Digit ratios (2D:4D), secondary sexual characters and cell-mediated immunity in house sparrows <Emphasis Type="Italic">Passer domesticus</Emphasis> |
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Authors: | Carlos Navarro Florentino de Lope Anders Pape Møller |
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Institution: | (1) Departamento de Biología Animal, Universidad de Extremadura, 06071 Badajoz, Spain;(2) Laboratoire de Parasitologie Evolutive, CNRS UMR 7103, Université Pierre et Marie Curie, Bat. A, 7ème étage, 7 quai St. Bernard, Case 237, 75252 Paris Cedex 05, France;(3) Dept. Ecologia Funcional y Evolutiva, Estación Experimental de Zonas Aridas (CSIC), c/ General Segura, 1, E-04001 Almeria, Spain |
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Abstract: | Homeobox genes regulate development of digits, and it has been suggested that the ratio of length of second to length of fourth
digit reflects such genetic effects in a sex-specific manner. We show that digit ratios in the sexually dichromatic house
sparrow Passer domesticus differ between sexes, with males having higher ratios than females, and that individuals produce consistent ratios on the
two feet. If Homeobox or other genes had pleiotropic effects on development of digits, behavior, and physiology of males and
females, we would expect secondary sexual characters and immunity to be related to digit ratio in a sex-specific manner. The
size of the visible part of the black badge in February (a secondary sexual character), but not total badge size, was positively
correlated with digit ratios, suggesting that males with more male-like digit ratios had larger visible badges. Because of
sex-specific effects of development on secondary sexual characters and immunity, we predicted sex-specific differences in
immune response to be related to digit ratio. House sparrows with large digit ratios had weaker T cell-mediated immune response
than individuals with small digit ratios, particularly in females, implying that females with more male-like digit ratios
had weak immune responses. These findings are consistent with the hypothesis that early development, as reflected by digit
ratios, and genetics affect the expression of adult characters that are supposedly strongly contributing to fitness. |
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Keywords: | Development Homeobox genes Immunity Sexual selection |
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