Why do you think your paper is highly cited?

  Does it describe a new discovery or new methodology that's useful to others?

It is arguable that by 1869 Alfred Russel Wallace had already proposed all major climatic, historical, and ecological explanations for the major geographic patterns of species richness. If so, then the mid-domain effect was the first new hypothesis in this arena in nearly 130 years. So it is certainly new, but its usefulness as an explanation for species richness patterns is an empirical question that awaits consensus solutions to the challenge of designing unambiguous tests of the hypothesis.

  Is it a condensation of previous literature on the subject?

We reviewed the literature on the mid-domain effect and related historical precedents in the context of a unifying mathematical and geometric framework that was original with our paper.

  Could you summarize the significance of your paper in layman's terms?

Biologists have long believed that geographical differences in the number of species of any particular group of plants or animals are ultimately caused by climatic differences-such as differences in the amount of rainfall or average temperature-and historical events such as glaciation. In the absence of geographic variation in such factors, it was implicitly assumed that the number of species of a group of plants or animals would be the same in all places suitable for that group. It now appears that this assumption is wrong. If the geographic ranges for a group of species are placed at random within the area they jointly occupy, without regard to climate or history, more species will be found near the center of that area than near the edges-a pattern we called the "mid-domain effect." While no one doubts the importance of climate and history, tests are now underway to see how much the mid-domain effect contributes to real-world  patterns of biodiversity.

  If you would like to add any other comments, please feel free to do so. 

Like all other patterns in ecology, geographic patterns of species richness doubtless have multiple, interacting causes. Much effort (and ink) has been wasted in past controversies by those who, themselves, champion single causes of complex ecological patterns, or falsely claim that others do so, arguing that if a proposed hypothesis cannot explain all, then it explains nothing. The mid-domain effect should be viewed as contributory to geographical patterns of species richness, its effect to be assessed within the context of competing hypotheses, none of which is exclusive.

Robert K. Colwell, 
Board of Trustees Distinguished Professor
Dept. of Ecology & Evolutionary Biology, U-43
University of Connecticut, 
Storrs, CT 06269-3042, USA