Pseudothaumatomyini

Pseudothaumatomyini Nartshuk, 1983

( Figs 106–107, 189–190)

Diagnosis: First flagellomere entirely black; parafacial large; eyes with converging inner margins in dorsal view; triangular pregonite; long michrotrichose distiphallus.

Genera included: Pseudothaumatomyia Nartshuk, 1963 , Xena Nartshuk, 1964 .

Some of the features that defined this group in Nartshuk’s (1984) system — composed of Chloropsina , Ensiferella , Neoloxotaenia and Pseudothaumatomyia —are the surstyli not divided into two lobes, a pair of anal sclerites and aligned gonites. Apparently, these features are highly plastic, so unrelated genera ended up together. Nartshuk (1984) herself argued that anal sclerites may have arisen more than once in the evolution of the subfamily. In our study, a good number of characters gather Pseudothaumatomyia and Xena in a clade sister to the Lasionini. Ismay (1990) proposed that Aragara is a member of this tribe; however, Nartshuk (2012) rejected his suggestion—a recommendation that finds support in our tree.

The tribe Pseudothaumatomyini is here restricted to only two genera, which share similarities in the male genitalia ( Figs 189–190). The tribe is present in previous classifications and we decided to keep the tribal status of the clade in our final classification. One of the reasons is that features connecting them to the Lasiosinini are fragile. In other words, even if formally in the tree they are sister to the Lasiosinini and could be made part of the tribe, the position of the Pseudothaumatomyini may change. Scutum pruinosity, one of the features connecting both tribes, is a widespread feature in the Chloropinae . The elongation of the epandrium, shared by both tribes, is the only reliable feature so far justifying the connection of the Lasiosinini to these two genera.

Lasiosinini Nartshuk. 1983 ( Figs 108–115, 191–197)

Diagnosis: Surstylus completely fused to epandrium; mesolobus extremely reduced (except Desertochlorops ); subepandrial sclerite developed; epiphallus absent.

Genera included: Assuania Becker, 1903 , Desertochlorops Nartshuk, 1966 , Lagaroceras Becker, 1903 , Lasiosina Becker, 1910 , Parachlorops Cherian, 2015 , Phyladelphus Becker, 1910 , Sabeurina Deeming, 2018 , Stenophthalmus Becker, 1903 , Urubambina Paganelli, 2002 .

The original defining features for the Lasiosinini ( Nartshuk, 1984) are the surstyli strongly connected to the epandrium, the reduced or absent mesolobus and the aligned gonites. Of the genera that Nartshuk included in this tribe, only Metopostigma appear in our analysis in a separate clade, within the Mepachymerini mainly because the surtyli are not fused to the epandrium. Cherian (2015) described Parachlorops and added the genus to the Lasiosinini , because of the complete fusion of the surstyli into the epandrium and because of the extremely reduced mesolobus. Cherian (2015) assumed Parachlorops to be close to Desertochlorops based on the presence of a tibial organ and the shape of the phallic complex and gonites. These two genera appear in our analysis as a grade at the base of the tribe, so these characters were present at the groundplan of the tribe. We examined Sabeurina minuta (Loew), 1860 Deeming, and its position within the Lasiosinini shows that Sabrosky (1980) and Deeming (2018) were correct in suggesting that the species does not belong in Eurina .

This tribe is a well-established group of the Chloropinae , because all genera share the surstyli completely fused to the epandrium (95; 2) and the mesolobus is reduced or almost indistinct (93; 2). The most conspicuous characters gathering the genera of this tribe are related to male terminalia. However, Urubambina (the only Neotropical genus in this tribe) is known only from females and could have been placed among other Lasiosinini members, possibly due to the large amount of missing data. Finding the males of Urubambina would be useful in corroborating its odd position.

DISTRIBUTION PATTERNS IN THE CHLOROPINAE

Biogeographical evolution is so complex a process that the development of formal methods of biogeographical reconstruction led to a state that Nelson & Ladiges (2001) described as a “mess of methods”. Indeed, mobility at a biotic scale in a considerable extension erases previous patterns, and many of the biogeographic methods have not been able to deal with the complexity of the biogeographical process. In this section, we address the general distribution patterns seen in the Chloropinae using the phylogeny of the subfamily obtained here, without any of the numerical analyses available.

It is considerably well-established that Schizophora diversification started early in the Cenozoic ( Grimaldi & Cumming, 1999; Wiegmann et al., 2011). This clearly denies the evolution of the schizophorans in general and of its families to Jurassic-Cretaceous events, prior to the present separation between continents. Different acalyptrate families seem to have evolutionary patterns that diverge to some degree. The extinct Eocene Baltic amber Protorygma (Evenhuis, 1994) , for example, is seen either as a stem Sepsidae or a stem Ropalomeridae ( Pont & Meier, 2002) , meaning either of these groups could be approximately Eocene in age. The Sepsidae have only one or two subclades that diversify in the Neotropical region ( Su et al., 2008, 2015). Hennig (1965) described the Baltic amber genera Hemilauxania and Chamaelauxania , which were assumed to be stem clades of the recent Lauxaniidae . Additionally, Stuckenberg (1971: fig. 9) showed that most genera of the Lauxaniidae with distribution present in the Neotropical region are connected to the Nearctic region; that most Afrotropical genera with wider distribution are connected to the Palaearctic and Oriental regions; and that most Australian genera with wider distribution are connected to the Oriental region. The lauxaniid subfamily Homoneurinae , for example, is entirely absent from the Neotropical region. “Transtropical patterns” were recently explained as cases of pseudocongruence with Gondwanan distributions—or “pseudogondwanan” patterns ( Amorim et al., 2018). Amorim et al. (2018) suggested that tropical Laurasian biota have expanded to the south in the Americas, into Africa and into Australia, followed by extensive extinction in the northern hemisphere in the Neogene along with global cooling. The existence of this tropical Laurasian biota allows to explain these patterns without demanding “transoceanic dispersal and without advocating Gondwanan origin. Hence, the differential expansion of clades of acalyptrate families into the southern continents and the differential extinction of these clades in the Nearctic and Palaearctic regions produced different, not necessarily congruent patterns, which are difficult to interpret.

The distribution patterns found in the Chloropinae differ from what is seen in the sepsids and lauxaniids. Hennig (1965) considered that there should have already been some diversification of the Chloropidae in the Eocene, because Protoscinella electrica Hennig has features that are modified in relation to the groundplan of the family. The fossil does not belong to the Chloropinae and may be close to the base of the Oscinellinae .

When we look at the distribution of the genera of chloropines in the phylogeny ( Fig. 1), it is clear that most clades with tribal rank have a worldwide distribution. The Eurinini have two main clades, one of which basically has a New World distribution (the “ Ectecephala group”), sister to a clade with basically an Old World distribution (the “ Eurina group”). Within the Meromyzini , this pattern also occurs, with the “ Coroichlorops group” (New World) being sister to the Mepachymerus group (Old World, except Sagareocerus ). The Mindini are restricted to the Old World, while all remaining tribes except the Chloropellini (known only from the Australian region) have species in both the Old World and the New World. This picture shows that different chloropine clades should have been present in this tropical biota over Laurasian terranes.

The evolution and diversification of the Chloropidae lineages must have had a connection to the diversification of grasslands ( Solecki et al., 2016). Greenwalt etal. (2019), forexample,describedanEocene compression fossil of Lonchoptera (of which adults are also associated with grassy, open environments— Klymko & Marshall, 2008) that is clearly sister to the set of extant species of the genus. The diversification of the crown group of the Poaceae (i.e. BEP+PACCMAD) was dated by Bouchenak-Khelladi et al. (2010) to begin in the early Eocene, 57 Mya, which may have been followed by the diversification, e.g. of Lonchoptera , in the Northern Hemisphere.

This set of evidence here available suggests that there was probably already some chloropine diversification during the Eocene. There are still no known fossils of the Chloropinae ; however, the association between the phylogeny and distribution patterns ( Fig. 1) suggests that perhaps eight or nine clades (mostly corresponding to the tribes of the Chloropinae ) were already present early in the second half of the Cenozoic. They must have expanded from an original “pan-Laurasian tropical” distribution to the Neotropics (producing the New World patterns) and to the Afrotropical and Australian regions (producing the Old World patterns). Molecular studies of chloropine clades in the near future will provide the age of divergence for the main clades that would test this hypothesis and build a better understanding of Chloropinae biogeography.