Aging and demographic plasticity in response to experimental age structures in honeybees (<Emphasis Type="Italic">Apis mellifera</Emphasis> L) |
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Authors: | Olav Rueppell Robyn Linford Preston Gardner Jennifer Coleman Kari Fine |
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Institution: | (1) Department of Biology, University of North Carolina at Greensboro, 312 Eberhart Building, Greensboro, NC 27403, USA;(2) Present address: Bryan School of Business, University of North Carolina at Greensboro, Greensboro, NC 27403, USA;(3) Present address: West Virginia School of Osteopathic Medicine, Lewisburg, WV 24901, USA;(4) Present address: College of Veterinary Medicine, University of Georgia, Athens, GA 30602, USA |
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Abstract: | Honeybee colonies are highly integrated functional units characterized by a pronounced division of labor. Division of labor
among workers is mainly age-based, with younger individuals focusing on in-hive tasks and older workers performing the more
hazardous foraging activities. Thus, experimental disruption of the age composition of the worker hive population is expected
to have profound consequences for colony function. Adaptive demography theory predicts that the natural hive age composition
represents a colony-level adaptation and thus results in optimal hive performance. Alternatively, the hive age composition
may be an epiphenomenon, resulting from individual life history optimization. We addressed these predictions by comparing
individual worker longevity and brood production in hives that were composed of a single-age cohort, two distinct age cohorts,
and hives that had a continuous, natural age distribution. Four experimental replicates showed that colonies with a natural
age composition did not consistently have a higher life expectancy and/or brood production than the single-cohort or double-cohort
hives. Instead, a complex interplay of age structure, environmental conditions, colony size, brood production, and individual
mortality emerged. A general tradeoff between worker life expectancy and colony productivity was apparent, and the transition
from in-hive tasks to foraging was the most significant predictor of worker lifespan irrespective of the colony age structure.
We conclude that the natural age structure of honeybee hives is not a colony-level adaptation. Furthermore, our results show
that honeybees exhibit pronounced demographic plasticity in addition to behavioral plasticity to react to demographic disturbances
of their societies. |
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Keywords: | Aging Mortality Social insects Division of labor Homeostasis Colony productivity Biodemography |
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