Climate influences fledgling sex ratio and sex-specific dispersal in a seabird.

Alvaro Barros,Alberto Velando,David Alvarez,Samuli Helle

doi:10.1371/journal.pone.0071358

Abstract

Climate influences the dynamics of natural populations by direct effects over habitat quality but also modulating the phenotypic responses of organisms’ life-history traits. These responses may be different in males and females, particularly in dimorphic species, due to sex-specific requirements or constraints. Here, in a coastal seabird, the European shag (Phalacrocorax aristotelis), we studied the influence of climate (North Atlantic Oscillation, NAO; Sea Surface Temperature, SST) on two sex-related population parameters: fledgling sex ratio and sex-specific dispersal. We found that fledgling sex ratio was female skewed in NAO-positive years and male skewed in NAO-negative years. Accordingly, females dispersed a longer distance in NAO-positive years when females were overproduced, and on the contrary, males dispersed more in NAO-negative years. Overall, our findings provide rare evidence on vertebrates with genetic sex determination that climate conditions may govern population dynamics by affecting sex-specific density and dispersal.

Highlights

Climate fluctuations strongly influence the dynamics of natural populations, as revealed by long-term studies [1,2,3]
We showed that fledgling sex ratio was related to NAO in a breeding colony of European shag
NAO was related to natal dispersal, but interestingly this relationship was sex-specific

Summary

Introduction

Climate fluctuations strongly influence the dynamics of natural populations, as revealed by long-term studies [1,2,3]. Climate directly affects food and habitat availability, which in turn influence key demographic parameters such as reproductive success [4], [5], survival [6,7,8,9] and recruitment [10], [11]. Climatic oscillations may exert complex delayed effects because organisms program phenotypic responses to environmental cues, in many cases, to prepare for the environmental conditions that will encounter during their life [12]. In red deer (Cervus elaphus) offspring weigth, a key population parameter, is affected by parental weigth at birth, which in turn is governed by climate [16], [17]. Different responses by males and females to climatic oscillations may produce indirect effects on key demographic parameters involved in population dynamics [18]. In dimorphic species, sex ratio alterations may be produced by sex-specific mortality of the more demanding sex (i.e. the larger sex, which needs more parental supply to be successfully reared) [22] or by maternal production of the more demanding sex when resources are plentiful [25]

Methods

Results

Conclusion