Disentangling dysploidy and diversification in Crocus (Phase 2)

• Applicant: Nomar Waminal, Ph.D.
• Subject Area: Evolution and Systematics of Plants and Fungi ; Plant Genetics and Genomics
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 559280114

Dysploidy, a change in base chromosome number resulting from chromosome fusion or fission, is an essential player in species diversification. Reproductive isolation resulting from whole-genome duplication (WGD) and dysploidy provides a platform for speciation and the formation of a new group of taxa (cladogenesis), indicating a direct link between WGD, dysploidy, and species diversification. WGD can spur bursts of repetitive elements, such as transposable elements and tandem repeats. Compared with those from other clades, related taxa forming a clade share a pattern of abundance of specific repeat families, making shared repeat bursts a diagnostic feature of cladogenesis. These repetitive elements are frequently found in chromosome fusion sites, suggesting their involvement in descending dysploidy. Moreover, the chromosome numbers of flowering plants are tightly regulated to n = 7–12 by postpolyploidization mechanisms despite several rounds of WGD, making descending dysploidy a vital process of rediploidization. Hence, several reports have presented the theoretical associations and mechanisms linking WGD, repeat bursts, dysploidy, reproductive isolation, and speciation. Nevertheless, direct empirical evidence on these mechanisms is still very limited and has focused on a few related taxa, one or a few aspect(s) of this chain of events, or holocentric chromosomes. To better understand the connection between these components in monocentric species, it is necessary to comprehensively analyze a phylogenetic group that comprises a broad number of dysploid taxa. Using the monocentric genus Crocus, this project aims to understand links between WGD, repeat bursts, dysploidy, reproductive isolation, and speciation. Specifically, I want to address the following questions: 1) Does WGD always precede repeat bursts and cladogenesis in Crocus, or can a similar species diversification pattern evolve without WGD? 2) Do some types of repeats predispose chromosomes to descending dysploidy? 3) Are certain chromosome regions more prone to dysploidy? 4) To what degree do dysploid chromosome changes act as crossing barriers? Answering these questions will reveal the complex chromosome evolution of crocuses, provide insights into the role of dysploidy in plant evolution, and establish the genus as a model for the mechanisms and regulation of dysploidy in monocentric plants.

• DFG Programme: Research Grants