Physiological adaptation along environmental gradients and replicated hybrid zone structure in swordtails (Teleostei:<i>Xiphophorus</i>)

Culumber, Zachary W.; Shepard, Donald B.; Coleman, Seth W.; Rosenthal, Gil G.; Tobler, Michael

doi:10.1111/j.1420-9101.2012.02562.x

Cited by 75 publications

(106 citation statements)

References 106 publications

(209 reference statements)

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“…Rather than emphasizing the uncertain threat posed by the presence of hybrid individuals, the focus should be on understanding those environmental and anthropogenic factors related to the position, structure, and dynamics of hybrid zones (Culumber et al. 2012). …”

Section: Resultsmentioning

confidence: 99%

Patterns of hybridization among cutthroat trout and rainbow trout in northern Rocky Mountain streams

McKelvey

Young

Wilcox

et al. 2016

Ecology and Evolution

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Introgressive hybridization between native and introduced species is a growing conservation concern. For native cutthroat trout and introduced rainbow trout in western North America, this process is thought to lead to the formation of hybrid swarms and the loss of monophyletic evolutionary lineages. Previous studies of this phenomenon, however, indicated that hybrid swarms were rare except when native and introduced forms of cutthroat trout co‐occurred. We used a panel of 86 diagnostic, single nucleotide polymorphisms to evaluate the genetic composition of 3865 fish captured in 188 locations on 129 streams distributed across western Montana and northern Idaho. Although introgression was common and only 37% of the sites were occupied solely by parental westslope cutthroat trout, levels of hybridization were generally low. Of the 188 sites sampled, 73% contained ≤5% rainbow trout alleles and 58% had ≤1% rainbow trout alleles. Overall, 72% of specimens were nonadmixed westslope cutthroat trout, and an additional 3.5% were nonadmixed rainbow trout. Samples from seven sites met our criteria for hybrid swarms, that is, an absence of nonadmixed individuals and a random distribution of alleles within the sample; most (6/7) were associated with introgression by Yellowstone cutthroat trout. In streams with multiple sites, upstream locations exhibited less introgression than downstream locations. We conclude that although the widespread introduction of nonnative trout within the historical range of westslope cutthroat trout has increased the incidence of introgression, sites containing nonadmixed populations of this taxon are common and broadly distributed.

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Section: Resultsmentioning

confidence: 99%

Patterns of hybridization among cutthroat trout and rainbow trout in northern Rocky Mountain streams

McKelvey

Young

Wilcox

et al. 2016

Ecology and Evolution

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“…Recent studies have found increasing evidence for spatial structuring across numerous ecological gradients, including temperature gradients (Culumber et al. 2012), vegetation/substrate gradients (Shurtliff et al. 2013), bioclimatic gradients (Tarroso 2014), and elevational gradients (DuBay and Witt 2014).…”

Section: Discussionmentioning

confidence: 99%

“…Hybrid zones often occur along ecological gradients, as transitional habitats may facilitate contact between species occupying different ecological niches (Culumber et al. 2012). In cases of environment‐dependent selection, the spatial distribution of individuals within a hybrid zone should correlate strongly with their genotypes (Arnold 1997; Johnston et al.…”

Section: Introductionmentioning

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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“…As a result, a common pattern is that warmer, low-elevation stream communities are broadly and repeatedly invaded (14, 17) whereas colder, high-elevation streams are less altered and often serve as refugia for native species tolerant of cold temperatures (18,19). The same is true regarding more subtle genetic invasions and introgressive hybridization, because many genetically pure populations exist in headwater streams where climatic conditions limit the upstream expansion of hybrid zones (20,21).The ubiquity of isolated populations of many species in mountain headwaters (14, 18, 19) suggests they have existed for extended periods, but climate-induced stream warming (22, 23) raises legitimate concerns about their future persistence. Concerns are heightened by evidence of faster air temperature increases at high elevations (24), and by model predictions that streams in snowmelt-dominated landscapes will be highly sensitive (i.e., large stream Δ°C/air Δ°C) to air temperature increases (25)(26)(27).…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Slow climate velocities of mountain streams portend their role as refugia for cold-water biodiversity

Isaak

Young

Luce

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

203

236

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The imminent demise of montane species is a recurrent theme in the climate change literature, particularly for aquatic species that are constrained to networks and elevational rather than latitudinal retreat as temperatures increase. Predictions of widespread species losses, however, have yet to be fulfilled despite decades of climate change, suggesting that trends are much weaker than anticipated and may be too subtle for detection given the widespread use of sparse water temperature datasets or imprecise surrogates like elevation and air temperature. Through application of large water-temperature databases evaluated for sensitivity to historical air-temperature variability and computationally interpolated to provide high-resolution thermal habitat information for a 222,000-km network, we estimate a less dire thermal plight for cold-water species within mountains of the northwestern United States. Stream warming rates and climate velocities were both relatively low for 1968-2011 (average warming rate = 0.101°C/ decade; median velocity = 1.07 km/decade) when air temperatures warmed at 0.21°C/decade. Many cold-water vertebrate species occurred in a subset of the network characterized by low climate velocities, and three native species of conservation concern occurred in extremely cold, slow velocity environments (0.33-0.48 km/decade). Examination of aggressive warming scenarios indicated that although network climate velocities could increase, they remain low in headwaters because of strong local temperature gradients associated with topographic controls. Better information about changing hydrology and disturbance regimes is needed to complement these results, but rather than being climatic cul-de-sacs, many mountain streams appear poised to be redoubts for cold-water biodiversity this century.climate refugia | climate velocity | biodiversity | fish | network M ountain landscapes constitute 12% of the Earth's land surface (1) and have long served as sanctuaries for certain species by restricting human incursions and juxtaposing diverse environments (2). Mountains also host a suite of endemic species, many of which are perceived to be condemned to extinction as their habitats contract or disappear as a result of climate change-related temperature increases, environmental stochasticity, and nonnative species invasions (3-5). A substantial literature, to which we have contributed, has developed in previous decades suggesting a similar fate for cold-water fishes and other aquatic taxa in montane environments (6-8), but it rests largely on predictions about temperature increases and untested assumptions about the relationship between air temperature and water temperature. In particular, previous studies have failed to recognize that the highest and coldest streams are relatively insensitive to air temperature fluctuations (9, 10), and that the morphologies of many mountain ranges and their stream networks may mediate climate warming such that shifts in thermal habitat are small (2, 11).Dense stream networks drain moun...

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Physiological adaptation along environmental gradients and replicated hybrid zone structure in swordtails (Teleostei:Xiphophorus)

Cited by 75 publications

References 106 publications

Patterns of hybridization among cutthroat trout and rainbow trout in northern Rocky Mountain streams

Patterns of hybridization among cutthroat trout and rainbow trout in northern Rocky Mountain streams

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

Slow climate velocities of mountain streams portend their role as refugia for cold-water biodiversity

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