Population genetics of the understory fishtail palm Chamaedorea ernesti-augusti in Belize: high genetic connectivity with local differentiation
1 Department of Ecology, Evolution and Environmental Biology, Columbia University, 1200 Amsterdam Avenue, Mail Code 5557, New York, NY 10027, USA
2 Department of Biology, New Mexico State University, P.O. Box 30001 MSC 3AF, Las Cruces, NM 88003, USA
3 Department of Plant Biology Life Science II, Southern Illinois University, Mail Code 6509, 1125 Lincoln Drive, Carbondale, IL 62901, USA
4 Jodrell Laboratory, Royal Botanic Gardens Kew, Richmond, Surrey, TW9 3DS, UK
5 Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, CB2 3EA, UK
6 Natural History Museum, Cromwell Road, London, SW7 5BD, UK
7 Department of Biology, Georgetown University, 37th & O Streets NW, Washington, DC 20057, USA
8 Sackler Institute for Comparative Genomics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA
9 Department of Biology, Colorado State University, Campus Delivery 1878, Fort Collins, CO 80523, USA
10 Current address: Plant Genomics Laboratory, The New York Botanical Garden, 200th Street and Kazimiroff Boulevard, Bronx, NY 10458-5126, USA
BMC Genetics 2009, 10:65 doi:10.1186/1471-2156-10-65Published: 9 October 2009
Developing a greater understanding of population genetic structure in lowland tropical plant species is highly relevant to our knowledge of increasingly fragmented forests and to the conservation of threatened species. Specific studies are particularly needed for taxa whose population dynamics are further impacted by human harvesting practices. One such case is the fishtail or xaté palm (Chamaedorea ernesti-augusti) of Central America, whose wild-collected leaves are becoming progressively more important to the global ornamental industry. We use microsatellite markers to describe the population genetics of this species in Belize and test the effects of climate change and deforestation on its recent and historical effective population size.
We found high levels of inbreeding coupled with moderate or high allelic diversity within populations. Overall high gene flow was observed, with a north and south gradient and ongoing differentiation at smaller spatial scales. Immigration rates among populations were more difficult to discern, with minimal evidence for isolation by distance. We infer a tenfold reduction in effective population size ca. 10,000 years ago, but fail to detect changes attributable to Mayan or contemporary deforestation.
Populations of C. ernesti-augusti are genetically heterogeneous demes at a local spatial scale, but are widely connected at a regional level in Belize. We suggest that the inferred patterns in population genetic structure are the result of the colonization of this species into Belize following expansion of humid forests in combination with demographic and mating patterns. Within populations, we hypothesize that low aggregated population density over large areas, short distance pollen dispersal via thrips, low adult survival, and low fruiting combined with early flowering may contribute towards local inbreeding via genetic drift. Relatively high levels of regional connectivity are likely the result of animal-mediated long-distance seed dispersal. The greatest present threat to the species is the potential onset of inbreeding depression as the result of increased human harvesting activities. Future genetic studies in understory palms should focus on both fine-scale and landscape-level genetic structure.