Historical biogeography and speciation in the Creole wrasses (Labridae, <Emphasis Type="Italic">Clepticus</Emphasis>)

We tested whether vicariance or dispersal was the likely source of speciation in the genus Clepticus by evaluating the evolutionary timing of the effect of the mid-Atlantic barrier, which separates C. brasiliensis and C. africanus, and the Amazon barrier, which separates C. parrae and C brasiliensis. Genetic data from three mitochondrial genes and one nuclear gene were used. Mitochondrial genes separated Clepticus into three well supported clades corresponding to the three recognized allopatric morpho-species. All analyses provided consistent support for an initial separation (~9.68 to 1.86 mya; 4.84% sequence divergence) of the Caribbean and South Atlantic lineages, followed by a much more recent divergence (~ 0.60 to 0.12 mya; 0.3% sequence divergence) of the Brazilian and African sister morpho-species. Both these phylogenetic events occurred well after the formation of the two barriers that currently separate those three allopatric populations. The planktonic larval duration of these species (35–49 days) and coastal pelagic habits may have facilitated dispersal by this genus across those dispersal barriers after they formed.     

Pleistocene speciation of sister taxa in a North Pacific clade of brooding sea stars (<Emphasis Type="Italic">Leptasterias</Emphasis>)

Although numerous coastal marine species show intra-specific lineage splitting and population divergence times that date to the period of glacial cycles during the Pleistocene epoch, reported instances of recent speciation in the coastal marine environment are relatively rare. Marine organisms with brood-protection and other reproductive modes with limited dispersal potential have been suggested to experience more frequent speciation and extinction events than related species with higher dispersal rates, but few studies have actually estimated divergence times of sister species in these organisms. Here, two mitochondrial gene regions (cytochrome oxidase subunit I, putative control region and upstream tRNAs) and a nuclear gene region (Elongation factor 1α subunit intron 4) provide evidence of recent (0.5–1.2 Mya) cladogenetic events in four pairs of putative sister taxa in a predominantly North Pacific brooding subgenus of sea stars (Leptasterias subgenus Hexasterias). Calibration is obtained from a trans-arctic migration in a related clade of sea stars (Leptasterias subgenera Hexasterias and Nesasterias) that is timed to the opening of the Bering Strait at 3.5 ± 0.25 Mya, and uncertainty in the calibration point is accommodated with a normally-distributed Bayesian prior probability. Similar estimates of population splitting times for two of the pairs of putative sister taxa were obtained by a multilocus coalescent analysis. Estimates of mitochondrial mutation rates (0.01/My) were approximately 50% of the values calibrated for sister species pairs in tropical sea stars and sea urchins. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Horizontal movement of ocean sunfish, <Emphasis Type="Italic">Mola mola</Emphasis>, in the northwest Atlantic

Data were retrieved from 25 ocean sunfish (Mola mola) that were tagged with pop-up satellite archival tags in the southern Gulf of Maine (n = 6), off Nantucket Island (n = 17), and off the coast of Georgia (n = 2) between September 2005 and March 2008. Tags remained attached from 7 to 242 days, with a mean attachment period of (X ± SD) 107.2 ± 80.6 days. Ocean sunfish tagged in the Gulf of Maine and southern New England left those areas in the late summer and early autumn and moved south along the continental shelf break. Fish traveled as far south as the Bahamas and the Gulf of Mexico. By moving south, sunfish experienced similar mean sea surface temperatures throughout the tagging period. The maximum straight-line distance traveled by a tagged Mola mola was 2,520 km in 130 days. Two tagged ocean sunfish entered the Gulf of Mexico, one in the December and one in July. Movements were associated with frontal features created by the Gulf Stream and fish moved farther offshore in 2007 when the Gulf Stream was deflected from the shelf break.     

Genealogical relationships within and among shallow-water <Emphasis Type="Italic">Ciona</Emphasis> species (Ascidiacea)

In spite of historical and current interest in Ciona intestinalis and its congeners, little is known about evolutionary relationships among the members of the genus Ciona. Here 744-bp sequences of the mitochondrial cytochrome c oxidase subunit I (COI) gene are used to examine phylogenetic relationships among three described species (C. intestinalis, C. roulei, C. savignyi) sampled from multiple coastal sites in the Northeast Pacific (CA, USA), Northwest Atlantic (from New Hampshire to Connecticut, USA), Northeast Atlantic (Sweden and The Netherlands), and Mediterranean (Banyuls-sur-Mer, France). The samples were collected in June–October 2005. The COI sequences of Northeast Pacific/Mediterranean (Type A) and Northwest Atlantic (Type B) C. intestinalis differ by ∼12% and C. roulei is nested within Type B C. intestinalis. Ciona savignyi differs from all other haplotypes by 13–16%. A previously undescribed but morphologically distinct Ciona sp. found at the Banyuls-sur-Mer site was >10% divergent from all other haplotypes. Although these data arise from a single gene study, they indicate that further elucidation of species relationships within the genus and of the species’ distributions will be needed if continuing invasions and potential reproductive isolation are to be investigated.     

Interrelationships of the two families constituting the Lophogastrida (Crustacea: Mysidacea) inferred from morphological and molecular data

The Lophogastrida are primitive Mysidacea and comprise only six genera. One of these, Eucopia is considered as highly specialized and constitutes the family Eucopiidae; the other genera constitute the Lophogastridae. Among the latter family, the genus Gnathophausia is closely related to Eucopia, with two species (G. gracilis and E. sculpticauda) sharing similar morphological characteristics [i.e. ornamentation (spines) of the uropods, and the gastric mill]. This indicates that these species are phylogenetically related. To test this hypothesis, the partial 16S mitochondrial ribosomal RNA gene from various representative species of Gnathophausia and Eucopia were compared. The resulting phylogenetic tree suggests that each genus is monophyletic, and that Gnathophausia, which is the deepest-branching genus, is the most primitive, with the Eucopiidae originating from the Lophogastridae. The molecular results support the morphological hypothesis, and suggest an early separation of the two genera or a rapid divergence of Eucopia due to morphological specialization. Received: 29 June 1997 / Accepted: 16 March 1998     

Reproduction in <Emphasis Type="Italic">Heteroteuthis dispar</Emphasis> (Rüppell, 1844) (Mollusca: Cephalopoda): a sepiolid reproductive adaptation to an oceanic lifestyle

Small cephalopods of the genus Heteroteuthis are the most pelagic members in the family Sepiolidae. This study examines the reproductive biology of Heteroteuthis dispar (Rüppell, 1844), the first such study on any member of the genus, based on 46 specimens (27 females and 19 males) collected during the Mar-Eco cruise in the North Atlantic in the region of the Mid-Atlantic Ridge in 2004, and compares it with reproductive features in the less pelagic members of the family. The unusually large spermatophores of the males have a very small ejaculatory apparatus and cement body, relative to the size of the sperm mass. Females first mate when they are still maturing: a large sperm mass (up to 3.4% of the female body mass), consisting of one to several spermatangia, was found in an internal seminal receptacle of the majority of the females examined regardless of their maturity state. The seminal receptacle has a unique form and position in this species. The receptacle is a thin-walled sac at the posterior end of the visceral mass that is an outpocketing of, and opens into, the visceropericardial coelom. Spermatangia and sperm from the spermatangia apparently enter into the visceropericardial coelom (which is mostly occupied by the ovary) from the seminal receptacle indicating that ova are fertilised internally, a strategy unknown for decapodiform cephalopods (squid and cuttlefish), but present in most octopods. Fecundity of Heteroteuthis dispar (1,100–1,300 oocytes) is much higher than in other sepiolids whereas the egg size (mean max. length ∼1.6 mm) is the smallest within the family. Spawning is continuous (sensu Rocha et al. in Biol Rev 76:291–304, 2001). These and other reproductive traits are discussed as being adaptations to an oceanic lifestyle.     

Phylogeny of Opsanus spp. (Batrachoididae) inferred from multiple mitochondrial-DNA sequences

 Species of the toadfish genus Opsanus are increasingly used as experimental organisms in biomedicine and evolutionary/ecological physiology. Despite their importance, little is known of the phylogenetic relationships among Opsanus species. DNA sequence data for portions of the mitochondrial 12S rRNA, cytochrome oxidase I and cytochrome b genes were generated and analyzed from the four recognized Opsanus species and three outgroup taxa. Results of these analyses indicate an evolutionarily rapid divergence of three lineages within the genus. O. beta and O. pardus were resolved within the same lineage, and could not be distinguished with these mitochondrial sequence data. These data and paleoclimatic theory support a hypothesis of speciation based on the formation of allopatric populations during periods of elevated water temperature in the northern Caribbean. Received: 6 July 1999 / Accepted: 15 March 2000     

Species boundaries in the starfish genus Linckia

 The genetic basis for species boundaries in the starfish genus Linckia was examined using variation observed in 613 base pairs (bp) of sequence from the cytochrome oxidase I gene of mtDNA and 16 allozyme loci. Five groups within Linckia were clearly genetically differentiated; L. columbiae, L. bouvieri, two clades within L. guildingi, and one clade with two sub-clades consisting of both L. laevigata and L. multifora. Genetic divergence among these groups is consistent with interspecific variation. The two clades within L. guildingi suggest the presence of a cryptic, partially sympatric, species. Genetic divergence between these two clades implies that they have been genetically distinct from each other for at least one million years. In contrast, genetic data suggest that L. laevigata and L. multifora are a single species, despite the fact that live individuals can be distinguished by their colour and colour pattern, number of madreporites and ratio of arm length to breadth. There are probably three closely related groups within the L. laevigata/L. multifora clade –L. multifora, and two groups in L. laevigata defined by biogeographic province. It is difficult to determine boundaries for these three entities, since genetic and morphological differences are complicated by phenotypic differences arising from both environmental variation and population genetic structure. The difficulties encountered in defining species boundaries in Linckia, particularly with respect to variation arising from the overlap of Indian and Pacific biogeographic provinces, may be a general issue for many marine organisms from this region. Received: 24 May 1999 / Accepted: 6 October 1999     

Molecular phylogeny and evolution of the pelagic copepod genus Neocalanus (Crustacea: Copepoda)

Portions of the mitochondrial genome (ca. 4 kb), encoding three protein-coding (COI, ND4L, ND6) and two ribosomal RNA (srRNA, lrRNA) genes, were sequenced for all six currently recognized species, plus one form, of the pelagic calanoid copepod genus Neocalanus. In Neocalanus gracilis, the ND6 gene was not found in the sequenced portion of the mitochondrial genome. Unambiguously aligned sequences were subjected to Bayesian, maximum-likelihood, maximum-parsimony, and neighbor-joining analyses using Eucalanus bungii as an outgroup. The resultant tree topologies from these four methods were congruent, robust, and all nodes were supported by high bootstrap values and posterior probabilities of 92–100%. Two tropical and subtropical species (N. gracilis and N. robustior) occupied the most basal position, and a subantarctic (N. tonsus) and three subarctic Pacific species (N. cristatus, N. plumchrus, and N. flemingeri) diverged subsequently. Transequatorial dispersal of the ancestral population during glaciations is suggested for this pattern of speciation, in which sister clades exhibited antitropical distributions. Although the area of ocean is much broader in the subantarctic than the subarctic Pacific, a higher number of species occur in the subarctic Pacific (three) than the subantarctic (one). The possibility that marginal seas, such as Japan Sea and Okhotsk Sea, function as natal areas for the divergence of species is discussed.     

Genetic divergence and phylogenetic inferences in five species of Mugilidae (Pisces: Perciformes)

Allozyme electrophoresis was used to compare the genetic divergence of global populations of Mugil cephalus Linnaeus, 1758 and two congeneric [M.␣curema Cuvier & Valenciennes, 1836; M. gyrans (Jordan & Gilbert, 1885)] and two more distantly related [Liza ramada (Risso, 1826); Xenomugil thoburni (Jordan & Starks, 1896)] species on the basis of 18 enzyme loci. The amount of genetic divergence among the species examined is in agreement with their present systematic status, the differences being larger among non-congeneric species than among species of the same genus. Intraspecific genetic distances in M. cephalus (average Nei's D= 0.154), although higher than those reported for conspecific populations of fish, appear to be small when compared to the interspecific values among mugilid species (0.821 ≤ Nei's D ≤ 1.744). Phylogenetic trees obtained by genetic distance methods and discrete character parsimony analysis were of similar topology, except for the relationships within the genus Mugil and for the arrangement of M. cephalus populations. Received: 7 April 1997 / Accepted: 4 February 1998     

Reproductive patterns of scleractinian corals in the northern Red Sea

The majority of published accounts on scleractinian coral reproduction are from the tropical Pacific and Caribbean, with very little information known about Red Sea species. This report examines variation in reproductive mode in 24 species of hermatypic corals (belonging to seven families) in the Gulf of Eilat, Red Sea. Eighteen species are hermaphroditic broadcasters, two are hermaphroditic brooders and three are gonochoric broadcasters. In the Pocilloporidae, the gonads project into the body cavity, while in the other six families the gonads reside inside the mesenteries. The number of gonads per polyp in broadcasting species follows family or genus lines. Fecundity (eggs per polyp) increases with polyp size. Brooding species usually exhibit one or two gonads per polyp and each gonad contains only one to three oocytes. Oocyte size varies widely and does not relate to mode of reproduction. The largest oocytes (diameter = 450 μm) occur in the brooding coral Alveopora daedalea and in broadcasting species of the genus Acropora (diameter = 420 μm). Gonad morphology and gonochorism versus hermaphroditism appear to be constrained phylogenetically at the family or genus level. Lastly, this report compares the data presented for Red Sea scleractinian species with the data available on scleractinian corals from other geographical regions. Received: 2 February 1993 / Accepted: 9 March 1998     

Mitochondrial and nuclear rRNA based copepod phylogeny with emphasis on the Euchaetidae (Calanoida)

Phylogenetic relationships within the copepod family Euchaetidae and between representatives of three copepod orders (Calanoida, Harpacticoida, and Poecilostomatoida) were investigated using partial nucleotide sequences of the mitochondrial 16S rRNA and the nuclear 28S rRNA genes. DNA isolation, polymerase chain reaction, cloning, and DNA sequencing techniques were customized for these crustaceans. Our results support the monophyly of each copepod order, but in contrast to traditional morphology-based phylogenies of copepod orders, the Poecilostomatoida are basal to the Calanoida and Harpacticoida on our DNA-based phylogenetic tree. Phylogenetic trees generated by maximum parsimony, neighbor-joining, and maximum-likelihood analyses support the classification of the genera Euchaeta and Paraeuchaeta in the family Euchaetidae; results, however, suggest that Euchaetaacuta Giesbrecht is more closely related to species of the genus Paraeuchaeta than to those of Euchaeta, although limited taxon sampling may be partially responsible for this result. Phylogenetic mapping using the most parsimonious 16S tree suggests that the morphological synapomorphies distinguishing the genus Euchaeta evolved independently twice during the history of the Euchaetidae. Further, phylogenetic mapping suggests that the most recent common ancestor of the Euchaetidae and the Aetideidae was a deep-living, vertically migrating copepod, and that a bathypelagic, vertically migrating lifestyle characteristic of Paraeuchaeta is an ancestral trait of the family Euchaetidae which was lost apomorphically by Euchaeta. The application of a molecular clock suggests that the sibling species Euchaeta rimana Bradford and Euchaeta marina (Prestandrea) diverged due to the emergence of the Panamanian land bridge. Received: 9 October 1997 / Accepted: 5 August 1998     

Cryptic species and population structuring of the Atlantic and Pacific seabob shrimp species, Xiphopenaeus kroyeri and Xiphopenaeus riveti

Seabob shrimps of the genus Xiphopenaeus are important fishery resources along the Atlantic and Pacific coasts of Central and South America. The genus was considered to comprise two species: the Atlantic Xiphopenaeus kroyeri (Heller, Sitzungsber Math Naturwiss cl kaiserliche Akad Wiss Wien 45:389–426, 1862), and the Pacific Xiphopenaeus riveti (Bouvier, Bull Mus Hist Nat Paris 13:113–116, 1907). In a recent review, Xiphopenaeus was regarded as a monotypic genus, on the basis that no clear morphological differences could be found between Pacific and Atlantic specimens (Pérez Farfante and Kensley, Mem Mus Nat Hist Nat Paris 175:1–79, 1997). In the present work, nuclear (allozymes), and mitochondrial (Cytochrome Oxidase I) genes were used to demonstrate the validity of X. riveti and reveal the presence of two cryptic species of Xiphopenaeus within X. kroyeri in the Atlantic Ocean. The high levels of molecular divergence among these species contrast with their high morphological resemblance. Interspecific sequence divergences (Kimura 2-parameter distance) varied from 0.106 to 0.151, whereas intraspecific distances ranged from 0 to 0.008 in Xiphopenaeus sp. 1, from 0 to 0.003 in Xiphopenaeus sp. 2, and from 0.002 to 0.005 in X. riveti. In addition, five diagnostic allozyme loci were found between sympatric samples of Xiphopenaeus sp. 1 and 2 along the Brazilian coast. The results suggest that Xiphopenaeus sp. 2 from the Atlantic is more closely related to the Pacific X. riveti than to the Atlantic Xiphopenaeus sp. 1. Furthermore, a high level of genetic structuring (Xiphopenaeus sp. 1: F _ST =0.026; P<0.05; Xiphopenaeus sp. 2: F _ST =0.055; P<0.01) was found in the Brazilian Xiphopenaeus populations, indicating the presence of different genetic stocks in both Atlantic species. These findings have important commercial implications as they show that the fisheries of the two Atlantic species must be managed separately, and that each one is comprised of different populations.Communicated by O. Kinne, Oldendorf/Luhe     

Colonization of the northwest Atlantic by the blue mussel, <Emphasis Type="Italic">Mytilus trossulus</Emphasis> postdates the last glacial maximum

Blue mussels in the genus Mytilus first arrived in the Atlantic Ocean from the Pacific during the Pliocene, following the opening of the Bering Strait. Repeated periods of glaciation throughout the Pleistocene led to re-isolation of the two ocean basins and the allopatric divergence of Mytilus edulis in the Atlantic and M. trossulus in the Pacific. Mytilus trossulus has subsequently colonized the northwest Atlantic (NW Atlantic) so that the two species are presently sympatric and hybridize throughout much of the Canadian Maritimes and the Gulf of Maine. To estimate when M. trossulus arrived in the NW Atlantic, we have examined sequence variation within a portion of the female mtDNA lineage large untranslated region (F-LUR) for 156 mussels sampled from three Pacific and eleven Atlantic populations of M. trossulus. Although we found no evidence of reciprocal monophyly for Pacific and NW Atlantic M. trossulus, limited gene flow between ocean basins has led to the divergence of unique sequence clades within each ocean basin. In contrast, relative genetic homogeneity indicates high levels of gene flow within each basin. Coalescence-based analysis of the F-LUR sequences suggests that M. trossulus recolonized the NW Atlantic from the northeast Pacific subsequent to a demographic expansion in the Pacific that occurred ~96,000 years before present (ybp). Estimates of timing of divergence for Pacific and NW Atlantic populations and the time since expansion among NW Atlantic sequence clades indicate that M. trossulus arrived in the NW Atlantic more recently, between 20,000 and 46,000 ybp. Given that these estimates overlap with the dates of peak ice in the NW Atlantic during the last glacial maximum (LGM, ~18,000–21,000 ybp), we suggest that colonization of the NW Atlantic by M. trossulus occurred during, but more likely just subsequent to, the LGM and was followed by rapid temporal and spatial expansion in the region.     

First genetic validation and diagnosis of the short-finned squid species of the genus <Emphasis Type="Italic">Illex</Emphasis> (Cephalopoda: Ommastrephidae)

Squids of the genus Illex are representative of the family Ommastrephidae and account for 65% of the world’s cephalopod captures. Illex is formed by four taxa distributed throughout the Atlantic Ocean (I. argentinus, I. coindetii, I. illecebrosus and I. oxygonius), whose identification and phylogenetic relationships based on morphological characters remain controversial. Thirty-seven enzyme-coding loci were analysed in 230 individuals from seven populations of Illex and ten specimens of Todaropsis eblanae, which were used as the outgroup. Two to four enzyme loci (ALPDH*, IDHP-1*, MEP* and SOD*) were diagnostic among Illex species depending on the species-pair comparison. Individuals morphologically identified as I. oxygonius were also found genetically distinct, which proves the taxonomic validity of this species. No significant intraspecific genetic heterogeneity was detected within Illex argentinus, I. coindetii and I. illecebrosus (Mean G _ST= 0.011, 0.003, 0.017, respectively). I. illecebrosus and I. oxygonius were shown as sister species with a close relationship to I. argentinus, whereas I. coindetii formed a different lineage.     

Incipient speciation within a subgenus of rockfish (<Emphasis Type="Italic">Sebastosomus</Emphasis>) provides evidence of recent radiations within an ancient species flock

The high frequency of speciation events associated with species flocks (i.e., radiations of closely related species) provides invaluable insight into the speciation process. Investigations of the speciation process in the marine environment are rare, and therefore, the genetic analysis of the rockfish genus Sebastes, considered an ancient marine species flock, provides an opportunity to investigate this process in the sea. Using both mitochondrial and nuclear markers, we analyzed five closely related species within the rockfish subgenus Sebastosomus. Our goal was to understand the evolutionary history and genetic relationships among species within this group and to provide evidence of recent speciation events within the subgenus. In the genetic analysis of the subgenus, we found different stages of the speciation process, with greater genetic divergences among three of the five species, evidence of recent divergence between two of the five species, Sebastes entomelas and S. mystinus, and significant genetic divergence between two lineages within S. mystinus revealing a signature of incipient speciation. We also found frequency differences of the two S. mystinus lineages among sample locations and found no evidence of introgression between the lineages at the location where both coexist. Although Sebastes is an example of an ancient species flock, this study provides evidence of ongoing speciation within the genus and reveals stages of this process from incipient to distinct species.     

Variation in larval life-history traits among reef fishes across the Isthmus of Panama

We tested the hypothesis that regional differences in oceanic productivity have led to the evolution of predictable patterns of regional variation in life-history traits of pelagic larvae of tropical reef fishes. To do so we compared larval traits (egg and hatchling size, larval growth rate and duration, and size at settlement) among closely related reef fishes from the Atlantic and Pacific coasts of the Isthmus of Panama. This comparison provides a control for phylogenetic effects because those regions shared a common fauna prior to the rise of the Isthmus ˜3.5 million years ago, subsequent to which each fauna evolved independently under a very different productivity regime. We measured larval traits of 12 benthic-spawning damselfishes (Pomacentridae: Abudefduf, Chromis and Stegastes) and 13 pelagic-spawning wrasses (Labridae: Bodianus, Halichoeres and Thalassoma). These included members of each genus on each side of the Isthmus and four sets of transisthmian sister species of pomacentrids. Among the pomacentrids we found consistent transisthmian differences in hatchling size, but not in other larval traits. Essentially the reverse pattern occurred among the labrids – larval growth and duration differed consistently among congeners in the two regions, but without consistent differences in hatchling size or size at settlement. Neither relationship is predicted by the regional-productivity hypothesis. Most of the differences were quite small. Stronger phylogenetic effects on larval traits (inter- and intrageneric variation within regions) occur in both families and evidently overwhelm any effect of regional variation in productivity. Reassessment of data that takes into account such phylogenetic effects questions previous conclusions about the existence of regional differences in larval traits among damselfishes in the West Pacific and the Caribbean. Received: 19 January 2000 / Accepted: 26 September 2000     

Optical–digital system applied to the identification of five phytoplankton species

An optical–digital system was used to identify five phytoplankton species of the genus Ceratium from Todos Santos Bay off the California Peninsula, Mexico. The system recognized species with at least 90% accuracy, regardless of their size, rotation, or location within the field of view. An optical filter was constructed for each species for correlation with each of six test images. The test images were prepared from phytoplankton samples containing one or more of the five species. The correlations demostrate that each optical filter recognized its corresponding species. To evaluate the effectiveness of the correlation technique, we used images of 100 different samples. The species of the Ceratium genus analyzed are important indicators, since some are responsible for red-tide blooms in areas surrounding Todos Santos Bay, Baja California, Mexico. In the near future, based on the method proposed, we plan to implement an automated plankton-identification system to determine marine eco-biological properties. Received: 9 June 1997 / Accepted: 3 June 1998     

Evolution of reproductive features and larval development in the genus Amphiglena (Polychaeta: Sabellidae)

Larval development in Amphiglena mediterranea is direct in the parental tube, and larvae crawl away as young juveniles with a radiolar crown capable of feeding. The non-feeding larvae of A. nathae are initially brooded in the parental tube, and then have a swimming phase before settling and developing a radiolar crown. Developmental data and reproductive features such as sperm structure are combined with other morphological data for an assessment of the cladistic relationships of the species in the genus Amphiglena. Two species of Laonome are included as part of the ingroup. Six genera, representing a sister group to the Laonome/Amphiglena clade, are used as an outgroup. Two most-parsimonious cladograms were found, and the evolution of reproductive features are discussed. The monophyly of Amphiglena is indicated by features previously identified, as well as two features based on sperm morphology. At present a plesiomorphic larval form cannot be identified for the genus Amphiglena. Received: 16 June 1997 / Accepted: 29 January 1998     

Arsenic accumulation by ferns: a field survey in southern China

The objective of this study reported here was to characterize arsenic (As) accumulation by Pteris ferns by comparing 3 of the ferns of this genus with each other as well as with four non-Pteris ferns growing on seven sites in southern China with different As levels. A total of 112 samples, including 78 Pteris vittata, 13 P. cretica, 3 P. multifida and 18 ferns from other non-Pteris genera, with the soils in which they grew were collected for As and other elemental analyses. P. vittata was found to be the most dominant species and the most efficient As-accumulator, whereas P. multifida was the lowest As-accumulator among the Pteris ferns, with 4.54–3599, 28.7–757 and 11.2–341 mg kg^–1 As recorded in the fronds of P. vittata, P. cretica and P. multifida, respectively. Arsenic concentrations in non-Pteris ferns were generally much lower than those in Pteris ferns, with 0.81–1.32, 3.59, 10.7, 6.17–24.3 mg kg^–1 in the fronds of Blechumum orientale, Dicranopteris dichotoma, Pteridium aquilinum and Cyclosorus acuminatus, respectively. For P. vittata, the As bioaccumulation factor (ratio of As in fronds to that in soils) changed, whereas the As translocation factor (ratio of As in fronds to that in roots) remained unchanged among the different sites. The concentrations of Fe were very high in all of the collected fern sample, with the exception of B.␣orientale, with 207–6865, 637–3369, 375–1856, 1876, 493-6865 and 492 mg kg^–1 in the fronds of P. vittata, P. cretica, P. multifida, C. acuminatus, P. aquilinum and D. dichotoma, respectively. The association between Fe accumulation and As accumulation and tolerance in these ferns indicates the unique role of Fe in As-hyperaccumulation.