Examining the link between climate change and species invasions

Ciona intestinalis

Ciona intestinalis was one of the non-indigenous species studied in this study. This species has been introduced to all continents except Antarctica and is a significant fouling organism that quickly coats marine structures forming dense aggregates. It is now abundant in harbours and lagoons around the world. Dense growths of this species have been reported to cause important economic impact on aquaculture facilities in Canada and South Africa. (Photo credit: Prof. Charles Griffiths)

Temperature is one of the most important factors affecting species distributions. Climate change is expected to cause poleward and upslope shifts in native species ranges. Non-indigenous species provide an opportunity to witness the establishment of range boundaries in a way that cannot be observed for native species.

In an international collaborative project led by researchers from the C·I·B, regional and global distribution patterns of marine organisms were compared with genetic, climatic and physiological data to understand how climate change affects non-indigenous species. The results, published in Global Ecology and Biogeography, showed that non-indigenous species with a variety of thermal tolerances and distributions have expanded their ranges and increased in abundance as seawater temperature patterns have changed. The authors found little variation in shipping movement through time, suggesting that human-mediated transport did not increase during the study period.

This study provides evidence that non-indigenous marine species, regardless of their thermal tolerance, range size and genetic variability, are expanding their ranges and increasing in abundance. This trend is not linked to human-mediated transport but is rather concurrent with changes in seawater temperature, which suggests that climate change increases non-indigenous species spread and abundance across multiple spatial scales.

Dr. Marc Rius was a Centre for Invasion Biology postdoctoral fellow and is currently a Lecturer at the University of Southampton, United Kingdom.

Dr. Susana Clusella-Trullas is a Senior Lecturer at Stellenbosch University and a core team member of the Centre for Invasion Biology.

Prof. Charles Griffiths is a Professor at the University of Cape Town and a core team member of the Centre for Invasion Biology.

Read the paper:

Rius M, Clusella-Trullas S, McQuaid CD, Navarro R, Griffiths CL, Matthee CA, von der Heyden S, Turon X. Range expansions across ecoregions: interactions of climate change, physiology and genetic diversity. Global Ecology and Biogeography.

For more information, contact Marc Rius at

Distribution of the studied non-indigenous species (ascidians) along the world’s coastlines. Such widespread and disjunct distributions cannot be understood solely through natural dispersal. Ascidians are sessile as adults, and the motile microscopic stages (embryonic and lecithotrophic larval stages) last from just minutes to a few days, which allows for short-distance dispersal. Therefore, long-distance dispersal of these species is solely human mediated.

Distribution of the studied non-indigenous species (ascidians) along the world’s coastlines