Ecology and genetics of hybrid animals

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Hybridization is increasingly recognized as a diversifying force in animal evolution. High hybrid fitness is more frequent in novel, marginal, or dynamic habitats. Causes of higher hybrid fitness, however, are only partly known. My research program employs an integrative approach involving field and experimental studies coupled with genetic characterization to investigate how new genetic combinations can provide higher fitness in dynamic ecological settings. I take advantage of the Fundulus hybrid complex where two fish species (Fundulus heteroclitus and F. diaphanus) typically found at different salinities have hybridized to produce sexually reproducing and gynogenetic hybrids. The latter comprises all-female clones that need sperm from Fundulus males to trigger egg development. Ecological surveys are conducted to establish the relative distribution of parental and hybrid forms in habitats of intermediate and/or variable salinity such as estuaries, tidal rapids, coastal lakes and lagoons. In parallel, preliminary estimates of hybrid frequency, introgression levels and clonal diversity are refined by genome-wide genetic characterization with AFLP markers. Ecological and genetic knowledge are coupled by examining fitness-related traits such as ionoregulation ability, survival and growth in the field (transplant experiments) and in the lab (common garden experiments). Here, the availability of fixed clonal genotypes is particularly appropriate to disentangle the genetic, maternal, environmental sources of phenotypic variation impacting on fitness components. Given their constant genetic background, clones are also useful to examine allelic gene expression in hybrids. This integrated analysis of natural gynogens will offer opportunities to test competing hypothesis on the ecological breadth of clones. This research will also be relevant to the fields of functional and environmental physiology and genomics, which use F. heteroclitus as a model organism. The proposed research will involve one Ph. D., three M. Sc., and five B. Sc students. These students will be trained in documenting and interpreting ecological, phenotypic and genetic variation from a holistic point of view.