Species Live Where There is Rain

A new study has found that during the time of Pangaea the supercontinent, animals tended to congregate where there was rain — this is despite the fact that there was many times more space for them to spread out and no landmarks to prevent them from travelling.

The research focused on the waste disposal of mammals and reptiles, and found that because mammals pass water than reptiles, they need a water-rich environment to replenish what they have lost.

Scientists studied a transect of Pangaea that stretched from about 3 degrees south to 26 degrees north, a large area of the supercontinent which contained both tropical and semiarid temperate zones.

The scientists determined that reptiles, as represented by a species which was called procolophonids, lived in an area of the supercontinent where monsoon-like rains only occurred once a year, while mammals, as represented by a precursor species called traversodont cynodonts, lived in a region where major rains occurred twice a year.

“We’re answering a question that goes back to Darwin’s time,” said Jessica Whiteside at Brown University, assistant professor of geological sciences at Brown, who studies ancient climates. “What controls where organisms live? The two main constraints are geography and climate.”

“It’s interesting that something as basic as how the body deals with waste can restrict the movement of an entire group,” Whiteside said, noting that in water-limited areas, “the reptiles had a competitive advantage over mammals,” Whiteside said.

The data for Pangaea comes from samples collected from lakes and ancient rift basins which currently stretch from Georgia to Nova Scotia, and represent a period of time during the late Triassic period, from 234 million years ago to 209 million years ago.

During this time in Earth’s history, temperatures were approximately 20 degrees Celsius hotter in the summer, and atmospheric carbon dioxide existed in 5 to 20 times greater quantities than it does today. Unsurprisingly then, this research is a good indicator of what the animals on planet Earth could once again be facing as the global climate continues to change and warm.

“There is evidence that climate change over the last 100 years has already changed the distribution of mammal species,” said Danielle Grogan, a graduate student in Whiteside’s research group. “Our study can help us predict negative climate effects on mammals in the future.”

Source: Brown University

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