Cryptic genetic variation and paraphyly in ravens

Abstract

Widespread species that are morphologically uniform may be likely to harbour cryptic genetic variation. Common ravens (Corvus corax) have an extensive range covering nearly the entire Northern Hemisphere, but show little discrete phenotypic variation. We obtained tissue samples from throughout much of this range and collected mitochondrial sequence and nuclear microsatellite data. Our study revealed a deep genetic break between ravens from the western United States and ravens from throughout the rest of the world. These two groups, the`California clade' and the`Holarctic clade' are well supported and over 4% divergent in mitochondrial coding sequence. Microsatellites also reveal signi¢cant di¡erentiation between these two groups. Ravens from Minnesota, Maine and Alaska are more similar to ravens from Asia and Europe than they are to ravens from California. The two clades come in contact over a huge area of the western United States, with mixtures of the two mitochondrial groups present in Washington, Idaho and California. In addition, the restricted range Chihuahuan raven (Corvus cryptoleucus) of the south-west United States and Mexico is genetically nested within the paraphyletic common raven. Our ¢ndings suggest that the common raven may have formerly consisted of two allopatric groups that may be in the process of remerging.

Mathematical Consequences of the Genealogical Species Concept

“…Takahata and Slatkin (1984) show that if mtDNA is neutral, only a trickle of gene flow can cause substantial introgression of this DNA between taxa, even if there is substantial hybrid unfitness based on differences in nuclear DNA. It is worth noting that most published claims of paraphyletic species involve phylogenetic analysis based solely on mtDNA (e.g., Melnick et al 1993;Omland et al 2000), and analysis of nuclear loci may show that the paraphyly is not pervasive throughout the genome, particularly if one adheres to the autapomorphic species concept. Our main point, however, is that phenomena such as selective sweeps and introgression can substantially accelerate or decelerate the attainment of monophyly, and that the effects of these forces may be far greater on mtDNA than on a sample of nuclear genes.…”

Habitat selection and ecological speciation in Galápagos warbler finches ( Certhidea olivacea and Certhidea fusca )

“…Molecular methods have previously revealed cryptic speciation in birds, but it has typically been associated with geographical variation (e.g. Avise & Nelson 1989;Omland et al 2000). Habitat choice has been implicated in speciation of other organisms, for instance, in insects that specialize on different hosts (Via 1999).…”

Phylogenetic relationships of Amazonian anole lizards (Dactyloa): Taxonomic implications, new insights about phenotypic evolution and the timing of diversification

“…Given the documented role of anole dewlaps in species recognition and presumably reproductive isolation (e.g., Losos, 1985;Macedonia and Stamps, 1994;Sigmund, 1983), these results may indicate that D. philopunctata is still in its very first stages of speciation. A vast number of studies have documented paraphyly among animal species that are phenotypically and often ecologically distinct (e.g., Brown and Twomey, 2009;Johnson et al, 2005;McKay and Zink, 2010;Omland et al, 2000), including anoles (Thorpe and Stenson, 2003). From the perspective of allele coalescence, the speciation process inherently starts with paraphyly in gene genealogies, and the probability of achieving reciprocal monophyly increases with time since population divergence (Knowles and Carstens, 2007).…”