Fitzpatrick, Benjamin M, Johnson, Jarrett R, Kump, D Kevin, Shaffer, H Bradley, Smith, Jeramiah J, Voss, S Randal
Abstract Background Hybrid zones represent valuable opportunities to observe evolution in systems that are unusually dynamic and where the potential for the origin of novelty and rapid adaptation...
Spinks, Phillip Q, Thomson, Robert C, Lovely, Geoff A, Shaffer, H Bradley
Abstract Background Phylogenies often contain both well-supported and poorly supported nodes. Determining how much additional data might be required to eventually recover most or all nodes with high...
Spinks, Phillip Q., Shaffer, H. Bradley
Understanding the mechanisms by which widely disjunct members of a clade came to occupy their current distribution is one of the fundamental challenges of biogeography. Here, we used data from 7...
Ian J. Wang, H. Bradley Shaffer
Aposematism is one of the great mysteries of evolutionary biology. The evolution of aposematic coloration is poorly understood, but even less understood is the evolution of polymorphism in aposematic...
Delimiting Species in Recent Radiations (2007)
Shaffer, H. Bradley, Thomson, Robert C.
Despite considerable effort from the systematics community, delimiting species boundaries in recent radiations remains a daunting challenge. We argue that genealogical approaches, although sometimes...
Phylogenetic hypotheses for the turtle family Geoemydidae (2004)
Spinks, Phillip Q, Shaffer, H Bradley, Iverson, J B, McCord, W P
The turtle family Geoemydidae represents the largest, most diverse, and most poorly understood family of turtles. Little is known about this group, including intrafamilial systematics. The only...
ENVIRONMENT-DEPENDENT ADMIXTURE DYNAMICS IN A TIGER SALAMANDER HYBRID ZONE (2004)
Benjamin M. Fitzpatrick, H. Bradley Shaffer
After an estimated five million years of independent evolution, the barred tiger salamander (Ambystoma tigrinum mavortium) was introduced by bait dealers into the native range of the California tiger...
Thomas J. Near, Peter A. Meylan, H. Bradley Shaffer
abstract: Although still controversial, estimation of divergence times using molecular data has emerged as a powerful tool to examine the tempo and mode of evolutionary change. Two primary obstacles...
Engstrom, Tag N., Shaffer, H. Bradley, McCord, William P.
We present a phylogenetic hypothesis and novel, rank-free classification for all extant species of softshell turtles (Testudines: Trionychidae). Our data set included DNA sequence data from two...
David E. Starkey, H. Bradley Shaffer, Russell L. Burke, John B. Iverson, Fredric J. Janzen, ...
The painted turtle, Chrysemys picta, is currently recognized as a continentally distributed polytypic species, ranging across North America from southern Canada to extreme northern Mexico. We...
Peter C. Trenham, H. Bradley Shaffer, Walter D. Koenig, Mark R. Stromberg
In December 1991, we initiated a long-term study of the California Tiger Salamander (Ambystoma californiense) at a breeding pond in Monterey County, California. Because of habitat loss, this species...
Tests of Turtle Phylogeny: Molecular, Morphological, and Paleontological Approaches (1997)
Shaffer, H. Bradley, Meylan, Peter, McKnight, Mark L.
We present phylogenetic analyses of both molecular and morphological data for the 23 major lineages of living turtles and seven key fossil taxa. Nearly 1 kilobase of cytochrome b sequence, 325 base...
SHAFFER, H. BRADLEY, VOSS, S. RANDAL
Many of the critical pieces are now in place to exploit the evolution of paedomorphosis (metamorphic failure) as a model for both the phylogenetic and mechanistic analysis of a developmentally...
Phylogenetics of Model Organisms: The Laboratory Axolotl, Ambystoma Mexicanum (1993)
The axolotl, Ambystoma mexicanum, has been an important model system in both developmental and evolutionary biology for over 100 years. The axolotl is a recently derived member of the Ambystoma...
Adaptive evolution via a major gene effect: Paedomorphosis in the Mexican axolotl
Voss, S. Randal, Shaffer, H. Bradley
Although adaptive evolution is thought to depend primarily on mutations of small effect, major gene effects may underlie many of the important differences observed among species in nature. The...
Adaptive evolution via a major gene effect: Paedomorphosis in the Mexican axolotl
Voss, S. Randal, Shaffer, H. Bradley
Although adaptive evolution is thought to depend primarily on mutations of small effect, major gene effects may underlie many of the important differences observed among species in nature. The...
Hybrid vigor between native and introduced salamanders raises new challenges for conservation
Fitzpatrick, Benjamin M., Shaffer, H. Bradley
Hybridization between differentiated lineages can have many different consequences depending on fitness variation among hybrid offspring. When introduced organisms hybridize with natives, the ensuing...