Magazine article Earth Island Journal

A Rare Advantage

Magazine article Earth Island Journal

A Rare Advantage

Article excerpt

Here's one for the "small is good" category. We usually think species that exist only in small numbers are in danger of going extinct. But apparently, sometimes being rare may hold the ticket to a species' survival.

When most people think of rare species, they think of ones endangered as a result of habitat loss, hunting, poaching, climate change, or other environmental disturbances. But some species have always been rare--occurring in small densities within their range--throughout their evolutionary history.

In a perspective paper published in the journal Ecology Letters, a team of researchers from the University of California, Davis suggests that for many species, such as a Tritonia nudi-branch--a small member of the mollusk family that's spotted in the Red Sea only once every few years--rarity is not a guarantee of impending extinction. Instead, the traits that enable some species to be what they term "chronically rare" could very well be an advantage during crises.

The researchers explored factors that make a species likely to thrive, even if its population is small.

Rare species, they found, can persist if fertilization occurs inside or close to an adult, which exponentially increases the chances of the gametes of both sexes actually getting to unite to form a zygote, and of that new life being protected. This might seem obvious, but many species, including sea urchins and abalone, use "broadcast fertilization," where they simply release their gametes into the water and hope for the best. …

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