The evolution of coloration and opsins in tarantulas

Abstract

Tarantulas paradoxically exhibit a diverse palette of vivid coloration despite their crepuscular to nocturnal habits. The evolutionary origin and maintenance of these colours remains mysterious. In this study, we reconstructed the ancestral states of both blue and green coloration in tarantula setae, and tested how these colours correlate with presence of stridulation, urtication and arboreality. Green coloration has probably evolved at least eight times, and blue coloration is probably an ancestral condition that appears to be lost more frequently than gained. While our results indicate that neither colour correlates with the presence of stridulation or urtication, the evolution of green coloration appears to depend upon the presence of arboreality, suggesting that it ptobably originated for and functions in crypsis through substrate matching among leaves. We also constructed a network of opsin homologues across tarantula transcriptomes. Despite their crepuscular tendencies, tarantulas express a considerable diversity of opsin genes—a finding that contradicts current consensus that tarantulas have poor colour vision on the basis of low opsin diversity. Overall, our findings raise the possibility that blue coloration could have ultimately evolved via sexual selection and perhaps proximately be used in mate choice or predation avoidance due to possible sex differences in mate-searching.

Phylogenomic analyses reveal a Gondwanan origin and repeated out of India colonizations into Asia by tarantulas (Araneae: Theraphosidae)

“…Mygalomorph spiders from the family Theraphosidae, also known as tarantulas, are also useful models for understanding biogeographic patterns. They possess several intriguing adaptations that have received significant attention in recent years, such as their stridulatory capacity ( Galleti-Lima & Guadanucci, 2018 ; Galleti-Lima & Guadanucci, 2019 ), urticating bristle evolution ( Bertani, 2003 ; Kaderka et al, 2019 ; Foley et al, 2019 ), colouration ( Foley, Saranathan & Piel, 2020 ), and venom compositions ( Santana et al, 2017 ; Lüddecke, Vilcinskas & Lemke, 2019 ). Robust, subfamily-level phylogenies are late in coming ( Lüddecke et al, 2018 ; Foley et al, 2019 ), but these phylogenies have verified the monophylies of all studied subfamilies, except Ischnocolinae (with Selenogyrinae being the only subfamily not represented by these studies).…”

Phylogenomics and loci dropout patterns of deeply diverged Zodarion ant‐eating spiders suggest a high potential of RAD‐seq for genus‐level spider phylogenetics

“…Most of these studies have focused on deep to intermediate levels of divergence and have helped to disentangle the evolution of spider webs (Bond et al, 2014;Fern andez et al, 2014;Kallal et al, 2021) and that of their silk glands and respiratory systems (Ram ırez et al, 2021). In particular spider groups, phylogenomic studies have also led, for example, to unraveling the evolution of sexual dimorphism (Kuntner et al, 2019), coloration (Foley et al, 2020) and morphological traits (Wood et al, 2018), have allowed a better understanding of their biogeography (Xu et al, 2021), and have resulted in broad taxonomic reorganizations (Opatova et al, 2019). These studies used sequence capture techniques or transcriptomics, which are ideal for questioning deep to intermediate levels of divergence (Young & Gillung, 2020;Zhang et al, 2019), but whose utility has not been tested thoroughly in the context of recent evolution (but see Harvey et al, 2016), where most of the splits of the tree of life occur, and where more phylogenetic information is often needed, to overcome the effects of incomplete lineage sorting and horizontal gene transfer (Davidson et al, 2015;Maddison & Knowles, 2006;Rokas & Carroll, 2005).…”

Dynamic evolution of size and colour in the highly specializedZodarionant-eating spiders

“…Likewise, several animal species, including the jumping spider Habronattus ustulatus (Griswold, 1979) (Salticidae), display significant convergent evolution in colour, linked with the colonization of the gypsum dune fields of the White Sands National Park [63]. Finally, a green body colour appears to have evolved several times in tarantulas (Theraphosidae) in connection with the evolution of arboreality [64].…”