Population genetic structure in three sympatric Ficus species associated with copollinator

Abstract

Understanding the factors contributing to genetic structure among closely related sympatric species is crucial for grasping adaptive divergence and speciation initiation. We focused on three dioecious fig trees (Ficus hispida, Ficus heterostyla, and Ficus squamosa) that constitute a clade of closely related species pollinated by closely related Ceratosolen wasps. Analyzing microsatellite data (64 sampling locations) and chemical volatiles for fig trees and inferring the phylogenetic relationships of their pollinating wasps, we show that despite sharing of a large proportion of volatile compounds and a few exchanges of pollinators, all species maintain genetic and morphological integrity. Admixture of F. heterostyla and F. hispida in F. squamosa is detected at its distribution margin. Two genetically distinct clusters of F. heterostyla, possibly indicating cryptic fig species pollinated by distinct pollinators, are highlighted. Ficus hispida is genetically homogeneous over its studied range but associated with at least three pollinator species. Life history traits of each Ficus species (fruiting mode, population density, flowering pattern, habitat preference) and seed dispersal mode (hydrochorous, zoochorous) are discussed together with elements on the morphology and biology of their pollinators to explain observed results. This study contributes to our understanding of how species in the fig–wasp mutualism diversify and coexist.