Contemporary pollen-mediated gene immigration reflects the historical isolation of a
rare,animal-pollinated shrub in a fragmented landscape |
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Authors: | J F Sampson M Byrne C J Yates N Gibson R Thavornkanlapachai S Stankowski B MacDonald I Bennett |
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Institution: | 1.Science Division, Department of Parks and
Wildlife, Bentley Delivery Centre, Bentley, Western Australia, Australia;2.Centre for Ecosystem Management, Edith Cowan
University, Joondalup Western Australia, Australia |
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Abstract: | Fragmentation is generally considered to have negative impacts on widespread outbreeders
but impacts on gene flow and diversity in patchy, naturally rare, self-compatible plant
species remain unclear. We investigated diversity, gene flow and contemporary
pollen-mediated gene immigration in the rare, narrowly distributed endemic shrub
Calothamnus quadrifidus ssp. teretifolius. This taxon occurs in an
internationally recognized biodiversity hotspot subjected to recent human-induced
fragmentation and the condition of the remnants ranges from intact to highly degraded.
Using microsatellites, we found that inbreeding, historically low gene flow and
significant population differentiation have characterized the genetic system of C.
quadrifidus ssp. teretifolius. Inbreeding arises from self-pollination, a
small amount of biparental inbreeding and significant correlation of outcross paternity
but fecundity was high suggesting populations might have purged their lethals. Paternity
analyses show that pollinators can move pollen over degraded and intact habitat but
populations in both intact and degraded remnants had few pollen parents per seed parent
and low pollen immigration. Genetic diversity did not differ significantly between intact
and degraded remnants but there were signs of genetic bottlenecks and reduced diversity in
some degraded remnants. Overall, our study suggests human-induced fragmentation has not
significantly changed the mating system, or pollen immigration to, remnant populations and
therefore genetic connectivity need not be the highest conservation priority. Rather, for
rare species adapted to higher levels of inbreeding, conservation efforts may be best
directed to managing intact habitats and ecosystem processes. |
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Keywords: | fragmentation gene flow diversity pollen immigration ironstones conservation |
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