Zaprionus, , Yassin & David, 2010

Russo, Claudia A. M., Mello, Beatriz, Frazão, Annelise & Voloch, Carolina M., 2013, Phylogenetic analysis and a time tree for a large drosophilid data set (Diptera: Drosophilidae), Zoological Journal of the Linnean Society 169 (4), pp. 765-775 : 770

ZAPRIONUS CLADE

The early branches within the major Drosophila clade indicate a Eurasian origin ( Fig. 2 ). Nevertheless, most early branches of this clade are restricted to Southeast Asia and the Pacific (SEA), strongly suggesting that the clade originated in the latter region (Table S2). The cosmopolitan Drosophila busckii Coquillett, 1901 , which is sister to all remaining species, is the type species of the SEA subgenus Dorsilopha (see also Grimaldi, 1990; Robe et al., 2010). Samoaia leonensis Wheeler & Kambysellis, 1966 , a member of the Pacific genus Samoaia , is the next species to diverge from the remaining lineages. Geographical consistency and morphological data indicate that Samoaia is monophyletic, but the type species, Samoaia ocellaris Malloch, 1934 , was unavailable. Therefore, the status of this genus remains to be ascertained ( Grimaldi, 1990; O’Grady & DeSalle, 2008). The remaining lineage divides to form the Zaprionus clade and the main Drosophila cluster ( Fig. 1 ).

The Zaprionus clade includes the SEA Liodrosophila aerea Okada, 1956 , which joins the clade consisting of the SEA Drosophila repletoides (Carson & Okada, 1980) plus Zaprionus . The repletoides species group is currently unassigned to higher rankings ( Yassin, 2013), but our topology suggests that it belongs to the Zaprionus clade (see also Van der Linde et al., 2010).

Zaprionus and Samoaia are currently assigned to the Zaprionus genus group ( Grimaldi, 1990; Yassin et al., 2010), but our results suggest that Samoaia is sister to a much larger group that includes Hirtodrosophila , Dichaetophora , Mycodrosophila , the Hawaiian Drosophilid clade, the subgenera Siphlodora and Drosophila , and the Zaprionus clade. Because the type species of Zaprionus ( Zaprionus vittiger Coquillett, 1901 ) and Liodrosophila ( L. aerea ) were sampled, our results indicate that these genera belong to the Zaprionus clade (see also O’Grady & Markow, 2009).

Our timescale shows that during the early Oligocene, an Old World Zaprionus ancestor diverged to form the subgenera Anaprionus (Eurasia) and Zap- rionus (Africa). Our time estimates imply that the Oligocene Zaprionus radiation did not prevent the Miocene radiation of the melanogaster subgroup, but may have impeded the radiation of the African ananassae and montium lineages, which remained undiversified ( Fig. 2 ). The difference in the melanogaster subgroup may be related to distinct ancestral ecological requirements or to sampling error; these alternatives remain to be tested using additional data.

In a recent Bayesian molecular analysis, one Zaprionus species ( Zaprionus K1) clustered with high support in a clade that included Drosophila funebris (Fabricius, 1787) (Yassin et al., 2010) . In our tree, however, Zaprionus is monophyletic, and D. funebris clusters elsewhere. Furthermore, Bayesian analyses are known to inflate clade support, and their statistical support may not hold if more consistent statistical tests are performed ( Suzuki et al. 2002). Even so, because this undescribed Zaprionus species was not included in our data set, the current diagnosis for Zaprionus may not represent a true clade. In a recent review of African Zaprionus, Yassin & David (2010) proposed a new definition of the species groups within Zaprionus based on morphological and molecular data. Their classification agrees well with our major Zaprionus clades ( Fig. 2 ), except that Zaprionus tsacasi Yassin, 2008 (from the inermis group) is tightly clustered with Zaprionus taronus Chassagnard & Tsacas, 1993 (from the vittiger group), well inside the vittiger clade.

Figures

Figure 1. Timescale for drosophilids based on a maximum-likelihood (ML) analysis using a concatenated alignment (9917 bp) of six protein-coding nuclear genes. Several monophyletic branches have been collapsed, indicating that all taxa within that taxonomic rank form a cluster. Support values above branches are bootstrap proportions performed on the ML tree; values less than 50 are not shown.

Figure 2. Phylogenetic tree showing the reconstructed ancestral geographical distributions for extant and ancestral drosophilids estimated by the maximum-likelihood algorithm. Extant geographical distributions were retrieved from the Drosophila Stock Center or from the ZipcodeZoo database. See Table S2 for geographical distributions.