title: Phylogenetic position of the bee genera Ancyla and Tarsalia (Hymenoptera: Apidae): a remarkable base compositional bias and an early Paleogene geodispersal from North America to the Old World.
abstract: We address the phylogenetic position of the bee genera Tarsalia and Ancyla (currently forming the tribe Ancylaini) on the basis of morphological, molecular and combined data. We assembled a matrix of 309 morphological characters and 5246 aligned nucleotide positions from six nuclear genes (28S, EF-1a, wingless, POL2, LW-Rhodopsin, NAK). In addition to both constituent genera of Ancylaini, we include all three subtribes of the Eucerini as well as a large number of other tribes from the "eucerine line". The morphological data suggest Ancyla to be sister to Tarsalia+Eucerini and analyses of the entire molecular dataset suggest Tarsalia to be sister to Ancyla+Eucerini. However, analyses of the combined dataset suggests the Ancylaini to be monophyletic. We address possible bias within the molecular data and show that the base composition of two markers (EF-1a and NAK) is significantly heterogeneous among taxa and that this heterogeneity is strong enough to overcome the phylogenetic signal from the other markers. Analyses of a molecular matrix where the heterogeneous partitions have been RY-recoded yield trees that are better resolved and have higher nodal support values than those recovered in analyses of the non-recoded matrix, and strongly suggest the Ancylaini to be a monophyletic sister group to the Eucerini. A dated phylogeny and ancestral range reconstructions suggest that the common ancestor of the Ancylaini reached the Old World from the New World most probably via the Thulean Land Bridge in a time window between 69 and 47 mya, a period that includes the Early Eocene Climatic Optimum. No further exchanges between the New World and the Old World are implied by our data until the period between 22 mya and 13.9 mya. These more recent faunal exchanges probably involved geodispersal over the Bering Land Bridge by less thermophilic lineages.
authors.affiliation: Institute of Biology, University of Neuchatel, Emile-Argand 11, 2000 Neuchatel, Switzerland. Electronic address: christophe.praz@unine.ch.
authors.forename: Christophe J
authors.initials: CJ
authors.lastname: Praz
authors.affiliation: Department of Biology, York University, 4700 Keele St., Toronto, ON M3J 1P3, Canada.
authors.forename: Laurence
authors.initials: L
authors.lastname: Packer
mesh_terms: D000818:Animals; D001482:Base Composition; D001499:Bayes Theorem; D001516:Bees / Q000145:classification*; D005075:Biological Evolution; D017344:Genes, Insect; D005843:Geography; D016013:Likelihood Functions; D008957:Models, Genetic; D009656:North America; D010802:Phylogeny; D017422:Sequence Analysis, DNA
keywords: Ancylaini; Biogeography; Eucerini; Non-stationarity; North Atlantic Land Bridge; Stepping stone method