Inferring the impacts of evolutionary history and ecological constraints on spore size and shape in the ferns

Abstract

Citation: Barrington, D. S., N. R. Patel, and M. W. Southgate. 2020. Inferring the impacts of evolutionary history and ecological constraints on spore size and shape in the ferns. Applications in Plant Sciences 8(4): e11339. PREMISE:In the ferns, cell size has been explored with spores, which are largely uniform within species, produced in abundance, and durable. However, spore size and shape have been variously defined, and the relationship of these traits to genome size has not been well established. Here, we explore the variation in fern spore size and shape by ploidy level and genome size. METHODS:Measurements of spore dimensions for two study sets of ferns, Polystichum and Adiantum, both including diploid and tetraploid taxa, provided the basis for computing estimates of shape and size as defined here. These traits were compared between and within ploidy levels and regressed with genome size estimates from flow cytometry analysis. RESULTS:All size traits were strongly correlated with genome size; the shape trait was weakly correlated. Tetraploids were larger than diploids as expected; the spores of some closely related diploid species were also significantly different in size. DISCUSSION:Researchers with access to a student-grade compound microscope can develop a valid estimate of relative genome size for ferns. These estimates provide enough resolution to infer ploidy level and explore the relationship between genome size, habitat, and physiological constraints for species within ploidy level. KEY WORDS ferns; genome size; ploidy level; spore shape; spore size; spore volume; spores. Applications in Plant Sciences 2020 8(4): e11339 Barrington et al.-Fern spores and genome size • 2 of 10

Conducting botanical research with limited resources: Low‐cost methods in the plant sciences

“…() provide a detailed protocol for meiotic chromosome counts, a technique that has been underutilized in recent years but requires minimal lab equipment, and is simple and very effective once mastered. Similarly, correlations between spore size and genome size in ferns can be used to develop estimates for relative genome size, with enough resolution to infer ploidy (Barrington et al., ), allowing evolutionary history to be explored with minimal equipment and training.…”

A dormant resource for genome size estimation in ferns: C‐value inference of the Ophioglossaceae using herbarium specimen spores

“…The spore sizes of ferns are widely used to infer ploidy (e.g., Barrington et al, 1986 , 2020 ; Shinohara et al, 2006 ; Perrie et al, 2010 ; Chang et al, 2013 ; Kuo et al, 2016 ; Patel et al, 2018 ; and references therein). Plants with two or more times the DNA content in their nuclei than other congeneric species tend to have corresponding larger cell sizes (Comai, 2005 ; Corneillie et al, 2019 ), including the sizes of their unicellular spores.…”

“…Plants with two or more times the DNA content in their nuclei than other congeneric species tend to have corresponding larger cell sizes (Comai, 2005 ; Corneillie et al, 2019 ), including the sizes of their unicellular spores. Despite this, the correlation between spore size and genome size is evidently not universal across fern lineages (Barrington et al, 2020 ); for instance, Tmesipteris elongata P. A. Dang. has a minimum spore size of 55 µm in length and 26 µm in width (with a volume of 19,458 µm 3 sensu Barrington et al, 2020 ), and a spore genome size of 74.84 pg (Perrie et al, 2010 ; Clark et al, 2016 ).…”

Biometrics of the sporangia and spores of the Parablechnum cordatum complex (Blechnaceae, Polypodiopsida)

“…Spores are a character of great importance when making taxonomic classifications in ferns (Barrington et al 1986(Barrington et al , 2020Tryon & Lugardon 1991;Tryon & Tryon 1982). Specifically, in the case of the family Blechnaceae several studies have been made concerning the spores (Melo da Silva et al 2019;Moran et al 2018;Pasarrelli et al 2010), and recently others that allow us to discriminate species and genera within this family using, in addition to the spores, the information concerning the sporangia (Molino et al 2020).…”

“…Spores have been widely used as a taxonomical character in ferns (Tryon & Lugardon 1991;Tryon & Tryon 1982). In particular, ornamentation, wall structure, size and shape of the spores are of high taxonomic value characters, since they are relatively constant for each species (Barrington et al 1986(Barrington et al , 2020Lugardon 1974;Tryon & Lugardon 1991).…”