How temperature extremes change the distribution of species

A recent study by McGill University and international collaborators provides a comprehensive understanding of how temperature extremes influence the distribution of species, particularly cold-blooded animals. 

This study, which is critical in the context of climate change, reveals intricate patterns in the role temperature plays in determining species habitats.

Focus of the study 

“Understanding how temperature determines the distribution of life is necessary to assess species’ sensitivities to contemporary climate change,” wrote the study authors.

“Here, we test the importance of temperature in limiting the geographic ranges of ectotherms by comparing the temperatures and areas that species occupy to the temperatures and areas species could potentially occupy on the basis of their physiological thermal tolerances.”

This method offered insights into how species’ distribution is influenced by temperature and other factors. The research was focused on 60 cold-blooded species from different geographic realms. 

Environmental changes 

A key finding is the differential impact of temperature on terrestrial and marine species. 

While temperature directly impacts species in oceans, land animals like reptiles, amphibians, and insects show a lesser direct correlation with temperature for their habitat range. 

This distinction underscores the complex dynamics in how different species adapt to environmental changes.

Habitat choices

The experts also observed a notable pattern concerning species’ latitude and their distribution. Species higher in latitudes tend to avoid equatorial regions, even if the temperatures there are within their tolerance range. 

This suggests that factors other than temperature, such as negative interactions with other species, might be influencing their habitat choices.

Surprising patterns 

Study lead author Nikki A. Moore, a PhD student in the Department of Biology at McGill, highlighted the unexpected patterns linked to temperature across species. 

“It was not surprising to find that temperature doesn’t always limit species ranges, but what was surprising was that, despite the complexity, we found general patterns in the role that temperature plays across species,” said Moore.

“This research helps us to understand general patterns in how sensitive the distributions of different cold-blooded animal species might be to changes in temperature, which will help us to predict how the global distribution of species will change because of climate change.”

Species distribution 

The study sheds light on two conflicting hypotheses about species distribution.

“While it had long been thought that species ranges are less limited by temperature and more limited by species interactions in the tropics, the new work shows that higher-latitude species are increasingly excluded from their potential ranges in the tropics, supporting the idea of a trade-off between broad thermal tolerances and performance in the tropics,” said Moore.

Study implications 

According to the researchers, predicting and testing how species distributions respond to temperature requires good observations of where species live. 

The team noted that anyone can get involved in contributing to our knowledge of species distributions through citizen science, using applications such as iNaturalist.

The study is published in the journal Nature Ecology & Evolution.

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