Distribution and predictors of wing shape and size variability in three sister species of solitary bees

Abstract

Morphological traits can be highly variable over time in a particular geographical area. Different selective pressures shape those traits, which is crucial in evolutionary biology. Among these traits, insect wing morphometry has already been widely used to describe phenotypic variability at the inter-specific level. On the contrary, fewer studies have focused on intra-specific wing morphometric variability. Yet, such investigations are relevant to study potential convergences of variation that could highlight micro-evolutionary processes. The recent sampling and sequencing of three solitary bees of the genus Melitta across their entire species range provides an excellent opportunity to jointly analyse genetic and morphometric variability. In the present study, we first aim to analyse the spatial distribution of the wing shape and centroid size (used as a proxy for body size) variability. Secondly, we aim to test different potential predictors of this variability at both the intra- and inter-population levels, which includes genetic variability, but also geographic locations and distances, elevation, annual mean temperature and precipitation. The comparison of spatial distribution of intra-population morphometric diversity does not reveal any convergent pattern between species, thus undermining the assumption of a potential local and selective adaptation at the population level. Regarding intra-specific wing shape differentiation, our results reveal that some tested predictors, such as geographic and genetic distances, are associated with a significant correlation for some species. However, none of these predictors are systematically identified for the three species as an important factor that could explain the intra-specific morphometric variability. As a conclusion, for the three solitary bee species and at the scale of this study, our results clearly tend to discard the assumption of the existence of a common pattern of intra-specific signal/structure within the intra-specific wing shape and body size variability.

Landscape genetic analyses of Cervus elaphus and Sus scrofa: comparative study and analytical developments

“…After the first MRDM/ LR-CA analyses, total suppressors were identified and discarded in a series of successive MRDM/LR-CA analyses, until all the suppressors were removed . A predictor may be considered a total suppressor when its unique contribution is counterbalanced by its (negative) common contribution (classical suppression) or when its regression coefficient and its correlation coefficient are of opposite signs (cross-over suppression; Paulhus et al 2004;Prunier et al 2017): it shares no or little variance with the response variable but is responsible for artefactual relationships among variables due to the removal of the irrelevant variance in other (suppressed) predictors. Discarding such suppressor variables can potentially purify the relationship between remaining predictors and the response variable (Prunier et al 2017).…”

Morphometric Variability among Populations of Euglossa cordata (Hymenoptera: Apidae: Euglossini) from Different Phytophysiognomies

“…These authors reported the high morphological similarity between populations with the high dispersal potential of these bees. The wing shape variability may be related to factors such as genetic control, sexual selection and environmental heterogeneity (Dellicour et al, 2017). Euglossini bees present some ecological requirements that are scattered in the landscape (Roubik & Hanson, 2004).…”

“…However, some studies verified the efficacy of morphological characters in males to identify morphotypes and cryptic species of the genus Euglossa (Francoy et al, 2012;Quezada-Euán et al, 2015), demonstrating the importance of using males in morphometric studies. Geometric morphometrics, the study of shape and size associated with random factors (Monteiro & Reis, 1999;Klingenberg, 2015), has been used as a tool for studies on intra and interpopulation variation in social bees species (Mendes et al, 2007;Prado-Silva et al, 2016;Combey et al, 2018) and solitary bees (Ferreira et al, 2011;Neves et al, 2012;Dellicour et al, 2017;Grassi-Sella et al, 2018). Such studies have shown the efficacy of that technique on understanding phenotypic expression of these insect populations associated to different environmental factors, such as altitude, geographic distribution, vegetation type and habitat fragmentation.…”

Morphological variation and strain identification of insects using wings and I3S

“…It also occurs in species that experience different environmental conditions to their siblings living elsewhere. Termed 'ecological variation' it has been documented in many organisms including insects (Yi Bai et al 2016, Suman et al 2009, Dellicour et al 2017, Ekgachai et al 2013.…”