Jose María Gabriel y Galán

A community-derived classification for extant lycophytes and ferns

Phylogeny has long informed pteridophyte classification. As our ability to infer evolutionary trees has improved, classifications aimed at recognizing natural groups have become increasingly predictive and stable. Here, we provide a modern, comprehensive classification for lycophytes and ferns, down to the genus level, utilizing a community‐based approach. We use monophyly as the primary criterion for the recognition of taxa, but also aim to preserve existing taxa and circumscriptions that are both widely accepted and consistent with our understanding of pteridophyte phylogeny. In total, this classification treats an estimated 11 916 species in 337 genera, 51 families, 14 orders, and two classes. This classification is not intended as the final word on lycophyte and fern taxonomy, but rather a summary statement of current hypotheses, derived from the best available data and shaped by those most familiar with the plants in question. We hope that it will serve as a resource for those wanting references to the recent literature on pteridophyte phylogeny and classification, a framework for guiding future investigations, and a stimulus to further discourse.

Gametophyte Development, Sex Expression and Antheridiogen System in Pteris incompleta Cav. (Pteridaceae)

ABSTRACT The gametophytic phase of several species of Pteris has been well studied, but for others, due perhaps to their more restricted distribution, little is known. Agar and soil cultures of different spore samples of P. incompleta were established in order to analyze developmental features of its gametophytes. Gametophyte development followed the Ceratopteris pattern, but resulted in a slightly different morphology from that of other more common species of the genus. Sex expression was variable among gametophyte populations, and was affected by culture medium. An antheridiogen system was present and promoted both male precocity and dark germination. Antheridiogen response was variable among gametophyte populations. Positive antheridiogen response in interspecific gametophyte pairings suggests a common antheridiogen system in Pteris vittata and P. incompleta.

Pteridophyte spores viability

Spore viability is defined as the time that spores retain their capacity to germinate. It is a factor of primary importance in the establishment of fern species and populations in a new habitat after spore dispersal. Viability is typically maintained for a long period in pteridophytes, but there are great variations in both interspecific and intraspecific levels.

Spore morphology and ornamentation in the genus Blechnum (Blechnaceae)

Abstract A study of the spores of 64 neotropical and palaeotropical taxa of the genus Blechnum was performed using scanning electron microscopy (SEM). Two basic types of perispores were recognised: perispore smooth or only slightly ornamented (laevigate, with micro-granules or micro-lamellae, venulose and rugulate), and perispore ornamented (rugate, low reticulate, cristate-reticulate, orbiculate, and colliculate). SEM observations allow for distinguishing differences in the structure of perispores, but the character does not correlate with the ornamentation. The smooth exospore predominates among the studied species. Results suggest that perispore characters have important diagnostic value, since different combinations of ornamentation/structure were found among the studied species. Moreover, when spore characters are considered together with other morphological traits of the sporophytes and the habit of plants, ornamentation of spores becomes a useful complementary feature at the specific level. The results are discussed in light of the recent systematic studies and emphasise that any eventual subdivision of the genus Blechnum must include characters of the sporophyte as well as spore features to ensure a more robust classification than the previously proposed. The spores also show a significant affinity between Blechnum and other genera of Blechnaceae, which was also suggested by recent phylogenetic studies.

Gametophyte development and reproduction of Argyrochosma nivea (Pteridaceae)

The gametophyte of Argyroschosma nivea was studied, mainly focusing in its morphological development, and in the apogamous production of sporophytes. Some observations on the spores were also made. As far as it is known, this is the second species of the genus whose gametophytes are studied. The germination pattern followed the Vittaria type. The subsequent developmental processes followed the Ceratopteris type. Some of the gametophytes reached an adult stage with a cordate, symmetric shape, but most of them developed as irregular, lobed prothalli. The sporophyte emerged from the anterior part of the prothallus, without formation of gametangia. First, a cell became active and originated a proliferating area of small cells. From this area, long glandular hairs were formed followed by a projected conical cluster of cells. The cluster elongated into a sporophytic structure and its apex became progressively spatulate and finally trilobulate, with marginal, glandular hairs, stomata and tracheids continuously produced. This sporophyte secreted granules of white farina from its beginnings. The production of farina in the sporophyte but not in the gametophyte could help to support the idea of the segregation of this species from its traditional location in Notholaena to Argyrochosma, as farinose gametophytes seem to be a synapomorphy of the notholenoids, group that includes Notholaena but not Argyroschoma.The gametophyte of Argyroschosma nivea was studied, mainly focusing in its morphological development, and in the apogamous production of sporophytes. Some observations on the spores were also made. As far as it is known, this is the second species of the genus whose gametophytes are studied. The germination pattern followed the Vittaria type. The subsequent developmental processes followed the Ceratopteris type. Some of the gametophytes reached an adult stage with a cordate, symmetric shape, but most of them developed as irregular, lobed prothalli. The sporophyte emerged from the anterior part of the prothallus, without formation of gametangia. First, a cell became active and originated a proliferating area of small cells. From this area, long glandular hairs were formed followed by a projected conical cluster of cells. The cluster elongated into a sporophytic structure and its apex became progressively spatulate and finally trilobulate, with marginal, glandular hairs, stomata and tracheids continuously produced. This sporophyte secreted granules of white farina from its beginnings. The production of farina in the sporophyte but not in the gametophyte could help to support the idea of the segregation of this species from its traditional location in Notholaena to Argyrochosma, as farinose gametophytes seem to be a synapomorphy of the notholenoids, group that includes Notholaena but not Argyroschoma.

Gametófitos de Pleurosorus papaverifolius (Kunze) Fée (Aspleniaceae) y Cheilanthes glauca (Cav.) Mett. (Pteridaceae), dos helechos rupícolas sudamericanos

En este trabajo se estudia la germinacion de la espora, el desarrollo morfologico de los gametofitos y la expresion sexual de dos pteridofitos sudamericanos rupicolas: Pleurosorus papaverifolius (Kunze) Fee. y Cheilanthes glauca (Cav.) Mett. Las esporas mostraron una germinacion vigorosa, y se alcanzaron porcentajes relativamente altos de germinacion (>70%) en menos de tres semanas. Pleurosorus papaverifolius desarrollo una fase filamentosa de lento crecimiento, con celulas gruesas e hinchadas que daban al gametofito un aspecto algo redondeado; por el contrario, en Cheilanthes glauca esta etapa fue efimera y rapidamente se dio paso a la fase laminar. Las formas presexuales fueron cordadas en ambas especies, pero en Pleurosorus papaverifolius se desarrollaron, ademas, abundantes protalos alargados de mayor tamano. Mientras que los protalos de Cheilanthes glaucafueron desnudos, los de Pleurosorus papaverifoliuspresentaron numerosos tricomas unicelulares tanto marginales como superficiales. Ambos pteridofitos difirieron tambien en su expresion sexual, que comenzo con el desarrollo de anteridios en Pleurosorus papaverifolius y de arquegonios en Cheilanthes glauca. En Pleurosorus papaverifolius nunca se observaron gametofitos femeninos, pero si abundantes bisexuales. Cheilanthes glauca mantuvo durante largo tiempo un numero similar de gametofitos femeninos y masculinos, produciendo solamente un reducido numero de protalos bisexuales.

Gametophyte of the Andean Fern Cheilanthes pilosa Goldm. (Pteridaceae)

Abstract The gametophytic generation of Cheilanthes pilosa (Pteridaceae), including spore germination, morphological development of the gametophytes, major vegetative features and sexual expression, was studied. In C. pilosa spore germination was of the Vittaria model and the developmental pattern was intermediate between Adiantum and Ceratopteris models. Adult gametophytes were cordate and hairy, with unicellular hairs located in the margins and both the ventral and dorsal surfaces of the prothalli. Gametangia were of the normal type described for leptosporangiate ferns. In C. pilosa populations the gametophytes produced at first instance a high proportion of female gametophytes, few male gametophytes developed and most of the female gametophytes became bisexual with time. Thus, although outbreeding is possible, this species seemed to be promoting intragametophytic selfing as the major reproductive strategy.

Farina Production by Gametophytes of Argyrochosma nivea (Poir.) Windham (Pteridaceae) and its Implications for Cheilanthoid Phylogeny

Abstract Modern molecular phylogenetic studies of the Pteridaceae have recognized a well supported cheilanthoid clade that includes four major subclades: myriopteroids, pellaeoids, hemionitidoids and notholaenoids. Many of the morphological characters used in delimitation of the cheilanthoid lineages and genera appear to be the result of convergent evolution, a result of adaptation to xeric environments. Faced with the apparent lack of sporophytic synapomorphies for the cheilanthoid subclades, farina production by gametophytes has been proposed as a character of possible phylogenetic utility. All the notholaenoid species observed to date produce farina in their gametophytes, but species of the other cheilanthoid clades (pellaeoids, hemionitidoids, and myriopteroids) do not. In this work we provide the first account of farina production in the gametophyte of a non-notholaenoid: two accessions of Argyrochosma nivea from different geographical localities were found to have farina on their gametophytes, suggesting that this gametophytic character is not a synapomorphy for the notholaenoids, and may have had several independent evolutionary origins.

Gametophyte of the Andean Fern Polystichum pycnolepis (Kunze ex Klotzsch) T. Moore (Dryopteridaceae)

Abstract The gametophytic generation of Polystichum pycnolepis (Dryopteridaceae), including spore germination, morphological development of the gametophytes, major vegetative features and sexual expression, was studied. Spore germination was of the Vittaria model and the developmental pattern was of the Aspidium model. Adult gametophytes were cordate and hairy, with unicellular hairs located in the margins and the surface of the prothalli. In addition, hairs of P. pycnolepis were papillate, secretory and the marginal ones septate. Gametangia were of the normal type described for leptosporangiate ferns. The gametophytes produced at first instance a high proportion of female gametophytes. Polystichum pycnolepis formed few bisexual gametophytes with scarce antheridia. No male gametophytes for this species were detected. Thus, the species seemed to be promoting intragametophytic selfing and, to a lesser extend, intergametophytic unions between bisexuals and females.

GERMINACION DE LA ESPORA,MORFOLOGIA DEL GAMETOFITO Y EXPRESION SEXUAL DE POLYPODIUM FEUILLEI BERTERO (POLYPODIACEAE)

En este trabajo se estudia el desarrollo morfologico y la expresion sexual de los gametofitos de Polypodium feuillei. Se emplearon cultivos multisporos en agar nutritivo para sembrar esporas. En menos de tres semanas se observo germinacion vigorosa, alcanzandose porcentajes del 78%, siendo el patron de germinacion del tipo Vittaria. El gametofito de P. feuillei presenta una fase filamentosa alargada, cuyo crecimiento se prolonga durante unas dos semanas, seguida de una fase laminar. Hacia la decima semana tras la germinacion, los gametofitos alcanzan la forma cordado-alada y presentan abundantes pelos en los margenes y en la superficie abaxial de la lamina antes de la madurez. Este modelo ontogenico de desarrollo se ajusta al tipo Drynaria. En su madurez, hacia la vigesima quinta semana, P. feuillei desarrolla inicialmente protalos de sexo femenino, que adquieren mayor tamano y vigor que los masculinos. Muy pocos gametofitos exhiben condicion bisexuada.