Comments on Feb 1 version

Posted by kotanen at February 10. 2010

I've taken a quick look at the wiki, and have a few general comments.

1) Can we make this a real wiki that can be co-edited at some point, rather than a .doc file? Or am I doing something wrong?

2) Purpose (and Summary)

I think it's also worth acknowledging publication bias. People tend to study problem species. This gives the erroneous impression that most invaders cause problems. As well, it makes meta-analysis difficult. It might be worth trying to quantify the fact that in floras with hundreds of invasive species (like mine), only a handful get studied as invaders, and these tend to be the most serious problems. We ought to encourage study of non-problem species.

3) Summary

I'm made uncomfortable by statements such as:

"To address this question, studies of biological invasions often employ a comparative approach, such as the comparison of life-history traits between native and introduced species or populations of species. We argue that the comparative approach is predicated on a native-introduced dichotomy that is unproven or demonstrably false in many important ways."

There's nothing wrong with testing whether exotics and natives differ; this isn't a false dichotomy, it's a hypothesis. If we want to answer the title question based on data, we have to ask this question. If the answer is "no", so be it. We should be arguing against assuming a difference, and against biased tests of this difference, not against testing a difference per se.

4) Section 2 (and following)

"Species may do the same thing (Phragmites, beavers, ragweed, etc.) in their native and introduced ranges.... The impacts of an exotic species (#1 in Sec 1) would therefore be completely a result of perception and not an ecological or evolutionary phenomenon.".

This doesn't follow. Introducing a problem species to a new area can cause new problems for that area. Just because they are doing the same thing in native and exotic regions doesn't mean they aren't a problem in both. Impacts of ragweed in Europe or beavers in South America aren't imaginary; they're real, and potentially serious. Further, if their impact is novel in the new region, it may represent an unprecedented challenge to invaded ecosystems without any change in the invader's behaviour. Peter Vitousek made this point years ago regarding N-fixers in Hawai'i, for example. Perhaps a better point is that problems often may be predicted by study of invaders as native species in their native ranges.

5) Section 2

"What data EXIST and what data are NEEDED to answer these questions?

What is the appropriate control group? – native vs. introduced genotypes? native and introduced competitors in the same community? invaders vs. abundant natives?"

This is a good question, and worth discussion. A related issue is when (or if) phylogenetic control is needed. I think it depends on the hypothesis. For example, if you want to ask whether an invasive species has changed during the invasion, it makes sense to compare native and introduced populations of the same species. If you want to ask why an invader success of fails in a new community, it makes sense to compare it with competing natives. Perhaps the issue of correct treatments and controls is one we could clarify

That's it for now, but it's a start!

Peter M. Kotanen

Department of Ecology and Evolutionary Biology

3359 Mississauga Road North

Mississauga, ON, L5L 1C6 CANADA

tel: 905-828-5365; fax: 905-828-3792

lab: 905-828-5304

e-mail: peter.kotanen@utoronto.ca

http://www.utm.utoronto.ca/~w3pkota/

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Comments on Feb 1 version

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