While this seems an interesting and important area of study, I see
difficulties in making it an evolutionary study (as opposed to an ecological
study). To me, an evolutionary study implies that you can compare gene
frequencies in a population BEFORE the invasion with frequencies AFTER the
invasion. There are several problems with this: 1) How are you going to
sample gene frequencies from the 16 hundreds, which I'm guessing would be
about the time of the earliest invasions? 2) Even if you find a model where
invasion happened this long ago, that doesn't seem like many generations for
measurable change unless the interaction is very strong. 3) Assuming you
find measurable change, how will you know if it is caused by competition
with the invader, when there have been so many other environmental changes
as a result of the invasion of European humans and the concomitant changes
in land use patterns?
Just sampling present-day gene frequencies of populations with and
without invaders won't prove your case, since the populations might have had
these differences before the invasion.
An ecological study, on the other hand, could look at shifts in the
geographical distribution of populations, where there may be
presence/absence data from old records. Also, you might be able to
elucidate the means/mode of competition (i.e., for pollinators, dispersers,
habitat, use of soil minerals, etc.). Changes in morphology, as might be
revealed from old herbarium specimens, might reflect adaptive phenotypic
changes (without provable genetic basis) associated with habitat shifts,
though you would worry about whether old collections were statistically
representative of the old population.
Of course, Ms. Bean may have ways of addressing these issues, and
perhaps other readers of this listserv can point out some solutions or
useful approaches (and, of course, possibly other problems).
Martin M. Meiss
2010/4/7 Wayne Tyson <[email protected]>
> Howdy y'all:
>
> I presume that Bean is referring to alien invasive species, but in the
> purest sense, might one interpret the phenomenon more broadly? Indigenous
> colonizers seem to be the orphans of the phenomenon, but might the
> "evolutionary responses" to them be, in terms of evolutionary pressure, more
> "seasoned?"
>
> I must admit that I had not thought much about evolutionary responses of
> (particularly) native plant species until Bean's post, and I'm still
> thinking about it, but maybe Bean and others can expand my consciousness
> further on this particular topic.
>
> In a recent casual (insofar as they can be casual) trip to a southwestern
> desert to observe the rampage of Brassica tournefortii, I noticed some sharp
> "ecotones" between a depauperate-appearing Erodium species and an indigenous
> indicator species, Lasthenia sp. (glabrata?). The indigenous species
> appeared to be succeeding better in the "poorer" soils, whilst the weedy
> alien (of long standing) seemed to be thriving in apparently "better" soils.
> While this is nothing new, it may be an under-studied phenomenon ripe for
> investigation. (This was an accidental observation, however, while looking
> at a large colony of B. t.) Either of these species would bear closer
> observations in a more disciplined way, and I suspect that funding might
> more readily be found for B. t. Apparently Robin Marushia has been looking
> at B. t., and there are undoubtedly others. In my opinion, this species is a
> preeminent invader (not merely a ruderal species), and extreme environments
> like deserts may be more instructive places to work--especially if Bean
> wants to relocate and can find a "slot" someplace.
>
> Just a thought . . .
>
> WT
>
> ----- Original Message ----- From: "Carolyn Beans" <[email protected]>
> To: <[email protected]>
> Sent: Wednesday, April 07, 2010 7:39 AM
> Subject: [ECOLOG-L] invasive and native plant competitors
>
>
> Hello All,
>>
>> I'm a first year graduate student and I'm planning to study the
>> evolutionary response of native plant
>> populations to an invasive plant competitor. Right now I'm at the stage of
>> trying to figure out exactly
>> which invasive and native plants to work with. I'm wondering if anyone has
>> noticed any invasive
>> plants that seem to be especially strong competitors with a specific
>> native plant species? I would also
>> be interested in instances where an invasive plant appears to be
>> facilitating a native plant species.
>>
>> I'll most likely be doing my field work in Virginia at Mountain Lake
>> Biological Station, but I could
>> potentially go anywhere.
>>
>> thanks for your help!
>> Carolyn
>>
>
>
>
> --------------------------------------------------------------------------------
>
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 8.5.437 / Virus Database: 271.1.1/2796 - Release Date: 04/07/10
> 06:32:00
>
