Definition
The panbiogeographic approach, originally proposed by Léon Croizat (1958),
basically plots distributions of a particular taxon or group of taxa on maps
and connects the disjunct distribution areas or collection localities together
with lines called tracks. A track is a representation of the
spatial form of a species distribution and can give insights into the spatial
processes that generated that distribution. Crossing of an ocean or sea basin
or any other major tectonic structure (eg. a fault zone) by an individual track
constitutes a baseline. Individual tracks are superimposed, and
if they coincide according to a specified criterion (eg. shared baselines or
compatible track geometries), the resulting summary lines are considered
generalized (or standard) tracks. Generalized tracks suggest the
pre-existence of ancestral biotas, which subsequently become fragmented by tectonic
and/or climate change. The area where two or more generalized tracks intersect
is called node. It means that different ancestral biotic and
geological fragments interrelate in space/time, as a consequence of terrain
collision, docking, or suturing, thus constituting a composite area. A
concentration of numerical, genetical or morphological diversity within a taxon
in a given area constitutes a main massing
Over the last two decades, Panbiogeography as first conceived by Croizat
(1958, 1964, 1976) and further developed by researchers in New Zealand and Latin
America (Craw et al., 1999; Morrone, 2004) became established as a productive
research programme (Craw & Weston, 1984) in historical biogeography. Panbiogeography
provides a method for analyzing the geographic (spatial) structure of
distributions in order to generate predictions about the evolution of species
and other taxa in space and time.
Panbiogeographic key concepts of track, node, baseline, and main massing have
shown to be powerful analytical tools, especially following the mathematical
formalization of these concepts with the development of quantitative
panbiogeography (Page, 1987; Craw, 1988, 1989; Henderson, 1989). Such
developments were based on the application of concepts and methods from graph
theory, for example minimum spanning trees to depict individual tracks in a
more rigorous way, clique analysis to identify standard tracks, and nodal
analysis to determine the precise location of panbiogeographic nodes.
Panbiogeography emphasizes the analysis of raw locality and broader
distribution data for taxa and may thus benefit from modern technological
advances for the collection, storage, and analysis of such data as online biodiversity
databases of georeferenced records (FishNet,
HerpNet, MaNIS,
OBIS, ORNIS),
the Global Positioning System (GPS) and Geographic Information Systems (GIS) technology.
Furthermore, besides its academic interest and scientific relevance as a method
for the analysis of earth/life historical relationships, panbiogeographic
concepts may also be useful to address the critical issue of global
biodiversity conservation in a potentially fast and cost-effective way (Grehan,
1989, 1993, 2000; Morrone & Crisci, 1992; Alvarez-Mondragón & Morrone, 2004;
Prevedello & Carvalho, 2006; Torres-Miranda & Luna-Vega, 2006).
|