Geography Reference
In-Depth Information
• An area of endemism can be defined by the congruent distributional
limits of two or more species (Platnick 1991:xi).
• Geographic region comprising the distributions of two or more mono-
phyletic taxa that exhibit a phylogenetic and distributional congruence
and have their respective relatives occurring in other such defined re-
gions (Harold and Mooi 1994:262).
• Areas of nonrandom distributional congruence between different taxa
(Morrone 1994b:438).
• Areas defined by the distributions of endemic taxa occurring in those
areas (Humphries and Parenti 1999:6).
• Areas delimited by the congruent distribution of at least two species of
restricted range (Linder 2001:893).
• Areas delimited by barriers, the appearance of which entails the form-
ation of species restricted by these barriers (Hausdorf 2002:648).
• Areas that have many different groups found there and nowhere else
(Szumik et al. 2002:806).
Some of these definitions entail extensive sympatry (Platnick 1991), al-
though this congruence does not demand complete agreement on those
limits at all possible scales of mapping (Hausdorf 2002; Linder 2001; Mor-
rone 1994b; Morrone and Crisci 1995; Wiley 1981). Some definitions derive
explicitly from a vicariance model (Harold and Mooi 1994; Hausdorf 2002),
whereas others are neutral (Morrone 1994b; Szumik et al. 2002). Some
refer to species (Hausdorf 2002; Linder 2001; Platnick 1991) and others to
taxa (Harold and Mooi 1994; Humphries and Parenti 1999; Morrone 1994b).
How do we recognize an area of endemism? Müller (1973) suggested
a protocol for working out “dispersal centers,” which has been applied to
identify areas of endemism (Morrone 1994b; Morrone et al. 1994). It con-
sists basically of plotting the ranges of species on a map and finding the
areas of congruence between several species. This approach assumes that
the species' ranges are small compared with the region itself, that the limits
of the ranges are known with certainty, and that the validity of the species is
not in dispute. According to Linder (2001), areas of endemism should meet
four criteria: They must have at least two endemic species; the ranges of
the species endemic to them should be maximally congruent; they should
be narrower than the whole study area, so that several areas are located;
and they should be mutually exclusive.
