Biology Reference
In-Depth Information
CHAPTER
10
Ecological and Evolutionary
Morphology
In this chapter we discuss methods and approaches for studying evolutionary trans-
formations of shape. This topic covers a wide variety of studies, so we focus on a few
commonly investigated areas of interest: correlations between size and shape (evolutionary
allometry), correlations between form and function (functional morphology, ecomorpho-
logy), comparisons of evolutionary trends (studies of parallelism and convergence), and
quantitative descriptions of the morphospace occupation (evolution of morphological
diversity). For each area, we examine the typical research questions and the principal
methods of answering those questions.
Many of the studies of shape evolution have focused on identifying the factors that deter-
mine its direction. One question might be: Is there a correlation between size and shape?
Another might ask: Do species that differ in diet also differ in shape and is that difference
related to the strength or the speed of their bite? Having found such a relationship, the next
step might be to ask if other lineages exhibit a similar trend, or what conditions would cause
a change in the direction of that trend. Answers to these questions might lead to new
questions about the generation of morphological diversity: for example, are some habits or
habitats more conducive than others to increasing morphological diversity?
The vast majority of studies on evolution of shape involve comparing morphologies
of multiple species, sometimes several dozen species. Many of these interspecific comparisons
can be performed using the same analytic methods as would be applied to intraspecific compar-
isons of individuals (e.g. regressing size on shape or performing ANOVA to test for differences
of means among diet classes). However, to perform these analyses correctly for interspecific
comparisons, it is necessary to include the phylogenetic relationships of the taxa. Therefore, we
begin this chapter with a discussion of the role of phylogeny in comparative studies.
INCOR PORATING PHYLOGENY IN COMPARATIVE ST UDIES
The problem phylogenetic relationships present for statistical inference have been
discussed at length in numerous publications ( Cheverud et al., 1985; Felsenstein, 1985;
 
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