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

• Published in: The Journal of animal ecology Vol. 81; no. 4; pp. 806 - 817
• Main Authors: Morrongiello, John R., Bond, Nicholas R., Crook, David A., Wong, Bob B. M.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing 01.07.2012; Blackwell Publishing Ltd; Blackwell
• Subjects: adaptive phenotypic plasticity; Agnatha. Pisces; Animal and plant ecology; Animal ecology; Animal populations; Animal reproduction; Animal, plant and microbial ecology; Animals; Biological and medical sciences; Ecological competition; Eggs; Environment; Environmental quality; Fecundity; Female; Female animals; Fertility; Fish; Freshwater; Freshwater ecology; freshwater fish; Freshwater fishes; Fundamental and applied biological sciences. Psychology; General aspects; Genetic Fitness; Habitats; Life histories; maternal effect; Models, Biological; Nannoperca australis; optimal offspring size; Ovum - physiology; Perciformes - genetics; Perciformes - physiology; Reproduction; reproductive life history; spatial bet‐hedging; Streams; unpredictable environment; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; Victoria; Wetland ecology; Victoria; Bet hedging strategy; Life history; Egg; Fresh water; Phenotypic plasticity; Spatial variation; spatial bet-hedging; freshwater fish; Progeny; optimal offspring size; Vertebrata; Reproduction; Environmental quality; Pisces; adaptive phenotypic plasticity; Environment; Maternal effect; unpredictable environment; Adaptation; Environment quality; reproductive life history
• ISSN: 0021-8790; 1365-2656
• DOI: 10.1111/j.1365-2656.2012.01961.x

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.