FLEXIBILITY IN GENE COEXPRESSION AT DEVELOPMENTAL AND EVOLUTIONARY TIMESCALES.

The explosion of next-generation sequencing technologies has allowed researchers to move from studying single genes, to thousands of genes, and thereby to also consider the relationships within gene networks. Like others, we are interested in understanding how developmental and evolutionary forces shape the expression of individual genes, as well as the interactions among genes. To this end, we characterized the effects of genetic background and developmental environment on brain gene coexpression in two parallel, independent evolutionary lineages of Trinidadian guppies ().

In your CORT: Corticosterone and its receptors in the brain underlie mate choosiness in female Cope's gray treefrogs (Hyla chrysoscelis).

Selecting an attractive mate can involve trade-offs related to investment in sampling effort. Glucocorticoids like corticosterone (CORT) are involved in resolving energetic trade-offs. However, CORT is rarely studied in the context of mate choice, despite its elevated levels during reproductive readiness and the energetic transitions that characterize reproduction.

Convergent Anuran Middle Ear Loss Lacks a Universal, Adaptive Explanation.

Introduction: Shared selection pressures often explain convergent trait loss, yet anurans (frogs and toads) have lost their middle ears at least 38 times with no obvious shared selection pressures unifying "earless" taxa. Anuran tympanic middle ear loss is especially perplexing because acoustic communication is dominant within Anura and tympanic middle ears enhance airborne hearing in most tetrapods.

Methods: Here, we use phylogenetic comparative methods to examine whether particular geographic ranges, microhabitats, activity patterns, or aspects of acoustic communication are associated with anuran tympanic middle ear loss.

Sexual signal evolution and patterns of assortative mating across an intraspecific contact zone.

Contact zones provide important insights into the evolutionary processes that underlie lineage divergence and speciation. Here, we use a contact zone to ascertain speciation potential in the red-eyed treefrog (Agalychnis callidryas), a brightly coloured and polymorphic frog that exhibits unusually high levels of intraspecific variation. Populations of A.

Peripheral Auditory System Divergence Does Not Explain Species Differences in Call Preference.

Receiver sensory systems have long been cited as an important source of variation in mate preferences that could lead to signal diversification and behavioral isolation between lineages, with a general assumption that animals prefer the most conspicuous signals. The matched filter hypothesis posits that tuning of the frog peripheral auditory system matches dominant frequencies in advertisement calls used to attract mates. However, little work has characterized species with frequency modulation in their calls.

Reintegrating Biology Through the Nexus of Energy, Information, and Matter.

Information, energy, and matter are fundamental properties of all levels of biological organization, and life emerges from the continuous flux of matter, energy, and information. This perspective piece defines and explains each of the three pillars of this nexus. We propose that a quantitative characterization of the complex interconversions between matter, energy, and information that comprise this nexus will help us derive biological insights that connect phenomena across different levels of biological organization.

Spatio-temporal Dynamics in Animal Communication: A Special Issue Arising from a Unique Workshop-Symposium Model.

Investigating how animals navigate space and time is key to understanding communication. Small differences in spatial positioning or timing can mean the difference between a message received and a missed connection. However, these spatio-temporal dynamics are often overlooked or are subject to simplifying assumptions in investigations of animal signaling.

How Signaling Geometry Shapes the Efficacy and Evolution of Animal Communication Systems.

Animal communication is inherently spatial. Both signal transmission and signal reception have spatial biases-involving direction, distance, and position-that interact to determine signaling efficacy. Signals, be they visual, acoustic, or chemical, are often highly directional.

Nonparallel transcriptional divergence during parallel adaptation.

How underlying mechanisms bias evolution toward predictable outcomes remains an area of active debate. In this study, we leveraged phenotypic plasticity and parallel adaptation across independent lineages of Trinidadian guppies (Poecilia reticulata) to assess the predictability of gene expression evolution during parallel adaptation. Trinidadian guppies have repeatedly and independently adapted to high- and low-predation environments in the wild.

A biologist's guide to model selection and causal inference.

A goal of many research programmes in biology is to extract meaningful insights from large, complex datasets. Researchers in ecology, evolution and behavior (EEB) often grapple with long-term, observational datasets from which they construct models to test causal hypotheses about biological processes. Similarly, epidemiologists analyse large, complex observational datasets to understand the distribution and determinants of human health.

Whispers from vestigial nubbins: Arrested development provokes trait loss in toads.

Despite the use of acoustic communication, many species of toads (family Bufonidae) have lost parts of the tympanic middle ear, representing at least 12 independent evolutionary occurrences of trait loss. The comparative development of the tympanic middle ear in toads is poorly understood. Here, we compared middle ear development among two pairs of closely related toad species in the genera Atelopus and Rhinella that have (eared) or lack (earless) middle ear structures.

Dynamics of perineuronal nets over amphibian metamorphosis.

Extracellular matrix materials known as perineuronal nets (PNNs) have been shown to have remarkable consequences for the maturation of neural circuits and stabilization of behavior. It has been proposed that, due to the possibly long-lived biochemical nature of their components, PNNs may be an important substrate by which long-term memories are stored in the central nervous system. However, little empirical evidence exists that shows that PNNs are themselves stable once established.

Larger Genomes Linked to Slower Development and Loss of Late-Developing Traits.

Genome size varies widely among organisms and is known to affect vertebrate development, morphology, and physiology. In amphibians, genome size is hypothesized to contribute to loss of late-forming structures, although this hypothesis has mainly been discussed in salamanders. Here we estimated genome size for 22 anuran species and combined this novel data set with existing genome size data for an additional 234 anuran species to determine whether larger genome size is associated with loss of a late-forming anuran sensory structure, the tympanic middle ear.

Prolonged middle ear development in Rhinella horribilis.

Despite the benefit of the tympanic middle ear to airborne hearing sensitivity, anurans range in how soon they develop functional middle ears after transitioning to life on land. Previous evidence suggested that bufonids had particularly slow middle ear developmental rates, but precise timelines have not yet been published for this family. Here, we provide the first age-verified middle ear development timeline for a true toad species (family Bufonidae).

Sensitive high-frequency hearing in earless and partially eared harlequin frogs ().

Harlequin frogs, genus , communicate at high frequencies despite most species lacking a complete tympanic middle ear that facilitates high-frequency hearing in most anurans and other tetrapods. Here, we tested whether are better at sensing high-frequency acoustic sound compared with other eared and earless species in the Bufonidae family, determined whether middle ear variation within affects hearing sensitivity and tested potential hearing mechanisms in We determined that at high frequencies (2000-4000 Hz), are 10-34 dB more sensitive than other earless bufonids but are relatively insensitive to mid-range frequencies (900-1500 Hz) compared with eared bufonids. Hearing among species is fairly consistent, evidence that the partial middle ears present in a subset of species do not convey a substantial hearing advantage.

Erratum: Non-adaptive plasticity potentiates rapid adaptive evolution of gene expression in nature.

This corrects the article DOI: 10.1038/nature15256.

Trait independence primes convergent trait loss.

The repeated, independent evolution of traits (convergent evolution) is often attributed to shared environmental selection pressures. However, developmental dependencies among traits can limit the phenotypic variation available to selection and bias evolutionary outcomes. Here, we determine how changes in developmentally correlated traits may impact convergent loss of the tympanic middle ear, a highly labile trait within toads that currently lack adaptive explanation.

Neural Circuitry for Target Selection and Action Selection in Animal Behavior.

Animal behaviorists have long strived for a comprehensive understanding of the proximate and ultimate causes of complex behavior, and we propose that recent advances in neurobiology can help reshape or clarify this behavior-oriented understanding. We begin with an overview of current views of neural circuit mechanisms that mediate target selection and action selection. In target selection, different stimuli compete for priority in sensory-motor processing.

Earless toads sense low frequencies but miss the high notes.

Sensory losses or reductions are frequently attributed to relaxed selection. However, anuran species have lost tympanic middle ears many times, despite anurans' use of acoustic communication and the benefit of middle ears for hearing airborne sound. Here we determine whether pre-existing alternative sensory pathways enable anurans lacking tympanic middle ears (termed earless anurans) to hear airborne sound as well as eared species or to better sense vibrations in the environment.

Mating patterns and post-mating isolation in three cryptic species of the Engystomops petersi species complex.

Determining the extent of reproductive isolation in cryptic species with dynamic geographic ranges can yield important insights into the processes that generate and maintain genetic divergence in the absence of severe geographic barriers. We studied mating patterns, propensity to hybridize in nature and subsequent fertilization rates, as well as survival and development of hybrid F1 offspring for three nominal species of the Engystomops petersi species complex in Yasuní National Park, Ecuador. We found at least two species in four out of six locations sampled, and 14.

Better late than never: effective air-borne hearing of toads delayed by late maturation of the tympanic middle ear structures.

Most vertebrates have evolved a tympanic middle ear that enables effective hearing of airborne sound on land. Although inner ears develop during the tadpole stages of toads, tympanic middle ear structures are not complete until months after metamorphosis, potentially limiting the sensitivity of post-metamorphic juveniles to sounds in their environment. We tested the hearing of five species of toads to determine how delayed ear development impairs airborne auditory sensitivity.

The complex evolutionary history of the tympanic middle ear in frogs and toads (Anura).

Most anurans possess a tympanic middle ear (TME) that transmits sound waves to the inner ear; however, numerous species lack some or all TME components. To understand the evolution of these structures, we undertook a comprehensive assessment of their occurrence across anurans and performed ancestral character state reconstructions. Our analysis indicates that the TME was completely lost at least 38 independent times in Anura.