The Rocky Mountains as a dispersal barrier between barn owl (Tyto alba) populations in North America

Abstract

Aim: Geological barriers within a species range play a key role in shaping patterns of genetic variation by restricting gene flow. Mountain ranges are particularly imposing barriers responsible for creating genetic differentiation across multiple taxa, from small amphibians to large mammals and birds. Here, we examined the population structure of North American barn owls (Tyto alba) and investigated whether the Rocky Mountains influence gene flow and dispersal at the continental scale.Location: Continental North America. Methods:We collected 292 museum samples covering the species range, genotyped them at 20 microsatellite markers and sequenced 410 bp of the mitochondrial gene ND6. Population and landscape genetics tools were used to study range-wide patterns of structure and identify gene flow barriers. Ring recapture data were also analysed to investigate individual movement patterns and frequency of exchanges between both sides of the Rocky Mountains.Results: We found faint overall genetic structure, which is consistent with barn owl's high mobility across its continuous range. Nonetheless, we identified two distinct genetic groups on the western and eastern regions of the Rocky Mountains with a likely contact point through the narrow southern pass between them and the Sierra Madre Occidental in Mexico. Accordingly, most recaptured barn owls remain on the same side of the mountains. The Rockies appear to significantly isolate the populations in the west, which, as a consequence, display lower genetic diversity than their counterparts to the east.Main conclusions: The Rocky Mountains appear to constrain barn owl dispersal and gene flow. Our study supports the hypothesis that regional landscape barriers can shape gene flow and population structure even in highly mobile organisms. K E Y W O R D S barn owl,

Geographical variation in bill size provides evidence for Allen’s rule in a cosmopolitan raptor

“…Very little information has been collected about the altitudinal range potentially exploited by barn owls. Although it has been suggested that at high latitudes it prefers to live at relative low elevations and that high mountain ranges might represent ecological barriers that limit its dispersal (e.g., the Rocky Mountains; Machado, Clément, Uva, Goudet, & Roulin, ), it is also well known that this taxon inhabits many high mountainous areas, especially valleys (e.g., in the New Guinean Central Range, in the Andes, in the Alps and in the Himalayas), and uplands (e.g., in the East African Highlands), ≤ 3,000 m a.s.l. (see also Supporting Information Figure S1).…”

Unexpected post-glacial colonisation route explains the white colour of barn owls (Tyto alba) from the British Isles

“…Table 3). This suggests that the Pyrenees are permeable to barn owl migration, unlike other higher and larger mountain ranges (Machado, Clément, Uva, Goudet, & Roulin, 2018). In central Europe, barn owl populations appear to be remarkably homogenous genetically, despite covering a large geographical and colour range (Figure 1, Sup.…”

Implications of genetic heterogeneity for plant translocation during ecological restoration

“…The Continental Divide was associated with higher genetic differentiation between Mountain mahogany populations, especially in central Colorado, where the Continental Divide is at high altitudes. Several studies have shown that the Continental Divide is a strong barrier to gene flow (Machado et al., 2018; Schield et al., 2018). However, to date, no published study has documented this in plant species.…”