Individuals from non-native populations are stronger and bigger than individuals from native populations of a widespread seaweed

Academic Article

Abstract

  • Many species introduced to non-native regions undergo profound phenotypic change, but conflicting evidence remains on the frequency of such trait differentiation. Here, we describe two phenotype categories—biomechanical material properties and organismal size—that differ between and within native Japanese and non-native North America and Europe shorelines of the macroalga Gracilaria vermiculophylla. Biomechanical traits represent capacity to withstand wave energy and disperse by fragmentation, while body size in algae can reflect capacity for reproduction. Field-collected thalli from 43 populations were assayed for peak force (breaking force), peak stress (strength), breaking energy (strain energy storage), and modulus (stiffness). Thalli attached to hard substratum were approximately 27% stronger than thalli that were drifting, and non-native thalli were approximately 50% stronger and approximately 23% stiffer than native thalli. Non-native thalli had 28% more surface area than did native thalli. Interestingly, the population means of thallus strength and size were not tightly correlated; this suggests that their expression, evolution, or both is not tightly coupled. Stronger thalli were found in areas with cooler sea surface temperature, while the largest thalli were found in the cooler, northern European latitudes. This study stands alongside a surprisingly small number of studies that directly compare material properties between native versus non-native populations within a species, despite the potential importance of material properties in mediating invasion success. Future work would benefit from estimates of fitness in the field and address whether biogeographic shifts in material phenotypes reflect adaptive or non-adaptive processes and are either driving or reflecting invasion success.
  • Digital Object Identifier (doi)

    Author List

  • Murren CJ; Krueger-Hadfield SA; Clark AJ; Flanagan BA; Lees LE; Sotka EE
  • Start Page

  • 2169
  • End Page

  • 2180
  • Volume

  • 24
  • Issue

  • 7