Parsimony analysis of endemicity (PAE) of Mexican terrestrial mammals at different area units: when size matters
Juan J. Morrone* and T. Escalante Museo de Zoologı´a, Departamento de Biologı´a Evolutiva, Facultad, de Ciencias, UNAM, Mexico D.F., Mexico
Aim Parsimony analysis of endemicity (PAE) is a biogeographical method that uses aparsimony algorithm to obtain an area cladogram, based on taxa inhabiting the study areas. We compare its performance at different geographical units (1/2° and 1° quadrats, ecoregions and biogeographical provinces) to analyse distributional patterns of Mexican terrestrial mammals, in order to assess the importance of the size of area units. Location The area analysed corresponds to Mexico. MethodsParsimony analyses were based on 56,859 collection records, corresponding to 703 genera, species and subspecies. Four data matrices were constructed for: (1) 716 quadrats of 1/2° latitude · 1/2° longitude, (2) 230 quadrats of 1° latitude · 1° longitude, (3) forty-ﬁve ecoregions and (4) fourteen biogeographical provinces. Results For the 1/2° quadrat matrix, we obtained six cladograms of 17,138 steps.For the 1° quadrat matrix, we obtained ﬁve cladograms (strict consensus with 9394 steps). For the matrix of ecoregions, we obtained twelve cladograms (strict consensus cladogram with 3009 steps). For the provinces, we obtained a single cladogram with 1603 steps. Main conclusions The best results were obtained with natural areas instead of quadrats. There seems to exist a trend to decrease theabsolute number of steps and an increase in the absolute and relative number of synapomorphies as the size of the area units decreases, although this does not necessarily occur for the number of cladograms. Keywords Endemicity, distributions, biogeography, parsimony, parsimony analysis of endemicity, mammals, Mexico.
INTRODUCTION Parsimony analysis of endemicity (PAE) – also named parsimony analysisof distributions (PAD) (Trejo-Torres & Ackerman, 2001) – uses a parsimony algorithm in order to obtain an area cladogram, based on the taxa inhabiting the areas (Rosen, 1988; Rosen & Smith, 1988; Morrone & Crisci, 1995). Although it was originally aimed at ﬁnding areas of congruent distributional patterns, authors began to use it increasingly to assess biotic similarities between areas. PAE hasbeen applied by several authors to establish
*Correspondence: Museo de Zoologia, Departamento de Biologia Evolutiva, Facultad de Ciencias, UNAM, Apdo. postal 70-399, 04510 Mexico D.F., Mexico. E-mail: email@example.com
relationships among different biogeographical units, e.g. localities, quadrats, areas of endemism, continents, islands, etc. (Craw, 1989; Cracraft, 1991; Myers, 1991;Morrone, 1994a,b, 1998; Fernandes et al., 1995; Morrone & Lopretto, 1995; Da Silva & Oren, 1996; Morrone & del Coscaron, ´ 1996; Posadas, 1996; Bellan & Bellan-Santini, 1997; Morrone et al., 1997, 1999; Posadas et al., 1997; Geraads, 1998; Sfenthourakis & Giokas, 1998; Watanabe, 1998; ´ Glasby & Alvarez, 1999; Luna-Vega et al., 1999, 2000; Espinosa-Organista et al., 2000; Ron, 2000; Bisconti et al.,2001; Ippi & Flores, 2001; Morrone & Marquez, 2001; ´ Trejo-Torres & Ackerman, 2001; Garcıa-Barros et al., ´ 2002). Results of applying PAE have been interpreted in different ways. Many authors assume the existence of a common historical explanation for the assemblages of areas based on
Ó 2002 Blackwell Science Ltd
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shared species and supraspeciﬁc taxa(Rosen, 1988; Myers, 1991; Morrone, 1994b, 1998; Posadas et al., 1997; Luna et al., 1999). Cracraft (1991) speculated whether ecological similarity could also contribute to the patterns detected by PAE. Trejo-Torres & Ackerman (2001) considered that patterns discovered by PAE could have a Ôstatic or non-historical interpretationÕ. Humphries & Parenti (1999) anathematized PAE, declaring that it...