Balance of nature: importance of ecosystems (Introduction)

by David Turell , Thursday, August 26, 2021, 19:30 (1184 days ago) @ David Turell

They are delicate when balanced only by nature. Humans mess them up introducing foreign species:

https://www.nature.com/articles/d41586-021-02317-9?utm_source=Nature+Briefing&utm_c...

"The list of ‘deadly animals in Australia’ just got a little weirder. The cane toad, a toxic, invasive species notorious for devouring anything it can fit in its mouth — household rubbish, small rodents and even birds — has become highly cannibalistic in the 86 years since it was introduced to the continent, according to a new study. Its counterpart in South America, where cane toads originated, is far less cannibalistic.

***

"Farmers first introduced about 100 cane toads (Rhinella marina) to Australia from their native range in South America in 1935 to control cane beetles (Dermolepida albohirtum), which were wreaking havoc on sugarcane plantations. The giant toads failed to knock down the beetle populations, but they succeeded in epically multiplying. Because of their highly poisonous skin, which is coated in bufotoxins, they had no natural predators and went on to invade large swaths of the northern and eastern parts of the country.

"Although adult cane toads are fearsome — they grow up to 25 centimetres in length — it’s their tadpoles that are usually the cannibals. Multiple tadpoles together can gobble more than 99% of the hatchlings that emerge from the tens of thousands of eggs in a single clutch.

***

"Although the speed with which the toads evolved this behaviour is impressive, the team was even more surprised by how fast the animals evolved a defence to protect against it. The researchers found that when invasive Australian hatchlings shared a tank with caged, older tadpoles from the same group, the hatchlings were more likely to have a shorter developmental period than that of the South American hatchlings. Older tadpoles don’t tend to eat older tadpoles — so the toads might have evolved to speed up their hatchling phase, the researchers found. This would limit the amount of time they spend vulnerable to cannibalism, even if the adaptation eventually stunts their growth, says DeVore.

***

"Although there are still mysteries around the cane toads’ cannibalistic tendencies, one thing is for certain, says Shine: “The cane toads that are currently hopping across Australia are extraordinarily different animals from the ones that were first taken out of the native range.'”

Comment: The usual problem when foreign species are introduced is damage to the finely balanced natural system. These ecosystems are the Earth's necessary food supply for the huge bush of existing life on Earth.