Genetics, Taxonomy, and Conservation of the Threatened California Gnatcatcher

Abstract

The California Gnatcatcher ( Polioptila californica) has become a flagship species in the dispute over development of southern California's unique coastal sage scrub habitat, a fragile, geographically restricted ecosystem with high endemism. One aspect of the controversy concerns the status of the subspecies of this bird in southern California coastal sage scrub that is currently listed as threatened under the U.S. Endangered Species Act. To investigate the recent population history of this species and the genetic distinctiveness of subspecies and to inform conservation planning, we used direct sequencing of mitochondrial DNA (mtDNA) for 64 individuals from 13 samples taken throughout the species' range. We found that coastal sage scrub populations of California Gnatcatchers are not genetically distinct from populations in Baja California, which are dense and continuously distributed throughout the peninsula. Rather, mtDNA sequences from this species contain the signatures of population growth and support a hypothesis of recent expansion of populations from a southern Baja California refugium northward into the southern coastal regions of California. During this expansion, stochastic events led to a reduction in genetic variation in the newly occupied range. Thus, preservation of coastal sage scrub cannot be linked to maintaining the genetic diversity of northern gnatcatcher populations, despite previous recognition of subspecies. Our study suggests that not all currently recognized subspecies are equivalent to evolutionarily significant units and illustrates the danger of focusing conservation efforts for threatened habitats on a single species.

Subspecific relationships and genetic structure in the spotted owl

“…Endangered Species Act has stimulated greater interest in these topics. To date, most of these cases have involved non-avian taxa (e.g., Allendorf and Leary 1988;Bernatchez 1995;Firestone et al 1999;Parker et al 1999;Roman et al 1999; although see Avise and Nelson 1989;Young and Allard 1997;Nelson et al 2000;Zink et al 2000). In this study, we examine population structure as well as relationships within and among geographically-defined subspecies for a threatened avian species with little morphological variation yet historical divergence among subspecies.…”

Variación fenotípica infraespecífica de la codorniz de California (Callipepla californica, Aves: Odontophoridae) de la península de Baja California, México

“…californica, la cual habita zonas de matorral costero en California y Baja California (Zink et al 2000, Zink et al 2013. En aves de importancia cinegética, son muy escasos los trabajos que abordan esta problemática taxonómica, a pesar de la importancia que implica una identificación infraespecí-fica adecuada para su conservación.…”

Forest Structure Within Barred Owl (Strix varia) Home Ranges in the Eastern Cascade Range, Washington

“…In this vein, Moritz' (1994b) definition was developed, and relies largely on the determination of reciprocal monophyly in mtDNA sequences (each geographically based population coalesces to a common mtDNA haplotype ancestor) and significant differentiation of nuclear gene allele frequencies. This definition has been used widely in conservation biology, and is perhaps the definition most often applied to assess avian ESUs (e.g., Fleischer 1998, Lovette et al 1999, Tarr and Fleischer 1999, Zink et al 2000. A more recent method for defining ESU's incorporates information from morphological and ecological traits, as well as molecular characters (Crandall et al, 2000).…”