Invasive ecosystem engineer selects for different phenotypes of an associated native species

Abstract

Abstract. Invasive habitat-forming ecosystem engineers modify the abiotic environment and thus represent a major perturbation to many ecosystems. Because native species often persist in these invaded habitats but have no shared history with the ecosystem engineer, the engineer may impose novel selective pressure on native species. In this study, we used a phenotypic selection framework to determine whether an invasive habitat-forming ecosystem engineer (the seaweed Caulerpa taxifolia) selects for different phenotypes of a common cooccurring native species (the bivalve Anadara trapezia). Compared to unvegetated habitat, Caulerpa habitat has lower water flow, lower dissolved oxygen, and sediments are more silty and anoxic. We determined the performance consequences of variation in key functional traits that may be affected by these abiotic changes (shell morphology, gill mass, and palp mass) for Anadara transplanted into Caulerpa and unvegetated habitat. Both linear and nonlinear performance gradients in Anadara differed between habitats, and these gradients were stronger in Caulerpa compared to unvegetated sediment. Moreover, in Caulerpa alternate phenotypes performed well, and these phenotypes were different from the dominant phenotype in unvegetated sediment. By demonstrating that phenotype-performance gradients differ between habitats, we have highlighted a role for Caulerpa as an agent of selection on native species.

Under niche construction: an operational bridge between ecology, evolution, and ecosystem science

“…Recent research on the reciprocal interactions between ecological and evolutionary dynamics is increasingly filling this gap (Hairston et al 2005, Schoener 2011, Becks et al 2012), but more studies are needed that examine how chemical modifications of the environment by organisms affect the evolution of consumer resource demand (Mizuno andKawata 2009, Matthews et al 2011b), and how physical modification of the environment by ecosystem engineers can modify selection gradients of the engineers themselves or of other organisms (Wright et al 2012). …”

“…However, there is little experimental evidence showing how bioturbation activities can affect selection pressures (Criterion 2) in a way that would affect evolutionary responses (Criterion 3). There are, however, experimental studies that measure changes in selection pressures caused by organism-mediated modifications to the environment, illustrative of the type of research needed to address the second criterion (Wright et al 2012). In a study on ecosystem engineers, Wright et al (2012) showed that invasive seaweeds (Caulerpa taxifolia) modify the physical and chemical characteristics of coastal marine sediments, and, in so doing, alter selection gradients on native bivalves (Anadara trapezia).…”

“…There are, however, experimental studies that measure changes in selection pressures caused by organism-mediated modifications to the environment, illustrative of the type of research needed to address the second criterion (Wright et al 2012). In a study on ecosystem engineers, Wright et al (2012) showed that invasive seaweeds (Caulerpa taxifolia) modify the physical and chemical characteristics of coastal marine sediments, and, in so doing, alter selection gradients on native bivalves (Anadara trapezia). Specifically, the relationships between several morphological traits (e.g., shell length, gill mass, and palp mass) and relative performance (i.e., change in biomass over time) of Anadara trapezia (the recipient of niche construction) differed in the presence and absence of Caulerpa taxifolia (the niche constructor).…”

Trait and abundance patterns in two marine molluscs: the influence of abiotic conditions operating across multiple spatial scales

“…Shell length was used as a measure of body size as morphological traits (e.g. length, width, height, total weight) are highly correlated in marine molluscs such as A. trapezia (Wright & Gribben 2008, Gribben et al 2009a, Wright et al 2012.…”

“…Shell length was used as a measure of body size as morphological traits (e.g. length, width, height, total weight) are highly correlated in marine molluscs such as A. trapezia (Wright & Gribben 2008, Gribben et al 2009a, Wright et al 2012.To investigate the effects of abiotic variation on the abundance and body size of Anadara trapezia and Batillaria australis, water temperature, pH, salinity, dissolved oxygen (DO) and sediment redox (a proxy for general sediment health) (Gribben et al 2009b, McKinnon et al 2009, Wright et al 2010 were measured in all habitats at all sites. All these abiotic variables can have important effects on marine invertebrates (Rainer et al 1979, Berge et al 2006, Harley et al 2006, Bibby et al 2007, Gribben et al 2009b, McKinnon et al 2009, Wright et al 2010.…”