Reproductive skews of territorial species in heterogeneous landscapes

Abstract

The socio-spatial organization of populations of territorial species refers to the way distance, variation in social status and variation in resource availability interact to shape the way territory-bounded individuals are distributed. I investigated the resulting reproductive skew, i.e. the emergence of a few high performers amidst a majority of mediocre performers, using lifetime reproductive success data from 46 species living in contrasting landscape configurations. I applied three skew statistics that captured different aspects of the individual heterogeneity: the skewness, the Gini coefficient of inequalities and Hill's index of heavy-tailed distribution. I also used a simplistic theoretical model, in which only immediate neighbors interacted. In the comparative analysis, the distribution of lifetime reproductive success was more skewed but also more egalitarian in homogeneous than heterogeneous landscapes, after controlling for the allometric effect of the body mass. The simulations indicated that a possible explanatory mechanism for the change in egalitarian properties is that some individuals hide behind their neighbors in the socio-spatial organization. They therefore secure a better territory than if the distribution was despotic. The ideal despotic model without spatial restriction on interactions could not explain the correlations. This work emphasizes that the shape of the distribution of fitness components conveys information besides the mean and the variance, and the potential for nontrivial effects to emerge from simple movement heuristics.

To prosper, live long: understanding the sources of reproductive skew and extreme reproductive success in structured populations

“…1 Some researchers have looked for variation in strategy or quality that allows the most successful individuals to dominate reproduction (e.g. Annett and Pierotti (1999); Péron (2023)); however, our past work suggests that exceptional success may be mostly random, resulting from some combination of rapid early growth or maturation, a favorable environment at the right time, unusually large clutch sizes, and a long life (Snyder and Ellner, 2018, 2022; Snyder et al, 2021). Even then, we can ask exactly how an individual needs to be lucky to end up far out on the reproductive tail, since not all of these forms of luck may be equally important for having exceptional LRO.…”