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- Laugen, A. T., et al.
(författare)
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Sperm competition in yellow dung flies: No consistent effect of sperm size
- 2022
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X .- 1420-9101. ; 35:10, s. 1309-1318
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Tidskriftsartikel (refereegranskat)abstract
- The male competition for fertilization that results from female multiple mating promotes the evolution of increased sperm numbers and can impact sperm morphology, with theory predicting that longer sperm can at times be advantageous during sperm competition. If so, males with longer sperm should sire more offspring than competitors with shorter sperm. Few studies have directly tested this prediction, and findings are inconsistent. Here we assessed whether longer sperm provide a competitive advantage in the yellow dung fly (Scathophaga stercoraria; Diptera: Scathophagidae). Initially, we let brothers with different temperature-mediated mean sperm lengths compete - thus minimizing confounding effects of genetic background - and found no clear advantage of longer sperm. We then used flies from lines subjected to bidirectional selection on phenoloxidase activity that had shown correlated evolutionary responses in sperm and female spermathecal duct lengths. This experiment also yielded no main effect of sperm size on siring success. Instead, there was a trend for a shorter-sperm advantage, but only when competing in females with longer spermathecal ducts. Our data corroborated many previously reported findings (last-male precedence, effects of copula duration and body size), suggesting our failure to find sperm size effects is not inherently due to our experimental protocols. We conclude that longer sperm are not competitively superior in yellow dung flies under most circumstances, and that, consistent with previous work, in this species competitive fertilization success is primarily determined by the relative numbers of sperm competing.
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| 2. |
- Laugen, A T, et al.
(författare)
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Do common frogs (Rana temporaria) follow Bergmann's rule?
- 2005
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Ingår i: Evolutionary Ecology Research. - 1522-0613 .- 1937-3791. ; 7:5, s. 717-731
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Tidskriftsartikel (refereegranskat)abstract
- Questions: Does intraspecific extension of Bergmann's rule - larger size within a species in cooler areas - hold true for ectotherms in general, and for the common frog (Rana temporaria) in particular? What is the relative importance of genetic and environmental factors (i.e. direct environmental induction) in determining latitudinal patterns of body size variation in common frogs?Methods: We tested for a positive association between mean body size and latitude in common frogs (Rana temporaria) across a 1600 km long latitudinal gradient in Scandinavia both for wild-collected adults and laboratory-reared metamorphs.Results: In adults, the mean body size increased from south to mid-latitudes, and declined thereafter. This occurred despite the fact that the mean age of adult frogs increased with increasing latitude, and age and body size were positively correlated. The latitudinal pattern of body size variation in metamorphs reared in a common garden experiment was similar to that observed among wild-caught adults.Conclusions: The results suggest that the concave pattern of body size variation across the latitudinal cline may be at least partly genetically determined, and that although there is considerable geographic variation in mean body size of R. temporaria, this variation does not conform with Bergmann's rule.
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