Support for maternal manipulation of developmental nutrition in a facultatively eusocial bee, <Emphasis Type="Italic">Megalopta genalis</Emphasis> (Halictidae) |
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Authors: | Karen M Kapheim Sandra P Bernal Adam R Smith Peter Nonacs William T Wcislo |
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Institution: | (1) Department of Ecology and Evolutionary Biology, University of California, Los Angeles, 621 Charles E. Young Dr. South, Los Angeles, CA 90095, USA;(2) Smithsonian Tropical Research Institute, MRC 0580-12, Unit 9100, Box 0948, DPO, AA 34002-9998, USA |
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Abstract: | Developmental maternal effects are a potentially important source of phenotypic variation, but they can be difficult to distinguish
from other environmental factors. This is an important distinction within the context of social evolution, because if variation
in offspring helping behavior is due to maternal manipulation, social selection may act on maternal phenotypes, as well as
those of offspring. Factors correlated with social castes have been linked to variation in developmental nutrition, which
might provide opportunity for females to manipulate the social behavior of their offspring. Megalopta genalis is a mass-provisioning facultatively eusocial sweat bee for which production of males and females in social and solitary
nests is concurrent and asynchronous. Female offspring may become either gynes (reproductive dispersers) or workers (non-reproductive
helpers). We predicted that if maternal manipulation plays a role in M. genalis caste determination, investment in daughters should vary more than for sons. The mass and protein content of pollen stores
provided to female offspring varied significantly more than those of males, but volume and sugar content did not. Sugar content
varied more among female eggs in social nests than in solitary nests. Provisions were larger, with higher nutrient content,
for female eggs and in social nests. Adult females and males show different patterns of allometry, and their investment ratio
ranged from 1.23 to 1.69. Adult body weight varied more for females than males, possibly reflecting increased variation in
maternal investment in female offspring. These differences are consistent with a role for maternal manipulation in the social
plasticity observed in M. genalis. |
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