Once upon a fly: The biogeographical odyssey of Labrundinia (Chironomidae, Tanypodinae), an aquatic non-biting midge towards diversification

Labrundinia is a highly recognizable lineage in the Pentaneurini tribe (Diptera, Chironomidae). The distinct predatory free-swimming larvae of this genus are typically present in unpolluted aquatic environments, such as small streams, ponds, lakes, and bays. They can be found on the bottom mud, clinging to rocks and wood, and dwelling among aquatic vegetation. Labrundinia has been extensively studied in ecological research and comprises 39 species, all but one of which has been described from regions outside the Palearctic. Earlier phylogenetic studies have suggested that the initial diversification of the genus likely occurred in the Neotropical Region, with its current presence in the Nearctic Region and southern South America being the result of subsequent dispersal events. Through the integration of molecular and morphological data in a calibrated phylogeny, we reveal a complex and nuanced evolutionary history for Labrundinia, providing insights into its biogeographical and diversification patterns. In this comprehensive study, we analyze a dataset containing 46 Labrundinia species, totaling 10,662 characters, consisting of 10,616 nucleotide sites and 46 morphological characters. The molecular data was generated mainly by anchored enrichment hybrid methods. Using this comprehensive dataset, we inferred the phylogeny of the group based on a total evidence matrix. Subsequently, we employed the generated tree for time calibration and further analysis of biogeography and diversification patterns. Our findings reveal multiple dispersal events out of the Neotropics, where the group originated in the late Cretaceous approximately 72 million years ago (69-78 Ma). We further reveal that the genus experienced an early burst of diversification rates during the Paleocene, which gradually decelerated towards the present-day. We also find that the Neotropics have played a pivotal role in the evolution of Labrundinia by serving as both a cradle and a museum. By "cradle," we mean that the region has been a hotspot for the origin and diversification of new Labrundinia lineages, while "museum" refers to the region's ability to preserve ancestral lineages over extended periods. In summary, our findings indicate that the Neotropics have been a key source of genetic diversity for Labrundinia, resulting in the development of distinctive adaptations and characteristics within the genus. This evidence highlights the crucial role that these regions have played in shaping the evolutionary trajectory of Labrundinia.

How ‘Gondwanan’ is Riethia? Molecular phylogenetics elucidates the mode and tempo of diversification in Austro-Pacific Chironominae (Diptera)

Riethia Kieffer, a genus of the non-biting midge subfamily Chironominae (Diptera: Chironomidae) is distributed in Australia, New Zealand, New Caledonia and South America. This austral distribution could be due to earth history (vicariance) or from Southern Hemisphere dispersal(s). We obtained samples from each area, most intensively from throughout Australia. We included putative sister genus Pseudochironomus Malloch, many genera from tribe Tanytarsini, enigmatic taxa in Chironomini and conventional outgroups from other subfamilies. We assembled a multilocus molecular dataset for four genetic regions from 107 individuals to reconstruct the first dated molecular phylogeny for the group. Four terminal clusters corresponded to unreared (thus unassociated) larvae. Monophyly was supported for ‘core’ Riethia, Pseudochironomus, putative tribe Pseudochironomini, tribe Tanytarsini (including enigmatic Nandeva Wiedenbrug, Reiss & Fittkau) and subfamily Chironominae. All species are monophyletic except for R. cinctipes Freeman, which includes R. neocaledonica Cranston. Riethia zeylandica Freeman, previously thought to be widespread in eastern Australia, now is a New Zealand endemic with Australian specimens allocated now to several regionally restricted species. The origin of Riethia was at 60.6 Ma (‘core’) or 52.1 Ma depending on the relationship of two South American species. Both dates are before the break-up of South America and Australia. Diversification within crown group Riethia started before the Cretaceous–Paleogene boundary, with subsequent separation at 52 Ma of an Australian ‘clade I’ from its sister ‘clade II’, which comprises Australian, New Zealand and New Caledonian species. Inferred dates for species origins of New Caledonia and New Zealand taxa imply transoceanic dispersals from eastern Australia. Western Australian species diverged during the mid to late Miocene from their eastern Australian sister taxa. This correlates with the onset of drying of Australia and the separation of mesic east from west by the formation of an arid proto-Nullarbor. Taken together, the inferred tempo of diversification in the group included both older ages reflecting earth history, yet with suggested recent intra-Pacific separations due to transoceanic dispersals.

Towards a dated molecular phylogeny of the Tanypodinae (Chironomidae, Diptera)

A dated molecular phylogeny is proposed for the Tanypodinae, a diverse subfamily of Chironomidae (Diptera). We used molecular data from fragments of one ribosomal gene (28S), one nuclear protein-coding gene (CAD), and one mitochondrial protein-coding gene (COI), analysed using mixed model Bayesian and maximum likelihood inference methods. All proposed tribes were sampled, namely, Anatopyniini, Clinotanypodini, Coelopyniini, Fittkauimyiini, Macropelopiini, Natarsiini, Pentaneurini, Procladiini and Tanypodini. A multilocus dataset of 1938 characters was compiled from 123 individuals including outgroups. Monophyly was supported for all tribes although some relationships were not robust. Relationships between tribes and some genus groups are highly congruent with a morphology-based estimate. Relationships within tribe Pentaneurini mostly find weak support, yet previously hypothesised groupings and monophyly or lack thereof in well-sampled genera are revealed. The tempo of diversification of the family was deduced by divergence time analysis (BEAST). Origination of a subfamily stem group in the late Jurassic to early Cretaceous was inferred, with all tribes and many genera of Pentaneurini originating and diversifying in the Cretaceous. Some nodes are biogeographically informative. Gene sections supported the backbone, but more extensive sampling is needed to estimate shallower phylogenies and to better understand the tempo and diversification of Tanypodinae.