Geography Reference
In-Depth Information
Figure 4.15
Assignment of scores under different criteria in endemicity analysis.
(a) Area with score 3 under the first criterion (contributed by the three species); (b)
area with score 2 under the second criterion (in addition to species “circle,” species
“square” contributes to the score); (c) area with score 2 under the third criterion (spe-
cies“triangle”doesnotcontributetothescorebecauseitisfoundonlyinsomecells);
(d) area with score 4 under the fourth criterion (the four species contribute to the
score, although none of them is found in all the cells).
Algorithm
It consists of the following steps (Szumik et al. 2002, 2006; Szu-
mik and Goloboff 2004; Szumik and Roig-Juñent 2005):
1. Plot species localities on a map with a grid.
2. Assign values of endemicity to all possible sets of grid cells, counting the
species that may be considered endemic to them according to the four cri-
teria defined by Szumik et al. (2002).
3. Choose the sets of grid cells with the highest endemicity scores.
4. Draw the sets of grid cells on a map as areas of endemism.
Software
NDM and VNDM (Goloboff 2004; Szumik et al. 2006).
Empirical Applications
Domínguezetal.(2006),MolineandLinder(2006),
Szumik and Roig-Juñent (2005).
Southern South America, basically the area south of 30° south parallel (Crisci et
al. 1991b), harbors a very interesting biota, with high endemicity and strong biotic
relationships with other austral continents. Szumik and Roig-Juñent (2005) ana-
lyzed data from 191 species of Carabidae (Coleoptera), distributed in 208 1° × 1°
grid cells with software NDM (Goloboff 2004).
Fifty-three (28%) species were present in a single grid cell. A first analysis of
endemicity was undertaken in order to determine whether these species were de-
fining single grid cell areas of endemism or were the result of insufficient data or
artifacts due to small grid cells. Four small areas of endemism were found, one of
them corresponding to the Juan Fernandez Islands. The second analysis of en-
demicity was conducted adding or deleting two grid cells each time and defining
areas of endemism by four or more endemic species, with an endemicity value
corresponding to two species with perfect sympatry. Fifteen sets of grid cells were
found, but some of these sets were nested within others or differed in a single grid
