Offspring size in a resident species affects community assembly

Authors: Kurt Davis and Dustin J Marshall

Published in: Journal of Animal Ecology, volume 83, issue 2 (March 2014)

Abstract

Offspring size is a trait of fundamental importance that affects the ecology and evolution of a range of organisms. Despite the pervasive impact of offspring size for those offspring, the influence of offspring size on other species in the broader community remains unexplored. Such community-wide effects of offspring size are likely, but they have not been anticipated by theory or explored empirically.

For a marine invertebrate community, we manipulated the size and density of offspring of a resident species (Watersipora subtorquata) in the field and examined subsequent community assembly around that resident species.

Communities that assembled around larger offspring were denser and less diverse than communities that assembled around smaller offspring. Differences in niche usage by colonies from smaller and larger offspring may be driving these community-level effects.

Our results suggest that offspring size is an important but unexplored source of ecological variation and that life-history theory must accommodate the effects of offspring size on com- munity assembly. Life-history theory often assumes that environmental variation drives intra- specific variation in offspring size, and our results show that the converse can also occur.

Full paper

Davis K, Marshall DJ (2014) Offspring size in a resident species affects community assembly. Journal of Animal Ecology, 83, 322–331 PDF PDF 274 KB doi:10.1111/1365-2656.12136

Phenotypic links among life-history stages are complex and context-dependent in a marine invertebrate: interactions among offspring size, larval nutrition and postmetamorphic density

Authors: Richard M Allen and Dustin J Marshall

Published in: Functional Ecology, volume 27, issue 6 (December 2013)

Abstract

Examples of simple phenotypic relationships, where variation in one stage directly affects phenotypic variation in a subsequent stage, are documented in most taxa. However, environmental variation can mediate these relationships, and because most organisms develop through multiple life-history stages, each stage-dependent environment has the potential to create new phenotypic relationships and interfere with existing relationships.

Despite the likelihood of complex phenotypic interactions among life-history stages, and the potential for these interactions to resonate throughout the life history, there are few tests of the problem and few predictions of how these phenotypic interactions are resolved.

Hydroides diramphus

Hydroides diramphus, a polychaete tube worm found in cosmopolitan benthic marine assemblages. Image by Richard Allen.

Here, we examined the interdependent effects of three sources of phenotypic variation on the performance of a marine tube worm. Sources of phenotypic variation included: offspring size, larval nutrition and juvenile density.

We found highly context-dependent relationships between these factors and postmetamorphic performance. Within the overarching result of context dependence, we found: interactions could negate and reverse relationships; early-stage phenotypes could persist to postmetamorphosis; later, life-history environments could contribute more to recruit phenotypes than early-stages; and late-stage variation can depend on early-stage phenotypes.

Our results demonstrate that while simple phenotypic links among the egg, larval and post-recruitment stages may be common and important contributors to growth and survival, these relationships should be considered in the context of the organism’s life experience. Each phenotypic link among stages can potentially be complex and depend on prior experience, current state and the subsequent environments experienced.

Full paper

Allen R, Marshall DJ (2013) Phenotypic links among life-history stages are complex and context-dependent in a marine invertebrate: interactions among offspring size, larval nutrition, and post-metamorphic density. Functional Ecology, 27(6): 1358–1366 PDFPDF 390 KB doi: 10.1111/1365-2435.12117

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

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

The biogeography of marine invertebrate life histories

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

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

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