Background and Aims The dynamics of genome evolution caused by whole genome duplications and other processes are hypothesized to shape the diversification of plants and thus contribute to the astonishing variation in species richness among the main lineages of land plants. Ferns, the second most species rich lineages of land plants are highly suitable to test this hypothesis because of several unique features that distinguish fern genomes from those of seed plants. In this study, we tested the hypothesis that genome diversity and disparity shape fern species diversity by recording several parameters related to genome size and chromosome number. Methods We conducted de novo measurement of DNA C-values across the fern phylogeny to reconstruct the phylogenetic history of the genome space occupation in ferns by integrating genomic parameters such as genome size, chromosome number, and average DNA amount per chromosome into a time-scaled phylogenetic framework. Using phylogenetic generalized least square methods, we determined correlations between chromosome number and genome size, species diversity and evolutionary rates of their transformation. Key Results The measurements of DNA C-values for 233 species more than doubled the taxon coverage from ca. 2.2% in previous studies to 5.3% of extant diversity. The dataset documented not only substantial differences in the accumulation of genomic diversity and disparity among the major lineages of ferns but also recovered support the predicted correlation between species diversity and the dynamics of genome evolution. Conclusions Our results demonstrated substantial genome disparity among different groups in ferns and supported the prediction that alterations of reproductive modes alter trends of genome evolution. Finally, we recovered evidence for a close link between the dynamics of genome evolution and species diversity in ferns for the first time.

No abstract

Introducción y objetivos: Algunas especies de helechos cheilanthoideos son caracterizados por presentar adaptaciones a hábitats xéricos. Además, presentan la particularidad de enrollar sus láminas frente a condiciones de stress hídrico. Sin embargo, al retornar las condiciones ambientales óptimas las láminas se vuelven a expandir. El objetivo de este trabajo es proporcionar información morfo-anatómica de las frondes y asociar estructuras anatómicas a estos movimientos foliares.M&M: Se estudiaron mediante microscopía óptica y electrónica de barrido la morfo-anatomía de las frondes de cuatro especies: Adiantopsis radiata, Cheilanthes glauca, Doryopteris concolor, y D. pentagona. Además, se analizó la densidad de los estomas y se calculó el índice estomático.Resultados: Se observó mesófilo homogéneo en A. radiata y D. pentagona. Cheilanthes glauca y Doryopteris concolor presentaron mesófilo heterogéneo dorsiventral. Todas las especies mostraron hojas hipoestómaticas y estomas de tipo anomocítico. El índice estomático osciló entre 9,1% (A. radiata) y 14,1% (D. concolor) y el rango de densidad de los estomas fue de 39,7 (D. pentagona) y 57,8 (D. concolor).Conclusiones: El mesófilo observado en A. radiata y D. pentagona refleja la especialización para habitar ambientes mesófilos. El mesófilo heterogéneo dorsiventral de Doryopteris concolor podría ser una ventaja para su hábito epifítico facultativo. Cheilanthes glauca tiene características xeromorfas y mesomorfas, probablemente como resultado de la disponibilidad de agua en el ambiente durante las diferentes estaciones. Se propone como hipótesis que el engrosamiento de las paredes anticlinales de las células epidérmicas podría estar involucrados en los movimientos de las láminas.

The genus Botrychium (Ophioglossaceae) is comprised of about 30 widely distributed species. Because of their small size and few, yet variable, morphological characters, many questionable taxa have been described over the years. Since its description in 1906, B. dusenii has been treated as both a distinct species and variously divided into four taxa: B. lunaria var. dusenii, B. lunaria var. typicum, B. lunaria var. antarctica, and B. ramosum var. patagonicum (B. matricariaefolium subsp. patagonicum). The aim of this study is to evaluate the validity of these taxa using spore wall sculpture, spore size, allelic composition employing enzyme electrophoresis, and morphological characters. We conclude that only one species of Botrychium occurs in southern South America and recognize this as B. dusenii, a species distinct from B. lunaria. Spore size and results of enzyme electrophoresis suggest that B. dusenii is an allotetraploid derived through hybridization between a diploid member of the B. lunaria complex and a diploid member of the B. campestre complex. We provide information about habitat, distribution, and full exsiccate citations.