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Analysis of ancestry heterozygosity suggests that hybrid incompatibilities in threespine stickleback are environment dependent
Hybrid incompatibilities occur when interactions between opposite ancestry alleles at different loci reduce the fitness of hybrids. Most work on incompatibilities has focused on those that are "intrinsic," meaning they affect viability and sterility in the laboratory. Theory predicts that ecological selection can also underlie hybrid incompatibilities, but tests of this hypothesis using sequence data are scarce. Thompson et al. compiled genetic data for F2 hybrid crosses between divergent populations of threespine stickleback fish (Gasterosteus aculeatus L.) that were born and raised in either the field (seminatural experimental ponds) or the laboratory (aquaria). Because selection against incompatibilities results in elevated ancestry heterozygosity, they tested the prediction that ancestry heterozygosity will be higher in pond-raised fish compared to those raised in aquaria. The authors found that ancestry heterozygosity was elevated by approximately 3% in crosses raised in ponds compared to those raised in aquaria, providing evidence that, in stickleback, a signal of environment-dependent hybrid incompatibility is reliably detectable and suggesting that extrinsic incompatibilities can evolve before intrinsic incompatibilities. The image shows drawings of individuals from each of the stickleback populations studied (from top; freshwater, marine, limnetic and benthic populations).
Image Credit: Katie Chu
Citation: (2022) PLoS Biology Issue Image | Vol. 20(1) January 2022. PLoS Biol 20(1): ev20.i01. https://doi.org/10.1371/image.pbio.v20.i01
Published: January 31, 2022
This is an open-access article distributed under the terms of the Creative Commons Public Domain declaration which stipulates that, once placed in the public domain, this work may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose.
Hybrid incompatibilities occur when interactions between opposite ancestry alleles at different loci reduce the fitness of hybrids. Most work on incompatibilities has focused on those that are "intrinsic," meaning they affect viability and sterility in the laboratory. Theory predicts that ecological selection can also underlie hybrid incompatibilities, but tests of this hypothesis using sequence data are scarce. Thompson et al. compiled genetic data for F2 hybrid crosses between divergent populations of threespine stickleback fish (Gasterosteus aculeatus L.) that were born and raised in either the field (seminatural experimental ponds) or the laboratory (aquaria). Because selection against incompatibilities results in elevated ancestry heterozygosity, they tested the prediction that ancestry heterozygosity will be higher in pond-raised fish compared to those raised in aquaria. The authors found that ancestry heterozygosity was elevated by approximately 3% in crosses raised in ponds compared to those raised in aquaria, providing evidence that, in stickleback, a signal of environment-dependent hybrid incompatibility is reliably detectable and suggesting that extrinsic incompatibilities can evolve before intrinsic incompatibilities. The image shows drawings of individuals from each of the stickleback populations studied (from top; freshwater, marine, limnetic and benthic populations).
Image Credit: Katie Chu