Brent M Horton

Millersville University · Department of Biology

The neurogenomic mechanisms mediating male–male reproductive cooperative behaviours remain unknown. We leveraged extensive transcriptomic and behavioural data on a neotropical bird species ( Pipra filicauda ) that performs cooperative courtship displays to understand these mechanisms. In this species, the cooperative display is modulated by testost...

Organismal behavior, with its tremendous complexity and diversity, is generated by numerous physiological systems acting in coordination. Understanding how these systems evolve to support differences in behavior within and among species is a longstanding goal in biology that has captured the imagination of researchers who work on a multitude of tax...

The neurogenomic mechanisms mediating cooperative behaviors are understudied. We leveraged extensive transcriptomic and behavioral data on a neotropical bird (Pipra filicauda) that perform cooperative courtship displays to better understand the underlying mechanisms. Cooperative display is modulated by testosterone, it promotes cooperation in non-t...

Global biodiversity decline is continuing largely unabated. The International Union for Conservation of Nature (IUCN) Red List of Threatened Species (hereafter, Red List) provides us with the gold standard for assessments, but taxonomic coverage, especially for invertebrates and fungi, remains very low. Many players contribute to the Red List knowl...

The advent of high-throughput sequencing technologies, such as 16S rRNA amplicon sequencing, has enabled the characterization of microbial communities across diverse ecosystems including animal carrion. Although most studies on postmortem microbial communities focus on its application to human death scene analysis, this technique holds great potent...

The white-throated sparrow (Zonotrichia albicollis) offers unique opportunities to understand the adaptive value of supergenes, particularly their role in alternative phenotypes. In this species, alternative plumage morphs segregate with a nonrecombining segment of chromosome 2, which has been called a 'supergene'. The species mates disassortativel...

Social networks can vary in their organization and dynamics, with implications for ecological and evolutionary processes. Understanding the mechanisms that drive social network dynamics requires integrating individual‐level biology with comparisons across multiple social networks. Testosterone is a key mediator of vertebrate social behaviour and ca...

Supergenes, or linked groups of alleles that are inherited together, present excellent opportunities to understand gene-behaviour relationships. In white-throated sparrows (Zonotrichia albicollis), a supergene on the second chromosome associates with a more aggressive and less parental phenotype. This supergene includes the gene for vasoactive inte...

Many studies have identified the reproductive benefits of cooperative behaviors, yet few have identified the mechanisms that underlie these behaviors. Mechanistic studies can inform our understanding of why some individuals are more or less cooperative, as well as identify the physiological constraints imposed upon the evolution of reproductive tra...

Stable cooperation requires plasticity whereby individuals are able to express competitive or cooperative behaviors depending on social context. To date, however, the physiological mechanisms that underlie behavioral variation in cooperative systems are poorly understood. We studied hormone-mediated behavior in the wire-tailed manakin (Pipra filica...

Social networks can vary in their organization and dynamics, with implications for ecological and evolutionary processes. Understanding the mechanisms that drive social network dynamics requires integrating individual-level biology with comparisons across multiple social networks. Testosterone is a key mediator of vertebrate social behavior and can...

In white-throated sparrows, a chromosomal rearrangement has led to alternative phenotypes that differ in sex steroid-dependent behaviors. The rearrangement has captured the genes estrogen receptor alpha and 5-alpha reductase, making these genes strong candidates for mediating the behavioral phenotypes. We report here that of the two genes, expressi...

The vertebrate basal forebrain and midbrain contain a set of interconnected nuclei that control social behavior. Conserved anatomical structures and functions of these nuclei have now been documented among fish, amphibians, reptiles, birds and mammals, and these brain regions have come to be known as the vertebrate social behavior network (SBN). Wh...

Stable social partnerships require physiological mechanisms that maintain a balance between competition and cooperation. Although the endocrine system is known to facilitate competitive behavior, we know very little about how steroid hormones affect cooperation and the stability of partnerships. Here, we examine how testosterone (T) modulates socia...

The vertebrate basal forebrain and midbrain contain a set of interconnected nuclei that control social behavior. Conserved anatomical structures and functions of these nuclei have now been documented among fish, amphibians, reptiles, birds and mammals, and these brain regions have come to be known as the vertebrate social behavior network (SBN). Wh...

Studies of birds have greatly advanced our understanding of how testosterone modulates complex phenotypes, specifically its role in mediating male reproductive and associated behaviors. Yet most of the foundational studies have been limited to northern latitude breeding species despite the fact that they represent only a small fraction of worldwide...

Obtaining baseline hormone samples can be challenging because circulating hormone levels often change rapidly due to the acute stress of capture. Although field protocols are established for accurately sampling baseline glucocorticoid concentrations, fewer studies have examined how common sampling techniques affect androgens levels. Indeed, many st...

Many species that use or require early-successional forest are of conservation concern, including a number of songbirds that have experienced long-term population declines. In this study, our initial goal was to test whether herbicide application intensity was linked to offspring sex ratio in the White-crowned Sparrow (Zonotrichia leucophrys), a sp...

Manakins of the family Pipridae are known for performing complex courtship displays at leks. These complex displays have evolved in association with strong reproductive skew, suggesting individual differences in courtship behavior exist. By measuring components of hormone regulatory networks, one may be able to elucidate the proximate mediators of...

The genome of the white-throated sparrow (Zonotrichia albicollis) contains an inversion polymorphism on chromosome 2 that is linked to predictable variation in a suite of phenotypic traits including plumage color, aggression and parental behavior. Differences in gene expression between the two color morphs, which represent the two common inversion...

Trade-offs between competitive and parental strategies often are mediated by sex steroids. The mechanisms underlying steroid signaling and metabolism may therefore serve as targets of disruptive selection that leads to alternative behavioral phenotypes. White-throated sparrows exhibit two color morphs that differ in both competitive and parental be...

The white-throated sparrow is a promising model for behavioural neuroendocrinology and genetics because behaviour and endocrine function may be linked to a chromosomal rearrangement that determines plumage colour. The notion that the two colour morphs, tan-striped (TS) and white-striped (WS), differ predictably in aggression and parenting has been...

Quantitative real-time PCR (qPCR) is becoming a popular tool for the quantification of gene expression in the brain and endocrine tissues of songbirds. Accurate analysis of qPCR data relies on the selection of appropriate reference genes for normalization, yet few papers on songbirds contain evidence of reference gene validation. Here, we evaluated...

Significance In this series of studies, we provide a rare illustration of how a chromosomal polymorphism has affected overt social behavior in a vertebrate. White-throated sparrows occur in two alternative phenotypes, or morphs, distinguished by a chromosomal rearrangement. That the morphs differ in territorial and parental behavior has been known...

Behaviors associated with breeding are seasonally modulated in a variety of species. These changes in behavior are mediated by sex steroids, levels of which likewise vary with season. The effects of androgens on behaviors associated with breeding may in turn be partly mediated by the nonapeptides vasopressin (VP) and oxytocin (OT) in mammals, and v...

Traits subject to ecologically based divergent selection that also affect nonrandom mating (i.e. 'magic traits') may hasten incipient speciation. In this study, we investigated whether nonrandom mating results from ecological divergence between swamp sparrow, Melospiza georgiana, subspecies. As a by-product of adaptive divergence in bill morphology...

The white-throated sparrow is rapidly becoming an important model in the genetics of social behavior because of a chromosomal rearrangement that segregates with a behavioral phenotype. Within a population, 50 % of individuals are heterozygous for a rearranged chromosome 2 (ZAL2(m)). These birds sing more and are more aggressive than the other 50 %,...

In species with discrete morphs exhibiting alternative behavioral strategies, individuals may vary their aggressive behavior in competitive encounters according to the phenotype of their opponent. Such aggression bias has been documented in multiple polymorphic species evolving under negative frequency-dependent selection, but it has not been well-...

Multiple parasitism of host nests by generalist brood parasites reflects the decisions of laying females and may influence the development and behavior of parasitic young. We used microsatellite and mtDNA control-region haplotype data to examine the relatedness of Brown-headed Cowbird (Molothrus ater) offspring in multiply parasitized nests sampled...

Social network analysis is an ideal quantitative tool for advancing our understanding of complex social behaviour. However, this approach is often limited by the challenges of accurately characterizing social structure and measuring network heterogeneity. Technological advances have facilitated the study of social networks, but to date, all such wo...

Black-footed ferrets (Mustela nigripes) apparently were extirpated from all native habitats by 1987, and their repatriation requires a combination of captive breeding, reintroductions, and translocations among sites. Improvements in survival rates of released ferrets have resulted from experience in quasi-natural environments during their rearing....

Male reproductive coalitions, in which males cooperate to attract females, are a rare strategy among vertebrates. While some studies have investigated ultimate aspects of these relationships, little is known about the mechanistic role that hormones play in modulating cooperative behaviours. Here, we examined male testosterone variation in a tropica...

Comparative hormone studies can reveal how physiology underlies life history variation. Here, we examined seasonal variation in plasma testosterone concentration between populations of male orange-crowned warblers (Vermivora celata) breeding in Fairbanks, Alaska (V. c. celata) and on Santa Catalina Island, California (V. c. sordida). These populati...

The adrenocortical response to perturbation varies considerably within and across avian species during breeding. Among the factors hypothesized to influence this variation is the degree of parental care expressed by an individual. To increase our understanding of the relationship between parental care and the adrenocortical response, we examined co...

In the polymorphic white-throated sparrow (Zonotrichia albicollis), tan-striped males provision nestlings at higher rates than do white-striped males. In a previous study, we found that tan-striped males had lower baseline corticosterone levels than white-striped males during the nestling stage. To determine if this variation in corticosterone infl...

Selecting the most reliable method to deliver exogenous steroids remains a problem for researchers, particularly when designing experiments on small birds. We used intraperitoneal (IP) osmotic pumps to deliver exogenous corticosterone (CORT) and RU486 in captive White-throated Sparrows. Males received implants containing either a low (LD) or modera...

Corticosterone is a multifaceted hormone that can influence physiological and behavioral adjustments to changes in energy demand. Across and within species, breeding birds show great variation in the secretion of corticosterone, the primary avian energy-regulating steroid. Two factors are hypothesized to influence variation in corticosoterone secre...