Evolution took a long time; catagorizing econiches (Introduction)

by David Turell @, Monday, October 09, 2017, 17:47 (164 days ago) @ David Turell

In any environment there are only limited ways an animal can adapt:


"Many seemingly different species actually live very similar lives. This convergence suggests that it may someday be possible to predict how many species live in a particular habitat, and even to identify the holes left by missing species.

"For more than half a century, ecologists have tended to describe ecological roles, or “niches”, as though they were properties of individual species. For example, chameleons are camouflaged, tree-dwelling lizards that ambush insects, while horned lizards are ground-dwelling desert creatures that eat ants and bear protective spines. The diversity can seem overwhelming.

"But Eric Pianka, an evolutionary ecologist at the University of Texas in Austin, has long wondered whether there might only be a certain, limited set of niches.


"Over and over, they saw pairs of unrelated lizards converge on similar niches. Out of the 134 species, 100 belonged to a convergent pair, far more than could have happened by chance.
For example, African chameleons have ecological equivalents in the Americas called bush anoles, and Australia’s thorny devil fills almost precisely the same niche as North America’s horned lizards.

"If lizards could evolve into an unlimited number of niches, this convergence would be unlikely. Instead, their result suggests that lizards are constrained to live particular lifestyles. For instance, there are no marine lizards or lizards that behave like elephants. “There’s only a certain number of ways to be a lizard,” says Pianka.

“'This is beautiful,” says evolutionary biologist George McGhee at Rutgers University in New Jersey. “It’s astonishing the number of species that have converged into ecological roles.”
Ecologists could apply the same approach to other groups, like birds or rodents. However, each group is likely to have its own unique set of niche features – for example, many birds make long migrations, and some rodents hibernate – which would complicate the analysis, says Pianka.

"The limited number of niches implies that ecologists may someday be able to construct a “table of niches”, somewhat analogous to chemistry’s periodic table of elements. “If we constructed this table, and we thought it was fairly complete, then we could go into places and look at the structure of the habitat, the temperatures and so on, and say ‘this place ought to be able to support 10 species of lizards’,” says Vitt. Ecologists could then predict far more about the natural world than they can today.

"Moreover, such a table would highlight “empty” niches where species ought to occur but do not. These gaps could point to niches that were once filled by a species that has died out, but so recently that evolution has not yet refilled the niche, says Vitt.

"However, the findings do not necessarily mean that extinct species can be easily replaced by their ecological equivalents, says Vitt. Such “plug and play” replacements have been attempted on Indian Ocean islands, where giant tortoises wiped out by human activity have been substituted by tortoises from other islands. The problem is, even if the new species fills the same niche, it may respond differently to competitors, predators and prey – leading to unpredictable changes in the ecosystem."

Comment: Long ago I noted that basic designs were set up at the start of multicellular life. Our skeletons compare easily to lizards. All lizards are similar and adapt to different environments. Viewed this way evolution doesn't look quite so bushy. God set up a simple path to follow in the beginning.

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