The rich get richer, and the poor get poorer, the saying goes — and it looks like the same may hold true for marine species’ responses to climate change. Ocean animals that already enjoy large home ranges are claiming new territory faster than those that have historically stuck to a smaller area. “[N]arrow-range species may face double jeopardy in a warming ocean,” the study authors warn, since these animals are more likely to be wiped out by chance events and may not be able to relocate to cooler waters.

As the climate changes, many species are picking up and moving to new habitats. But their responses have been all over the map. Some animals have quickly staked new ground, others are expanding their territories slowly, and still others have migrated in unpredictable directions. To get a better grasp of what drives species’ reactions, researchers need to figure out if certain traits, such as diet, play an important role in these range shifts.

Studies of land-based animals haven’t produced consistent trends, but a team from Canada and Australia wondered if ocean animals might show clearer patterns. The researchers studied species off the coast of eastern Australia, an area that has been warming swiftly over the last several decades. They gathered data on 104 fish and invertebrate species from sources such as underwater surveys, reef monitoring programs, and studies of range shifts. Then the team investigated whether several traits — including mobility, body size, range size, and diet-related factors — were linked to the speed of each species’ range expansion.

Species moved poleward at an average of 24 kilometers per decade, the team reports in Ecology Letters. Animals with large ranges pushed the boundaries of their territories more quickly; for example, the Maori wrasse, yellowtail kingfish, and tiger shark each moved more than 92 kilometers per decade. Species that were omnivorous or could swim also tended to expand their ranges faster. The more scientists learn about what helps drive animals to new habitats, the better they can predict and prepare for such changes — and identify which species may find themselves stuck. — Roberta Kwok | 30 July 2015

Source: Sunday, J.M. et al. 2015. Species traits and climate velocity explain geographic range shifts in an ocean-warming hotspots. Ecology Letters doi: 10.1111/ele.12474.

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