Methods for species delimitation in bumblebees (Hymenoptera, Apidae, Bombus): towards an integrative approach

Abstract

Delimitation of closely related species is often hindered by the lack of discrete diagnostic morphological characters. This is exemplified in bumblebees (genus Bombus). There have been many attempts to clarify bumblebee taxonomy by using alternative features to discrete morphological characters such as wing shape, DNA, or eco‐chemical traits. Nevertheless each approach has its own limitations. Recent studies have used a multisource approach to gather different lines of speciation evidence in order to draw a strongly supported taxonomic hypothesis in bumblebees. Yet, the resulting taxonomic status is not independent of selected evidence and of consensus methodology (i.e. unanimous procedure, majority, different weighting of evidence). In this article, we compare taxonomic conclusions for a group of taxonomically doubtful species (the Bombus lapidarius‐group) obtained from the four commonly used lines of evidence for species delimitation in bumblebees (geometric morphometric of wing shape, genetic differentiation assessment, sequence‐based species delimitation methods and differentiation of cephalic labial gland secretions). We ultimately aim to assess the usefulness of these lines of evidence as components of an integrative decision framework to delimit bumblebee species. Our results show that analyses based on wing shape do not delineate any obvious cluster. In contrast, nuclear/mitochondrial, sequence‐based species delimitation methods, and analyses based on cephalic labial gland secretions are congruent with each other. This allows setting up an integrative decision framework to establish strongly supported species and subspecies status within bumblebees.

Ecological niche modelling and coalescent simulations to explore the recent geographical range history of five widespread bumblebee species in Europe

“…(, ) for B. terrestris , Lecocq et al . (, ) for B. lapidarius , Dellicour et al . () for B. hortorum and B. pratorum , and Lecocq et al .…”

Too strict or too loose? Integrative taxonomic assessment of Bombus lapidarius complex (Hymenoptera: Apidae)

“…Two hundred seventy‐seven specimens from the B. lapidarius complex were previously sampled for other studies (Lecocq, Dellicour, et al, ; Lecocq et al, ): B. lapidarius lapidarius (genetic analyses [GA] = 196, CLGS analyses [CA] = 174, morphological comparisons [MC] = 196), B. lapidarius decipiens (GA = 23, CA = 17, MC = 20), B. lapidarius atlanticus (GA = five, CA = zero, MC = 10), B. caucasicus (GA = 10, CA = three, MC = 13) and decipiens‐ like from South Italy (GA = 20, CA = 35, MC = 35). Specimens were killed by freezing at −20°C.…”

“…Recently, the confusing taxonomy of bumblebees (Hymenoptera: Apidae: Bombus ) has reaped the benefits of integration of several independent lines of evidence in the species delimitation framework (Bertsch, ; Bertsch, Schweer, Titze, & Tanaka, ; Lecocq, Brasero, et al, ; Lecocq, Dellicour, et al, ). While the efficiency of commonly used taxonomic diagnostic characters as components of integrative taxonomy approach has been recently assessed (Lecocq, Brasero, et al, ; Lecocq, Dellicour, et al, ), the suitability of alternative decision frameworks (i.e. integration by congruence vs. integration by cumulation) has not been investigated to date.…”

“…integration by congruence vs. integration by cumulation) has not been investigated to date. Indeed, published studies have used an integration by congruence approach leading to only strongly supported species status (Bertsch, ; Bertsch et al, ; Lecocq, Brasero, et al, ; Lecocq, Dellicour, et al, ). However, the recent bumblebee evolutionary radiation (i.e.…”

“…In this study, we investigate the taxonomic status within the Bombus lapidarius complex (Lecocq, Dellicour, et al, ; Lecocq et al, ). According to the latest taxonomic revision based on a multisource approach along with an integration by congruence decision framework (Lecocq, Dellicour, et al, ), the B. lapidarius complex includes (a) two species ( Bombus caucasicus Radoszkowski 1859 and B. lapidarius (L.)); (b) three poorly differentiated subspecies ( Bombus lapidarius atlanticus Benoist, 1928 from Maroccan Atlas, Bombus lapidarius decipiens Pérez, 1890 from Iberian peninsula and Bombus lapidarius lapidarius (L.) from the Mainland of Europe and W. Turkey); and (c) one highly differentiated taxon currently included in B. lapidarius (S. Italian and Sicilian decipiens ‐like). Bombus lapidarius includes another subspecies ( Bombus lapidarius eriophorus ) in the Caucasus but it has not been revised with a multisource approach.…”