Fig wasp Research

We take advantage of a solid background on the ecology and natural history of fig wasps to ask relevant molecular evolution and population genetics questions. Current interests include studying the genetic consequences of evolution in subdivided populations, the extent of cospeciation between Neotropical figs and their pollinators, the geographical context of speciation and cospeciation in the mutualism, and the potential for genetic introgression across different fig species due to pollinator host switches (see fig research).

Population structure and genetic diversity in fig wasps

We have developed an EST database for one species of Pegoscapus pollinator from Panama (Pegocapus estherae, ex. Ficus costaricana), that we are using to develop sequencing markers for population genetics and molecular evolution studies. In particular, the extremely subdivided population structure of fig wasps, and the ease of approximately estimating that structure without genetic data, make fig pollinating wasps an ideal system for conducting studies of the genetic consequences of evolution in subdivided populations. Population genetic studies of mtDNA and nuclear variation in 11 fig wasp species show a pattern consistent with the effects of directional selection (hithchiking) or selection against linked deleterious mutations (background selection) acting on any region of the genome but affecting mitochondrial and nuclear loci equally due to the effective linkage generated by the extreme levels of inbreeding observed in these species. Additional analyses that look at the frequency spectrum of segregating mutations suggest that directional selection might be the most plausible mechanism responsible for the observed pattern, thus suggesting the action of selective sweeps with potential genome-wide consequences in fig wasps. We are interested in determining how often selective sweeps occur in these species and whether they are correlated with the level of population subdivision.

The effect of Wolbachia infection in fig wasps

Population genetic and evolutionary studies are being conducted in the context of a NSF grant (DEB-0108475) to study the dynamics of Wolbachia in fig communities. Wolbachia are alpha-proteobacteria that are found in a wide range of arthropods and filarial nematodes, and that cause a diverse range of important fitness-related phenotypic effects on their hosts. A variety of strains of Wolbachia infect many species of Neotropical fig wasps. The high frequencies of Wolbachia infections and the biology of fig wasps allows unparalleled opportunities to address interconnected questions concerning Wolbachia in natural populations:

1) the ecological and evolutionary transmission of Wolbachia;
2) the population dynamics of Wolbachia;
3) the effects of Wolbachia on their hosts' reproduction and how that is related to population structure;
4) molecular evolution in Wolbachia and the effects of Wolbachia infections on fig wasp genetic variation.

No previous study has been able to address all of the above questions and the relationships between them. This work is being conducted in collaboration with Dewayne Shoemaker (USDA) and Allen Herre (STRI).

All contents copyright © 2005 Carlos Machado. All rights reserved.