The role that asexual reproduction plays in the regeneration of tropical Piper shrubs: Habitat differences and genetic consequences.

摘要

Asexual reproduction is a common, but little explored characteristic of many tropical plants with a variety of life-histories and habitat requirements. My dissertation research examined the ecological correlates and population genetic consequences of asexual reproductive success in five co-occurring Piper species using a combination of field experiments and molecular approaches. Working at the Barro Colorado Nature Monument (BCNM) Panama, I found that shade-tolerant species use asexual reproduction more often than do light-demanding species. Further, I showed that all Piper populations contain high genetic diversity regardless of the frequency of asexual reproduction in the population, and that these values of genetic diversity were higher than values found in most clonal plants in non-tropical ecosystems, but are similar to other clonal tropical plant species. Factors such as the accumulation of somatic mutations, habitat heterogeneity, and density dependent mortality, may be playing an important role in maintaining genetic diversity, despite high levels of asexual recruitment. I also integrated spatial geographic data with spatial genetic data and found that more than 50% of neighboring plants were close relatives and clones. I hypothesize that the strong spatial genetic structure found in this genus is the result of clumped dispersal of genetically related seeds and of a lack of overlap in the feeding territories of their seed dispersal agents, Carollia bats. Finally, one of the most striking findings of this research is that gene flow in these five Piper shrub species is generally more restricted than for tropical tree species. Limited gene flow, localized clonal spread and genetic drift could favor the establishment of small reproductively isolated populations, potentially leading to the speciation of some of the >1000 species of Piper currently present in the Tropics.