Shea M Lambert

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Simulation studies suggest that coalescent-based species-tree methods are generally more accurate than concatenated analyses. However, these species-tree methods remain impractical for many large datasets. Thus, a critical but unresolved issue is when and why concatenated and coalescent species-tree estimates will differ. We predict such differences for(More)
The evolution of viviparity is a key life-history transition in vertebrates, but the selective forces favoring its evolution are not fully understood. With >100 origins of viviparity, squamate reptiles (lizards and snakes) are ideal for addressing this issue. Some evidence from field and laboratory studies supports the "cold-climate" hypothesis, wherein(More)
Life-history modes can profoundly impact the biology of a species, and a classic example is the dichotomy between metamorphic (biphasic) and paedomorphic (permanently aquatic) life-history strategies in salamanders. However, despite centuries of research on this system, several basic questions about the evolution of paedomorphosis in salamanders have not(More)
We describe a new species of Boophis treefrog from Ranomafana National Park in the southern central east of Madagascar. This region has remarkably high anuran diversity, and along with neighbouring sites, hosts more than 35 Boophis species. Boophis boppa sp. nov. is part of the B. ankaratra sub-clade (herein named the B. ankaratra complex), previously(More)
The pattern of reproductive character displacement (RCD)-in which traits associated with reproductive isolation are more different where two species occur together than where they occur in isolation-is frequently attributed to reinforcement, a process during which natural selection acting against maladaptive mating events leads to enhanced prezygotic(More)
Guanine nucleotides regulate binding of opiate agonists to membrane receptors by increasing agonist dissociation rates. The current study demonstrates that the ability of guanosine 5'-triphosphate (GTP) and its nonhydrolyzable analogue guanylyl-5'-imidodiphosphate (Gpp(NH)p) to inhibit opiate agonist binding to rat brain membranes can be altered by two(More)
The Tropical Andes make up Earth's most species-rich biodiversity hotspot for both animals and plants. Nevertheless, the ecological and evolutionary processes underlying this extraordinary richness remain uncertain. Here, we examine the processes that generate high richness in the Tropical Andes relative to other regions in South America and across(More)
Pretreatment of rat brain membranes at pH 4.5 increased GTP and Gpp(NH)p regulation of [3H]-D-ala2-met5-enkephalinamide (D-ala-enk) binding with no change in absolute binding itself. Pretreatment at pH 4.5 did not alter basal adenylate cyclase activity but did cause a loss (50-90%) in NaF- and Gpp(NH)p-stimulated activity, indicating a functional loss of(More)