Mesophotic reef fish assemblages of the remote St. Peter and St. Paul’s Archipelago,Mid-Atlantic Ridge,Brazil

Mesophotic reef fish assemblages (30–90 m depth) of the small and remote St. Peter and St. Paul’s Archipelago (SPSPA), Mid-Atlantic Ridge, Brazil, were characterized using remotely operated vehicles. Ordination analyses identified distinct fish assemblages in the upper (30–50 m) and lower (50–90 m) mesophotic zones, the former characterized by high abundances of species that are also abundant at euphotic reefs (Caranx lugubris, Melichthys niger, Stegastes sanctipauli and Chromis multilineata) and the latter dominated by two mesophotic specialists (Prognathodes obliquus and Chromis enchrysura). Planktivores dominated fish assemblages, particularly in the upper mesophotic zone, possibly due to a greater availability of zooplankton coming from the colder Equatorial Undercurrent in mesophotic depths of the SPSPA. Turf algae, fleshy macroalgae and scleractinian corals dominated benthic assemblages between 30 and 40 m depth, while bryozoans, black corals and sponges dominated between 40 and 90 m depth. Canonical correspondence analysis explained 74 % of the relationship between environmental characteristics (depth, benthic cover and complexity) and structure of fish assemblages, with depth as the most important independent variable. Juveniles of Bodianus insularis and adults of P. obliquus and C. enchrysura were clearly associated with branching black corals (Tanacetipathes spp.), suggesting that black corals play key ecological roles in lower mesophotic reefs of the SPSPA. Results from this study add to the global database about mesophotic reef ecosystems (MREs) and provide a baseline for future evaluations of possible anthropogenic and natural disturbances on MREs of the SPSPA.     

Application of diet theory reveals context-dependent foraging preferences in an herbivorous coral reef fish

Dietary preferences of grazers can drive spatial variability in top-down control of autotroph communities, because diet composition may depend on the relative availability of autotroph species. On Caribbean coral reefs, parrotfish grazing is important in limiting macroalgae, but parrotfish dietary preferences are poorly understood. We applied diet-switching analysis to quantify the foraging preferences of the redband parrotfish (Sparisoma aurofrenatum). At 12 Caribbean reefs, we observed 293 redband parrotfish in 5-min feeding bouts and quantified relative benthic algal cover using quadrats. The primary diet items were macroalgal turfs, Halimeda spp., and foliose macroalgae (primarily Dictyota spp. and Lobophora spp.). When each resource was evaluated independently, there were only weak relationships between resource cover and foraging effort (number of bites taken). Electivity for each resource also showed no pattern, varying from positive (preference for the resource) to negative (avoidance) across sites. However, a diet-switching analysis consisting of pairwise comparisons of relative cover and relative foraging effort revealed clearer patterns: parrotfish (a) preferred Halimeda and macroalgal turfs equally, and those two resources were highly substitutable; (b) preferred Halimeda to foliose macroalgae, but those two resources were complementary; and (c) also preferred turf to foliose macroalgae, and those resources were also complementary. Thus parrotfish grazing rates depend on relative, not absolute, abundance of macroalgal types, due to differences in substitutability among resources. Application of similar analyses may help predict potential changes in foraging effort of benthic grazers over spatial gradients that could inform expectations for reef recovery following the protection of herbivore populations.     

Influence of environmental variables on the larval stages of anchovy, <Emphasis Type="Italic">Engraulis encrasicolus</Emphasis>, and sardine, <Emphasis Type="Italic">Sardinops sagax</Emphasis>, in Algoa Bay,South Africa

We investigated the environmental drivers of larval abundance of anchovy Engraulis encrasicolus and sardine Sardinops sagax in Algoa Bay, Eastern Cape (South Africa). This study comprised a pre-drought post-drought time period, comparing the responses of the fish larvae to different factors before and after the drought. The current study presents, for the first time, which environmental variables are affecting the anchovy and sardine larvae populations in the region. Easterly wind speed and zooplankton density were the only environmental variables that presented a significant change between the pre- and post-drought periods, increasing after the drought. Generalized additive models (GAMs) were used in order to explore the effects that environmental factors might have in the abundance of anchovy and sardine larvae in Algoa Bay. Specifically, the GAM that best explained the deviance of the anchovy larvae dynamics included the covariates rainfall, easterly wind speed, Chl a concentration, sardine larvae abundance and the interactions SST*Chla and sard*SST. The GAM best explaining sardine larvae abundance included only the easterly wind speed as a covariate. This model showed that there was a positive relationship between the higher values of wind speed and sardine larvae abundance.     

Does Type of Substratum Affects Chironomid Larvae Assemblage Composition? A Study in a River Catchment in Northern Patagonia,Argentina

Chironomid larvae assemblages were investigated at seven sampling stations in relation to stream habitat type in the Challhuaco-Ñireco river system located in the Nahuel Huapi National Park, in the North-Western part of Rio Negro Province, Argentina. A total of 2229 individuals were sampled and 43 Chironomidae taxa were recorded with Orthocladiinae (29) being the best represented subfamily, followed by Diamesinae (5), Tanypodinae (3), Podonominae (3) and Chironominae (3). Stictocladius spF, Cricotopus (Paratrichocladius) sp6, Cricotopus sp2, Cricotopus sp3 and Parapsectrocladius sp2 were the most abundant taxa. Sites near the source of the river system were dominated by Podonomus sp., Limnophyes sp., Parapsectrocladius sp. and Stictocladius spF, whereas sites close to the river mouth were dominated by Diamesinae sp5 and Cricotopus sp. Rank/abundance plots show that all the analysed sites displayed dominance of some species. Stictocladius spF, Cricotopus sp2, Cricotopus sp3, Cricotopus (Paratrichocladius) sp6, Parapsectrocladius sp. and Limnophyes sp. resulted as dominant species, or being part of a group of dominant species, at least in one sample. Eleven taxa were associated with habitats related with riffle areas and stable substrates with filamentous algae. Species–environment relationships were examined using ordination analysis. Elevation was the most significant environmental variable that explained 22% of the total variability of the chironomid assemblages, showing stronger relationships among sites within an altitudinal gradient than among habitat type. Abundance of chironomids increased from headwaters to the outflow in Nahuel Huapi Lake responding to an altitude gradient as well as some environmental factors such as coarse matter and nutrient concentrations.     

Water mite (Acari: Hydrachnidia) diversity and distribution in undisturbed Dinaric karst springs

Large undisturbed karst springs in the Dinaric region are particularly interesting and extremely valuable and rare ecosystems, housing diverse and yet undiscovered water mite species. The complex life history traits of water mites include several life stages that are interconnected with other freshwater arthropod groups, making them important components of freshwater fauna. This study examined whether the differences in water mite assemblages between Mediterranean and alpine karst springs were driven by seasonal and/or regional changes in environmental conditions. The first ecological data on water mite dynamics and distribution in the Dinaric region of Croatia are presented. Water mites were represented by 11 taxa, decreasing in taxon richness from alpine to Mediterranean springs. Spatial patterns of water mite assemblages at the regional scale were best explained by water temperature, dissolved oxygen and water velocity. Pseudotorrenticola rhynchota and Oxus setosus were exclusively found in springs with higher water temperature and velocity, whereas the genera Aturus sp. and Woolastookia rotundifrons were exclusively recorded in the alpine springs, where oxygen concentrations were significantly higher. Atractides sp., Lebertia sp. and Sperchon sp. were recorded in most springs. Water mite abundances had a summer peak in the Mediterranean region, whereas two smaller peaks were observed in the spring and fall in the alpine region. Regional differences in the seasonality of water mite abundance were most likely patterned by the emergence of insect crenofauna.     

Human-Imposed,Fine-Grained Patch Burning Explains the Population Stability of a Fire-Sensitive Conifer in a Frequently Burnt Northern Australia Savanna

Woody plant demographics provide important insight into ecosystem state-shifts in response to changing fire regimes. In Australian tropical savannas, the switch from patchy landscape burning by Aborigines to unmanaged wildfires within the past century has been implicated in biodiversity declines including the fire-sensitive conifer, Callitris intratropica. C. intratropica commonly forms small, closed-canopy groves that exclude fire and allow recruitment of conspecifics and other fire-sensitive woody plants. C. intratropica groves provide a useful indicator of heterogeneity and fire regime change, but the mechanisms driving the species’ persistence and decline remain poorly understood. We examined the hypothesis that C. intratropica population stability depends upon a regime of frequent, low-intensity fires maintained by Aboriginal management. We combined integral projection models of C. intratropica population behaviour with an environmental state change matrix to examine how vital rates, grove dynamics and the frequency of high- and low-intensity fires contribute to population stability. Closed-canopy C. intratropica groves contributed disproportionately to population growth by promoting recruitment, whereas singleton trees accounted for a larger proportion of adult mortality. Our patch-based population model predicted population declines under current fire frequencies and that the recruitment of new groves plays a critical role in the species’ persistence. Our results also indicated that reducing fire intensity, a key outcome of Aboriginal burning, leads to C. intratropica population persistence even at high fire frequencies. These findings provide insight into the relationship between ecosystem composition and human–fire interactions and the role of fire management in sustaining the mosaics that comprise ‘natural’ systems.     

Long-term dynamics of orthopteran assemblages (orthoptera) of the Hissar Valley (Tajikistan)

Results of investigation of the species composition and population density of the orthopteran assemblages, performed in the Hissar Valley in 1935 and 1989 are discussed. The increased anthropogenic press resulted in the drastic changes in the assemblages during 50 years. Two species dominating in the past, Calliptamus italicus (L.) and Dociostaurus maroccanus (Thunb.), are indicators of the integrity of original assemblages (and entire ecosystems of Hissar Valley, which are now completely destroyed) or of their insignificant transformation. The recent mesomorphic assemblages are dominated by Oxya fuscovittata (Marsch.), Duroniella gracilis Uv., Chorthippus biguttulus (L.), Aiolopus thalassinus (Fabr.), and xeromorphic communities, by Calliptamus barbarus (Costa), Dociostaurus tartarus (Stshelk.), Oedipoda miniata (Pall.), and Acrotylus insubricus (Scop.). The predominance and wide distribution of these species points to a significant transformation of ecosystems and destabilization of the environment in the Hissar Valley.     

Suppression of Settlement of Larvae of Fouling Organism by Water-Soluble Substances from Epibiotic Bacteria

Twenty-nine bacterial strains were isolated from the surface of the green alga Ulva reticulata, the soft coral Dendronephthya sp., and the sponge Haliclona sp. The bacterial species Vibrio alginolyticus, Vibrio sp. 4, an unidentified α-Proteobacterium, Vibrio sp. 7, Pseudoalteromonas sp. 2, and Pseudoalteromonas sp. 4 were found to suppress the larval settlement of the polychaete Hydroides elegans (Haswell, 1883) and the bryozoan Bugula neritina (Linnaeus, 1758). Aqueous extracts of five bacteria (all those named above except Pseudoalteromonas sp. 2) prevented larval settlement. Bacteria V. alginolyticus, Vibrio sp. 4, and an unidentified α-Proteobacterium were first discovered to produce high-molecular substances (>100 kDa) preventing larval settlement. Their activity was inhibited by amylase treatment, while trypsin and papain did not influence their activity. The data obtained proved that bacteria from the surface of the number of marine organisms excrete water-soluble sacchariferous compounds preventing larval settlement.     

Influential environmental gradients and patterns of fish assemblages in a West African basin

Twenty-two sites were monitored in the Lower Sassandra River Basin (Côte d’Ivoire, West Africa) to examine patterns in fish species assemblage structure along environmental gradients. Hierarchical clustering of the species presence–absence data identified four types of assemblages corresponding to the man-made Lake Buyo, the main channel, and the two major tributaries. Canonical Correspondence Analysis (CCA) indicated that canopy closure, leaves-wood, aquatic plants, temperature, width, total dissolved solids and depth were the environmental factors most strongly correlated with variation in the fish assemblages. Five species: Papyrocranus afer, Micralestes elongatus, Parailia pellucida, Tilapia busumana and T. mariae were reported from the basin for the first time. The investigation of the variation in species richness led to the assessment of a major anthropogenic disturbance induced by a palm oil factory. In conjunction with the fact that the Sassandra River hosts an endemic species, Synodontis koensis, it was concluded that this basin is of high conservation priority.     

Mayfly emergence along an oligotrophic Dinaric karst hydrosystem: spatial and temporal patterns,and species–environment relationship

Mayfly emergence was studied in the Plitvice Lakes National Park (Croatia) monthly over a 2-year period in four habitats (springs, streams, mountainous rivers, tufa barriers) using monthly collections of emergence traps. A total of 12 mayfly taxa were recorded. Almost half of the collected specimens belonged to the genus Baetis Leach, 1815, which was recorded at every site, but we were unable to distinguish between two included species (B. rhodani and B. cf. nubecularis). Other abundant species were Centroptilum luteolum (Müller, 1776), Alainites muticus (Linnaeus, 1758), Habrophlebia lauta Eaton 1884, Paraleptophlebia submarginata (Stephens, 1835), Serratella ignita (Poda, 1761), Ephemera danica Müller, 1764 and Rhithrogena braaschi Jacob, 1974. The mayfly assemblages at all sites were dominated by species typical of the rhithral zone, but there was a shift in species composition along a longitudinal gradient (from 720 to 390 m a.s.l.) from dominance of eucrenal–epirhithral to metarhithral–hyporhithral elements and finally to appearance of metapotamal and littoral elements. Two environmental factors, maximum water temperature and mean pH, had the highest influence on the mayfly assemblages. Emergence mainly occurred between March and November and was related to the elevated water temperature. Emergence patterns of some species were in accordance with their typical Central European emergence patterns (e.g. S. ignita, H. lauta) while some others showed certain discrepancies (e.g. longer emergence period in Rh. braaschi and P. submarginata, one generation emergence in A. muticus and variable emergence patterns between the sites and between the two studied years in C. luteolum). The current study provides a significant contribution to the knowledge of mayfly ecology in karst freshwater habitats which forms a basis for further investigation and monitoring of mayflies in this area.     

Evolution of the Solar Wind Speed with Heliocentric Distance and Solar Cycle. Surprises from Ulysses and Unexpectedness from Observations of the Solar Corona

An extensive analysis of Ulysses observations of the solar wind speed V from 1990 to 2008 is undertaken. It is shown that the evolution of V with heliocentric distance r depends substantially on both the heliolatitude and the solar activity cycle. Deviations from the predicted Parker’s profile of V(r) are so considerable that cannot be explained by a scarcity of measurements or other technical effects. In particular, the expected smooth growth of the solar wind speed with r is typical only for the solar activity maximum and for low heliolatitudes (lower than ±40°), while at high latitudes, there are two V(r) branches: growing and falling. In the solar activity maximum, V increases toward the solar pole in the North hemisphere only; however, in the South hemisphere, it decreases with heliolatitude. In the minimum of solar activity, the profile of V(r) at low heliolatitudes has a local minimum between 2 and 5 AU. This result is confirmed by the corresponding data from other spacecraft (Voyager 1 and Pioneer 10). Unexpected spatial variations in V at low heliolatitudes can be explained by the impact of coronal hole flows on the V(r) profile since the flows incline to the ecliptic plane. To reproduce the impact of spatial variations of V in the polar corona on the behavior of V at low heliolatitudes, a stationary one-fluid ideal MHD-model is developed with account of recent results on imagery of the solar wind speed in the corona up to 5.5 solar radii obtained on the basis of combined observations from SOHO/UVCS, LASCO, and Mauna Loa.     

Native ecosystem engineer facilitates recruitment of invasive crab and native invertebrates

Native ecosystem engineers that add physical structure to ecosystems can facilitate invasive species. In this study we determined the effects of the native tube-forming serpulid worm, Galeolaria caespitose on the recruitment of the invasive New Zealand porcelain crab, Petrolisthes elongatus, and whether invasive crab recruitment was related to the recruitment of native species. P. elongatus is abundant beneath intertidal rocks around Tasmania, southern Australia, and the underside of these rocks is usually covered with a calcareous matrix formed by the serpulid. We used an experimental approach to investigate whether rocks, serpulids on the underside of rocks and adult P. elongatus influenced the recruitment P. elongatus and native communities. P. elongatus and native invertebrates only recruited in the presence of rocks indicating the importance of rock as primary recruitment habitat. Moreover, the presence of serpulids on the underside of rocks significantly increased the recruitment of P. elongatus and native invertebrates compared to rocks without serpulids. Rocks with higher densities of adult P. elongatus at the end of the experiment also had higher densities of P. elongatus recruits. The density of P. elongatus recruits did not influence native species richness and abundance although there was some evidence that high P. elongatus recruitment was correlated with shifts in native community structure. We have shown that a native ecosystem engineer facilitates recruitment of an invasive crab but this does not appear to influence the recruitment of native species.     

Effects of nonnative invertebrates on two life stages of the native eastern oyster <Emphasis Type="Italic">Crassostrea virginica</Emphasis>

Since their recent introductions into Florida waters, three sessile invertebrates [Perna viridis (Asian green mussel), Mytella charruana (charru mussel) and Megabalanus coccopoma (pink titan acorn barnacle)] have expanded their range along the Atlantic coast in estuarine waters. Little research has been done to understand how these nonnative species interact with the ecologically and economically important eastern oyster Crassostrea virginica. To assess the potential effects of P. viridis, M. charruana and M. coccopoma on C. virginica, the following questions were addressed in manipulative experiments. (1) Does the presence of nonnative species decrease oyster larval settlement? (2) Do oyster larvae avoid settling on nonnative species? (3) Do nonnative species decrease survival of juvenile oysters (spat)? (4) Do nonnative species hinder spat growth? We included two controls: absence of nonnative species and presence of the native mussel Geukensia demissa. The nonnative species influenced settlement, growth and survival of C. virginica in different ways. M. coccopoma and P. viridis negatively influenced larval settlement, whereas M. charruana had no influence on the total number of settled larvae. Oyster larvae avoided settling on all three nonnative species and the native G. demissa. Both nonnative mussels negatively affected survival of juvenile oysters but only M. charruana also reduced spat growth. The native mussel, G. demissa, had no negative impacts on total settlement, survival and growth of C. virginica; in fact, it increased larval settlement in some trials. These three nonnative species should be classified as invasive because all had negative effects on native C. virginica.     

Bleaching response of coral species in the context of assemblage response

Caribbean coral reefs are declining due to a mosaic of local and global stresses, including climate change-induced thermal stress. Species and assemblage responses differ due to factors that are not easily identifiable or quantifiable. We calculated a novel species-specific metric of coral bleaching response, taxon-α and -β, which relates the response of a species to that of its assemblages for 16 species over 18 assemblages. By contextualizing species responses within the response of their assemblages, the effects of environmental factors are removed and intrinsic differences among taxa are revealed. Most corals experience either a saturation response, overly sensitive to weak stress (α > 0) but under-responsive compared to assemblage bleaching (β < 1), or a threshold response, insensitive to weak stress (α < 0) but over-responsive compared to assemblage bleaching (β > 1). This metric may help reveal key factors of bleaching susceptibility and identify species as targets for conservation.     

Bark-dwelling spider assemblages (Araneae) in the boreal forest: dominance,diversity, composition and life-histories

We collected spiders from tree-bark, foliage and litter habitats in deciduous and conifer dominated stands in NW Alberta (Canada) to define these assemblages and consider their conservation significance. To establish habitat associations, we used Indicator Species Analysis (ISA) together with a species dominance metric (DV′) newly proposed here. Of the 116 species collected, 78 were collected from bark. Results support categorizing 16 species as true bark-dwellers, 16 as facultative bark-dwellers and 46 as accidental bark-dwellers or species of unknown association. Species that were strong indicators of particular microhabitats in analyses restricted to bark habitats lost their indicator value when foliage and ground habitats were also considered, suggesting that bark habitats are critical for specific life-history functions. Clubiona canadensis Emerton 1980, Callobius nomeus (Chamberlin 1919), Pocadicnemis americana Millidge 1976 and Enoplognatha intrepida (Sørensen 1888) were the most common bark-dwelling species but their dominance varied among forest cover-types and trapping techniques. Collecting period, forest cover-type, habitat, and trapping technique were generally important environmental variables influencing composition of bark-dwelling assemblages. Although less important in structuring assemblages, tree status (dead or alive) and decay class were important for particular species. Bark habitats are crucial for boreal forest spider assemblages and must be considered central to maintenance of spider diversity.     

The Plant Alkaloid Camptothecin as a Novel Antifouling Compound for Marine Paints: Laboratory Bioassays and Field Trials

The extensive use of copper and booster biocides in antifouling (AF) paints has raised environmental concerns and the need to develop new AF agents. In the present study, 18 alkaloids derived from terrestrial plants were initially evaluated for AF activity using laboratory bioassays with the bryozoan Bugula neritina and the barnacle Balanus albicostatus. The results showed that 4 of the 18 alkaloids were effective in inhibiting larval settlement of B. neritina, with an EC₅₀ range of 6.18 to 43.11 μM, and 15 of the 18 alkaloids inhibited larval settlement of B. albicostatus, with EC₅₀ values ranging from 1.18 to 67.58 μM. Field trials that incorporated five alkaloids respectively into paints with 20% w/w indicated an in situ AF efficiency of evodiamine, strychnine, camptothecin (CPT), and cepharanthine, with the most potent compound being CPT, which also exhibited stronger AF efficiency than the commercial antifoulants cuprous oxide and zinc pyrithione in the field over a period of 12 months. Further field trials with different CPT concentrations (0.1 to 20% w/w) in the paints suggested a concentration-dependent AF performance in the natural environment, and the effective concentrations to significantly inhibit settlement of biofoulers in the field were ≥?0.5% w/w (the efficiency of 0.5% w/w lasted for 2 months). Moreover, CPT toxicity against the crustacean Artemia salina, the planktonic microalgae Phaeodactylum tricornutum and Isochrysis galbana, was examined. The results showed that 24 h LC₅₀ of CPT against A. salina was 20.75 μM, and 96 h EC₅₀ (growth inhibition) values of CPT to P. tricornutum and I. galbana were 55.81 and 6.29 μM, respectively, indicating that CPT was comparatively less toxic than several commercial antifoulants previously reported. Our results suggest the novel potential application of CPT as an antifoulant.     

The effect of emerald ash borer-caused tree mortality on the invasive shrub Amur honeysuckle and their combined effects on tree and shrub seedlings

Invasive insects and plants are major threats to the health and viability of North American forests. Emerald ash borer (Agrilus planipennis) (EAB) may cause extensive changes to forest composition due to rapid ash (Fraxinus spp.) mortality. Invasive shrubs like Amur honeysuckle (Lonicera maackii) may benefit from EAB and have negative effects on woody seedlings. We predict that ash mortality has positive effects on seedling abundance, recruitment, and survival, but that these effects are influenced by L. maackii basal area and/or cover. We sampled 16 sites, representing a chronosequence of ash mortality throughout western Ohio. We tested whether L. maackii growth and fecundity varied in relation to ash decline. We also investigated effects of ash decline, stand basal area (BA), L. maackii BA and percent cover on woody seedling abundance, recruitment, and survival using linear mixed models evaluated with Akaike’s Information Criterion. These same responses were also investigated for four seedling groups: L. maackii, invasive plants (excluding L. maackii), shade tolerant natives, and shade intolerant natives. We found a significant positive relationship between ash decline and L. maackii BA growth. Lower seedling species richness corresponded with greater L. maackii BA and better ash condition. Greater L. maackii BA was also associated with lower seedling abundance and recruitment, as well as abundance and recruitment of shade-tolerant species, and recruitment of shade-intolerant species. Sites with poorer ash condition and greater L. maackii BA had more L. maackii seedlings. These findings indicate that the negative effects of L. maackii are more important to future forest composition than ash decline; however ash decline increases L. maackii growth, hence exacerbating the effects of this invasive shrub.     

The structure of biogenic habitat and epibiotic assemblages associated with the global invasive kelp <Emphasis Type="Italic">Undaria pinnatifida</Emphasis> in comparison to native macroalgae

Kelp forests dominate temperate and polar rocky coastlines and represent critical marine habitats because they support elevated rates of primary and secondary production and high biodiversity. A major threat to the stability of these ecosystems is the proliferation of non-native species, such as the Japanese kelp Undaria pinnatifida (‘Wakame’), which has recently colonised natural habitats in the UK. We quantified the abundance and biomass of U. pinnatifida on a natural rocky reef habitat over 10 months to make comparisons with three native canopy-forming brown algae (Laminaria ochroleuca, Saccharina latissima, and Saccorhiza polyschides). We also examined the biogenic habitat structure provided by, and epibiotic assemblages associated with, U. pinnatifida in comparison to native macroalgae. Surveys conducted within the Plymouth Sound Special Area of Conservation indicated that U. pinnatifida is now a dominant and conspicuous member of kelp-dominated communities on natural substrata. Crucially, U. pinnatifida supported a structurally dissimilar and less diverse epibiotic assemblage than the native perennial kelp species. However, U. pinnatifida-associated assemblages were similar to those associated with Saccorhiza polyschides, which has a similar life history and growth strategy. Our results suggest that a shift towards U. pinnatifida dominated reefs could result in impoverished epibiotic assemblages and lower local biodiversity, although this could be offset, to some extent, by the climate-driven proliferation of L. ochroleuca at the poleward range edge, which provides complex biogenic habitat and harbours relatively high biodiversity. Clearly, greater understanding of the long-term dynamics and competitive interactions between these habitat-forming species is needed to accurately predict future biodiversity patterns.     

Life history differences and latitudinal variation in recruitment in two species of arctic-boreal perciform fishes,the fish doctor <Emphasis Type="Italic">Gymnelus viridis</Emphasis> and the Arctic shanny <Emphasis Type="Italic">Stichaeus punctatus</Emphasis>

Growth and recruitment were examined in two arctic-boreal, shallow water marine perciform species: the fish doctor Gymnelus viridis (Zoarcidae) and the Arctic shanny Stichaeus punctatus (Stichaeidae). G. viridis ranges in the Canadian Arctic from northern Hudson Bay to northern Ellesmere Island, whereas S. punctatus has a more southerly range from Nova Scotia coastal waters to northern Hudson Bay. At Nuvuk Islands in northeastern Hudson Bay, where the two species are sympatric in shallow water, they had comparable juvenile growth rates but temporal variation in 0+ recruitment was substantially greater in S. punctatus. This difference may stem from their contrasting early life histories. S. punctatus spawns large numbers of small demersal eggs that hatch into pelagic larvae, whereas G. viridis spawns small numbers of large demersal eggs that hatch directly into demersal juveniles with no pelagic stage, suggesting that recruitment in G. viridis should be less sensitive to yearly variation in the onset of the ice-free period in Hudson Bay and the subsequent pulse of pelagic invertebrate production. Relative to Nuvuk, recruitment variation in G. viridis was found to be greater at Resolute, Cornwallis Island, close to its northern range limit, whereas recruitment variation in S. punctatus was not evident in Newfoundland, closer to its southern range limit.     

Resolving neutral and deterministic contributions to genomic structure in <Emphasis Type="Italic">Syntrichia ruralis</Emphasis> (Bryophyta,Pottiaceae) informs propagule sourcing for dryland restoration

Syntrichia ruralis is a cosmopolitan moss that occupies steep environmental gradients. In arid to semi-arid regions of the world it is a key component of biological soil crusts, which are fundamental to healthy dryland ecosystem processes. As such, S. ruralis has attracted the attention of conservationists seeking to restore degraded biological soil crust communities and their associated vascular flora. Here, we generate genomic data for S. ruralis populations that span climatic gradients across the Colorado Plateau of the southwestern USA to investigate the contributions of neutral and deterministic processes to the partitioning of genomic structure. Although S. ruralis appears to be highly dispersible, geographic proximity significantly predicts genomic similarity. In addition, even when taking into account apparently high migration rates among populations and spatial autocorrelation of allele frequencies, some genomic variation is explained by environmental gradients correlated with elevation and latitude. Consequently, efforts to restore dryland ecosystems by establishing S. ruralis as a foundation should include strategies to ensure that propagule sources of this moss are environmentally stratified and targeted to the current/future climates of restoration sites.