Sex Allocation

Honeybee colony drone production and maintenance in relation to environmental factors: an interplay of queen and worker decisions.

by Katie Wharton Boes

Boes KE.  Published 2010 in Insectes Sociaux

Social insect colonies display a remarkable ability to adjust investment in reproduction (i.e., production of sexuals)... more Social insect colonies display a remarkable ability to adjust investment in reproduction (i.e., production of sexuals) in accordance with environmental conditions such as season and food availability. How this feat is accomplished by the colony’s queen(s) and workers remains a puzzle. Here, I review what we have learned about this subject in the European honeybee (Apis mellifera), specifically with regard to a colony’s production of males (drones). I identify five environmental conditions that influence colony-level patterns of drone production and then define five stages of drone rearing that are accomplished by the queen and workers. Using this framework, I detail our current understanding of how the queen or workers adjust their actions at each stage of drone rearing in response to each of the environmental conditions. Future investigations of this topic in honeybees and other social insect societies will lead to a better understanding of how colonies manage to flexibly and efficiently allocate their resources under changing environmental conditions.

Baeza, J.A. and C. Piantoni. 2010. Sexual system, sex ratio and group living in the shrimp Thor amboinensis (De Man): relevance to resource-monopolization and sex-allocation theories. Biological Bulletin 219: 151–165.

by Antonio Baeza

Facultative sex allocation in the viviparous lizard Eulamprus tympanum, a species with temperature-dependent sex determination

by Kylie Robert

Emerging sex allocation research in mammals: marsupials and the pouch advantage

by Kylie Robert

Offspring sex varies with maternal investment ability: empirical demonstration based on cross-fostering

by Kylie Robert

Sex determination: viviparous lizard selects sex of embryos

by Kylie Robert

Sex Ratio at Birth and Mortality Rates Are Negatively Related in Humans

by Madhukar Dama

Evolutionary theory posits that resource availability and parental investment ability could signal offspring sex... more Evolutionary theory posits that resource availability and parental investment ability could signal offspring sex selection, in order to maximize reproductive returns. Non-human studies have provided evidence for this phenomenon, and maternal condition around the time of conception has been identified as most important factor that influence offspring sex selection. However, studies on humans have reported inconsistent results, mostly due to use of disparate measures as indicators of maternal condition. In the present study, the cross-cultural differences in human natal sex ratio were analyzed with respect to indirect measures of condition namely, life expectancy and mortality rate. Multiple regression modeling suggested that mortality rates have distinct predictive power independent of cross-cultural differences in fertility, wealth and latitude that were earlier shown to predict sex ratio at birth. These findings suggest that sex ratio variation in humans may relate to differences in parental and environmental conditions.

High Fat Diet Prevents Over-Crowding Induced Decrease of Sex Ratio in Mice

by Madhukar Dama

Adaptive theory predicts that mothers would be advantaged by adjusting the sex ratio of their offspring in relation to... more Adaptive theory predicts that mothers would be advantaged by adjusting the sex ratio of their offspring in relation to their offspring's future reproductive success. In the present study, we tested the effect of housing mice under crowded condition on the sex ratio and whether the fat content of the diet has any influence on the outcome of pregnancies. Three-week-old mice were placed on the control diet (NFD) for 3 weeks. Thereafter the mice were allotted randomly to two groups of 7 cages each with 4, 6, 8, 10, 12, 14, and 16 mice in every cage to create increasing crowding gradient and fed either NFD or high fat diet (HFD). After 4 weeks, dams were bred and outcomes of pregnancy were analyzed. The average dam body weight (DBW) at conception, litter size (LS) and SR were significantly higher in HFD fed dams. Further, male biased litters declined with increasing crowding in NFD group but not in HFD. The LS and SR in NFD declined significantly with increasing crowding, whereas only LS was reduced in HFD group. We conclude that female mice housed under overcrowding conditions shift offspring SR in favor of daughters in consistent with the TW hypothesis and high fat diet reduces this influence of overcrowding.