[APWG] Positive interactions between native and non-native species

[Wayne Tyson]

Dear Zelianne:

I refer you to a recent discussion on this list with the subject line: 
Plants  Alien  Uses

Having worked for several decades in "ecosystem restoration," I have made 
several observations with respect to your line of enquiry, but have not 
published specifically on this subject. I do, however, think that your 
research could be a significant contribution to the literature. Here is a 
summary of my offhand observations/thoughts on the subject, for what they 
may be worth:

1. What I am arrogantly calling "Tyson's Law" says that "Organisms do what 
they can, when they can, where they can."

2. What I call the Goldilocks Hypothesis: Organisms have ranges of both 
(genetic) requirements and tolerances that we might call "habitat 
requirements and limitations." (For example, temperature, radiation, 
salinity, pH, nutrients, toxins, water, oxygen, carbon dioxide, etc., etc.)

3. Organisms tend to thrive best when the match between habitat requirements 
and habitat characteristics are optimal for any given organism.

4. Organisms tend to be limited as the habitat fails to be characterized by 
an optimal match between it requirements and any given habitat.

5. The two preceding features of organisms and habitat/environment are 
largely, if not entirely, responsible for the diversity of organisms in any 
given place at any given time.

6. All of the preceding change, become different at different rates for 
different reasons (e.g., "seasons," epochs, eras, "time of day," etc.); that 
is, they are dynamic, not static.

7. Most humans have difficulty conceiving of change, and are "more 
comfortable" with static concepts or those changes which are readily 
observed, limited, or otherwise convenient.

8. Most organisms have the capacity to adaptively change to some extent, and 
as changes in habitat characteristics occur, those organisms having larger 
capacities to change (adaptive potential) are likely to be the ones which, 
in a changed state, survive and reproduce most.

9. Organisms themselves become "change agents" affecting habitat 
characteristics and other organisms.

10. The number of variables acting and interacting over time is exceedingly 
difficult to "model," and the complexity of ecosystems may be too great to 
fully explain or predict consequences of changes. While changes in 
temperature, for example can be a powerful influence upon organisms, genetic 
variation within species may cause a shift in ecotypes that results in 
adaptation rather than shifts in populations or distributions, but those 
also may occur. No model at all might be better than one that lacks 
demonstrated ability to predict change outside of the laboratory, but may 
have utility when combined with other analytical techniques within the scope 
of its actual relevance. Creating a database of the adaptive range of 
organisms and the range of it requirements and tolerances might be a simple 
way to accumulate data that can have real predictive value without as many 
bells and whistles that seem to characterize some models.

11.  It is likely to be a long time before computer models have the 
capability to predict more than the assumptions built into them, and 
probably longer before they become the "savior" of Earth ecosystems.

12. "Colonizing" species are merely those which have moved or been moved to 
a habitat for which they are sufficiently well suited to a given habitat, 
conditions which sufficiently match (or "fall within") their range of 
requirements and tolerances.

13. "Alien" species are those which did not evolve within a particular 
ecosystem subset.

14. Indigenous species can colonize changed habitats; this is a major 
element of ecosystem resilience. For example, indigenous "weeds" that 
colonize disturbed habitats and occupy (and change) them until changed 
conditions are again unfavorable to them, mirror the ecological processes 
that make "alien invasions" possible.

15. We might ponder whether or not "invasions" are more cultural artifact 
than natural process, but certainly natural, non-cultural processes are 
involved.


These are all points which could be pursued at greater length and improved, 
and certainly the list is not complete. Yeates and others can, I am certain, 
add to them, shed further light upon their content, and organize them 
better. I only hope that they will be useful to Yeates and to others in the 
pursuit of better understanding of how Nature works, how it affects human 
cultural activities, and how they affect the Earth and its life.

As Yeates and others reveal more about their thinking and debate the merits 
and defects stated here in future discussions, the science of ecology and 
the practices of ecosystem management and mismanagement might become a bit 
more understandable and "accurate." The relevant sciences and current 
practices in this "field" can then change, one hopes, for the better.

I will appreciate criticisms.

WT


----- Original Message ----- 
From: "Z. Yeates" <z.yeates at btinternet.com>
To: <apwg at lists.plantconservation.org>
Sent: Wednesday, May 25, 2011 8:25 AM
Subject: [APWG] Positive interactions between native and non-native species


> Hello List Subscribers
> I am a postgraduate researcher at the University of Gloucestershire, 
> researching positive interactions between native and non-native species.
> I would be grateful for any information relating to research that has 
> detected a positive association between native species/native biodiversity 
> and the presence of a non-native species.
> I am looking for both published (peer-reviewed) research and unpublished 
> research - significant or non-significant results.
>
> Although I am interested in all research that has detected a positive 
> association between native species/native biodiversity and the presence of 
> a non-native species.
> My interest in this subject stems from the fact that most research into 
> the impacts of established non-native species has understandably focused 
> on the negative effects of invasive species.
> The positive effects that some non-native species have on other non-native 
> species are also relatively well reported.
> However, my primary objective, as it stands, is to identify and retrieve 
> all (or as many as I can) studies that have uncovered situations where a 
> non-native species has (potentially) had a positive (or partially 
> positive) effect on a native
> species/native biodiversity (e.g. increases in abundance, density, growth, 
> survival, fecundity and ideally, fitness).
>
> Thank you and regards
> Zelianne
>
> -- 
> Zelianne Yeates
> Postgraduate Researcher
> Positive Interactions between Non-Native and Native Species
> Department Natural Sciences
> University of Gloucestershire
> Francis Close Hall
> Swindon Road
> Cheltenham
> GL50 4AZ
>
>
>
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