The immigrans group is an large Old World clade of about one hundred described species. This group has, interestingly, diversified in parallel with the tripunctata species group in the New World. Throckmorton considered this group a member of the immigrans radiation, a lineage basal to the tripunctata radiation. Remsen and O’Grady (2002), using molecular characters, placed this taxon basal to all species in their immigrans-tripunctata clade. In spite of recent taxonomic reorganization (Okada and Carson, 1983) removing the lineosa subgroup and placing it within the genus Zaprionus, no inclusive phylogenetic hypothesis exists for the immigrans species group. One study (Yu et al., 1999) examined the phylogeny of the nasuta subgroup. Within this subgroup, D. niveifrons is basal and sister to a large clade of relatively closely related taxa. Their phylogeny suggests that D. s. sulfurigaster, which is traditionally composed of several subspecies, may not be monophyletic. Instead, each of the three subspecies examined (neonasuta, albostrigata, bilimbata) may be species distinct from the typical D. s. sulfurigaster. These data also conclude that D. albomicans is not monophyletic at the species level, with populations from Chiangmai, China, being quite different from the other three populations sampled. Additional work, taking into consideration the remaining taxa in the immigrans species group, is needed.
(excerpted from Markow and O’Grady, 2006, Chapter 1)
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