Examining the link between climate change and species invasions
Temperature is one of the most important factors affecting species distributions. Climate change is expected to change temperature regimes and 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 such as shipping but is rather linked with changes in seawater temperature, which suggests that climate change increases non-indigenous species spread and abundance.
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
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.
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