Why does offspring size affect performance? Integrating metabolic scaling with life-history theory

Pettersen, Amanda K.; White, Craig R.; Marshall, Dustin J.

doi:10.1098/rspb.2015.1946

Cited by 48 publications

(77 citation statements)

References 66 publications

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“…Bugula neritina Linnaeus, 1758, is a bryozoan common to sessile marine communities worldwide and is used extensively as a model for studies on life‐history strategies (Wendt ; Allen & Marshall ; Pettersen et al . ; Cameron et al . ).…”

Section: Methodsmentioning

confidence: 99%

Should mothers provision their offspring equally? A manipulative field test

2017

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Within-brood variation in offspring size is universal, but its causes are unclear. Theoretical explanations for within-brood variation commonly invoke bet-hedging, although alternatives consider the role of sibling competition. Despite abundant theory, empirical manipulations of within-brood variation in offspring size are rare. Using a field experiment, we investigate the consequences of unequal maternal provisioning for both maternal and offspring fitness in a marine invertebrate. We create experimental broods of siblings with identical mean, but different variance, in offspring size, and different sibling densities. Overall, more-variable broods had higher mean performance than less-variable broods, suggesting benefits of unequal provisioning that arise independently of bet-hedging. Complementarity effects drove these benefits, apparently because offspring-size variation promotes resource partitioning. We suggest that when siblings compete for the same resources, and offspring size affects niche usage, the production of more-variable broods can provide greater fitness returns given the same maternal investment; a process unanticipated by the current theory.

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Section: Methodsmentioning

confidence: 99%

Should mothers provision their offspring equally? A manipulative field test

2017

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“…Once embryogenesis is complete, the developed non-feeding larvae are released into the plankton where they are competent to settle almost immediately, yet remain dependent on maternally derived energy reserves from release as larvae through post-settlement until the end of metamorphosis. This 'dependent phase' (sensu [23]) lasts approximately 2 days before the development of the first zooid with feeding structure (lophophore) is complete, and offspring feed for themselves.…”

Section: Materials and Methods (A) Study Species Site And Larval Massmentioning

confidence: 99%

“…The released larvae were then immediately photographed on a glass slide using a Moticam 5 digital camera (Motic, Hong Kong, China) mounted on a dissecting microscope as per standard techniques developed previously [24]. Measurements of larval body area and length of the ciliated groove were estimated to the nearest micrometres using IMAGEJ software (v. 1.47) and larvae mass estimates based on calculations obtained in a previous study [23]. Once photographed, larvae were then pipetted in a drop of seawater directly onto roughened acetate sheets to induce settlement.…”

Section: Materials and Methods (A) Study Species Site And Larval Massmentioning

confidence: 99%

Metabolic rate covaries with fitness and the pace of the life history in the field

Pettersen¹,

White²,

Marshall³

2016

Proc. R. Soc. B.

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Metabolic rate reflects the 'pace of life' in every organism. Metabolic rate is related to an organism's capacity for essential maintenance, growth and reproduction-all of which interact to affect fitness. Although thousands of measurements of metabolic rate have been made, the microevolutionary forces that shape metabolic rate remain poorly resolved. The relationship between metabolic rate and components of fitness are often inconsistent, possibly because these fitness components incompletely map to actual fitness and often negatively covary with each other. Here we measure metabolic rate across ontogeny and monitor its effects on actual fitness (lifetime reproductive output) for a marine bryozoan in the field. We also measure key components of fitness throughout the entire life history including growth rate, longevity and age at the onset of reproduction. We found that correlational selection favours individuals with higher metabolic rates in one stage and lower metabolic rates in the other-individuals with similar metabolic rates in each developmental stage displayed the lowest fitness. Furthermore, individuals with the lowest metabolic rates lived for longer and reproduced more, but they also grew more slowly and took longer to reproduce initially. That metabolic rate is related to the pace of the life history in nature has long been suggested by macroevolutionary patterns but this study reveals the microevolutionary processes that probably generated these patterns.

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“…Burgess et al () found that when the dispersal period of a bryozoan with a similar life history, Bugula neritina , is extended, there is selection for larger offspring size. Burgess's findings have intuitive appeal for three reasons: dispersal is costly for nonfeeding offspring (Strathmann , Bennett and Marshall ), larger offspring are released with more energy, and larger offspring use proportionally less energy during dispersal than smaller offspring (Pettersen et al ). These three criteria also apply to our study species, Watersipora , but we found the reverse pattern to Burgess: colonies that were larger as offspring perform initially worse when they experience an extended dispersal period.…”

Section: Discussionmentioning

confidence: 99%

Dispersal duration mediates selection on offspring size

Svanfeldt

Monro

Marshall

2016

Oikos

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Offspring size varies at all levels of organisation, among species, mothers and clutches. This variation is thought to be the result of a tradeoff between offspring quality and quantity, where larger offspring perform better but are more costly to produce. Local environmental conditions alter the benefits of increased offspring size and thereby mediate selection on this trait. For sessile organisms, dispersal is a crucial part of the offspring phase, and in animals, bigger offspring tend to better endure longer dispersal distances than smaller offspring because they have more energy. Theory predicts that increasing distances between suitable habitats strengthens selection for larger offspring. We manipulated the dispersal duration of offspring of different sizes in the bryozoan Watersipora subtorquata and then examined the relationship between offspring size and post‐metamorphic performance in the field. We found that selection on offspring size is altered by larval experience. Larger offspring had higher post‐settlement performance if the larval period was short but, contrary to current theory, performed worse when the larval period was extended. The reversal of the relationship between offspring size and performance by extending the larval phase in Watersipora may be due to the way in which offspring size affects growth in this species. Regardless of the mechanism, it appears that experiences in one life‐history stage alter selection on offspring size in another stage, even when they occupy identical habitats as adults.

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Why does offspring size affect performance? Integrating metabolic scaling with life-history theory

Cited by 48 publications

References 66 publications

Should mothers provision their offspring equally? A manipulative field test

Should mothers provision their offspring equally? A manipulative field test

Metabolic rate covaries with fitness and the pace of the life history in the field

Dispersal duration mediates selection on offspring size

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