Selection on offspring size among environments: the roles of environmental quality and variability

Monro, K, Sinclair-Taylor, T and Marshall, DJ (2010) Selection on offspring size among environments: the roles of environmental quality and variability. Functional Ecology, 24 3: 676-684. doi:10.1111/j.1365-2435.2009.01665.x

Author Monro, K
Sinclair-Taylor, T
Marshall, DJ
Title Selection on offspring size among environments: the roles of environmental quality and variability
Journal name Functional Ecology   Check publisher's open access policy
ISSN 0269-8463
Publication date 2010-06-01
Year available 2009
Sub-type Article (original research)
DOI 10.1111/j.1365-2435.2009.01665.x
Volume 24
Issue 3
Start page 676
End page 684
Total pages 9
Editor Charles W Fox
Place of publication U K
Publisher Wiley-Blackwell Publishing Ltd
Language eng
Subject C1
970106 Expanding Knowledge in the Biological Sciences
060411 Population, Ecological and Evolutionary Genetics
Abstract 1. How mothers balance the trade-off between offspring size and number to maximize maternal fitness has long been of interest to ecologists seeking to understand the evolution of offspring size. Predictions of the optimal offspring size depend fundamentally on the relationship between offspring size and offspring performance, which may in turn vary with environmental conditions. 2. Selection for larger offspring is expected to intensify as environmental quality deteriorates. Models also predict that variable selection on offspring size may favour the evolution of larger offspring than those favoured when selection is constant, or of strategies of variable offspring provisioning (e.g. bet-hedging, plasticity). To date, there is mixed empirical support for the first expectation and few tests of the second. Given, however, that offspring size effects are often estimated under controlled laboratory conditions that presumably downplay their strength and variability, we may not yet understand how selection shapes offspring size in nature. 3. We examined several relationships between offspring size and performance in controlled (laboratory) and natural (field) environments over time for a colonial marine invertebrate, Bugula neritina, and assessed the variability of these relationships by doing so for replicate cohorts. We further developed a simple optimality model to examine whether predictions of the optimal offspring size were similar (or similarly variable) across environments. 4. We found that selection on offspring size varied substantially among laboratory and field environments, and among cohorts in the latter. In the laboratory, our model consistently predicted that mothers should maximize their fecundity by producing the smallest possible offspring. In the field, however, the predicted optimal offspring size varied from the smallest possible size to the largest possible size for different cohorts. 5. Our study suggests that laboratory estimates of offspring size effects, though often necessary, may not always reflect the direction or variability of selection on offspring size under natural conditions. The optimal offspring size for mothers in nature may be an ever-shifting target that shapes provisioning strategies such as bet-hedging or plasticity in offspring size.
Keyword Egg size
Maternal effects
Q-Index Code C1
Q-Index Status Confirmed Code

Document type: Journal Article
Sub-type: Article (original research)
Collections: 2010 Higher Education Research Data Collection
School of Biological Sciences Publications
Ecology Centre Publications
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Citation counts: TR Web of Science Citation Count  Cited 11 times in Thomson Reuters Web of Science Article | Citations
Scopus Citation Count Cited 11 times in Scopus Article | Citations
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Created: Sun, 25 Apr 2010, 10:04:19 EST