Generic-Level Relationships Within the Ant Subfamily Dolichoderinae (Hymenoptera: Formicidae) S T E V E N 0
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Systematic Entomology (1995) 20,217-228 Generic-level relationships within the ant subfamily Dolichoderinae (Hymenoptera: Formicidae) s T E v E N 0 . s H AT T u c K CSIRO, Division of Entomology, Canberra, A.C.T., Australia Abstract. A cladistic analysis was undertaken to determine relationships among ex- tant genera of the ant subfamily Dolichoderinae. Twenty-one of the twenty-two cur- rently recognized genera within the subfamily were examined using 104 morphological characters.A single fully resolved, most-parsimonioustree was found when a combina- tion of ordered and unordered characters was used. When all characters were coded as unordered, seventy most-parsimonioustrees were found. The following results were found with both character coding methods. Leptomyrmex was placed basal to the remainder of the subfamily and the monophyletic sets Dolichoderus + Liometopum + Axinidris + Tapinoma + Technomyrmex, Froggattella + Iridomyrmex + Ochetellus + Papyrius + Philidris + Turneria, and Bothriomyrmex + Dorymyrmex + Forelius + Loweriella were suggested. The genera Linepithema and Doleromyrma showed a small amount of insta- bility in moving between neighbouring sister groups when the character coding method changed. The genera Anillidris and Anonychomyrma were difficult to place as they showed major differences in their positions between the two character coding methods. Introduction Table 1. Approximate number of extant, described dolichoderine spe- cies and subspecies by geographic region. Geographically widespread The ant subfamily Dolichoderinae forms one of the larger groups species are recorded for more than one region. Numbers in parentheses within the family Formicidae. The approximately 1000 described indicate introduced species occumng outside their normal, native range. extant species have been placed in up to forty-two genera and Regions follow Brown (1973) and are abbreviated as follows: Ne, Ne- subgenera. The most recent generic-level revision considered arctic; No, Neotropic; Pa, Palearctic; Et, Ethiopian; Ma, Malagasy; Or, twenty-two genera to be valid (Shattuck, 1992b). Members of Oriental; Au, Australian. ~ the subfamily occur world-wide in all geographic regions al- Genus Ne No Pa Et Ma Or Au Total though they are most species-rich in the tropics and Australia (Table 1). Most genera contain relatively few species (approxi- Anillidris -- 1 mately one-third contain fewer than ten) but several genera are Anonychomym 3 21 30 large (Azteca, 130 species; Dolichoderus, 154 species; Tapinoma, Axinidris -- 13 95 species; Technomyrmex, 88 species). Biogeographically, gen- Aztecu --130 era range from limited areas to worldwide. In some cases this Bothriomyrmex 76 45 apparent endemism may be caused by limited collection records, Doleromyrmu -3 3 for example the genera Anillidris (Argentina, Brazil), Ecphorella Dolichoderus 56 27 140 (Angola) and Loweriella (Sarawak, Brunei) are known from Dorymyrmex -- 78 Ecphorellu -- 1 three or fewer collections each. In other cases the taxa concerned Forelius -- 30 are regularly collected and appear to have genuinely restricted Froggattella -I 7 ranges. These include Doleromyrma (southern Australia) and Iridomynnex 6 74 80 Papyrius (Australia, New Guinea). At the other end of the spec- Leptomyrmex - 40 40 trum are genera with essentially worldwide distributions, for Linepithemu - (1) 28 example Dolichoderus and Tapinoma. Most taxa show patterns Liometopum 3- 8 between these extremes. These include Bothriomyrmex (Europe Loweriella 1- 1 east to Australia), Dorymyrmex (North and South America) and Ochetellus 18 10 Ochetellus (southeast Asia to Australia). For detailed discussion Pupyrius -6 6 of distribution patterns by genus, see Shattuck (1992b). Philidris 59 14 Tupinoma 20 7 95 Technomynnex 2 6(1) 37(1) 8(1) 26 9(1) 88 Correspondence: Dr S. 0.Shattuck, CSIRO, Division of Entomology, Turneriu -- -- -6 6 G.P.O. Box 1700, Canberra,A.C.T. 2601, Australia. 217 2 18 Steven 0. Shattuck From an ecological perspective, dolichoderines vary from One of the first studies of dolichoderine relationships was that minor components to dominant members of local faunas. One of of Emery (1 888). He produced a tree for ten dolichoderine gen- the most important groups ecologically is Iridomynnex in Aus- era, and included an ancestor and the most closely related non- tralia. Species of the Iridomymexpurpureus species group have dolichoderines. Although his proposed relationships are been shown to be dominant members of communities and to have limited to a subset of the currently recognized dolichoderine gen- a strong impact on the foraging activities of other ant species era, some of the proposals are still accepted today. These include with which they interact (Andersen & Patel, 1993, 1994; the close relationships of Tapinoma and Technomyrmex, and Greenslade, 1976). Several species are also notable pests. Bothriomyrmex, Dorymyrmex and Forelius. Also, the basal place- Linepithema humile (the Argentine ant), Tapinoma ment of Leptomyrmex within the subfamily is still accepted. In melanocephalum and Technomyrmex albipes are widely dis- most other aspects, however, Emery’s relationships have not been persed by human activity and can have a negative impact on lo- supported. The most notable are the close relationships between cal insect faunas (Bond & Slingsby, 1984; Ward, 1987). These Bothriomyrmex and Iridomyrmex, and the fact that Emery was species also commonly invade houses and buildings. uncertain of the monophyly of the Dolichoderinae. Taxonomically, the generic-level classification of these ants One of the only other statements on the generic-level relation- has recently been reviewed. The entire subfamily was examined ships for the entire subfamily was that of Brown (1973), who by Shattuck (1992b) including workers, queens, males and lar- compiled a list of the world ant genera in which the ordering of vae, and all previously proposed genus-group names were evalu- the genera was intended to indicate the relative primitiveness of ated. Substantial changes were proposed in the classification a group. Thus he placed ‘primitive’ taxa near the top of his list based on an analysis of approximately 180 morphological char- and more ‘advanced’ taxa near the bottom. However, because acters. In the system proposed by that study, all recognized gen- evolution of taxa is better viewed as occurring in multi-dimen- era were defined as sets of species possessing derived characters sional space, rather than linearly, this method of presentation has or unique sets of characters and thus were arguably monophyletic. limited value. Given this limitation, the following patterns are That study did not, however, examine the relationships among noteworthy. First, Leptomymex is placed basal to the remain- the genera of the Dolichoderinae. ing taxa of the subfamily. Second, Dolichoderus is considered In the present paper, all extant genera in the subfamily are fairly primitive within the subfamily. And finally, the following examined to determine the cladistic relationships among them. sets of taxa are considered closely related: Dolichoderus + The closely related subfamilies Formicinae and Aneuretinae Monoceratoclinea (treated as congeneric by Shattuck, 1992b), (Baroni Urbani et al., 1992; Bolton, 1990; Shattuck, 1992a; Axinidris + Liometopum + Sernonius (Semonius is treated as Ward, 1990) are used in the analysis to assist in the interpreta- congeneric with Tapinoma by Shattuck, 1992b), Froggattella + tion of the results. Characters which support the proposed rela- Iridomyrmex + Turneria, Bothriomyrmex + Dorymyrmex + tionships are discussed, and an attempt is made to quantify the Forelius + Neoforelius (Forelius and Neoforelius are considered relative strength of data supporting individual sets of taxa congeneric by Shattuck, 1992b), Engramma + Tapinoma + through the use of the bootstrap and an examination of trees Technomymex + Zutapinoma (Engramma and Technomymex, slightly longer than the most parsimonious. Relationships and Tapinoma and Zutapinoma, are considered congeneric by among the majority of genera are considered, although a single Shattuck, 1992b). However, several placements have not been genus, Ecphorella, could not be placed with confidence because supported during more recent studies. First, Brown (1973) placed of the lack of character information from the single known Linepithema near Dolichoderus. Second, Axinidris + worker and unknown queen and male castes and therefore it is Liometopum + Sernonius were placed close to Linepithema or excluded from the analysis. Tumena. Shattuck (1990) placed Turneria near Froggattella and Iridomyrmex, and Shattuck (1992b) synonomized Semonius with Tapinoma. Previous studies on dolichoderine relationships The only other broad-based classification systems proposed within the Dolichoderinae are at tribal level. Emery (1912) There has been little discussion of the relationships among the proposed a classification of the subfamily consisting of three genera of the Dolichoderinae. Earlier studies were limited tribes: Dolichoderini (Dolichoderus, Linepithema) Lepto- primarily to ‘classifications’ (lists of taxa grouped into sets myrmicini (Leptomyrmex) and Tapinomini (the remaining gen- (most often tribes)). These classifications were generally intended era of the subfamily). Fore1 (1917) modified this system by to reflect evolutionary patterns within the group, but were based placing the Dolichoderini and Leptomyrmicini together (as on the overall similarities of the taxa considered