Molecular phylogeny and revision of species groups of Nearctic bombardier beetles (Carabidae, Brachininae, Brachinus ( Neobrachinus)).

Bombardier beetles of the genus Brachinus Weber are notorious for their explosive defensive chemistry. Despite ongoing research on their defense mechanism, life history, and ecology, the group lacks a robust molecular-based phylogeny. In this study, three loci from mitochondrial and nuclear genomes (COI, CAD, 28S) are used to reconstruct the phylogeny of the large subgenus Neobrachinus, and test species group boundaries hypothesized by Erwin (1970) based on morphological characters. Erwin's fumans species group is found to be polyphyletic, and is herein re-defined with eight new species groups erected to reflect clades based on molecular evidence: the cinctipennis, cyanipennis, galactoderus, gebhardis, mexicanus, phaeocerus, quadripennis, and tenuicollis species groups. Erwin's cordicollis group is also expanded to include Brachinus (Neobrachinus) medius and the americanus group.

Variation in Mating Dynamics across Five Species of Leiobunine Harvestmen (Arachnida: Opliones).

The study of mating choices often focuses on correlates of traits to the overall outcome of a mating interaction. However, mating interactions can proceed through a series of stages, with opportunities for assessment at each stage. We compared whether male or female size predicted mating interaction outcome across several stages of mating in five species of North American leiobunine harvestmen (commonly known as daddy longlegs). Leiobunine harvestmen have been previously shown to exhibit incredible morphological diversity consistent with a spectrum of male⁻female antagonism. Across all of the species, we found a general progression of female size predicting the outcome (success and timing) of early stages of interactions, and male size or male size relative to female size predicting the outcome and timing of later stages of interactions. We also found that size was not a strong predictor of outcome in the two species on the lower end of the antagonism spectrum. The variation in how female and male size predicted outcomes across species and stages of mating suggests that multiple mechanisms may operate to shape mating dynamics within and across species. Given the close relatedness of the species studied, the patterns we uncovered suggest a rapid evolution of the traits and processes predicting the outcome of mating interactions.