Abstract
Many large species have declined worldwide due to habitat fragmentation and poaching. The defaunation of large frugivores and the consequent reductions of seed dispersal services may have immediate effects on plant demography. Yet, the lasting effects of frugivore defaunation on microevolutionary processes of the plants they disperse remain understudied. We tested if the loss of large seed dispersers can lead to microevolutionary changes of a tropical palm. We show that frugivore defaunation is the main driver of changes in allelic frequency among populations. Turnover of alleles accounted for 100% of dissimilarity in allelic frequencies of individuals between defaunated and non-defaunated forests; and individuals from defaunated sites are 1.5 times more similar genetically than those found in pristine sites. Given that sizeable fractions of the palm fruit crops remain undispersed in defaunated sites due to lack of large-bodied frugivores, this distinct pattern of gene pool composition of early recruits may reveal strong dispersal limitation for specific genotypes, or collapses of gene flow between fragmented areas, or both. Because most of tropical tree species rely on seed dispersal by vertebrates, our results show that defaunation has a lasting effect on microevolutionary processes, with potential consequences for persistence under scenarios of environmental change.
Highlights
Defaunation: The loss of large seed dispersers may led to microevolutionary changes among populations due to a selection against large seed size and to the collapse of the long-distance seed dispersal events
We found that microevolutionary changes between defaunated and non-defaunated sites and between rain forest and semideciduous forest were not due to changes in genetic variability or contemporary effective population size
Our results indicate that the defaunation of large seed dispersers has a distinct signal on large-scale genetic variability, potentially arising from microevolutionary changes in the palm populations
Summary
Defaunation: The loss of large seed dispersers may led to microevolutionary changes among populations due to a selection against large seed size and to the collapse of the long-distance seed dispersal events. Biogeographical regions: Rain forest and semideciduous forest may led to microevolutionary changes among populations due to their influence on the distribution of genetic variability through evolutionary time, and due to the distinct selective regimes imposed by biogeographical differences between the two regions. High correct assignment (Kappa) and β-allelic diversity among rain forest sites similar to semideciduous forest sites. Forest Fragmentation: Forest fragmentation may led to microevolutionary changes among populations because of the associated drastic reductions in population size, and may increase the effect of spatial isolation among populations. Sampling design: Given that individuals were sampled in delimited and isolated populations, the sampling design may generate differences in the gene pool among populations
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