Molecular phylogenetics of the bristle fly tribe Rutiliini, (Diptera: Tachinidae)

Abstract

This study examines the phylogeny of the bristle-fly tribe Rutiliini (Diptera:Tachinidae:Dexiinae), focusing on the genus Rutilia R-D. Chapter 1 reviews the higher level systematics of Tachinidae, outlining its morphological and biological characteristics. Chapter 2 examines the systematics of Rutiliini and its biological and behavioural aspects, before testing the morphology-based classification of Crosskey (1973) against a molecular phylogeny based on an informative and representatively sampled nuclear dataset. To generate the data set, extensive fieldwork was conducted across Australia in order to secure the high-quality molecular samples required for Anchored Hybrid Enrichment. A total of 94 Australasian tachinid specimens from at least 36 genera were sequenced. A final 503-locus dataset was used for the phylogenetic analyses using summary-coalescence methods, as well as for concatenation-based phylogenetic analyses in a maximum-likelihood framework. This data set for 121 taxa was 71% complete for 503 loci that comprised alignments of 483,060 nucleotide or 161,020 amino acid sites, respectively. Inferred phylogenies from the 121-taxon dataset were congruent in their overall structure across species trees with the majority of branches well supported. These analyses clarified phylogenetic relationships from diverse outgroup taxa to ingroup Rutiliini. All analyses recovered a monophyletic Rutiliini with maximum support values in all species trees. Most internal branches in this part of the phylogeny were consistently well supported and topologically congruent across species trees. Among the sampled Rutiliini genera, Amphibolia Macq., Chetogaster Macq., Chrysopasta Brauer & Bergenstamm and Prodiaphania Townsend were all consistently supported as clades based on their sampled taxa. In contrast, both genera Formosia Guerin-Meneville and Rutilia R-D were consistently reconstructed as non-monophyletic taxa. However, the monophyly of most of their subgenera was consistently supported, with the exception of the nominotypical subgenus of Rutilia. The genus Rutilodexia Townsend was only represented by a single undetermined PNG species, and the monospecific Formodexia Crosskey was the only rutiliine genus not represented. This study presents the most detailed molecular phylogeny of Australian Dexiinae and provides the first phylogenetic hypotheses on the evolutionary relationships within the tribe Rutiliini. The results are largely congruent with, the phylogenies of Stireman et al., (2019) and de Paula et al., (2024). This study strongly supports the paraphyly of Dexiini relative to Rutiliini and the need to move the tribe Myiotrixini from Tachininae to Dexiinae. It also demonstrates that the genus Rutilia does not reflect a natural or tenable grouping. Some subgenera should be elevated to genus level, and others should be grouped together into new genera or be combined with existing genera other than Rutilia. The monophyly of most of the morphology-based subgenera of Crosskey (1973a) is strongly supported. However, the most unexpected difference to this classification (Crosskey 1973a) is that the nominotypical subgenus Rutilia s.s. is not monophyletic as currently defined. Chapter 3 provides a summary and some potential systematic and biological research directions. Additional molecular and morphological evidence is needed to support formal taxonomic changes. This study will contribute to the classification of the various sampled unnamed taxa, which are being formally described in a future publication. Future molecular studies should ideally represent key unsampled taxa, i.e. the genus Formodexia, subgenera Formosia (Pseudoformosia) and Rutilia (Neorutilia), and representatives Crosskey's of R. (Chrysorutilia) luzona and F. (Formosia) viridiventris species groups. Show more