EXPLORATION OF MESOPSYCHIDAE PHYLOGENY AND THE ORIGIN OF THE SIPHONATE PROBOSCIS IN EARLY MECOPTERA

Mecoptera is a nonspeciose order of insects. This group currently consists of 38 extant genera in 9 families and about 39 families and 207 genera as fossils. Within Mecoptera, Mesopsychidae and the three other families of Aneuretopsychidae, Pseudopolycentropodidae and Nedubroviidae form a major clade, Aneuretopsychina, which have elongate, siphonate proboscides, and likely fed on gymnosperm pollination drops. The Aneuretopsychina ranges from Upper Permian to Lower Cretaceous and family-level phylogenetic relationships are established.

Nevertheless, phylogenetic relationships of genera within Aneuretopsychina and the origins of their elongate, siphonate proboscises lack formal examination, attributable to the limited number of well-preserved fossils. Based on data from two new and previously described Mesopsychidae species and a suite of unique morphological characters, phylogenetic analyses and geometric morphometric analyses were done to shed light on the taxonomy, classification and phylogeny of Mesopsychidae genera.

Our analyses provided four results. First, phylogenetic relationships establishes Mesopsychidae as a monophyletic group and the validity of the two new species. Second, phylogenetic and geometric morphometric analyses indicate a need for taxonomic revision of Mesopsyche. Third, the long-proboscid condition likely originated independently four or five times within the early Mecoptera. Fourth, repeated rounds of suppression of ext and hth genes could explain initial proboscis development in early Mecoptera.

Additional specimens of Pseudopolycentropodidae and Mesopsychidae were collected from Myanmar Amber, revealing well-preserved proboscides and other features differing from related species. These specimens provide new data for the origin of this specialized mouthpart type. Future discovery and examination of mouthpart structure in both fossil and amber specimens will augment understanding of the origin of early Mecoptera and their siphonate proboscides.