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Cooperative breeding in groups of synchronously mating females and evolution of large testes to avoid sperm depletion in african striped mice


Schradin, C; Kinahan, A A; Pillay, N (2009). Cooperative breeding in groups of synchronously mating females and evolution of large testes to avoid sperm depletion in african striped mice. Biology of Reproduction, 81(1):111-117.

Abstract

Testis size has been related to the mating system of both vertebrates and invertebrates. These differences are regarded as adaptive responses to sperm competition in promiscuously mating species. However, not all variation in testis size can be explained by sperm competition. Here, we test the hypothesis that the evolution of large testes occurs when synchronously breeding females must be fertilized within a short period of time to avoid reproductive competition among the females. African striped mouse (Rhabdomys pumilio) males of a polygynous population with cooperative breeding and high risk of sperm depletion had testes and cauda epididymis twice as large as those of males of four different promiscuous populations with high risk of sperm competition. When paired with three females simultaneously in captivity, males of the polygynous population bred with three females within 8 days, leading to synchronous births in their harems, thereby potentially reducing the risk of infanticide. Males from the promiscuous population reproduced with only one or two females within 8 days, and births were not synchronous. We conclude that large testes are selected for in species with synchronously mating females, which is ultimately beneficial for the evolution of cooperative breeding.

Abstract

Testis size has been related to the mating system of both vertebrates and invertebrates. These differences are regarded as adaptive responses to sperm competition in promiscuously mating species. However, not all variation in testis size can be explained by sperm competition. Here, we test the hypothesis that the evolution of large testes occurs when synchronously breeding females must be fertilized within a short period of time to avoid reproductive competition among the females. African striped mouse (Rhabdomys pumilio) males of a polygynous population with cooperative breeding and high risk of sperm depletion had testes and cauda epididymis twice as large as those of males of four different promiscuous populations with high risk of sperm competition. When paired with three females simultaneously in captivity, males of the polygynous population bred with three females within 8 days, leading to synchronous births in their harems, thereby potentially reducing the risk of infanticide. Males from the promiscuous population reproduced with only one or two females within 8 days, and births were not synchronous. We conclude that large testes are selected for in species with synchronously mating females, which is ultimately beneficial for the evolution of cooperative breeding.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Uncontrolled Keywords:Rhabdomys; sperm competition; communal breeding; reproductive skew
Language:English
Date:1 July 2009
Deposited On:08 Jul 2009 16:07
Last Modified:06 Dec 2017 20:07
Publisher:Society for the Study of Reproduction
ISSN:0006-3363
Publisher DOI:https://doi.org/10.1095/biolreprod.108.075838
PubMed ID:19264699

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