Shifts in bilateral asymmetry within a distribution range: The case of the chukar partridge

Kark, S (2001) Shifts in bilateral asymmetry within a distribution range: The case of the chukar partridge. Evolution, 55 10: 2088-2096.

Author Kark, S
Title Shifts in bilateral asymmetry within a distribution range: The case of the chukar partridge
Journal name Evolution   Check publisher's open access policy
ISSN 0014-3820
Publication date 2001-10-01
Year available 2001
Sub-type Article (original research)
Open Access Status Not yet assessed
Volume 55
Issue 10
Start page 2088
End page 2096
Total pages 9
Place of publication LAWRENCE
Language eng
Abstract Three major types of bilateral asymmetry (fluctuating asymmetry, directional asymmetry, and antisymmetry) have long been recognized in the literature. Little, however, is known about transitions between asymmetry types, especially in natural populations. It is often assumed that directional asymmetry and antisymmetry have a larger Genetic basis than fluctuating asymmetry. This leads many scientists to exclude traits or populations showing either directional asymmetry or antisymmetry from developmental instability studies, focusing attention on fluctuating asymmetry alone. This procedure may bias the findings and thus our understanding of patterns of bilateral asymmetry and the factors influencing it. To examine changes in bilateral asymmetry across the distribution range of a species, I studied the length of the third toe in I I chukar partridge (Alectoris chukar) populations across a steep environmental gradient of 320 km within the species' range in Israel. This trait was selected due to its adaptive value in the chukar, a species that spends much of its activity walking, and due to its high measurement repeatability. Moving front the core toward the very extreme periphery of the range, the following four trends are detected: ( I) the expression of the directional asymmetry component significantly increases; (2) the frequency of symmetrical individuals in the population significantly decreases, with a sharp decline at the steepest part of the climatic and environmental gradient studied, within the Mediterranean-desert ecotone; (3) mean asymmetry levels, as estimated using the unsigned difference between the right and left toe, significantly increases; and (4) the range of asymmetry increases such that the most asymmetrical individuals originate from the very edge of the range. These findings provide primary evidence that substantial shifts in asymmetry may occur across short geographical distances within a species' distribution range. They show a continuum between asymmetry types and support the notion that all three types of asymmetry can reflect developmental instability. Further studies of developmental instability should be designed so that they enable detection of transitions between asymmetry types across natural populations. Such a procedure may partly resolve some of the contradictions seen in the literature regarding the relationship between bilateral asymmetry and environmental stress.
Keyword Alectoris chukar
developmental instability
directional asymmetry
distribution range
fluctuating asymmetry
Fragmented Afrotropical Forest
Fluctuating Asymmetry
Developmental Stability
Directional Asymmetry
Habitat Disturbance
Mixture Analysis
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Unknown

Document type: Journal Article
Sub-type: Article (original research)
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