Geometric morphometrics of the forewing shape and size discriminate Plebeia species (Hymenoptera: Apidae) nesting in different substrates

Abstract

Historically, studies evaluating morphological diversity in stingless bees (Hymenoptera, Apidae: Meliponini) by geometric morphometrics have been used to successfully discriminate taxa and/or populations. Moreover, the use of geometric morphometrics to evaluate phylogenetic morphological variation among stingless bee species has received less attention. Here, we used geometric morphometrics to assess taxonomic discrimination and putative phylogenetic signals for six diapausing stingless bee species (Plebeia) occurring in southern Brazil. In all, 12 landmarks were captured from forewings of P. droryana, P. saiqui, P. emerina, P. remota, P. nigriceps and P. wittmanni. Our data show that the centroid size of the forewings reliably discriminated, for example, between P. droryana and P. emerina from P. saiqui. Moreover, this trait does not have a significant phylogenetic signal. In turn, we found that the overall accuracy in discriminating between the six Plebeia species according to forewing shape was 84%, while the confusion matrix achieved 71%. Interestingly, our discriminant analysis separated Plebeia species nesting in tree cavities from those nesting under granitic rocks. The latter group has second cubital (landmarks = 5, 6, 7), first medial (landmarks = 2, 3, 8) and first submarginal cells (landmarks = 3, 4, 9, 10) that are larger than those of species nesting in trees. The forewing shape showed a strong phylogenetic signal, therefore suggesting that its variation may be due to an evolutionary history shared between Plebeia species studied here rather than to environmental features. This work sheds light on the value of forewing size and shape attributes in discriminating Plebeia species within same genus. We suggest that landmarks separating different taxonomic groups could be incorporated into dichotomous keys to help in identifying clades of complex resolution.

Species morphospace boundary revisited through wing phenotypic variations of Antodynerus species (Hymenoptera: Vespidae: Eumeninae) from the Indian subcontinent

“…This insight opens the door to further research into the environmental, developmental, behavioral, and genetic factors contributing to such disparities (Villemant et al, 2007). The landmarks (used in our study to distinguish potter wasps) that successfully differentiated the closely related taxonomic group (i.e., congeneric species) could be incorporated into dichotomous keys to help in the identification of clades of complex resolution (dos Santos et al, 2019).…”

“…In fact, the forewing shape is becoming more popular in systematics since it can help to resolve many taxonomic problems (Dehon et al, 2014;Perrard et al, 2014). In previous GM analyses of wasps (Pretorius, 2005;Mitrovski Bogdanović et al, 2009;Baracchi et al, 2011;Perrard et al, 2016;Žikić et al, 2017;dos Santos et al, 2019), less than 20 landmarks in the forewing were identified and employed for GM analysis. In our studies, we used the maximum number of landmarks (forewing with 26 landmarks and hindwing with nine landmarks), which represents a large number of shape variables.…”

“…Phylogenetic signal analysis is very rare in hymenopteran groups, so this is the first study report on Eumeninae phylogenetic signal analysis. dos Santos et al (2019) used the GM to decipher the taxonomic relationship and phylogenetic signal of six diapausing stingless bee species (Plebeia) occurring in southern Brazil. The authors discovered no phylogenetic signal in forewing centroid size, as well as the existence of a significantly strong phylogenetic signal in the forewing shape of Plebeia species.…”

An integrative approach to delimit species in the Eulaema cingulata and Eulaema pseudocingulata pair (Hymenoptera: Apidae) using morphometric and molecular evidence

“…Morphometric and molecular approaches have been successfully applied in studies of bees' biogeography, systematic and evolution (Quezada-Euán et al, 2007;Quezada-Euán et al, 2015;Santos et al, 2019). However, there are relatively few studies using integrative taxonomy to assess the relationships and species thresholds in euglossine bees.…”