‘geographic distribution modelling’ loosely based on ‘niche theory’

So this is my very mini- rant regarding the not so recent publication-volley between Warren (2012), and McInerny and Etienne (2013) with a reply to the reply in Warren (2013).

Apart from the decade long niche-modelling vs. species distribution modelling terminology war. What made me really nervous is the fact that authors deliberately misquote or somehow misunderstand something written in plain text so that it is easy to pick on an idea. I won’t say much except providing you the excerpts from these publications, you can then judge for yourselves.

So… excerpt from Warren (2012) goes as follows ….” [I] am not arguing that the term ‘distribution model’ be deprecated, or that anybody should necessarily switch from terminology that they are comfortable with; rather, I am demonstrating that the niche assumption is frequently necessary when constructing and applying these models, and that assumption cannot be avoided by simply avoiding the term. Therefore, this is not simply an argument about terminology. It is an argument, or at the very least a reminder, about the assumptions implicit in the construction and use of these models.”

The reply from McInerny and Etienne (2013) starts with…..” [R]ecently, Warren [1] argued that correlative modelling of species distribution and environmental data should be described as Ecological Niche Modelling (ENM) rather than Species Distribution Modelling (SDM).”

Did anyone notice the word “should” in their excerpt? If this is not inflammatory I don’t know what is. So anyone by now can easily see the strategy used to pick a fight, the earlier excerpt clearly shows that the author’s notion of not at all endorsing one or the other term, rather he was worried that just banishing the term “niche modelling” will not make the species distribution practice “better”. Extracting information on the species niche from presence records albeit partial, is the whole basis on which correlative models are constructed. Unless we completely ditch the idea of extracting possible combination of values of environmental variables that we assume limit the species and project them either spatially or temporally, we cannot deny the fact that the mechanism of the correlative species distribution modelling is related with niche theory. I read McInerny and Etienne’s (2012) “Ditch the niche-…” paper hoping there will be a suggestion regarding what other theory apart from niche theory can be used to predict species distributions; unfortunately, their article was still focused on ‘tautology’, ‘conceptual grammar’ and ‘wording’. So we are stuck with niche theory… So if I were Warren (2013) my ideal title reply for their [‘niche’ or ‘distribution’ modelling?] would have been [‘geographic distribution modelling’ loosely based on ‘niche theory’]… But I guess [‘Niche modelling’: that uncomfortable sensation means it’s working] works well too :).

Now how successful we are in estimating or understanding species niche from crude climatic variables is a different question. It also makes sense to define what sort of niche we are talking about. The climatic niche of a species is likely to be much broader than the idea of niche with which most ecologists are comfortable. I mean the niche which is actually defined by functional roles of the species within a food web, its physical attributes as well as environmentally suitability for the species. As beautifully defined by Odum (1971) when he effortlessly combined Grinnell’s and Elton’s view of species niche.

“… the ecological niche of an organism depends not only on where it lives but also on what it does(how it transforms energy, behaves, responds to and modifies its physical and biotic environment), and how it is constrained by other species. By analogy, it may be said that the habitat is the organism’s ‘address,’ and the niche is its ‘profession,’ biologically speaking. “

McInerny and Etienne’s (2012) gave a very good review of how the term ‘niche’ was defined according to various sources. I suggest reading their paper to have a quick overview of how differently the term ‘niche’ conceived by different people with different backgrounds.

End of rant…

To be fair, I understood where McInerny & Etienne (2013) were coming from, It is just that their argument started by misstating Warren (2012). My point is, isn’t it easier to stick to what the authors wrote instead of reading between the lines? Sometimes when texts in journal articles are not clear, we may be forced to read between the lines and work out what they meant. However, when the message is very clear as the excerpt I’ve put in the beginning from Warren (2012), going with what we thought the authors meant instead of what they clearly stated, just makes the discussion on the subject very repetitive and obscures the real issue to be tackled.

But really you might think why I did not write a reply… well apart from the fact that it is a year old, I personally believe that Warren (2012) has already eloquently put it. I believe that what we need is not a term change rather a better definition of what we mean by “niche” when we use it in the context of species distribution modelling. If one uses only climatic variables then what we assume is that we are estimating even if somewhat partial (as we don’t have all the locations of where the species is present on earth) – a climatic niche. Now whoever is using the species distribution prediction that was found as a product of partial climatic niche projection on to the geographic space (giving us species distribution) can further look into geographic barriers, biotic interactions as well as possible non-analogue climate extrapolations to narrow down the potential distribution into a possible realised geographic distribution. Or alternatively one can use variables that are assumed to limit a species distribution better than mere climatic variables.

There is of course the issue of scale when it comes to using environmental variables that have high variation over distance. For example, plant species that need shade to grow…. you cannot possibly model shade at a global scale … I should know I tried and it was an epic fail :). Part of the problem being that correlation structures of such highly dynamic variables that are affected by different factors in different parts of the world cannot effectively be used to estimate global distribution….especially not using linear models anyway. But you can hone your climatic global potential distribution even further by looking at variables that make sense to the species at a local level for high resolution predictions. If we make our predictions two-step and find climate limited distributions and later narrow that down using biologically meaningful variables at a small scale area it would make grasping the problem we face with how we use niche in species distribution modelling easier.

After all… living things are clearly limited by climate when you look at their distribution at a global scale. To my knowledge (which is not much) it is only H. Sapiens and associated species that managed to defy climatic boundaries and managed to equate their realized distribution to their potential geographic distribution and beyond by engineering unsuitable habitats into suitable habitats. That is because H. Sapiens can actively change their environment by altering its nature…For example simply having cooling fans in hot areas and heaters in cold areas, a luxury not shared by many of our fellow species. (Of course – not forgetting some ubiquitous micro-organisms that could quickly adapt to new situations due to the extremely high number of generations they have over a given time allowing for a quicker natural selection that favours better adapted individuals).

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[ECOLOG-L] Postdoctoral Researcher for the NE Climate Science Center at UMass

Via Toni Lyn Morelli  from MyEcologForward google group


The Northeast Climate Science Center (NE CSC) along with the Department of
Civil and Environmental Engineering at the University of Massachusetts
Amherst is seeking a Postdoctoral Research Associate (Climate Impacts
Expert). The selected researcher will join an active group of faculty,
postdoctoral researchers, and graduate students engaged in research projects
funded by the Department of Interior, NOAA, and the U.S. Fish and Wildlife

Job duties include: data analysis and computer programming; statistical
analysis of climate data and climate model simulations; development of
project research goals through innovative ideas and approaches; preparation
of research papers and reports; presentation of occasional lectures and
seminars; and participation in research group meetings.

Further information about the NE CSC can be found at https://necsc.umass.edu

The successful candidate will be supervised by Dr. Toni Lyn Morelli, Program
Manager of the Northeast Climate Science Center and Adjunct Assistant
Professor of the Department of Environmental Conservation.

The candidate must hold a Ph.D. in an area of natural sciences, engineering,
or other relevant discipline with specialization in climate modeling and
expertise in at least two of the following areas: coastal resilience,
climate modeling, structured decision-making, and the ecological impacts of
climate change. The position will require skills in programming and data
management, knowledge of statistical methods, the ability to write
scientific papers and project reports, and the ability to travel and give
scientific presentations at regional meetings. Previous experience with
stakeholder-driven research is strongly desired.

Starting salary is expected to be $48,000 but will be commensurate with
qualifications and experience. The position will initially be for one year
and may be extended for up to two years, dependent upon satisfactory
performance and availability of funding.

If interested, please apply online at
http://umass.interviewexchange.com/jobofferdetails.jsp?JOBID=49594 and
submit a CV, cover letter describing research experience and interests, and
the names and emails of three references. Review of applications will begin
on June 13, 2014, and continue until the position is filled. The
anticipated start date is August 1, 2014. Please send direct inquiries to
Toni Lyn Morelli by email mor…@umass.edu.

The Department of Civil and Environmental Engineering is committed in its
efforts to hire candidates who will enhance the diversity and gender balance
its faculty, staff and students. The University of Massachusetts is an
Affirmative Action/Equal Opportunity Employer of women, minorities,
protected veterans, and individuals with disabilities and encourages
applications from these and other protected group members.