The relative contribution of individual quality and changing climate as drivers of lifetime reproductive success in a short-lived avian species

Lisha L Berzins,Robert G Clark,Christy A Morrissey,Russell D Dawson

doi:10.1038/s41598-020-75557-w

Abstract

Animal populations are influenced strongly by fluctuations in weather conditions, but long-term fitness costs are rarely explored, especially in short-lived avian species. We evaluated the relative contributions of individual characteristics and environmental conditions to lifetime reproductive success (LRS) of female tree swallows (Tachycineta bicolor) from two populations breeding in contrasting environments and geographies, Saskatchewan and British Columbia, Canada. Female swallows achieved higher LRS by breeding early in the season and producing more fledglings. Other measures of female quality had virtually no influence on LRS. Genetic factors did not predict LRS, as there was no correlation between life-history components for sister pairs nor between mothers and their daughters. Instead, climate variability—indexed by spring pond density (i.e., abundance of wetland basins holding water) during years when females bred—had strong positive effects on female LRS in more arid Saskatchewan but only weak positive effects of moisture conditions were detected in wetter British Columbia. Overall, several life history trait correlates of LRS were similar between populations, but local environmental factors experienced by individuals while breeding produced large differences in LRS. Consequently, variable and extreme environmental conditions associated with changing climate are predicted to influence individual fitness of distinct populations within a species’ range.

Highlights

Animal populations are influenced strongly by fluctuations in weather conditions, but long-term fitness costs are rarely explored, especially in short-lived avian species
Fluctuations in weather conditions play a major role in dynamics of animal populations by affecting survival and reproduction[1], and these effects may be pronounced in years with extreme weather e vents[2]
One approach to evaluating how weather variability and climate extremes influence avian fitness is to determine their individual and combined effects on the total numbers of offspring produced by individuals over their lifetime that contribute to future generations, i.e., lifetime reproductive success (LRS)[9,10]

Summary

Introduction

Animal populations are influenced strongly by fluctuations in weather conditions, but long-term fitness costs are rarely explored, especially in short-lived avian species. We evaluated the relative contributions of individual characteristics and environmental conditions to lifetime reproductive success (LRS) of female tree swallows (Tachycineta bicolor) from two populations breeding in contrasting environments and geographies, Saskatchewan and British Columbia, Canada. Several life history trait correlates of LRS were similar between populations, but local environmental factors experienced by individuals while breeding produced large differences in LRS. Variable and extreme environmental conditions associated with changing climate are predicted to influence individual fitness of distinct populations within a species’ range. One approach to evaluating how weather variability and climate extremes influence avian fitness is to determine their individual and combined effects on the total numbers of offspring produced by individuals over their lifetime that contribute to future generations, i.e., lifetime reproductive success (LRS)[9,10]. Measurements of LRS, at least in avian studies, commonly assume that the “number of fledglings” (survive to fledging age) is a reliable approximation of fitness instead of more accurately determining the “number of recruits” (survive to breeding age), which may obscure the interpretation of LRS d rivers[16,20]

Methods

Results

Conclusion