Isolation by environment in White-breasted Nuthatches (Sitta carolinensis) of the Madrean Archipelago sky islands: a landscape genomics approach

ABSTRACTThe interplay between environmental attributes and evolutionary processes can provide valuable insights into how biodiversity is generated, partitioned, and distributed. This study investigates the role of spatial, environmental, and historical factors that could potentially drive diversification and shape genetic variation in Malaysian torrent frogs. Torrent frogs are ecologically conserved, and we hypothesize that this could impose tight constraints on dispersal routes, gene flow, and consequently genetic structure. Moreover, levels of gene flow were shown to vary among populations from separate mountain ranges, indicating that genetic differentiation could be influenced by landscape features. Using genome-wide SNPs in conjunction with landscape variables derived from GIS, we performed distance-based redundancy analyses and variance partitioning to disentangle the effects of isolation-by-distance (IBD), isolation-by-environment (IBE), and isolation-by-colonization (IBC). Our results demonstrated that IBE, contributed minimally to genetic variation. Intraspecific population structure can be largely attributed to IBD, whereas interspecific diversification was primarily driven by IBC. We also detected two distinct population bottlenecks, indicating that speciation events were likely driven by vicariance or founder events.

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A genomic investigation of the putative contact zone between divergent Brown Creeper (Certhia americana) lineages: chromosomal patterns of genetic differentiation

Genome ◽

10.1139/gen-2015-0093 ◽

2016 ◽

Vol 59 (2) ◽

pp. 115-125 ◽

Cited By ~ 7

Author(s):

Joseph D. Manthey ◽

Mark B. Robbins ◽

Robert G. Moyle

Keyword(s):

Gene Flow ◽

Genetic Differentiation ◽

Contact Zone ◽

Sex Chromosome ◽

Random Mating ◽

Sky Islands ◽

Recombination Rates ◽

Isolated Populations ◽

Brown Creeper ◽

Madrean Archipelago

Sky islands, or montane forest separated by different lowland habitats, are highly fragmented regions that potentially limit gene flow between isolated populations. In the sky islands of the Madrean Archipelago (Arizona, USA), various taxa display different phylogeographic patterns, from unrestricted gene flow among sky islands to complex patterns with multiple distinct lineages. Using genomic-level approaches allows the investigation of differential patterns of gene flow, selection, and genetic differentiation among chromosomes and specific genomic regions between sky island populations. Here, we used thousands of SNPs to investigate the putative contact zone of divergent Brown Creeper (Certhia americana) lineages in the Madrean Archipelago sky islands. We found the two lineages to be completely allopatric (during the breeding season) with a lack of hybridization and gene flow between lineages and no genetic structure among sky islands within lineages. Additionally, the two lineages inhabit different climatic and ecosystem conditions and have many local primary song dialects in the southern Arizona mountain ranges. We identified a positive relationship between genetic differentiation and chromosome size, but the sex chromosome (Z) was not found to be an outlier. Differential patterns of genetic differentiation per chromosome may be explained by genetic drift—possibly in conjunction with non-random mating and non-random gene flow—due to variance in recombination rates among chromosomes.

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