EVOLUTIONARY ORIGIN OF THE CYCLORRHAPHA (DIPTERA): TEST OF ALTERNATIVE MORPHOLOGICAL HYPOTHESES

Area of Science:

• Entomology
• Systematics
• Evolutionary Biology

Background:

• The phylogenetic placement of higher flies (infraorder Cyclorrhapha) is a long-standing problem in dipteran systematics due to rapid morphological evolution.
• Two main hypotheses exist: Cyclorrhapha as sister to Empidoidea or within Empidoidea, with debates often focusing on male genitalia homology.

Purpose of the Study:

• To quantitatively analyze all available morphological evidence to resolve the phylogenetic origin of Cyclorrhapha.
• To evaluate the impact of different interpretations of male genitalic homology on phylogenetic placement.
• To determine if adult morphological data are sufficient to settle these systematic debates.

Main Methods:

• Cladistic analysis of morphological data, including alternative codings for male genitalic features.
• Analysis excluding genitalic features to assess their impact.
• Factorial design analog to test effects of character transformation series, outgroup choice, and successive weighting.

Main Results:

• Under all analyses, Cyclorrhapha consistently originated within Empidoidea, near the family Atelestidae.
• Constraining Empidoidea to be monophyletic resulted in trees only slightly longer, suggesting a non-significant difference.
• The debate over genitalic homology did not critically affect the placement of Cyclorrhapha.

Conclusions:

• Adult morphological data may be insufficient to definitively resolve the precise phylogenetic placement of Cyclorrhapha or the genitalic homology debate.
• The origin of Cyclorrhapha within Empidoidea is robust across different analytical manipulations, including varying genitalic interpretations.