Functional and evolutionary parallels between birdsong and human musicality.

Here, we compare birdsong and human musicality using insights from songbird neuroethology and evolution. For example, neural recordings during songbird duetting and other coordinated vocal behaviors could inform mechanistic hypotheses regarding human brain function during music-making. Furthermore, considering songbird evolution as a model system suggests that selection favoring certain culturally transmitted behaviors can indirectly select for associated underlying neural functions.

Food-seeking behavior has complex evolutionary pressures in songbirds: Linking parental foraging to offspring sexual selection.

The target article addresses increased food-seeking behaviors in times of instability, particularly in passerines. We note that food instability might have intergenerational effects on birds: Nutritional stress during development affects song-learning abilities, associating parental foraging with offspring sexual selection. We explore the implications of these compounding selection pressures on food-seeking motivation during breeding, as well as the hormonal underpinnings of these behaviors.

Polyomavirus-associated Disseminated T-cell Lymphoma in a Colony of Zebra Finches (Taeniopygia guttata).

Four zebra finches in a closed research colony presented with variable clinical signs, including masses, skin lesions, shivering, and/or ruffled feathers. These birds were not responsive to treatment efforts; 3 died and one was euthanized. All 4 were submitted for necropsy to determine the cause of the clinical signs. Gross necropsy and histopathologic findings from all birds resulted in a diagnosis of round cell neoplasia in multiple organs, including the skin, liver, kidney, and reproductive tract, with intranuclear inclusion bodies in the neoplastic cells. In all 4 cases, immunohistochemical staining showed strong immunoreactivity for CD3 in 70% to 80% of the neoplastic round cells, with a relatively small subset that were immunopositive for Pax5. These findings supported a diagnosis of T-cell lymphoma. Frozen liver tissue from one case was submitted for next-generation sequencing (NGS), which revealed viral RNA with 100% sequence homology to canary polyomavirus strain 34639 that had originally been identified in a European goldfinch. Formalin-fixed paraffin-embedded scrolls from another case were also submitted for NGS, which revealed viral RNA with 97.2% sequence homology to canary polyomavirus strain 37273 that had originally been identified in a canary. To localize the virus in situ, RNAscope hybridization was performed using a probe designed to target the VP1 gene of the sequenced virus in frozen liver tissue. In all 4 cases, disseminated and robust hybridization signals were detected in neoplastic cells. These findings indicate that polyomaviruses have the potential to be oncogenic in zebra finches.

Structured growth and genetic drift raise relatedness in the social amoeba Dictyostelium discoideum.

One condition for the evolution of altruism is genetic relatedness between altruist and beneficiary, often achieved through active kin recognition. Here, we investigate the power of a passive process resulting from genetic drift during population growth in the social amoeba Dictyostelium discoideum. We put labelled and unlabelled cells of the same clone in the centre of a plate, and allowed them to proliferate outward. Zones formed by genetic drift owing to the small population of actively growing cells at the colony edge. We also found that single cells could form zones of high relatedness. Relatedness increased at a significantly higher rate when food was in short supply. This study shows that relatedness can be significantly elevated before the social stage without a small founding population size or recognition mechanism.

Polygyny is linked to accelerated birdsong evolution but not to larger song repertoires.

Non-monogamous mating behaviors including polygyny or extra-pair paternity are theorized to amplify sexual selection, since some males attract multiple mates or copulate with paired females. In several well-studied songbird species, females prefer more complex songs and larger repertoires; thus, non-monogamous mating behaviors are predicted to accelerate song evolution, particularly toward increased complexity. However, studies within songbird clades have yielded mixed results, and the effect of non-monogamy on song evolution remains unclear. Here, we construct a large-scale database synthesizing mating system, extra-pair paternity, and song information and perform comparative analyses alongside songbird genetic phylogenies. Our results suggest that polygyny drives faster evolution of syllable repertoire size (measured as average number of unique syllables), but this rapid evolution does not produce larger repertoires in polygynous species. Instead, both large and small syllable repertoires quickly evolve toward moderate sizes in polygynous lineages. Contrary to expectation, high rates of extra-pair paternity coincide with smaller repertoires.

A worldwide view of matriliny: using cross-cultural analyses to shed light on human kinship systems.

Although matriliny and matrilocality are relatively rare in contemporary human populations, these female-based descent and residence systems are present in different cultural contexts and across the globe. Previous research has generated numerous hypotheses about which cultural traits are associated with the stability or loss of matrilineal descent. In addition, several studies have examined matrilineal descent with phylogenetic analyses; however, the use of language phylogenies has restricted these analyses to comparisons within a single language family, often confined to a single continent. Cross-cultural comparisons are particularly informative when they account for the relationships between widely distributed populations, as opposed to treating each population as an independent sample or focusing on a single region. Here, we study the evolution of descent systems on a worldwide scale. First, we test for significant associations between matriliny and numerous cultural traits that have been theoretically associated with its stability or loss, such as subsistence strategy, animal domestication, mating system, residence pattern, wealth transfer and property succession. In addition, by combining genetic and linguistic information to build a global supertree that includes 16 matrilineal populations, we also perform phylogenetically controlled analyses to assess the patterns of correlated evolution between descent and other traits: for example, does a change in subsistence strategy generally predict a shift in the rules of descent, or do these transitions happen independently? These analyses enable a worldwide perspective on the pattern and process of the evolution of matriliny and matrilocality. This article is part of the theme issue 'The evolution of female-biased kinship in humans and other mammals'.

Correlated evolution between repertoire size and song plasticity predicts that sexual selection on song promotes open-ended learning.

Some oscine songbird species modify their songs throughout their lives ('adult song plasticity' or 'open-ended learning'), while others crystallize their songs around sexual maturity. It remains unknown whether the strength of sexual selection on song characteristics, such as repertoire size, affects adult song plasticity, or whether adult song plasticity affects song evolution. Here, we compiled data about song plasticity, song characteristics, and mating system and then examined evolutionary interactions between these traits. Across 67 species, we found that lineages with adult song plasticity show directional evolution toward increased syllable and song repertoires, while several other song characteristics evolved faster, but in a non-directional manner. Song plasticity appears to drive bi-directional transitions between monogamous and polygynous social mating systems. Notably, our analysis of correlated evolution suggests that extreme syllable and song repertoire sizes drive the evolution of adult song plasticity or stability, providing novel evidence that sexual selection may indirectly influence open- versus closed-ended learning.