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Research Progress

Reproductive Barriers between Two Sympatric Beetle Species Specialized on Different Host Plants

Dec 30, 2009

Speciation occurs as a result of the evolution of reproductive isolation between populations. Knowledge on interspecific pre- and post-zygotic isolation mechanisms provides insights into speciation patterns. Most species of genus Altica (Insecta: Coleoptera: Chrysomelidae) are specialists, therefore, the beetle genus was suggested as an ideal candidate for ecological speciation studies.

Based on crosses of two closely related flea beetles species specialized on different hosts in sympatry, we measured: (a) the type of reproductive isolation using an isolation indexes analysis and (b) the inheritance mode of preference and hostspecific performance, using a joint-scaling test and Castle–Wright estimator. Each species preferred almost exclusively its host plant, creating strong prezygotic isolation between them, and suggesting that speciation may occur at least partly in sympatry. Reproductive isolation was intrinsic between females of A. fragariae and either A. viridicyanea or F1 males, whereas the other crosses showed ecologically dependent reproductive isolation, suggesting ecological speciation. The genetic basis of preference and performance was at least partially independent, and several loci coded for preference, which limits the possibility of sympatric speciation. Hence, both ecological and intrinsic factors may contribute to speciation between these species. The result was published on Journal of Evolutionary Biology ( Xue HJ, Magalhães S, Li WZ, Yang XK. 2009. Journal of Evolutionary Biology 22: 22582266 ).

Recently, a "specialist beetle–host plant" system was selected and a series of works focused on host plant specialization, reproductive isolation and speciation have been carried out by Prof. Xing-Ke Yang’s research group at Institute of Zoology, Chinese Academy of Sciences. Five papers have been published on international journals since 2007 (other four papers: Ecological Entomology 2009, 34: 7480; Naturwissenschaften 2008, 95: 639–645; Entomologia Experimentalis et Applicata 2007, 125: 119124; Environmental Entomology 2007, 36: 468474). The works mentioned above were mainly executed by Dr. Huai-Jun Xue, and supported by a National Natural Science Foundation of China.

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