{"689305":{"#nid":"689305","#data":{"type":"event","title":"PhD Defense by Nikesh Kumar ","body":[{"value":"\u003Cp\u003EIn partial fulfillment of the requirements for the degree of\u003Cbr\u003EDoctor of Philosophy in Bioinformatics\u003Cbr\u003Ein the School of Biological Sciences\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ENikesh Kumar\u003C\/strong\u003E\u0026nbsp;\u003Cbr\u003E\u003Cbr\u003EDefends his thesis:\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EStructural Variation in Adaptive Radiations: Determining the Potential Role of Large Genomic Inversions in Lake Malawi Cichlids\u0026nbsp;\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003E\u0026nbsp;\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003ETuesday April 14, 2026 at 2:30 PM\u003C\/p\u003E\u003Cp\u003EClough Undergraduate Learning Commons,\u0026nbsp;\u003Cstrong\u003ERoom 262\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EMeeting Link:\u0026nbsp;\u003Ca href=\u0022https:\/\/gatech.zoom.us\/j\/97168334383?pwd=b1htuiBwiY73VvOkw1lb7xJ5FFGp8z.1\u0022\u003ENikesh Kumar Thesis Defense | Zoom\u003C\/a\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EThesis Advisor\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EDr. Patrick T. McGrath\u003C\/p\u003E\u003Cp\u003ESchool of Biological Sciences\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EGeorgia Institute of Technology\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003ECommittee Members\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EDr. I. King Jordan\u003Cbr\u003ESchool of Biological Sciences\u003Cbr\u003E\u003Cem\u003EGeorgia Institute of Technology\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EDr. Joseaph Lachance\u003Cbr\u003ESchool of Biological Sciences\u003Cbr\u003E\u003Cem\u003EGeorgia Institute of Technology\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EDr. J. Todd Streelman\u003Cbr\u003ESchool of Biological Sciences\u003Cbr\u003E\u003Cem\u003EGeorgia Institute of Technology\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EDr. Thomas D. Kocher\u003C\/p\u003E\u003Cp\u003EDepartment of Biology\u003Cbr\u003E\u003Cem\u003EUniversity of Maryland\u003C\/em\u003E\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EAbstract\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003ELarge chromosomal inversions restructure the genome, linking together small genetic variants by suppressing recombination between inverted and non-inverted segments. Large inversions have been shown to play an important evolutionary role in local adaptation, resolution of sexual conflict, and in speciation. This thesis investigates whether large inversions could be involved in the recent adaptive radiation in Lake Malawi cichlids, where ~800 species, characterized by large amounts of sexual dimorphism and adaptation to local niches, have evolved in the past 1.2 million years. Using optical genome mapping on a discovery cohort of 12 species from Lake Malawi, we identified six large inversions that span over 12% of the genome and then validated them using new long-read genome assemblies. We genotyped these inversions in 118 species, encompassing all seven major ecogroups distributed throughout the lake. We found that the inversions are correlated with ecogroup, consistent with a role for these structural variants to facilitate the separation of the major lake lineages into specific lake habitats. Furthermore, to investigate the functional impact of inversion heterozygosity, we found that at least one of these inversions functions as an XY sex-determination system in the deep benthic species Aulonocara sp. \u2018chitande type north\u2019 Nkhata Bay, where males are heterozygous for the inversion while females are homozygous. To map the causal locus within this non-recombining region, we utilized backcrossed hybrids generated between this deep benthic species and a species lacking the chromosome 10 inversion, successfully restoring meiotic recombination across the non-inverted, male-specific Y (MSY) sex-determining region. Leveraging this mapping population, we employed quantitative trait locus (QTL) mapping to narrow the sex-determining locus within the Aulonocara MSY to a 2Mbp region. Subsequent fine-mapping using highly informative recombinant offspring further isolated the locus to a 200kb window containing three key candidate genes, including a long non-coding RNA and a histone variant that collectively implicate a novel epigenetic regulatory network. The findings presented in this dissertation conclusively demonstrate that chromosomal inversions can play significant roles in driving both local adaptation and sex chromosome evolution within adaptive radiations.\u003C\/p\u003E\u003Cp\u003E\u0026nbsp;\u003C\/p\u003E","summary":"","format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003E\u003Cstrong\u003EStructural Variation in Adaptive Radiations: Determining the Potential Role of Large Genomic Inversions in Lake Malawi Cichlids\u0026nbsp;\u003C\/strong\u003E\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Structural Variation in Adaptive Radiations: Determining the Potential Role of Large Genomic Inversions in Lake Malawi Cichlids "}],"uid":"27707","created_gmt":"2026-04-01 13:40:27","changed_gmt":"2026-04-01 13:45:56","author":"Tatianna Richardson","boilerplate_text":"","field_publication":"","field_article_url":"","field_event_time":{"event_time_start":"2026-04-14T02:30:00-04:00","event_time_end":"2026-04-14T16:30:04-04:00","event_time_end_last":"2026-04-14T16:30:04-04:00","gmt_time_start":"2026-04-14 06:30:00","gmt_time_end":"2026-04-14 20:30:04","gmt_time_end_last":"2026-04-14 20:30:04","rrule":null,"timezone":"America\/New_York"},"location":"Clough Undergraduate Learning Commons, Room 262","extras":[],"groups":[{"id":"221981","name":"Graduate Studies"}],"categories":[],"keywords":[{"id":"100811","name":"Phd Defense"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[{"id":"1788","name":"Other\/Miscellaneous"}],"invited_audience":[{"id":"78771","name":"Public"}],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[],"email":[],"slides":[],"orientation":[],"userdata":""}}}