The tempo of species diversification in large clades can reveal fundamental evolutionary mechanisms that operate on large temporal and spatial scales. Hummingbirds have radiated into a diverse assemblage of specialized nectarivores comprising 338 species, but their evolutionary history has not, until now, been comprehensively explored. We studied hummingbird diversification by estimating a time-calibrated phylogeny for 284 hummingbird species, demonstrating that hummingbirds invaded South America by ∼22 million years ago, and subsequently diversified into nine principal clades (see [5-7]). Using ancestral state reconstruction and diversification analyses, we (1) estimate the age of the crown-group hummingbird assemblage, (2) investigate the timing and patterns of lineage accumulation for hummingbirds overall and regionally, and (3) evaluate the role of Andean uplift in hummingbird speciation. Detailed analyses reveal disparate clade-specific processes that allowed for ongoing species diversification. One factor was significant variation among clades in diversification rates. For example, the nine principal clades of hummingbirds exhibit ∼15-fold variation in net diversification rates, with evidence for accelerated speciation of a clade that includes the Bee, Emerald, and Mountain Gem groups of hummingbirds. A second factor was colonization of key geographic regions, which opened up new ecological niches. For example, some clades diversified in the context of the uplift of the Andes Mountains, whereas others were affected by the formation of the Panamanian land bridge. Finally, although species accumulation is slowing in all groups of hummingbirds, several major clades maintain rapid rates of diversification on par with classical examples of rapid adaptive radiation.

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Polymorphism may play an important role in speciation because new species could originate from the distinctive morphs observed in polymorphic populations. However, much remains to be understood about the process by which morphs found new species. To detail the steps of this mode of speciation, we studied the geographic variation and evolutionary history of a throat color polymorphism that distinguishes the "rock-paper-scissors" mating strategies of the sideblotched lizard, Uta stansburiana. We found that the polymorphism is geographically widespread and has been maintained for millions of years. However, there are many populations with reduced numbers of throat color morphs. Phylogenetic reconstruction showed that the polymorphism is ancestral, but it has been independently lost eight times, often giving rise to morphologically distinct subspecies/species. Changes to the polymorphism likely involved selection because the allele for one particular male strategy, the "sneaker" morph, has been lost in all cases. Polymorphism loss was associated with accelerated evolution of male size, female size, and sexual dimorphism, which suggests that polymorphism loss can promote rapid divergence among populations and aid species formation.lizard | morph | phylogeny | rock-paper-scissors | Uta stansburiana P olymorphic forms within a population could be the starting material for new species (1-4). Tests of how polymorphisms diversify into new lineages have been relatively rare (2, 5, 6), despite increasing recognition that polymorphisms, such as alternative mating strategies, are common within species (7-9). Here we investigate the processes by which a morph in a polymorphic population may diverge to found a new species.Competition within a population can generate morphs possessing alternative adaptations, which may become as phenotypically distinct as separate species and thus primed for speciation (2, 3). WestEberhard theorized how morphs may promote speciation (2, 10) and suggested that selection in new environments may favor a particular morph, destabilizing the dynamics maintaining the polymorphism. If a population loses a morph, this can lead to rapid phenotypic divergence in the remaining morph(s) (2). One cause of rapid divergence is that genetic evolution may be constrained in polymorphic populations, because alleles that increase the fitness of a single morph but decrease the fitness of other morphs may be unable to spread. Loss of a morph allows these alleles to spread, which can result in rapid phenotypic evolution in the direction of specialization on the remaining morph phenotypes, a process called character release (2). Another reason for rapid evolution coincident with morph loss is that colonization of a new ecological environment may select against a particular morph and also favor novel phenotypes in the remaining morphs. In addition, loss of a morph changes the competitive environment, because the fitness of morphs can depend on the frequency of other types in the population (8). Rapid evolution may occur ...

The consequences of alcohol use disorders (AUDs) are devastating to individuals and society, yet few treatments are currently available. To identify genes regulating the behavioral effects of ethanol, we conducted a genetic screen in Drosophila and identified a mutant, happyhour (hppy), due to its increased resistance to the sedative effects of ethanol. Hppy protein shows strong homology to mammalian Ste20 family kinases of the GCK-1 subfamily. Genetic and biochemical experiments revealed that the epidermal growth factor (EGF)-signaling pathway regulates ethanol sensitivity in Drosophila and that Hppy functions as an inhibitor of the pathway. Acute pharmacological inhibition of the EGF receptor (EGFR) in adult animals altered acute ethanol sensitivity in both flies and mice and reduced ethanol consumption in a preclinical rat model of alcoholism. Inhibitors of the EGFR or components of its signaling pathway are thus potential pharmacotherapies for AUDs.