Preliminary phylogeny of Encarsia Forster (Hymenoptera : Aphelinidae) based on morphology and 28S rDNA

Species of Encarsia Forster (Hymenoptera: Aphelinidae, Coccophaginae) are e conomically important for the biological control of whitefly and armored sc ale pests (Hemiptera: Aleyrodidae, Diaspididae). Whereas some regional keys for identification of Encarsia species are now available, few studies have addressed relationships within this diverse and cosmopolitan genus because of unreliable morphological data. Nuclear sequences of the D2 expansion re gion of 28S rDNA were determined from 67 strains of 24 species representing 10 species groups of Encarsia, 2 strains of Encarsiella noyesi Hayat, and 1 strain of Coccophagoides fuscipennis Girault. Analysis of molecular data alone and combined with morphological data resolves many nodes not resolved by morphology alone and offer insights into which morphological characters are useful for supporting group relationships. All analyses that include m olecular data reveal Encarsia to be paraphyletic with respect to Encarsiell a. If monophyly of Encarsia is constrained, the relationships are the same but with a different root within Encarsia, and these trees are presented as an alternate hypothesis. The luteola and strenua species groups are shown by both morphological and molecular data to be monophyletic, whereas the in aron group, the E. nigricephala + luteola group, and the E. quericola + str enua group are supported only by molecular data. The aurantii and parvella species groups are not supported in any of the analyses. The utility of mor phological characters for defining species group relationships is discussed . (C) 2001 Academic Press.