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Spatial and temporal variation in morphology in Australian whistlers and shrike-thrushes: is climate change causing larger appendages?

journal contribution
posted on 2020-05-01, 00:00 authored by I R Onley, J L Gardner, Matthew SymondsMatthew Symonds
Allen's rule is an ecogeographical pattern whereby the size of appendages of animals increases relative to body size in warmer climates in order to facilitate heat exchange and thermoregulation. Allen's rule predicts that one consequence of a warming climate would be an increase in the relative size of appendages, and evidence from other bird species suggests that this might be occurring. Using measurements from museum specimens, we determined whether spatio-temporal variation in bills and legs of Australian Pachycephalidae species exhibits within-species trends consistent with Allen's rule and increases in temperature attributable to climatic warming. We conducted regression model analyses relating appendage size to spatio-temporal variables, while controlling for body size. The relative bill size in four of the eight species was negatively associated with latitude. Tarsus length showed no significant trends consistent with Allen's rule. No significant increases in appendage size were found over time. Although bill size in some species was positively correlated with warmer temperatures, the evidence was not substantial enough to suggest a morphological response to climatic warming. This study suggests that climate change is not currently driving adaptive change towards larger appendages in these species. We suggest that other adaptive mechanisms might be taking place.

History

Journal

Biological journal of the Linnean Society

Volume

130

Issue

1

Pagination

101 - 113

Publisher

Oxford University Press

Location

Oxford, Eng.

ISSN

0024-4066

eISSN

1095-8312

Language

eng

Publication classification

C Journal article; C1 Refereed article in a scholarly journal