Dr Mark Jervis - PhD
A parasitoid fly visiting a flower, to feed on its nectar.
Life-history diversity & evolution in insects
My principal research interest is the life history, diversity, behaviour and evolution of insect parasitoids - insects whose females lay their eggs in or on other invertebrates (mostly other insects) and whose larvae feed on the host and eventually kill it. Parasitoids (mostly comprising wasps, i.e. Hymenoptera) warrant study for several reasons: there are an estimated 2 million species (20% of all insects); they form an important component of most terrestrial insect communities; they play an important role in the population dynamics of their hosts; and they are widely employed in biological pest control.
A female parasitoid wasp, attempting to lay an egg in an aphid.
I am also interested in life-history diversity, behaviour and evolution of butterflies and moths. Like Hymenoptera, Lepidoptera form a major component of the World’s insectan biodiversity. In addition to having aesthetic value, they are of considerable importance as crop and forest pests, as prey/hosts for predators/parasitoids, as study organisms in evolutionary biology/ecology, and as indicators of environmental quality.
Head of parasitoid wasp, showing mouthpart specialisations for floral nectar extraction
With both Hymenoptera and Lepidoptera, I am particularly concerned with the relationships between key life-history traits: the timing of reproduction, life-span, resource allocation strategy, resource acquisition strategy (feeding habit), body size and mouthpart structure. A major goal of evolutionary biologists is to identify the factors that shape life-history differences and similarities among organisms. One approach to this is to seek cross-species correlations between different life-history traits.
Relationships between life-span, initial egg load (a positive correlate of ovigeny index) and diet breadth in Lepidoptera. Labels refer to different conceptual models. Life-span has been shown to be negatively correlated with diet breadth among a phylogenetically diverse array of Lepidoptera
A quite different, but complementary approach to identifying the factors responsible for life-history differences and similarities between organisms involves stochastic dynamic programming. It reveals correlations between different life-history traits at the intra-specific levels..
Negative correlations are of particular interest, as they imply a trade-off between traits and are evidence that life-histories are compromises. An associated goal is to understand the integration of suites of life-history traits. The ‘ovigeny’ concept – comprising the ovigeny index (a measure of temporal aspects of allocation to reproduction across the life-cycle) together with its correlates - can help us to attain these goals, and so contribute to a general life-history theory for insects (see publications, below).
Professor George Heimpel (University of Minnesota): phylogenetic signal in parasitoid host range