Genetic Dynamics in Hybrid Zones of Small Mammals
Summary
Hybrid zones between closely related small mammal species serve as natural laboratories for investigating the balance between gene flow and selection across ecological gradients. In these regions of secondary contact, parental species may exchange genetic material, producing hybrids of varying fitness and adaptive potential. The structure of hybrid zones can range from narrow tension zones, maintained by selection against hybrids, to wide mosaic zones, where environmental heterogeneity permits differential introgression of adaptive alleles. Patterns of genomic admixture reveal both broad‐scale and locus‐specific variation, driven by factors such as ecological niche divergence, behavioural isolation, and post-zygotic barriers. Studies in woodrats (Neotoma spp.), field voles (Microtus agrestis) and mice (Peromyscus spp.) illustrate how dietary specialisation, toxin metabolism and mate choice interact with demographic history to shape the distribution of hybrid genotypes. Recent advances in high-throughput sequencing and spatial modelling have shed light on the genomic regions that resist or facilitate introgression, as well as the evolutionary forces that stabilise species boundaries. Understanding these dynamics has broad implications for speciation theory, conservation management of cryptic taxa and predicting responses to environmental change.
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Genetic Dynamics in Hybrid Zones of Small Mammals publication trend
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Technical terms
Hybrid zone: A geographical region where two genetically distinct populations meet, mate and produce offspring of mixed ancestry.
Introgression: The incorporation of genetic material from one species into the gene pool of another through repeated backcrossing.
Backcrossing: The process by which a hybrid individual mates with one of its parental species, leading to successive generations with increasing proportions of one species’ genome.
Tension zone: A hybrid zone maintained by a balance between dispersal of parental genotypes into the zone and selection against hybrids.
Bimodal zone: A hybrid zone in which parental genotypes predominate and hybrids are relatively rare or unfit, resulting in a bimodal distribution of genotypes.
References
- Differences in dietary composition and preference maintained despite gene flow across a woodrat hybrid zone. Ecology and Evolution (2021).
- Experimental evidence for asymmetric mate preference and aggression: behavioral interactions in a woodrat (Neotoma) hybrid zone. BMC Ecology and Evolution (2013).
- Hybridization in the absence of an ecotone favors hybrid success in woodrats (Neotoma spp.). Evolution (2023).
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