Genetic differentiation and speciation among four Phyllotreta species (Coleoptera: Chrysomelidae)
1998
Verdyck, P.
Among the four closely related Phyllotreta species P. dilatata Thomson, 1866, P. flexuosa (Illiger, 1794), P. ochripes (Curtis, 1837) and P. tetrastigma (Comolli, 1837) several systematic problems occur due to the existence of colour pattern variation and morphological similarity. All four species feed on Brassicaceae, but P. tetrastigma, P. flexuosa and P. dilatata are monophagous in the field, whereas P. ochripes is oligophagous. Genetic differentiation and systematic relationships of the four species are studied by means of allozyme electrophoresis of 10 variable loci, with a total of 30 allelomorphs. Of the six alleles that are present only in a single species, none is diagnostic. Rogers modified genetic distance and Cavalli-Sforza & Edwards arc distance between all populations are calculated and Distance Wagner trees are constructed, revealing three major groups. P. ochripes is separated first, being the most distant species. The three other species are more closely related, and within this group P. dilatata is separated from the other two. The last group contains the populations of P. tetrastigma and P. flexuosa. In the differentiation between the different species host plant shifts and consequent genetic differentiation have been important.
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