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Trait means and reaction norms: the consequences of climate change/invasion interactions at the organism level


How the impacts of climate change on biological invasions will play out at the mechanistic level is not well understood. Two major hypotheses have been proposed: invasive species have a suite of traits that enhance their performance relative to indigenous ones over a reasonably wide set of circumstances; invasive species have greater phenotypic plasticity than their indigenous counterparts and will be better able to retain performance under altered conditions. Thus, two possibly independent, but complementary mechanistic perspectives can be adopted: based on trait means and on reaction norms. Here, to demonstrate how this approach might be applied to understand interactions between climate change and invasion, we investigate variation in the egg development times and their sensitivity to temperature amongst indigenous and introduced springtail species in a cool temperate ecosystem (Marion Island, 46°54′S 37°54′E) that is undergoing significant climate change. Generalized linear model analyses of the linear part of the development rate curves revealed significantly higher mean trait values in the invasive species compared to indigenous species, but no significant interactions were found when comparing the thermal reaction norms. In addition, the invasive species had a higher hatching success than the indigenous species at high temperatures. This work demonstrates the value of explicitly examining variation in trait means and reaction norms among indigenous and invasive species to understand the mechanistic basis of variable responses to climate change among these groups.

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We thank Erika Nortje, Heidi Sjursen Konestabo and various members of the Marion Island relief teams for assistance in the field. Bettine Jansen van Vuuren and Angela McGaughran assisted with the COI sequence data and phylogenetic analysis. Janne Bengtsson, Melodie McGeoch and two anonymous referees provided useful comments on a previous version of the ms. The South African National Antarctic Programme provided logistic support. This work was funded partly by a SA-Norway science liaison grant awarded jointly to HPL and SLC. The work forms a contribution to the SCAR EBA Programme.

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Correspondence to Charlene Janion.

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Janion, C., Leinaas, H.P., Terblanche, J.S. et al. Trait means and reaction norms: the consequences of climate change/invasion interactions at the organism level. Evol Ecol 24, 1365–1380 (2010).

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  • Biological invasions
  • Climate change
  • Development rate
  • Phenotypic plasticity
  • Soil arthropod