Robbin C. Moran

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.

Phytogeographic relationships between neotropical and African-Madagascan pteridophytes

The purpose of this study is to determine the floristic affinities of pteridophytes between the neotropics and Africa-Madagascar and examine how these affinities might have arisen. We present an annotated list that contains two kinds of affinities: 1) species in common between both regions (excluding pantropical species) and 2) species pairs (or clusters of species paris) where one of the species (or infrageneric group) occurs in the Neotropics and the other in Africa and/or Madagascar. There are 114 examples on the list, of which 27 are same-species and 87 are species pairs or closely related taxa at some infrageneric level. About 13% of the African pteridoflora and 14% of the Madagascan pteridoflora show affinities with the Neotropics. To determine how these similarities might have originated, we assess three hypotheses: 1) the boreotropics hypothesis, 2) continental drift, and 3) long-distance dispersal. The boreotropics hypothesis is difficult to assess without further phylogenetic information on the groups to which the species belong. Continental drift seems to best explain one example in the geologically old family Schizaeaceae (species inAnemia subgen.Coptophyllum sect.Tomentosae). Nearly all the other examples seem best explained by long-distance dispersal because they belong to families that first appeared during the Paleocene, more than 30 million yearsafter drift had effectively separated South America and Africa. Most of the dispersal events appear to have taken place from the neotropics to Africa-Madagascar, but recent African extinctions may have obscured directionality. Species with green spores or gemmiferous gametophytes were slightly overrepresented on the list compared to pteridophytes as a whole.ResumenLos propósitos de este estudio son determinar las afinidades florísticas de pteridofitas entre el neotrópico y la región de África-Madagascar y examinar como estas han ocurrido. Se presenta una lista con anotaciones que contiene dos tipos de afinidades: 1) especies en común entre las dos regiones (omitiendo las especies pantropicales) y 2) parejas de especies (grupos de especies) donde una de las especies (o grupo infragenérico) existe en el neotrópico y la otra en África y/o Madagascar. Hay 114 ejemplos en la lista, de los cuales 27 son la misma especie y 87 son parejas o taxa cercanamente relacionadas en algun nivel infragenérico. Casi el 13% de la pteridoflora de África y 14% de la pteridoflora de Madagascar presentan afinidades al neotrópico. Para determinar como se originaron estas similaridades, se examinaron tres hipóteses: 1) la hipótesis boreotrópica, 2) deriva continental, y 3) dispersión a larga distancia. La hipótesis boreotrópica es difícil de evaluar sin suficiente información filogenética sobre los grupos a los que las especies pertenecen. La deriva continental parece explicar mejor un ejemplo en la familia geológicamente antigua Schizaeaceae (especies enAnemia subgen.Coptophyllum sect.Tomentosae). Casi todos los otros ejemplos parecen explicarse mejor por dispersión a larga distancia ya que pretenecen a familias que aparecieron por primera vez durante el Paleoceno, más de 30 millones de años antes de que deriva continental separara América del Sur y África. La mayoría de los casos de dispersión aparecen haber tomado lugar desde el neotrópico hasta África-Madagascar, pero extinciones recientes quizás han obscurecido la direcionalidad. Las especies con esporas verdes o gametofitos gemíferos están representadas con más frecuencia en nuestra lista en contraste con las pteridofitas en general.

Molecular Studies of Representative Species in the Fern Genus Elaphoglossum (Dryopteridaceae) Based on cpDNA Sequences rbcL, trnL‐F, and rps4‐trnS

Phylogenetic relationships among 48 species representing the nine sections within the fern genus Elaphoglossum were investigated using cpDNA sequence data from rbcL, trnL‐F, and rps4‐trnS. Elaphoglossum is shown to be a well‐supported, monophyletic genus containing five major clades. Mapping of morphological characters onto the molecular phylogeny reveals how scale structure, rhizome morphology, presence/absence of hydathodes and/or phyllopodia, and general growth form are important synapomorphies for sectional and subsectional classification in Elaphoglossum. The first major clade is formed by species with subulate scales and/or hydathodes. Within this clade, a monophyletic group is formed by those species possessing hydathodes, and another monophyletic group is formed by species lacking hydathodes. The second major clade is formed by species that generally have conspicuously scaly blades. The third major clade is characterized by slender, long‐creeping, two‐ranked rhizomes, small leaves (generally less than 20 cm long), and echinulate spores. The fourth clade has phyllopodia and inconspicuously scaly or glabrous blades but is separated in two subgroups, one consisting of small plants with short‐ to long‐creeping rhizomes and another of relatively larger plants with thicker, more congested rhizomes. The fifth clade consists solely of Elaphoglossum amygdalifolium, which differs from all other members of the genus by the combination of long‐creeping rhizomes, hydathodes, phyllopodia, and reddish young leaves. Hydathodes have evolved independently more than once in Elaphoglossum.

The evolution, morphology, and development of fern leaves

Leaves are lateral determinate structures formed in a predictable sequence (phyllotaxy) on the flanks of an indeterminate shoot apical meristem. The origin and evolution of leaves in vascular plants has been widely debated. Being the main conspicuous organ of nearly all vascular plants and often easy to recognize as such, it seems surprising that leaves have had multiple origins. For decades, morphologists, anatomists, paleobotanists, and systematists have contributed data to this debate. More recently, molecular genetic studies have provided insight into leaf evolution and development mainly within angiosperms and, to a lesser extent, lycophytes. There has been recent interest in extending leaf evolutionary developmental studies to other species and lineages, particularly in lycophytes and ferns. Therefore, a review of fern leaf morphology, evolution and development is timely. Here we discuss the theories of leaf evolution in ferns, morphology, and diversity of fern leaves, and experimental results of fern leaf development. We summarize what is known about the molecular genetics of fern leaf development and what future studies might tell us about the evolution of fern leaf development.

Spore Morphology in Relation to Phylogeny in the Fern Genus Elaphoglossum (Dryopteridaceae)

The perispore structure of Elaphoglossum was studied using a scanning electron microscope. Of the species examined, 119 corresponded to those used in a previously published phylogenetic analysis of the genus based on two chloroplast noncoding DNA regions, trnL‐trnF and rps4‐trnS. The spores of 102 additional species were examined for comparative purposes. Five perispore characters were scored for each species and optimized onto the previously published molecular tree. The morphology of the perispore and its character state changes are described and discussed in a phylogenetic context. Synapomorphies for major clades within the genus were identified, such as spines for the Neotropical species of sect. Squamipedia and perforations, spines, and cristae for subsect. Pachyglossa and a large subclade within sect. Setosa. This study is the largest done on perispore morphology in relation to phylogeny in a genus of ferns. Spore images of all species studied are available at http://www.plantsystematics.org.

Phylogeny and Character Evolution of the Bolbitidoid Ferns (Dryopteridaceae)

We performed a phylogenetic analysis of the traditionally recognized genera of bolbitidoid ferns (i.e., Arthrobotrya, Bolbitis, Elaphoglossum, Lomagramma, and Teratophyllum) using two noncoding chloroplast spacers: trnL‐trnF and rps4‐trnS. The sampling included 57 species, of which 55 had not been sequenced previously. The results supported the monophyly of bolbitidoid ferns and of Arthrobotrya, Elaphoglossum, Lomagramma, and Teratophyllum; however, Bolbitis was resolved as polyphyletic. A clade of eight Neotropical species currently placed in Bolbitis is sister to Elaphoglossum, not the other species of Bolbitis. We refer to this group of species as the Bolbitis nicotianifolia clade. Lomagramma (or Bolbitis) guianensis, whose generic placement has been uncertain, was found to belong to the B. nicotianifolia clade. Bolbitis s.s. was resolved sister to the rest of the bolbitidoid ferns, which are in turn divided into two clades, one consisting of Elaphoglossum and the B. nicotianifolia clade and the other of Lomagramma, Teratophyllum, and Arthrobotrya. We optimized 34 morphological characters on the resulting phylogenetic tree. The characters found to be synapomorphic for bolbitidoid ferns were ventral root insertion, elongated ventral meristeles, sterile‐fertile leaf dimorphism, acrostichoid sori, and the absence of hairs on the leaves. Other characters, such as articulate pinnae, venation patterns, laminar buds, paraphyses, and growth habit, are discussed in relation to the clades they support at different nodes on the tree. The bolbitidoid ferns show a transition series from terrestrial (Bolbitis) to hemiepiphytic (the B. nicotianifolia clade, Arthrobotrya, Lomagramma, and Teratophyllum) to epiphytic (Elaphoglossum). A sister‐species relationship between the Neotropical Bolbitis serratifolia and the African Bolbitis acrostichoides was recovered, supporting their relationship as previously postulated on the basis of morphology.

Synopsis of Mickelia, a newly recognized genus of bolbitidoid ferns (Dryopteridaceae)

Our recent molecular phylogenetic study revealed a previously unrecognized clade of six species that is sister to Elaphoglossum. Within this clade, four species are currently classified in Bolbitis, one in Lomagramma, and one in Acrostichum. For this clade, we propose the name Mickelia, with M. nicotianifolia as the type species. We also make new combinations for the species in our phylogenetic study shown to belong to Mickelia (M. bernoullii, M. guianensis, M. hemiotis, M. nicotianifolia, M. oligarchica, and M. scandens) and two other species believed to belong to the clade based on morphology (M. lindigii, M. pergamentacea). A new hybrid and two new species are also described (M. ×atrans, M. furcata, and M. pradoi). In total, Mickelia consists of ten species and one hybrid. It is entirely neotropical. We provide a key to the genera of bolbitidoid ferns and a synopsis of Mickelia that gives for each species a complete synonymy, geographical distribution, comparative discussion, and illustration.ResumoAnálises filogenéticas recentes revelaram a existência de uma clado composto por seis espécies, irmão de Elaphoglossum. Das espécies incluídas nestas análises, quatro são atualmente tratadas em Bolbitis, uma em Lomagramma, e uma em Acrostichum. A este clado propomos o nome Mickelia, com M. nicotianifolia sendo sua espécie-tipo. Neste trabalho são apresentadas as novas combinações para as espécies de Mickelia, tanto as que foram tratadas nas análises filogenéticas (M. bernoullii, M. guianensis, M. hemiotis, M. nicotianifolia, M. oligarchica e M. scandens), quanto para duas outras que são aqui incluídas com base em evidências morfológicas (M. lindigii e M. pergamentacea). Um híbrido novo e duas espécies novas são também descritos (M. ×atrans, M. furcata e M. pradoi). No total, Mickelia compreende dez espécies e um híbrido. O gênero é inteiramente neotropical, e é caracterizado pelo hábito hemiepifítico, nervuras anastomosadas, e pela ausência de gemas (essas, se presentes, surgindo próximas à junção da pina com a raque). São apresentadas uma chave para os gêneros das samambaias bolbitidoides, e uma sinopse para Mickelia contendo uma lista completa de sinônimos, dados sobre distribuição geográfica, discussões comparativas e ilustrações.

Nuclear genome size in Selaginella

Estimates of nuclear genome size for 9 Selaginella species were obtained using flow cytometry, and measurements for 7 of these species are reported for the first time. Estimates range from 0.086 to 0.112 pg per holoploid genome (84-110 Mb). The data presented here agree with the previously published flow cytometric results for S. moellendorffii. Within the 9 species sampled here, chromosome number varies from 2n = 16 to 2n = 27. Nuclear genome size appears to be strongly correlated with chromosome number (Spearmans rank correlation; p = 0.00003725). Cultivated S. moellendorffii lacks sexual reproduction--manifest by the production of abortive megasporangia. Flow cytometric data generated from a herbarium specimen of a fertile wild-collected S. moellendorffii are virtually indistinguishable from the data generated from fresh material (0.088 vs. 0.089 pg/1C). Therefore, the limited fertility observed in cultivated plants is probably not the result of abnormal chromosome number (e.g., induced by interspecific hybridization).

Monograph of the neotropical species of Lomariopsis (Lomariopsidaceae)

This work provides a key, illustrations, descriptions, and distribution maps for the 15 species of neotropicalLomariopsis. In the Neotropics, the genus occurs in southern Florida, the Antilles, and Mexico to Bolivia and southern Brazil. Two groups of species can be recognized on the basis of heteroblastic leaf series: one (the “sorbifolia group”) whose leaves become pinnate when 1–2 cm long, and another (the “japurensis group”) whose leaves become pinnate when 15–40 cm long. Three species in the Antilles are unusual because the rachis apex aborts and the distalmost lateral pinna assumes the terminal position.ResumenEste trabajo proporciona una clave, ilustraciones, descripciones, y mapas de distribución para las 15 especies neotropicales deLomariopsis. En el Neotrópico, el género se distribuye en el sur de Florida, las Antillas, y México hasta Bolivia y el sur de Brasil. Con base en las séries heteroblásticas de las hojas se consideran dos grupos de especies: el “grupo sorbifolia” cuyas hojas son pinnadas cuando alcanzan 1–2 cm de longitud; el “grupo japurensis” tiene hojas pinnadas cuando miden 15–40 cm de largo. Las tres especies de las Antillas son extrañas porque el ápice del raquis aborta y la pinna lateral más distal se torna terminal en posición.

New Combinations in Megalastrum (Dryopteridaceae)

One of Carl Christensens many important contributions to fern taxonomy was demonstrating that Dryopteris, as defined around the turn of the century, was a vast, unrelated assemblage of ferns (Christensen, 1913, 1920). He indicated this diversity by dividing Dryopteris into 11 subgenera, using characters such as pinnule arrangement, hair type, and scale type that were not widely employed or appreciated by his predecessors and contemporaries. Ever since his work on Dryopteris, the trend has been to raise Christensens subgenera to the generic rank or to treat them as subgenera in genera other than Dryopteris. In some cases, even his informal species groups have received generic status. This paper deals with one such grouping: the D. subincisa group of Dryopteris subg. Ctenitis. Nowadays, all pteridologists recognize Christensens subgenus Ctenitis as a distinct genus, Ctenitis. Within Ctenitis s.l., one of Christensens informal groups, comprising the species allied to Ctenitis protensa, was recently established as the genus Triplophylium by Holttum (1986a). He provided evidence that Triplophyllum is more closely allied to Tectaria than to Ctenitis. Another informal group, that of Dryopteris subincisa, was made a section of Ctenitis by Tindale (1965) and a genus by Holttum (1986b), as Megalastrum. We agree with Holttum that Megalastrum deserves generic status, as it is phenetically and cladistically distinct from Ctenitis. Furthermore, we are not aware of any species that is ambiguous with regard to placement in either Megalastrum or Ctenitis.