Geography Reference
In-Depth Information
An alternative conceptualization (Haydon et al. 1994) highlights the com-
plementary roles of ecology, history, and chance (
fig. 2.3
). In this model, a
balanced biogeography results from the interaction of ecological, historical,
and stochastic processes.
Biogeographic patterns are nonrandom, repetitive arrangements or distribu-
tions of organisms and clades in geographic space. The study of certain
specific patterns constitutes the scope of particular biogeographic ap-
proaches; for example, specific richness patterns and distribution of life
formsarestudiedinecologicalbiogeography,chorologicalpatternsarestud-
ied in areography, structural and functional patterns of ecological systems
are studied in macroecology, and biogeographic homology patterns are
studied in evolutionary biogeography (Espinosa Organista et al. 2002).
Biogeographic homology is the basic concept of evolutionary biogeo-
graphy (Morrone 2004a). In its more general form,
homology
means equi-
valenceofpartsandconstitutesasortingprocedureusedtoestablishmean-
ingful comparisons within a hierarchical system (de Pinna 1991; Nelson
1994; Rieppel 2004; Williams 2004). Biogeographic homology allows one to
identify biotic components, namely, the sets of spatiotemporally integrated
taxa that coexist in given areas. If the analogy between systematics and
biogeography is accepted, we may consider that the distributions of indi-
vidual taxa are the statements about biogeographic homology that are be-
ing compared. Homology is the relationship between the homologues (in
biogeography, the biotic components) rather than the homologues them-
selves (Nelson 1994; Rieppel 1991; Williams 2004).
Several authors have recognized two stages in the proposition of ho-
mologies, which have been named primary and secondary homology by de
Pinna (1991). Primary homology, which corresponds to the stage of gen-
eration of the hypotheses, represents a conjecture on the correspondence
between parts of different organisms. Secondary homology, which corres-
ponds to the stage of legitimation of the hypotheses, represents a test of
such conjecture by congruence with similar statements in the cladogram.
In biogeography, both stages have been implicitly recognized by several
authors (Donoghue et al. 2001; Hausdorf and Hennig 2003; Morrone and
Crisci 1990, 1995; Riddle and Hafner 2006).
