Geography Reference
In-Depth Information
Dispersal explanations traditionally have rested on narrative frameworks,
lacking a general theory to explain distributional patterns, so they have been
rejected by panbiogeographers and cladistic biogeographers as ad hoc ex-
planations. After establishing biogeographic homology patterns, however,
dispersal explanations can help establish when the cenocrons assembled in
the identified components, incorporating a time perspective in the study of
biotic evolution. In this chapter I explore how time slicing, intraspecific phylo-
geography, and molecular clocks may be used to incorporate temporal in-
formation in the biotic components recognized previously, helping identify the
cenocrons that they comprise and how they dispersed and integrated.
Hunn and Upchurch (2001) emphasized the relevance of time in evolutionary
biogeography because data on temporal distribution may provide important
constraints in biogeographic analyses, helping reinforce or overturn specific
hypotheses. The incorporation of temporal information entails assigning time
values to cladogenetic events (Crisci et al. 2000). Lieberman (2004) high-
lighted the relevance of the deep time perspective in biogeography, based on
three arguments: The fossil record is the only primary and direct chronicle of
the history of life, the phenomenon of extinction can influence our ability to
retrieve biogeographic patterns, and the fossil record may provide examples
of dispersal events.
Upchurch and Hunn (2002) stated that the extent to which temporal data
are incorporated into biogeography depends on the researcher's choice of
sources of spatial data and analytical methods. It has been suggested that
the temporal ranges of organisms are important because distribution patterns
