Comparative phylogeography and population genetics within Buteo lineatus reveals evidence of distinct evolutionary lineages Joshua M. Hull a, * , Bradley N. Strobel b , Clint W. Boal b , Angus C. Hull c , Cheryl R. Dykstra d , Amanda M. Irish a , Allen M. Fish c , Holly B. Ernest a,e a Wildlife and Ecology Unit, Veterinary Genetics Laboratory, 258 CCAH, University of California, One Shields Avenue, Davis, CA 95616, USA b U.S. Geological Survey Texas Cooperative Fish and Wildlife Research Unit, Department of Natural Resources Management, Texas Tech University, Lubbock, TX 79409, USA c Golden Gate Raptor Observatory, Building 1064 Fort Cronkhite, Sausalito, CA 94965, USA d Raptor Environmental, 7280 Susan Springs Drive, West Chester, OH 45069, USA e Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, One Shields Avenue/Old Davis Road, Davis, CA 95616, USA article info Article history: Received 25 June 2008 Revised 13 September 2008 Accepted 17 September 2008 Available online 26 September 2008 Keywords: Red-shouldered Hawk Buteo lineatus Microsatellite Mitochondria Isolation Historical demography abstract Traditional subspecies classifications may suggest phylogenetic relationships that are discordant with evolutionary history and mislead evolutionary inference. To more accurately describe evolutionary rela- tionships and inform conservation efforts, we investigated the genetic relationships and demographic histories of Buteo lineatus subspecies in eastern and western North America using 21 nuclear microsatel- lite loci and 375-base pairs of mitochondrial control region sequence. Frequency based analyses of mito- chondrial sequence data support significant population distinction between eastern (B. l. lineatus/alleni/ texanus) and western (B. l. elegans) subspecies of B. lineatus. This distinction was further supported by fre- quency and Bayesian analyses of the microsatellite data. We found evidence of differing demographic his- tories between regions; among eastern sites, mitochondrial data suggested that rapid population expansion occurred following the end of the last glacial maximum, with B. l. texanus population expan- sion preceding that of B. l. lineatus/alleni. No evidence of post-glacial population expansion was detected among western samples (B. l. elegans). Rather, microsatellite data suggest that the western population has experienced a recent bottleneck, presumably associated with extensive anthropogenic habitat loss during the 19th and 20th centuries. Our data indicate that eastern and western populations of B. lineatus are genetically distinct lineages, have experienced very different demographic histories, and suggest man- agement as separate conservation units may be warranted. Ó 2008 Elsevier Inc. All rights reserved. 1. Introduction The taxonomic rank of subspecies has a controversial history in evolutionary biology (Wilson and Brown 1953; Mayr 1982; Philli- more and Owens 2006). Ideally, subspecies should reflect evolu- tionary potential and relationships within species, and provide a framework for prioritizing conservation efforts (Zink 2004; Haig et al. 2006); however, inconsistent application and definition have often limited the utility of the subspecies rank (Zink 2004). While more recent species concepts have been developed to describe evo- lutionary differentiation (Ryder 1986; Mortiz, 1994; de Queiroz, 2005), the rank of subspecies is still widely applied. Use of the subspecies rank is common in ornithology (Zink 2004), where subspecies are often described as geographic seg- ments of a species that, although not reproductively isolated from each other, differ in morphology or coloration, and may be associ- ated with differences in habitat and behavior (AOU, 1983). Use of these particular distinctions may mislead evolutionary inference (Zink 2004; Phillimore and Owens 2006); during initial periods of divergence, relative differences in the rates of morphological and neutral genetic evolution may result in conflicting patterns of differentiation (AOU, 1983; Bromham et al., 2002; Hull et al., in press). Therefore, some named subspecies may be phenotypi- cally distinct yet genetically similar (e.g., Avise and Nelson 1989; Ball and Avise 1992; Zink, 2004) while other evolutionarily distinct lineages remain unrecognized due to retained similarities in mor- phology or habitat preferences (Isler et al. 2002). Molecular genetic investigations of wide-ranging species with several recognized subspecies provide an opportunity to under- stand the ecological, behavioral, and evolutionary patterns respon- sible for differentiation, and evaluate the support for subspecific status. Such studies may be particularly useful in avian taxa where a high degree of mobility may obfuscate detection and description of within-species divergence. Additionally, molecular genetic anal- yses of subspecies complexes may aid conservation efforts by more clearly defining within-species differentiation and identifying the factors responsible for maintaining observed patterns of diversity. 1055-7903/$ - see front matter Ó 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.ympev.2008.09.010 * Corresponding author. Fax: +1 530 754 5518. E-mail address: jmhull@ucdavis.edu (J.M. Hull). Molecular Phylogenetics and Evolution 49 (2008) 988–996 Contents lists available at ScienceDirect Molecular Phylogenetics and Evolution journal homepage: www.elsevier.com/locate/ympev