Plant Ecology 160: 91–112, 2002.© 2002 Kluwer Academic Publishers. Printed in the Netherlands.

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Landscape variation of liana communities in a Neotropical rain forest

Guillermo Ibarra-Manrıquez & Miguel Martınez-Ramos1

Departamento de Ecologıa de los Recursos Naturales, Instituto de Ecologıa, Universidad Nacional Autonomade Mexico, Antigua carretera a Patzcuaro # 8701, Col. San Jose de la Huerta, Codigo Postal 58190, Morelia,Michoacan, Mexico; 1Author for correspondence (E-mail: mmartine@ate.oikos.unam.mx)

Received 17 August 1999; accepted in revised form 1 February 2001

Key words: Chiapas, Community ecology, Landscape, Lianas, Mexico, Montes Azules, Species diversity, Tropicalrainforest

Abstract

We studied local and landscape variation of liana communities across habitats differing in soil and topography inthe Lacandon tropical rain forest, southeast Mexico. All liana stems ≥1 cm diameter breast height (DBH) weresampled within each one of eight 0.5 ha plots. Two plots were sampled in each of the following habitats: alluvial-terrace, flood plain, low-hill, and karst-range. In the whole sampled area, we recorded 2092 liana stems ha−1

representing a total basal area of 1.95 m2 ha−1 and 90 species within 34 families. Lianas showed a strong clumpedspatial pattern and a high taxonomic diversity at the scale of 50 m2. On average (± s.e.), we found 10.4 ± 0.6stems, 4.4 ± 0.2 species and 3.4 ± 0.2 families per 50-m2 quadrat. Bignonaceae (19 species), Malpighiaceae (9),and Fabaceae (8) comprised about 40% of total number of recorded species, and almost 50% of the total lianabiomass, as expressed by an importance value index that combines species relative abundance, spatial frequencyand basal area. Nineteen families (56%) were represented by just one species and Cydista (Bignoniaceae) andMachaerium (Fabaceae) were the most diverse genera with four species each. In the landscape, lianas showed ageometric diversity-dominance relationship with only three species (Combretum argenteum, Hiraea fagifolia andMachaerium floribundum) accounting for more than 50% of total biomass. More than 30% of the species were rare(<15 stems ha−1) and showed low spatial frequency (recorded in just one of the eight plots). Liana communitiesdiffered in structure and composition among sites and habitats. Among sites, lianas exhibited four-fold variationboth in stem density and basal area and two-fold variation in species richness. Liana density was significantlyand positively correlated with treefall disturbance. Ordination analysis indicated a strong habitat differentiation oflianas at the family and species levels. Most species with non-random distribution among habitats (69% from 25species) were significantly most abundant in low-hill or flood plain sites, and some (12%) were preferentially foundat the karst-range sites. The karst-range habitat was well differentiated from the others in species composition andstructure, and shared only 50% of common species with other habitats.

Soil water availability, treefall dynamics, as well as tree host identity and abundance may play an importantrole in the organisation of the liana communities at the Lacandon forest.

Nomenclature: Ibarra-Manríquez & Sinaca (1995) and Martínez et al. (1994).

Introduction

Tropical rain forests are one of the most species di-verse plant communities (Gentry & Dodson 1987a).This assertion has been sustained for many years bystudies focused on the tree component of the forest

(e.g., Richards 1996). Recently, the exploration of me-chanically dependent plants, such as orchids, vines,and lianas has pinpointed the contribution of theseelements to species diversity, structural complexity,and function of tropical rain forests (Gentry 1982,1988, 1992; Gentry & Dodson 1987a, b; Putz 1984,

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1995; Clark & Clark 1990; Hegarty & Caballé 1991;Campbell & Newbery 1993; Makana et al. 1998).

In neotropical rain forests, there are around 9216liana species, representing 97 families of vascularplants (Gentry 1991a). At a local scale, lianas com-prise between 12 and 24% of the total number ofwoody species (Gentry & Dodson 1987a, b; Ibarra-Manríquez & Sinaca 1995). In addition, lianas arestructurally important in these forests. In moist andwet tropical forests, about 18–22% of understoreyerect plants are juvenile lianas (Gentry 1982) and, onaverage, lianas comprise about 24% of total stems withDBH ≥2.5 cm (Gentry 1991a). Functionally, the lianacommunity exhibits a diverse array of pollination, dis-persal, and phenological systems, and provides severalresources to the animal community (Emmons & Gen-try 1983; Gentry 1982, 1983, 1985, 1991b; Putz &Windsor 1987; Hegarty 1990; Ibarra-Manríquez etal. 1991; Opler et al. 1991). Lianas influence for-est regeneration dynamics; they produce weight loadsthat favour the occurrence of treefall gaps, and lianagrowth may inhibit tree regeneration in gaps and forestedges (Appanah & Putz 1984; Putz 1984, 1985; Putzet al. 1984; Clark & Clark 1990).

An increasing number of studies have documentedthe structure and composition of liana communities atthe scale of a few dozen square meters (e.g., Gentry1988; Putz & Mooney 1991). Some attempts havebeen made to document geographical relations be-tween attributes of the liana communities and macro-environmental variables such as annual rainfall, cli-mate seasonality, average temperature, and soil type(Clinebell et al. 1995). At present, however, fewstudies (Holdridge et al. 1971; Putz & Chai 1987;Molina-Freaner & Tinoco 1997) have explored howliana communities vary at a landscape scale whereclimate is virtually the same, but factors such assoil, topography, and arboreal vegetation are spatiallyheterogeneous. This type of analysis is necessary be-cause the abundance and size of trellis and tree lianahosts, frequency and magnitude of forest disturbances,and soil-water availability are thought to affect localabundance and distribution of lianas (e.g., Putz 1984;Hegarty & Caballé 1991; Molina-Freaner & Tinoco1997).

The present study was undertaken to explore struc-tural and species composition trends of liana commu-nities within and among contrasting soil-topographichabitats at the Lacandon forest in southeast Mexico.These habitats represent major environmental discon-tinuities within the Montes Azules Biosphere Reserve,

and sustain forests that vary in floristic compositionand structure (Siebe et al. 1996). In addition to pro-viding a detailed quantitative analysis of the structureand composition of the liana communities in the re-gion, at a scale of about 100 km2, we addressed thefollowing questions: what is the variation of the lianacommunities in the landscape in terms of abundance,spatial distribution, and species diversity? Are lianaspecies segregated among habitats; if so, what fac-tors are likely to promote such a differentiation? Howcomparable are the liana communities present at theLacandon forest with that of other tropical rainforests?

Study site

This study was conducted at the Chajul Tropical Bi-ological Station, located to the south of the MontesAzules Biosphere Reserve (16◦04′ N; 90◦45′ W),within the Lacandon region, in southeast Mexico. Thispreserve covers an area of 331 200 ha, and an altituderange of 80 to 1750 m.a.s.l. At Chajul, average annualrainfall is about 3000 mm. Mean annual temperatureis about 22 ◦C. There is a dry season from Februaryto April (less than 100 mm per month) which accountsless than 10% total annual rainfall. In this area a mo-saic of vegetation types is present including: lowlandand mountain rain forests, savannah-like vegetation,elfin forest, and pine forest (Gómez-Pompa & Dirzo1995). In the preserve, there are around 3400 speciesof vascular plants (Martínez et al. 1994) of which 573are trees.

Major landscape units

In the Chajul region there exist at least four differ-ent geo-morphological units (hereafter referred to ashabitats) that were defined using soil and topographiccriteria (Table 1). (i) Alluvial-terraces (altitude: 105–120 m.a.s.l.) are flat, fertile soil sites along marginsof the Lacantún-river. (ii) Flood plains (altitude: 105–115 m.a.s.l.) are old meandric areas originated fromthe Lacantun-river and with hydromorphic soil char-acteristics; these areas remain flooded at least threemonths every year. (iii) Low-hills (altitude: 115–300m.a.s.l.) are topographically irregular areas with smallhills and valleys with sandy or limestone soils of lowpH (< 5.5). (iv). Karst-range sites are topographicallyirregular mountain chain areas (300–700 m.a.s.l), lo-cally known as ‘Cordon Chaquistero’, where the soilis basically composed of a thin layer of organic matter,

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Table 1. Characteristics of the four study habitats at the Lacandon rain forest in southeast Mexico. Where available, minimum and maximumvalues are shown. (a) Abiotic aspects based on soil and topography surveys in three to five 0.5-ha plots per habitat. Average availablephosphorous (P, mg kg−1) and nitrogen (N, mg kg−1) are provided as soil nutrients; these values were estimated with samples taken fromsoil profiles of indicated depth∗ (modified after Siebe et al. 1996). (b) Tree community attributes based on censuses of trees DBH ≥ 10.0 cmin three to five 0.5 ha plots in each habitat (Martınez-Ramos et al., unpubl. data). Forest canopy height is expressed as the among plots averagemaximum canopy height (± s.d.). Treefall disturbance is the percentage of forest canopy area in gaps (points where canopy height was lessthan 2 m).

(a) Soil Topography

(Slope)

Habitat Category Depth∗ pH Nutrients Drainage

(FAO, 1988) (cm) P N

Alluvial terrace Haplic Luvisol 65–100 5.6–6.7 0.36–0.95 23.8–35.0 Moderate Flat (< 10◦)

Flood plain Eutric Planosol 45 4.9–6.0 0.22 12.2 Deficient Flat (< 10◦)

Low-hill Humic Acrisol 55–65 3.9–5.4 < 0.1 13.2–27.3 Moderate Moderate-steep (15◦–30◦)

Karst-range Rendzic Leptosol 12–20 7.0 0.23 57.9 High Very steep (30◦–40◦

(b) Tree community characteristics

Canopy Tree density Basal area Tree species % Area in gaps

hight (m) (ind ha−1) (m2 ha−1 richness

(in 0.5 ha)

Alluvial terrace 40 ± 3 318–376 22.6–37.6 43–58 0.4–4.3

Flood plain 40 ± 12 202–252 19.6–29.4 35–54 2.8–9.4

Low-hill 35 ± 1 344–524 16.6–29.8 50–81 2.3–3.9

Karst-range 35 ± 4 426–578 21.6–27.0 70–74 1.2–1.5

with masses of limestone rocks exposes over a karsttopography. Alluvial terraces have the most nutrientrich soils and low-hills have the poorest ones (Table 1).

A preliminary study has documented the varia-tion in the tree communities between these habitats(Siebe et al. 1996). Table 1 shows a summary of themain tree community attributes in the study habitats. Itshould be noted that karst-range and low-hill habitatssustain higher tree density and species richness whilethe alluvial-terrace habitat have the highest standingbiomass (estimated from tree community basal area).Forest canopy disturbance, as measured by the per-centage of forest area in gaps (localities with forestcanopy height shorter than 2 m), is lowest in karst-range habitat and highest in the flood plain habitat(Table 1).

Methods

The liana study system

To enable comparison with other works (Gentry 1982,1988, 1991a), in this study we included both lianasand those woody hemi-epiphytes that are liana-like.Lianas are woody vines that become established onthe forest floor and grow upward, toward the forestcanopy. Woody-liana-like hemi-epiphytes are climb-ing plants that germinate and establish themselves ontrees and lianas, and their physiognomy and growthbehaviour are similar to that of true lianas. As lianas,woody hemi-epiphytes may spread on more than onetree by producing a net of slender stems, some ofwhich may root in the soil and grow upwards again(Gentry 1988, 1991a). Hemi-epiphyte strangler trees(e.g., several species of Ficus) and epiphyte trees (e.g.,Clussia spp.), which are not liana-like, were not in-cluded. Hereafter we will refer to both true lianas andwoody hemi-epiphytes that are liana-like as ‘lianas’.

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Liana surveys

We conducted a census of lianas in each of the fourhabitats described above. Two different sites locatedat least 2 km apart represented each habitat. In eachsite, we established a permanent 0.5 ha (20 × 250-m)plot that ensured a good representation of the forest re-generative mosaic, including gap, building and maturephases (sensu Whitmore 1978). The plot was gridedwith aluminium stakes (0.75 m height) in quadrats of5 × 10 m. For each plot we randomly selected 30quadrats. All liana stems located within the quadratsand with a perimeter at breast height (PBH, 1.3 mabove ground) larger or equal to 3.1 cm (or 1 cm DBH,assuming a circular cross-section stem area), wereidentified to species and measured for PBH. We usedthe perimeter rather than diameter to avoid errors as-sociated with the irregular shapes of most liana stems.Later, PBH measures were converted to DBH valuesassuming a circular cross-section stem area (i.e., DBH= PBH/π).

We identified separate individual lianas whenstems were clearly rooted; otherwise, we lookedfor possible underground stem connections. All non-rooted stems with a measurable PBH were assumedto belong to rooted lianas within the quadrats. Lianaswere identified to species in the field using repro-ductive (flowers or fruits) and/or vegetative (leaves,trunks) characteristics and when necessary sterile ma-terial was collected for later identification at theMEXU Herbarium, where voucher specimens col-lected previously by others were deposited. Speciesnomenclature in this study follows that of Ibarra-Manríquez & Sinaca (1995) and Martínez et al.(1994).

Data analyses

Liana assemblage characterisation at the landscapelevelTo describe average floristic and structural attributesof lianas at the landscape level, we combined dataobtained from all plots. We used the frequency ofspecies per family to characterise the floristic compo-sition. To describe liana size structure, we obtainedthe frequency of stems in log10 DBH classes. Bydividing the total number of stems by the total num-ber of rooted lianas, we roughly estimated the aver-age number of stems with DBH >1 cm per rootedliana. We also obtained the abundance (total numberof individual lianas and stems), basal area (cross-sectional area of stems at 1.3 m above ground), and

frequency (number of quadrats or plots in which aspecies was recorded) per species, family, and forthe whole liana assemblage. Basal area per stem wasobtained as π(DBH/2)2, assuming stem cross-sectionarea as a circle. To quantify the structural importanceof families and species, we used an Importance ValueIndex (IVi). Following Müller-Dumbois & Ellenberg(1974), this index was calculated as IVi = Ai + Fi +BAi , where Ai , Fi and BAi are, respectively, the per-centages of abundance, quadrat frequency, and basalarea of the ith family or species.

The coefficient of dispersion (CD = variance/mean) of the number of stems per 5 × 10 m quadratwas used to assess local spatial pattern of the lianastem community. A CD value statistically equal to1 indicates a random pattern, CD > 1 indicates anaggregated pattern, and CD < 1 an uniform one.We used a t-test to assess significant deviation fromCD = 1.0 (Pielou 1969).

Following Magurran (1988), we used the totalnumber of species recorded in the eight plots (speciesrichness), as well as Shannon (H ′) and Simpson (D)

diversity indices to quantify species diversity. Shannonindex emphasises the contribution of rare species tospecies diversity, while Simpson index emphasise thecontribution of the most abundant (dominant) species.We also obtained the evenness index J associatedwith H ′ and the evenness index E associated with D

(Magurran 1988). In all these indices we used IVi asa criterion of species biomass. Additionally, followingGotelli & Graves (1996), we used species IVi to con-struct a dominance-diversity curve for the whole lianaassemblage.

Variation in abundance among species was ex-pressed as the frequency of species in log2 abundancecategories. The spatial distribution of species in thelandscape was defined by the frequency of quadratsand plots in which each species was recorded. Finally,to explore abundance-distribution relationships and toassess the relative contribution of abundance, basalarea, and frequency to species importance value, weexplored pair-wise linear relationships among thesestructural variables.

Community variation among sites and habitatsWe quantified the same parameters described abovefor each site and habitat. These values were calculatedat the scale of the total area sampled per site (or habi-tat), and at the scale of the 5×10-m quadrats. To assessstructural and composition changes among habitats,we performed ordination by correspondence analysis

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(CA). In this analysis, we assumed that taxa (familiesor species) have optimum performance (e.g., abun-dance) in one particular habitat (Jongman et al. 1987).We constructed matrixes with h (habitats) columns,and t (families or species) rows. The number of rowscorresponded to the total number of taxa recorded inthe eight study plots. Matrix cells corresponded tothe taxa importance value in each habitat. We usedthe program Orden V.2.0 (Ezcurra 1992) to performthe CAs. Additionally, the Sørensen index (Magur-ran 1988) was used to quantify the floristic similarityamong habitats. Simple correlation analysis was usedto explore relationships between inter-site variationin liana abundance, basal area and species diversitywith canopy disturbance (as measured by natural log-arithm of percentage of forest area in gaps) and tree(DBH ≥ 10 cm) density (data from Table 1).

To assess statistical differences in abundance, basalarea, and floristic (species and family) diversity amongsites and habitats, we used Analyses of Deviance (AN-DEVA) procedures (Crawley 1993). We performedone-way ANDEVAs using the two plot values perhabitat as habitat replicates. We performed a sec-ond series of ANDEVAs to test the effects of habitatand site on structural variables by using data fromindividual quadrats. For count variables, we used aPoisson error and a log-link function and, when re-quired, over-dispersion problems were corrected byrescaling dependent variables (Crawley 1993). Theeffect of site and habitat type was assessed by theamount of explained deviance from total deviance,which approximates to χ2 values (Crawley 1993). Forcontinuous variables, we used a normal error and alinear link function, in which case ANDEVA becomesequivalent to one-way Analysis of Variance. To avoidviolation of ANOVA normality requirements, we usedlogarithmic transformation (Sokal and Rohlf 1995) forbasal area and species diversity values (both H ′ andD). Also, we used analyses of deviance to test associa-tion analyses between species abundance and habitats,and to assess correlations between liana species diver-sity or abundance and canopy disturbance (assessed aspercentage of forest area in gaps) and the abundanceof trees with DBH > 10 cm. All statistical tests wererun using the statistical package GLIM 3.77 (1985).

Figure 1. Size distribution (DBH classes and their relative contribu-tion to total basal area) of lianas at the Lacandon forest in southeastMexico. Along the X′s axis, the upper limit of each category isshowed.

Results

Liana community composition and structure at thelandscape level

In the eight study plots (total area = 1.2 ha), werecorded a total of 1252 rooted lianas (1043 lianasha−1), and 2510 liana stems (2092 stems ha−1).These stems represented a total basal area of 2.34 m2

(1.95 m2 ha−1). Lianas were widely distributed in thestudy area as we recorded liana stems in 93.3% oftotal sampled quadrats (N = 240). On average (±s.e.), an individual rooted liana had 2.0 ± 0.1 stemsat the forest floor level. Eighty one percent of to-tal stems had between 1 and 4 cm-DBH and only1.6% had a DBH > 9.9-cm DBH . These big lianas,however, represented 16% of the total basal area (Fig-ure 1). The biggest stem measured 21.0-cm-DBH

(Souroubea loczyi, Marcgraviaceae) and on averagestems measured 2.7 ± 0.1 cm in DBH .

At the scale of the 5 × 10 m quadrats, we obtainedan average stem density of 10.4 ± 0.6. This mean den-sity showed a great variance: 50% of total quadratsincluded less than 15% of total stems while fifteenpercent of quadrats contained more than 50% of totalstems. Maximum liana stem density per quadrat was51. The coefficient of dispersion (CD = 8.9) indi-cated that lianas had a strongly clumped spatial pattern(t = 13.5, DF = 238, P < 0.0001).

A total of 90 liana species, representing 34 an-giosperm families, were recorded. Appendix I showsthe list of taxa recorded in each one of the eight study

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Table 2. Structural contribution of the ten most important families with liana speciesin the Lacandon forest, southeast, Mexico. Percentage values (in parenthesis) wereobtained by pooling all plots (1.2 ha).

Familiy Species Stem Basal Importance

richness abundance area (m2) value

1. Bignoniaceae 18 (20) 628 (25) 60.1 (26) 75.9 (25)

2. Fabaceae 8 (9) 301 (12) 37.8 (16) 40.7 (14)

3. Combretaceae 2 (2) 251 (10) 34.0 (15) 33.2 (11)

4. Sapindaceae 6 (7) 326 (13) 21.2 (9) 32.8 (11)

5. Malpighiaceae 9 (10) 226 (9) 15.1 (7) 25.1 (8)

6. Compositae 5 (6) 176 (7) 15.7 (7) 19.9 (7)

7. Apocynaceae 4 (4) 108 (4) 7.7 (3) 12.6 (4)

8. Hippocrateaceae 1 (1) 93 (4) 9.8 (4) 10.9 (4)

9. Marcgraviaceae∗ 2 (2) 75 (3) 8.2 (4) 7.3 (2)

10. Dilleniaceae 2 (2) 50 (2) 3.9 (2) 5.9 (2)

Subtotal 57 (63) 2234 (89) 273.9 (93) 264.1 (87)

Other families 24 (37) 276 (11) 39.5 (7) 35.9 (13)

Total 90 (100) 2510 (100) 234.4 (100) 300.0 (100)

∗Marcgraviaceae was represented by one liana and one woody hemi-epiphytespecies.

Figure 2. Species-dominance relationship for the study liana communities at the Lacandon forest, southeast Mexico. The latin names of the tenmost important species and parameter values of the adjusted regression model are given.

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Figure 3. Structural components of the liana community at theLacandon forest, southeast Mexico. (a) Frequency distribution ofspecies in log2 categories of stem density, (b) frequency distribu-tion of species categorised by the number of plots in which theyappeared.

plots. On average, a 5 × 10 m quadrat had 4.4 ± 0.2species and 3.4 ± 0.2 families. There was strong tax-onomic dominance as only five families contributedabout 50% of total number of recorded species (Ta-ble 2), and nineteen families were represented by onlyone species (Appendix I). The most diverse generawere Cydista and Machaerium, each one with fourspecies, whereas Arrabidaea, Paullinia, and Stigma-phylum had three species each (Appendix I).

Just one Bignoniaceae (Schlegelia parviflora),two Marcgraviaceae (Marcgravia mexicana andSouroubea loczyi) species and Drymonia serrulata(Gesneriaceae) were liana-like hemi-epiphytes and therest were true lianas. These hemi-epiphyte species ac-counted for less than 5% of total abundance, basal

area, and importance value, and each species wasrecorded in less than 5% of total sampled quadrats.

The most species rich families were also the moststructurally important, as only five families repre-sented 69% of total abundance, 73% of total basalarea, and 69% of total community importance value(Table 2). Bignoniaceae and Fabaceae were the moststructurally important families. Combretaceae was thethird in importance but was represented by only twospecies.

The Shannon index of diversity for the whole lianacommunity was 1.65, with relatively high evennessindex (J = 0.85). However, Simpson diversity in-dex (D = 32.5) indicates that only a third of totalspecies (E = 0.36) were the most structurally im-portant. Among dominant species, eleven species ac-counted for 50% of total community importance value.The observed community dominance-diversity curvefitted tightly to a geometric model; Combretum argen-teum, Hiraea fagifolia, and Machaerium floribundumwere the species with the highest importance values(Figure 2).

Most of the recorded species were rare, but severalwere very abundant (Figure 3a). About 30% of totalspecies had less than seven stems in the eight studyplots (i.e., less than 5.8 stems ha−1), and about 15%of total species had more than 127 stems (i.e., morethan 106 stems ha−1). Most species were spatiallyrestricted. About 35% of total species were found injust one of the eight studied plots (Figure 3b). OnlyCombretum laxum and Hiraea fagifolia were recordedin all plots (Appendix I). Combretum argenteum, Cy-dista potosina, Forsteronia viridescens, Machaeriumkegelii, Paragonia pyramidata, Paullinia venosa, andSerjania mexicana were also widely distributed, asthey were recorded in seven of the eight study plots.

Species abundance, basal area, and quadrat fre-quency showed a positive association across the wholesampled area. Species abundance and spatial distri-bution were closely related (Figure 4a). No speciescovered the entire sample area, and the most abun-dant species were recorded in less than 30% of totalsampled quadrats (Figure 4a). The relationships be-tween species basal area and species abundance ordistribution were more variable (Figures 4b and 4c).Species with similar levels of abundance and distrib-ution differed strongly in basal area (Figures 4b and4c), indicating that the average individual stem basalarea varied greatly among species. For example, theabundant and widely distributed species, Combretumargenteum, Machaerium floribundum, C. laxum, and

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Figure 4. Relationships between variables related to species importance of the liana community at the Lacandon forest, Southeast Mexico:(a) Abundances spatial distribution; (b) abundance vs basal area, (c) distribution vs basal area. Distribution values are expressed as thepercentage of quadrats in which a species was recorded. In each case, parameter values of the adjusted linear regression and their statisticalsignificance are indicated. The numbers inside the graphs indicate the ten species with the highest importance value as indicated in Figure 2.

M. lunatum, had basal area stems between 40 to 60%higher than the community average (9.4 cm2 stem−1;Figure 4). On the contrary, Hiraea fagifolia, Sti-zolobium riparium, and Fornsteronia viridescens hadbasal area stems 20 to 50% lower than the communityaverage.

Liana community variation among sites and habitats

At the family level, CA analysis segregated flood plainand karst-range from low-hill and alluvial-terracehabitats (Figure 5). Among the ten most importantfamilies, Marcgraviaceae, Hippocrataceae and, to alesser degree, Sapindaceae and Vitaceae, were associ-ated with the karst-range habitat, while Bignonaceae,Fabaceae, Combretaceae, Malpighiaceae, Composi-tae, and Apocynaceae were associated with the low-

land habitats (Figure 5). Some families with mediumimportance value were also associated with particu-lar habitats: Acanthaceae with low-hill and alluvial-terrace, and Malvaceae with the flood plain habitat.

At the species level, CA analysis again segre-gated alluvial-terrace and low-hill from karst-rangeand flooded plain habitats (Figure 6). The two firstaxes explained 77% of total variation. Several speciesthat were found exclusively in one habitat had verylow importance values. Although dominant specieswere mostly found in lowland habitats (Figure 6),some were clearly associated with one or two particu-lar habitats: Hippocratea celastroides in karst-range,Piptocarpha chontalensis in low-hill and alluvial-terrace, and Stizophyllum riparium in the flood plainsites.

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Table 3. Variation of liana community attributes among sites and habitats at the Lacandon forest, southeast Mexico. AT = alluvial-terrace, FP= flood plain, KR = karst-range, LH = low-hill sites. Values for habitats are in italics. Abundance is the total number of rooted lianas (orstems indicated in parenthesis) per site (0.15 ha) or habitat (0.30 ha). Frequency is the percentage of total sampled quadrats occupied by lianas.Maximum stem DBH recorded in each site is indicated in parenthesis (minimum DBH in all cases was 1.0 cm). Sites and habitats not sharingsame letter are statistically different (P < 0.025).

Attribute Sites

AT-1 AT-2 FP-1 FP-2 KR-1 KR-2 LH-1 LH-2

Abundance 240 (387) 138 (210) 232 (522) 74 (151) 73 (159) 98 (261) 262 (548) 135 (274)

Lianas (stems) 378c (597)b 304b (673)b 181a (422)a 397c (820)c

Stems liana−1 1.6 ± 0.1b 1.5 ± 0.1b 2.3 ± 0.1a 2.0 ± 0.3a 2.2 ± 0.2a 2.7 ± 0.3a 2.1 ± 0.1a 2.0 ± 0.2a

(mean ± s.e) 1.6 ± 0.1a 2.2 ± 0.1b 2.5 ± 0.2b 2.1 ± 0.1b

Frequency (%) 96.7 96.7 93.3 90.0 93.3 93.3 96.7 86.7

96.7 91.7 93.3 91.7

Basal area (m2) 0.35 0.24 0.36 0.18 0.17 0.21 0.51 0.32

0.59a 0.54a 0.38a 0.83a

Stem DBH 2.6 ± 0.1 2.7 ± 0.1 2.3 ± 0.1 2.9 ± 0.1 2.6 ± 0.1 2.7 ± 0.1 2.7 ± 0.1 2.9 ± 0.1

mean ± s.e. (14.5) (16.0) (11.6) (13.0) (21.0) (9.5) (10.5) (12.5)

(max) 2.6 ± 0.1a 2.5 ± 0.1a 2.5 ± 0.1a 2.8 ± 0.1b

Broadness of distribution among habitats did notnecessarily reflect the lack of habitat preference ofthe species. Considering only species with more than20 stems in 1.2 ha, we found 25 of them with apreference for a particular habitat, with respect to arandom (uniform) distribution among habitats. Four(16.0%) of these species were significantly more abun-dant in the alluvial-terrace, eight (32.0%) in the floodplain, three (12%) in the karst-range, and ten (40%)in the low-hill (Figure 7). Another four species wereequally abundant among habitats except in the karst-range sites where they showed a significantly lowerabundance (Acacia hayesii, Cydista potosina) or wereabsent (Tetracera volubilis, Mikania leiostachya). Fi-nally, Abuta panamensis exhibited equal abundance inthe karst-range and low-hill habitats but was virtuallyabsent from alluvial-terrace and flood plain sites. OnlyMachaerium kegelii (n = 21) had a statistically equalabundance in all habitats (χ2 = 6.2, DF = 3, N.S.).

Classification analysis, using Sørensen similarityindex, showed a very high β-species diversity. Thekarst-range was the most floristically dissimilar habi-tat, sharing less than 50% of common species with theother habitats. Alluvial-terrace and low-hill were themost floristically similar habitats, sharing about 75%of common species.

Liana abundance, basal area, and species richnessvaried two to four-fold among sites (Tables 3, 4 and5). The frequency with which lianas were recorded in

Figure 5. Correspondence Analysis by habitat for the liana commu-nity represented by 36 families recorded in 1.2 ha at the Lacandonforest, southeast Mexico. The black dots indicate the habitat posi-tion: AL = alluvial sites, LH = low hill sites, FP = flood plainsites, KR = karst-range sites. The numbers indicate position ofthe ten most important families as listed in Table 2, except 19(Acanthaceae), and 20 (Malvaceae).

the sampled quadrats was consistently high in all sites(>86%). Inter-site variation in liana abundance wasthe only community liana parameter significantly cor-

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Table 4. Structural liana community variation among sites and habitats at the scale of 50 m2 (10 × 5 m quadrats) at the Lacandon forest,southeast Mexico. Values for habitats are in italics. Sites or habitats not sharing same letter are statistically different (P < 0.025). Dispersionindex values with one ∗ are significantly different from randomness at P < 0.001, those with ∗∗ at P < 0.0001.

Attribute Site

AT-1 AT-2 FP-1 FP-2 KR-1 KR-2 LH-1 LH-2

Stems quadrat−1 12.9 ± 1.8c 7.2 ± 1.3b 17.4 ± 2.2c 5.0 ± 0.8a 5.3 ± 0.8ab 8.7 ± 1.5b 18.3 ± 1.8c 9.1 ± 1.6b

(mean, ± s.e.) 10.0 ± 1.2b 10.9 ± 1.4bc 7.0 ± 0.9a 13.0 ± 1.3c

Dispersion 8.0∗∗ 6.9∗∗ 8.5∗∗ 4.0∗∗ 3.4∗∗ 7.8∗∗ 5.1∗∗ 8.0∗∗index (s2 mean−1) 8.3∗∗ 10.9∗∗ 6.5∗∗ 7.5∗∗

Number of 4.5 ± 0.4b 3.0 ± 0.4a 5.1 ± 0.5b 1.8 ± 0.2a 2.0 ± 0.2a 2.3 ± 0.3a 5.2 ± 0.4b 3.0 ± 0.4a

families quadrat−1 3.8 ± 0.3bc 3.4 ± 0.3b 2.2 ± 0.2a 4.2 ± 0.4c

(mean ± s.e)

Number of 5.8 ± 0.6b 3.8 ± 0.6a 6.2 ± 0.7b 2.0 ± 0.3a 2.2 ± 0.3a 2.7 ± 0.4a 6.7 ± 0.5b 4.0 ± 0.6a

species quadrat−1 4.8 ± 0.4bc 4.1 ± 0.5b 3.3 ± 0.3a 5.4 ± 0.6c

(mean ± e.e)

Table 5. Components of liana species diversity and their spatial variation at the Lacandon forest, southeast Mexico. Valuesbased on samples taken in 0.15 ha per site. H ′ = Shannon diversity index, J = evenness index for H ′, D = Simpsondiversity index, E = evenness index for D. Values in italics correspond to averages (± s.e.) per habitat and those inparenthesis were obtained mixing the two plots per habitat. Habitats not sharing same letter are statistically different(P < 0.05).

Attribute Sites

AT-1 AT-2 FP-1 FP-2 KR-1 KR-2 LH-1 LH-2

Species richness 45 41 41 23 24 28 47 42

43.0 ± 2.0 (58)b 32.0 ± 9.0 = (48)ab 26.0 ± 2.0 (40)a 44.5 ± 2.5 = (56)b

Diversity (H ′) 1.48 1.47 1.39 1.16 1.23 1.09 1.43 1.36

1.48 ± 0.00 = (1.56)a 1.28 ± 0.11 (1.45)a 1.16 ± 0.07 (1.31)a 1.40 ± 0.03 (1.47)a

Equitability (J ) 0.89 0.90 0.86 0.85 0.85 0.79 0.88 0.87

(0.89) (0.86) (0.82) (0.84)

Diversity (D) 23.7 21.8 17.7 9.0 11.5 7.6 20.5 17.2

22.8 ± 1.0 (27.6)a 13.4 ± 4.4 (19.3)a 9.6 ± 2.0 (13.0)a 18.9 ± 1.7 (18.6)a

Equitability (E) 0.53 0.53 0.43 0.39 0.41 0.32 0.49 0.46

(0.48) (0.40) (0.33) (0.33)

related with canopy disturbance (r = 0.73, DF = 6,P < 0.05). The variation among sites in abundance,basal area, and species richness were not correlatedwith inter-site variation in tree density (P > 0.10).The number of stems per liana differed significantlyamong habitats (χ2 = 33.7, DF = 3, P < 0.001);the number of stems with DBH ≥ 1 cm per rootedliana in the alluvial-terrace was about half as much asin the other habitats (Table 3). Average liana size, asmeasured by stem DBH, was significantly (F3, 1247 =

3.08, P < 0.05) larger in the low-hill than in the otherhabitats. The biggest liana, however, was found in oneof the karst-sierra sites (Table 3).

Liana abundance and basal area tended to be highin the low-hills and low in the karst-range sites inthe 20 × 250 m plots. ANDEVA, however, did notdetect significant differences (P > 0.10) for thesevariables. Considering the 5 × 10 m quadrats, stemabundance differed among sites (χ2 = 81.3, DF = 7,P < 0.01) and habitats (χ2 = 16.6, DF = 3,

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Figure 6. Correspondence analysis of the liana community ordering90 species among habitats at the Lacandon forest, southeast Mexico.The black dots indicate habitat position: AL = alluvial sites, LH =low hill sites, Fl = flooded sites, Ka = karstic sites. The numbersindicate position of the ten most important species as in Figure 2.

P < 0.01; Table 4). The karst-range had a signifi-cantly lower abundance of liana stems than the otherhabitats, and the low-hill showed the highest abun-dance. In all sites and habitats liana stems were strongclumped, especially in the flood plain sites (Table 4).

At the 0.5 ha plot scale, species richness (χ2 =10.1, DF = 3, P < 0.01) was significantly lowerin the karst-range than in the alluvial-terrace and low-hill, but was similar to that of the flood plain habitat(Table 4). Although species diversity (measured ei-ther with the Shannon or Simpson indices) showedsame trend, ANDEVA did not detect significant dif-ferences in species diversity among habitats (P >

0.10; Table 5). On the basis of the evenness indices,the alluvial-terrace showed the maximum diversity(Table 5).

The number of species (χ2 = 38.3, DF = 3,P < 0.01) or families (χ2 = 28.8, DF = 3, P <

0.001) per 50 m2 quadrat was significantly higher atthe alluvial-terrace and low-hill habitats and lower atthe karst-range. On average, we recorded an inter-sitevariation of 5 to 18 stems representing two to five fam-ilies, and two to seven species per quadrat (Table 4).Roughly, we found different taxa every two to threeliana stems. Maximum values for species and familyrichness per quadrat ranged among sites from six tofifteen and from four to nine, respectively.

Discussion

Liana communities at Chajul compared to othertropical rain forests

Taxonomic attributesWe found that Bignoniaceae, Fabaceae (Legumi-nosae), Malpighiaceae, and Sapindaceae were themost species rich families; this is also the case formost neotropical rainforests studied to date (Gentry1990, 1991a; Dewalt et al. 2000). In addition, themost speciose genera in our study (e.g., Machaeriumand Paullinia) are among the most speciose in otherneotropical rain forests (Gentry 1991a). Our findingthat only ten families comprised 69% of liana speciesis very close to Gentry’s (1991a) conclusion that about64% of the estimated 9216 climbing species in theNeotropics belong to only twelve families. Similar ob-servations were made at Los Tuxtlas, Mexico, where69% of total number of species of climbing plantsbelongs to eleven families (Ibarra-Manríquez et al.1997). Perhaps, this pattern is related to the ecologicaladvantages conferred by specialised climbing struc-tures and mechanisms evolved in certain families, as isthe case of tendrils (e.g., Bignoniaceae) and sensitiveyoung branch lets (e.g., Malpighiaceae; Gentry 1991a;Hegarty 1990; Dewalt et al. 2000).

The families with high species richness were alsothe most structurally important. Bignoniaceae andFabaceae were the dominant families (Table 2), as hasbeen reported for most neotropical rain forests (Gen-try 1991a). The dominance of a few speciose familieshas been also noted in tree communities of tropicalrain and deciduous forests (Lott et al. 1987; Balée &Campbell 1990; Valencia et al. 1994). An exception tothis trend was the Combretaceae, third in communityimportance value in our study, which was representedby only two species (Table 2).

Structural attributesCompared with the density values for lianas (DBH >

1 cm) at other locations around the world (Gentry1991a), liana density at Chajul (116 stems 0.1 ha−1)was above the average value for the Neotropics (69–78 0.1 ha−1). It was similar to the maximum valuerecorded for the Neotropics in Jauneche, Ecuador, andto the values found in some rain forests in Africa (106–122 0.1 ha−1). The ratio between liana (DBH >

2.5 cm) density to tree (DBH > 10 cm) density,claimed by Gentry (1991a) to be around 1 in neotrop-ical rain forests, was 2.8 at Chajul. This high ratio

102

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103

may result from a relative low tree density at Chajul.However, we can estimate for Chajul (from Tables1 and 5) an average of 2.0 trees ≥ 10 cm DBHper 5 × 10 m quadrat, and an average of four lianastems per tree. This liana abundance per tree is higherthan that recorded at other rain forest localities (e.g.,Campbell & Newbery 1993).

The abundance of big lianas (DBH > 10 cm)may indicate the regenerative status of a tropical rainforest. As a general trend, as forest successional ageincreases the abundance and basal area of big lianasalso tend to increase (Schnitzler 1995, Dewalt et al.200). In mature neotropical forests, big lianas repre-sent between 1 and 2% of the total basal area of woodyplants with ≥ 10 cm DBH (Hegarty & Caballé 1991).These values are higher than that we found at Chajul.Considering that the community of trees and lianas≥ 10 cm DBH at Chajul has an average basal area of25.2 m2 ha−1 (Martínez-Ramos et al., unpubl. data),we calculate that big lianas represent only 0.7% of theliana and tree community basal area. This value wasseveral times lower than the relative abundance (4.1%)accounted by big lianas among tree and liana stemswith DBH ≥ 10 cm (416 stems ha−1; Martínez-Ramos et al., unpubl. data). Such a difference mayreflect the great vegetative growth capacity of lianas,which prolifically produce slender stems and branchesas they grow from host tree to another. Such a capacityis also illustrated by our finding that, on average, arooted liana has two stems detectable near the forestfloor level (Table 3). Future studies need to compareforest dynamics to determine whether the relativelylow frequency of big lianas at Chajul results from ahigher frequency of disturbance in this locality than inforests with higher basal area of big lianas.

Spatial pattern of the liana communityThe strongly clumped spatial pattern exhibited bythe lianas at Chajul resembles that described inSabah, East Malaysia (Campbell & Newbery 1993). Aclumped pattern has been also documented for lianasin other forests (e.g., Putz 1984; Putz & Chai 1987).Trellis and light have been proposed as factors thatpromote clumped liana distribution: once an individ-ual liana successfully climbs a tree, it becomes a trellisitself, allowing other lianas to climb. This process maybe more active near light gap edges where lianas growfaster (Campbell & Newbery 1993; Putz 1984). Aclumped pattern may also result when several lianastems are deposited on the forest floor as a conse-quence of a treefall. Also, new liana shoots may grow

from these stems, stimulated by the rich light envi-ronment of the gap (Putz 1985; Putz & Chai 1987;Hegarty & Caballé 1991).

The above observations may help to explain whywe found a significant correlation of liana abundanceand canopy disturbance. Appanah & Putz (1984) alsofound in Malaysia that climbers tend to be more abun-dant in places with more frequent natural treefalls. Inour study sites, liana aggregation was strongest in themost disturbed site, the flood plain site FP-1, whichhad the highest percentage of gap area, a high lianaabundance, and the minimum average liana DBH (anindicator of high recruitment; Tables 1, 3 and 4). It ispossible, however, that the abundant growth of lianasin gaps may lower canopy turnover rates by inhibitingtree regeneration. In addition to canopy disturbance,poor seed dispersal (i.e., limited spatial recruitment),prolific vegetative growth, and spatial pattern of hosttrees are factors that may be involved in the clumpedbehaviour of lianas.

Dominance-diversity relationshipThe geometric dominance-diversity curve fitted tothe studied liana communities contrasts with the log-normal and ‘broken-stick’ curve types, which is com-monly found for tropical rain forest tree communities(e.g., Bongers et al. 1988; Hubbell 1979). The geomet-ric curve presumably expresses a colonisation processwhere each species arrives at open habitats at ran-dom intervals pre-empting a constant proportion ofavailable resources (Gotelli & Graves 1996). Log-normal and broken-stick curves, on the other hand,suggest situations where species populations are neara numerical equilibrium in different environmentalpatches, presumably as a result of species competitiveinteractions (but see Hubbell 1979).

A geometric curve type has often been found forpioneer, early successional plant communities (e.g.,Whittaker 1972; Bazzaz 1975; May 1975). From thisperspective, the liana communities we studied arestructurally similar to assemblages of pioneer species.Although not all liana species are light demanding,several may need open spaces to recruit, grow and re-produce (Putz 1984; Hegarty & Caballé 1991; Dewaltet al. 2000). As with some pioneer and light demand-ing species (e.g., Brokaw 1987), different species oflianas may differ in their ability to disperse or surviveas seeds, seedling or saplings under shaded condi-tions and pre-empt forest gaps. However, in contrast topioneer trees, lianas may rely relatively more on veg-etative growth than on seed dispersal to colonise gaps.

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Also, a geometric curve may result from a species’differential use of gaps of different sizes, as gap fre-quency itself declines geometrically with increasedsize (Hubbell & Foster 1986a).

Abundance-distribution relationshipThe tight relationship we found between liana speciesabundance and distribution (Figure 4a) suggests thatwidespread species are locally more abundant thanspatially restricted ones. At least four hypotheses havebeen proposed to explain this general pattern (Gotelli& Graves 1996). First, this may result from a sam-pling artefact as species abundance may depend uponwhat part of the species distribution range is includedin the sampled area. This possibility apparently doesnot apply to our case as we widely spaced our samplesof liana communities across habitats and sites. Also,we detected that species tended to be restricted to par-ticular habitats (Table 7) where they have a higherdensity.

Second, the abundance-distribution relationshipmay be obtained purely by chance when a Poissonprocess defines species local density across the land-scape. Under this scenario, a null linear relation witha slope of −1 and an intercept of 0 is expected be-tween the natural logarithm of the species frequencyof absences (Ln f ) and species average local density(D; Gotelli & Graves 1996). Regressing Ln f (esti-mated as Ln of 1 − relative frequency of quadrats inwhich a species was recorded) on D (stems per 50-m2

quadrat) we obtained a slope ± s.e.) of −0.402±0.022(F = 723.5, DF = 89, r2 = 0.88, P < 0.0001).This slope value was significantly less steep than thatexpected by random. A slope value lower than −1.0indicates that abundant species tend to be spatially ag-gregated, as was the case for the lianas we studied atthe landscape and site levels (Table 5).

A third possibility is that species abundances anddistributions reflect niche breadth, and those factorsfavouring (or limiting) abundance also determine thewideness of species distributions (Brown 1984). Thismay imply that in our liana study system there weresome species with broad niches (generalist species),such as Combretum laxum and Hiraea fagifolia, whichwere recorded in all plots and were among the mostabundant and frequent species in all studied soil-topographic habitats. Rarity in this context may resultfrom the low availability of habitat of required forhabitat-specialist species.

As in trees, liana species niche breadth may bedetermined by dispersal capacity and the spatial fre-

quency of habitats where successful seed germinationand growth occurs. However, unlike trees, liana nichebreadth may also depend on the abundance and spatialfrequency of host-tree species where liana maturationtakes place. In the same study sites, it was found thatthe most abundant tree species showed a strong segre-gation among the habitats here studied; for example,Sapotaceae species (e.g., Manilkara sapota, Pouteriaspp.) were very abundant in the karst-range sites andalmost absent from the other habitats, while Legumetrees (e.g., Dialium guianense) that were abundantin low-hill sites were rare in the karst-range sites(Martínez-Ramos et al., unpubl. data). In this studywe found that some liana species were restricted to thekarst-range (e.g., Thinouia myriantha) and others tothe low-hill habitat (e.g., Zesmenia serrata; Figure 7).

Finally, the abundance-distribution relationshipmay result from species metapopulation dynamics.Hanski (1982) and Hanski & Gyllenberg (1993) pre-dicted that local population density and the fractionof an area occupied by a species depends on sto-chastic or deterministic variation in local extinctionand colonisation rates across the landscape. This isthe so-called ‘core-satellite hypothesis’. Most frequentspecies are those restricted to a small fraction ofavailable sites (‘satellite’, rare, prone to extinctionspecies), and those occurring in most sites (‘core’,abundant, demographically growing species). Localpopulations of satellite species may persist throughmigration (‘rescue effect’) from other sympatric hostpopulations (Hanski & Gyllenberg 1993). To test thisidea, assuming that species are ecologically simi-lar and have comparable metapopulation dynamics, abimodal distribution in the species frequency of oc-currence must be observed in the community (Gotelli& Graves 1996). This certainly was not the case atChajul. We found a single modal distribution skewedtowards less frequent species, for both plots (Fig-ure 3b) and quadrats (50% of species were presentin only 2.5% of total sampled quadrats). It has beentheoretically argued that when low colonisation rates,a small amount of variation in environmental patchsizes, and a small rescue effect operate on the speciesin a community, one should expect a single modal dis-tribution skewed towards a low occurrence frequency(Hanski & Gyllenberg 1993).

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Variation of liana community structure across thelandscape

Our four-fold range of liana abundance variationamong study habitats compares with that found byGentry (1991a) for a large set of neotropical forestlocalities. In a dipterocarp forest at Pahang, Malaysia,Appanah & Putz (1984) showed that liana (≥ 2 cmDBH) abundance changed as much as two-fold amonghectares. The same result was obtained in Sarawak,Malysia where liana density (DBH > 2 cm) wastwice as high in a valley as on a hilltop (Putz & Chai1987).

High liana density has been recorded in local-ities with a marked dry season where a transitionfrom moist to dry forest is present (Holdridge et al.1971, Gentry 1991a). At Chajul, a clear dry seasonoccurs from January to March, when precipitationaccounts for less than 10% of total annual rainfall.Also, at Chajul there is a clear distinction betweenevergreen tall forests (along river edges) and semi-deciduous medium sized forests (in karst-range andlow-hill sites). Among other things, such a vegetationchange is related to changes in soil drainage capacity(Table 1) and soil water availability that, in general,decrease as the distance to the Lacantún-river edgeincreases. Although we found maximum liana abun-dance in low-hills, some alluvial terrace and floodplain sites have also high liana density (Tables 3 and4), which resembles other seasonally inundated forest(Appanah & Putz 1984; Putz & Chai 1987; Gen-try 1991a), especially if the soil is not hydromorphic(Schnitzler 1995).

Maximum liana abundance in the low-hill habitatcould be associated with high host tree availability(Table 1). The fact that the inter-site variation inliana abundance was not significantly related to theabundance of trees with DBH > 10 cm weakensthis idea. However, the abundance of saplings andsmall trees, which can act as trellis for lianas, was30 to 60% higher in low-hills than in other habitats(Martínez-Ramos et al., unpubl. data). This high trel-lis abundance and relatively high canopy disturbancelevels (Table 1) may favour high abundance of lianasin the low-hill sites. Also, the availability of soil re-sources seems to be involved in the variation of lianaabundance among habitats. For example, lianas wereless abundant in the karst-range sites where soil wateravailability seems to be an important limiting factor(Table 1). The water conducting system of lianas iscomposed of large and wide vessels, which are very

sensitive to low water availability (Ewers et al. 1990;Gartner et al. 1990). After a severe drought, the xylemmay become disfunctional due to vessel embolism,detrimentally affecting individual liana fitness. In aseasonal dry forest at Chamela, Mexico (Lott et al.1987), and in a xeric system, at Sonora, Mexico(Molina-Freaner & Tinoco, 1997), liana abundancealso decreased in areas with low soil water availability.

As discussed above, the variation of liana abun-dance among sites may also result from differencesin forest gap dynamics. Liana abundance may changewith gap size and frequency as well as with the typeand persistence of disturbance (Appanah & Putz 1984;Hegarty & Caballé 1991). In the alluvial-terrace, floodplain, and low-hill sites, where liana abundance tendsto be high, most fallen trees are uprooted creating largegaps (> 200 m2; Martínez-Ramos et al., unpubl. data).The low liana abundance recorded in the karst-rangesites, on the other hand, may be associated with lowtreefall disturbance (Table 1b). Although the tree sizesat the karst-range are similar to those at the low-hills(Table 1), the gaps at the karst-range are smaller. Thisis because at the karst-range most gaps are producedby the fall of tree branches and snapped-off trees, notby entire trees being uprooted (Martínez-Ramos et al.,unpubl. data). It is possible that roots of the largetrees in the karst-range sites are strongly anchored tolimestone rocks, reducing the probability of uprooting.

Gentry (1991a) observed that in the Neotropicsliana species diversity declines from pluvial to drierforests. At Chajul, liana species diversity seems todecline with soil water availability, as discussed abovefor the case of liana abundance. Gentry’s observationthat liana diversity declines with the altitude can beapplied marginally to our study system, since karst-range sites are 200–500 m higher in altitude than theother study habitats. In contrast, liana species diver-sity did not decline with decreasing soil fertility asnoted by Gentry (1982, 1988, 1991a), and Appanah &Putz (1984) for other tropical localities. Thus, our datasupport the affirmation of Clinebell et al. (1995) thatspecies richness of lianas in tropical forests is inde-pendent of soil quality. Liana diversity was not lowerat the low-hills where soils have the poorest nutrientavailability, especially of phosphorous (Table 1).

Liana species composition and density greatly var-ied among habitats. Species differentiation related tosoil-topographic habitats has also been reported forliana species in a desert-scrub community (Molina-Freaner & Tinoco 1997), and for tree species inneotropical (Gentry 1986, 1988; Baillie et al. 1987;

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Hubbell & Foster 1986b) and Malaysian rain forests(Asthon & Hall 1992). The fact that species of thesame family or same genera tended to dominate dif-ferent habitats suggests that evolutionary niche differ-entiation has occurred within some liana phylogeneticlineages (Figures 5 and 6). For example, differentgenera of Bignoniaceae tended to dominate differenthabitats: Mansoa and Paragonia at alluvial-terraces;Stizophyllum at flooded sites; and, Callichlamys, Cy-dista and Arrabidaea at low-hill sites (Figure 7). Asimilar pattern occurred within genera. For example,the Bignoniaceae Arrabidade verrucosa was mostlypresent in the alluvial-terrace while A. patellifera andA. floribundum were more abundant at the low-hillsites; within Fabaceae, Machaerium floribundum wasover-represented in the flood plain habitat while M.lunatum was dominant in the low-hills (Figure 7).

At Chajul, similar patterns of taxonomic differ-entiation among closely related tree species are alsoapparent. For example, within the Leguminosae, Di-alium guianense is significantly more abundant inthe low-hills, Platymiscium yucatanum in the floodplains and Inga pavoniana in the alluvial terraces;within the Meliaceae, Trichillia acuntanthera is re-stricted to karst-range sites while Guarea species aremostly found at the lowland sites. Also, species of thesame genera show strong habitat differentiation. Ex-amples include Cymbopetallum, Guarea, Protium, andQuararibea species (Martínez-Ramos et al., unpubl.data). These observations suggest that in the studiedregion a purported evolutionary niche differentiationhas operated as a general phenomenon in the woodycommunities.

Conclusions

Liana communities vary strongly in their structuralcharacteristics and taxonomic composition across a100 km2 landscape in the Lacandon rain forest. Thevariation in some community attributes was compa-rable to that reported for other forests at much largergeographical scales. Liana abundance at Chajul isamong the highest recorded in tropical rain forests.The dominance-diversity relationship suggests that apre-emptive colonisation process may be driving theorganisation of the liana community, in a mannersimilar to that suggested for early successional plantcommunities. Several liana species were segregatedalong environmental gradients, producing an impor-tant level of β-species diversity. Soil water availability,

soil fertility, treefall disturbance regime, as well as theabundance and identity of trellis and tree hosts, mayinfluence the responses of the liana community to en-vironmental heterogeneity present at Chajul. We alongwith others (e.g., Gentry 1988, 1991a) propose severalhypotheses about factors influencing the communitystructure and composition of liana assemblages andalso about the population properties of lianas. Now,we urgently need to develop an experimental approachtesting these hypotheses.

Acknowledgements

The John D. and Catherine T. MacArthur Foundationand the Dirección General de Asuntos del PersonalAcadémico (project IN-209993 managed by MMR) ofthe National Autonomous University of Mexico pro-vided support for this study. We thank the help of San-tiago Sinaca in the fieldwork and species identificationand to J. Rodríguez-Velázquez for his technical sup-port in managing permanent plots and databases. C.Siebe provided us with unpublished data on soil char-acterisation. We appreciate the valuable comments ofJ. Benitez-Malvido, F. Sterck, L. López-Hoffman, D.Ackerly and two anonymous reviewers. We appreciatethe logistic support provided by the Biological FieldStation ‘Chajul’, managed by Instituto de Ecología,UNAM and Espacios Naturales A.C. The final ver-sion of this paper was finished at D. Ackerly’s lab,Department of Biological Sciences, Stanford Univer-sity, while MMR was on sabbatical, supported byfellowships from Consejo Nacional de Ciencia y Tec-nología (Mexico) and Dirección General de Asuntosdel Personal Académico (UNAM).

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Appendix I.List of species recorded in each of the eight study sites at the Lacandon rainforest, Southeast Mexico. Asterisksindicate species presence and last column gives the total number of sites (plots) in which each species was recorded.A = alluvial-terrace, F = flood plain, K = karst-range, and L = low-hill sites.

Family/species AT1 AT2 FP1 FP2 KR1 KR2 LH1 LH2 Total

Acanthaceae

Mendoncia guatemalensis Standl. & Steyerm. ∗ ∗ 2

M. retusa Turril ∗ ∗ 2

Amaranthaceae

Chamissoa altissima (Jacq.) Kunth ∗ ∗ 2

Apocynaceae

Forsteronia acouci (Aubl.) DC. ∗ 1

F. viridescens J. F. Blake ∗ ∗ ∗ ∗ ∗ ∗ ∗ 7

Prestonia guatemalensis Woodson ∗ 1

P. mexicana A. DC. ∗ 1

Arecaceae

Desmoncus quasillarius Bartlett ∗ ∗ ∗ ∗ ∗ ∗ 6

Aristolochiaceae

Aristolochia arborea Linden ∗ ∗ 2

Bignoniaceae

Amphilophium paniculatum (L.) Kunth ∗ 1

Anemopaema chrysantha Dugand ∗ ∗ ∗ 3

Arrabidaea florida DC. ∗ ∗ ∗ ∗ ∗ 5

A. patellifera (Schltdl.) Sandwith ∗ ∗ ∗ ∗ ∗ ∗ 6

A. verrucosa (Standl.) A. Gentry ∗ ∗ ∗ 3

Bignoniaceae 1 ∗ 1

Callichlamys latifolia (L.C. Rich.) K. Schum. ∗ ∗ ∗ ∗ 4

Cydista aequinoctialis (L.) Miers ∗ 1

C. diversifolia (Kunth) Miers ∗ ∗ ∗ ∗ ∗ ∗ 6

C. heterophylla Seibert ∗ ∗ ∗ 3

C. potosina (K. Schum & Loes.) Loes. ∗ ∗ ∗ ∗ ∗ ∗ ∗ 7

Macfadyena unguis-cati (L.) A. Gentry ∗ 1

Mansoa verrucifera (Schledl.) A. Gentry ∗ ∗ ∗ ∗ 4

Mussatia hyacinthina (Standl.) Sandwith ∗ ∗ ∗ ∗ ∗ 5

Paragonia pyramidata (L.C. Rich.) Bureau ∗ ∗ ∗ ∗ ∗ ∗ ∗ 7

Schlegelia parviflora (Oerst.) Monachino ∗ ∗ ∗ ∗ ∗ 5

Stizophyllum riparium (Kunth) Sandw. ∗ ∗ ∗ ∗ ∗ 5

Tynanthus guatemalensis J.D. Sm. ∗ 1

110

Appendix I. Continued.

Family/species AT1 AT2 FP1 FP2 KR1 KR2 LH1 LH2 Total

Boraginaceae

Cordia spinescens L. ∗ 1

Combretaceae

Combretum argenteum Bertol. ∗ ∗ ∗ ∗ ∗ ∗ ∗ 7

C. laxum Jacq. ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ 8

Compositae

Calea jamaicensis (L.) L. ∗ 1

Mikania leiostachya Benth. ∗ ∗ ∗ 3

Piptocarpha chontalensis J. S. Blake ∗ ∗ ∗ ∗ 4

Sinclairia discolor Hook. & Arn. ∗ ∗ 2

Zesmenia serrata La Llave & Lex. ∗ ∗ ∗ 3

Connaraceae

Cnestidium rufescens Planch. ∗ ∗ ∗ 3

Rourea glabra Kunth ∗ ∗ ∗ 3

Cucurbitaceae

Psiguria triphylla (Miq.) C. Jeffrey ∗ 1

Dichapetallaceae

Dichapetalum donnell-smithii Engl. ∗ ∗ ∗ 3

Dilleniaceae

Doliocarpus dentatus (Aubl.) Standl. ∗ ∗ 2

Tetracera volubilis L. ∗ ∗ ∗ ∗ ∗ ∗ 6

Euphorbiaceae

Acalypha sp. ∗ 1

Plukenetia penninervia Muell.Arg. ∗ 1

Fabaceae

Acacia hayesii Benth. ∗ ∗ ∗ ∗ ∗ ∗ 6

Bauhinia herrerae (Br. & Rose) Standl. & Steyerm. ∗ ∗ ∗ 3

Dioclea wilsonii Standl. ∗ 1

Machaerium cobanense J.D. Sm. ∗ 1

M. floribundum Benth. ∗ ∗ ∗ ∗ ∗ 5

M. kegelii Meisn. ∗ ∗ ∗ ∗ ∗ ∗ ∗ 7

M. lunatum ∗ ∗ ∗ ∗ ∗ 5

Mimosa recordii Britton & Rose ∗ ∗ 2

Gesneriaceae

Drymonia serrulata (Jacq.) Mart. ∗ ∗ 2

Hernandiaceae

Sparattanthelium amazonum Mart. ∗ ∗ 2

111

Appendix I. Continued.

Family/species AT1 AT2 FP1 FP2 KR1 KR2 LH1 LH2 Total

Hippocrateaceae

Hippocratea celastroides Kunth ∗ ∗ ∗ ∗ ∗ ∗ 6

Loganiaceae

Strichnos tabascana Sprague & Sandw. ∗ ∗ ∗ ∗ ∗ 5

Malpighiaceae

Heteropterys laurifolia (L.) Adr. Juss. ∗ ∗ ∗ ∗ 4

Hiraea fagifolia (DC.) Adr. Juss. ∗ ∗ ∗ ∗ ∗ ∗ ∗ ∗ 8

H. smilacina Standl. ∗ ∗ ∗ 3

Mascagnia rivularis C.V. Morton & Standl. ∗ ∗ 2

Stigmaphyllon dentatus ∗ 1

S. ellipticum (Kunth) Adr. Juss. ∗ 1

S. lindenianum Adr. Juss. ∗ ∗ ∗ 3

Tetrapterys schiedeana Schltdl. ∗ 1

Tetrapterys sp. ∗ 1

Malvaceae

Hibiscus sp. ∗ 1

Marcgraviaceae

Marcgravia mexicana Gilg ∗ 1

Souroubea loczyi (Al. Richter) de Roon ∗ ∗ ∗ 3

Menispermaceae

Abuta panamensis (Standl.) Krukoff & Barneby ∗ ∗ ∗ ∗ ∗ ∗ 6

Nyctaginaceae

Pisonia aculeata L. ∗ ∗ ∗ ∗ 4

Passifloraceae

Passiflora spp. ∗ 1

Phytolaccaceae

Trichostigma octandrum (L.) H. Walt. ∗ ∗ 2

Rhamnaceae

Gouania lupuloides (L.) Urb. ∗ ∗ 2

G. polygama (Jacq.) Urb. ∗ ∗ 2

Rubiaceae

Chione sp. ∗ 1

Randia sp. ∗ ∗ 2

Rubiaceae 1 ∗ 1

112

Appendix I. Continued.

Family/species AT1 AT2 FP1 FP2 KR1 KR2 LH1 LH2 Total

Sapindaceae

Paullinia clavigera Schltdl. ∗ ∗ ∗ ∗ 4

P. fuscescens Kunth ∗ ∗ ∗ 3

P. venosa Radlk. ∗ ∗ ∗ ∗ ∗ ∗ ∗ 7

Serjania goniocarpa Radlk. ∗ ∗ ∗ 3

S. mexicana (L.) Willd. ∗ ∗ ∗ ∗ ∗ ∗ ∗ 7

Thinouia myriantha Triana & Planchón ∗ ∗ ∗ ∗ ∗ ∗ 6

Sterculiaceae

Byttneria aculeata Jacq. ∗ 1

B. catalpifolia Jacq. ∗ 1

Ulmaceae

Celtis iguanaea (Jacq.) Sarg. ∗ 1

Urticaceae

Urera eggersii Hieron. ∗ ∗ ∗ ∗ 4

Verbenaceae

Aegiphila elata Sw. ∗ 1

Vitaceae

Cissus gossypiifolia Standl. ∗ ∗ ∗ ∗ ∗ 5

C. sicyoides L. ∗ 1

Vitis tiliifolia Kunth ∗ 1