Gerstner Scholar Profiles
2023-2025: Rene Martin
2019-2021: Chris Law
Research Focus: My postdoctoral research as a Gerstner Scholar at the American Museum of Natural History focuses on investigating a key innovation of deep-sea fishes, bioluminescence. Fishes create bioluminescent displays either intrinsically, through the innervation of light-producing photophores, or by housing symbiotic bioluminescent bacteria in light organs in their bodies. Fishes have independently evolved the ability to produce bioluminescence at least 27 times and it occurs in over 1,500 species. Bioluminescence is used in behaviors such as camouflaging, predation, and communication, and fish lineages with bioluminescent courtship displays have significantly higher rates of species accumulation compared to their non-luminous sister clades. Within these over 1,500 bioluminescent fish, there exists numerous adaptations and alterations to the light organs possessed by these species. Fishes have evolved different light-organ morphologies, and many have evolved various filters and shutters that change the color of emitted light or obscure it completely.
My work focuses on using various methods (e.g., histology, micro-CT, SEM) combined with phylogenetic comparative methods to describe and understand the evolution of light-organ morphology in a diverse group of deep-sea fishes, the lanternfishes (Myctophidae). Lanternfishes possess intrinsic bioluminescence and emit light from primary scale-associated photophores located in ventral and lateral positions on their bodies. Many species also possess additional light organs, often sexually dimorphic, on their heads and tails. My research will also focus on analyzing the light organ morphology and control of the shuttering system in a more shallow-water group of fishes, the ponyfishes (Leiognathidae). Unlike lanternfishes, ponyfishes instead have bacterially mediated bioluminescence through a symbiosis with bioluminescent bacteria housed in an esophageal light organ. The light organ morphology in many species is sexually dimorphic, being larger in males, and often-times the males of these species also possess uniquely patterned ‘windows’ that they emit light through. Their symbiotic bacteria emit light continuously, so it is important to understand how ponyfishes control how this light is emitted and shuttered.
Biography: Rene Martin received her BS and MS in Biology from St. Cloud State University in 2014 and 2017 respectively and her PhD in Ecology and Evolutionary Biology from the University of Kansas in 2022. Most of her graduate work focused on investigating the macroevolution and adaptation in deep-sea lanternfishes and blackchins (Myctophiformes). Lanternfishes are extremely abundant and are prey for a variety of organisms, playing a major role in oceanic ecosystems. Lanternfishes are also bioluminescent and are considered diverse for a mesopelagic fish lineage. This work included creating phylogenetic hypotheses of genus-level relationships within the Myctophiformes using ultraconserved elements, gene sequences, and morphological characters. Resulting trees furthered the understanding of lanternfish relationships and were integral in investigating macroevolutionary questions associated with feeding and dentition, body-shape evolution, and olfactory organs.
Research Focus: My postdoctoral research at the AMNH focuses on the systematics, taxonomy, and phenotypic evolution of a charismatic and diverse group of mammals, the tree squirrels (Sciuridae, Sciurini). My objectives include undertaking a comprehensive taxonomic review of Sciurini using an integrative approach to reconcile genomic and morphological data, and investigating phenotypic evolution and morphological disparification in the adaptive radiation of tree squirrels.
Sciurini represents a diverse radiation that originated around 14 Mya, most likely in North America, and successfully colonized the Holarctic and Neotropical regions. Tree squirrels exhibit strikingly high rates of diversification, especially in the Neotropics, where they experienced an explosive diversification after invading South America around 6 Mya. They are conspicuous inhabitants of forested ecosystems throughout their distribution, and they play important ecological roles as predators and dispersers of tree seeds. Tree squirrels are also often used as model organisms to address a wide range of ecological and evolutionary questions, both in their native ecosystems and as invasive species. However, unresolved taxonomic problems obscure many potentially important aspects of tree-squirrel research.
Until quite recently, the genetic diversity and molecular systematics of tree squirrels were poorly known, particularly regarding the Neotropical taxa. During my Ph.D. research, I proposed heretofore the most comprehensive phylogenetic hypotheses for tree squirrels based on mitogenomes and thousands of UCE loci recovered from almost all valid species of the tribe Sciurini. The phylogenomic results allowed the advancement of a preliminary and tentative nomenclatural designation for the taxa at the genus-group level. However, a detailed taxonomic investigation is still in very much needed to carefully evaluate the application of generic names, to provide taxon diagnoses and descriptions, as well as to evaluate the species-level taxonomy within genera.
Biography: Edson F. Abreu received his B.Sc. from the University of Santa Cruz do Sul, Brazil, in 2009 and his M.Sc. from the University of São Paulo, Brazil, in 2014. For his masters thesis, he studied the non-volant small mammal fauna of the southeastern Brazilian Atlantic Forest, and described a new rodent species. He earned his Ph.D. from the University of São Paulo, including a one-year program of doctoral research at the Smithsonian Institution’s Center for Conservation Genomics in 2020. His dissertation research focused on the phylogenomics, diversification, and biogeography of Neotropical squirrels (Sciurillinae and Sciurinae: Sciurini).
Research focus: My postdoctoral research focuses on why and how certain frogs attain transparency—a rare occurrence in terrestrial vertebrates. Glassfrogs are well known for their highly transparent skin and muscle tissue, through which their organs are visible. Under the supervision of my advisor Christopher Raxworthy, this comparative project aims to identify (i) the underlying specializations that balance the physical requirements for tissue transparency with the physiological demands of living cells, and (ii) the broader eco-evolutionary processes that explain these adaptations.
Biography: Jesse Delia received an MSc from East Carolina University (2011), where he was advised by Kyle Summers. He studied the social lives of Mexican glassfrogs in the understory cafetales of San Gabriel Mixtepec (Oaxaca). This work formed the foundation for his PhD thesis on the co-evolutionary dynamics of family life in glassfrogs, which spanned across the Americas. He received his PhD (2018) from Boston University under the supervision of Karen Warkentin. Prior to this fellowship, Jesse was a postdoctoral researcher in Lauren O’Connell’s lab at Stanford University, where he developed a protocol for in vivo cell labeling using non-model amphibians. He also began investigating the physiology of glassfrogs in collaboration with Carlos Taboada, Sönke Johnsen, and Junjie Yao at Duke University.
Research Focus - My current research as an NSF Postdoctoral Fellow (DBI–1906248) and Gerstner Scholar at the American Museum of Natural History focuses on the evolutionary integration of the cranial, axial, and appendicular skeleton and their contributions to mammalian body shape diversity and adaptive significance. Understanding the major patterns and adaptive significance of phenotypic variation is a central goal of evolutionary biology. In vertebrates, body shape diversity is one of the most prominent features of phenotypic variation that can lead to increased diversification, niche specialization, and innovations within a clade. However, biologists still lack a full understanding of the underlying morphological components that contribute to body shape diversity, particularly in endothermic vertebrates such as mammals. Consequently, little is known about the morphology, ecology, and evolution of mammalian body shapes as well as the underlying traits that contribute to different body plans. Therefore, I am generating the first quantitative database of mammalian body shapes using skeletal specimens. This database will enable me to document the underlying skeletal components that contribute to body shape diversity and test novel hypotheses in mammals, including the relationship between body shape and limb lengths and the influences of locomotor and dietary ecologies on the evolution of body shapes.
Biography - Chris J. Law received his B.S. from the University of California Santa Diego in 2012 and his Ph.D. from the University of California Santa Cruz in 2019 with Dr. Rita Mehta. His dissertation examined the species diversity and phenotypic disparity across Musteloidea (badgers, minks, otters, raccoons, red panda, skunks, and weasels) as well as the influences of tool use variation on individual dietary specialization on sea otters in the Monterey Bay. Top