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Gerstner Scholar Profiles

2013-2015

Dr. Aaron Heiss

Aaron Heiss

Research Focus - My research focuses on the morphology and evolution of protists (those eukaryotes that are not also plants, animals, or fungi).  I am particularly interested in organisms from 'orphan' lineages (those without known close relatives) and those representing ancestral forms, which in most cases are unicellular, heterotrophic flagellates.

My studies in morphology have centred around the use of transmission electron microscopy (TEM).  I use serial sections from a single cell to make a computer-based model of the cytoskeleton, referring to series from additional cells for consistency.  I combine this with observations using contrast-enhanced light microscopy (LM) and scanning electron microscopy (SEM) to produce a comprehensive view of the cell’s structure.  One exciting development of this is that my models can be made into physical objects through the use of 3D printers and related technology.  Physically or virtually, these models can be compared with one another, as well as with models developed from previous research, to give an idea of the evolution of the morphology of the eukaryotic cell.

That comparison requires a solid evolutionary framework, which is unfortunately lacking in many critical cases.  Molecular phylogenies (evolutionary trees based on genetic data) have proven surprisingly dependent upon such factors as selection of gene, which organisms are included, the method used to translate genetic data into a tree, and the individual researcher’s often-subjective preparation of that data.  Rather than solid answers, the last few decades of phylogenetic research have given us a series of (usually) increasingly consistent hypotheses.  In some cases, such as the relationships amongst the major eukaryotic lineages, those hypotheses remain tentative.  One factor that remains definitely lacking is representation of the same groups that I am most interested in.  To that end, I sequence genetic data on both the small (individual gene) and large (transcriptomic) scales.  In addition to solidifying our understanding of the relationships of major lineages, the trees that I generate also yield both questions and (sometimes) answers about the evolution of critical features of the eukaryotic cell.

The data that we are able to obtain from any organism is contingent upon that organism being sampled in the first place.  Surprisingly, new organisms, representing very deeply divergent lineages, continue to be discovered on an almost-regular basis.  In some cases, organisms are rediscovered after decades of not having been reported; in others, completely new lineages are found that had not been anticipated.  I have been sampling the environment for such organisms, discovering and culturing both new and rediscovered strains, and assisting others with similar work.  This provides the raw material for my ongoing phylogenetic and morphological studies.

Biography - Aaron Heiss completed his B.S. in Biology at Portland State University in 2002.  He then worked in PSU’s Museum of Vertebrate Biology for two years, until starting graduate school.  He earned an M.Sc. in Botany from the University of British Columbia in 2006, working in the lab of Dr. Patrick Keeling, and a Ph.D. in Biology from Dalhousie University, working under Dr. Alastair Simpson.  After additional work in Dr. Simpson’s lab as a postdoctoral researcher, he was awarded a Japan Society for the Promotion of Science postdoctoral fellowship, for which he spent eight months in Japan at the University of Tsukuba.  His research at the American Museum of Natural History is an extension of his work in Japan.


Dr. Adrien Perrard

Adrien Perrard

Research Focus - I am interested in the use of the wing shape as a new marker to reconstruct relationships among social wasp species. The wing venation is a long-known marker in insect identification. Geometric morphometrics methods enable to quantify the shape of the venation using landmarks in order to detect subtle morphological differences. During my PhD I developed a method to measure the wing shape of pinned specimens from natural history collections without damaging them. I used this method to study the caste and sex dimorphism of the wing shape in hornets and the variation between populations of a single hornet species and between the different species of hornets. My results confirmed that the wing shape enables to identify species of hornets, sex, castes and isolated populations, and that this structure presents a significant phylogenetic signal, i.e. that the wing shape similarity of insect species is congruent with the phylogeny.

My Gerstner project aims at determining whether the wing shape could be a good marker for phylogenetic reconstructions. The wing shape can be measured on ancient material from Natural History collections, and the wing is one of the best structures preserved in fossil insects. Using wing shape as a phylogenetic marker could improve phylogenetic inferences of rare or extinct species for which no molecular data could be available. The use of data from geometric morphometrics in phylogenies has long been a subject of debate because of their multivariate continuous nature, but a new method was recently developed for using landmark data in phylogeny outside from the framework of regular geometric morphometrics. Using this method, I will test the efficiency of wing shape for reconstructing the phylogeny of the Vespinae.

The subfamily of social wasps Vespinae comprises hornets and yellow-jackets. However these insects are well-known due to their large colonies and feared stings, the phylogeny of this group, comprising 70 species, has been surprisingly poorly studied. During this project, I will develop a comprehensive analysis of the phylogeny of the Vespinae integrating molecular markers and traditional morphological characters. This analysis will serve as a framework for estimating the suitability of wing shapes as markers for phylogenetic reconstruction and to test the methods of integration of geometric morphometrics data in phylogenies.

Biography- Adrien Perrard graduated at the University of Toulouse, in the South of France. He studied there the biology of a new invasive hornet. He completed his master’s degree in Palaeontology, Systematics and Evolution at the University Pierre & Marie Curie (Paris). For his master thesis, he worked on the phylogeny of hornets (genus Vespa) at the University of Vermont with Kurt M. Pickett and at the American Museum of Natural History with James M. Carpenter. He did his Ph.D. between 2009 and 2012 at the Muséum National d’Histoire Naturelle in Paris under the co-direction of Claire Villemant and James M. Carpenter. Before his Gerstner appointment in October 2013, he worked on a French collection of amber fossils with André Nel at the Paris Museum as a part-time employee.


Dr. Sara Ruane

Sara Ruane

Research Focus - My research interests include many aspects of herpetology, but are particularly strong within the realm of evolutionary biology and systematics and focus extensively on snakes. My current research, working with Dr. Chris Raxworthy, is on the systematics and phylogenetics of the Malagasy Pseudoxyrhophiine snakes. Madagascar has frequently been considered an ideal model system for understanding basic evolutionary processes including diversification and the interaction between ecology and speciation. The Pseudoxyrhophiinae snakes are a striking example of a group in Madagascar showing both high species diversity and encompassing a wide range of morphologies, habitat use, and diets. This monophyletic subfamily is one lineage of the largely continental African snake radiation Lamprophiidae, which makes up >98% of the Madagascan colubroid snake assemblage. Pseudoxyrhophiinae is represented by 88 described species in 21 genera, with 18 of these genera forming the Malagasy radiation of 83 described species (Reptile Database). This group provides an opportunity to examine causes of speciation, and the ecological and morphological diversity found in these snakes is comparable with other continental radiations. However, the advantage here is that pseudoxyrhophiines are almost entirely endemic to Madagascar, with little outside influence from colonization of other snake groups.

To estimate broad patterns relating to the tempo of diversification in extant taxa and to understand basic taxonomy, it is imperative to have a phylogeny of Pseudoxyrhophiinae. However, <50% of the described species have so far been included in the broadest published molecular study. In addition, preliminary work suggests that species diversity has been greatly underestimated for these snakes, likely due to cryptic species and poor sampling. By using next generation sequencing techniques we are generating 100’s of homologous loci across all taxa in this group in order to properly estimate phylogeny and divergence times. Understanding relationships among pseudoxyrhophiines, and the timing of origin and diversification, requires a precisely estimated and dated species tree. The species richness of the Malagasy pseudoxyrhophiine radiation, coupled with their ecological diversity (arboreal, surface dwelling, fossorial, and aquatic) and high levels of regional endemism for most species make this an ideal group to explore patterns and process of species radiations, especially concerning the tempo of species diversification in relation to both morphological and ecological evolution. My most recent work is focused on screening our current tissue collection for potentially cryptic species using a handful of informative loci, as well as targeted collecting of species in Madagascar that we are missing from our dataset.

Biography - Sara received her doctorate (Ecology, Evolution, and Behavior) from the CUNY Graduate Center in November 2012. Her dissertation, entitled “Phylogenetics, Phylogeography, Historical Demography and Morphology of Milksnakes (genus Lampropeltis)”, disentangled the systematics of the species formerly known as Lampropeltis triangulum. Her research experience is primarily within evolution and systematics, with a strong focus on herpetology, especially snakes. She also has additional training in ecological research as well, having done a MS examining ecology and population demography of Blanding’s turtles. You can read more about Sara’s research at sararuane.wordpress.com.


Dr. J. Angel Soto-Centeno

Angelo Soto

Research Focus - I am fascinated by population genetics, phylogeography, distribution models, fossils, and the application of computer software to solve population level evolutionary problems. I use climate based ecological niche models and fossils to understand the changes that occurred in insular populations of bat from the late Pleistocene (ca. 20 thousand years ago) to the present and to assess how available habitat has changed with climate fluctuations. Also, I model population genetic data under a coalescent framework (i.e. projected towards the past) to explore how different climate change scenarios affected populations of bat on Caribbean Islands. Climate based ecological niche models can be projected to infer the potential distributions of organisms at different time intervals. Radiocarbon dated fossils provide the hard data of when and where different species occurred. Finally, DNA serves as a distinctive marker for each population and can give us information about evolutionary processes that occur today and in the past. For example, DNA analysis can help us understand island bat population sizes, movement of bats among islands, etc. The combined use of DNA, coalescent methods, distribution models, and fossils is very powerful and allows me to learn about the evolutionary processes that shaped island bat populations and how bats reacted to climate change in the past. In the face of current climate change trends, my research plays an important part to better understand what happens to these bats today and to be able to predict what may happen to them in the future.

Biography - Dr. J. Angel Soto-Centeno received his B.Sc. in 2000 from Interamerican University of Puerto Rico where he studied physiological ecology of bats on Puerto Rico. He earned his M.Sc. from Eastern Michigan University studying dietary ecology of nectarivorous bats on Puerto Rico in 2004. He completed his Ph.D. from University of Florida in 2013 where he researched phylogeography of multiple species of bat in the Caribbean.


2012-2014

Dr. Faysal Bibi

RGGS Bibi

Research Focus - I currently have two main avenues of research, the evolution of bovids (horned ungulates such as antelopes, oxen, goats and their relatives), and the discovery of fossils of around 7 million years in age from the United Arab Emirates.

I study the modern and fossil bovids to reconstruct evolutionary, ecological, and biogeographic histories. Bovidae is a large, diverse, and widespread clade of horned ungulates that is subject to a broad range of investigation, from evolutionary studies to conservation and agricultural sciences. The earliest fossil bovids are at least 18 million years old, and since that time the fossil record of Eurasia and Africa is rich in bovid remains.  My main focus is on bovid fossils ranging from the last 10 million years, from Ethiopia (Middle Awash, Omo), Turkey (Sivas), Kenya (Baringo), United Arab Emirates (Baynunah), and Pakistan and India (Siwaliks). My work consists of: description and taxonomic identification of specimens; comparative and phylogenetic analyses for determination of evolutionary relationships; analysis of functional morphology and ecological proxies (tooth wear, stable isotopes, etc.) for paleoecological reconstruction; and comparative biogeography for reconstruction of evolutionary dispersal patterns.

I am also co-director (with Andrew Hill of Yale University) of the Baynunah Paleontology Project. Each year, our team spends a month conducting fieldwork surveys of the region of Al Gharbia in Abu Dhabi Emirate, United Arab Emirates, to recover fossil remains from the Baynunah Formation.  These sediments preserve fossil remains of plants and animals that indicate an age of somewhere between 8 and 6 million years ago. In addition to bone and plant remains, among the Baynunah sites are also elephant trackways preserving the earliest evidence for herding behavior in this group of mammals.

My Gerstner Scholar project, Combined Morphological-Molecular Systematics of Bovidae (Mammalia: Ruminantia), willintegrate molecular and morphological character datasets to produce the most comprehensive phylogeny for Bovidae. Recent efforts to integrate living and fossil taxa into a single phylogeny using combined molecular and morphological datasets have produced encouraging results in many clades.  The resulting phylogeny of fossil and living Bovidae would be the first of its kind, providing a large and comprehensive phylogenetic framework that would be of direct relevance to biologists and paleobiologists alike. This analysis would also provide the best-calibrated chronological estimates for diversification events within this clade. The resulting data would span almost the entire Neogene (23 million years ago to present) and may be used to directly test hypotheses of diversification associated with global and regional climate and environmental changes.  The resulting phylogeny will also comprise a primary reference for conservation biologists, namely for the identification of unique clades (genera to sub-species) susceptible to perturbation and extinction. The proposed project complements concurrent AMNH-related projects such as the mammalian portion of the Assembling the Tree of Life project. 

Biography - Faysal Bibi received his Ph.D. in Geology & Geophysics from Yale University in 2009. Since then he has spent two years at the Institute de Paléoprimatologie, Paléontologie Humaine (IPHEP) in Poitiers, France, as an International Research Fellow of the N.S.F., and one year at the Museum für Naturkunde in Berlin, Germany, as a D.A.A.D.-Leibniz scholar.


Dr. Jo Wolfe

RGGS Wolfe

Research Focus - I am interested in the relationship between ontogeny (development from embryo to adult) and our understanding of phylogenetic relationships. My Ph.D. involved testing the relationships of Cambrian (500+ million year old) fossil crustacean larvae to living clades. To achieve this, I studied the morphology of each discrete ontogenetic stage (in arthropods these are separated by molt events) and coding each stage as a separate row in a cladistic matrix. Resulting phylogenetic trees placed fossil larvae on the stem lineages of important extant clades, and supported molecular estimates of divergence in the Cambrian.

My Gerstner Scholar research will expand this ontogenetic approach to transcriptomics of living crustaceans. Decapods (crabs, shrimps, lobsters, and relatives) are some of the most charismatic and economically important crustaceans. Many species undergo radical metamorphosis multiple times in their ontogeny. Transcriptomes are the set of genes expressed in a particular tissue at a particular time in ontogeny. Different genes are expected to be expressed depending on ontogenetic timing (as they play roles in development). I will sequence transcriptomes from multiple life stages (embryo, larva, adult) of each of several species to examine the influence of ontogenetic gene expression on phylogeny reconstruction.

In order to accurately link gene expression with its specific larval or adult morphology, all sequenced life stages will also be documented with high-resolution scanning electron micrographs. The morphological data I gather will also be used for the NSF-funded AVAToL project: “Next-generation phenomics for the tree of life”. My images will be test cases for developing new approaches to automate morphological character discovery and scoring. See http://www.avatol.org. 

Biography - Jo Wolfe received her H.B.Sc. from the University of Toronto in 2007, and her Ph.D. from Yale University in 2012. Her doctoral research focused on the combination of different types of datasets (fossil, phylogenomic, and developmental) for reconstructing the pattern and tempo of deep (500+ million year) divergences of pancrustacean clades.


2011-2013

Dr. Mercer Brügler

RGGS Brugler

Research Focus - Reconstructing relationships among cnidarians is complicated by extremely low rates of mitochondrial (mt) DNA sequence evolution within anthozoans (anemones, corals, zoanthids and corallimorphs). With the exception of some stony corals, anthozoans examined to date are characterized by synonymous substitution rates 50-100 times slower than most metazoans and variation is almost nonexistent at the intraspecific level. Currently applied nuclear markers are not sufficiently variable to differentiate some putative species.

Anthozoan systematists and taxonomists face a daunting challenge: in addition to slow mt sequence evolution and a lack of variable nuclear markers, simple body plans reduce the number of morphological characters available to define a species or provide phylogenetic information. Sea anemones (order Actiniaria) are among the most diverse members of the subclass Hexacorallia and are considered an emerging model system as they represent a basal eumetazoan lineage that serves as an outgroup to studies analyzing the origin and evolution of bilaterian animals. Mosaics of characters currently distinguish actiniarians, and proposed evolutionary relationships have been largely based on an absence of features. Thus, my primary focus is to search for variable, single-copy nuclear DNA markers for species-level identification. Variable markers will ultimately help determine which external / internal morphological characters are species-specific. My secondary focus is elucidating systematic relationships within, and the evolutionary history of, the order Actiniaria (1,200 species; 46 families) using 44 newly sequenced complete mitochondrial genomes (~16-18K nucleotides per individual).

To locate novel nuclear markers for reliable species-level identification and phylogenetic analysis, I am focusing on two largely Antarctic anemones: Hormathia (Hormathiidae) and Isosicyonis (Actiniidae). Markers also are being located forAiptasia and Metridium because of their broad applicability to the scientific community. I am implementing three strategies to locate markers: building a recombinant library from whole genomic DNA; constructing a complementary DNA (cDNA) library from messenger RNA (mRNA) and screening for expressed sequence tags (ESTs); and de-novo sequencing of the transcriptome utilizing a 454 ultra-high-throughput Next Generation DNA Sequencer (the complete nuclear genome ofNematostella vectensis serves as a control). Defining species and deeper phylogenetic relationships is imperative, representing a critical step in advancing knowledge and understanding of sea anemone taxonomy and systematics. 

Biography - Mercer R. Brügler is a Texas native who was born in Hurst on December 8, 1978 to Mercer L. and Donna J. Brügler. He attended the University of Miami (Florida, 1997-2001) where he earned a Bachelor of Science in Marine Biology. He then pursued a Master of Science in Marine Biology at the College of Charleston’s Grice Marine Laboratory (South Carolina, 2001-2004) and a Doctor of Philosophy in Environmental and Evolutionary Biology at the University of Louisiana at Lafayette (2004-2011).


Dr. Timothy Guiher

RGGS Guiher

Research Focus - I am interested in the evolutionary history of the subfamily Crotalinae, the venomous snakes commonly known as pitvipers. Despite recent efforts to reconstruct the phylogenetic history of this medically important group of snakes, using mtDNA, several key nodes remain unresolved, also leaving several unanswered biogeographic questions. For instance, estimates of time of dispersal into the New World vary from the Miocene to the Late Cretaceous. In addition, inter-generic relationships remain poorly resolved, making it difficult to identify patterns of dispersal into temperate and tropical environments.

Pitvipers are responsible for the majority of mortality and morbidity due to envenomation in many parts of the world. Antivenom effectiveness is reduced by substantial variation in composition among crotaline snakes. In contrast, venom proteins have received a great deal of interest from the medical community to develop treatments. Recent studies have identified venom proteins with properties suitable to the treatment of breast cancer, colon cancer, and tumor suppression. Describing the variability in venom composition at all taxonomic levels requires a phylogenetic framework. Providing a robust hypothesis of phylogenetic (evolutionary) relationships, which can be accomplished by combining extensive sampling with a large number of unlinked genetic loci. This study will explore applications of novel genomic techniques and next generation sequencing to greatly improve the sampling of loci and individuals that can efficiently be achieved for phylogenetic study. Recent efforts to sequence entire genomes for an increasing number of vertebrate taxa, including several squamate taxa, have identified a large number of potentially informative nuclear loci suitable for examining phylogenetic relationships. Taking advantage of this is limited by the cost and effort required to sequence a large number of markers for many individuals using standard Sanger sequencing. However, recently proposed sample barcoding techniques pool samples making it possible to simultaneously sequence hundreds of loci for hundreds of individuals. This study will be among the first to apply next generation sequencing to the field of phylogenetics. By combining extensive sampling with 48 nuclear loci I will provide new insight into the biogeographic history of Crotalinae and the evolution of venom proteins within this subfamily. Specific efforts will be made to elucidate when Crotalines invaded the New World and identify patterns of dispersal into temperate and tropical niches. 

Biography - Tim Guiher received his PhD from the City University of New York in 2011. His research focuses on using molecular techniques to investigate the processes that have resulted in current species diversity and distributions of snakes. In addition, Tim uses large empirical and simulated data sets to investigate the performance of statistical methods to delineate species and infer population dynamics, including changes in historical population sizes and migration rates. He has described two new venomous snakes in the US in addition to several phylogeographic lineages of non-venomous snakes. Currently, he is using next-generation sequencing techniques to compile a massive multi-locus data set to investigate the phylogenetic relationships within Crotalinae (pitvipers) and processes influencing the radiation of this group.


2010-2012

Dr. Jonah Choiniere

RGGS Choiniere

Research Focus - I am interested in the early evolution of the Coelurosauria, a clade of theropod dinosaurs closely related to birds. Although the first bird, Archaeopteryx, is known from Jurassic deposits (~150 million years old), the fossil record of contemporaneous coelurosaurs is poor. My dissertation research focused on the anatomy and systematics of new coelurosaurs that predate Archaeopteryx from the earliest Late Jurassic (~160 million years old) of China. My Gerstner Scholar research focuses on the evolution and anatomy of the Alvarezsauroidea, an enigmatic clade of theropod dinosaurs once thought to be a flightless lineage of basal birds, and the implications for understanding the non-avian dinosaur to bird transition. Alvarezsauroids are particularly fascinating because they have short, robust forelimbs, lightly-built skulls with hundreds of teeth, and long, gracile legs. Moreover, advanced alvarezsauroids share many morphological similarities with birds, including special structures of the skull, the pelvis, and the hindlimb. Recent research on alvarezsauroids shows that the lineage had evolved by the earliest Late Jurassic and that they are not as closely related to birds as previously thought. Questions remain about the phylogenetic position of alvarezsauroids within the Theropoda and about the evolution of their bird-like morphology. I am working on a detailed anatomy of alvarezsauroids from Mongolia, incorporating data from high-resolution 3D CT scans and from new, unpublished specimens. This research will clarify alvarezsauroid relationships and illuminate morphological characteristics that alvarezsauroids share with birds. 

Biography - Jonah Choiniere received his Ph.D. in Biological Sciences from the George Washington University. He studies evolution of coelurosaurian theropods, the group of meat-eating dinosaurs most closely related to birds. He has examined theropods from around the world, and his fieldwork in China, South Africa and Mongolia focuses on discovering new species of coelurosaurs and understanding dinosaur (including birds) evolution. His systematic research on theropod dinosaurs involves the use of large datasets and the application of software designed for molecular sequence alignment to questions in morphological evolution. His current research focuses on the relationships and evolution of the bizarre theropod group Alvarezsauroidea, which were previously hypothesized to be basal flightless birds.


Dr. Jose M. Padial

RGGS Padial

Research Focus - I’m interested in species diversity, both in how it originates and how we classify it. My current research focuses on the taxonomy and phylogenetic relationships of Pristimantis. This group of Neotropical frogs, with more than 400 species, is the largest genus of Terrestrial vertebrates. These frogs are characterized by having direct development—they lay eggs in moist areas and embryos undergo direct development without the typical tadpole phase so characteristic of other anurans— and include species inhabiting the major biomes and areas of the Neotropical realm (the Amazon, the Guiana Shield, the Cerrado, diverse habitats of Central America, some islands in the Caribbean, and multiple Andean ecosystems (paramos, interandean dry valleys, cloud forests, etc.). Such an ample distribution made this group a perfect candidate to study the historical processes that shape species diversity. The first step to study the origin and biogeography of a group of organisms is to reconstruct the phylogenetic relationships of its species, so that we can identify the split of ancient species lineages and relate them to changes in the geology, climate or ecological conditions of an area. My goal as Gerstner scholar is to reconstruct a robust phylogeny of Pristimantisusing molecular and morphological data. This new phylogeny will shed light on the origin of Neotropical diversity, particularly on the diversity of the eastern slopes of the Andes and western Amazonia, for which little empirical work based on new phylogenetic hypotheses has so illuminated biogeography. Other problems that will be illuminated by an improved phylogeny and biogeography are: what is the relative role of intrinsic and extrinsic factors on the process of diversification? Has diversification occurred mainly through pulses of speciation and extinction within the same biogeographic area or through vicariance or dispersal events across different biotic zones? Do highlands promote higher diversity than lowlands? Are the Andes a diversity pump that supplies lineages to the Amazon? What’s the role of ancient areas such as the Guiana Shield in the diversification of Neotropical lineages? Has been the diversification process punctuated or constant along time? And, if punctuated, which was the period that produced a largest number of lineages and why? But also, why are so many Pristimantis out there? Ultimately, the new phylogeny will give place to an improved classification of the group. Other related projects I’m involved include, an integrative approach to Amazonian species diversity—in order to estimate how many amphibian species are still undescribed there, and how the diversity of the Amazonian forests originated; and a study on the diversity and biogeography of Andean lizards of the genus Liolaemus

Biography - José M. Padial received his PhD from Granada University in 2007. For his PhD research he worked at Museo Nacional de Ciencias Naturales (Madrid), and Museo de Historial Natural Noel Kemppf Mercado (Santa Cruz, Bolivia). During his PhD he was awarded with the Ernst Mayr Travel Grant in Ecology and Systematics from Harvard University and with the Travel grant of the European program “Synthesys”. In 2008 he received the 9th R.J.H. Hintelmann Scientific Award for Zoological Systematics. After his PhD he moved to Sweden for a two years postdoc at the Evolutionary Biology Centre of Uppsala University, awarded with a Marie Curie Inter-European fellowship. Since January 2009 he is associated editor for amphibians of the international taxonomic journal Zootaxa. Every year since 2002 he conducts field expeditions to the Amazon Basin and tropical Andes to search for frogs, several of which have been described by him and collaborators as new species to science.


2009-2011

Dr. Christian Kammerer

RGGS Kammerer

Research Focus - My current research as a Gerstner Scholar explores the origin and evolution of mammals from early cynodonts, a diverse group of synapsids in the Permian-Triassic (approximately 200-300 million years ago). Although the evolution of mammals from “reptilian”-grade vertebrates (sometimes incorrectly termed “mammal-like reptiles”) is one of the best-understood major evolutionary transitions in the fossil record, many questions about the base of the mammalian tree of life remain. In particular, there continues to be debate about the phylogenetic relationships of several groups of cynodonts hypothesized to be close relatives of mammals. This research is working towards the resolution of these issues through broader taxon sampling and the introduction of new character data from cynodont skulls and postcranial skeletons, including endocranial data derived from high resolution, 3-D CT-scans. In addition to addressing cynodont phylogeny, this research is elucidating the biological underpinnings of the origin of mammals. Cynodonts underwent a “size squeeze” during their evolution: most Triassic cynodonts were roughly dog-sized, but along the main branch of mammal ancestry, average body size was reduced to shrew proportions, and mammals remained generally small-bodied throughout the Mesozoic. Through histological sectioning of cynodont long bones (limb bones), data on cynodont growth history and “paleo-genomics” are being obtained. Relative ages and growth rates can be extrapolated from bone growth rings, and because genome size is correlated with cell size in extant organisms, the volumes of lacunae (the spaces containing bone cells) in fossil bones can provide an estimator of genome size in long-extinct organisms. Together, these data will be used to assess how cynodont miniaturization occurred and the implications of this for later mammalian success. 

Biography - Christian Kammerer received his PhD in Evolutionary Biology from the University of Chicago. He primarily studies evolution in the Synapsida, one of the two major groups of amniotes and the dominant terrestrial vertebrates of the late Paleozoic and early Mesozoic eras. He has extensively examined Permo-Triassic synapsid faunas around the world and utilizes rigorous quantitative methodologies and innovative imaging technologies to address major questions of diversification and extinction in the vertebrate fossil record. His current research focuses on the early Cynodontia, the most common synapsids of the Triassic Period, and their evolution into mammals.


Dr. Cartsen Kamenz

RGGS Kamez

Research Focus - Carsten is interested in the phylogeny and evolution of Chelicerata (arthropods with chelicerae, including all arachnids). The phylogenetic position of scorpions is crucial for resolving chelicerate phylogeny and fossil scorpions are especially important in this regard. Some scientists believe the earliest scorpions were aquatic, suggesting either that the invasion of land occurred twice in the evolutionary history of chelicerates or else that arachnids are not monophyletic (sharing a single common ancestor). Fossil scorpions are also important for illuminating the basal lineages of Recent scorpions. Unfortunately, little detailed morphological work, let alone phylogenetic analysis, has been done on fossil scorpion. Carsten is critically reassessing and documenting the morphology of 75 fossil scorpions, based on a re-examination of almost 200 specimens in twelve European and North American collections, using traditional palaeontological methods and new techniques like variable pressure scanning electron microscopy, and CT-scanning (for 3D specimens with morphology hidden in the matrix). He is focusing on characters with implications for terrestrialization, namely the abdominal plates, legs, specialized sensory structures called pectines and book lungs. Preliminary results of Carsten’s work suggest that fossil scorpions were not aquatic (i.e. there was a single origin of terrestrialization among chelicerates) and confirm hypotheses that arachnids are the monophyletic sister-group of eurypterids (sea scorpions). These findings are independently supported by genomic data.  

Biography - Carsten Kamenz graduated from the Humboldt University, Berlin (HUB) in 2003. He enrolled the same year for a Ph.D. on the comparative morphology of arachnid book lungs, co-supervised by Gerhard Scholtz (HUB) and Jason Dunlop (Museum für Naturkunde, Berlin). Carsten’s dissertation research, using the latest histological and micro-tomographical methods, was aided by an EU Synthesys grant to work at the Museum National de Histoire Naturelle, Paris (2005) and an Annette Kade Fellowship to work at the American Museum of Natural History, New York (2005/2006). Carsten was awarded his Ph.D. in 2009, moving immediately thereafter to take up his current postdoctoral fellowship, working on fossil scorpions at the AMNH.

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