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Spoelhof, Jonathan [1], Soltis, Douglas [2], Soltis, Pamela [3].

Evolutionary rate heterogeneity in chromosome count evolution: an application of the ‘hidden rates model’.

For over a century, chromosome count data have fueled important discoveries about plant systematics and genome evolution. An ongoing use of chromosome count data is the reconstruction of ancestral chromosome numbers within a clade of interest. These analyses often employ variations of the Mk model, which optimizes the rate (or rates) of discrete character changes (in this case, dysploidy or whole-genome duplication) along an input phylogeny. However, these analyses typically assume that rates of character evolution are homogeneous throughout the entire phylogeny, which is unlikely for large clades. In this study, we apply the hidden rates model (or hidden Markov model, which optimizes rate parameters for multiple evolutionary regimes and the transitions between them) to identify potential rate shifts in chromosomal evolution. Specifically, we evaluate its accuracy at identifying the position and number of evolutionary rate shifts in simulated phylogenies and corresponding chromosome count data sets. We then compare the results of chromosome count reconstructions under single-rate and multiple-rate regimes in the gymnosperms, which are well represented in chromosome count databases and contain clades with highly variable levels of chromosome count diversity.

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1 - University Of Florida, Florida Museum Of Natural History, Dickinson Hall, 1659 Museum Road, Gainesville, FL, 32611, United States
2 - University Of Florida, Florida Museum Of Natural History, Dickinson Hall, Gainesville, FL, 32611, United States
3 - University Of Florida, Florida Museum Of Natural History, PO Box 117800, Gainesville, FL, 32611, United States

chromosome number
Ancestral State reconstruction.

Presentation Type: Oral Paper
Session: MACROIII, Macroevolution III
Location: Virtual/Virtual
Date: Friday, July 23rd, 2021
Time: 10:45 AM(EDT)
Number: MACROIII004
Abstract ID:791
Candidate for Awards:None

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