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Testes mass in megachiropteran bats varies in accordance with sperm competition theory 总被引:4,自引:0,他引:4
D. J. Hosken 《Behavioral ecology and sociobiology》1998,44(3):169-177
Sperm competition is a widespread phenomenon influencing a range of characters, including investment in gonadal tissue. Conspecific
proximity is one factor which can influence the risk of sperm competition and hence testicular investment, and decreased confidence
of paternity may be one cost of group living. Aspects of female biology may also influence spermatogenic investment and sperm
morphology. This study examines the associations between relative testes mass and roost-group size across 17 species of Megachiroptera.
Associations between breeding season duration and investment in spermatogenesis are also examined, as are associations between
female reproductive tract dimensions and testes mass and dimensions of spermatozoa across all bats. Relative testes mass was
significantly positively associated with roost-group size at a species level and after appropriate phylogenetic control (pairwise
comparisons and comparison of independent contrasts). There were no significant relationships between breeding season duration
and relative testes mass. Across all bats, neither testes mass nor sperm length were significantly related to dimensions of
the female tract. The results are discussed in the context of sperm competition.
Received: 7 January 1998 / Accepted after revision: 8 August 1998 相似文献
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Oliver Schülke Peter M. Kappeler Hans Zischler 《Behavioral ecology and sociobiology》2004,55(3):293-301
Sperm competition will be the inevitable consequence of polyandrous mating behavior if two or more males inseminate a single female. It has been demonstrated for a wide variety of animals that males adapt to this situation behaviorally, physiologically and morphologically, e.g. by evolving relatively large testes size to produce more sperm. All pair-living primates investigated so far were found to have relatively small testes, suggesting a monandrous mating system. We investigated the relationship between extra-pair paternity (EPP) rate as a measure of sperm competition intensity and relative testes size in a pair-living primate, the fork-marked lemur (Phaner furcifer). Paternity exclusion analyses for seven offspring using six polymorphic DNA-microsatellite markers suggested a high EPP rate. Female nocturnal travel distances were longer during the mating season, suggesting that females take an active role in achieving extra-pair copulations (EPCs). Surprisingly, fork-marked lemur testes size was relatively small compared to 23 other lemuroid primates, a result that is in contrast to predictions of sperm competition theory. Neither possible behavioral and morphological adaptations to an alternative paternity guard (i.e. mate guarding), nor sampling biases, phylogenetic constraints, and population density effects explain the absence of large testes in a species with high EPP, a phenomenon also known from birds with moderate to low EPP rates. We conclude that more data are needed on the frequency of EPCs, the timing of in-pair and extra-pair copulations, as well as the role of female choice, to explain why males of some species apparently do not adapt to sperm competition.Communicated by S. Alberts 相似文献
3.
Peter M. Kappeler 《Behavioral ecology and sociobiology》1997,41(2):115-127
The primates of Madagascar (Lemuriformes) deviate from fundamental predictions of sexual selection theory in that polygynous
species lack sexual dimorphism, have even adult sex ratios and often live in female-dominated societies. It has been hypothesized
that intrasexual selection in these species is either reduced or primarily focused on traits related to scramble competition.
The goal of this study was to examine these hypotheses by studying the mating system of a solitary nocturnal species, Mirzacoquereli. During a 4-year field study in western Madagascar, I captured and followed 88 individually marked animals. I found that
adult males were significantly larger than females, providing the first evidence for sexual size dimorphism in lemurs. In
addition, the adult sex ratio was biased in favour of females in 3 out of 4 years. There was no significant sex difference
in canine size, however. Males showed pronounced seasonal variation in testis size with a 5-fold increase before and during
the short annual mating season. During the mating season, males had more injuries than females and more than quadrupled their
home ranges, overlapping with those of more than ten females, but also with about the same number of rivals. Only about one
social interaction per 10 h of observation was recorded, but none of them were matings. Together, these results indicate that
these solitary lemurs are clearly subject to intrasexual selection and that male-male competition is primarily, but not exclusively,
of the scramble type. In addition, they suggest that the above-mentioned idiosyncracies may be limited to group-living lemurs,
that social systems of solitary primates are more diverse than previously thought, and that the temporal distribution of receptive
females is responsible for this particular male mating strategy.
Received: 11 January 1997 / Accepted after revision: 18 April 1997 相似文献
4.
M. Pyron 《Behavioral ecology and sociobiology》2000,48(2):132-136
Most comparative analyses of relative testes mass find that testes are larger in species in which more sperm competition is
predicted (multiple males mate with individual females). I tested for differences in adjusted testes mass (for body mass)
by spawning mode and by sexual size dimorphism in a comparative analysis of 37 minnow species. No significant differences
were found for testes mass by spawning mode or sexual size dimorphism. These results imply a lack of response to selection
on testes size from sperm competition in minnow species. Possible explanations for the lack of the expected relationship between
testes mass and mating systems in minnows are presented.
Received: 8 November 1999 / Received in revised form: 27 January 2000 / Accepted: 13 February 2000 相似文献
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