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About 25 years ago, a revolution began in evolutionary studies of seed-free vascular plants. Whereas common wisdom and laboratory-based observations had averred that minute spores and inbreeding of individual bisexual gametophytes diminished barriers to long distance migration, genetic analyses of sporophyte populations demonstrated outcrossing breeding systems that required two spores for each successful migration event. After those population-based discoveries, the processes controlling biogeographic patterns of ferns appeared to resemble those of seed plants, and vicariance took on renewed significance. More recently, data from DNA sequencing predicted that some of the most diverse extant fern families originated after the isolation of major land masses, and these new hypotheses also demanded fresh consideration of biogeographic assumptions. The Polypodiaceae yield phylogenetic insights through integration of DNA sequence analysis and biogeography. New evidence shows separate yet simultaneous radiations in the New and Old Worlds. By combining sequence data, vicariance, and a reassessment of morphological features, new family and generic boundaries are obtained. Contributors to this symposium discovered similar patterns in the systematics and biogeography of the seed-free vascular plants they studied. Although long distance migration remains an important factor in explaining fern distributions, local and recent radiations that result in species complexes are also significant in explaining fern biogeography.
A preliminary phylogenetic analysis is presented for Lomariopsis based on sequence data from the chloroplast intergenic spacer trnL-trnF. The analysis includes 27 (60%) of the approximately 45 species in the genus. A strict consensus of six most parsimonious trees supports two main clades—the Sorbifolia-group and the Japurensis-group—previously proposed based on heteroblastic leaf development. The Sorbifolia-group is entirely neotropical and includes all the Antillean species. The species in this clade had either smooth or crested spores, but the tree was ambiguous whether these spore types define two separate clades. The Japurensis-group consists of two clades, one primarily neotropical and the other entirely paleotropical. Within the neotropical clade nests a clade of two African species, which have long-spiny spores typical of the neotropical clade and unlike those found in the African-Madagascan clade. The occurrence of these two species in Africa is best explained by long-distance spore dispersal of their ancestral species from the neotropics to Africa. Within the paleotropical clade of the Japurensis-group, a clade of three African species is nested among seven species from Madagascar (all the species from that island). Within the genus as a whole, a derived character—the abortion of the rachis apex and its replacement by the distal lateral pinna assuming a terminal position—was found to have evolved separately in each of the four species with this kind of leaf apex. A scanning electron microcope study of the spores revealed five types, and a transformation series for these different types is proposed. Characters of spore morphology and heteroblastic leaf development agreed with many of the clades in the phylogenetic tree. This study represents the first phylogeny for the genus.
The Gleicheniaceae are an ancient family of ferns, with three of the six extant genera occurring in New Zealand: Dicranopteris, Gleichenia, and Sticherus. The biogeographic origins of this family in New Zealand are unknown, and the taxonomy of Gleichenia in particular is still unclear. To address aspects of these two issues, DNA sequences from the trnL-trnF locus and the rbcL gene were produced for all of the common Gleicheniaceae species in New Zealand, as well as for Gleichenia alpina from Tasmania and Sticherus cryptocarpus from Chile. Several trnL-trnF haplotypes were found amongst New Zealand G. dicarpa. One of these haplotypes was also observed in Tasmanian G. alpina, while the other New Zealand G. dicarpatrnL-trnF haplotypes were more similar to those of G. microphylla. These results suggest the taxonomy of New Zealand Gleichenia may be more complex than presently recognized. Molecular dating of the rbcL sequences with the program r8s rejected vicariant explanations for the disjunct distributions between New Zealand and elsewhere for each of Dicranopteris, Gleichenia, and Sticherus. However, the direction of the inferred long-distance dispersal was not resolved.
Located approximately 4000 km from the nearest continent, the Hawaiian Islands comprise the most isolated archipelago on Earth. This isolation has resulted in a unique flora that includes nearly 200 native ferns and lycophytes, 77% of which are endemic to the islands. Because the Hawaiian Islands are volcanic in origin, all abiotically dispersed organisms must have arrived there via the wind or the water. Fern spores are most likely dispersed through the air, and thus patterns of air movement have undoubtedly played a significant role in determining the geographic origins of the ancestors of the Hawaiian ferns. We have identified four possible climate-based or weather-based spore dispersal hypotheses that could have resulted in the movement of ancestral spores to the Hawaiian Islands: (1) the northern subtropical jetstream, moving spores from Indo-Pacific regions; (2) the trade winds, dispersing spores from Central and North America; (3) storms carrying spores from southern Mexico and/or Central America; and (4) a dispersal mechanism carrying spores from the South Pacific across the equator resulting from the combined influence of a seasonal southern shift of the Intertropical Convergence Zone (ITCZ), Hadley Cell air movement, and the trade winds. Utilizing recently published molecular phylogenetic studies of three fern genera (Dryopteris, Polystichum, and Hymenophyllum) and new analyses of three additional genera (Adenophorus, Grammitis, and Lellingeria), each of which is represented in the Hawaiian Islands by at least one endemic lineage, we reviewed the biogeographical implications for the Hawaiian taxa in light of the possible common dispersal patterns and pathways. We hypothesize that three of the five endemic Dryopteris lineages, both of the endemic Polystichum lineages, at least one endemic Hymenophyllum lineage in the Hawaiian Islands, and, perhaps, one endemic Grammitis lineage resulted from ancestral spores of each lineage dispersing to the Hawaiian Islands via the northern subtropical jetstream. Adenophorus is sister to a mostly neotropical clade, therefore, it is likely that the ancestor of the Hawaiian clade dispersed to the Hawaiian Islands via the trade winds or a storm system. The ancestor of the endemic Lellingeria lineage may have dispersed to the Hawaiian Islands from the neotropics via the trade winds or a storm system, or from the South Pacific across the equator through the combination of a seasonal southern shift of the ITCZ, Hadley Cells, and the trade winds.
Although Africa harbors low species diversity compared to the neotropics or South East Asia, the African fern flora is of interest because of its specific composition and geographic location between the neotropics and Asia. We address the question of how the evolution of the African fern flora may have been enriched by repeated input from the neotropics and Asia. For the purpose of this paper we consider three major biogeographic regions: the neotropics, Africa and Madagascar, and Asia including Malesia and Australasia. We interpret distribution data for six clades of Polypodiaceae in a molecular phylogenetic framework. We conclude that African fern taxa shared with or closely related to ones in the neotropics or Asia have been brought about by ancient and recent dispersal events with or without subsequent speciation. The African fern flora is interpreted as being composed of endemic, neotropical, and Asian elements and as being situated in a zone of overlap of typical neotropical and Asian fern floras.
A new hybrid, Micropolypodium xbradei, from Rio de Janeiro, Brazil, is described and illustrated. It shows intermediate morphology between its parents, M. setosum and Terpsichore achilleifolia, in dissection of blades and veins, and number of sori per segment. New combinations for Brazilian endemic species are presented based on this hybrid and on recent results in grammitid phylogenetics.
We describe 11 new pteridophyte species belonging to various families from Bolivia: Dennstaedtiaceae: Hypolepis scandens, Hypolepis minima; Pteridaceae: Cheilanthes glutinosa, Eriosorus angustus, E. ascendens, E. madidiensis; Tectariaceae: Tectaria jimenezii; and Woodsiaceae: Athyrium latinervatum, Diplazium bipinnatum, D. bolivianum, D. yuyoense. The following new combinations are proposed: Anemia australis, Diplazium andicola, D. andinum, and D. petiolulatum. Polystichum maximum is proposed as a new name for Polystichum giganteum.