Tag Archives: egg size

Published paper: Interspecific competition alters non-linear selection on offspring size in the field

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Authors: Dustin J Marshall and Keyne Monro

Published in: Evolution, volume 67, issue 2 (February 2013) doi: 10.1111/j.1558-5646.2012.01749.x

Abstract

Offspring size is one of the most important life-history traits with consequences for both the ecology and evolution of most organisms. Surprisingly, formal estimates of selection on offspring size are rare, and the degree to which selection (particularly nonlinear selection) varies among environments remains poorly explored.

We estimate linear and nonlinear selection on offspring size, module size, and senescence rate for a sessile marine invertebrate in the field under three different intensities of interspecific competition. The intensity of competition strongly modified the strength and form of selection acting on offspring size.

We found evidence for differences in nonlinear selection across the three environments.

Our results suggest that the fitness returns of a given offspring size depend simultaneously on their environmental context, and on the context of other offspring traits. Offspring size effects can be more pervasive with regards to their influence on the fitness returns of other traits than previously recognized, and we suggest that the evolution of offspring size cannot be understood in isolation from other traits.

Overall, variability in the form and strength of selection on offspring size in nature may reduce the efficacy of selection on offspring size and maintain variation in this trait.

Full paper

Marshall DJ, Monro K (2013) Interspecific competition alters nonlinear selection on offspring size in the field. Evolution, 67-2: 328–337 PDFPDF 291 KB doi: 10.1111/j.1558-5646.2012.01749.x

Published paper: The biogeography of marine invertebrate life histories

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Authors: Dustin J Marshall, Patrick J Krug, Elena K Kupriyanova, Maria Byrne and Richard B Emlet

Published in: Annual Review of Ecology, Evolution and Systematics, volume 43, pp. 97–114, doi: 10.1146/annurev-ecolsys-102710-145004

Abstract

Biologists have long sought to identify and explain patterns in the diverse array of marine life histories. The most famous speculation about such patterns is Gunnar Thorson’s suggestion that species producing planktonic larvae are rarer at higher latitudes (Thorson’s rule). Although some elements of Thorson’s rule have proven incorrect, other elements remain untested.

With a wealth of new life-history data, statistical approaches, and remote-sensing technology, new insights into marine reproduction can be generated.

We gathered life-history data for more than 1,000 marine invertebrates and examined patterns in the prevalence of different life histories. Systematic patterns in marine life histories exist at a range of scales, some of which support Thorson, whereas others suggest previously unrecognized relationships between the marine environment and the life histories of marine invertebrates.

Overall, marine life histories covary strongly with temperature and local ocean productivity, and different regions should be managed accordingly.

Full paper

Marshall DJ, Krug PJ, Kupriyanova EK, Byrne M, Emlet RB (2012) The biogeography of marine invertebrate life-histories. Annual Review of Ecology, Evolution and Systematics, 43: 97–114 External linke-print doi: 10.1146/annurev-ecolsys-102710-145004

Published paper: Initial offspring size mediates trade-off between fecundity and longevity in the field

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Authors: Halil Kesselring, Rebecca Wheatley and Dustin J Marshall

Published in: Marine Ecology Progress Series, volume 465, doi: 10.3354/meps09865

Abstract

An understanding of the effects of intraspecific variation in offspring size is important from both an ecological and an evolutionary perspective.

While the relationship between off- spring size and overall offspring performance is key, most studies are restricted to examination of the effects of offspring size on early life-history stages only, and too few have examined the effects of offspring size throughout the life history.

Here, we examine the effects of offspring size on post- metamorphic survival, growth, and fecundity under field conditions for the polychaete Janua sp.

Larger offspring became larger adults and had higher levels of fecundity than those from smaller offspring, though the effect on fecundity was weaker and more variable over different experimental runs. Adults derived from larger larvae had shorter lifespans than adults derived from smaller larvae.

Our results suggest that the maternal effect of offspring size can influence the frequently observed trade-off between longevity and fecundity.

Future studies should seek to measure the effects of offspring size over as much of the life history as possible in order to avoid misestimating the relationship between offspring size and fitness.

Full paper

Kesselring H, Wheatley R, Marshall DJ (2012) Initial offspring size mediates trade-off between fecundity and longevity in the field. Marine Ecology Progress Series, 465: 129–136  email for a copy doi: 10.3354/meps09865