Abstract
Morphological and allozyme analyses suggested the occurrence of a pseudocryptic species in the Lasioglossum villosulum (Kirby, 1802) species complex (Hymenoptera: Halictidae). We analysed the morphology of more than 1500 specimens and the DNA barcode fragment of the cytochrome c oxidase subunit I (COI) of 102 specimens of this species complex from several Palaearctic countries. Our phylogenetic tree reconstructions, based on maximum likelihood and Bayesian inference revealed one clade corresponding to all specimens morphologically identified as Lasioglossum medinai (Vachal, 1895) and one divergent specimen morphologically identified as Lasioglossum berberum (Benoist, 1941). The other specimens, morphologically identified as L. villosulum, aggregated into at least three other lineages in our phylogenetic trees. The tree-based species delineations methods based on the Generalized Mixed Yule Coalescent (GMYC) model and the Bayesian Poisson Tree Process (bPTP) identified five to ten candidate species within the L. villosulum species complex, with L. medinai and L. berberum consistently recognized as separated from all other candidate species. Diagnostic morphological differences were found among L. medinai, L. berberum and the remaining specimens identified as L. villosulum. No diagnostic morphological differences were found to distinguish the different phylogenetic candidate species or lineages found within L. villosulum and L. medinai. Thus, both genetic and morphological approaches support the existence of L. medinai and L. berberum as distinct species from L. villosulum.
Highlights
Integrative taxonomy is efficient in classifying pseudocryptic species, that is, species recognizable by a few apparent, subtle, morphological criteria once their existence is revealed by other methods (Padial et al 2010; Lajus et al 2015; Kress et al 2015; Struck et al 2017)
The objective of this study is to analyse the morphology and a DNA barcode fragment of the cytochrome c oxidase subunit I (COI) gene of specimens previously identified as L. villosulum from various localities from the Palaearctic, with a focus on Europe and the Mediterranean Basin, and to evaluate if larger females collected from the south of France, Israel and Spain belong to a separate species or not
All specimens identified as L. medinai and sequenced here cluster together in all phylogenetic analyses, with a bootstrap support of 94% in the Maximum likelihood (ML) analysis, and a posterior probability of one in the Bayesian inferences
Summary
Integrative taxonomy is efficient in classifying pseudocryptic species, that is, species recognizable by a few apparent, subtle, morphological criteria once their existence is revealed by other methods (Padial et al 2010; Lajus et al 2015; Kress et al 2015; Struck et al 2017). Integrative taxonomy can contribute to synonymize species (e.g. GonzálezVaquero & Roig-Alsina 2019). The Lasioglossum villosulum (Kirby, 1802) species complex is a highly variable group of halictid bees, widespread throughout the Palaearctic (Fig. 1). The biology of L. villosulum was studied in detail by Plateaux-Quénu & Plateaux (1981, 1985, 1986, 1987, 1993), Plateaux-Quénu et al (1987), and Plateaux-Quénu (1993). These authors report the presence of larger females inhabiting the south of France (Fig. 2C, D).
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