Differential energy allocation as an adaptation to different habitats in the parasitic wasp <Emphasis Type="Italic">Venturia canescens</Emphasis> |
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Authors: | Perrine Pelosse Carlos Bernstein Emmanuel Desouhant |
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Institution: | (1) Laboratoire de Biométrie et Biologie Evolutive (UMR 5558), CNRS, Univ. Lyon 1, 43 bd 11 nov, 69622 Villeurbanne Cedex, France |
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Abstract: | Environmental pressures are expected to favour organisms that optimally allocate metabolic resources to reproduction and survival.
We studied the resource allocation strategies and the associated tradeoffs in the parasitoid wasp Venturia canescens, and their adaptation to the characteristics of the environment. In this species, individuals of two reproductive modes coexist
in the same geographical locations, but they mainly occur in distinct habitats. Thelytokous (asexual) wasps are mostly found
in anthropogenic habitats, where hosts tend to aggregate and food is absent. Arrhenotokous (sexual) wasps are exclusively
found in natural habitats, where hosts are scattered and food is present. We analysed (1) the quantity of energy stored during
ontogeny, (2) the tradeoff between reproduction and survival, by measuring egg load and longevity and (3) the host patch exploitation
behaviour of the wasps at emergence. Arrhenotokous wasps emerged with more metabolic resources than thelytokous ones, especially
glycogen, a nutrient that could be used for flying in search of hosts and/or food. Thelytokous wasps allocated more energy
than arrhenotokous wasps to egg production: this would allow them to parasitize more hosts. The tradeoff between egg production
and longevity was not revealed within reproductive modes, but when comparing them. At emergence, arrhenotokous wasps tended
to exploit host patches less thoroughly than thelytokous wasps, suggesting that by leaving the host patch, they search for
food. The results clearly showed adaptations to the characteristics of habitats preferentially inhabited by the two reproductive
modes, and suggested a mechanism that facilitates their coexistence in natural conditions. |
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Keywords: | Habitat specialization Reproductive mode Energy allocation Tradeoffs Host patch exploitation Host quality Venturia canescens |
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