Behavioural, ecological and genetic evidence confirm the occurrence of host-associated differentiation in goldenrod gall-midges

Authors


Netta Dorchin, Museum Koenig, Adenauerallee 160, Bonn 53113, Germany.
Tel.: +49 228 9122 292; fax: +49 228 9122 212; e-mail: n.dorchin.zfmk@uni-bonn.de

Abstract

Host-associated differentiation (HAD) is considered a step towards ecological speciation and an important mechanism promoting diversification in phytophagous insects. Although the number of documented cases of HAD is increasing, these still represent only a small fraction of species and feeding guilds among phytophagous insects, and most reports are based on a single type of evidence. Here we employ a comprehensive approach to present behavioural, morphological, ecological and genetic evidence for the occurrence of HAD in the gall midge Dasineura folliculi (Diptera: Cecidomyiidae) on two sympatric species of goldenrods (Solidago rugosa and S. gigantea). Controlled experiments revealed assortative mating and strong oviposition fidelity for the natal-host species. Analysis of mitochondrial DNA showed an amount of genetic divergence between the two host-associated populations compatible with cryptic species rather than host races. Lower levels of within-host genetic divergence, gall development and natural-enemy attack in the S. gigantea population suggest this is the derived host.

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