Characterizing Quantitative Variation in the Glossopodia of Three Western North American<i>Isoëtes</i>Species

Freund, Forrest D.

doi:10.1640/0002-8444-106.2.87.1

Cited by 6 publications

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References 40 publications

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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 diagnostic 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.…”

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Inferring the evolutionary reduction of corm lobation in Isoëtes using Bayesian model‐averaged ancestral state reconstruction

Freund

Freyman

Rothfels

2018

American J of Botany

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Inferring the evolutionary reduction of corm lobation in Isoëtes using Bayesian model‐averaged ancestral state reconstruction

Freund

Freyman

Rothfels

2018

American J of Botany

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

Freund

Freyman

Rothfels

2017

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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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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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Characterizing Quantitative Variation in the Glossopodia of Three Western North AmericanIsoëtesSpecies

Cited by 6 publications

References 40 publications

Inferring the evolutionary reduction of corm lobation in Isoëtes using Bayesian model‐averaged ancestral state reconstruction

Inferring the evolutionary reduction of corm lobation in Isoëtes using Bayesian model‐averaged ancestral state reconstruction

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

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

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