Data from: Integrating fuzzy logic and statistics to improve reliabile definition of biogeographic regions and transition zones

The present study uses the amphibian species of the Mediterranean Region
to develop a consistent procedure based on fuzzy sets with which
biogeographic regions and biotic transition zones can be objectively
detected and reliably mapped. Biogeographical regionalizations are
abstractions of the geographical organization of life on Earth that
provide frameworks for cataloguing species and ecosystems, for answering
basic questions in biogeography, evolutionary biology and systematics, and
for assessing priorities for conservation. On the other hand, limits
between regions may form sharply defined boundaries along some parts of
their borders, whereas elsewhere they may consist of broad transition
zones. The fuzzy set approach provided a heuristic way to analyze the
complexity of the biota within an area; significantly different regions
were detected whose mutual limits were sometimes fuzzy, sometimes clearly
crisp. Most of the regionalizations described in the literature for the
Mediterranean Region present a certain degree of convergence when they are
compared within the context of fuzzy interpretation, as many of the
differences found between regionalizations are located in transition
zones, according to our case study. Compared to other classification
procedures based on fuzzy sets, the novelty of our method is that both
fuzzy logic and statistics are used together in a synergy in order to
avoid arbitrary decisions in the definition of biogeographic regions and
transition zones.