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John Alcock 《Behavioral ecology and sociobiology》1996,39(3):181-188
I examine three alternative hypotheses on the male size dimorphism of Dawson’s burrowing bees (Amegilla dawsoni) in which there are large (major) and small (minor) males. One possibility is that minor males are simply the incidental
byproduct of environmental conditions that prevent females from provisioning brood cells optimally. This hypothesis is not
supported by the finding that males of intermediate size are consistently rare in populations sampled across years and in
different regions, nor can it easily account for the absence of a size dichotomy in females. A second possibility is that
minors represent a “best of a bad job” response of those females that are small or otherwise disadvantaged. However, presumptive
male siblings sometimes include both majors and minors, a result not predicted from this hypothesis. A third explanation is
that female brood provisioning strategy results in the production of minors and majors with equal fitness benefit to fitness
cost ratios. However, although it is true that minor males weigh on average about half what a major weighs, and so represent
approximately half the provisioning expense of a major, minor males on average appear to secure far fewer than half the number
of matings of majors. If the estimate of mating success of minors is accurate, the net gain to females from producing a minor
son is unlikely to equal that derived from a major son. Therefore the third hypothesis must also be tentatively rejected,
although with caution given the uncertainties in estimating the relative costs and benefits of producing major and minor sons.
Received: 12 January 1996/Accepted after revision: 27 April 1996 相似文献
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