Integrative species delimitation in Nearctic ambush bugs (Heteroptera: Reduviidae: Phymatinae): insights from molecules, geometric morphometrics and ecological associations

Abstract

Ambush bugs (Hemiptera: Reduviidae: Phymatinae) are sit‐and‐wait predators of flower‐visiting insects including pollinators. Broad species distribution ranges, intraspecific polymorphism, sexual dimorphism and subtle interspecific differences all contribute to making species delimitation especially difficult in this group, which is used as a model in the study of interactions between sexual dimorphism and sexual selection. Species boundaries among Nearctic ambush bugs in the common and frequently collected erosa species group (11 species, nine subspecies) have therefore remained unclear, resulting in a complex and poorly justified taxonomy. Recent molecular phylogenetic research suggested that several widespread Nearctic species are para‐ or polyphyletic. We here build on this research, integrating geometric morphometrics, molecular species delimitation approaches and host plant association data to provide a comprehensive dataset with respect to both taxon and character sampling with the goal of teasing apart evolutionary lineages of Nearctic Phymata Latreille. Although molecular‐based species delimitation analyses suggested a variety of species hypotheses, probably as a result of striking discordance between mitochondrial and nuclear ribosomal genes, the combination of these with geometric morphometric data enabled us to confidently delimit several of these problematic taxa. In addition, geometric morphometric analysis of pronotal shape revealed undocumented morphological patterns that appear to be useful in the diagnosis of many of the surveyed taxa. The results from this study provide an objective foundation for the much‐needed taxonomic revision of the most ubiquitous ambush bugs in North America.

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“…The P. fasciata treated by Kormilev (1962) included three subspecies in addition to the nominate. Two of these subspecies, P. fasciata mexicana and P. fasciata mystica are elevated here to species rank based on differences in their morphology and molecular evidence (see Masonick and Weirauch, 2020). The remaining subspecies, Phymata fasciata panamensis Kormilev, 1962 from Panama, is herein synonymized with P. mexicana.…”

“…Taxonomic descriptions: Descriptions were partially produced using a WinClada v1.61 (Nixon 1999) based character matrix and then manually edited to accommodate variability and any unique traits for each species. Outlines displaying the consensus pronotal shape were generated following the geometric morphometric approach outlined in Masonick and Weirauch (2020) and are included for each sex in all taxon plates. The curvature of the pronotal lobes are best viewed from a dorsolateral perspective with the lateral margin placed roughly perpendicular to the optical axis.…”

“…Discussion: This striking species is rarely encountered in the wild and represented by relatively few specimens in entomological collections. Based on molecular data, P. arctostaphylae appears to be very closely related to other western members of the americana species complex (i.e., P. metcalfi and P. obscura) (Masonick and Weirauch, 2020).…”

“…Discussion: Phymata borica morphologically resembles two other species that are found elsewhere in the southwestern United States, P. luteomarginata and P. paraborica sp. nov., and is closely related to P. rossi, a species with which it is sympatric (Masonick and Weirauch, 2020).…”

“…Outdated descriptions and keys, the most recent having been published in 1962, have culminated in numerous specimens in natural history collections being mis-or unidentified. While little has been done to modernize ambush bug taxonomy, molecular phylogenetics and integrative species delimitation have recently shed light on their specieslevel relationships and revealed that several erosa group taxa are para-or polyphyletic (Masonick et al 2017;Masonick and Weirauch 2020). Taxonomic updates are sorely needed and insights from these analyses have helped structure the present revision.…”