Differential high‐altitude adaptation and restricted gene flow across a mid‐elevation hybrid zone in A ndean tit‐tyrant flycatchers
The tropical Andes are a global hotspot of avian diversity that is characterized by dramatic elevational shifts in community composition and a preponderance of recently evolved species. Bird habitats in the Andes span a nearly twofold range of atmospheric pressure that poses challenges for respirati...
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Veröffentlicht in: | Molecular ecology 2014-07, Vol.23 (14), p.3551-3565 |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | The tropical Andes are a global hotspot of avian diversity that is characterized by dramatic elevational shifts in community composition and a preponderance of recently evolved species. Bird habitats in the Andes span a nearly twofold range of atmospheric pressure that poses challenges for respiration, thermoregulation, water balance and powered flight, but the extent to which physiological constraints limit species' elevational distributions is poorly understood. We report a previously unknown hybrid zone between recently diverged flycatchers (
A
ves,
T
yrannidae) with partially overlapping elevational ranges. The southern
Anairetes reguloides
has a broad elevational range (0–4200 m), while the northern
Anairetes nigrocristatus
is restricted to high elevations (>2200 m). We found hybrids in central Peru at elevations between ~3100 and 3800 m, with
A
. nigrocristatus
above this elevation and
A
. reguloides
below. We analysed variation in haematology, heart mass, morphometrics, plumage and one mitochondrial and three nuclear loci across an elevational transect that encompasses the hybrid zone. Phenotypic traits and genetic markers all showed steep clines across the hybrid zone. Haemoglobin concentration, haematocrit, mean cellular haemoglobin concentration and relative heart mass each increased at altitude more strongly in
A
. reguloides
than in
A
. nigrocristatus
. These findings suggest that
A
. nigrocristatus
is more resistant than
A
. reguloides
to high‐altitude hypoxic respiratory stress. Considering that the ancestor of the genus is suggested to have been restricted to high elevations,
A
. reguloides
may be secondarily adapted to low altitude. We conclude that differential respiratory specialization on atmospheric pressure combined with competitive exclusion maintains replacement along an elevational contour, despite interbreeding. |
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ISSN: | 0962-1083 1365-294X |
DOI: | 10.1111/mec.12836 |