deciphering their diversity and evolutionary history

Smithsonian National Museum of Natural History

Asiloid Flies
deciphering their diversity and evolutionary history

Sample of Asiloid Flies

Phylogenetic relationships within Asiloidea

The phylogenetic relationships among the family taxa of Asiloidea are not entirely resolved. There appears to be a clade comprising Apsilocephalidae, Evocoidae, Scenopinidae, and Therevidae. Sister-taxon to that clade is most probably a clade comprising Apioceridae, Asilidae, and Mydidae.

Hull (1962) and Yeates (1994) postulated that Asilidae and Apioceridae are sister-taxa.

Hennig (1973) was undecided about the adelphotaxon relationships of Apioceridae and Mydidae in respect to Asilidae.

Wood (1981) discussed a probable sister-group relationship between the Mydidae and Asilidae. Character states she mentioned that emphasised the hypothesis were:

  • well-developed face (swelling on which the mystax is situated in Asilidae, but there are often also setae in Mydidae present)
  • depressed vertex
  • larvae with broadened paddle-like or scoop-like maxilla.

Woodley (1989), Yeates & Irwin (1996), and Yeates (2002) placed the Mydidae and Apioceridae as a monophyletic taxon forming a sister-group. Characters supporting this relationships are:

  • wing with veins R5 and M1 strongly curved anteriorly, ending anterior to wing tip
  • adult with supernumerary rectal papillae.

Yeates (1994) hypothesised a sister-group relationship between Mydidae and Scenopinidae with the following synapomorphies:

  • short posterior arms of cibarial pump
  • epandrium completely divided medially
  • lateral aedeagal apodemes absent.

Yeates (1994) also postulated that the Apioceridae are closely related to the Asilidae.

Dikow (2009) postulates a sister group relationship of Asilidae + (Apioceridae + Mydidae) based on a extensive morphological phylogenetic study on Asilidae. Representatives of these three taxa share the autapomorphic presence of a lateral depression on the prothoracic coxae. Based on the taxon sampling employed, this depression is only absent in Leptogastrinae among Asilidae, and Pseudonomoneura hirta among Mydidae. Additional apomorphic character states supporting the monophyly of this taxon are: clypeal-facial margin forming a distinct ridge; sensory pit in distal maxillary palpomere absent; propresternum square; upper calypter small; and female spermathecal reservoir not differentiated from spermathecal ducts (same diameter). The monophyly of a taxon composed of these three taxa is also supported by the presence of muscles M5, M33, and M38 in the male terminalia (Ovtshinnikova 1989, Ovtshinnikova & Yeates 1998) although these characters are uninformative within this clade.

Apioceridae + Mydidae form a clade supported by two autapomorphies, i.e., postgenae with medial projection and anterior ocellus separate and situated anteriorly. The single dorsal longitudinal ridge on the pulvilli could be interpreted as another autapomorphy of Apioceridae + Mydidae as suggested by Yeates & Irwin (1996) as it is only found outside of this taxon in Asilidae: Dasypogoninae: Megapodina and this is certainly an independent reduction from two ridges to one. Woodley (1989) and Yeates & Irwin (1996) found that wing veins R5 and M1 terminate anterior to the wing apex in Apioceridae and Mydidae (in some Mydidae they do not reach the wing margin at all) and this development is postulated to be an autapomorphy. This has been corroborated by the analysis of Dikow (2009) as this arrangement of veins is only found in the phylogenetically unrelated Nemestrinidae and a few Asilinae species. Woodley (1989), Yeates & Irwin (1996), and Yeates (2002) postulated the supernumerary rectal papillae as an autapomorphy of this clade. Although it appears as if it could be an important character, it has not been examined in many species. Future studies, including more Apioceridae, Mydidae, but also Asilidae, are necessary.

My own unpublished analyses of DNA sequences of a sample of Apioceridae and Mydidae are contradicting my morphological and combined morphological and molecular findings based on my phylogenetic studies on Asilidae (Dikow 2009a, Dikow 2009b). Apioceridae and Mydidae form the sister-group to Asilidae in the morphological (Dikow 2009a) and combined morphological and molecular study (Dikow 2009b) whereas Apioceridae is more closely related to Asilidae than to Mydidae in a molecular only study (molecular analysis has been presented at 6th International Congress of Dipterology in 2006, but is unpublished).

Trautwein et al. (2010) assembled the largest molecular dataset for Asiloidea and included 1 Apioceridae and 2 Mydidae species. The aim of the analysis was the placement of the enigmatic genera Apystomyia and Hilarimorpha as well as the monophyly of Asiloidea and position of Bombyliidae. In regards to Apioceridae and Mydidae the results are not entirely conclusive (compare figures 2–4), but in general a sister-group relationship between Apoceridae and Mydidae is supported and Asilidae is the most closely related taxon.