Short‐range phenotypic divergence among genetically distinct parapatric populations of an Australian funnel‐web spider

Abstract

Speciation involves divergence at genetic and phenotypic levels. Where substantial genetic differentiation exists among populations, examining variation in multiple phenotypic characters may elucidate the mechanisms by which divergence and speciation unfold. Previous work on the Australian funnel-web spider Atrax sutherlandi Gray Atracinae) has revealed a marked genetic structure along a 110-kilometer transect, with six genetically distinct, parapatric populations attributable to past glacial cycles.In the present study, we explore variation in three classes of phenotypic characters (metabolic rate, water loss, and morphological traits) within the context of this phylogeographic structuring. Variation in metabolic and water loss rates shows no detectable association with genetic structure; the little variation observed in these rates may be due to the spiders' behavioral adaptations (i.e., burrowing), which buffer the effects of climatic gradients across the landscape. However, of 17 morphological traits measured, 10 show significant variation among genetic populations, in a disjunct manner that is clearly not latitudinal. Moreover, patterns of variation observed for morphological traits serving different organismic functions (e.g., prey capture, burrowing, and locomotion) are dissimilar. In contrast, a previous study of an ecologically similar sympatric spider with little genetic structure indicated a strong latitudinal response in 10 traits over the same range. The congruence of morphological variation with deep phylogeographic structure in Tallaganda's A. sutherlandi populations, as well as the inconsistent patterns of variation across separate functional traits, suggest that the spiders are likely in early stages of speciation, with parapatric populations independently responding to local selective forces. K E Y W O R D Sfunctional traits, mygalomorph, phylogeography, physiology, speciation, Tallaganda

Morphometric Analysis of a Trapdoor Spider (Araneae, Idiopidae) across Different Brazilian Biomes Reveals the Geographic Variation of Spiders from the Caatinga Biome

“…To explore the variation in the linear structures in relation to each biome, nine measurements of different body parts were taken: the carapace length (CL), carapace width (CW), sternum length (SL), sternum width (SW), leg 1 length (LL1), leg 2 length (LL2), leg 3 length (LL3), leg 4 length (LL4), and the pedipalp length (PpL) (Figure 2A-C). The definition of the linear measurements used was based on the structures that showed morphological variation among different groups of spiders in previous morphometric studies [28,35,36].…”

“…To explore the variation in the linear structures in relation to each biome, nin measurements of different body parts were taken: the carapace length (CL), carapa width (CW), sternum length (SL), sternum width (SW), leg 1 length (LL1), leg 2 leng (LL2), leg 3 length (LL3), leg 4 length (LL4), and the pedipalp length (PpL) (Figure 2A-C The definition of the linear measurements used was based on the structures that showe morphological variation among different groups of spiders in previous morphometr studies [28,35,36]. In addition to linear measurements, to detect geometrically significant variations specimens in relation to biomes, geometric morphometric analysis was performed base on images of the dorsal copulatory bulb (Figure 2D), the sternum (Figure 2B), and the e arrangement (Figure 2E).…”

“…In spiders, few studies have explored morphometric variation throughout the range of a species [22][23][24][25][26][27][28]. The majority of the existing morphometric studies are focused on species delimitation and on the investigation of sexual dimorphism [22][23][24][28][29][30][31][32][33][34].…”

“…In spiders, few studies have explored morphometric variation throughout the range of a species [22][23][24][25][26][27][28]. The majority of the existing morphometric studies are focused on species delimitation and on the investigation of sexual dimorphism [22][23][24][28][29][30][31][32][33][34]. There are also some studies that focus on habitat preference and foraging ecology [35,36], and others that investigate the morphological variation of specific structures in a phylogenetic context [36][37][38][39].…”

“…There are also some studies that focus on habitat preference and foraging ecology [35,36], and others that investigate the morphological variation of specific structures in a phylogenetic context [36][37][38][39]. Despite the diversity of approaches, morphometric analyses based on multivariate and morphogeometric data have only been applied to Mygalomorph spiders one a few occasions [28,29,[38][39][40].…”