Grappling with homoplasy: taxonomic refinements and reassignments in the ant genera Camponotus and Colobopsis (Hymenoptera: Formicidae)

Philip S Ward,Brendon E Boudinot

doi:10.3897/asp.79.e66978

Abstract

Camponotus and Colobopsis are widely distributed and species-rich genera in the ant tribe Camponotini. Molecular phylogenetic studies demonstrate that they are not sister taxa, but several lineages within each genus have converged to a remarkable degree, confounding the taxonomy of these ants. Based on multiple lines of evidence, including worker and male morphology, we demonstrate that: (1) three species of “Camponotus” belonging to the subgenus Myrmotemnus, including its type species, are in fact members of the genus Colobopsis; (2) four species previously assigned to Colobopsis belong to the subgenus Myrmamblys of Camponotus; and (3) three Nearctic taxa recently placed in Colobopsis are members of the genus Camponotus and closely related to Camponotus clarithorax. These taxonomic findings yield the following new or revived combinations: Colobopsis moeschi (comb. nov.), Colobopsis moeschi lygaea (comb. nov.), Colobopsis nutans (comb. nov.), Colobopsis nutans cleliae (comb. nov.), and Colobopsis reichenspergeri (comb. nov.); Camponotus apostemata (comb. nov.), Camponotus aurelianus (comb. rev.), Camponotus cavibregma (comb. nov.), Camponotus horrens (comb. rev.), Camponotus politae (comb. rev.), Camponotus trajanus (comb. rev.), and Camponotus yogi (comb. rev.). A further consequence is the following generic synonymy (senior synonym listed first): Colobopsis = Myrmotemnussyn. nov., and Camponotus = Dolophrasyn. rev. At the species level, we argue that Camponotus apostemata and Camponotus cavibregma are junior synonyms (syn. nov.) of Camponotus yogi, and Camponotus quercicola is a junior synonym (syn. nov.) of Ca. laevigatus. Taxonomic comments are also provided on some members of the Camponotus reticulatus group, with Camponotus adustus (stat. nov.) and Ca. leucodiscus (stat. rev.) being recognized as distinct species rather than subspecies of Ca. bellus. A male-based diagnosis of the Camponotini is provided, and differences between the males of Colobopsis and Camponotus are documented and illustrated for the first time. This study reveals new character systems of potential value to the systematics of these ants, including features of the male genitalia, and emphasizes the value of reciprocal illumination between phylogenomics and critical morphological analysis.

Highlights

Evolution is a heterogeneous process, occurring at variable rates in different lineages (Simpson 1953) and across different body structures (Hennig 1957)
Large ant clades often contain a mixture of slower-evolving species that appear to have retained many original characteristics as well as highly divergent taxa that have evolved to the point where certain ancestral features are lost or indiscernible. Examples of this pattern include the “army ants” within the subfamily Dorylinae (Borowiec 2019), numerous genera of the Ponerinae (Schmidt 2013, Schmidt and Shattuck 2014), and social parasites in the Myrmicinae (Rabeling et al 2014, Ward et al 2015, Prebus 2017). In addition to this variable rate of evolutionary divergence, ants show a strong propensity for convergent evolution of certain features in the worker caste, with respect to defensive traits such as spines (Blanchard and Moreau 2017), morphology of the major worker (Hölldobler and Wilson 1990), and chemical weaponry (Hermann and Blum 1981)
In effecting these changes in generic assignment, we are guided by the differences in worker morphology uncovered in Ward et al (2016), which are corroborated by character differences in the larvae and pupae, and by molecular phylogenetic data (Wernegreen et al 2009, Blaimer et al 2015, Clouse et al 2015)

Summary

Introduction

Evolution is a heterogeneous process, occurring at variable rates in different lineages (Simpson 1953) and across different body structures (Hennig 1957). Examples of this pattern include the “army ants” within the subfamily Dorylinae (Borowiec 2019), numerous genera of the Ponerinae (Schmidt 2013, Schmidt and Shattuck 2014), and social parasites in the Myrmicinae (Rabeling et al 2014, Ward et al 2015, Prebus 2017) In addition to this variable rate of evolutionary divergence, ants show a strong propensity for convergent evolution of certain features in the worker caste, with respect to defensive traits such as spines (Blanchard and Moreau 2017), morphology of the major worker (Hölldobler and Wilson 1990), and chemical weaponry (Hermann and Blum 1981). These evolutionary dynamics pose considerable challenges to ant systematics and, in Arthropod Systematics & Phylogeny 79, 2021, 37–56 particular, to the establishment of a ranked, phylogenetic classification (Ward 2011)

Methods

Results

Conclusion