Evol Ecol Res 1: 317-332 (1999)     Full PDF if your library subscribes.

The role of host-plant fidelity in initiating insect race formation

T.K. Wood,1 K.J. Tilmon,1‡ A.B. Shantz,1§ C.K. Harris1¶ and J. Pesek2

1Department of Entomology and Applied Ecology and 2Department of Food and Resource Economics, University of Delaware, Newark, DE 19717-1303, USA

Author to whom all correspondence should be addressed.
e-mail: sympatry@udel.edu


Advocates of sympatric speciation postulate that habitat-/host-associated mating and reproduction are critical conditions to reduce genetic constraints (recombination and migration) that otherwise impede divergence. To determine whether host-plant fidelity of insects could establish these conditions, we experimentally created sympatric host shifts. We shifted first instars of the treehopper Enchenopa (Homoptera: Membracidae) from their host-plant Viburnum lentago to three novel Viburnum species (V. lantana, V. utile and V. prunifolium). After eclosion, adults were marked and allowed to move freely between original and novel hosts. Hourly observations were made throughout each of the 33 days of the mating period to record host origin and location of individuals in mating pairs. At the onset of oviposition, daily observations were made to record the position within cages of marked ovipositing females and observations were made every 3 days to determine the location of every female within a cage. Under the conditions of this experiment, when dispersal distances between original and novel hosts were small, male and female host fidelity contributed to non-random mating and oviposition. Although some adults dispersed back to the original host, most did not. In the control treatment, containing two presumably equally ‘acceptable’ V. lentago plants, fidelity to the plant on which adults were raised resulted in non-random mating and oviposition. Our results suggest that host fidelity in the initial stages of a host shift could be a facilitating factor that allows divergent selection on host-associated performance traits and perhaps eventually host preference.

Keywords: Enchenopa, gene flow, insects, plants, speciation, sympatric.

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        © 1999 Thomas K. Wood. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

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