2009 Zoological Society of Japan ZOOLOGICAL SCIENCE 26: 623–631 (2009) Mitochondrial DNA Variation Reveals Recent Evolutionary History of Main Boa constrictor Clades Ivana Hynková, Zuzana Starostová and Daniel Frynta * Department of Zoology, Faculty of Science, Charles University, Vini ˇ cná 7, CZ-128 44 Praha 2, Czech Republic We sequenced a 1114-bp fragment of cytochrome b gene in six subspecies (115 samples) of Boa constrictor and detected 67 haplotypes. Our analyses revealed the presence of two distinct clades, one from Central America (CA) including the neighboring part of South America west of the Andes, and the other covering the rest of South America (SA). Sequence divergence between CA and SA clades is about 5–7%, which roughly corresponds to a separation at the time of uplift of the Colom- bian Andes following formation of the Panama Isthmus before 3.5 Myr Sequence divergence within the SA and CA clades is only 2–3%, suggesting a fairly recent spread of these clades into their cur- rent geographic ranges. Thus, we may not be dealing with taxa with a markedly old evolutionary history. Because juveniles of B. constrictor feed mostly on small rodents, we hypothesized that spread of this species was allowed by a new food source represented by muroid rodents that appeared after closure of the Panama portal. With respect to the taxonomy, B. c. imperator may be elevated to full species rank. Within the SA clade, a haplotype of Argentinian B. c. occidentalis is markedly distinct, while the remaining haplotype groups analyzed are distributed throughout large ranges and may all belong to a single nominotypic subspecies. Key words: boid snakes, CITES, conservation, genetics, Neotropics, Panama land bridge, phylogeny, phylogeography INTRODUCTION Boa constrictor Linnaeus, 1758 is a large boid species and one of the most famous snakes. Its extensive range covers most of Central and South America from northern Mexico to central Argentina (Walls, 1998) (see Fig. 1 for a map). As this species is distributed in both Central and South America, we assume that it participated in the spec- tacular “Great American Biotic Interchange” between these subcontinents following closure of the Panama Isthmus a few million years ago (Webb, 1991). Thus, it may serve as a model for understanding this process. Although Boa constrictor is generally considered to be polytypic (Price and Russo, 1991; Henderson and Hedges, 1995; Bonny, 2007), its subspecies have been defined solely on external morphology and coloration. Molecular characters have been explored in this species only recently (Campbell, 1997; Rivera et al., 2005), and thus the phylo- genetic relationships among Boa constrictor subspecies remain largely unsolved. Seven continental subspecies are currently recognized (Uetz et al., 2006). Boa constrictor imperator Daudin, 1803 is the Central American subspecies. It ranges from northern- most part of Mexico in Sonora and Tamaulipas to south- eastern South America and west of the Andes as far as the Ecuadorian Pacific coast (e.g., Boback, 2005; Quick et al., 2001). The nominotypic subspecies B. c. constrictor has the largest geographic distribution, covering most of tropical South America east of the Andes. The southernmost sub- species, B. c. occidentalis Philippi, 1873, is distributed in southern Paraguay and in Argentina between the Andes and the river Paraná as far as about 35 degrees south (Chiaroviglio et al., 2003; Rivera et al., 2005; Boback, 2005). Boa constrictor amarali Stull, 1932 reaches eastern Bolivia across the provinces of Mato Grosso and Goiás to the Brazilian province of Sao Paulo and also to southern Para- guay. The remaining three continental subspecies are restricted to the small areas in northern Peru and Ecuador: B. c. longicauda Price and Russo, 1991 to the Peruvian province of Tumbes on the Pacific coast; B. c. ortonii Cope, 1877 to the eastern slopes of the northern Peruvian Andes; and B. c. melanogaster Langhammer, 1983 to eastern Equador (Price and Russo, 1991). Island subspecies were described from Saboga Island located near mainland Panama (B. c. sabogae Barbour, 1906) and the Lesser Antilles (B. c. orophias Linnaeus, 1758; B. c. nebulosa Lazell, 1964; and B. c. sigma Smith, 1943) (Censky and Kaiser, 1999; Crother, 1999). New insight into the phylogenetic relationships among subspecies of B. constrictor may also serve as a foundation for conservation plans for this species. The Argentinean subspecies is included in Appendix I of the Convention of International Trade in Endangered Species of Wild Fauna and Flora (CITES), and the others are listed in Appendix II (Chiaroviglio et al., 2003; Rivera et al., 2005). Nevertheless, * Corresponding author. Phone: +420-221-951-846; Fax : +420-221-951-804; E-mail: frynta@centrum.cz doi:10.2108/zsj.26.623