Innarestin', CJ, thanks.

Though the hypothesis concerning size evolution on islands was hardly "magical" thinking, since there was a clear naturalistic rationale given for the claimed effects (predator-free smaller animals no longer being selected for their ability to be unobtrusive; larger animals being selected against due to limited resources).

Also, the abstract for the article
http://www3.interscience.wiley.com/journal/123356145/abstract?CRETRY=1&SRETRY=0
specifically states that the researchers did not rule out island dwarfing (as suggested for H. floresiensis, for example) -- in fact, to the contrary:

We did find consistent evidence that large (> 10 kg) mammals grow smaller on islands. Smaller species, however, show no consistent tendency to either dwarf or grow larger on islands.

My bold.

To this extent, at least, the article's conclusions are over-extended in the Science Daily discussion.

And the way the *magical* island-size hypothesis that they were testing was expressed is a much different formulation than the typical way of expressing the smaller-get-bigger-bigger-get-smaller generalization that I have encountered:

Optimal body size theories predict that large clades have a single, optimal, body size that serves as an evolutionary attractor, with the full body size spectrum of a clade resulting from interspecific competition. Because interspecific competition is believed to be reduced on islands, such theories predict that insular animals should be closer to the optimal size than mainland animals. We test the resulting prediction that insular clade members should therefore have narrower body size ranges than their mainland relatives.

I have frankly never seen the claim that there is some environment-free "optimal" size for any given clade, and certainly the claim that the environmental constraints keeping some animals small are loosened on islands is not easily transformed into a claim that there is an "optimal" size that the constraints are suppressing.

Since the article itself is beyond a paywall for me, I don't doubt -- or, at least, have no basis for refuting -- that the authors supply cites to support their characterization of the "optimal clade size" hypothesis. I've just never heard of it being expressed that way.

Wasn't it recently shown that Komodo Dragons are not in fact a product of Island evolution in any case? That they in fact evolved in Australia, spread to the Indonesian archipelago, and then went extinct in most of it's former range (including Aus), leaving only the current population on a few Indonesian islands?

I don't recall the exact details, or where I heard it. Maybe someone will dig up a link.

I think the article is targetting the idea of an optimal body size being the sole mechanism responsible for the island rule as being 'magical thinking', which is quite right. The following article provides references to articles that claim an optimal body size, for which the article is refuting:

http://www.tau.ac.il/lifesci/department ... fitall.pdf

it would be a silly notion to think of the island rule itself to be 'magical thinking', as the island rule only describes a pattern - a tendency for size increase in small organisms and size decrease in large organisms. The rule is a 'rule' for a reason - it has exceptions and it says nothing about the processes.

It is well known that the underlying processes are complex. Some key factors include decreased interspecific competition (Grant 1965), thermoregulation, and dominance over resources in high-density populations. The reason there is a general pattern of island evolution (divergence of island species from their mainland counterparts) is that many islands have similar characteristics, differing from the mainland (such as reduced species diversity, increased abundance within species, and reduced resource availability).