succession

dustinmeeg

Spatial pattern of distribution of marine invertebrates within a subtidal community: do communities vary more among patches or plots?

Authors: Chun‐Yi Chang and Dustin J Marshall

Published in: Ecology and Evolution, volume 6, issue 22 (November 2016)

Abstract

Making links between ecological processes and the scales at which they operate is an enduring challenge of community ecology.

Our understanding of ecological communities cannot advance if we do not distinguish larger scale processes from smaller ones.

Variability at small spatial scales can be important because it carries information about biological interactions, which cannot be explained by environmental heterogeneity alone.

Marine fouling communities are shaped by both the supply of larvae and competition for resources among colonizers—these two processes operate on distinctly different scales.

Here, we demonstrate how fouling community structure varies with spatial scale in a temperate Australian environment, and we identify the spatial scale that captures the most variability. Community structure was quantified with both univariate (species richness and diversity) and multivariate (similarity in species composition) indices.

Variation in community structure was unevenly distributed between the spatial scales that we examined. While variation in community structure within patch was usually greater than among patch, variation among patch was always significant.

Opportunistic taxa that rely heavily on rapid colonization of free space spread more evenly among patches during early succession. In contrast, taxa that are strong adult competitors but slow colonizers spread more evenly among patches only during late succession.

Our findings show significant patchiness can develop in a habitat showing no systematic environmental spatial variation, and this patchiness can be mediated through different biological factors at different spatial scales.

Citation

Chang CY, Marshall DJ (2016) Spatial pattern of distribution of marine invertebrates within a subtidal community: do communities vary more among patches or plots? Ecology and Evolution 6(22): 8330–8337 PDF 522 KB doi: 10.1002/ece3.2462

dustinmeeg

Faster is not always better: selection on growth rate fluctuates across life history and environments

Authors: Keyne Monro and Dustin J Marshall

Published in: The American Naturalist, volume 183, number 6 (June 2014)

Abstract

Growth rate is increasingly recognized as a key life-history trait that may affect fitness directly rather than evolve as a by-product of selection on size or age.

An ongoing challenge is to explain the abundant levels of phenotypic and genetic variation in growth rates often seen in natural populations, despite what is expected to be consistently strong selection on this trait. Such a paradox suggests limits to how contemporary growth rates evolve.

We explored limits arising from variation in selection, based on selection differentials for age-specific growth rates expressed under different ecological conditions. We present results from a field experiment that measured growth rates and reproductive output in wild individuals of a colonial marine invertebrate (Hippopodina iririkiensis), replicated within and across the natural range of succession in its local community.

Colony growth rates varied phenotypically throughout this range, but not all such variation was available for selection, nor was it always targeted by selection as expected.

While the maintenance of both phenotypic and genetic variation in growth rate is often attributed to costs of growing rapidly, our study highlights the potential for fluctuating selection pressures throughout the life history and across environments to play an important role in this process.

Full paper

Monro K, Marshall DJ (2014) Faster isn’t always better: selection on growth rate fluctuates across the life history and environments. The American Naturalist, 183(6): 798–809 PDFPDF 393 KB doi:10.1086/676006