High resilience of Pacific Island forests to a category- 5 cyclone.

Assessing how forests respond to, and recuperate from, cyclones is critical to understanding forest dynamics and planning for the impacts of climate change. Projected increases in the intensity and frequency of severe cyclones can threaten both forests and forest-dependent communities. The Pacific Islands are subject to frequent low-intensity cyclones, but there is little information on the effects of high intensity cyclones, or on how forest stewardship practices may affect outcomes. We assess the resistance and resilience of forests in three community-stewarded sites on the island of Tanna, Vanuatu, to the wind-related effects of 2015 Category-5 Cyclone Pam, one of the most intense cyclones to make landfall globally. Drawing on transect data established pre-and post-cyclone, we (1) test whether windspeed and tree structural traits predict survival and damage intensity, and whether this varies across sites; (2) assess post-cyclone regeneration of canopy, ground cover, seedlings, and saplings, and how community composition shifts over time and across sites. In sites that sustained a direct hit, 88 % of trees were defoliated, 34 % sustained severe damage, and immediate mortality was 13 %. Initial mortality, but not severe damage, was lower in areas that received an indirect hit and had lower windspeed. Larger trees and those with lighter wood had a higher probability of uprooting and snapping, respectively. Canopy and ground cover regenerated within three years and seedling and sapling regeneration was widespread across life histories, from pioneer to mature forest species. Three species of non-native vines recruited post-cyclone but within 5 years had largely declined or disappeared with canopy closure. Tanna's historical cyclone frequency, combined with customary stewardship practices that actively maintain a diversity of species and multiplicity of regeneration pathways, are likely responsible for the island's resistance and resilience to an intense tropical cyclone.

Reticulate evolution in the Pteris fauriei group (Pteridaceae).

The Pteris fauriei group (Pteridaceae) has a wide distribution in Eastern Asia and includes 18 species with similar but varied morphology. We collected more than 300 specimens of the P. fauriei group and determined ploidy by flow cytometry and inferred phylogenies by molecular analyses of chloroplast and nuclear DNA markers. Our results reveal a complicated reticulate evolution, consisting of seven parental taxa and 58 hybrids. The large number of hybrid taxa have added significant morphological complexity to the group leading to difficult taxonomic issues. The hybrids generally had broader ranges and more populations than their parental taxa. Genetic combination of different pairs of parental species created divergent phenotypes of hybrids, exhibited by both morphological characteristics and ecological fidelities. Niche novelty could facilitate hybrid speciation. Apogamy is common in this group and potentially contributes to the sustainability of the whole group. We propose that frequent hybridizations among members of the P. fauriei group generate and maintain genetic diversity, via novel genetic combinations, niche differentiation, and apogamy.

Once more unto the breach, dear friends: Resolving the origins and relationships of the Pellaea wrightiana hybrid complex.

PREMISE: The taxonomic status of Wright's cliff brake fern, Pellaea wrightiana, has been in dispute ever since it was first described by Hooker in 1858. Previously published evidence suggested that this "taxon" may represent a polyploid complex rather than a single discrete species, a hypothesis tested here using a multifaceted analytical approach. METHODS: Data derived from cytogenetics, spore analyses, leaf morphometrics, enzyme electrophoresis, and phylogenetic analyses of plastid and nuclear DNA sequences are used to elucidate the origin, relationships, and taxonomic circumscription of P. wrightiana. RESULTS: Plants traditionally assigned to this taxon represent three distinct polyploids. The most widespread, P. wrightiana, is a fertile allotetraploid that arose through hybridization between two divergent diploid species, P. truncata and P. ternifolia. Sterile triploids commonly identified as P. wrightiana, were found to be backcross hybrids between this fertile tetraploid and diploid P. truncata. Relatively common across Arizona and New Mexico, they are here assigned to P. ×wagneri hyb. nov. In addition, occasional sterile tetraploid plants assigned to P. wrightiana are shown here to be hybrids between the fertile allotetraploid and the tetraploid P. ternifolia subsp. arizonica. These tetraploid hybrids originated independently in two regions of parental sympatry (southern Arizona and west Texas) and are here assigned to P. ×gooddingii hyb. nov. CONCLUSIONS: Weaving together data from a diversity of taxonomic approaches, we show that plants identified as P. wrightiana represent three morphologically distinguishable polyploids that have arisen through repeated hybridization events involving the divergent sexual taxa P. ternifolia and P. truncata.

Morphological characterization of infra-generic lineages in Deparia (Athyriaceae: Polypodiales).

Deparia, including the previously recognized genera Lunathyrium, Dryoathyrium (=Parathyrium), Athyriopsis, Triblemma, and Dictyodroma, is a fern genus comprising about 70 species in Athyriaceae. In this study, we inferred a robust Deparia phylogeny based on a comprehensive taxon sampling (~81% of species) that captures the morphological diversity displayed in the genus. All Deparia species formed a highly supported monophyletic group. Within Deparia, seven major clades were identified, and most of them were characterized by inferring synapomorphies using 14 morphological characters including leaf architecture, petiole base, rhizome type, soral characters, spore perine, and leaf indument. These results provided the morphological basis for an infra-generic taxonomic revision of Deparia.

Madagascar sheds new light on the molecular systematics and biogeography of grammitid ferns: New unexpected lineages and numerous long-distance dispersal events.

Based on a worldwide phylogenetic framework filling the taxonomic gap of Madagascar and surrounding islands of the Western Indian Ocean (WIO), we revisited the systematics of grammitid fern species (Polypodiaceae). We also investigated the biogeographic origin of the extant diversity in Madagascar and estimated the relative influence of vicariance, long-distance dispersals (LDD) and in situ diversification. Phylogenetic inferences were based on five plastid DNA regions (atpB, rbcL, rps4-trnS, trnG-trnR, trnL-trnF) and the most comprehensive taxonomic sampling ever assembled (224 species belonging to 31 out of 33 recognized grammitids genera). 31 species from Madagascar were included representing 87% of the described diversity and 77% of the endemics. Our results confirmed a Paleotropical clade nested within an amphi-Atlantic grade. In addition, we identified three new major clades involving species currently belonging to Grammitis s.l., Ctenopterella and Enterosora. We resolved for the first time Grammitis s.s. as monophyletic, and Ctenopterella (newly tested here) and Enterosora as polyphyletic. The Neotropical genus Moranopteris was shown to also occur in Madagascar through a newly discovered species. Most importantly, we suggest a >30% inflation of the species number in the WIO due to the hidden diversity in >10 cryptic lineages, best explained by high morphological homoplasy. Molecular dating and ancestral areas reconstruction allowed identifying the Neotropics as the predominant source of LDD to the African-WIO region, with at least 12 colonization events within the last 20Ma. Repeated eastward migrations may be explained by transoceanic westerly winds transporting the dust-like spores. Tropical Asia s.l. would also have played a (minor) role through one dispersal event to Madagascar at the end of the Oligocene. Last, within the complex Malagasy region made of a mosaic of continental and oceanic islands located close to the African continent, we showed that contrary to theoretical expectations and empirical evidence in angiosperms, Africa does not act as a dispersal source and Madagascar seems to have a more important influence on the regional dynamics: we observed both in situ species diversification and dispersal out of Madagascar. This influence also extends beyond the region, since one dispersal event probably originated from Madagascar and reached the Subantarctic island of Amsterdam.

Morphological innovation, ecological opportunity, and the radiation of a major vascular epiphyte lineage.

The emergence of angiosperm-dominated tropical forests in the Cretaceous led to major shifts in the composition of biodiversity on Earth. Among these was the rise to prominence of epiphytic plant lineages, which today comprise an estimated one-quarter of tropical vascular plant diversity. Among the most successful epiphytic groups is the Polypodiaceae, which comprises an estimated 1500 species and displays a remarkable breadth of morphological and ecological diversity. Using a time-calibrated phylogeny for 417 species, we characterized macroevolutionary patterns in the family, identified shifts in diversification rate, and identified traits that are potential drivers of diversification. We find high diversification rates throughout the family, evidence for a radiation in a large clade of Paleotropical species, and support for increased rates of diversification associated with traits including chlorophyllous spores and noncordiform gametophytes. Contrary to previous hypotheses, our results indicate epiphytic species and groups with humus-collecting leaves diversify at lower rates than the family as a whole. We find that diversification rates in the Polypodiaceae are positively correlated with changes in elevation. Repeated successful exploration of novel habitat types, rather than morphological innovation, appears to be the primary driver of diversification in this group.

Why are there so few species of ferns?

A recent study has documented a natural hybridization event between two fern lineages that last shared a common ancestor about 60 million years ago. This is one of the deepest hybridization events ever described and has important implications for plant speciation theory.

Global phylogeny and biogeography of grammitid ferns (Polypodiaceae).

We examined the global historical biogeography of grammitid ferns (Polypodiaceae) within a phylogenetic context. We inferred phylogenetic relationships of 190 species representing 31 of the 33 currently recognized genera of grammitid ferns by analyzing DNA sequence variation of five plastid DNA regions. We estimated the ages of cladogenetic events on an inferred phylogeny using secondary fossil calibration points. Historical biogeographical patterns were inferred via ancestral area reconstruction. Our results supported four large-scale phylogenetic and biogeographic patterns: (1) a monophyletic grammitid clade that arose among Neotropical polypod ancestors about 31.4 Ma; (2) a paraphyletic assemblage of clades distributed in the Neotropics and the Afro-Malagasy region; (3) a large clade distributed throughout the Asia-Malesia-Pacific region that originated about 23.4 Ma; and, (4) an Australian or New Zealand origin of the circumaustral genus Notogrammitis. Most genera were supported as monophyletic except for Grammitis, Oreogrammitis, Radiogrammitis, and Zygophlebia. Grammitid ferns are a well-supported monophyletic group with two biogeographically distinct lineages: a primarily Neotropical grade exhibiting several independent successful colonizations to the Afro-Malagasy region and a primarily Paleotropical clade exhibiting multiple independent dispersals to remote Pacific islands and temperate, austral regions.

Ecological factors influencing growth of the endangered Hawaiian fern Marsilea villosa (Marsileaceae) and implications for conservation management.

PREMISE OF THE STUDY: Conserving endangered plants is a complex task, and practitioners must often use a "triage" approach, addressing only immediate needs. Ecologists can improve this process by conducting sound science upon which to base management. Marsilea villosa is an endangered, endemic Hawaiian fern with seven remaining populations in ephemerally flooding drylands. Among its uncommon traits are long-lived sporocarps, requiring flood and drought to complete its sexual life cycle, and extensive vegetative growth. METHODS: We conducted a 3-yr ecological field study, measuring percent cover of M. villosa and associated species, flooding depth, and canopy cover, to identify ecological factors with the greatest impact on M. villosa growth. KEY RESULTS: Maximum flooding depth and canopy cover had strong positive relationships with M. villosa growth, and all plots with >50% threshold of either variable reached 100% cover of M. villosa by the end of the study. Interaction effects explained nuances of these relationships, including synergy between the two variables. Percent cover of nonnative functional groups (graminoids and nongraminoids) each had negative relationships with M. villosa growth, but interactions showed that nongraminoid cover was driven by particular species, and that time since flooding had greater influence on M. villosa growth than graminoid cover. CONCLUSIONS: We recommend planting reintroduced populations in flood-prone areas with moderate shade, experimental outplanting of native plants with M. villosa, and management of graminoids as a functional group, while nongraminoid management should be species-specific. These practices will promote self-sustaining populations and reduce the need for labor-intensive management.

New insights into the phylogeny and historical biogeography of the Lellingeria myosuroides clade (Polypodiaceae).

Grammitid ferns are a well-supported clade of ~900 primarily tropical epiphytic species. Recent phylogenetic studies have found support for a distinctive, geographically diverse group of 24 species referred to as the Lellingeria myosuroides clade and have provided evidence for a variety of phylogenetic relationships within the group, as well as hypotheses of historical processes that have produced current biogeographical patterns. We present new data and analyses that support the following primary conclusions: 1) the L. myosuroides clade is monophyletic and pantropical; 2) that clade is sister to a more species rich clade of entirely Neotropical species (Lellingeria s.s.); 3) we infer two independent dispersal events from the Neotropics to Pacific islands, five independent dispersal events from the Neotropics to the Paleotropics, and two separate dispersal events from mainland tropical America to the West Indies.

Mitochondrial DNA evolution in the Anaxyrus boreas species group.

The Anaxyrus boreas species group currently comprises four species in western North America including the broadly distributed A. boreas, and three localized species, Anaxyrus nelsoni, Anaxyrusexsul and Anaxyrus canorus. Phylogenetic analyses of the mtDNA 12S rDNA, cytochrome oxidase I, control region, and restriction sites data, identified three major haplotype clades. The Northwest clade (NW) includes both subspecies of A. boreas and divergent minor clades in the middle Rocky Mountains, coastal, and central regions of the west and Pacific Northwest. The Southwest (SW) clade includes A. exsul, A. nelsoni, and minor clades in southern California. Anaxyrus canorus, previously identified as paraphyletic, has populations in both the NW and SW major clades. The Eastern major clade (E) includes three divergent lineages from southern Utah, the southern Rocky Mountains, and north of the Great Basin at the border of Utah and Nevada. These results identify new genetic variation in the eastern portion of the toad's range and are consistent with previous regional studies from the west coast. Low levels of control region sequence divergence between major clades (2.2-4.7% uncorrected pair-wise distances) are consistent with Pleistocene divergence and suggest that the phylogeographic history of the group was heavily influenced by dynamic Pleistocene glacial and climatic changes, and especially pluvial changes, in western North America. Results reported here may impact conservation plans in that the current taxonomy does not reflect the diversity in the group.

Evolutionary history and phylogeography of Encelia farinosa (Asteraceae) from the Sonoran, Mojave, and Peninsular Deserts.

Pleistocene glaciations have had a profound influence on the genetic structure of plant species throughout the Northern Hemisphere because of range contractions, fragmentations, and expansions. Phylogeographic studies have contributed to our knowledge of this influence in several geographic regions of North America, however, very few phylogeographic studies have examined plant species in the Sonoran, Mojave, and Peninsular deserts. In this study, we used sequence data from the chloroplast DNA psbA-trnH intergenic spacer to obtain information on phylogeographic patterns among 310 individuals from 21 populations of Encelia farinosa ("brittlebush"; Asteraceae) across its range. We applied several population and spatial genetic analyses that allowed us to interpret our data with respect to Pleistocene climate change. These analyses indicate that E. farinosa displays patterns of genetic differentiation and geographic structuring consistent with postglacial range expansion. Populations of E. farinosa are characterized by distinct haplotype lineages significantly associated with geography. Centers of genetic diversity for the species occur in southwestern Arizona, the plains of Sonora, and Baja California Sur, all of which are putative sites of glacial refugia as predicted by analyses of macrofossil and pollen data. Nested clade analysis suggests that genetic structure in E. farinosa has been affected by past fragmentation followed by range expansion. Range expansion in several locations is further supported by significant departures from neutrality for values of Fu's F(S) and Tajima's D, and mismatch analyses.

Origin of the endemic fern genus Diellia coincides with the renewal of Hawaiian terrestrial life in the Miocene.

The enigmatic fern genus Diellia, endemic to the Hawaiian archipelago, consists of five extant and one recently extinct species. Diellia is morphologically highly variable, and a unique combination of characters has led to several contrasting hypotheses regarding the relationship of Diellia to other ferns. A phylogenetic analysis of four chloroplast loci places Diellia within 'black-stemmed' rock spleenworts of the species-rich genus Asplenium, as previously suggested by W. H. Wagner. Using an external calibration point, we estimate the divergence of the Diellia lineage from its nearest relatives to have occurred at ca. 24.3 Myr ago matching an independent estimate for the renewal of Hawaiian terrestrial life (ca. 23 Myr ago). We therefore suggest that the ancestor of the Diellia lineage may have been among the first successful colonists of the newly emerging islands in the archipelago. Disparity between morphological and nucleotide sequence variation within Diellia is consistent with a recent rapid radiation. Our estimated time of the Diellia radiation (ca. 2 Myr ago) is younger than the oldest island of Kaua'i (ca. 5.1 Myr ago) but older than the younger major islands of Maui (ca. 1.3 Myr ago), Lana'i (ca. 1.3 Myr ago) and Hawaii (ca. 0.43 Myr ago).

Unraveling the phylogeny of polygrammoid ferns (Polypodiaceae and Grammitidaceae): exploring aspects of the diversification of epiphytic plants.

We explore the phylogeny of the polygrammoid ferns using nucleotide sequences derived from three plastid loci for each of 98 selected species. Our analyses recovered four major monophyletic lineages: the loxogrammoids, two clades consisting of taxa restricted to the Old World, and a largely neotropical clade that also includes the pantropical Grammitidaceae. The loxogrammoid lineage diverges first and is sister to a large clade comprising the three remaining species-rich lineages. One paleotropical clade includes the drynarioid and selligueoid ferns, whereas the second paleotropical clade includes the platycerioids, lepisoroids, microsoroids, and their relatives. The grammitids nest within the neotropical clade, although the sister taxon of this circum-tropic, epiphytic group remains ambiguous. Microsorum and Polypodium, as traditionally defined, were recovered as polyphyletic. The relatively short branch lengths of the deepest clades contrast with the long branch lengths leading to the terminal groups. This suggests that the polygrammoid ferns arose through an old, rapid radiation. Our analysis also reveals that the rate of substitution in the grammitids is remarkably higher relative to other polygrammoids. Disparities in substitution rate may be correlated with one or more features characterizing grammitids, including species richness, chlorophyllous spores, and an extended gametophytic phase.

MULTIPLE COLONIZATIONS OF ASPLENIUM ADIANTUM-NIGRUM ONTO THE HAWAIIAN ARCHIPELAGO.

The extreme isolation and mid-Pacific origin of the Hawaiian archipelago has ensured that all indigenous organisms have arrived via long-distance dispersal or have evolved from successfully colonizing species. Although this isolation has also produced high rates of species endemism in angiosperms (89% or more), that rate in pteridophytes is considerably less (76%). The ratio of native species to the estimated number of original successful colonizing species in angiosperms (3.4) is more than double that for pteridophytes (1.6). One possible explanation for the lower speciation rate in pteridophytes is that populations of these species are more likely to experience interpopulational gene flow because of the great vagility of their wind-dispersed spores. We conducted isozymic surveys of populations from the island of Hawaii of the indigenous allotetraploid species Asplenium adiantum-nigrum, putatively derived from two strictly European diploid taxa. Our data support multiple hybrid origins for the populations surveyed, with a minimum of 3, and possibly as many as 17, discrete hybridization events having produced the genetic diversity observed. Since the parental taxa are not found in Hawaii, each hybrid lineage must have arrived in the archipelago independently of the others. Similar long-distance, repeated dispersal events may be occurring between insular and noninsular populations of other native pteridophytes in Hawaii and in other insular regions of the world, thus contributing to the relatively low rates of speciation and insular endemism in this ancient group of plants.