(uniola paniculata) poaceae,andadaptations ... · ofseaoats(uniola...

Understanding relationships between evolutionary historyof Sea Oats (Uniola paniculata) Poaceae, and adaptations

to environmental conditions

Background:A long ribbon of barrier islands, which shelters inland habitats,estuaries, lagoons and sounds, borders the southeastern coastof the United States. Even during normal conditions, the ocean strikes the coastline withsubstantial force. Oceanfront sand dunes absorb the initial main impact of the ocean's en-ergy. After beaches, dunes are the second line of defense in protecting the land from the sea.Their effectiveness in the defense of interior terrestrial habitats against waves, winds, tides andstorms depends upon their height and stability, which in turn depends on dune vegetation.The principal native dune-forming vegetation along the southeastern North American coastis sea oats, Uniola paniculata (Poaceae) (Figure 1 and 2). Sea oats are used in restoration

projects because they are one of the most effective native sand-binding and dune-buildinggrasses. However, there is a lack of scientific data regarding which natural populations aremost suitable as a source of propagules, and there is considerable disagreement about howto delineate local provenances. Furthermore, a major unresolved issue in evolutionary biol-ogy is the relationship between molecular measures of genetic diversity and quantitative vari-ation (Frankham 1999). Our research project addresses this problem by using simultaneousanalyses of evolutionary history and the distribution of genetic diversity (measured by neu-tral genetic markers) and geographic patterns of adaptive variation (measure by morpholog-ical and reproductive traits).

Objectives:The overarching objective is to define Evolutionary Significant Units(ESUs) and Management Units (MUs) based on:i) evolutionary history and historical dispersalii) geographic distribution of adaptive traits.Specific objectives:A. Reconstruct a phylogeographic history of Uniola paniculata

based on chloroplast DNA (cpDNA). Phylogeographic struc-ture will provide the basis for the delineation of ESUs.

B. Test congruence between phylogeographic structure and dis-tribution of nuclear genetic diversity.

C. Measure the distribution of adaptive variation across geo-graphic range of U. paniculata.

D. Test for congruence between the distribution of genetic diver-sity (both cpDNA and nuclear DNA) and adaptive traits. Thisanalysis will provide a basis for delineating MUs and identify-ing the most suitable propagules for habitat restoration.

MethodsLaboratory analysis:We will PCR-amplify specific non-coding cpDNA regions using universal primersand sequence the amplified fragments from 300-350 plants representing the entirecontemporary geographic range of sea oats.Phylogeographic analysis and delineation of ESUs:We will use cpDNA sequence variation to infer intra-specific phylogeny and to re-construct sea oats phylogeography. We will consider populations belonging to eachcpDNA lineage (i.e., sharing the same haplotype) a separate ESU.

Preliminary results and discussionPhylogeography:Cp DNA haplotype diversity:We identified seven variable cpDNA fragments result-ing in FIVE cpDNAhaplotypes clustered into two major groups: Western (TX, MS)and Eastern (MS, FL, GA, SC, NC, VA). Each of the major clades has internal and

more shallow subdivisions (sub-clades) separated by fewer mutations (i.e., se-quence differences) (Table 1).Cp DNA haplotype geographic distribution: The geographic distribution of haplo-types is clustered in most cases, although there are some unexpected results withhaplotypes located outside of their main range. Furthermore, there are unique hap-lotypes located along the coast from Northern Florida to South Carolina, imbeddedin the center of the most common lineage. This unexpected complexity can be ex-plained by human introductions of non-local haplotypes, by homoplasy, and by long-term isolation of populations along sea oats! naturally fragmented range. Seeddispersal mitigated by the Gulf Stream and patterns of tropical storms may con-tribute to observed haplotype distribution.

Evolutionary significant units and adaptive traitsWhile cpDNA clades provide information about independent maternal lineages thatmay have evolved separately from each other, they do not provide any informationregarding the evolution of adaptive traits in these populations. We compared thephylogeographic structure of sea oats with a previously published study on the dis-tribution of morphological traits (Seneca 1972). The distribution of these presumablyadaptive traits is only partially congruent with phylogeography (Figures 3 and 4).We are collecting more extensive data regarding adaptive and reproductive traitsand their geographic distribution. This comparison will lead to delineation of MUs,taking into account both evolutionary history (based on cpDNA) and adaptive vari-ation shaped by natural selection (based on reproductive and morphological char-acters). Thus, our research will provide new science-based tools for designingrestoration and conservation management strategies.

Future directions: evolutionary significant units,adaptations and climate changeA. The outcome of our current investigation will form a foundation for subsequent

growth chamber experiments testing the response of U. paniculata to a range oftemperatures and CO2 concentrations predicted for the next 100 years. We willmeasure both reproductive and vegetative traits (e.g., pollen development andfertility, grain filling, above and below ground biomass) and investigate the vari-ation of plant responses within and among populations, MUs and ESUs.

B. We will investigate the variation of sea oats in their mycorrhizal associationsacross the entire geographic range.

Figure 3: Geographic distribution of Uniola paniculata chloroplast DNA lineagesdisplays more complexity and only partial congruence with previously reporteddivergence in morphological traits. This complexity may potentially be explainedby human introduction of non-native cpDNA haplotypes.

Figure 4: Divergence in morphological traits (e.g., seed germination, biomassproduction, salinity tolerance) among populations of Uniola paniculata clusteredinto three geographical regions: I. Gulf of Mexico, II. Atlantic coast of Floridaand III. Virginia and North Carolina (modified from Seneca 1972).

Figure 5: The UPGMA dendrogram based on genetic distance (allozyme mark-ers, presumably neutral) demonstrates more complexity and weak geographicpattern or congruence with both: cpDNA and morphological variation (modifiedfrom Franks et al 2004).

Gonzales E. and R. Hodel Appalachian State University, Boone, NC

References:Frankham R (1999) Quantitative genetics in conservation biology. Genetical Research. 4, 237-244. – Franks, SJ, Richards, CL, Gonzales, E, Cousins, JE, Hamrick JL (2004) Multi-scale geneticanalysis of Uniola paniculata (Poaceae): a coastal species with a linear, fragmented distribution. American journal of Botany, 91, 1345-1351. – Moritz, C (1994) Defining “Evolutionary SignificantUnits” for conservation. Trends in Ecology and Evolution, 9, 373-375. – Moritz, C (1999) Conservation units and translocations: strategies for conserving evolutionary processes. Hereditas, 130,21-228. – Seneca, ED (1972) Germination and seedling response of Atlantic and Gulf coasts populations of Uniola paniculata. American Journal of Botany. 59, 290-296.Acknowledgment:Funding provided by: NC Sea Grant (2010-2011) Sand Dune Restoration: What is local? Understanding Relationships Between Evolutionary History of Sea Oats (Uniola paniculata) Poaceaeand Adaptations to Local Environmental Conditions. – Appalachian State University URC (University Research Council): (2009) Reconstructing phylogeographic history of sea oats (Uniolapaniculata, Poaceae), and its application to conservation and restoration of coastal habitats.

Table 1: Pairwise matrix of cpDNA haplotype divergence. Each number indicate number ofmutations (SNPs or single nucleotide indels) between haplotypes.

Figure 1: Cape Hatteras, NC

Figure 2: Huntington Beach, SC