Genotype-environment associations support a mosaic hybrid zone between two tidal marsh birds
Date
2015-12-29
Journal Title
Journal ISSN
Volume Title
Publisher
John Wiley & Sons Ltd.
Abstract
Local environmental features can shape hybrid zone dynamics when hybrids are
bounded by ecotones or when patchily distributed habitat types lead to a
corresponding mosaic of genotypes. We investigated the role of marsh-level
characteristics in shaping a hybrid zone between two recently diverged avian
taxa – Saltmarsh (Ammodramus caudacutus) and Nelson’s (A. nelsoni) sparrows.
These species occupy different niches where allopatric, with caudacutus
restricted to coastal marshes and nelsoni found in a broader array of wetland
and grassland habitats and co-occur in tidal marshes in sympatry. We determined
the influence of habitat types on the distribution of pure and hybrid
sparrows and assessed the degree of overlap in the ecological niche of each
taxon. To do this, we sampled and genotyped 305 sparrows from 34 marshes
across the hybrid zone and from adjacent regions. We used linear regression to
test for associations between marsh characteristics and the distribution of pure
and admixed sparrows. We found a positive correlation between genotype and
environmental variables with a patchy distribution of genotypes and habitats
across the hybrid zone. Ecological niche models suggest that the hybrid niche
was more similar to that of A. nelsoni and habitat suitability was influenced
strongly by distance from coastline. Our results support a mosaic model of
hybrid zone maintenance, suggesting a role for local environmental features in
shaping the distribution and frequency of pure species and hybrids across space.
Description
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Citation
Walsh, Jennifer, et al. "Genotype‐environment associations support a mosaic hybrid zone between two tidal marsh birds." Ecology and Evolution (2015).