Differential high‐altitude adaptation and restricted gene flow across a mid‐elevation hybrid zone in <scp>A</scp>ndean tit‐tyrant flycatchers

DuBay, Shane G.; Witt, Christopher C.

doi:10.1111/mec.12836

Cited by 57 publications

(58 citation statements)

References 88 publications

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“…2012), vegetation/substrate gradients (Shurtliff et al. 2013), bioclimatic gradients (Tarroso 2014), and elevational gradients (DuBay and Witt 2014). This study offers empirical evidence for exogenous selection in a novel ecotone, providing support for hybrid zone maintenance along tidal marsh gradients.…”

Section: Discussionmentioning

confidence: 99%

Genotype‐environment associations support a mosaic hybrid zone between two tidal marsh birds

Walsh

Rowe

Olsen

et al. 2015

Ecology and Evolution

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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.

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Section: Discussionmentioning

confidence: 99%

Genotype‐environment associations support a mosaic hybrid zone between two tidal marsh birds

Walsh

Rowe

Olsen

et al. 2015

Ecology and Evolution

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“…This movement of individuals after isolation could be random; alternatively, landscape features and ephemeral dispersal corridors, in conjunction with physiological constraints, could produce congruent patterns of gene flow (e.g. Cheviron & Brumfield ; DuBay & Witt ; Cadena et al . ).…”

Section: Introductionmentioning

confidence: 99%

Isolation with asymmetric gene flow during the nonsynchronous divergence of dry forest birds

et al. 2017

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Dry forest bird communities in South America are often fragmented by intervening mountains and rainforests, generating high local endemism. The historical assembly of dry forest communities likely results from dynamic processes linked to numerous population histories among codistributed species. Nevertheless, species may diversify in the same way through time if landscape and environmental features, or species ecologies, similarly structure populations. Here we tested whether six co-distributed taxon pairs that occur in the dry forests of the Tumbes and Marañón Valley of northwestern South America show concordant patterns and modes of diversification. We employed a genome reduction technique, double-digest restriction site-associated DNA sequencing, and obtained 4407-7186 genomewide SNPs. We estimated demographic history in each taxon pair and inferred that all pairs had the same best-fit demographic model: isolation with asymmetric gene flow from the Tumbes into the Marañón Valley, suggesting a common diversification mode. Overall, we also observed congruence in effective population size (N ) patterns where ancestral N were 2.9-11.0× larger than present-day Marañón Valley populations and 0.3-2.0× larger than Tumbesian populations. Present-day Marañón Valley N was smaller than Tumbes. In contrast, we found simultaneous population isolation due to a single event to be unlikely as taxon pairs diverged over an extended period of time (0.1-2.9 Ma) with multiple nonoverlapping divergence periods. Our results show that even when populations of codistributed species asynchronously diverge, the mode of their differentiation can remain conserved over millions of years. Divergence by allopatric isolation due to barrier formation does not explain the mode of differentiation between these two bird assemblages; rather, migration of individuals occurred before and after geographic isolation.

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“…While physiological adaptation to abiotic factors undoubtedly impacts distributions of tropical montane birds in some cases (e.g. DuBay & Witt, ; see also adaptation to hypoxia at very high elevations; e.g. Cheviron & Brumfield, ; McCracken et al ., ), I did not find support for the fundamental physiological niche hypothesis as applied to cold range limits of New Guinean montane birds.…”

Section: Discussionmentioning

confidence: 99%

Thermal tolerances to cold do not predict upper elevational limits in New Guinean montane birds

Freeman

2015

Diversity and Distributions

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Aim To test predictions of the ‘fundamental physiological niche’ hypothesis that thermal tolerances are tightly correlated with upper elevational limits in New Guinean montane birds. Location New Guinea. Methods I combined previously published data describing New Guinean montane birds’ (1) metabolic responses to temperature, (2) elevational distributions and (3) recent upslope shifts, with an empirically measured lapse rate (temperature–elevation regression) to test two predictions of the fundamental physiological niche hypothesis – that species’ thermal tolerances to cold temperatures, measured as lower critical temperatures (LCTs) and thermal conductances, are correlated with their upper elevational limits (n = 24 species), and that species’ thermal mismatches (the difference between the mean temperatures species experience at their upper elevation limits and their LCTs) predict the magnitude of recent warming‐associated upslope shifts (n = 11 species). Results Species’ LCTs and thermal conductances were not correlated with the ambient temperatures they experience at their upper elevational limits (cold range limit), and species’ thermal mismatches were not related to the magnitude of recent upslope shifts at their upper elevational limits. Main Conclusions My results do not support the fundamental physiological niche hypothesis and suggest New Guinean montane birds’ upper elevational limits are unlikely to be set by the direct influence of temperature on adult birds’ thermal tolerances. I also found no evidence that warming‐associated upslope shifts in this avifauna are related to species’ thermal physiology. While this result is based on a small sample size, it is consistent with the hypothesis that recent upslope shifts result from biotic factors indirectly related to temperature.

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Differential high‐altitude adaptation and restricted gene flow across a mid‐elevation hybrid zone in Andean tit‐tyrant flycatchers

Cited by 57 publications

References 88 publications

Genotype‐environment associations support a mosaic hybrid zone between two tidal marsh birds

Genotype‐environment associations support a mosaic hybrid zone between two tidal marsh birds

Isolation with asymmetric gene flow during the nonsynchronous divergence of dry forest birds

Thermal tolerances to cold do not predict upper elevational limits in New Guinean montane birds

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