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1 June 2008 A partial molecular phylogeny of the Eumastacoidea s. lat. (Orthoptera, Caelifera)
S. Matt, P. K. Flook, C. H. F. Rowell
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Abstract

We used mitochondrial (12s, 16s) and nuclear (18s, 28s) ribosomal gene sequences to derive a phylogeny of the Eumastacoidea, with the aims of a) clarifying the position of the Proscopiidae with respect to the Eumastacoidea b) testing the phylogenetic hypothesis and classification advanced by Descamps 1973b for the Eumastacoidea, and c) deriving a time scale for the phylogeny based on molecular clock calculations. Four different analysis methods were employed: maximum parsimony, neighborjoining assuming minimum evolution, maximum likelihood and Bayesian analysis. The genes were analysed separately and after concatenation. The sample included 6 of the 7 families and 12 of the 31 subfamilies of the Eumastacoidea, and three proscopiids. We included tetrigoids (as outgroup) and tanaoceroids and trigonopterygoids to provide polarity.

No analysis supported placing the Proscopiidae within any of the existing branches of the Eumastacoidea. Some placed the two taxa as sistergroups within a Eumastacoidea s. lat., and some indicated that they are separate superfamilies. We cannot distinguish between these two possibilities with the present data.

Within the Eumastacoidea s.str. all of the groupings of subfamilies (i.e., families) proposed by Descamps were well-supported. Higher nodes of the phylogeny were in general only weakly supported. Descamps' suprafamilial groupings appeared in some but not all analyses. Of these groupings, the Cryptophalli (=Chorotypidae plus Episactidae) were not well supported, the Stenophalli (Eumastacidae plus Morabidae) were reasonably well supported, while the Disclerophalli (=Thericleidae plus Euschmidtiidae) were strongly supported, and additionally the Gomphomastacinae were associated with it. (The Euphalli, containing only the Indian family Mastacideidae, were not included in the analysis.)

The sequence data did not allow the assumption of a molecular clock, and for this reason the nodes of the phylogeny could not be dated.

Introduction

The Eumastacoidea are a superfamily of the Orthoptera Caelifera, almost worldwide in distribution, but predominantly tropical and entirely absent from Europe, New Zealand and Antarctica. They have long been considered a relatively early branch of the Caelifera, a view confirmed by molecular systematic investigations which place them after the Tridactyloidea and Tetrigoidea but before the remaining superfamilies (Flook & Rowell 1997, Rowell & Flook 1998, Flook et al. 1999). Like the more familiar Acridoidea they are subaerial herbivores of higher plants, but differ from them in numerous aspects of morphology, of which the superficially most obvious are the absence of an abdominal tympanum, small size, wings (when present) widening towards the tip, and, in most taxa, very short antennae and a laterally spread posture of the jumping hind legs when at rest.

Currently the superfamily (excluding the Proscopiidae, see below) contains 295 genera and 1103 species (totals derived from Otte, Eades & Naskrecki 2003). This represents about 10% of the entire Caelifera, making them the largest superfamily after the Acridoidea. Since their original recognition as a systematic group by Stål (1876), the eumastacids have been the subject of several major revisions, which have taken them to family and then to superfamily status and produced an ever-increasing number of subfamilies (Karsch 1889; Brunner 1893, 1898; Burr 1899, 1903; de Saussure 1903; Bolívar 1930, 1932; Rehn and Rehn 1934, 1939, 1942, 1945; Rehn 1948; Dirsh 1961, 1975; Descamps 1973b). The most recent of these (despite the chronologically later appearance of Dirsh's last work) is that of Descamps 1973b, who recognized 4 groupings of families, 7 families and 31 subfamilies (Table 1), principally on the basis of the male genitalia.

Table 1.

Classification of the Eumastacoidea according to Descamps (1973a), and the geographical distribution of the subfamilies.

i1082-6467-17-1-43-t01.gif

Descamps' classification, which was explicitly based on a hypothesis of phylogeny (Fig. 1), has been widely adopted, though some secondary authors have either reduced his families to subfamilies and the subfamilies to tribes (e.g., Otte 1994, Otte et al. 2003), or conversely have raised certain of Descamps' subfamilies to family rank (e.g., Kevan 1982). Some of his higher groupings of the taxa have been disputed by Amedegnato (19