Meeting Abstract
The factors determining the geographic distribution of organisms has long been of interest to organismal biologists. Eco-physiological studies have shown that what limits an organism’s range in nature is not often one single factor, but rather the tolerance to multiple biotic/abiotic factors that vary across an organism’s range. With the advent of modern genomic sequencing we can not only document the genes underlying environmental tolerance, but also the mechanistic basis for why they serve as evolutionary barriers to range expansion. Here we investigate the range limit of the Trinidadian guppy, Poecilia reticulata which is restricted to freshwater in Trinidad despite its ability to survive in brackish water in the lab and other parts of its range. Transplant experiments and behavioral studies show that salinity and competition with a closely related species, Poecilia picta , interact antagonistically to limit P. reticulata’s range. This negative interaction is perhaps mediated by the fact that P. reticulata becomes subordinate to P. picta when in brackish water. In addition to documenting this interaction at the phenotypic level, we also investigated it at the transcriptomic level. We looked at transcriptome wide gene expression in the gills and brain of P. reticulata in different salinities and in different competitive environments to investigate if the negative phenotypic interaction is due to an antagonistic interaction between the transcriptomic responses underlying osmoregulation and aggression. Our genotype-to-phenotype approach can help to understand the complex pleiotropic trade-offs associated with different environmental challenges.
