[News] Randomness reigns in ecology

[Moontanman]

Randomness reigns in ecology

 

The environment is not the only key factor in determining which species will populate a given habitat -- random, stochastic processes may also play a significant role, according to a study published online today (May 27) on the Science Express website. Study author Jonathan Chase, a community ecologist at Washington University in Saint Louis, talked with The Scientist about why randomness is so important to species composition, and what the findings mean for conserving and restoring the world's ecosystems.

 

 

Read more: Q&A: Randomness reigns in ecology - The Scientist - Magazine of the Life Sciences Q&A: Randomness reigns in ecology - The Scientist - Magazine of the Life Sciences

[Rade]

The reply by Hollenberg below makes a number of good points. What Chase really did was alter the randomness of species diversity initial conditions by adding different types of species from day 1. This is a different ball of wax than saying their was natural randomness of species diversity in the nearby field available to colonize the tanks (nearby to the experimental tanks)--which there must have been--however, the experiment design of Chase does not allow one to study this effect (unless Chase had a number of control tanks where he altered nutrients but did not alter the species initial conditions ??). If Chase found higher diversity of change in tanks where he added high levels of nutrients (but did not alter species initial randomness), in relation to tanks with low nutrients added--then he would have an argument that randomness of colonization plays an important role in regulation of species diversity over ecological (succession) time. As it stands, until I read his paper, his claims about randomness are unclear to me given the nature of his experimental design.

 

For me, the take home lesson from the Chase experiment is that humans should not add nutrients to bodies of waters such as ponds/lakes in excess of what enters the systems naturally (whatever natural background conditions may be for the watershed in question)--not if they want to have predictable ecosystems year after year.

 

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Chase: you've mistaken ecological network effects for some randomness

by DENNIS HOLLENBERG

 

[Comment posted 2010-05-29 11:48:45]

The ecological variables of manipulating the ponds include a. the order in which species are added and b. the nutrient-addition permutations:

 

a. varying the order in which species are added subtly changes the details of species subsequent interactions which induce additional variation in the way in which subsequently added species interact. What you're really doing here is manipulating the successionary dynamics of (~primary) ecological succession.

 

The resulting emergent variation is likely disproportionately due to the founder effect (traditionally associated with evolutionary process but more recently in theoretical ecological succession as the "network founder effect" *). Additional variables are inadvertently introduced through the variation among the individuals added, e.g., the specimens easiest to catch for transporting to the study site are subtly different from those left behind and introduced into other ponds.

 

b. These inadvertent 'deterministic' variations could then be magnified through the mechanism of nutrient manipulation due to original or successionary variation.

 

BTW, the same phenomena likely occur in organism development; it likely provides an important and non-DNA source of variation among conspecifics (perhaps personality predisposition and orientation as well).

 

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*Hollenberg 2007 "On the evolution and dynamics of biological networks" _Revista di Biologia/Biology Forum_ 100(1) 93-118 (see page 102ff)

-- please e-mail me for a copy.