The macroevolutionary dynamics of pharyngognathy in fishes fail to support the key innovation hypothesis.

Key innovations, traits that provide species access to novel niches, are thought to be a major generator of biodiversity. One commonly cited example of key innovation is pharyngognathy, a set of modifications to the pharyngeal jaws found in some highly species-rich fish clades such as cichlids and wrasses. Here, using comparative phylogenomics and phylogenetic comparative methods, we investigate the genomic basis of pharyngognathy and the impact of this innovation on diversification.

Interpeduncular GABAergic neuron function controls threat processing and innate defensive adaptive learning.

The selection of appropriate defensive behaviors in the face of potential threat is fundamental to survival. However, after repeated exposures to threatening stimuli that did not signal real danger, an animal must learn to adjust and optimize defensive behaviors. Despite extensive research on innate threat processing, little is known how individuals change their defensive behaviors when presented with recurrent threat exposures without evidence of a real risk.

Noise leads to the perceived increase in evolutionary rates over short time scales.

Across a variety of biological datasets, from genomes to conservation to the fossil record, evolutionary rates appear to increase toward the present or over short time scales. This has long been seen as an indication of processes operating differently at different time scales, even potentially as an indicator of a need for new theory connecting macroevolution and microevolution. Here we introduce a set of models that assess the relationship between rate and time and demonstrate that these patterns are statistical artifacts of time-independent errors present across ecological and evolutionary datasets, which produce hyperbolic patterns of rates through time.

Shifts in evolutionary lability underlie independent gains and losses of root-nodule symbiosis in a single clade of plants.

Root nodule symbiosis (RNS) is a complex trait that enables plants to access atmospheric nitrogen converted into usable forms through a mutualistic relationship with soil bacteria. Pinpointing the evolutionary origins of RNS is critical for understanding its genetic basis, but building this evolutionary context is complicated by data limitations and the intermittent presence of RNS in a single clade of ca. 30,000 species of flowering plants, i.