Hydrologically defined niches reveal a basis for species richness in plant communities

Article Abstract:

Resource-based competition theory predicts a stable coexistence between species depending on each being a superior competitor in its own niche. However observed niche overlaps are high and exclusion of all but the best competitor is predicted. Theoretical solutions involve a degree of niche separation in time or space. Niche separation is found in community structure, suggesting smaller than expected niche overlaps and a trade off between resource use by species on orthogonal axes. Both these condition were found in a species-rich plant community.

Niche (Ecology), Niches (Ecology)

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Eel-like swimming in the earliest ichthyosaurs

Article Abstract:

Specimen study of the earliest known ichthyosaurs, Chensaurus chaoxianensis, reveals that their evolution is a transition between shorter-bodied terrestrial stock which led to group evolution to thunniform ichthyosaurs. The specimen has a partial skin impression, a small caudal fin, a long and narrow body, and a high presacral vertebral count, indicating an anguilliform swimming mode. The advanced ichthyosaurs had a rigid thunniform bauplan and a deep fusiform body. Thus, their evolution depended on the evolution of discoidal vertebrae.

Evolution (Biology), Reptiles, Reptiles, Fossil, Fossil reptiles

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Marine species richness

Article Abstract:

Estimates of deep sea species have frequently been based on limited samples from the North Atlantic that do not reflect oceanic biodiversity. These samples have been used to extrapolate both the number and types of species expected to be found despite other samples from the South Pacific that refute those estimates. Therefore, a broader sampling technique is necessary to estimate the biodiversity of marine species and their approximate populations.

Natural history, North Atlantic Ocean, South Pacific Ocean

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