Presentation Detail

Evolutionary Ecology

DuBay, Shane [1], Witt, Christopher [2].

Differential high-altitude adaptation and limited gene flow across a mid-elevation hybrid zone in Andean tit-tyrant flycatchers (Aves: Tyrannidae).

The Andes are a global hotspot of biological diversity that is characterized by dramatic elevational shifts in community composition and a preponderance of recently evolved species. Animal habitats in the Andes span a ~5000 m elevational gradient, encompassing a tremendous range of atmospheric conditions that pose challenges for respiration, thermoregulation, and water balance in endothermic vertebrates. Few studies address the extent to which this elevational gradient influences speciation or facilitates high rates of species turnover. We report a previously unknown hybrid zone between recently diverged flycatchers (Aves: Tyrannidae) with partially overlapping elevational ranges. The southern Anairetes reguloides has a broad elevational range from 0-4200 m, while the northern Anairetes nigrocristatus is restricted to elevations above 2000 m. The two taxa are largely allopatric, but where they come into contact in central Peru we found hybrids at elevations between ~3100-3800 m, with A. nigrocristatus above this elevation and A. reguloides below. We analyzed variation in hematology, heart mass, morphometrics, plumage, and one mitochondrial and three nuclear loci across an elevational transect encompassing the hybrid zone. The hybrid zone was structured as a steep cline, with little evidence of gene flow away from the two central localities of the transect. Relative heart mass and hemoglobin concentration increased strikingly with elevation and the proportion of genetic input from A. reguloides, suggesting that the latter species is not genetically adapted to high altitudes and experiences physiological stress in cold, hypoxic environments. Considering the high-altitude ancestor of the clade, A. reguloides appears to be secondarily adapted to low-altitude. These results suggest a physiological basis for elevational replacement, whereby differential adaptation to altitude maintains the distinctness of incipient species by stable parapatry along an elevational contour.

1 - University of Chicago, Committee on Evolutionary Biology, 1025 E. 57th Street, Culver Hall 402, Chicago, IL, 60637, USA
2 - University of New Mexico, Department of Biology , 167 Castetter Hall MSC03 2020, 1 University of New Mexico, Albuquerque, NM, 87131, USA

Keywords:
local adaptation
elevational replacement
elevational gradients
hybridization
hemoglobin
Speciation.

Presentation Type: Regular Oral Presentation
Session: 6
Location: Alpine C/Snowbird Center
Date: Saturday, June 22nd, 2013
Time: 9:00 AM
Number: 6003
Abstract ID:93
Candidate for Awards:W.D. Hamilton Award for Outstanding Student Presentation