Geometric morphometric analyses of sexual dimorphism and allometry in two sympatric snakes: Natrix helvetica (Natricidae) and Vipera berus (Viperidae)

Abstract

The non-venomous grass snake (Natrix helvetica) and the venomous adder (Vipera berus) are two native species that are often found in sympatry in Great Britain and Europe. They occupy partially overlapping ecological niches and prey on small vertebrates, but use different feeding strategies. Here, we investigated the morphologies of grass snakes and adders from Dorset (UK) using two-dimensional geometric morphometrics to assess the degree of sexual dimorphism in size and shape together with the relative impact of allometry and general body dimensions on head shape. Both species showed significant sexual dimorphism in head size, but not in head shape. We found a clear allometric pattern in N. helvetica, whereas allometry in V. berus was generally less pronounced. Body dimensions were strongly correlated with head shape in the grass snake, but not in the adder. The fact that V. berus is venomous appears to explain the lack of allometric patterns and the lack of an association between body dimensions and head shape. The high degree of size dimorphism identified in both species could originate from the advantages of reduced intraspecific competition that are conveyed by a partial differentiation in feeding morphology.

Sexual dimorphism in the Anatolian endemic tiger beetle, Cephalota circumdata cappadocica Franzen, 1996 (Coleoptera: Carabidae: Cicindelinae): a study showing the effectiveness of geometric morphometrics

“…Methods for the selection and use of body parts, and for the evaluation of sexes, are of central importance in sexual dimorphism. Geometric morphometrics is not only a novel tool for detecting morphological variations (Mitteroecker & Gunz, 2009;Breno et al, 2011;Kaliontzopoulou, 2011;Benítez et al, 2013;Meng et al, 2018), but also is the best clue to determine sexual dimorphism between and/or among organisms (Hood, 2000;Kaliontzopoulou et al, 2007;Moneva et al, 2012;Alencar et al, 2014;Jun-Yan et al, 2015;Solis et al, 2015;Minoli et al, 2016;Benítez & Vargas, 2017;Tamagnini et al, 2018). For insects in general, and beetles in particular, past works on sexual dimorphism have concentrated on sclerotized body parts (Pretorius & Scholtz, 2001), such as head and pronotum (Torres et al, 2010;Cruz et al, 2011;Acevedo, 2015;Ober & Connolly, 2015;Eldred et al, 2016;Sukhodolskaya & Saveliev, 2017;Vesović et al, 2019).…”

Geometric morphometric study of sexual dimorphism and its associated allometry in wings of Pelopidas thrax (Lep.: Hesperiidae)

“…Zelditch, personal communication). Therefore, a multivariate Procrustes ANOVA which is particularly useful for shape data was carried out as a nonparametric permutational-MANOVA by the R package geomorph v. 3.0.4, using procD.lm (Adams & Otarola-castillo, 2013;Sherratt, 2016;Tamagnini et al, 2018).…”

Morfometría Geométrica y sus Nuevas Aplicaciones en Ecología y Biología Evolutiva. Parte 2

“…Los estudios de integración morfológica y modularidad difieren de los análisis de redes en otros contextos, porque las interacciones responsables de la integración no son directamente observables y, en cambio, deben inferirse a partir de los patrones de covariación entre rasgos. Debido a esta razón, la modularidad ha sido temática de particular relevancia en la última década, en especial en estudios de evolución del desarrollo, donde varios autores argumentan que proporciona la flexibilidad suficiente para que diferentes rasgos evolucionen más fácilmente bajo demandas funcionales diferentes y/o contrastantes (Andjelkovic et al;Asahara, 2013;Goswami & Polly, 2010;Lehoux & Cloutier, 2015;Maga et al, 2017;Maiorino et al;Randau & Goswami, 2017, 2018Simons et al, 2018;Stefanello et al;Tamagnini et al, 2018;Zollikofer et al). Por consiguiente, la delimitación de módulos a partir de datos sobre patrones de covariación es una preocupación clave para la evolución del desarrollo de la forma (Klingenberg, 2010).…”