| Welcome to the lab pages of Brian McGill. |
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I am interested in problems in large scale ecology or macroecology. These problems have a large scope in one or more of the scaling dimensions: time, space, taxon. Most of my recent work has focused on either large spatial scales or large taxonomic scales. One example is exploring the causes and implications of patterns in the geographic ranges of species. Another example is exploring traditional community ecology questions such as the causes of the species abundance distribution and whether the neutral theory provides an adequate explanation. I also have interests in macroevolution/paleoecology and in evolutionary ecology. Large scale ecology is experiencing a burst of new research enabled by new technology involving large amounts of data and computer techniques for analyzing the data. This technology is collectively called "ecoinformatics" and is the central tool in much of my research.
The abundance of a species across its range has been characterized as being normal or Gaussian in shape. While this is a gross simplification, there is some real structure to abundances across a range, which I refer to as "peak-and-tail" structure. It turns out this structure combined with two other very general hypothesis can explain many well-known macroecological patterns, including the species abundance distribution (SAD) and the species area relation (SPAR). This work is done in collaboration with Cathy Collins. For more details click here or to download the paper Evolutionary Ecology Research 2003 vol 5(4):469-492
Given the implications of the structure of abundance across a range described above, one naturally wants to know why this structure occurs. This has been little studied to date. I propose two hypothesis:
I implement models of these two mechanisms and show that they both produce Gaussian shaped abundances across a range
A species abundance distribution is a histogram of the # of species in different abundance classes (1 individual observed, 2 individuals observed, etc). It is one of the most basic descriptions of the structure of a community imaginable. It is also one of ecology's truly universal laws. There are ALWAYS lots of rare species and a few hypercommon species (and some in the middle). Why is this? We don't know despite having studied this problem since the 1920's.
Given that controlled, replicated experiments are very difficult and costly at the scale of macroecological questions, theory plays a very important role in macroecology. In particular the search for mechanisms depends heavily on theory.
This means that we need to be very careful about how we macroecologists test theories. In particular, I argue that fitting a curve with free parameters is a very weak test. The shape of the curve is usually predicted by the Central Limit Theorem or a similar statistical argument. I propose that there are three things which are not predicted by the central limit theorem and suggest that these make much stronger tests of macroecological theories. Oikos 2003 vol 102(3):679-685
Applying the above argument, I examine whether the neutral theory works better than the null hypothesis of a lognormal distribution of species abundances. In fact it does not. The lognormal distribution outperforms the Zero Sum Multinomial distribution on all measures. For more details, click here or download Nature 422(24 April):881-885
My work on species ranges has led me to an interest in an old but poorly understand question: what converts the fundamental niche into the realized niche? By definition it is competition (or perhaps more generally all biotic interactions). Yet we know next to nothing about how this process works.
I am very interested in this rapidly growing methodology and how it can be applied to questions of coevolution. Especially to questions of diffuse coevolution with many species interacting with each other simultaneously.
The theory of predation and competition has been extensively developed.
This is not true of mutualisms. I am interested in working on
the evolution and population dynamic theory of mutualisms and
other positive species interactions such as commensalism.