Genetic evidence for recent range fragmentation and severely restricted dispersal in the critically endangered Sierra Madre Sparrow, Xenospiza baileyi

Abstract

Assessing patterns of genetic structure and diversity of threatened species has become an essential tool for determining conservation status and designing management strategies. We examine the genetic structure of the Sierra Madre sparrow (Xenospiza baileyi), a species restricted to fragmented patches of subalpine bunchgrass in three small isolated areas of northwestern and central Mexico. Coding and non-coding regions of mtDNA (1,878 bp) from individuals of the only three known populations revealed the existence of a single major lineage, with closely related haplotypes being shared between populations across the range. The sharing of haplotypes between the distant northwest and central populations (*800 km) suggests a recent fragmentation of a formerly contiguous population. Despite a lack of large-scale phylogeographic structure, haplotype frequencies at local scales revealed significant genetic differentiation and high F ST values between all three remaining populations, even between localities separated by less than 12 km. These results suggest restricted gene flow and limited dispersal, likely due to the species' inability to cross areas of unsuitable habitat. On the basis of genetic interchange and ecological equivalence criteria, we recommend that the species be managed as a single unit, permitting the strengthening of the small population in the northwest with individuals from central Mexico, and/or the translocation of individuals to new areas of suitable habitat.

The role of immigration and local adaptation on fine‐scale genotypic and phenotypic population divergence in a less mobile passerine

“…In spite of their geographical proximity, the suboptimal habitat separating both populations could prevent dispersal between them or increase the energy expenditure and risk of predation as a result of having to travel through an unsuitable matrix (Harris & Reed, ; McRae, ; Smith & Batzli, ; Baguette & Van Dyck, ). Unfavourable or inhospitable habitats may restrict dispersal and lead to genetic differences between populations separated by short distances (Postma et al ., ; Oliveras de Ita et al ., ).…”

Speciation in mountain refugia: phylogeography and demographic history of the pine siskin and black‐capped siskin complex

“…In addition to S. p. perplexus , independent evolutionary lineages in this area have been documented in broad‐tailed hummingbirds Selasphorus platycercus (Malpica and Ornelas ), yellow‐rumped warblers Setophaga coronata (Milá et al , ), and yellow‐eyed juncos Junco phaeonotus (Milá et al ). Given the restricted size of this geographic region, the human pressures on its remaining natural habitats, and the increased extinction risk of high elevation taxa (Oliveras de Ita et al , White and Bennett ), the Guatemalan highlands and adjacent high‐elevation areas represent an important evolutionary refugium that should be the target of increased research and conservation.…”

New Locality of the endangered Sierra Madre Sparrow (Xenospiza Baileyi) from the State of Durango, Mexico, and recommendations for its conservation

“…This new locality here described in the state of Durango is only 64.5 km to the north of the other known Durango locality of Ejido Ojo de Agua El Cazador, so it is possible that birds from this site could move to this new locality with habitat available to reproduce. A recent genetic analysis found, that allopatric populations from the two known distribution ranges show the absence of significant phyleographic structure, which indicates the origin of SMPS had a single existing lineage, and a marked haplotypic differentiation among the populations as well that shows a high degree of isolation, mainly in the population of Durango (Oliveras de Ita et al, 2012). Limited gene flow owing to fragmented habitat and widely unconnected ranges suggest that the best management option would be to translocate SMSP from southern populations to the northern one in Durango (Oliveras de Ita et al, 2012).…”