Brachycera

Introduction

The suborder Brachycera represents a major division of the Diptera containing approximately 120 families and a great diversity of species, morphological innovations, and life history strategies. The name "Brachycera" or "shortened horn" refers to their shortened antennae—a reduced antenna with fewer than 8 antennal flagellomeres is the easiest to recognise of a list of defining features (see below). The origins of the Brachycera can be traced to the late Triassic or earliest Jurassic (245-208 mya) based on fossil evidence (Evenhuis 1995; Grimaldi and Cumming 1999; Yeates and Wiegmann 1999) and comparisons of evolutionary rates in DNA sequences (Wiegmann et al. 2003).

Characteristics

Brachycera is well supported monophyletic lineage supported by a number of morphological synapomorphies (Yeates 2002; Yeates and Wiegmann 1999; Sinclair et al. 1993; Woodley 1989):

• reduction of antennal flagellomeres to 8 or fewer
• posterior portions of larval head capsule elongated into prothorax
• maxillary palpus with 2 segments or fewer
• wing veins CuA2 and A1 with apices approximate, forming a nearly closed cell Cup
• larval mandible subdivided into distinct two parts
• premandibles lost from ventral surface of labrum
• epandrium and hypandrium of male genitalia separated.

Brachyceran flies exhibit a broad array of feeding strategies, life histories and behavioral patterns. Many of the orthorrhaphous lineages are scavengers, predators or parasitoids as larvae. Multiple major radiations of species diversity, feeding habits and habitat specialization can be found in the Cyclorrhapha or "higher" flies.

Discussion of Phylogenetic Relationships

Traditional non-phylogenetic classifications of the brachycera break the group into two major sections, the 'Orthorrhapha' and Cyclorrhapha. The 'Orthorrhaphous' Brachycera is a paraphyletic assemblage of all those families not included in the Cyclorrhapha. Recent classifications based on explicit phylogenetic evidence include 4 monophyletic infraorders: Stratiomyomorpha, Xylophagomorpha, Tabanomorpha, and Muscomorpha.

Brachyceran phylogeny has been the subject of intensive study in recent years. Comprehensive phylogenetic treatments in Hennig (1973), Griffiths (1972), Woodley (1989) and Sinclair et al. (1994) began the explicit definition of clades based on synapomorphic character states (see Yeates and Wiegmann 1999 for a review). Quantitative phylogenetic analyses of morphological (Yeates 1994, 2002; Yeates et al. 2003; Meier and Hilger 2000) and gene sequence data (Wiegmann et al. 2000, Wiegmann et al. 2003; Collins and Wiegmann 2001ab; Moulton and Wiegmann 2004) continue to add resolution and support to many of the key lineages of brachyceran flies.

References

Collins, K. P. and B. M. Wiegmann. 2002. Phylogenetic relationships and placement of the Empidoidea (Diptera: Brachycera) based on 28S rDNA and EF-1a sequences. Insect Syst. Evol. 33: 21-444.

Griffiths, G. C. D. 1972. The phylogenetic classification of Diptera Cyclorrhapha, with special reference to the male postabdomen. Series entomologica 8, 340pp. The Hague.

Griffiths, G. C. D. 1994. Relationships among the major subgroups of Brachycera (Diptera): A critical review. Can. Entomol. 126:861-880.

Hennig, W. 1973. Diptera. In: W. Kukenthal (ed.) Handbuch der Zoologie, IV: Arthropoda. de Gruyter, New York, pp. 1-337.

Krivosheina, N. P. 1991. Phylogeny of lower Brachycera (Diptera): A new view. Acta Entomol. Bohemoslov. 88:81-92.

McAlpine, J. F., B. V. Peterson, G. E. Shewell, H. J. Teskey, J. R. Vockeroth, and D. M. Wood (eds.). 1981, 1987. Manual of Nearctic Diptera, Vol. 1 & 2. Research Branch, Agriculture Canada, Monographs 27 & 28.

McAlpine, J. F. and D. M. Wood (eds.). Manual of Nearctic Diptera, Vol. 3. Research Branch, Agriculture Canada, Monograph 32.

Moulton, J. K. and B. M. Wiegmann. 2004. Evolution and phylogenetic utility of CAD (rudimentary) among Mesozoic-aged Eremoneuran Diptera (Insecta). Mol. Phylogenet. Evol. 31: 363-378.

Nagatomi, A. 1991. History of some families of Diptera, chiefly those of the lower Brachycera (Insecta: Diptera). Bull. Biog. Soc. Japan 46(1-22): 21-38.

Nagatomi, A. and N. Liu. 1994. Apystomyiidae, a new family of Asiloidea (Diptera). Acta Zool. Hung. 40:203-218.

Sinclair, B. J. 1992. A phylogenetic interpretation of the Brachycera (Diptera) based on the larval mandible and associated mouthpart structures. Syst. Entomol. 17:233-252.

Sinclair, B. J., Cumming, J. M. and D. M. Wood. 1994. Homology and phylogenetic implications of the male genitalia in Diptera-Lower Brachycera. Entomol. Scand. 24:407-432.

Wada, S. 1991. Morphological evidence for the direct sister group relationship between the Schizophora and the Syrphoidea (Aschiza) in the phylogenetic systematics of the Cyclorrhapha (Diptera: Brachycera). J. Nat. Hist. 25:1531-1570.

Wiegmann, B. M., C. Mitter, and F. C. Thompson. 1993. Evolutionary origin of the Cyclorrhapha (Diptera): tests of alternative morphological hypotheses. Cladistics, 9:41-81.

Wiegmann, B. M., D. K. Yeates, J. L. Thorne, and H. Kishino. 2003. Time flies, a new molecular time-scale for brachyceran fly evolution without a clock. Syst. Biol. 52:745-756.

Woodley, N. E. 1989. Phylogeny and classification of the "Orthorrhaphous" Brachycera. In: McAlpine J.F., Wood D.M. (eds.)Manual of Nearctic Diptera 3. Research Branch, Agriculture Canada, Monograph 32:1371-1395.

Yeates, D. K. 1994. The cladistics and classification of the Bombyliidae (Diptera: Asiloidea). Bull. Am. Mus. Nat. Hist. 219:1-191.

Yeates, D. K. 2002. Relationships of the lower Brachycera (Diptera): A quantitative synthesis of morphological characters. Zool. Scripta 31:105-121.

Yeates, D. K. and B. M. Wiegmann. 1999. Congruence and controversy: Toward a higher-level phylogeny of Diptera. Ann. Rev. Entomol. 44:397-428.

Yeates, D. K., M. E. Irwin, and B. M. Wiegmann. 2003. Ocoidae, a new family of asiloid flies (Diptera: Brachycera: Asiloidea), based on Ocoa chilensis gen. and sp. nov. from Chile, South America. Syst. Entomol. 28:417-431.

Yeates, D. K., R. Meier, and B. M. Wiegmann. 2003. Phylogeny of true flies (Diptera): A 250 million year old success story in terrestrial diversification. Entomol. Abh. 61:119.

Zaitsev, V. F. 1991. On the phylogeny and systematics of the dipteran superfamily Bombylioidea (Diptera). Entomologicheskoe Obozrenie 70(3): 716-736.

Zloty, J., B. J. Sinclair, & G. Pritchard. 2005. Discovered in our backyard: a new genus and species of a new family from the Rocky Mountains of North America (Diptera, Tabanomorpha). Systematic Entomology. 30:248-266.