Genetic relationships between Bidens forbesii and six species in the Hawaiian and the Marquesas Islands

A crossing program was carried out between the Kauai endemicB. forbesii and six other Polynesian species, five of which are Hawaiian and one Marquesan. All crosses produced vigorous F₁ hybrids, portraying a strong genetic relationship betweenB. forbesii and the other species. The results indicate a close systematic relationship among the Polynesian species ofBidens placed by Sherff in sect.Campylotheca and strengthen the argument that this group dispersed from North America to the Hawaiian Islands, then from Hawaii to the Marquesas Islands.     

The Hawaiian Archipelago is a stepping stone for dispersal in the Pacific: an example from the plant genus Melicope (Rutaceae)

Aim Pacific biogeographical patterns in the widespread plant genus Melicope J.R. Forst. & G. Forst. (Rutaceae) were examined by generating phylogenetic hypotheses based on chloroplast and nuclear ribosomal sequence data. The aims of the study were to identify the number of colonization events of Melicope to the Hawaiian Islands and to reveal the relationship of Hawaiian Melicope to the Hawaiian endemic genus Platydesma H. Mann. The ultimate goal was to determine if the Hawaiian Islands served as a source area for the colonization of Polynesia. Location Nineteen accessions were sampled in this study, namely eight Melicope species from the Hawaiian Islands, four from the Marquesas Islands, one species each from Tahiti, Australia and Lord Howe Island, two Australian outgroups and two species of the Hawaiian endemic genus Platydesma. To place our results in a broader context, 19 sequences obtained from GenBank were included in an additional analysis, including samples from Australia, Papua New Guinea, New Zealand, Southeast Polynesia and Asia. Methods DNA sequences were generated across 19 accessions for one nuclear ribosomal and three chloroplast gene regions. Maximum parsimony analyses were conducted on separate and combined data sets, and a maximum likelihood analysis was conducted on the combined nuclear ribosomal and chloroplast data set. A broader nuclear ribosomal maximum parsimony analysis using sequences obtained from GenBank was also performed. Geographic areas were mapped onto the combined chloroplast and nuclear ribosomal tree, as well as onto the broader tree, using the parsimony criterion to determine the dispersal patterns. Results Phylogenetic analyses revealed that Platydesma is nested within Melicope and is sister to the Hawaiian members of Melicope. The Hawaiian Melicope + Platydesma lineage was a result of a single colonization event, probably from the Austral region. Finally, Marquesan Melicope descended from at least one, and possibly two, colonization events from the Hawaiian Islands. Main conclusions These data demonstrate a shifting paradigm of Pacific oceanic island biogeography, in which the patterns of long‐distance dispersal and colonization in the Pacific are more dynamic than previously thought, and suggest that the Hawaiian Islands may act as a stepping stone for dispersal throughout the Pacific.     

Comparative life history of five HokkaidoPolystichum ferns with reference to leaf development in relation to altitudinal distribution

The temperate fernsPolystichum craspedosorum, P. retroso-paleaceum, P. tripteron, P. braunii andP. microchlamys are distributed widely in Hokkaido: on 13 Hokkaido mountains their average altitudinal distributions are 450, 479, 570, 689 and 964 m above sea level, respectively. The developmental stage of the sporophytic leaf is expressed by the “number of venation” (NV, the number of veins branching from the midrib of the leaf), which, inPolystichum ferns, is itself a qualitative expression of the phase-change from sterile to fertile leaf production and is more discriminatory than leaf area, length or dry weight. Usually, the developmental stage structure of the fertile leaf expressed by NV in the fivePolystichum ferns showed a normal distribution. Among the fourPolystichum ferns that grow in the forest understory of Hokkaido's cool temperate regions, a good correlation was found between the mean altitude of vertical distribution and the maximum NV of the leaf (r=−0.993) and the initiation of maturity in the relative developmental stage (r=0.991) of the ferns.Polystichum craspedosorum found on cliffs, however, matures at much earlier stage and has the smallest maximum NV. In the developmental stage expressed by the NV, the initiation of fertility and maximum NV seem to be correlated with altitudinal distribution and habitat in populations ofPolystichum ferns in Hokkaido. Contribution No. 2694 from the Inst. of Low Temp. Sci., Hokkaido University.     

Phylogeny and biogeography of Chinese and Australasian Polystichum ferns as inferred from chloroplast trnL-F and rps4-trnS sequence data

Polystichum, one of the largest genera of ferns, occurs worldwide with the greatest diversity in southwest China and adjacent regions. Although there have been studies of Chinese Polystichum on its traditional classification, geographic distributions, and even a few on its molecular systematics, its relationships to other species outside China remain little known. Here, we investigated the phylogeny and biogeography of the Polystichum species from China and Australasia. The evolutionary relationships among 42 Polystichum species found in China (29 taxa) and Australasia (13 taxa) were inferred from phylogenetic analyses of two chloroplast DNA sequence data sets: rps4-trnS and trnL-F intergenic spacers. The divergence time between Chinese and Australasian Polystichum was estimated. The results indicated that the Australasian species comprise a monophyletic group that is nested within the Chinese diversity, and that the New Zealand species are likewise a monophyletic group nested within the Australasian species. The divergence time estimates suggested that Chinese Polystichum migrated into Australasia from around 40 Ma ago, and from there to New Zealand from about 14 Ma. The diversification of the New Zealand Polystichum species began about 10 Ma. These results indicated that Polystichum probably originated in eastern Asia and migrated into Australasia: first into Australia and then into New Zealand.     

Cainozoic ferns and their distribution

The phytogeographic distribution of Cainozoic ferns is reported based upon a critical re-appraisal of the macrofossil and mesofossil record also taking account of evidence from a few highly diagnostic spores. Well-documented circum-Arctic Cainozoic floras show ferns (Woodwardia, Onoclea, Osmunda, Coniopteris and to a lesser extentAzolla) distributed around the pole to very high paleolatitudes. Some ferns are shared between the mid-paleolatitudes of North America and Europe as would be predicted from the distributions of other biota. Evidence for the composition of Cainozoic fern floras is minimal in some regions (e.g., Antarctica, Central and South America, Africa, India, South East Asia), so the absence of fern fossils from these areas has no biogeographical significance. Matoniaceae were abundant in the preceding Mesozoic. However, the absence of Cainozoic macrofossils, and the fact that no CainozoicMatonisporites spores areMatonia-like, indicates that Matoniaceae had attained their modern relict distribution by, or very early in, the Cainozoic. The important Mesozoic families Marattiaceae and Dipteridaceae are also not represented by Cainozoic macrofossils. They probably also showed Cainozoic restriction but spores are not sufficiently diagnostic to enable testing of this hypothesis. Other ferns, which were also important in the Mesozoic (e.g., Dicksoniaceae, Gleicheniaceae), have patchy, equivocal, or inadequately published Cainozoic records. The dispersed spore record may provide an opportunity to track Cainozoic Gleicheniaceae but this approach is not without problems. Most well-represented Cainozoic fern families, genera and subgenera show widespread Cainozoic ranges, typically with considerable range extensions over their living relatives, both onto other continents and north and south to higher paleolatitudes. These include Schizaeaceae (Lygodium, Anemia, and the extinctRuffordia), Osmundaceae (Osmunda), Pteridaceae (Acrostichum), Thelypteridaceae (Cyclosorus), Lophosoriaceae (Lophosoria), Cyatheaceae (theCnemidaria/Cyathea decurrens clade) and the heterosporous water fernAzolla (Azollaceae). A few well-represented ferns show Cainozoic distributions similar to those of the present day (e.g.,Salvinia [Salviniaceae] andCeratopteris [Pteridaceae] (the latter by the Neogene and based only on spores]) but even these had slightly broader ranges in the Cainozoic. Some Cainozoic ferns have apparently local distributions, e.g.,Blechnum dentatum (Blechnaceae) in Europe; and others are so far represented at only one or few sites, e.g.,Dennstaedtiopsis (Dennstaedtiaceae),Botrychium (Ophioglossales),Grammitis (Grammitidaceae), andMakotopteris andRumohra (Dryopteridaceae). Cainozoic fossils assigned toDryopteris (and some other dryopteroids) require revision along with those of Thelypteridaceae, the latter having high potential to provide useful paleobiogeographic evidence, at least of theCyclosorus group. Cainozoic records of Hymenophyllaceae and Polypodiaceae are here considered unconfirmed.     

Repeated range expansion and niche shift in a volcanic hotspot archipelago: Radiation of C4 Hawaiian Euphorbia subgenus Chamaesyce (Euphorbiaceae)

Woody perennial plants on islands have repeatedly evolved from herbaceous mainland ancestors. Although the majority of species in Euphorbia subgenus Chamaesyce section Anisophyllum (Euphorbiaceae) are small and herbaceous, a clade of 16 woody species diversified on the Hawaiian Islands. They are found in a broad range of habitats, including the only known C₄ plants adapted to wet forest understories. We investigate the history of island colonization and habitat shift in this group. We sampled 153 individuals in 15 of the 16 native species of Hawaiian Euphorbia on six major Hawaiian Islands, plus 11 New World close relatives, to elucidate the biogeographic movement of this lineage within the Hawaiian island chain. We used a concatenated chloroplast DNA data set of more than eight kilobases in aligned length and applied maximum likelihood and Bayesian inference for phylogenetic reconstruction. Age and phylogeographic patterns were co‐estimated using BEAST. In addition, we used nuclear ribosomal ITS and the low‐copy genes LEAFY and G3pdhC to investigate the reticulate relationships within this radiation. Hawaiian Euphorbia first arrived on Kaua`i or Ni`ihau ca. 5 million years ago and subsequently diverged into 16 named species with extensive reticulation. During this process Hawaiian Euphorbia dispersed from older to younger islands through open vegetation that is disturbance‐prone. Species that occur under closed vegetation evolved in situ from open vegetation of the same island and are only found on the two oldest islands of Kaua`i and O`ahu. The biogeographic history of Hawaiian Euphorbia supports a progression rule with within‐island shifts from open to closed vegetation.     

Origins of the Hawaiian flora: Phylogenies and biogeography reveal patterns of long‐distance dispersal

Botanists have long considered the origins of the Hawaiian flora in terms of long‐distance dispersal from particular source areas. We extensively reviewed phylogenetic studies of the Hawaiian angiosperm flora to determine the most likely region of origin for each lineage from a defined set of source areas. We also evaluated dispersal modes of each lineage to assess whether certain dispersal modes are associated with a given source area. The largest source category was Widespread (involving related taxa that extend across more than one region), although many of these comprised native non‐endemic species, and accounted for little of the total species diversity (after accounting for in situ speciation). The next largest source regions were Indo‐Malayan and Neotropical. Comparatively few lineages originated from the East Asian region, although these include the single largest lineage. Lineages originating in the Indo‐Malayan region predominantly arrived via Pacific Islands, whereas dispersal from all other regions appears to have been mostly direct. Compared with previous analyses, we found a higher proportion of lineages originating in the Neotropics and temperate North America. Widespread origins were positively associated with dispersal via flotation on water, whereas other origins were associated with dispersal by birds, either through internal transport or external adhesion. We identified thirty‐one potential cases of dispersal out of Hawaii to other islands. Our assessment is complicated by lineages with ancient origins, with further complications likely stemming from hybridization events. Overall, numerous lineages including some distinctive endemic genera have not had sufficient phylogenetic study to determine an origin.     

Trans‐Atlantic,trans‐Pacific and trans‐Indian Ocean dispersal in the small Gondwanan Laurales family Hernandiaceae

Aim To investigate the historical biogeography of the pantropical flowering plant family Hernandiaceae (Laurales), which today comprises 62 species in five genera. Location Hernandiaceae occur in Africa (9 species), Madagascar (4), the Neotropics (25), Australia (3), southern China, Indochina, Malesia, and on numerous Pacific Islands (32). These numbers include two widespread species, Hernandia nymphaeifolia, which ranges from East Africa to the Ogasawara Islands and New Caledonia, and Gyrocarpus americanus, thought to have a pantropical range. Methods We sampled 37 species from all genera, the widespread ones with multiple accessions, for a chloroplast DNA matrix of 2210 aligned nucleotides, and used maximum likelihood to infer species relationships. Divergence time estimation relied on an uncorrelated‐rates relaxed molecular clock calibrated with outgroup fossils of Lauraceae and Monimiaceae. Results The deepest split in the family is between a predominantly African–Madagascan–Malesian lineage comprising Hazomalania, Hernandia and Illigera, and an African–Neotropical lineage comprising Gyrocarpus and Sparattanthelium; this split may be 122 (110–134) Myr old. The stem lineages of the five genera date back at least to the Palaeocene, but six splits associated with transoceanic range disjunctions date only to the Oligocene and Miocene, implying long‐distance dispersal. It is inferred that Hernandia beninensis reached the West African islands of São Tomé and Bioko from the West Indies or the Guianas; Hernandia dispersed across the Pacific; and Illigera madagascariensis reached Madagascar from across the Indian Ocean. Main conclusions The disjunct ranges and divergence times of sister clades in the Hernandiaceae are partly congruent with the break‐up of West Gondwana, but mostly with later transoceanic dispersal. An exceptional ability to establish following prolonged oceanic dispersal may be largely responsible for the evolutionary persistence of this small clade.     

Biogeography of temperate Australasian Polystichum ferns as inferred from chloroplast sequence and AFLP

Aim and location New Zealand began to separate from Gondwana c. 85 Ma, and has been isolated from the nearest large landmass, Australia, by some 2000 km of the Tasman Sea since c. 60 Ma. Given New Zealand's long geographical isolation, there has been considerable interest in explaining the origins of its different biotic elements. Here we investigate the biogeography of the fern genus Polystichum from temperate Australasia. Six species are found in New Zealand, four in Australia, and two on Lord Howe Island. Methods The evolutionary relationships between the twelve Polystichum species found in temperate Australasia were inferred from phylogenetic analyses of two molecular data sets: DNA sequence from the chloroplast rps4–trnS spacer locus; and AFLP DNA‐fingerprinting. The timing of the separation between Australian and New Zealand Polystichum was estimated by using the fossil record to temporally calibrate the rbcL sequence differentiation between representative species from these regions. Results Species of Polystichum from New Zealand appear to comprise a monophyletic group. This suggests that Polystichum crossed the Tasman only once. Temporal calibration of the rbcL sequence differentiation between Australian and New Zealand Polystichum indicates that a vicariant explanation for their separation can be rejected in favour of trans‐oceanic dispersal. Main conclusions The extant diversity within New Zealand Polystichum appears to have been derived from a single, trans‐oceanic dispersal event (within the last c. 20 Myr), followed by a relatively extensive in situ ecological radiation.     

A SURVEY FOR 1,3,6,7-TETRAHYDROXY-C-GLYCOSYLXANTHONES EMPHASIZING THE “PRIMITIVE” LEPTOSPORANGIATE FERNS AND THEIR ALLIES

A survey for 1,3,6,7-tetrahydroxy-C-glycosylxanthones of representative species within the primitive vascular plants, emphasizing the leptosporangiate ferns, has indicated a limited distribution of these compounds within three leptosporangiate families: Hymenophyllaceae, Aspleniaceae and Marsileaceae. In the Hymenophyllaceae the distribution of these compounds appears to be a useful criterion for segregating species of Mecodium from other species of Hymenophyllum (sensu lato) and suggests that the tubulate vs. the valvate indusial condition may not be an ideal character for separating all species of Hymenophyllum (s.l.) from those of Trichomanes (s.l.). These compounds appear useful for delimiting several species of Elaphoglossum section Pachyglossa and support a relationship among the Aspleniaceae, Athyriaceae, and Elaphoglossaceae. Their presence in Marsilea also raises questions as to the origin of this group of plants.     

Autochory in ferns,not all spores are blown with the wind

Dispersal is a key process in plant population dynamics. In ferns, two successive vectors are needed: the sporangium catapulting mechanism, and wind or gravity. However, some rock ferns have a growth habit that suggests a kind of autochory by placing spores on the rock surface. Moreover, some ferns show modifications of the sporangial dehiscence. To determine the role of growth habit in spore dispersal, we checked the sporangial opening mechanism and explored the spatial distribution of plants on the walls. The presence of spores of Asplenium celtibericum, a rupicolous fern, in the rock surface was checked. In addition, its sporangial dehiscence, plant size and position in the wall were analysed. Spores and indehiscent sporangia were present on walls at each sampling moment. Their highest number was found close to the plants. There was a positive correlation between crack width and plant size. However, most plants occupy the upper half of the cliffs. The growth habit of A. celtibericum is instrumental to deposit the spores over the neighbouring rock surface, thus enhancing the probability of spores to find suitable crevices for germination. Furthermore, dispersal of indehiscent sporangia might promote intergametophytic mating, and the modified sporangial opening mechanism extends the dispersive period.     

Population structure of island‐associated dolphins: Evidence from mitochondrial and microsatellite markers for common bottlenose dolphins (Tursiops truncatus) around the main Hawaiian Islands

We used mitochondrial and nuclear genetic markers to investigate population structure of common bottlenose dolphins, Tursiops truncatus, around the main Hawaiian Islands. Though broadly distributed throughout the world's oceans, bottlenose dolphins are known to form small populations in coastal waters. Recent photo‐identification data suggest the same is true in Hawaiian waters. We found genetic differentiation among (mtDNA Φ_ST= 0.014–0.141, microsatellite F’_ST= 0.019–0.050) and low dispersal rates between (0.17–5.77 dispersers per generation) the main Hawaiian Island groups. Our results are consistent with movement rates estimated from photo‐identification data and suggest that each island group supports a demographically independent population. Inclusion in our analyses of samples collected near Palmyra Atoll provided evidence that the Hawaiian Islands are also occasionally visited by members of a genetically distinct, pelagic population. Two of our samples exhibited evidence of partial ancestry from Indo‐Pacific bottlenose dolphins (T. aduncus), a species not known to inhabit the Hawaiian Archipelago. Our findings have important implications for the management of Hawaiian bottlenose dolphins and raise concerns about the vulnerability to human impacts of pelagic species in island ecosystems.     

DECOUPLING OF SHORT‐ AND LONG‐DISTANCE DISPERSAL PATHWAYS IN THE ENDEMIC NEW ZEALAND SEAWEED CARPOPHYLLUM MASCHALOCARPUM (PHAEOPHYCEAE,FUCALES)1

The processes that produce and maintain genetic structure in organisms operate at different timescales and on different life‐history stages. In marine macroalgae, gene flow occurs through gamete/zygote dispersal and rafting by adult thalli. Population genetic patterns arise from this contemporary gene flow interacting with historical processes. We analyzed spatial patterns of mitochondrial DNA variation to investigate contemporary and historical dispersal patterns in the New Zealand endemic fucalean brown alga Carpophyllum maschalocarpum (Turner) Grev. Populations bounded by habitat discontinuities were often strongly differentiated from adjoining populations over scales of tens of kilometers and intrapopulation diversity was generally low, except for one region of northeast New Zealand (the Bay of Plenty). There was evidence of strong connectivity between the northern and eastern regions of New Zealand’s North Island and between the North and South Islands of New Zealand and the Chatham Islands (separated by 650 km of open ocean). Moderate haplotypic diversity was found in Chatham Islands populations, while other southern populations showed low diversity consistent with Last Glacial Maximum (LGM) retreat and subsequent recolonization. We suggest that ocean current patterns and prevailing westerly winds facilitate long‐distance dispersal by floating adult thalli, decoupling genetic differentiation of Chatham Island populations from dispersal potential at the gamete/zygote stage. This study highlights the importance of encompassing the entire range of a species when inferring dispersal patterns from genetic differentiation, as realized dispersal distances can be contingent on local or regional oceanographic and historical processes.     

Multiple origins of Hawaiian drosophilids: Phylogeography of Scaptomyza Hardy (Diptera: Drosophilidae)

Scaptomyza is a highly diversified genus in the family Drosophilidae, having undergone an explosive radiation, along with the Hawaiian‐endemic genus Idiomyia in the Hawaiian Islands: about 60% of 269 Scaptomyza species so far described are endemic to the Hawaiian Islands. Two hypotheses have been proposed for the origin and diversification of Hawaiian drosophilids. One is the “single Hawaiian origin” hypothesis: Scaptomyza and Idiomyia diverged from a single common ancestor that had once colonized the Hawaiian Islands, and then non‐Hawaiian Scaptomyza migrated back to continents. The other is the “multiple origins” hypothesis: Hawaiian Scaptomyza and Idiomyia derived from different ancestors that independently colonized the Hawaiian Islands. A key issue for testing these two hypotheses is to clarify the phylogenetic relationships between Hawaiian and non‐Hawaiian species in Scaptomyza. Toward this goal, we sampled additional non‐Hawaiian Scaptomyza species, particularly in the Old World, and determined the nucleotide sequences of four mitochondrial and seven nuclear genes for these species. Combining these sequence data with published data for 79 species, we reconstructed the phylogeny and estimated ancestral distributions and divergence times. In the resulting phylogenetic trees, non‐Hawaiian Scaptomyza species were interspersed in two Hawaiian clades. From a reconstruction of ancestral biogeography, we inferred that Idiomyia and Scaptomyza diverged outside the Hawaiian Islands and then independently colonized the Hawaiian Islands, twice in Scaptomyza, thus supporting the “multiple origins” hypothesis.     

Disentangling the dynamics of invasive fireweed (<Emphasis Type="Italic">Senecio madagascariensis</Emphasis> Poir. species complex) in the Hawaiian Islands

Studies investigating the genetic variation of invasive species render opportunities to better understand the dynamics of biological invasions from an ecological and evolutionary perspective. In this study, we investigate fine-scale population genetic structure of invasive Senecio madagascariensis (fireweed) using microsatellite markers to determine levels of genetic diversity and how it pertains to introduction history of this species within and among the Hawaiian Islands. Dispersal patterns were interpreted and, together with a habitat suitability analysis, we aim to describe the potential range expansion of S. madgascariensis within the islands. Bayesian and frequency-based analyses revealed genetic structure with two major genetic demes corresponding to the two fireweed-infested islands of Maui and Hawaii. Both these demes showed further genetic sub-structure, each consisting of three genetically distinct subgroups. Overall, fireweed showed significant levels of inbreeding. Major genetic demes (Maui and Hawaii) differed in observed heterozygosities, inbreeding and genetic structure, each harbouring a large proportion of private alleles. In contrast to the current understanding of fireweed’s introduction history between the Hawaiian Islands, fine-scale population genetic parameters suggest that this species has been introduced at least twice, possibly even more, to the archipelago. Spatial analyses also revealed high correlation between genetic similarity and geographical proximity (>2 km apart) followed by a sharp decline. In addition, a single population was identified that likely resulted from a rare human- or animal-mediated extreme long-distance dispersal event from Maui to Hawaii. Bayesian and likelihood estimates of ‘first generation migrants’ also concurred that contemporary dispersal occurs more frequently over smaller spatial scales than larger scales. These findings indicate that spread in this species occurs primarily via a stratified strategy. Predictions from habitat suitability models indicate all Hawaiian Islands as highly suitable for fireweed invasion and the movement of propagules to currently uninfested islands and outlying suitable habitats should be avoided to circumvent further expansions of the invasion.     

Diversification of Hawaiian Cyrtandra (Gesneriaceae) under the influence of incomplete lineage sorting and hybridization

Cyrtandra (Gesneriaceae) is a genus of flowering plants with over 800 species distributed throughout Southeast Asia and the Pacific Islands. On the Hawaiian Islands, 60 named species and over 89 putative hybrids exist, most of which are identified on the basis of morphology. Despite many previous studies on the Hawaiian Cyrtandra lineage, questions regarding the reconciliation of morphology and genetics remain, many of which can be attributed to the relatively young age and evidence of hybridization between species. We utilized targeted enrichment, high‐throughput sequencing, and modern phylogenomics tools to test 31 Hawaiian Cyrtandra samples (22 species, two putative hybrids, four species with two samples each, one species with four samples) and two outgroups for species relationships and hybridization in the presence of incomplete lineage sorting (ILS). Both concatenated and species‐tree methods were used to reconstruct species relationships, and network analyses were conducted to test for hybridization. We expected to see high levels of ILS and putative hybrids intermediate to their parent species. Phylogenies reconstructed from the concatenated and species‐tree methods were highly incongruent, most likely due to high levels of incomplete lineage sorting. Network analyses inferred gene flow within this lineage, but not always between taxa that we expected. Multiple hybridizations were inferred, but many were on deeper branches of the island lineages suggesting a long history of hybridization. We demonstrated the utility of high‐throughput sequencing and a phylogenomic approach using 569 loci to understanding species relationships and gene flow in the presence of ILS.     

Conservation of rDNA inPolystichum (Dryopteridaceae)

Restriction site variation in the nuclear 18S–25S ribosomal RNA genes (rDNA) was analyzed hierarchically in a species complex in the fern genusPolystichum. Two distinct rDNA repeat types were present in all individuals ofPolystichum examined. No variation was detected among individuals within a population ofP. munitum, among populations ofP. munitum orP. imbricans, or among the six diploid species ofPolystichum from North America, including the circumborealP. lonchitis. The identity of rDNA repeats across all six North American species ofPolystichum may reflect an overall similarity of the nuclear genomes of these species, an observation supported by isozyme data as well. However, this nuclear similarity contrasts sharply with the highly divergent chloroplast genomes of these six species. The conservative nature of the rDNA inPolystichum also is in contrast to the much more variable rDNAs of most angiosperms investigated. Perhaps the tempo and mode of evolution of rDNA in ferns differ from those of angiosperms; however, the data base for fern rDNA is very small. Furthermore, the number of repeat types per individual is consistent with a diploid, rather than polyploid, condition despite the high chromosome number (n = 41) of these plants, although homogenization of multiple, divergent rRNA genes cannot be disproven.     

Radiation following long‐distance dispersal: the contributions of time,opportunity and diaspore morphology in Sicyos (Cucurbitaceae)

Aim  To infer the most plausible explanations for the presence of 14 species of the Neotropical cucurbit genus Sicyos on the Hawaiian Islands, two on the Galápagos Islands, two in Australia, and one in New Zealand. Location  Neotropics, the Hawaiian and Galápagos archipelagos, Australia and New Zealand. Methods  We tested long‐problematic generic boundaries in the tribe Sicyoeae and reconstructed the history of Sicyos using plastid and nuclear DNA sequences from 87 species (many with multiple accessions) representing the group’s generic and geographic diversity. Maximum likelihood and Bayesian approaches were used to infer relationships, divergence times, biogeographic history and ancestral traits. Results  Thirteen smaller genera, including Sechium, are embedded in Sicyos, which when re‐circumscribed as a monophyletic group comprises 75 species. The 14 Hawaiian species of Sicyos descended from a single ancestor that arrived c. 3 million years ago (Ma), Galápagos was reached twice at c. 4.5 and 1 Ma, the species in Australia descended from a Neotropical ancestor (c. 2 Ma), and New Zealand was reached from Australia. Time since arrival thus does not correlate with Sicyos species numbers on the two archipelagos. Main conclusions  A plausible mechanism for the four trans‐Pacific dispersal events is adherence to birds of the tiny hard fruit with retrorsely barbed spines found in those lineages that underwent long‐distance migrations. The Hawaiian clade has lost these spines, resulting in a lower dispersal ability compared with the Galápagos and Australian lineages, and perhaps favouring allopatric speciation.     

What do we know about Hawaiian ferns and lycophytes?

The Hawaiian Islands are home to one of the most distinctive fern and lycophyte floras in the world. Of the 144 native fern species, 76% are endemic and, including subspecies and varieties, 84% of the 167 native fern taxa are endemic. There are 15 native lycophyte species, 47% of which are endemic, and 16 taxa, 50% of which are endemic. I review here most of the available literature on Hawaiian ferns and lycophytes. Few species of ferns or lycophytes have been studied in any kind of detail and, for most, we only know basic classification and general ecological information. Although the total number of studies reviewed here is not large, research has been conducted on a wide range of topics including systematics, floristics, dispersal, phylogeny, biogeography, ecology, form and function, population genetics, microevolution, fern-animal and fern-fungi associations, reproductive biology, demography, ethnobotany, and conservation.