Characterizing Quantitative Variation in the Glossopodia of Three Western North American Isoëtes Species (project)

Freund, Forrest D.

doi:10.7934/p2075

Cited by 3 publications

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“…Within the Isoetes crown group, no morphological features clearly divide different clades [18,42,58]. A number of features vary between taxa and clades, such as corm lobation and glossopodium structure, but these are either not widely characterised across the genus or show multiple transitions within clades [52,120]. The fossil record therefore does not allow implementing hard minimum ages for nodes within Isoetes.…”

Section: Calibration Pointsmentioning

confidence: 99%

Phylogenomics indicates the “living fossil” Isoetes diversified in the Cenozoic

et al. 2020

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The fossil record provides an invaluable insight into the temporal origins of extant lineages of organisms. However, establishing the relationships between fossils and extant lineages can be difficult in groups with low rates of morphological change over time. Molecular dating can potentially circumvent this issue by allowing distant fossils to act as calibration points, but rate variation across large evolutionary scales can bias such analyses. In this study, we apply multiple dating methods to genome-wide datasets to infer the origin of extant species of Isoetes, a group of mostly aquatic and semi-aquatic isoetalean lycopsids, which closely resemble fossil forms dating back to the Triassic. Rate variation observed in chloroplast genomes hampers accurate dating, but genome-wide nuclear markers place the origin of extant diversity within this group in the mid-Paleogene, 45-60 million years ago. Our genomic analyses coupled with a careful evaluation of the fossil record indicate that despite resembling forms from the Triassic, extant Isoetes species do not represent the remnants of an ancient and widespread group, but instead have spread around the globe in the relatively recent past.

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Section: Calibration Pointsmentioning

confidence: 99%

Phylogenomics indicates the “living fossil” Isoetes diversified in the Cenozoic

et al. 2020

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“…In these cases, small population size and genetic drift might be driving speciation. As more is learned about overlooked morphological characters, molecular phylogenies could gain additional support (Freund 2016, Bray et al 2018). The addition of unsampled (i.e., I. texana and I. mattaponica) and potentially unrecognized taxa (e.g., a unique population of I. melanospora in South Carolina, Taylor et al 1993) to this phylogeny could further enhance our understanding of the evolution of diploid Isoëtes in the southeastern USA.…”

Section: Character State Reconstructionmentioning

confidence: 99%

A Whole Chloroplast Genome Phylogeny of Diploid Species of Isoëtes (Isoëtaceae, Lycopodiophyta) in the Southeastern United States

et al. 2018

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“…Even characters once thought to be useful in delimiting natural groups within the genus, such as habitat (Engelmann, 1882) or megaspore morphology (Pfeiffer, 1922), have been found to be labile (Cox and Hickey, 1984;Taylor and Hickey, 1992;Budke et al, 2005;Hickey, 2007;Bagella et al, 2011). And while some characters such as the glossopodium (the portion of the ligule internal to the leaf) have shown some potential (Sharma and Singh, 1984;Pant et al, 2000;Shaw and Hickey, 2005;Singh et al, 2010;Freund, 2016), actually examining and interpreting these structures requires considerable histological and computational effort, making them ill-suited for field identification. This absence of consistent, dependable characters creates a paradox: the lack of reliable traits impedes the inference of phylogenies or classifications in the genus, but without a phylogeny, examining character evolution is exceptionally difficult.…”

Section: Introductionmentioning

confidence: 99%

Inferring the Evolutionary Reduction of Corm Lobation inIsoëtesusing Bayesian Model-Averaged Ancestral State Reconstruction

Freund

Freyman

Rothfels

2017

Preprint

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Inferring the evolution of characters in Isoëtes has been problematic, as these plants are morphologically conservative and yet highly variable and homoplasious within that conserved base morphology. However, molecular phylogenies have given us a valuable tool to test hypothesis of character evolution within the genus. One such hypothesis is that extant Isoëtes have undergone a morphological reduction from larger arborescent lycophyte ancestors. In this work we examine the reduction in lobe numbers on the underground trunk, or corm, over evolutionary time. Using reversible-jump MCMC and Bayesian inference, our results support the hypothesis of a directional reduction in lobe number in Isoëtes, with the best-supported model of character evolution being one of irreversible reduction. Furthermore, the most probable ancestral corm lobe number of extant Isoëtes is three, and a reduction to two lobes has occurred at least six times. From our results, we can infer that corm lobation, like many other traits in Isoëtes, shows a degree of homoplasy, yet also shows ongoing evolutionary reduction.

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Characterizing Quantitative Variation in the Glossopodia of Three Western North American Isoëtes Species (project)

Cited by 3 publications

References 0 publications

Phylogenomics indicates the “living fossil” Isoetes diversified in the Cenozoic

Phylogenomics indicates the “living fossil” Isoetes diversified in the Cenozoic

A Whole Chloroplast Genome Phylogeny of Diploid Species of Isoëtes (Isoëtaceae, Lycopodiophyta) in the Southeastern United States

Inferring the Evolutionary Reduction of Corm Lobation inIsoëtesusing Bayesian Model-Averaged Ancestral State Reconstruction

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