Heteronychia

Whitmore, Daniel, Pape, Thomas & Cerretti, Pierfilippo, 2013, Phylogeny of Heteronychia: the largest lineage of Sarcophaga (Diptera: Sarcophagidae), Zoological Journal of the Linnean Society 169 (3), pp. 604-639 : 625-629

MONOPHYLY OF HETERONYCHIA

The results of our analysis show that the species previously assigned to the subgenus Discachaeta do not form a clade, as already hypothesized by Whitmore et al. (2009) and Whitmore (2011). Sarcophaga longestylata , which was previously placed in a subgenus of its own ( Notoecus ) because of a couple of striking autapomorphies (the possession of only two postsutural dorsocentral setae and the possession of a long petiole on wing-cell r 4+5), turned out to be clearly included within the Sar. filia -group, i.e. one of the most strongly supported species-groups resulting from the analysis.

The clade [ Heteronychia + ex- Discachaeta + Sar. longestylata ] is well supported and is corroborated by the following autapomorphies: (1) microtrichosity on syntergosternite 7 + 8 present as a median line or small to large spot (16:1,2); (2) pregonite with (usually long) setae reaching all the way to tip (35:3); (3) postgonite with a sharply pointed tip (38:0); (4) lateral styli narrow in width, occupying only a small volume of distiphallus (56:1); (5) main axis of juxta orientated apicoventrally (64:2); (6) juxta divided into a median and two lateral processes (66:2); (7) tip of juxta blunt, rounded in lateral view (74:1); (8) tip of juxta in apical view with cupped lateral processes and a subtrapezoidal median process (81:3). Three of these (3, 4, 8) are unique autapomorphies supporting that clade in our study. In Sarcophaga , the plesiomorphic condition would seem to be that of microtrichosity covering most of the width of syntergosternite 7 + 8, and the occurrence of this microtrichosity as a thin median line or median patch (variable in size) seems to be a synapomorphy defining Heteronychia . Its complete reduction has arisen several times within the clade, as in species from other subgenera such as Sarcophaga (Kramerella) granulata Kramer , Sarcophaga (Sarcotachinella) sinuata Meigen , Sarcophaga (Liopygia) argyrostoma (Robineau-Desvoidy) , and Sarcophaga (Liopygia) crassipalpis Macquart. A sharply pointed, hooked postgonite, which here defines our Heteronychia clade (a blunt tip being found only in Sarcophaga amputata ), can be found in various other subgenera (e.g. in Krameromyia Verves , Liosarcophaga , Robineauella Enderlein ). Lateral styli of narrow width represent the norm in the genus Sarcophaga (cf. Giroux et al., 2010). A juxta subdivided into a median part and elongated lateral processes is typical, for example, of Liosarcophaga , but the widely rounded off or ‘spoonshaped’ structure of the lateral processes is unique to Heteronychia . Although many groups of Sarcophaga s.l. have a juxta whose main axis is orientated more or less ventrally (i.e. perpendicular to the main axis of the distiphallus), in several species scattered across the genus, including the type species Sarcophaga carnaria , it is orientated apicoventrally or apically (e.g. in subg. Pandelleana Rohdendorf ). The presence of long setae on the entire dorsal surface of the pregonite, reaching the tip (reduced to the basal half or basal two-thirds in many species), and the configuration of the juxtal tip (apical view) with small, cupped lateral processes and a subtrapezoidal median process ( Fig. 11F ), would seem to be unique autapomorphies of Heteronychia . Relatively long setae on the dorsal surface of the pregonite (longer than width of pregonite) can be found in two species of the subgenus Helicophagella : Sarcophaga novella Baranov and Sar. noverca ; however, they are not as long as the setae found in several species of Heteronychia (e.g. Sarcophaga gabrielei , Sarcophaga filia , Sarcophaga vicina , Sarcophaga kerteszi ), which possibly represents the plesiomorphic condition within the group, with several degrees of secondary reduction having subsequently occurred. Within the remaining Sarcophaga , including the rest of Helicophagella , the pregonite is either bare or with a few very short setulae on its dorsal surface, never longer than the width of the pregonite itself, this probably representing the plesiomorphic condition within the genus (cf. Richet et al., 2011). In addition to these character states, others can be useful to define the [ Heteronychia + Discachaeta + Sar. longestylata ] clade, such as the vesica consisting of a single scale-like process often reduced in size (a state shared, for example, with several species of Helicophagella ), and the epandrium with an elongated ventral margin. This last character state is also shared with Helicophagella , but in most species of Heteronychia apart from those of the Sar. filia - and Sar. minima -groups the epandrium is usually more elongated, often noticeably so.

Despite the identification of just three probable unique autapomorphies, both of which may seem prone to homoplasy because of simplicity, the group is unequivocally identified by these and by the above combination of character states.

Considering all the above, as well as the limited phylogenetic resolution and the presence of only a few well-corroborated morphological subgroupings, we think that the analysed species should all be included within one subgenus, Heteronychia , with Discachaeta and Notoecus as subgeneric synonyms. Verves (1989) already recognized the affinity of Sar. longestylata with Heteronychia by moving it to subtribe Heteronychiina after Rohdendorf (1965) had placed it in subtribe Bellieriina . Finally, it must be noted that in the phylogenetic analysis carried out by Giroux et al. (2010) on the subfamily Sarcophaginae , Discachaeta and Heteronychia came out as quite distant from one another; this can probably be ascribed to the low taxon sample from these two nominal taxa (one species each). A recent analysis by Jordaens et al. (2013) using the molecular marker cytochrome oxidase subunit I grouped Sar. cucullans and Sar. pumila together with other species of Heteronychia . We here substantially confirm their findings from a morphological standpoint.

Figures

Figure 11. A, Sarcophaga (Heteronychia) cucullans, distiphallus, lateral (detail of juxta, arrow showing ventral protuberance) (Latina, Italy). B, Sarcophaga (Heteronychia) mutila, distiphallus, lateral (detail, arrow showing preapical lateral indentation of juxta) (Promontorio del Gargano, Italy). C, Sarcophaga (Heteronychia) bulgarica, juxta, lateral (detail, arrow showing median depression of tip of juxta) (Verona, Italy). D, Sarcophaga (Heteronychia) bezziana, distiphallus, apical (detail, arrow showing tip of juxta) (Stazzo Rotolo, Italy). E, Sarcophaga (Heteronychia) ferox, tip of juxta, dorsal (Afourer, Morocco). F, Sarcophaga (Heteronychia) consanguinea, juxta, apical (Corleone, Sicily; arrow showing subtrapezoidal median process of juxta).