The genomics and population genetics of salinity tolerance in the invasive hydrozoan Cordylophora caspia:
The study of invasive species can provide us with new insight into ecological and evolutionary processes by presenting “natural experiments” as species adapt to new environments and native species respond to the invaders. For cnidarians, the evolutionary transition from a marine to freshwater habitat enables them to expand their potential range. An excellent system for investigating this evolutionary transition is the invasive hydrozoan Cordylophora caspia as it can be found in both freshwater and brackish habitats. Previous studies suggest it may be a species complex comprising lineages of exclusively brackish, freshwater and euryhaline colonies. My current work addresses several aspects of the Cordylophora species complex:
Phylogenetic placement of C. caspia genotypes collected along estuaries
Fine scale population genomics to determine if salinity tolerance is a barrier to gene flow along estuaries
Detection of signatures of adaptation to different salinity regimes in the C. caspia genome
Genetic consequences of an unusual mode of colony formation in the hydrozoan Ectopleura larynx:
The genus Ectopleura has re-evolved coloniality from within the ancestrally solitary Aplanulata. Recent work by the Cartwright lab has demonstrated that Ectopleura cannot asexually bud - rather, it forms large colonies through the fusion and subsequent physiological integration of sexually produced polyps from nearby colonies. I am currently working on a project which uses a RAD-seq technique to characterize the within- and between-colony genetic diversity of E. larynx in order to understand the potential for intra-colonial genetic conflict in this unique system.
Comparative genomics of cnidarian parasites:
Myxozoans are a diverse group of microscopic parasites that infect invertebrate and vertebrate hosts. Morphological evidence (presence of structures similar to cnidarian stinging cells) has suggested that they are extremely reduced cnidarians. By contrast, Polypodium hydriforme, which is an endoparasite of acipenseriform (paddlefish and sturgeon) fish oocytes, retains many more cnidarian-like characteristics such as fully functional tentacles and digestive system.
To understand the extreme evolutionary transition to endoparasitism in the Myxozoans, we used a phylogenomic/comparative genomics approach to confirm the placement of polypodium and the myxozoans within Cnidaria, and to demonstrate that the Myxozoans (as opposed to Polypodium) have lost many important developmental gene families. This project was summarized in PNAS .