Dr. Brent M. Horton

Education:

B.S., Wildlife Biology, Colorado State University
Ph.D, Zoology, University of Maine

Areas of Specialization:

Animal Behavior, Behavioral Ecology, Ecological Physiology, Behavioral Endocrinology & Neuroendocrinology, and Ornithology.

Courses Taught:

BIOL 101 – Foundations of Biology
BIOL 211 – Concepts of Zoology
BIOL 435 – Animal Physiology
BIOL 437 – Endocrinology 
BIOL 472 – Seminars in Behavioral Ecology and Sexual Selection
BIOL 484 – Mechanisms of Animal Behavior
BIOL 486 – Behavioral Ecology*

*Summer Course at Chincoteague Bay Field Station

Research Interests:

As an integrative behavioral and physiological ecologist, I seek to understand the physiological underpinnings of the behavioral strategies that distinguish vertebrate life histories. Hormones, particularly steroids, have pleiotropic effects on physiology and behavior, and growing evidence suggests they mediate the behavioral strategies that characterize life histories. The underlying genetic bases for most hormone-mediated traits remain elusive, however, limiting our understanding of the heritable substrates on which selection can act to shape behavioral phenotypes. To address this problem, I integrate advances in neuroendocrinology and molecular genetics with traditional behavioral ecology to deconstruct the neuroendocrine and genomic architecture of behavior. My approach is to study natural models and to combine field experiments with laboratory analyses to advance our understanding of the proximate and ultimate mechanisms that shape behavioral strategies and, ultimately, life histories.

I continue to work with three avian model systems:

White-throated Sparrows (Zonotrichia albicollis) – These sparrows are a unique and powerful model for studying the neuroendocrine and genetic bases of social and reproductive behavior. They exhibit genetically based plumage polymorphism, and the two color morphs, white-striped and tan-striped, differ in aggression, parenting, and mate-seeking behaviors. Importantly, color morph and behavioral strategy segregate according to the presence or absence of a structural rearrangement of chromosome 2. This rearrangement, which captures numerous neuroendocrine genes, highlights a genomic region for a targeted investigation into the neurogenetics of behavior. For some time now, I have been working with Dr. Donna Maney (Emory University) and a team of other great colleagues and students to better understand how hormones and gene expression in the brain underlie alternative behavioral strategies in these fascinating sparrows and, more broadly, vertebrate males.

Wire-tailed Manakins (Pipra filicauda) – In this Amazonian species, males engage in stable and cooperative display partnerships to attract females, and these partnerships form the basis of a complex social network. Male reproductive success, which is highly skewed, is a function of social status and degree of social connectivity; that is, territorial males with more display partners enjoy greater reproductive success. Moreover, variation in male testosterone levels correlates with their social status. This pattern implicates testosterone as a potential mechanism underlying behavioral phenotype, social rise, and, ultimately, social network structure and fitness in male manakins. Meanwhile, the fact that territorial males with high testosterone maintain stable and cooperative display partnerships with other males is paradoxical, as testosterone is well known for promoting male-male aggression. I am working with Dr. T. Brandt Ryder (Bird Conservancy of the Rockies), Dr. Ignacio Moore (Virginia Tech), Dr. Christopher Balakrishnan (National Science Foundation), Dr. Peri Bolton (Smithsonian National History Museum), Dr. Roslyn Dakin (Carleton University), Jennifer Houtz (Cornell University) and Dr. Matthew Fuxjager (Brown University) to integrate the often too disparate fields of neuroendocrinology, genetics, bioinformatics, and social network theory to better understand the neuroendocrine and genetic bases of social behavior in vertebrates. 

Tree Swallows (Tachycineta bicolor) and Red-winged Blackbird (Agelaius phoeniceus) –  In collaboration with Millersville University faculty and students, we are investigating whether and how endocrine disrupting chemicals (EDCs) in Pennsylvania wetlands bioaccumulate from aquatic insects to insectivorous birds. As the research progresses, we aim to examine how accumulated EDCs influence the reproductive physiology and behavior of adult birds, and how the parental feeding of contaminated insects to nestlings and fledglings may influence development.

PEER-REVIEWED PUBLICATIONS (*Denotes Undergraduate Authors)

*  Houtz J.L., J.B. Receveur, J.L. Pechal, M.E. Benbow, B.M. Horton, & J.R. Wallace. In Press. Characterization of the avian postmortem gut microbiome across space and time using 16S rRNA sequencing. Forensic Science International: Animals and Environments.

Dakin R., I.T. Moore, B.M. Horton, B.J. Vernasco, & T.B. Ryder. 2021. Testosterone-mediated behaviour shapes the emergent properties of social networks. Journal of Animal Ecology 90: 131–142. (doi:10.1111/1365-2656.13305).

Horton B.M, * C.M. Michael, M.R. Prichard, & D.L. Maney. 2020. Vasoactive intestinal peptide as a mediator of the effects of a supergene on social behaviour. Proceedings of the Royal Society B 287: 20200196. (doi:10.1098/rspb.2020.0196).

Ryder T.B., R. Dakin, B.J. Vernasco, B.S. Evans, B.M. Horton, & I.T. Moore. 2020. Testosterone modulates status-specific patterns of cooperation in a social network. The American Naturalist 195(1): 82-94. (doi:10.1086/706236).

Maney D.L., J.R. Merritt, M.R. Prichard, B.M. Horton, & S.V. Yi. 2020. Inside the supergene of the bird with four sexes. Hormones & Behavior 126: 104850. (doi:10.1016/j.yhbeh.2020.104850).

Horton B.M., T.B. Ryder, I.T. Moore, &. C.N. Balakrishnan. 2020. Gene expression in the social behavior network of the wire-tailed manakin (Pipra filicauda) brain. Genes, Brain & Behavior 19: e12560. (doi: 10.1111/gbb.12560).

Vernasco B.J., B.M. Horton, I.T. Moore, & T.B. Ryder. 2020. Reduced cooperative behavior as a cost of high testosterone in a lekking passerine bird. Behavioral Ecology 31(2): 401-410. (doi:10.1093/beheco/arz201).

Grogan K.E., B.M. Horton, * Y. Hu, & D.L. Maney. 2019. A chromosomal inversion predicts the expression of sex steroid-related genes in a species with alternative behavioral phenotypes. Molecular and Cellular Endocrinology 495: 110517. (doi:10.1016/j.mce.2019.110517).

Vernasco B.J., B.M. Horton, T.B. Ryder, & I.T. Moore. 2019. Sampling baseline androgens in free-living passerines: methodological considerations and solutions. General & Comparative Endocrinology 273:202-208. (doi:10.1016/j.ygcen.2018.07.017).

Moore I.T., B.J. Vernasco, C. Escallon, T. Small, T.B. Ryder, & B.M. Horton. 2019. Tales of testosterone: advancing our understanding of environmental endocrinology through studies of neotropical birds. General and Comparative Endocrinology 273:184-191. (doi:10.1016/j.ygcen.2018.07.003).

Rivers J.W., * J.L. Houtz, M.G. Betts, & B.M. Horton. 2017. No evidence for a link between forest herbicides and offspring sex ratio in a migratory songbird using high-throughput molecular sexing. Conservation Physiology 5(1): cox054. (doi:10.1093/conphys/cox054).

Zinzow-Kramer, W.M., B.M. Horton, C.D. McKee, J.M. Michaud, G.K. Tharp, J.W. Thomas, E.M. Tuttle, S. Yi, & D.L. Maney. 2015. Genes located in a chromosomal inversion are correlated with territorial song in white-throated sparrows. Genes, Brain & Behavior 14: 641-654. (doi:10.1111/gbb.12252).

Maney, D.L., B.M. Horton, & W.M. Zinzow-Kramer. 2015. Estrogen receptor alpha as a mediator of life-history trade-offs. Integrative & Comparative Biology 55(2): 323-331. (doi:10.1093/icb/icv005).

Horton, B.M., W.H. Hudson, E.A. Ortlund, * S. Shirk, J.W. Thomas, * E.R. Young, W. Zinzow-Kramer, & D.L. Maney. 2014. Promoter polymorphism and differential expression of estrogen receptor α in a species with alternative behavioral phenotypes. Proceedings of the National Academy of Sciences 11: 1443-1448. (doi:10.1073/pnas.1317165111).

Horton, B.M., I.T. Moore, & D.L. Maney. 2014. New insights into the hormonal and behavioural correlates of polymorphism in white-throated sparrows, Zonotrichia albicollis. Animal Behaviour 93: 207-219. (doi:10.1016/j.anbehav.2014.04.015).

Zinzow-Kramer, W.M., B.M. Horton, & D.L. Maney. 2014. Evaluation of reference genes for quantitative real-time PCR in songbird brain, pituitary, and gonad. Hormones & Behavior 66: 267-275. (doi:10.1016/j.yhbeh.2014.04.011).

Grozhik, A.V., C.P. Horoszko, B.M. Horton, * Y. Hu, * D.A. Voisin, & D.L. Maney. 2014. Hormonal regulation of vasotocin receptor mRNA in a seasonally breeding songbird. Hormones & Behavior 65: 254-263. (doi:10.1016/j.yhbeh.2013.11.009).

Horton, B.M., * Y. Hu, C.L. Martin, B.P. Bunke, E. Matthews, I.T. Moore, J.W. Thomas, & D.L. Maney. 2013. Behavioral characterization of a white-throated sparrow homozygous for the ZAL2^m chromosomal rearrangement. Behavior Genetics 43(1): 60-70. (doi:10.1007/s10519-012-9574-6).

Ballentine, B., B.M. Horton, E.T. Brown, & R. Greenberg. 2013. Divergent selection on bills contributes to non-random mating between swamp sparrow subspecies. Animal Behaviour 86: 467-473. (doi:10.1016/j.anbehav.2013.06.002).

Horton, B.M., M.E. Hauber, & D.L. Maney. 2012. Morph matters: Aggression bias in a polymorphic sparrow. PLoS ONE 7(10): e48705. (doi:10.1371/journal.pone.0048705).

Ryder, T.B., B.M. Horton, M. van den Tillaart, * J. Morales, & I.T. Moore. 2012. Proximity data-loggers increase the quantity and quality of social network data. Biology Letters 8: 917-920. (doi:10.1098/rsbl.2012.0536).

Rivers, J.W., S. Young, E. Gonzalez, B.M. Horton, J. Lock, & R.C. Fleischer. 2012. High levels of relatedness between brown-headed cowbird nestmates in a heavily-parasitized host community. The Auk 129(4): 623-631. (doi:10.1525/auk.2012.11236).

Ryder, T.B., B.M. Horton, & I.T. Moore. 2011. Understanding testosterone variation in a tropical lek-breeding bird. Biology Letters 7(4): 506-509. (doi:10.1098/rsbl.2010.1219).

Biggins, D.E., J.L. Godbey, B.M. Horton, & T.M. Livieri. 2011. Movements and survival of black-footed ferrets associated with an experimental translocation in South Dakota. Journal of Mammalogy 92(4): 742-750. (doi:10.1644/10-MAMM-S-152.1).

Horton, B.M. & R.L. Holberton. 2010. Variation in baseline corticosterone and the adrenocortical response in breeding white-throated sparrows. The Auk 127(3): 540-548. (doi:10.1525/auk.2010.09096).

Horton, B.M., J.M. Yoon, C.K. Ghalambor, I.T. Moore, & T.S. Sillett. 2010. Seasonal and population variation in breeding testosterone in male orange-crowned warblers, Vermivora celata. General & Comparative Endocrinology 168: 333-339. (doi:10.1016/j.ygcen.2010.04.019).

Horton, B.M., & R.L. Holberton. 2009. Corticosterone manipulations alter morph-specific nestling provisioning behavior in male white-throated Sparrows, Zonotrichia albicollis. Hormones & Behavior 56: 510-518. (doi:10.1016/j.yhbeh.2009.09.001).

Horton, B.M., J.A. Long, & R.L. Holberton. 2007. Intraperitoneal delivery of exogenous corticosterone via osmotic pump in a passerine bird. General & Comparative Endocrinology 152: 8-13. (doi:10.1016/j.ygcen.2007.02.030).