Do animal personalities promote species coexistence?Atest with sympatric boreal rodents

Abstract

The coexistence of competing species requires density feedbacks that have a larger effect on their own species' population growth than they do on others in the assembly. The feedbacks are often associated with behavioral tradeoffs that enable species to differentially exploit underlying axes of heterogeneity.Conjoining theories of species coexistence with foraging behavior and density-dependent habitat selection reveals that such tradeoffs impinge on invasion probabilities and equilibrium dynamics emerging from species' differences in habitat use. The resulting habitat separation promotes coexistence by reducing the overall interaction among species. Differential habitat selection depends on the behavioral abilities of organisms to identify and exploit the most profitable habitats and resource patches. One might thus expect that each species will evolve behavioral types distinct from those of other potential competitors. Accordingly, we exposed four coexisting species in four genera of boreal rodents to open-field tests. We used principal components (PC) to summarize their behaviors along three independent axes corresponding with clines of exploratory, vigilant, and apprehensive personalities. We confirmed that the axes represented repeatable behaviors (personalities) and assessed differences among species with a general linear model (GLM). The GLM revealed highly distinct differences among species, and between pairs of species, on each PC. Even so, it is difficult to infer the adaptive advantages of personality to the habitat segregation that reduces otherwise high interactions among species. Rather, personalities are best interpreted as co-adaptive behaviors reflecting the complex of morphological, physiological and behavioral attributes that dictate tradeoffs and enable coexistence.

Exploratory and risk-taking behaviours in coexisting rodents

“…Competition among coexisting species may illicit variation in reproductive strategy and ultimately personality phenotypes. Despite apparent competition, there are few studies that aim to model personality in coexisting species (Wauters et al, 2019; Morris and Palmer, 2023).…”

“…While we did not show evidence to support the POLS hypothesis between individuals of the same species, we show significant differences in behavioural phenotypes among coexisting species. Because species inhabiting the same ecological niche must engage in increased competition for resources, we further postulate that competition can regulate the expression of alternative behavioural phenotypes (Morris and Palmer, 2023; Sobral et al, 2023). Because personality may be a driving mechanism for environmental processes such as the distribution of seeds through fecal droppings (Réale et al, 2010; Morris and Palmer, 2023; Boone et al, 2022; Brehm and Mortelliti, 2022), we suggest that further evaluation into trade-offs in personality, population dynamics and changes in environmental structure will be valuable future research.…”

“…An extensive body of literature on the personality of various rodent species shows plastic changes in traits associated with the POLS between individuals and variation among species (Dingemanse et al, 2010; Brehm et al, 2020). Within an ecosystem, trade-offs in exploration and risk avoidance have been shown to promote species coexistence (Morris and Palmer, 2023; Milles et al, 2020). Such intraspecific differences in personality, specifically traits related to movement, have been shown to regulate community dynamics (Milles et al, 2020).…”

“…We hypothesized that if coexistence promotes alternative behavioural strategies to accommodate intra- and interspecific competition, then there should be measurable differences in personality among species along the proposed “fast” to “slow” continuum. Indeed, Distinct differences in personality have been shown to arise as a co-adaptive set of behaviours among species, potentially enabling coexistence (Morris and Palmer, 2023). We further predicted that there should be measurable variation in behaviours relating to movement patterns among species.…”