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Gerstner Scholar Profiles

2017-2019

Dr. Phillip Skipwith

Phil Skipwith

Research Focus: My postdoctoral research focuses on the macroevolutionary dynamics of an ecologically and morphologically diverse group of snakes, the pseudoxyrhophiine lamprophiids of Madagascar. This is a diverse group of ~85 species in 20 genera representing a radiation endemic to Madagascar. Very little is known about the ecology and morphological diversity of this exceptional clade. What is known is that, since the late Paleogene, this clade has colonized a number of niches resulting in fossorial, terrestrial, and arboreal forms with accompanying variation in size and shape. Previous studies attempting account for morphological diversity have been largely descriptive in nature. Moreover, this clade represents the only insular snake radiation where there has been extensive in situ diversification. Until recently, phylogenies of the Malagasy pseudoxyrhophiines have been poorly supported and incongruous, compounding the attempts to address macroevolutionary dynamics. Using a new and fully resolved species-level phylogeny generated from hundreds of anchored tag loci, I will use morphology to investigate phenotypic diversification within this group. My project involves using 3D x-ray computed tomography (CT scanning) to generate 3D models of the skeleton and soft tissues for species within this clade. These data will be used to address: 1) morphological diversity across the entire radiation, both interspecifically and intraspecifically, 2) the dynamics of phenotypic diversification through time, 3) the relationship between net diversification and phenotypic diversification, 4) and the presence of determinism and convergent evolution. Lastly, I will examine if environmental heterogeneity, particularly climate, has influenced ecological and ecomorphogical diversification within pseudoxyrhophiines. Determining the relationships between speciation, phenotypic diversification, and extrinsic factors is critical to our understanding of how biodiversity is generated and maintained across long timescales. The Malagasy pseudoxyrhophiines represent an excellent system through which we can understand these complex patterns and processes and inform conservation initiatives.

Biography: Phillip L. Skipwith received his B.S. from the Richard Stockton College of NJ in 2008, his M.S. from Villanova University in 2011 under the supervision of Aaron Bauer, and his PhD from the University of California, Berkeley in 2017 under the supervision of Jim McGuire. His dissertation focused on the phylogenomics and macroevolutionary dynamics of the diverse diplodactyloid geckos of Australasia.


Dr. Benjamin Titus

Benjamin Titus

Research Focus- My research is focused on understanding how biodiversity evolves in tropical marine symbioses at the species, population, and behavioral levels. I use sea anemone symbioses that live on coral reefs as models to understand the evolutionary processes and outcomes that generate and maintain diversity in these tightly linked interactions. I have primarily focused my research program on sea anemone symbioses from the Tropical Western Atlantic and Caribbean, but for my postdoctoral work I will be focusing exclusively on the evolution of sea anemones that host clownfishes in the Indo-Pacific.

Symbiosis often confers novel abilities or characteristics in at least one partner, can lead to adaptive radiation, and contributes meaningfully to the biodiversity within ecosystems. The clownfish-sea anemone symbiosis has been a model system for understanding fundamental evolutionary and ecological processes, and is one of the most recognizable symbioses on the planet. There are 30 described species of clownfishes, which have adaptively radiated to live with sea anemones, but only 10 nominal species of host anemones. Why have the host anemones not undergone a radiation similar to the clownfishes? Given the co-dependent nature of the mutualism, their broad geographic and ecological distribution, extensive phenotypic variation, and that all 10 host species are only described morphologically, I hypothesize that there is undescribed cryptic species-level diversity within the host anemones.

Using high-throughput sequencing (i.e. RADseq, Ultra-conserved elements), molecular species delimitation, and a comparative phylogeographic framework, I will test allopatric and ecological speciation hypotheses to search for cryptic species and reconstruct the evolutionary histories of the two most common sea anemone host species from the tropical Indo-West Pacific (IWP) oceans: Entacmaea quadricolor and Heteractis crispa. A genomic perspective is likely to be critical for understanding sea anemone diversity given the inherent challenges with classic morphological studies in this group. Ultimately, the existence of undescribed cryptic anemone host species has the potential to re-write much of our understanding of this symbiosis and impact the evolutionary, ecological, and behavioral theory that has been generated from the study of these charismatic relationships. This work will also have important conservation implications as these species are among the most heavily collected species in the ornamental aquarium trade.

Biography: Benjamin Titus received his BSc in Ecology from Otterbein University in 2008, his MSc in Marine Biology from Auburn University in 2011, and his PhD from the Dept. of Evolution and Ecology from The Ohio State University. For his doctoral work he studied the comparative phylogeography of sea anemone symbioses on coral reefs in the Tropical Western Atlantic and was advised by Meg Daly.


2016-2018

Dr. Federico Lopez-Osorio

Federico Lopez

Research Focus – I study the evolutionary relationships and molecular basis of social behavior in wasps. Specifically, I focus on the subfamily Vespinae (yellowjackets and hornets). These wasps live in colonies usually including a single reproductive queen, and hundreds to thousands of sterile workers that raise the queen's offspring. Worker and queen castes in advanced societies of yellowjackets and hornets can be morphologically different and, unlike groups of primitively social wasps, individuals cannot switch between castes as adults. The field of sociogenomics aims to understand the origin of social behavior in molecular terms. The Vespinae are particularly interesting for comparative studies in sociogenomics because its close relatives in the family Vespidae exhibit a full range of social phenotypes, from solitary to primitively social. Moreover, the Vespinae include socially parasitic species, which have secondarily lost the worker caste and rely on parental care from workers of host species. Therefore, social parasites may allow the identification of changes in genetic architecture associated with the loss of free-living traits, such as maternal care and nest founding, or the gain of parasitic behavior.

For my research as a Gerstner Scholar, I will address three objectives. First, I will augment existing transcriptomic data, identify single-copy genes, and conduct a phylogenomic analysis of vespine wasps. Second, I will use the inferred phylogeny to search for evidence of positive selection, and I will test the ‘novel’ genes hypothesis, which states that sociality is the product of the evolution of genes lacking detectable sequence similarity to known genes. Lastly, I will characterize the transcriptomes of socially parasitic species and test for the predicted loss (or lack of expression) of genes associated with maternal care.

Biography - Federico Lopez-Osorio received his B.Sc. from the Universidad Industrial de Santander in Colombia in 2009, and completed his Ph.D. in 2016 at the University of Vermont, where Dr. Kurt M. Pickett and Dr. Ingi Agnarsson were his advisors. In his doctoral studies, he focused on molecular phylogenetics and comparative transcriptomics of yellowjackets and hornets.


Dr. Edward A. Myers

Ed Myers

Research Focus – My postdoctoral research is focused on understanding variation in rattlesnake venom. Viperids, the family of snakes that includes rattlesnakes (Crotalus and Sistrurus), have venoms that are largely characterized as hemotoxic or hemorrhagic. However, a number of rattlesnake species and populations posses a potent neurotoxin. Despite these species being widespread within North America and being of medical importance, how these venoms have evolved is still unresolved. Recent studies have suggested that neurotoxic venoms are shared between rattlesnake species or populations because of past hybridization events (e.g. Zancolli et al. 2016 and Rokyta et al. 2015). However, other studies have concluded that the ancestor to all rattlesnakes possessed the genes responsible for these neurotoxins, and therefore species that lack this component in their venom have lost these genes at some point during their evolutionary history. My work will focus on addressing these competing hypotheses. In order to do so I will be generating RNA-seq data from venom glands and designing a set of DNA-probes to sequence venom genes across Crotalus. Ultimately this work will address how many times neurotoxin genes have evolved and whether hybridization plays a large role in the distribution of this trait across the rattlesnake phylogeny, which may contribute to our understanding of venom evolution in other snake groups as well as trait evolution in general.

In addition to the rattlesnake work, I will continue to work on population genomics and species delimitation in a number of North American snake taxa. This work seeks to address the mechanisms of speciation, while quantifying biodiversity within the US and Mexico. For example, collaborators and I are generating a genomic data set for the genus Pantherophis (rat snakes and corn snakes) to test species boundaries and to understand color pattern evolution in snakes.

Biography - Edward A. Myers received his B.Sc. in Zoology from Washington State University in 2009 and Ph.D. from the City University of New York in Biology in 2016, under the supervision of Dr. Frank Burbrink. His dissertation focused on comparative population genomics and ecological speciation of codistributed snakes across the desert southwest of North America.


Dr. Lu Yao

Lu Yao

Research Focus – My research interests thus far have utilized phylogeographic analysis and phylogenetic comparative methods to answer a number of questions concerning the evolution of mammals on islands. For my postdoctoral work, I will be expanding on this research by studying gibbon evolution through a combination of genetics and morphology to better understand the intraspecific variation and level of hybridization within this highly endangered family of primates in Southeast Asia. 

Gibbons (Hylobatidae) are relatively more speciose compared to other apes. Although some species are relatively well known, so far no attempts have been made to sample widely within each gibbon species to understand intraspecific variation and hybridization. My research is designed to use a combination of next generation sequencing techniques with morphometric analyses of wild gibbon specimens housed in museum collections around the world, including the extensive collections at AMNH, to expand knowledge about gibbon phylogeography, molecular evolution, and morphology at the population level. I will generate mitogenome, exome and single nucleotide polymorphism (SNP) data for a large selection of gibbon individuals across as many species as possible. With these data, I will be able to reconstruct a well-resolved intraspecific phylogeny, recognize hybridization events that may have occurred, and identify specific genes that experienced positive selection in different lineages. In addition to the genetic data, I am also collecting 3D morphological data from extant museum specimens along with alleged Hylobatidae fossils in order to analyze size and morphological variation between and within extant and fossil species. With this combination of genetic and morphological data, I intend to explore and illuminate the importance of intraspecific-level analyses, particularly in this group of understudied primates.

Biography - Lu Yao received her B.A. degree in 2011 from Northwestern University in the Integrated Science Program, Anthropology, and Biology. For her doctoral work, she was advised by Robert D. Martin and Corrie S. Moreau and studied the evolution of mammals on islands with a focus on long-tailed macaques. She received her Ph.D in 2016 from the Committee on Evolutionary Biology at University of Chicago.