Lordiphosa, Basden, 1961

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 : 768-770

LORDIPHOSA – SOPHOPHORA CLADE

Following these early Palaeogene divergences, the Drosophila radiation shows a clear Eurasian origin ( Figs 1 , 2 ). The ancestor lineage splits to form the Lordiphosa – Sophophora clade and the major Drosophila clade in the middle Palaeocene (56 Mya), considerably earlier than previous estimates (40 Mya, Russo et al., 1995; 25–40 Mya, Obbard et al., 2012).

According to our topology, New World Sophophora share an ancestor with Eurasian Lordiphosa from Japan, Korea, and Russia, rather than with Eurasian Sophophora . Previous molecular studies have reported a close relationship between Lordiphosa and Drosophila ( Gao et al., 2011; Yassin, 2013). This pattern is morphologically reasonable because Lordiphosa was originally described as a subgenus of Drosophila Basden, 1961 (for further morphological evidence, see Okada, 1963; Lastovka & Máca, 1978, Fig. 2 ; Hu & Toda, 2001). Our time estimate for the split between Lordiphosa and New World Sophophora is near the Eocene–Oligocene boundary (36 Mya).

The New World Sophophora groups ( saltans and willistoni ) are monophyletic and form a clade. The monophyly of the willistoni group is now firmly established by morphological and molecular data, including the deletion of an Adh intron ( Van der Linde & Houle 2008, but see also O’Grady and Kidwell 2002). The willistoni subgroup also appears to be monophyletic, but is clustered within bocainensis with low support. In the saltans group, the saltans and sturtevanti subgroups are monophyletic with higher support values. Only one species was analysed for each of the cordata and elliptica subgroups, and these were clustered in our topology.

The Old World Sophophora groups ( ananassae , melanogaster , montium , and obscura ) also form a clade. Our timescale indicates that the protomelanogaster ancestor (sensu Throckmorton, 1975) radiated in Eurasia during the late Eocene ( Figs 1 , 2 ), but three African lineages emerged during the Miocene. The first African radiation took place during the middle Miocene, giving rise to the entire melanogaster subgroup. The second, during the late Miocene, occurred within the montium group, and the third African lineage ( Drosophila lachaisei Tsacas, 1984 ) diverged during the early Miocene within the ananassae group.

In the melanogaster group, the elegans , melanogaster , and pseudotakahashii subgroups appear to be monophyletic, but the suzuki and ficusphila subgroups do not ( Fig. 1 ). Although there are several Australian Drosophila lineages (e.g. Drosophila flavohirta Malloch, 1924 ; Drosophila pseudotakahashii Mather, 1957 ), no melanogaster radiation occurred on that continent. Based on morphological and ecological data, Throckmorton (1975) has suggested that such a radiation was prevented by a major Scaptodrosophila diversification when the melanogaster ancestor arrived in Australia. Our timescale marginally supports this hypothesis, but a larger sample of Australian Scaptodrosophila species is needed to verify this conclusion.

The radiation of the obscura species group apparently began during the middle Miocene ( Fig. 1 ). Most lineages within this group are Eurasian, except for a small African clade. Apart from those, two subgroups are endemic to the New World: affinis and pseudoobscura . These New World subgroups are clustered within a clade that also includes the incertae sedis Drosophila helvetica Burla, 1948 . Drosophila helvetica is from Asia and is weakly clustered with the New World pseudoobscura , but the New World affinis is strongly linked to this group.

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.