Evidence for seasonal mate limitation in populations of an intertidal amphipod, Corophium volutator (Pallas) |
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Authors: | Mark R Forbes Dean G McCurdy Keiko Lui Selma I Mautner J Sherman Boates |
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Institution: | (1) Department of Biology, 209 Nesbitt Building, Carleton University, 1125 Colonel By Drive, Ottawa, ON, K1S 5B6, Canada;(2) Biology Department, Albion College, 611 East Porter Street, Albion, MI 49224, USA;(3) Nova Scotia Department of Natural Resources, 136 Exhibition Street, Kentville, NS, B4N 4E5, Canada |
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Abstract: | Potential rates of reproduction (PRR) differ between the sexes of many animal species. Adult sex ratios together with PRR
are expected to determine the operational sex ratio (OSR) defined as the ratio of fertilizable females to sexually active
males at any given time. OSR is expected to determine the degree to which one sex competes for another—the limiting sex. We
explored the potential for mate limitation in an intertidal amphipod, Corophium volutator (Pallas). Males have higher PRR than females, but males may be limiting because of extreme female-biased sex ratios observed
in this species. Consistent with this idea, late season females were less likely to be ovigerous and had smaller size-specific
clutches, both of which were associated with seasonal declines in availability of males of reproductive size. Seasonal changes
in ovigery could not be explained by seasonal changes across sites in other factors (e.g., female body size or phenology of
breeding). Smaller females were less likely to become ovigerous later in the season at three of four sites. Seasonal reductions
in clutch size also occurred among small females expected to be reproducing for their first time. In complimentary laboratory
experiments, reduced likelihood of ovigery and reduced fecundity occurred when the number of receptive females was increased
relative to availability of a reproductively active male. Our results suggest male mate limitation can occur seasonally in
this species and that male limitation is regionally widespread and may affect recruitment. |
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Keywords: | Amphipod Corophium Mate limitation Operational sex ratios Recruitment |
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