Resolving the phylogeny and population genetic structure of South African pollinating fig wasps

Abstract

A distinct pattern of obligate mutualism exists between fig tree hosts and their pollinating fig wasps. Normally one section or subsection of fig tree hosts is associated with one fig wasp genus. In general, each species is pollinated by a specific fig wasp species. This led to the hypothesis that the fig wasp and fig tree lineages diverged simultaneously. African fig wasps pollinating hosts of the Galoglychia section frequently break the normal one fig wasp species-to-one host species ratio. The phylogeny for these species was reconstructed using three DNA segments and compared to the morphological classification of their Ficus hosts. Pollinator genera were monophyletic for all analyses, however, the relative positioning of genera was inconsistent. Analyses suggest frequent host jumps between fig trees and fig wasps. Fig wasps of the genus Alfonsiella that pollinate Ficus craterostoma, Ficus stuhlmannii and Ficus petersii are morphologically similar in South Africa. Based on host association, genetic differentiation for this group was investigated. Molecular data indicated that the pollinator of F. craterostoma is a good species, while the F. stuhlmannii and F. petersii pollinators were genetically indistinguishable. Based on molecular data and morphological re-evaluation, a new Alfonsiella species is described, Alfonsiella pipithiensis sp. n. A key to all described species of Alfonsiella is provided. In order to resolve the population genetic differentiation of pollinating fig wasp species in South Africa, Platyscapa awekei was used as a model species. A few studies indicate that pollinating fig wasps can disperse between 30 and 55 kilometers. However, a recent study on two P. awekei populations in South Africa reported an FST value of 0.011, indicating that pollinators disperse approximately ten times further. This study aims to confirm these results with more detailed sampling of populations. In addition, possible temporal differentiation was tested for the South African population. Six microsatellite loci were used to detect spatial and temporal genetic differentiation in seven populations (collected from 2004 to 2006) over a 340 kilometer range. Genetic differentiation between sampled populations was low (FST = 0.0055), however, the data suggest stronger temporal genetic isolation than spatial genetic isolation.