Novel splitting/lumping index reflects the history of species concepts applied to bumblebees (Insecta: Apidae)

Abstract

Splitting or lumping of species is a concern because of its potential confounding effect on comparisons of biodiversity and on conservation assessments. By comparing global lists of species reported by previous authors to lists of the presently recognized species that were known to those authors, a simple ratio can be used to describe their relative splitting or lumping of species. One group of ‘model’ organisms claimed for the study of what species are and how to recognize them is bumblebees. A comparison of four bumblebee subgenera shows: (1) an early phase (up to and including 1931) showing splitting, in which taxonomy was dominated by a typological concept of invariant species with heavy reliance on colour-pattern characters; (2) a middle phase (1935–98) showing lumping, associated with a shift to a polytypic concept of species emphasizing morphological characters, often justified with an interbreeding concept of species, but only rarely associated directly with process-related characters; and (3) a recent phase (after 2000), using a concept of species as evolutionarily independent lineages, as evidenced by corroboration from integrative assessment, usually including evidence for coalescents of species in fast-evolving genes compared with morphology. Analysis of splitting or lumping should help to improve biodiversity comparisons and conservation.

Linnean shortfall and space‐time patterns in species description of New World coralsnakes (Serpentes: Elapidae)

“…The second category of the Linnean shortfall can encompass species that range from undescribed ones, but with specimens already housed in scientific collections, to changes in taxonomic practice that may split one species into two (or more) or lump two (or more) species under a single scientific name (Diniz‐Filho et al., 2023; Hortal et al., 2015; Walters et al., 2021; Williams, 2022). Many undescribed species of coralsnakes may also be present in this second category.…”

“…The tendency shown for more recently described species to have smaller geographic range sizes can also be a consequence of changes in taxonomic practice and criteria for species delimitation, including the use of more refined information at the molecular level (e.g. Walters et al., 2021; Williams, 2022). Species with large geographic ranges can be subsequently revised, and one or more of their populations can be recognized as full species.…”

Macroecological links between the Linnean, Wallacean, and Darwinian shortfalls

“…The uneven taxonomic uncertainty leads to unmeasured errors in diversification rates that can have a cascading impact on our understanding of how diversification rates relate to other aspects of biodiversity (e.g., species richness). To decrease these biases in diversification rates, it is important to consider the history of taxonomic progress for the taxa involved (Stropp et al 2022) by evaluating the variation of valid species through time (Alroy 2002;Williams 2022). The probability of splitting or lumping a valid species in the future can be estimated by simulations (see below) that would allow the total number of species predicted under multiple simulations to match the overall number of species predicted by species accumulation curves (Diniz-Filho et al 2005;Lobo and Martín-Piera 2002;Lobo et al 2007) or the application of SAR/ SAD (species-area relationships/species abundance distributions) analyses (ter Steege et al 2020).…”

Bumblebees of the hypnorum-complex world-wide including two new near-cryptic species (Hymenoptera: Apidae)

“…Bumblebees are some of the most intensively studied and well-known insects globally and yet new species continue to be discovered (patterns reviewed by Williams 1998;2022b). Some of the most widespread bumblebee species within Europe and Asia have in the last decade been examined for genetic variation across their ranges (Dellicour et al , 2017Lecocq et al 2016;Martinet et al 2021).…”