Genetic Variation and the Role of Insect Life History Traits in the Ability of Drosophila Larvae to Develop in the Presence of a Competing Filamentous Fungus |
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Authors: | Marko Rohlfs |
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Institution: | (1) Zoological Institute, Department of Animal Ecology, Am Botanischen Garten 1-9, Christian-Albrechts-University of Kiel, D-24098 Kiel, Germany |
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Abstract: | Competitive interactions between organisms from distantly related phylogenetical branches have been suggested as being one
of the most pervasive forms of interspecific competition. However, so-called inter-kingdom competition has rarely been the
focus of ecological and evolutionary studies. Thus, a relatively novel hypothesis has been proposed on the basis that saprophagous
insects might intensively compete with filamentous fungi for ephemeral resources (e.g. decaying plant tissue). Consideration
that life history traits (e.g. developmental time) are adaptive in determining developmental success in the presence of con-
or hetero-specifics competitors implies that these traits have been progressively established by natural selection. Because
a similar scenario may apply to antagonistic interactions between saprophagous insects and filamentous fungi, one can expect
the existence of heritable variation in developmental success when insect larvae are forced to grow in the presence of noxious
mould. Therefore, this study aimed at discovering whether a local population of Drosophila melanogaster indeed harbours genetic variation in developmental success in the presence of the mould Aspergillus niger. By using the isofemale line technique, single larvae forced to feed on fungal infected or uninfected substrate were analysed
for variation in survival probability to the adult stage, developmental time and body size of emerged adults. I found genetic
variation in survival probability in fungal infected substrates but not in uninfected larval food sources. Mean developmental
time and body size varied significantly among isofemale lines in both types of larval environment. Survival was negatively
correlated with developmental time on fungal infected substrate, but variation in developmental time on fungal-free substrates
was not correlated with survival on fungal infected food patches. Within-trait correlation between fungal infected and uninfected
substrates was surprisingly weak, and developmental time was not correlated with body size. The results of this study demonstrate
(a) the existence of genetic variation for larval developmental success in the presence of A. niger in a Drosophila population, and (b) heritability of important insect life history traits differed as a function of the larval environment
(fungal infected or uninfected feeding substrate). I discuss models that might explain heritability differences and the evolutionary
consequences of these results. |
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Keywords: | genetic variation heritability differences insect– mould interaction inter-kingdom competition life history survival |
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