Relative contributions of fixed and dynamic heterogeneity to variation in lifetime reproductive success in kestrels (Falco tinnunculus)

Maarten J E Broekman,Shripad Tuljapurkar,Eelke Jongejans

doi:10.1002/1438-390x.12063

Maarten J E Broekman, Shripad Tuljapurkar + Show 1 more

Open Access

https://doi.org/10.1002/1438-390x.12063

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Abstract

AbstractMany species show large variation in lifetime reproductive success (LRS), with a few individuals producing the majority of offspring. This variation can be explained by factors related to individuals (fixed heterogeneity) and stochastic differences in survival and reproduction (dynamic heterogeneity). In this study, we study the relative effects of these processes on the LRS of a Dutch Kestrel population, using three different methods. First, we extended neutral simulations by simulating LRS distributions of populations consisting of groups with increasingly different population parameters. Decomposition of total LRS variance into contributions from fixed and dynamic heterogeneity revealed that the proportion of fixed heterogeneity is probably lower than 10% of the total variance. Secondly, we used sensitivities of the mean and variance in LRS to each parameter to analytically show that it is impossible to get equal contributions of fixed and dynamic heterogeneity when only one parameter differs between groups. Finally, we computed the LRS probability distribution to show that even when all individuals have identical survival and reproduction rates, the variance in LRS is large (females: 27.52, males: 12.99). Although each method has its limitations, they all lead to the conclusion that the majority of the variation in kestrel LRS is caused by dynamic heterogeneity. This large effect of dynamic heterogeneity on LRS is similar to results for other species and contributes to the evidence that in most species the majority of individual variation in LRS is due to dynamic heterogeneity.

Highlights

In most species there is large variation in the total number of offspring produced by an individual during its life: the lifetime reproductive success (LRS)
The absence of a significant effect for most factors might be attributed to a large effect of dynamic heterogeneity, which can obscure relations with LRS
Because of this result and the finding in many other studies that dynamic heterogeneity plays a large role in determining LRS variation, we hypothesize that for our kestrel population the majority of LRS variation can be attributed to dynamic heterogeneity

Summary

| INTRODUCTION

The total variation in LRS is caused by this dynamic and fixed heterogeneity (note that some studies call these patterns individual stochasticity and heterogeneity, respectively, for example, Caswell, 2009, 2011; van Daalen & Caswell, 2017). The absence of a significant effect for most factors might be attributed to a large effect of dynamic heterogeneity, which can obscure relations with LRS Because of this result and the finding in many other studies that dynamic heterogeneity plays a large role in determining LRS variation, we hypothesize that for our kestrel population the majority of LRS variation can be attributed to dynamic heterogeneity. We calculate the sensitivities of producing a certain LRS to the population parameters These methods were performed separately for females and males and for both sexes all methods agree that most of the variation in LRS can be attributed to dynamic heterogeneity, confirming our hypothesis

| METHODS

| RESULTS

Findings

| DISCUSSION