Ecological Specialization in Predatory Lasiopogon Robber Flies and its Role in Facilitating Diversification and Species Coexistence

Abstract

Nearctic species of Lasiopogon Loew (Diptera: Asilidae) assigned to the bivittatus group by Cannings 2002 are revised, with the description of 13 new species, elevation of 1 subspecies to species, and redescriptions of 13 previously described taxa. Keys to adults are updated, notes on taxonomy, distribution, and ecology are provided, and a Bayesian species tree for 67 species of Lasiopogon is estimated from one mitochondrial (COI) and three nuclear protein-coding loci (AATS, PEPCK, wingless), and compared to the previous phylogeny. The following new species of Lasiopogon are described: L. anaphlecter sp. nov., L. apoecus sp. nov., L. asilomar sp. nov., L. bitumineus sp. nov., L. canningsi sp. nov., L. condylophorus sp. nov., L. esau sp. nov., L. karli sp. nov. (assigned to cinereus group of opaculus section), L. nelsoni sp. nov., L. odontotus sp. nov., L. sierra sp. nov., L. tumulicola sp. nov., L. wilcoxi sp. nov.; L. puyallupi Cole & Wilcox 1938 stat. nov. is elevated from subspecies. Stackelberginia Lehr is proposed as the sister taxon to Lasiopogon based on morphological and genetic evidence, and Stackelberginia cerberus sp.n. is described from the Nevada desert (USA) and compared to congeners. The ecology of 59 Nearctic Lasiopogon species is characterized from museum specimens and field observations, and trait divergences for sympatric and allopatric species are compared. Subclades of the Lasiopogon tree reveal signatures of different ecological processes: the bivittatus and opaculus groups show character displacement for seasonal phenology and perch behavior and environmental filtering for habitats; while species from the other half of the phylogeny show no significant associations with those environmental traits but do have a strong correlation with color. Allopatric species pairs have weaker trait associations than sympatric species pairs, supporting the hypothesis that competitive interactions are shaping ecological divergence in these taxa. Bioclimatic variables do not provide meaningful resolution of species niche differences. Given the complexity of trait divergence in Lasiopogon flies, evolution is likely proceeding along multiple niche axes which require more complex data collection and modeling to reasonably understand.