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Researchers: Humans “speeding up” evolution

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sticklebacks in Enos Lake, Vancouver Island, Canada/Ernie Cooper

Depending on how we define species, extinction, as well as hybridization and evolution. From ScienceDaily:

New research from UBC shows that when humans speed up the usually slow process of evolution by introducing new species, it can result in a lasting impact on the ecosystem. The phenomenon is known as reverse speciation and researchers witnessed it in Enos Lake on Vancouver Island where two similar species of threespine stickleback fish disappeared within three years.”When two similar species are in one environment, they often perform different ecological roles,” said Seth Rudman, a PhD student in zoology at UBC. “When they go extinct, it has strong consequences for the ecosystem.”

Two species of endangered threespine stickleback fish lived in the lake. One lived in the middle of the lake and ate mostly zooplankton while the other lived closer to the shore, eating insects that spent their larval stage in the water. In the mid-1990s, crayfish were introduced to the lake. Between 1994 and 1997, researchers documented how both species disappeared as a result of interbreeding, leaving only a hybrid species.

If the hybridization happened so quickly (resulting in two “extinctions”), what justifies the fish being classified as separate species before? When one asks this question, one is always told that all evolutionary biologists recognize the problem, but never that anyone proposes to do anything about it. After a while, that makes communication difficult. And raises suspicious about the reason the problem is allowed to just go on (because it greatly reduces the evidence bar for these kinds of claims?).

In this study, published recently in Current Biology, researchers document how the shift from two distinct species to one hybrid species has impacted the ecosystem. The new stickleback fish does not perform all of the functions as its predecessors. The hybrid spends more time near the shore of the lake and eats more large insects. As a result, the number of small insects coming out of the lake has increased, showing how the changes in the lake can also cause changes to the terrestrial ecosystem. With the new hybrid, researchers have also found that the leaves that fall into the lake do not decompose as quickly. More.

Hmmm. One would suggest coming back in a couple of decades to see what actually happened in the meantime. It sounds like a niche has opened up for a life form that eats small insects.

See also: Jaguars, cougars survived Ice Age by adjusting diets

and

What really happened to wildlife 25 years after Chernobyl?

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Here’s the abstract:

Young species are highly prone to extinction via increased gene flow after human-caused environmental changes [ 1–6 ]. This mechanism of biodiversity loss, often termed reverse speciation or introgressive extinction, is of exceptional interest because the parent species are typically highly differentiated ecologically. Reverse speciation events are potentially powerful case studies for the role of evolution in driving ecological changes, as the phenotypic shifts associated with introgressive extinction can be large and they occur over particularly short timescales. Furthermore, reverse speciation can lead to novel phenotypes [ 1, 2 ], which may in turn produce novel ecological effects. Here we investigate the ecological shift associated with reverse speciation in threespine stickleback fish using a field study and a replicated experiment. We find that an instance of introgressive extinction had cascading ecological consequences that altered the abundance of both aquatic prey and the pupating aquatic insects that emerged into the terrestrial ecosystem. The community and ecosystem impacts of reverse speciation were novel, and yet they were also predictable based on ecological and morphological considerations. The study suggests that knowledge about the community ecology and changes in functional morphology of a dominant species may lead to some predictive power for the ecological effects of evolutionary change. Moreover, the rapid nature and resultant ecological impacts associated with reverse speciation demonstrates the interplay between biodiversity, evolutionary change, and ecosystem function. – Seth M. Rudman, Dolph Schluter. Ecological Impacts of Reverse Speciation in Threespine Stickleback. Current Biology, 2016; 26 (4): 490 DOI: 10.1016/j.cub.2016.01.004

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