Hybridization And Introgression In Marine Invertebrates: Population Genomics Of Phymactis Papillosa And Asterias Sea Stars

Author

• Christopher J. Dookie, CUNY City CollegeFollow

Date of Award

2026

Document Type

Thesis

Department

Biology

First Advisor

Michael J. Hickerson

Second Advisor

Ana Carnaval

Third Advisor

Shubha Govind

Keywords

hybridization, introgression, marine invertebrates, population genomics, Phymactis papillosa, Asterias rubens, Asterias forbesi, gene flow

Abstract

Hybridization and introgression are evolutionary significant processes in marine invertebrates (Sanford & Kelly,2011) yet genome-wide investigations of gene flow in these taxa remain limited relative to vertebrate systems (Marchi et al., 2021). This thesis presents genomic analyses of hybridization and introgression in two marine invertebrates occupying contrasting oceanographic settings and characterized by contrasting genomic datasets: restriction-site associated DNA sequencing (RADseq) SNP data for the eastern Pacific sea anemone Phymactis papillosa and whole genome sequencing (WGS) data for the North Atlantic sea stars Asterias rubens and Asterias forbesi. For each system, I applied coalescent-based species tree inference using CASTER (Zhang et al., 2025) and introgression analyses using Dsuite (Malinsky et al., 2021). For the Asterias sea stars system only, I applied admixture dating using linkage disequilibrium decay as implemented in DATES (Chintalapati et al., 2022), a method that requires continuous whole genome sequence data. In Phymactis papillosa, the species tree recovered a geographically coherent topology consistent with major oceanographic barriers in the eastern Pacific coast with the blue color morph representing a genetically distinct and early diverging lineage. Introgression analyses revealed multiple gene flow signals which indicated that the blue morph and the Mexico/ElSalvador population are involved in historical introgression events with neighboring lineages as well as demonstrating that the oceanographic barriers may be semipermeable (Segovia et al., 2020). In the Asterias sea stars, species tree inference recovered consistent topology under both coalescent models while introgression analyses localized gene flow between Newfoundland and United States which confirmed geographic restriction of hybridization to the North American contact zone. Admixture dating estimates that hybridization began during the early 20th century which is consistent with the period of the Grand Banks fishing industry (Giakoumis et al., 2023). The results of this thesis demonstrates that hybridization and introgression shape the genomic composition of marine invertebrate populations across diverse geographic and ecological contexts.

Recommended Citation

Dookie, Christopher J., "Hybridization And Introgression In Marine Invertebrates: Population Genomics Of Phymactis Papillosa And Asterias Sea Stars" (2026). CUNY Academic Works.
https://academicworks.cuny.edu/cc_etds_theses/1306