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8 March 2021 Morphological Differences in the Island-Endemic Hawaiian Subspecies of the Common Gallinule Gallinula galeata
Charles B. Van Rees, M. Alejandra Muñoz, Sophia C. Cooke, J. Michael Reed
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Abstract

The study of island subspecies provides excellent “natural experiments” for examining the impacts of different selective regimes on animal taxa. We examined the morphological differences between the Hawaiian and continental North American subspecies of the Common Gallinule (Gallinula galeata sandvicensis and G. g. cachinnans, respectively), for which the existing literature is both scant and contradictory. More than 200 live gallinules and >100 museum specimens were measured, and a meta-analysis of literature values on North American Common Gallinules was conducted to quantitatively assess differences in wing chord, culmen and tarsus length, and body mass between these subspecies. Hawaiian Common Gallinules had smaller wing chords (–2.5 to –4.0%), larger culmen (+4.5 to +7.0%) and tarsi (+5.5 to +23.0%), and slightly larger body masses (∼+4.0%) than their mainland conspecifics. This is likely due to several factors including reduced predation pressure, shorter dispersal distances, nonmigratory behavior, and sedentary lifestyles associated with ecological differences between the Hawaiian Islands and the North American mainland. We also introduce the novel hypothesis that intra- and interspecific agonistic interactions due to habitat limitation are an additional selective force in driving these morphological changes.

© 2020 by University of Hawai‘i Press. All rights reserved.
Charles B. Van Rees, M. Alejandra Muñoz, Sophia C. Cooke, and J. Michael Reed "Morphological Differences in the Island-Endemic Hawaiian Subspecies of the Common Gallinule Gallinula galeata," Pacific Science 74(4), 345-364, (8 March 2021). https://doi.org/10.2984/74.4.3
Accepted: 7 August 2020; Published: 8 March 2021
JOURNAL ARTICLE
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KEYWORDS
body mass
culmen
flightlessness
moorhen
Morphometrics
rallidae
tarsus
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