Data from: Mainland size variation informs predictive models of exceptional insular body size change in rodents

The tendency for island populations of mammalian taxa to diverge in body
size from their mainland counterparts consistently in particular
directions is both impressive for its regularity and, especially among
rodents, troublesome for its exceptions. However, previous studies have
largely ignored mainland body size variation, treating size differences of
any magnitude as equally noteworthy. Here, we use distributions of
mainland population body sizes to identify island populations as
‘extremely’ big or small, and we compare traits of extreme populations and
their islands with those of island populations more typical in body size.
We find that although insular rodents vary in the directions of body size
change, ‘extreme’ populations tend towards gigantism. With classification
tree methods, we develop a predictive model, which points to resource
limitations as major drivers in the few cases of insular dwarfism. Highly
successful in classifying our dataset, our model also successfully
predicts change in untested cases.