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69 results for “Geographical divergence”

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Data from: Conspicuousness, color resemblance, and toxicity in geographically diverging mimicry: the pan-Amazonian frog Allobates femoralis

Predation risk is allegedly reduced in Batesian and Müllerian mimics, because their coloration resembles the conspicuous coloration of unpalatable prey. The efficacy of mimicry is thought to be affected by variation in the unpalatability of prey, the conspicuousness of the signals, and the visual system of predators that see them. Many frog species exhibit small colorful patches contrasting against an otherwise dark body. By measuring toxicity and color reflectance in a geographically variable frog species and the syntopic toxic species, we tested whether unpalatability was correlated with between-species color resemblance and whether resemblance was highest for the most conspicuous components of coloration pattern. Heterospecific resemblance in colorful patches was highest between species at the same locality but unrelated to concomitant variation in toxicity. Surprisingly, resemblance was lower for the conspicuous femoral patches compared to the inconspicuous dorsum. By building visual models, we further tested whether resemblance was affected by the visual system of model predators. As predicted, mimic-model resemblance was higher under the visual system of simulated predators compared to no visual system at all. Our results indicate that femoral patches are aposematic signals and support a role of mimicry in driving phenotypic divergence or mimetic radiation between localities.

opencc-zeroDec 2015View details →

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Data from: Resource stability and geographic isolation are associated with genome divergence in western Palearctic crossbills

While many conifers produce annually variable seed crops, serotinous species (which hold seeds in cones for multiple years) represent unusually stable food resources for seed predators. Such stability is conducive to residency and potentially population divergence of consumers as exemplified by the Cassia crossbill (Loxia sinesciuris) in North America. We used genotyping-by-sequencing to test whether three Mediterranean subspecies of common crossbills (L. curvirostra) associated with the serotinous Aleppo pine (Pinus halepensis) were more genetically distinct than European crossbills associated with non-serotinous conifers. We assembled a Cassia crossbill draft genome as a reference for mapping GBS reads, and as a first step towards a more contiguous genome assembly. We found clear patterns of genetic divergence for each of the P. halepensis-associated subspecies. Geographic isolation, as promoted by resource stability and residency, is associated with genetic divergence of two of these subspecies. However, geographic isolation cannot account for divergence of L. c. hispana. Instead, resource stability likely contributed to divergence by reducing dispersal and increasing resource competition that may limit breeding by immigrants. In contrast, we found no differentiation among common crossbills associated with less stable resources, and only slight differentiation between common crossbills and parrot crossbills (L. pytyopsittacus). The substantial morphological divergence between common and parrot crossbills has likely originated or been maintained by selection despite gene flow generated by spatiotemporal resource fluctuation. Our results indicate that phenological as well as morphological characteristics of conifers have influenced crossbill diversification, and suggest a possible link between resource stability and population divergence.

opencc-zeroDec 2017View details →

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Data from: The influence of geographic heterogeneity in predation pressure on mating signal divergence in an Amazonian frog species complex

Sexual section plays an important role in mating signal divergence, but geographic variation in ecological factors can also contribute to divergent signal evolution. We tested the hypothesis that geographic heterogeneity in predation causes divergent selection on advertisement call complexity within the Engystomops petersi frog species complex. We conducted predator phonotaxis experiments at two sites where female choice is consistent with call trait divergence. Engystomops at one site produces complex calls, while the closely related species at the other site produces simple calls. Bats approached complex calls more than simple calls at both sites, suggesting selection against complex calls. Moreover, bat predation pressure was greater at the site with simple calls, suggesting stronger selection against complex calls and potentially precluding evolution of complex calls at this site. Our results show that geographic variation in predation may play an important role in the evolution and maintenance of mating signal divergence.

opencc-zeroDec 2011View details →

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Data from: Genome divergence and diversification within a geographic mosaic of coevolution

Despite substantial interest in coevolution's role in diversification, examples of coevolution contributing to speciation have been elusive. Here, we build upon past studies that have shown both coevolution between South Hills crossbills and lodgepole pine (Pinus contorta), and high levels of reproductive isolation between South Hills crossbills and other ecotypes in the North American red crossbill (Loxia curvirostra) complex. We used genotyping by sequencing to generate population genomic data and applied phylogenetic and population genetic analyses to characterize the genetic structure within and among nine of the ecotypes. Although genome-wide divergence was slight between ecotypes (FST = 0.011–0.035), we found evidence of relative genetic differentiation (as measured by FST) between and genetic cohesiveness within many of them. As expected for nomadic and opportunistic breeders, we detected no evidence of isolation by distance. The one sedentary ecotype, the South Hills crossbill, was genetically most distinct because of elevated divergence at a small number of loci rather than pronounced overall genome-wide divergence. These findings suggest that mechanisms related to recent local coevolution between South Hills crossbills and lodgepole pine (e.g. strong resource-based density dependence limiting gene flow) have been associated with genome divergence in the face of gene flow. Our results further characterize a striking example of coevolution driving speciation within perhaps as little as 6000 years.

opencc-zeroDec 2015View details →

dryad28/100