Molecular diversity of fungal phylotypes co-amplified alongside nematodes from coastal and deep-sea marine environments

Nematodes and fungi are both ubiquitous in marine environments, yet few studies have investigated relationships between these two groups. Microbial species share many well-documented interactions with both free-living and parasitic nematode species, and limited data from previous studies have suggested ecological associations between fungi and nematodes in benthic marine habitats. This study aimed to further document the taxonomy and distribution of fungal taxa often co-amplified from nematode specimens. A total of 15 fungal 18S rRNA phylotypes were isolated from nematode specimens representing both deep-sea and shallow water habitats; all fungal isolates displayed high pairwise sequence identities with published data in Genbank (99-100%) and unpublished high-throughput 454 environmental datasets (>95%). BLAST matches indicate marine fungal sequences amplified in this study broadly represent taxa within the phyla Ascomycota and Basidiomycota, and several phylotypes showed robust groupings with known taxa in phylogenetic topologies. In addition, some fungal phylotypes appeared to be present in disparate geographic habitats, suggesting cosmopolitan distributions or closely related species complexes in at least some marine fungi. The present study was only able to isolate fungal DNA from a restricted set of nematode taxa; further work is needed to fully investigate the taxonomic scope and function of nematode-fungal interactions.     

Global diversity of nematodes (Nematoda) in freshwater

Despite free-living nematodes being present in all types of limnetic habitats including unfavorable conditions that exclude many other meiobenthic invertebrates, they received less attention than marine and terrestrial forms. Two-fifths of the nematode families, one-fifth of the nearly 1800 genera and only 7% of the about 27,000 nominal species are recorded from freshwater habitats. The Dorylaimia are the most successful in freshwater habitats with nearly two-thirds of all known freshwater nematodes belonging to this subclass. Members of the subclass Enoplia are principally marine though include some exclusively freshwater taxa with extreme endemism. The subclass Chromadoria includes half of the freshwater nematode families and members of the Monhysterida and Plectida are among the most widely reported freshwater nematodes. Studies on freshwater nematodes show extreme regional bias; those from the southern hemisphere are extremely underrepresented, especially compared to European freshwater bodies. The majority of records are from a single biogeographic region. Discussion on nematode endemism is largely premature since apart from Lake Baikal, the nematofauna of ancient lakes as centers of speciation is limited and recent discoveries show high nematode abundance and diversity in cryptic freshwater bodies, underground calcrete formations and stromatolite pools potentially with a high number of new taxa. Guest editors: E.V. Balian, C. Lèvêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Invasive plants and their escape from root herbivory: a worldwide comparison of the root-feeding nematode communities of the dune grass <Emphasis Type="Italic">Ammophila arenaria</Emphasis> in natural and introduced ranges

Invasive plants generally have fewer aboveground pathogens and viruses in their introduced range than in their natural range, and they also have fewer pathogens than do similar plant species native to the introduced range. However, although plant abundance is strongly controlled by root herbivores and soil pathogens, there is very little knowledge on how invasive plants escape from belowground enemies. We therefore investigated if the general pattern for aboveground pathogens also applies to root-feeding nematodes and used the natural foredune grass Ammophila arenariaas a model. In the late 1800s, the European A. arenariawas introduced into southeast Australia (Tasmania), New Zealand, South Africa, and the west coast of the USA to be used for sand stabilization. In most of these regions, it has become a threat to native vegetation, because its excessive capacity to stabilize wind-blown sand has changed the geomorphology of coastal dunes. In stable dunes of most introduced regions, A. arenaria is more abundant and persists longer than in stabilized dunes of the natural range. We collected soil and root samples and used additional literature data to quantify the taxon richness of root-feeding nematodes on A.␣arenaria in its natural range and collected samples from the four major regions where it has been introduced. In most introduced regions A. arenaria did not have fewer root-feeding nematode taxa than the average number in its natural range, and native plant species did not have more nematode taxa than the introduced species. However, in the introduced range native plants had more feeding-specialist nematode taxa than A. arenaria and major feeding specialists (the sedentary endoparasitic cyst and root knot nematodes) were not found on A. arenaria in the southern hemisphere. We conclude that invasiveness of A. arenaria correlates with escape from feeding specialist nematodes, so that the pattern of escape from root-feeding nematodes is more alike escape from aboveground insect herbivores than escape from aboveground pathogens and viruses. In the natural range of A. arenaria, the number of specialist-feeding nematode taxa declines towards the margins. Growth experiments are needed to determine the relationship between nematode taxon diversity, abundance, and invasiveness of A. arenaria.     

Gradients of salinity stress, environmental stability and water chemistry as a templet for defining habitat types and physiological strategies in inland salt waters

The search for pattern in the geographic occurrence of salt lake flora and fauna often reveals strong associations of specific taxa with certain types of water chemistry. Solute composition, along with salinity and habitat stability, may provide a templet shaping the distribution of many organisms inhabiting saline lakes. A review of studies demonstrating habitat associations, specific solute tolerance, and ionic and osmotic adaptations provide evidence of fidelity to particular conditions of environmental chemistry across a wide taxonomic spectrum. Under low salinity conditions, some species show osmoregulatory adaptability to varied solute composition but the capacity for such flexibility is reduced with increased salinity and only certain taxa are found in hypersaline waters dominated by a particular solute. Anionic ratios of chloride, bicarbonate–carbonate, and sulfate appear to be especially important determinants of distribution. Specific solute tolerance presents an alternative explanation to disrupted hydrographic connections in describing how biogeographic distributions may be restricted to certain aquatic habitats in arid regions. Physiological adaptations to chemistry, exemplified in the brine fly genus Ephydra, may be an integral part of the evolution, ecology and diversification of saline water organisms.     

Free-living marine nematodes from San Julián Bay (Santa Cruz,Argentina)

The free-living marine nematodes of San Julián Bay dataset is based on sediment samples collected in January 2009 during the project PICT AGENCIA-FONCYT 2/33345-2005. A total of 36 samples have been taken at three locations in the San Julián Bay, Santa Cruz Province, Argentina on the coastal littoral at three tidal levels. This presents a unique and important collection for the nematode benthic biodiversity assessment as this area remains one of the least known regions in Patagonia. In total 10,030 specimens of free-living marine nematodes belonging to 2 classes, 9 orders, 35 families, 78 genera and 125 species were collected. The San Julián city site presented a very high species richness.     

Phylogenetic inference in Odontesthes and Atherina (Teleostei: Atheriniformes) with insights into ecological adaptation

This contribution provides an insight into Atheriniformes systematics based on four mitochondrial regions: 12S rRNA, cytb, COI and control region (2794bp in total). In the Atherinopsoidei (New World silversides), comparisons among five species of Odontesthes, O. argentinensis, O. bonariensis, O. smitti, O. hatcheri and O. incisa revealed a putative marine-freshwater pairing pattern of Odontesthes species, possibly driven by sea level fluctuations of South American waters. This study represents the first data on molecular phylogeny of Odontesthes species that can be of usefulness to biodiversity conservation policies. In the Atherinoidei (Old World silversides), Atherina boyeri was corroborated as a species complex constituted by a marine form, a marine with dark spots form and a brackish form. Concretely, Odontesthes and Atherina may represent geographically replicated models to study genetic adaptation and speciation of marine species to brackish and freshwater habitats. In addition, phylogenetic analyses supported Odontesthes and Atherina as monophyletic taxa and their separation into two differentiated suborders Atherinopsoidei and Atherinoidei, respectively.     

Climate warming may cause a parasite-induced collapse in coastal amphipod populations

Besides the direct impact on the general performance of individual organisms, the ecological consequences of climate change in terrestrial and marine ecosystems are expected to be determined by complex cascading effects arising from modified trophic interactions and competitive relationships. Recently, the synergistic effect of parasitism and climate change has been emphasised as potentially important to host population dynamics and community structure, but robust empirical evidence is generally lacking. The amphipod Corophium volutator is an ecologically important species in coastal soft-bottom habitats of the temperate North Atlantic, and commonly serves as host to microphallid trematodes that cause intensity-dependent and temperature-dependent mortality in the amphipod population. Using a simulation model parameterised with experimental and field data, we demonstrate that a 3.8°C increase in ambient temperature will likely result in a parasite-induced collapse of the amphipod population. This temperature increase is well within the range predicted to prevail by the year 2075 in the International Wadden Sea region from where the model data are obtained. Due to the amphipods’ ecological importance, their population decline may impact the coastal ecosystem as a whole.     

Contributions of Robert (Bob) J. O’Neil to the field of predaceous Heteroptera

Predaceous Heteroptera are important components of natural and managed habitats. The extent of predatory habits among taxa ranges from those that are totally (or nearly totally) predaceous to those that are nearly totally phytophagous, but occasionally feed on arthropod prey. Because of that variability in predatory habit, the contributions of heteropteran taxa to management of pest species will vary greatly. The late Robert (Bob) J. O’Neil (1955–2008) added significantly to understanding the roles of and benefits from facultatively predaceous Heteroptera. His focus on behavioral and physiological attributes that permitted facultatively predaceous species to persist in agricultural habitats demonstrated that facultative predators could help prevent pest outbreaks, but were less effective at reducing numbers of species already considered above economic thresholds.     

A brief review of the fossil history of the family Rosaceae with a focus on the Eocene Okanogan Highlands of eastern Washington State, USA, and British Columbia, Canada

Many of the oldest definitive members of the Rosaceae are present in the Eocene upland floras of the Okanogan Highlands of northeastern Washington State and British Columbia, Canada. Over a dozen rosaceous taxa representing extant and extinct genera of all four traditionally recognized subfamilies are known from flowers, fruits, wood, pollen, and especially leaves. The complexity seen in Eocene Rosaceae suggests that hybridization and polyploidy may have played a pivotal role in the early evolution of the family. Increased species diversity and the first appearance of additional modern taxa occur during the Late Paleogene in North America and Europe. The Rosaceae become increasingly important components of fossil floras during the Neogene, with taxa adapted to many habitats.     

Lake Superior: an invasion coldspot?

Lake Superior receives a disproportionate number of ballast water discharges from transoceanic ships operating on the Laurentian Great Lakes. Although this provides dispersal opportunities for nonindigenous species (NIS), relatively few NIS were initially discovered in this lake prior to being recorded elsewhere in the basin. A lack of NIS records from this lake may be an artefact of sampling bias. We tested this hypothesis by sampling benthos and plankton from littoral and deepwater habitats around the perimeter of Lake Superior during June and August 2001. Using morphological analysis techniques, we identified a total of 230 invertebrate taxa representing planktonic, benthic and nektonic lifestyles. Five species with invasion histories in the lower Great Lakes, the bivalves Sphaerium corneum, Pisidium amnicum and P. moitessierianum, gastropod Potamopyrgus antipodarum and amphipod Echinogammarus ischnus, were identified for the first time in Lake Superior. In addition, records of expanded distributions within this lake are presented for the amphipod Gammarus fasciatus and oligochaetes Ripistes parasita and Vejdovskyella intermedia. Recently introduced NIS in Lake Superior were found near international ports, implicating shipping as the vector of their introduction. Intrinsic physical-chemical aspects of Lake Superior may account for the scarcity of NIS in this lake as compared to the lower Great Lakes.     

Diet of age-0 tarpon (<Emphasis Type="Italic">Megalops atlanticus</Emphasis>) in anthropogenically-modified and natural nursery habitats along the Indian River Lagoon,Florida

As human development in coastal areas increases, the role of anthropogenically-created habitats in the life history of marine organisms is becoming increasingly important. We examined the diet of age-0 tarpon, Megalops atlanticus, in and around man-made mosquito control impoundments along the Indian River Lagoon in east-central Florida, with a particular focus on identifying dietary patterns associated with tarpon size and nursery habitat type (i.e., between perimeter pool habitats in established impoundments and newly-created restoration marsh habitats). Age-0 tarpon were found to consume a wide variety of prey organisms, and exhibited considerable dietary variation among study sites. Smaller juvenile tarpon consumed a limited number of small prey taxa, while larger individuals fed on a greater range of prey taxa and sizes. Overall, copepods and fishes were the dominant prey items; however, the consumption of these organisms varied considerably among size classes and sites. There was no clear difference in tarpon diet between the two types of habitat we examined. The ability of juvenile tarpon to utilize such a diverse range of prey organisms may allow populations to inhabit a variety of habitats, including man-made marshes. When natural systems have been degraded or destroyed, human-altered habitats can assume a nursery role for the species.     

Large-scale species-richness gradients in the Atlantic Ocean

The increase in species richness from the poles to the Equator has been observed in numerous terrestrial and aquatic taxa. A number of different hypotheses have been put forward as explanations for this trend, e.g. area and energy availability. However, whether these hypotheses apply to large spatial scales in marine environments remains unclear. The present study shows a clear latitudinal gradient from high to low latitude (from 80 degrees N to 70 degrees S) in marine species richness for 6643 species (fishes and invertebrates) in 10 different taxa dwelling in benthic and pelagic habitats on both sides of the Atlantic. The patterns in benthic taxa are strongly influenced by coastal hydrographic processes, with marked peaks and troughs, and consequently the gradients are not symmetric along both Atlantic sides. Pelagic taxa show a plateau-shaped distribution and the influence from coastal events on gradients could not be demonstrated. The relationships between species richness and different environmental factors indicate that area size does not explain the latitudinal pattern in benthic species richness on a large spatial scale. Sea-surface temperature (positive relationship) is the best predictor of this pattern for benthic species, and nitrate concentration (negative relationship) is the best predictor for pelagic species. The results call into question the existence of a single primary cause that would explain the pattern in marine species richness on a large spatial scale.     

The benthic macroinvertebrate community in a coastal sand dune lake relative to habitat and changing lake levels

The benthic macroinvertebrate community (BMI) in a freshwater coastal dune lake without a surface outlet was investigated in May and October, 1986. Fifty-three invertebrate taxa were identified from Carter Lake, including three euryhaline crustacean species (Corophium spinicorne, Gnorimosphaeroma oregonensis lutea, and Acanthomysis awatchensis). Corophium spinicorne dominated the BMI communities of the littoral zones and sphaeriid clams dominated the deepwater community.The lake level dropped about 2.5 m between April and October. Based upon this decline, the lake bottom was divided into four major habitats: a sandy temporarily submerged littoral zone (A); a sandy submerged littoral zone (B); and mid-depth zone of mixed mud and sand and the macrophyte, Nitella (C); and a deep zone (D) with soft mud. The average density of BMI was highest in the littoral zones (A and B) in May and in zone B in October (zone A was dry). The lowest density occurred in zone D. In May, BMI biomass was highest in the littoral zones, but the biomass was highest in the mid-depth zone in October. The mid-depth zone in October. The mid-depth zone had the most diverse community.The two most abundant species in the temporarily submerged area, Corophium spinicorne and Juga plicifera, were found in greater numbers deeper in the lake after the water level dropped, suggesting migration by these species in response to changing water levels.     

Enregistrement des fluctuations du niveau marin dans l’Holocène supérieur du lac Retba (Sénégal) par les foraminifères

A study of sea level fluctuation records based on foraminiferal assemblages was carried out for the first time in a sediment core taken at the Lac Retba edge. A total of 37 foraminifera species were collected along the core, among which most are known in the modern estuaries and lagoons of Senegal. A succession of four assemblages dominated by Ammonia parkinsoniana and A. tepida were identified; they correspond to different stages of evolution of the lake. The first association, at the base of the core, indicates a lagoon slightly opened to the sea and bordered with vegetation, under relatively humid climate. The second has the richest and most diversified microfauna with a high proportion of coastal, marine benthic and planktonic species (about 10%) that indicate a small coastal gulf bordered with mangroves. The third association is oligospecific and typical of a closed and hypersaline lagoon under a dry climate. The last association again contains coastal, marine benthic and scarce planktonic species (3%) indicating a change to a saltier and more open lagoon under dry climate. The disappearance of planktonic foraminifera at the top of the core indicates the closure of the lagoon. The biocenotic indicators are evidence for two marine intrusions that are referred to the Dakarian (3000 years B.P.) and Saint-Louisian (2140-680 years B.P.) stages of the Upper Holocene of the senegalo-mauritanian stratigraphic scale. Evidence of the Lac Retba closure since 680 years B. P. appears in the core by high reduction of foraminifers’ abundance and diversity absence of planktonic species, and salts precipitated at the bottom of the lake.     

The icthyofauna of the Mhlathuze coastal lakes: some preliminary results

The fish faunas of the four Mhlathuze coastal lakes and the lower river comprise a diverse assortment of over fifty marine, estuarine and freshwater species. Three freshwater species are endemic to KwaZulu-Natal and nine estuarine species are endemic to southern Africa. Five species are of conservation significance. Species numbers in Lakes Mzingazi and Cubhu are similar historically and both lakes served as secondary nursery habitats for estuarine associated fishes. This role has been impacted by the construction of weirs at their outlets which prevent successful recruitment of estuarine species, especially during drought years when lake water levels are low. The fish faunas of Lakes Nsezi and Mangeza are depauperate and lack marine or estuarine components. In order that these systems fulfil their potential function as secondary nursery habitats to many estuarine fish species, minimum lake water levels must be set to ensure sufficient outflows at proposed fish ladders during critical spawning and migration times.     

Evidence of concurrent local adaptation and high phenotypic plasticity in a polar microeukaryote

Here we investigated whether there is evidence of local adaptation in strains of an ancestrally marine dinoflagellate to the lacustrine environment they now inhabit (optimal genotypes) and/or if they have evolved phenotypic plasticity (a range of phenotypes). Eleven strains of Polarella glacialis were isolated and cultured from three different environments: the polar seas, a hyposaline and a hypersaline Antarctic lake. Local adaptation was tested by comparing growth rates of lacustrine and marine strains at their own and reciprocal site conditions. To determine phenotypic plasticity, we measured the reaction norm for salinity. We found evidence of both, limited local adaptation and higher phenotypic plasticity in lacustrine strains when compared with marine ancestors. At extreme high salinities, local lake strains outperformed other strains, and at extreme low salinities, strains from the hyposaline lake outperformed all other strains. The data suggest that lake populations may have evolved higher phenotypic plasticity in the lake habitats compared with the sea, presumably due to the high temporal variability in salinity in the lacustrine systems. Moreover, the interval of salinity tolerance differed between strains from the hyposaline and hypersaline lakes, indicating local adaptation promoted by different salinity.     

Phylogeny of Chaetanthera (Asteraceae: Mutisieae) reveals both ancient and recent origins of the high elevation lineages

Penalized likelihood analysis of previously published chloroplast DNA (cpDNA) ndhF sequences suggests that the central-southern Andean genus Chaetanthera diverged ca. 16.5 million years (my) ago, well before the uplift of the Andes to their present heights. Penalized likelihood analysis based on new nuclear ribosomal DNA (rDNA) internal transcribed spacer (ITS) sequences indicates that the most relictual lineages occupy high elevation Andean habitats that did not exist until some 10my later. This result is contrary to the expectation that younger habitats should be occupied by phylogenetically younger lineages. The results are interpreted with respect to the development of aridity in lowland habitats during the Miocene and Pliocene, which presumably extinguished the lowland relatives of the high elevation taxa or, in effect, forced them upwards in search of adequate moisture. As the more northerly lineages were being displaced upward, others diversified in the mediterranean-type climate area of central Chile, giving rise to additional high elevation taxa again, at an early date, as well as lowland taxa. Some species of Chaetanthera from lowland central Chile appear as the phylogenetically youngest taxa, suggesting secondary adaptation to lowland aridity. At the same time, at least two high elevation species, Chaetanthera peruviana and Chaetanthera perpusilla, appear to have been derived recently from a lower elevation ancestor, while some middle to low elevation taxa seem to have evolved recently out of a high elevation complex. The results suggest that the younger high elevation habitats have served as both "cradle" and "museum" for Chaetanthera lineages.     

Ancient lakes as hotspots of diversity: a morphological review of an endemic species flock of <Emphasis Type="Italic">Tylomelania</Emphasis> (Gastropoda: Cerithioidea: Pachychilidae) in the Malili lake system on Sulawesi,Indonesia

The viviparous freshwater gastropod Tylomelania (Caenogastropoda: Cerithioidea: Pachychilidae) endemic to the Indonesian island Sulawesi has radiated extensively in two ancient lake systems. We here present the first systematic species-level review of taxa in the five lakes of the Malili lake system, which contains the most diverse and best studied freshwater fauna on Sulawesi. Our results indicate a significantly higher diversity of Tylomelania in these lakes than previously perceived based on morphological evidence for delimiting the taxa. We describe nine new species, thus increasing the number of taxa known from the Malili lakes to 25. Tylomelania species are inhabiting all available substrates in the lakes, and the diversity of habitats is reflected in an unparalleled range of radula types in this closely related group. Several species show a high intraspecific variability in some characters, and their closer investigation will probably lead to the discovery of more cryptic species. As it is, this species flock on Sulawesi is among the largest freshwater mollusc radiations known. Since the Malili lake system also contains other large endemic species flocks of e.g. crustaceans and fishes, it is a major hotspot of freshwater biodiversity in Asia to become a conservation priority. Handling editor: K. Martens