Temperature influences selective mortality during the early life stages of a coral reef fish.

Tauna L Rankin,Su Sponaugle,Vincent Laudet

doi:10.1371/journal.pone.0016814

Abstract

For organisms with complex life cycles, processes occurring at the interface between life stages can disproportionately impact survival and population dynamics. Temperature is an important factor influencing growth in poikilotherms, and growth-related processes are frequently correlated with survival. We examined the influence of water temperature on growth-related early life history traits (ELHTs) and differential mortality during the transition from larval to early juvenile stage in sixteen monthly cohorts of bicolor damselfish Stegastes partitus, sampled on reefs of the upper Florida Keys, USA over 6 years. Otolith analysis of settlers and juveniles coupled with environmental data revealed that mean near-reef water temperature explained a significant proportion of variation in pelagic larval duration (PLD), early larval growth, size-at-settlement, and growth during early juvenile life. Among all cohorts, surviving juveniles were consistently larger at settlement, but grew more slowly during the first 6 d post-settlement. For the other ELHTs, selective mortality varied seasonally: during winter and spring months, survivors exhibited faster larval growth and shorter PLDs, whereas during warmer summer months, selection on PLD reversed and selection on larval growth became non-linear. Our results demonstrate that temperature not only shapes growth-related traits, but can also influence the direction and intensity of selective mortality.

Highlights

Most animals have complex life cycles with multiple ontogenetic shifts, characterized by changes in morphology, physiology, behavior, and/or habitat [1]
When tested using forward selection and 1000 Monte Carlo permutations, near-reef water temperature averaged over the larval period was the only
Our results demonstrate that does temperature influence the Early life history traits (ELHTs) that are important to survival during the critical periods of larval and early juvenile life, but temperature can affect how selective mortality processes act on those traits

Summary

Introduction

Most animals have complex life cycles with multiple ontogenetic shifts, characterized by changes in morphology, physiology, behavior, and/or habitat [1] This life history confounds our understanding of the processes affecting population dynamics, because pivotal events may occur during any stage or cumulatively across stages [1]. Life history traits (ELHTs), such as larval growth rate or stage duration, often vary among individuals due to differences in genetic makeup, maternal contributions, and/or environmental influences. This trait variation coupled with high mortality rates create conditions for selective processes to occur [3]. Such ‘‘trait-mediated effects’’ can impact population dynamics and cascade through the trophic levels [4]

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Results

Conclusion