Spatial variation in egg size and egg number reflects trade-offs and bet-hedging in a freshwater fish

John Morrongiello, Nick Bond, David Crook, Bob Wong

Research output: Contribution to journalArticle

47 Citations (Scopus)

Abstract

1.Maternal reproductive investment is thought to reflect a trade-off between offspring size and fecundity, and models generally predict that mothers inhabiting adverse environments will produce fewer, larger offspring. More recently, the importance of environmental unpredictability in influencing maternal investment has been considered, with some models predicting that mothers should adopt a diversified bet-hedging strategy whilst others a conservative bet-hedging strategy. 2.We explore spatial egg size and fecundity patterns in the freshwater fish southern pygmy perch (Nannoperca australis) that inhabits a diversity of streams along gradients of environmental quality, variability and predictability. 3.Contrary to some predictions, N. australis populations inhabiting increasingly harsh streams produced more numerous and smaller eggs. Furthermore, within-female egg size variability increased as environments became more unpredictable. 4.We argue that in harsh environments or those prone to physical disturbance, sources of mortality are size independent with offspring size having only a minor influence on offspring fitness. Instead, maternal fitness is maximized by producing many small eggs, increasing the likelihood that some offspring will disperse to permanent water. We also provide empirical support for diversified bet-hedging as an adaptive strategy when future environmental quality is uncertain and suggest egg size may be a more appropriate fitness measure in stable environments characterized by size-dependent fitness. These results likely reflect spatial patterns of adaptive plasticity and bet-hedging in response to both predictable and unpredictable environmental variance and highlight the importance of considering both trait averages and variance. 5.Reproductive life-history traits can vary predictably along environmental gradients. Human activity, such as the hydrological modification of natural flow regimes, alters the form and magnitude of these gradients, and this can have both ecological and evolutionary implications for biota adapted to now non-existent natural environmental heterogeneity. © 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society.
Original languageEnglish
Pages (from-to)806-817
Number of pages12
JournalJournal of Animal Ecology
Volume81
Issue number4
DOIs
Publication statusPublished - 2012
Externally publishedYes

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fish roe
bet-hedging
egg size
freshwater fish
spatial variation
fitness
egg
fish
environmental quality
fecundity
physical disturbance
environmental gradient
life history trait
animal ecology
trade-off
plasticity
biota
perch
human activity
mortality

Cite this

Morrongiello, John ; Bond, Nick ; Crook, David ; Wong, Bob. / Spatial variation in egg size and egg number reflects trade-offs and bet-hedging in a freshwater fish. In: Journal of Animal Ecology. 2012 ; Vol. 81, No. 4. pp. 806-817.
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Spatial variation in egg size and egg number reflects trade-offs and bet-hedging in a freshwater fish. / Morrongiello, John; Bond, Nick; Crook, David; Wong, Bob.

In: Journal of Animal Ecology, Vol. 81, No. 4, 2012, p. 806-817.

Research output: Contribution to journalArticle

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AB - 1.Maternal reproductive investment is thought to reflect a trade-off between offspring size and fecundity, and models generally predict that mothers inhabiting adverse environments will produce fewer, larger offspring. More recently, the importance of environmental unpredictability in influencing maternal investment has been considered, with some models predicting that mothers should adopt a diversified bet-hedging strategy whilst others a conservative bet-hedging strategy. 2.We explore spatial egg size and fecundity patterns in the freshwater fish southern pygmy perch (Nannoperca australis) that inhabits a diversity of streams along gradients of environmental quality, variability and predictability. 3.Contrary to some predictions, N. australis populations inhabiting increasingly harsh streams produced more numerous and smaller eggs. Furthermore, within-female egg size variability increased as environments became more unpredictable. 4.We argue that in harsh environments or those prone to physical disturbance, sources of mortality are size independent with offspring size having only a minor influence on offspring fitness. Instead, maternal fitness is maximized by producing many small eggs, increasing the likelihood that some offspring will disperse to permanent water. We also provide empirical support for diversified bet-hedging as an adaptive strategy when future environmental quality is uncertain and suggest egg size may be a more appropriate fitness measure in stable environments characterized by size-dependent fitness. These results likely reflect spatial patterns of adaptive plasticity and bet-hedging in response to both predictable and unpredictable environmental variance and highlight the importance of considering both trait averages and variance. 5.Reproductive life-history traits can vary predictably along environmental gradients. Human activity, such as the hydrological modification of natural flow regimes, alters the form and magnitude of these gradients, and this can have both ecological and evolutionary implications for biota adapted to now non-existent natural environmental heterogeneity. © 2012 The Authors. Journal of Animal Ecology © 2012 British Ecological Society.

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