Phylogeny and behaviour of the Gollumiellinae, a new subfamily of the ant-parasitic Eucharitidae (Hymenoptera: Chalcidoidea)

Gollumiellinae is proposed as a new subfamily for the Indo-Pacific genera Gollumiella Hedqvist and Anorasema Boucek based on analyses of three ribosomal transcript gene regions (28S-D2 and -D3, and 18S-E23; 1262 aligned base pairs) sequenced for twenty-eight genera and fifty-four species of Eucharitidae, and twelve genera and nineteen species of Pteromalidae (Pteromalinae) and Perilampidae (Chrysolampinae and Perilampinae). Gollumiella and Anorasema have been treated as either a monophyletic or paraphyletic group within the Eucharitini (Hymenoptera: Eucharitidae). The monophyly of the Eucharitidae and a sister-group relationship between Gollumiellinae and Oraseminae+Eucharitinae are supported strongly in parsimony and Bayesian analyses. The molecular phylogeny contradicts previous morphological hypotheses, in which Gollumiella and Anorasema are within Eucharitini. The strength of the molecular hypothesis is explored through evaluations of data alignments that are eye optimized, CLUSTAL-X aligned, eye optimized but with gaps coded as a fifth base, and eye optimized and combined with morphological data. The oviposition behaviour and host associations of G. longipetiolata on tree ferns (Cyathea latebrosa, Cyatheaceae), and the morphology of the planidium and pupa are newly described. Eggs are deposited vertically, with the base anchored into the leaf or petiolar surface. Unlike other Eucharitidae, the eggs are not stalked, but rather tipped with a secretion that may act as an attractant for their ant host, Paratrechina sp. (Formicidae:Formicinae). Various morphological character state optimizations and their implications for convergent morphology, behaviour and host associations are discussed. All results using gene regions treated separately or combined with the morphological data reach the same conclusion: Anorasema+Gollumiella form the sister group of Oraseminae+Eucharitinae, and thus deserve subfamily status. This suggests that very distinct traits such as the fusion of the pronotum and prepectus in adults and the fusion of the first two tergites of the planidia are convergent apomorphies. Molecular data, when strongly supported, can provide new information to unravel convergent from synapomorphic changes, resulting in more robust hypotheses of relationship.