Gerstner Scholar Profiles
Current Gerstner Scholars
2025-2027: Zoe Kulik
2024-2026: Pedro Braganca
2023-2025: Sofia Paz Sedano
2023-2024: Rene Martin
2025-2027
Dr. Zoe Kulik
Research Focus: My research as an NSF Postdoctoral Fellow (EAR-2304875) and Gerstner Scholar focuses on illuminating the developmental patterns and life history traits in the synapsid forerunners of mammals. The synapsid lineage spans over 300 million years and includes a vast array of extinct lineages with different ecologies, physiologies, and life histories. While living mammals are also very ecologically diverse, they all share a homeothermic endothermic physiology. However, there is a longstanding hypothesis that synapsids arose from an ectothermic common ancestor and achieved endothermy in the immediate ancestors of living mammals. I am interested in testing this hypothesis by analyzing the bone tissue of deeply nested synapsid groups. Bone histology is one of the best and most informative lines of evidence to understand growth rates in the fossil record and is in turn used as a proxy for physiological capacity. By comparing the bone tissue of different synapsid groups, I aim to understand when, how, or how many times mammal-like growth rates and developmental patterns evolved. This requires a comparative approach that synthesizes bone tissue from multiple lineages to robustly assess the life histories and growth rates at different evolutionary stages along the mammalian stem.
Biography: Zoe Kulik received her B.A. in Geology from Macalester College in 2016, where she and Kristi Curry Rogers worked to reconstruct titanosaur life histories. She then worked as Macalester’s paleohistology lab manager as a post-bacc. In 2023, Zoe earned her PhD from the University of Washington in Christian Sidor’s lab. Her dissertation research focused on growth trajectories, life history, and community age structure in the mammalian stem lineage. Zoe uses a combination of traditional histological techniques, advanced imaging methods such as micro-CT, and cutting-edge synchrotron tomography to unveil the developmental patterns of the fossil relatives and ancestors of mammals.
2024-2026
Dr. Pedro Braganca
Research Focus: The main goal of my postdoctoral research at the AMNH is to understand the evolution of the Congo River within the past 15 million years through the analysis of miniature Congolese Cyprinodontiform fishes (families Nothobranchiidae and Procatopodidae), popularly known as killifishes. Based on the different species and populations distribution patterns, the project aims to understand if the hypothesized low land forest refugia played a major role in the process of speciation in the system.
The Congo River basin harbors the highest freshwater fish diversity in the African continent, but little is known about the processes that shaped this mega diversity. To address this knowledge gap, combined morphological and molecular data of different species and populations of miniature killifishes belonging to the genera Congopanchax, Hylopanchax, Fenerbahce, and Aphyoplatys, all of them inhabiting similar low land forest swamps, will be assessed. Through a comparative analysis of the populational structuring seen in the different genera, it will be possible, for the first time, to identify common historical patterns in the Congo. The selection of miniature species is a critical aspect of this research given that extremely small species generally have a lower vagility and are considered to be habitat specific. Thus, the resulting genetic diversity and distribution patterns are more likely to correspond with historical events that affected the Congo River drainage and the extent of its forest cover than patterns retrieved from larger species. In the past 10 million years, the Congo experienced increased aridification and many abrupt shifts between arid and moist periods, resulting in subsequent expansions and contractions of the rainforest. Have these climatic fluctuations affected the diversity and distribution of miniature fishes in the Congo?
During my Ph.D. research a fossil calibrated multigene phylogeny for the family Procatopodidae was published, allowing a first insight into the family biogeography in which it was possible to estimate the origin of the genera Congopanchax and Hylopanchax. A similar comprehensive phylogeny is not available for the Nothobranchiidae, thus the present research project also aims to build a time calibrated phylogeny for the family, allowing the estimate of the origin dates for Fenerbahce and Aphyoplatys.
The research will be based on specimens from the AMNH fish collection and other natural history collections, as well as on specimens that will be sampled in an expedition to the Congo River basin. For the first time UCEs will be used to understand the genetic diversity within taxa belonging to these two families, and to establish the relationships within the Nothobranchiidae.
Biography: Pedro H. N. Bragança received his B.Sc. from the Federal University of Rio de Janeiro, Brazil, in 2011 and his M.Sc. from the same institution in 2014. During his master’s thesis, he studied the Amazon miniature lampeye killifish Fluviphylax resulting in the first molecular phylogeny for the genus and the description of two new species. He earned his Ph.D. in 2018 from the Museu Nacional/Federal University of Rio de Janeiro, Brazil, including a 10-month program of doctoral research at the Royal Museum for Central Africa in Tervuren, Belgium. His dissertation research focused on the systematics and biogeography of the Cyprinodontoidei fishes, with a focus on the African lampeyes (Procatopodidae). Between the end of 2019 and 2023, Pedro was a postdoctoral researcher at the South African Institute for Aquatic Biodiversity in Makhanda (former Grahamstown), South Africa.
2023-2025
Dr. Sofía Paz Sedano
Research Focus: My postdoctoral research as a Gerstner Scholar at the American Museum of Natural History focuses on investigating the molecular mechanisms and genes involved in autotomy and regeneration of tissues in Nudibranchia (Mollusca, Gastropoda), as well as the evolution of this defense method in different lineages. Nudibranchs are soft-bodied mollusks that lost the shell. However, these sea slugs have developed defensive strategies to compensate the loss of this typical gastropod defensive structure. Some species of nudibranchs can synthesize de novo or sequester through their prey bioactive compounds. Other species can sequester stinging cells from the cnidarians which they feed. Another defensive strategy is autotomy/regeneration. It has been observed that different species of nudibranchs can autotomize different parts of the body, including the mantle, or the cerata. In the most extreme cases in Heterobranchia, the species may even free the entire body. The defense mechanisms of nudibranchs have been of interest over the years, highlighting the study of bioactive compounds and the sequestration of nematocysts. However, the ability of autotomy and regeneration has received less attention. With the aim to better understand the autotomy process in nudibranchs, one of the aims of the postdoctoral research is to study the differential gene expression and gene regulatory network of autotomy/regeneration mechanisms in the Cladobranch Berghia stephanieae (Á. Valdés, 2005) through the analyses of transcriptomes. The second aim of the research is to study the origin and evolution of autotomy/regeneration in nudibranchs through ancestral state reconstruction analyses, which combines the phylogenetic relationships between species with data on their ability to autotomize different body parts.
Biography: Sofía Paz-Sedano received her B.Sc. in Biology from the Autonomous University of Madrid (Spain) in 2016 and her M.Sc. in Marine Biology, Biodiversity and Conservation from the University of La Laguna (Spain) in 2018. Her work has focused on studying the biodiversity and evolution of Nudibranchia sea slugs. For her bachelor thesis, she studied and described one species of nudibranch belonging to the genus Okenia from the Azores Archipelago, using morphological and molecular analyses. For her master thesis, she increased the number of species and molecular data, and carried out a review of Okenia species inhabiting the Mediterranean Sea through integrative taxonomic approach, including morphological, phylogenetic and species delimitation analyses. She earned her position as assistant professor in Zoology and she carried out her Ph.D from the Autonomous University of Madrid. Her dissertation research focused on the phylogenetics, diversification and biodiversity of the nudibranch family Goniodorididae, performing a world-wide review of species. Her work included morphological studies using computed microtomography, scanning electron microscopy and dissections, as well as molecular analyses by sanger sequencing of mitochondrial and nuclear markers, and ultraconserved elements.
2023-2024
Dr. Rene Martin
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.