Current Projects
Phylogenomics of Hyalella in the Great Basin and beyond
Members of the genus Hyalella remain one of the most poorly understudied amphipod taxa in the Neraritc. Where most populations within the realm are thought to belong to a yet-to-be-unraveled species complex. Throughout North America, there is a great Linnean shortfall and almost nothing is known about the natural history of these organisms. In order to gauge species diversity within this genus throughout the Great Basin and beyond, I am utilizing Ultraconserved Elements (UCEs) to create a phylogeny for and test biogeographic hypotheses about, Hyalella. In addition, these data will be used to help settle the genus’ taxonomy in the United States.
UCEs are short, but highly conserved, regions of the genome that have been demonstrated to show utility in the examination of deeper phylogenetic relationships at levels above species, with typical probesets allowing the examination of 1,000+ loci simultaneously.
To execute this project, I designed a novel UCE probeset targeting peracarid crustaceans (manuscript in prep) which recovered ~3,000 unique UCE loci in-silico for members of both the Amphipoda and Isopoda. In collaboration with the U.S. Bureau of Land Management, I am in the process of analyzing over 180 populations of the genus Hyalella from across the Great Basin and locations throughout the Nearctic and Neotropical range of the genus. Analysis of these data are in their final stages; the robust dataset created by the UCEs will allow for an equally robust phylogeny to be reconstructed and from which species delimitation and estimation of distributions can be made. In addition, this phylogeny can also be utilized to make inferences on the evolutionary history of the region.
Similaer projects are planned for members of the Crangonyctidae
Above: localities for which Hyalella spp. will be analyzed utilizing UCES, coded by drainage basin.
Misc evolutionary history
Several small projects are currently in various stages of preparation, most examine the evolutionary and biogeographic history of various taxa such as Parabogidiella, Gammarus minus, and members of the Asellidae. A majority of taxa included in these analyses are sequenced for the first time and reveal interesting aspects of the natural history of both the organisms and the regions they occupy. A luxury afforded by the analysis of underrepresented groups!
One such study was published in Molecular Phylogenetics & Evolution in 20XX examining the historical biogeography of the superfamily Hyaloidea, results suggest the group was older than once thought, showed strong Gondwanan connections, and likely researched North America earlier than the Pliocene as once thought.
Right: Hypotheses of evolution proposed for members of the Hyaloidea. Results of our analysis supported a “Single Early Marine Invasion” hypothesis, likely promoted by the shallow habitats created by the breakup of Gondwana
Ohio peracarid surveys and taxonomy
Relatively little attention has been given to peracarid diversity in many regions of the United States, this is especially true in Ohio. Since 2020 I have been involved with collecting and cataloging both amphipods and isopods from Ohio and the surrounding regions. These collections so far have resulted in numerous new range records for many species, a new species of Lirceus from the Columbus metropolitan area (Samsa et al., 2024), and two new species of Crangonyx from a single locality in southeastern Ohio (in prep). These t trends not only suggest higher biodiversity than realized, but many of these taxa, such as the new Lirceus, belong to unique lineages that have implications for the region’s evolutionary history. For example, Lirceus from near Columbus were found to be more closely related to species from Alabama than to those from the rest of Ohio and Kentucky, suggesting the presence of a separate faunal assemblage in the region not observed in other freshwater invertebrates.
Above: Lirceus sp. n. collected from Delaware County, Ohio. Scale bar = 1 mm.
Other taxonomy
Whenever possible, I try to keep active with peracarid taxonomy. There is still a large number of species that need to be described from localities across the continent.
I currently have multiple projects ongoing, which are in various stages of preparation. Including a monograph describing 8 new species of Hyalella from the Chiuahuahn Desert of Texas/New Mexico; two new species of Crangonyx and two new species of Lircues from Ohio; new Hyalella from Nevada, Colorado, and Ohio; a new Caecidotea from Pennslyvania; and 4 new Stygobromus from California and Oregon.
No shortage of work to be done!
Right: A subset of Hyalella from the Chihuahuan Desert which are currently set to be included in an upcoming monograph.
Previous Projects
From 2017-2019, I worked in the Groundwater Biodiversity Lab ran by Dr. Thomas Sawicki at Florida A&M University. Here I was tasked with the examination of wide-ranging species occurring within the Floridan Aquifer (Crangonyx hobbsi and C. grandimanus)
Phylogenetic analysis of populations throughout the range of both these species, not only revealed cryptic diversity, but also unique phylogenetic structuring; where populations appeared to split near the confluence of the Suwannee and Santa Fe Rivers. This pattern was observed in several species, suggestive of a faunal break in the region.
Phylogenetic analyses of various populations of amphipods both epigean and hypogean also revealed the presence of numerous undescribed species within Florida. Species described by me during this period include: C. manubrium (Jackson County, FL), C. ephemerus/pseudoephemerus (Leon County, FL), C.apalachee (Leon County, FL), C. parhobbsi (~Northern Suwannee River), and Stygobromus doughertyensis (Jackson County, FL)
Phylogenetics / taxonomy of Florida Crangonyctidae
Above: Distributional map of Crangonyx hobbsi/parhobbsi. Note the split between species roughly corresponding with the northern Suwannee River.
Left: Variation in eye size observed within Crangonyx manubrium (b-p), a fully hypogean species, described from caves and similar habitats in Jackson County, Florida. Such variation is suggestive of relatively recent adaptation to groundwater.