Species comparison of among- and within-individual variation and correlations

Abstract

Individuals frequently differ consistently from one another in their average behaviors (i.e. “animal personality”) and in correlated suites of consistent behavioral responses (i.e. “behavioral syndromes”). However, understanding the evolutionary basis of this (co)variation has lagged behind demonstrations of its presence. This lag partially stems from comparative methods rarely being used in the field. Consequently, much of the research on animal personality has relied on “adaptive stories” focused on single species and populations. Here we used a comparative approach to examine the role of phylogeny in shaping patterns of average behaviors, behavioral variation, and behavioral correlations. In comparing the behaviors and behavioral variation for five species of Gryllid crickets we found that phylogeny shaped average behaviors and behavioral (co)variation. Variation in average exploratory behavior and response to cues of predator presence attributable to phylogeny was greater or comparable to the magnitude of “personality variation”. Likewise, magnitudes of variation were concordant with evolutionary relationships and behavioral correlations were consistent across species. These results suggest that phylogenetic constraints play an important role in the expression of animal personalities and behavioral syndromes and emphasize the importance of examining evolutionary explanations within a comparative framework.

The persistence and evolutionary consequences of vestigial behaviours

“…derived and ancestral population designations should be confirmed). Phylogenetic analysis may also provide a useful framework to identify potentially vestigial forms of behaviour, as well as identifying behavioural variation associated with phylogenetic signal more generally, which recent research has indicated might account for a substantial proportion of observed variation (Dalos et al ., 2021; but see White, Pascall & Wilson, 2020). Selection pressures at the relevant time points should also where possible be corroborated – for example by historical record, metagenomics or geological/fossil records (Cousyn et al ., 2001) – rather than by assuming that contemporary differences in selection regime are representative of long‐term trends.…”

“…They also warrant consideration in behavioural research. Vestigial behaviours might re‐emerge under artificial experimental conditions, and may be prone to misinterpretation by researchers seeking to understand behavioural variation within an adaptive context (Gould & Lewontin, 1979; Dalos et al ., 2021). For example, Byers (1997) controversially argued that many behavioural and morphological adaptations of American pronghorn ( Antilocapra americana ) populations are in fact adaptations to so‐called ‘ghosts of predators past’, that is, predators that have been long extinct (see also Peckarsky & Penton, 1988).…”