Phylogenetic relationships in the spoon tarsus subgroup of Hawaiian drosophila: Conflict and concordance between gene trees Richard T. Lapoint ⇑ , Alexander Gidaya, Patrick M. O’Grady University of California, Department of Environmental Science, Policy and Management, 137 Mulford Hall, Berkeley, CA 94720, United States article info Article history: Received 21 August 2010 Revised 24 December 2010 Accepted 24 December 2010 Available online 30 December 2010 Keywords: Hawaiian Drosophila Spoon tarsus subgroup Species tree abstract The Hawaiian Drosophilidae contains approximately 1000 species, placed in species groups and sub- groups based largely on secondary sexual modifications to wings, forelegs and mouthparts. Members of the spoon tarsus subgroup possess a cup-shaped structure on the foretarsi of males. Eight of the twelve species in this subgroup are found only on the Big Island of Hawaii, suggesting that they have diverged within the past 600,000 years. This rapid diversification has made determining the relationships within this group difficult to infer. We use 13 genes, including nine rapidly evolving nuclear loci, to estimate relationships within the spoon tarsus species, as well as to test the monophyly of this subgroup. A variety of analytical approaches are used, including individual and concatenated analyses, Bayesian estimation of species trees and Bayesian untangling of concordance knots. We find widespread agreement between phylogenetic estimates derived from different methods, although some incongruence is present. Notably, our analyses suggest that the spoon tarsus subgroup, as currently defined, is not monophyletic. Ó 2010 Elsevier Inc. All rights reserved. 1. Introduction The Hawaiian Islands, located approximately 4000 km from the nearest continent, are the most isolated island chain in the world (Carson and Clague, 1995). These volcanic islands rise out of the Pacific where lava seeps through a ‘‘hot spot’’ in the Earth’s crust, and over time becomes large enough to sustain life. As the Pacific Plate moves, islands are carried northwest. When an island moves off the hotspot, it become dormant and gradually erodes back into the sea (Carson and Clague, 1995). This leads to a datable progres- sion with young islands in the southwest and sequentially older islands in the northwest (see Fig. 1). High mountains that gradually slope into the sea characterize the young islands. Older islands are shorter, steeper and deeply carved by the action of wind and water (Price and Clague, 2002). The Hawaiian chain is currently composed of eight high islands, those that are high enough to catch the moist trade winds and pro- duce rainforest habitats. The high percentage of species found on the Hawaiian Islands has made it home to some of the highest lev- els of endemism in the United States (Eldredge and Evenhuis, 2003). Price and Clague (2002) have recently reviewed several lin- eages endemic to Hawaii that have originated from a single or few initial colonizers. In each of the lineages of endemic Hawaiian spe- cies that were reviewed it appears that the colonization occurred after the formation of the current high islands (Baldwin and Sanderson, 1998; Fleischer et al., 1998). However a few radiations are estimated to have colonized the island chain well before the formation of the current high islands, and have subsequently pro- gressed down to the younger islands as they form (Givnish et al., 1996; Jordan et al., 2003). The oldest inhabitants of the island chain are the Hawaiian Drosophilidae, a radiation derived from a single colonization event approximately 25 million years ago (Russo et al., 1995). Since this time they have diversified into a clade of 1000 species (O’Grady et al., 2010), occupying a wide variety of ecological niches (Heed, 1968; Montgomery, 1975; Magnacca et al., 2008) and displaying impressive morphological diversity (Hardy, 1965). They have diversified into many different niches, exploiting nearly 40% of the native plant families and even more bizarre substrates like spider eggs (Wirth, 1952). Most species also display marked sexual dimorphism, with males possessing elaborate secondary charac- ters, such as wing patterning, elongate antennae, tusk-like mouth- parts and elaborate processes on the tarsi (e.g., Stark and O’Grady, 2009), that they use in copulation. Mating displays are likewise diverse (Spieth, 1966). Morphological and molecular characters have been useful in defining several groups that have been tested by rigorous phylogenetic analysis (Baker and DeSalle, 1997; Bonacum, 2001; Bonacum et al., 2005; Carson and Stalker, 1969; Kambysellis et al., 1995; O’Grady and Zilversmit, 2004; O’Grady et al., in press). Males in the spoon tarsus clade have an eponymous cup-like second tarsi on their forelegs used in positioning females during mating (Spieth, 1966; Stark and O’Grady, 2009). All species are 1055-7903/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.ympev.2010.12.015 ⇑ Corresponding author. E-mail address: rlapoint@berkeley.edu (R.T. Lapoint). Molecular Phylogenetics and Evolution 58 (2011) 492–501 Contents lists available at ScienceDirect Molecular Phylogenetics and Evolution journal homepage: www.elsevier.com/locate/ympev