MA Thesis and PhD Dissertation Defenses Calendar

Fall 2025

October 7th

Spenser Babb-Biernacki’s (Esselstyn Lab) PhD research investigates the diversification and evolution of host specificity in Pneumocystis, a little-studied genus of obligately parasitic fungi found in mammal lungs. She re-examines historical assumptions that Pneumocystis has arisen through strict cospeciation and one-to-one host specificity by re-analyzing existing single locus data. Her results show that neither assumption is supported, and that there are likely between 4,500 and 6,000 Pneumocystis species, despite only six having been described. She then tests cospeciation in a pair of deermouse sister species (Peromyscus) by sequencing single mitochondrial and nuclear loci, finding that both hosts share two distantly related Pneumocystis taxa. To expand available molecular data, she then designs a target capture probe set targeting thousands of ultra-conserved elements (UCEs) in Pneumocystis genomes. After testing this probe set across multiple mammal orders, she generates a resolved phylogenetic hypothesis, with divergence time estimation supporting an origin of the genus Pneumocystis contemporaneous with placental mammals. Finally, she samples Pneumocystis across the continent-wide distribution of New World rodents in the subfamily Neotominae, finding that relaxed multi-host associations are common. Her results indicate that codiversification followed by parasite evolutionary inertia, rather than strict cospeciation, best explain the phylogeny and host specificities of extant Pneumocystis.

 

October 28th 

Daniel Geldof (Chakrabarty Lab) will defend his MA Thesis Defense on October 28th at 9AM, in the public exhibit area of the LSU Museum of Natural Science.