Primate tails: Ancestral state reconstruction and determinants of interspecific variation in primate tail length

Abstract

ObjectiveLiving primates vary considerably in tail length‐body size relation, ranging from tailless species to those where the tail is more than twice as long as the body. Because the general pattern and determinants of tail evolution remain incompletely known, we reconstructed evolutionary changes in relative tail length across all primates and sought to explain interspecific variation in this trait.MethodsWe combined data on tail length, head‐body length, intermembral index (IMI), habitat use, locomotion type, and range latitude for 340 species from published sources. We reconstructed the evolution of relative tail length to identify all independent cases of regime shifts on a primate phylogeny, using several methods based on Ornstein‐Uhlenbeck (OU) models. Accounting for phylogeny, we also examined the effects of habitat, locomotion type, distance from the equator and IMI on interspecific variation in tail length‐body size relation.ResultsPrimate tail length is not sexually dimorphic. A phylogenetic reconstruction allowing multiple optima explains the observed regime shifts best. During the evolutionary history of primates, relative tail length changed 50 times under an OU model. Specifically, relative tail length increased 26 and decreased 24 times. Most of these changes occurred among Old World primates. Among the variables tested here, interspecific variation in IMI and the difference between leaping and non‐leaping locomotion explained interspecific variation in relative tail length: Evolutionary decreases in relative tail length are generally associated with an increase in IMI and an absence of leaping behavior.ConclusionsRegime shifts for relative tail length in living primates occurred in concert with fundamental changes in IMI and a change from leaping to non‐leaping locomotion, or vice versa. Exceptions from this general pattern are linked to the presence of a prehensile tail or specialized foraging strategies. Thus, the primate tail appears to have evolved in functional coordination with limb proportions, presumably to assist body balance.

Substrate use drives the macroevolution of mammalian tail length diversity

“…Placed into their own evolutionary regime (as well as one additional regime that will be further discussed), this result for Primates highlights their unique evolutionary history and locomotor adaptations compared to other mammals. Tail length variation among primates was recently examined using evolutionary modelling [80]; however, this study did not examine the evolution of primate tail length within the context of all mammals and not all regime shifts identified were supported by pANCOVA. Furthermore, the authors of this study [80] employed a different procedure for obtaining a best-fit evolutionary model, which included tailless primates in their analysis and therefore violated the assumption of normally distributed data (see methods for more information).…”

“…Tail length variation among primates was recently examined using evolutionary modelling [80]; however, this study did not examine the evolution of primate tail length within the context of all mammals and not all regime shifts identified were supported by pANCOVA. Furthermore, the authors of this study [80] employed a different procedure for obtaining a best-fit evolutionary model, which included tailless primates in their analysis and therefore violated the assumption of normally distributed data (see methods for more information). These methodological differences explain why fewer evolutionary shifts in primate tail length were identified in our more comprehensive study.…”

Tails, Flails, and Sails: How Appendages Improve Terrestrial Maneuverability by Improving Stability

“…Their base of support is reduced, so smaller deflections in the position of the COM will result in toppling ( Full et al 2002 ), and their ability to compensate through interaction with the substrate is inhibited by the restricted range of available foot positions. Narrow branches are a challenging feature of arboreal environments, so surprisingly arboreality tends to drive the evolution of longer tails ( Sehner et al 2018 ; Mincer and Russo 2020 ). Of course, some of these long tails are prehensile, but there are also many examples of nonprehensile tails that assist animals with balance in a manner consistent with the other appendages discussed in this article.…”

Large Lemurs: Ecological, Demographic and Environmental Risk Factors for Weight Gain in Captivity

“…Relative tail length (13) The proportion of a species' total length (head to tail tip) that is the tail (from [41,43]). Larger values correspond to relatively longer tails: an adaptation to arboreality across primates [93][94][95]. Negative (iv) predation risk Predation score, 0-3 (13) Data on direct predation pressure are rare, but broad taxonomic descriptions of predators (e.g., "raptors") are described [41,43].…”