Abstract
The sex ratio of sexually reproducing animal species tends to be 1:1, which is known as Fisher’s principle. However, differential mortality and intraspecific competition during pupation can result in a biased adult sex ratio in insects. The female-biased sex ratio of small hive beetles (SHBs) is known from both laboratory and field studies, but the underlying reasons are not well understood. Here, we used laboratory mass and individual pupation to test if differential mortality between sexes and/or intraspecific interactions can explain this sex ratio. The data show a significant female-biased adult sex ratio in both mass and individual rearing, even when assuming that all dead individuals were males. Our results therefore suggest that neither differential mortality during pupation nor intraspecific interactions are likely to explain the female-biased sex ratio of freshly emerged adult SHBs. We regard it as more likely that either competition during the larval feeding stage or genetic mechanisms are involved. In addition, we compared our data with previously published data on the sex ratio of both freshly emerged and field-collected SHBs to investigate possible gender differences in adult longevity. The data show a significantly greater female bias in the sex ratio upon emergence, compared to field-collected SHBs, suggesting that adult females have a shorter longevity.
Highlights
The ratio of adult females to males is a key parameter for the biology of any sexually reproducing animal species [1]
[24] and/or differential suggest mortality of adult have reduced longevity, possibly due to costs associated with oviposition adultsSHBs in themay field
Our data confirm the female-biased sex ratio of newly emerged small hive beetles (SHBs) [6,7,8] and further suggest that neither differential mortality nor any intraspecific interactions during pupation are involved in any way
Summary
The ratio of adult females to males is a key parameter for the biology of any sexually reproducing animal species [1]. The sex ratio tends to be 1:1, which is known as Fisher’s principle. There are several insect and mite species that have a female-biased (e.g., fig wasps [2]) or male-biased sex ratio [3]) due to a range of different factors For small hive beetles (SHBs), Aethina tumida Murray (Coleoptera: Nitidulidae), several studies suggest a female-biased sex ratio in the laboratory [5,6,7] and in the field [8,9]. SHB is a parasite and scavenger of honeybee colonies, Apis mellifera. It is endemic to sub-Saharan Africa [10]
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