Urban Plants as Genetic Reservoirs or Threats to the Integrity of Bushland Plant Populations

Presented by Shannon Slivinske

Urban plants- contributing to plant conservation, or further threatening the gene pool?

Habitat fragmentation- increase in isolation and decrease in (population) size of natural resource patches, inevitably isolated remnants of natural forests. Species with patchy distribution and rare classification, more susceptible, esp. to "edge effects"

Grevillea macleayana McGillivray

New South Whales South coast Lifespan: decades undisturbed,

senescence after 20-30 yrs. No obvious seed dispersal

mechanism Germination after disturbance Flowers year round Inflorescences of 50

hermaphroditic, self-compatible flowers

Four bushland stands isolated by 1 km (except CB)

Six stands within Hyams Beach Village

Jervis Bay National Park (CB, Chinamans Beach; GB, Greenfields Beach; ILL, Illowra Lane; HB, Hyams Beach) and stands within an adjacent urban setting (HBV, Hyams Beach Village).

Examined:

1. Reproductive effort and success

2. Pollinator visitation and behavior

3. Genetic diversity and population differentiation

4. Outcrossing and gene flow

1.Reproductive effort (flowering intensity) and success (seeds set per plant)

15 plants from 3 stands # inflorescences every 3 weeks Mar. ’01-Sept.

’01 Crown volume (NS) 1-12 inflorescences, seed initiation after 3 weeks

and every 3 weeks until maturation

Methods

2. Pollinator Visitation and Behavior

Grevillea provide important resources for native nectarivores and insectivores in suburban areas

Pollinators- honeybee and honey-eaters observed on same sites

Visitor rate of pollinators- # inflorescences and # visits/inflorescence per 15-min

% foraging movement that were inter vs. intraplant- # plants visited per pollinator and # inflorescences per plant

3. Genetic Studies

Leaf material from all adult plants was collected and 4-15 seeds from 5-9 plants in each stand (3 from remnant and 3 from exotic in HBV)

DNA extraction using CTAB extraction protocol of Doyle and Doyle

4. Statistical Analysis

ANOVA to analyze Pollinator data Principal Coordinates Analysis- genetic distance

matrix POPGENE- standard population genetic

parameters Weir and Cockerham's formulation of Wright's F statistics- partition genetic variation

MLTR- level of outcrossing in each stand Biparental inbreeding level versus inbreeding CERVUS- scale and pattern of gene flow from

urban-bushland and assign paternity from seed sets

1. Plant Reproductive Effort and Success

Inflorescence production: Peak July-Sept

Urban- 1180, Bush- 753 and 892

Fruit initiation/inflorescence: Urban 1-12, Bush 1-6

Seed maturation: Urban 1-2, 11.1%, Bush 1-3, 12.1%(CB) and 2.4%(GB)

Results

2. Pollinator Visitation and Behavior

Foraging movement:

Honeyeaters- 80% b/w inflorescences on same plant

Honeybees- 90% b/w inflorescences on same plant

Observed honeyeaters flying between gardens and bushland, including between exotic stand and bush

3. Genetic Diversity and Population Differentiation All stands varied for at least 9 of 10 studied loci # alleles for GmE, Gm10 and Gm25 were 13-14,

2-8 for remainder 89% all alleles present in Urban, only 39%-52%

for Bush 27/30 private alleles within Urban, 17 in 19 with

unusual morphology

4. Outcrossing and Gene Flow

Low-intermediate outcrossing in all stands

157/358 seeds selfed 95/358 outcrossed,

62% within same stand

7-29 seeds outcrossed between stands

No exotic alleles in bushland or remnant

HBV plants:

Genetic diversity indicates disturbance resistance/resilience

Aesthetically pleasing as garden plants, less susceptible to drought/fire threat

Buffer loss of genetic diversity from bushland stands

Low-moderate outcrossing indicates regional functionality

Retained most alleles, contained most variation While about 77% adults in HBV contained 10

private alleles,

19 exotics/cvs with 17-27 private alleles (possibly deleterious)

Reduce fitness, outbreeding depression, possible extinction

Remnants may worsen as bridges Protection from fire also reduces future

generation germination potential

Honeybees: Introduced, potential gene-flow suppressant Increase inbreeding and reduce gene flow

Honey-eaters: patchy nature of nectar resources encourages

nomadism, less so in urban environments

Questions and Discussion

Works Cited Eastern Spine-billed honey-eater photo by Brett Donald on

Wikipedia Goosem, S. and N.I.J. Tucker (1998) Theory. Chapter 1 in:

Repairing the rainforest -- theory and practice of rainforest re-establishmnet in north Queensland's Wet Tropics. Wet Tropics Management Authority, Cairns.

Jean Clarke. 2002. Grevillea macleayana. Growing Native Plants, Australian National Botanic Gardens.

http://www.anbg.gov.au/gnp/interns-2002/grevillea-macleayana.html. October 13, 2008.

French, K., Major, R. and K. Hely. Use of Native and Exotic Garden Plants by Suburban Nectarivorous Birds. Biological Conservation 121 (4): 545-559, 2005.

Roberts, David G., Whelan, R. J., Ayre, D. J. and Phillip R. England. The Potential for Genetic Contamination vs. Augmentation by Native Plants in Urban Gardens. Biological Conservation 128 (4): 493-500, 2005.

Roberts, David G., Ayre, D. J. and Robert J. Whelan. Urban Plants as Genetic Resevoirs or Threats to the Integrity of Bushland Plant Populations. Conservation Biology 21 (2): 842-852, 2006.