Geography Reference
In-Depth Information
Biotic components are sets of spatiotemporally integrated taxa that coexist in
givenareas.Theirunityisduetotheircommonhistory,althoughtheymaynot
represent monophyletic entities because of reticulation due to geodispersal
and biogeographic convergence. Each biotic component usually consists of
a particular set of cenocrons that have been integrated at different times. If
taxa studied have a wide distribution in the fossil record or a molecular clock
can be calibrated, it would be possible to recognize these cenocrons accord-
ing to their geological age. The identification of biotic components, the basic
biogeographic units, is the first stage of an evolutionary biogeographic ana-
lysis. In this chapter I present the two basic approaches for studying biot-
ic components: panbiogeography and identification of areas of endemism. I
also introduce some basic methods and provide case studies.
There are two basic ways to represent biotic components: generalized tracks
and areas of endemism. The former are studied by panbiogeography, where-
as the latter are the units of cladistic biogeography. We may distinguish gen-
eralized tracks and areas of endemism by their scales (larger or smaller, re-
spectively), although they both represent biotic components (Morrone 2001c,
2004a). The aim of panbiogeography is to recognize generalized tracks,
whereas cladistic biogeography emphasizes the recognition of areas of
endemism and their relationships as fundamental issues (Morrone and Crisci
1995; Nelson and Platnick 1981; Szumik et al. 2002, 2006).
