Evolutionary allometry and ecological correlates of fang length evolution in vipers

Abstract

Traits for prey acquisition form the phenotypic interface of predator–prey interactions. In venomous predators, morphological variation in venom delivery apparatus like fangs and stingers may be optimized for dispatching prey. Here, we determine how a single dimension of venom injection systems evolves in response to variation in the size, climatic conditions and dietary ecology of viperid snakes. We measured fang length in more than 1900 museum specimens representing 199 viper species (55% of recognized species). We find both phylogenetic signal and within-clade variation in relative fang length across vipers suggesting both general taxonomic trends and potential adaptive divergence in fang length. We recover positive evolutionary allometry and little static allometry in fang length. Proportionally longer fangs have evolved in larger species, which may facilitate venom injection in more voluminous prey. Finally, we leverage climatic and diet data to assess the global correlates of fang length. We find that models of fang length evolution are improved through the inclusion of both temperature and diet, particularly the extent to which diets are mammal-heavy diets. These findings demonstrate how adaptive variation can emerge among components of complex prey capture systems.

Patterns of morphological variation and ecological correlates in the skull of vipers (Serpentes: Viperidae)

“…The reduction in the number of mandibular and palatopterygoid teeth, as in the species of Bothrops and Crotalus mentioned before, could then be a response to those selection pressures. Holding et al (2022) demonstrated that fang length in vipers is positively correlated with stoutness. The authors found that proportionally longer fangs have evolved in larger species, making it easier to inject venom into more voluminous prey.…”

“…Holding et al (2022) demonstrated that fang length in vipers is positively correlated with stoutness. The authors found that proportionally longer fangs have evolved in larger species, making it easier to inject venom into more voluminous prey.…”

“…Nevertheless, holding the prey after the strike faces the arboreal snake with the risk of damage caused by a struggling animal. In this regard, some authors (Holding et al, 2022; Wüster et al, 2005) suggested that shorter fangs in vipers that retain the prey after the strike could reduce the risk of fang breakage.…”

“…Most species are generalist feeders (feeding on amphibians, reptiles, birds, and/or mammals), but few have specialized diets (feeding only or mostly on mammals, birds, ectotherms, or arthropods; Greene, 1992, 1997; Marques et al, 2012; Martins et al, 2002). Several studies reported different feeding strategies in vipers related to different habitats and preys (Cundall, 1983, 2002, 2009; Cundall & Greene, 2000; Deufel & Cundall, 2006; Glaudas et al, 2017; Wüster et al, 2005) and it has been found that type of prey influences fang length (Holding et al, 2022). These studies suggest that different selective pressures of the environment could have influenced the overall morphology of the skull of vipers, as demonstrated for other groups of snakes (Klaczko et al, 2016).…”

“…Most species are generalist feeders (feeding on amphibians, reptiles, birds, and/ or mammals), but few have specialized diets (feeding only or mostly on mammals, birds, ectotherms, or arthropods; Greene, 1992Greene, , 1997Marques et al, 2012;Martins et al, 2002). Several studies reported different feeding strategies in vipers related to different habitats and preys (Cundall, 1983(Cundall, , 2002(Cundall, , 2009Cundall & Greene, 2000;Glaudas et al, 2017;Wüster et al, 2005) and it has been found that type of prey influences fang length (Holding et al, 2022).…”