Predictors Of Species Composition Research Articles

Urban park attributes as predictors for the diversity and composition of spontaneous plants − A case in Beijing, China

Urban biodiversity homogenization and native species habitat loss are becoming increasingly severe. The overuse of lawn grasses and cultivars in green spaces is one of the most important drivers. Scholars have asserted that spontaneous vegetation provides various ecological benefits and should be widely incorporated in planting design. Factors influencing spontaneous plant diversity have mainly been studied in specific habitats or at the city scale, and findings surrounding the attributes of urban parks that support the diversity of spontaneous plants are lacking. This study aimed to provide a perspective on conserving spontaneous plants through inferring the urban park attributes associated with plant diversity. Twenty-two urban park samples in Beijing were examined to identify the correlation between various park variables and spontaneous vegetation. This study recorded 199 spontaneous plant species, with large historic parks containing the most number of species. Park size was a remarkable predictive variable for the diversity of spontaneous plants. Species richness and diversity in large parks were significantly higher than in small parks; not only in total richness due to the species–area relationship but also in richness and diversity at the community level independent of plot number. Microhabitat heterogeneity and the percentage of green area had the strongest positive association with the richness of spontaneous plants. In contrast, the maintenance intensity, perimeter–area ratio, and fragmentation of green area, deciduous forest, and open lawn patches had negative associations with spontaneous plant richness. Redundancy analysis demonstrated that park area, maintenance intensity, microhabitat heterogeneity, and deciduous forest patches were the most remarkable variables predicting species composition. The correlations of variables related to water and open lawn patches with spontaneous plant diversity were more evident in summer. The predicted variables were also more significantly correlated with the diversity of exotic species in summer than in spring. Perennial herbs were more sensitive to the evaluated park attributes. This study elucidates how spontaneous plants are associated with the attributes of urban parks in Beijing, with critical implications for other large cities.

Deriving forest stand information from small sample plots: An evaluation of statistical methods

Most strategic and operational forest management decisions are taken based on stand-level information, and quantitative models of forest dynamics are key for developing sustainable management strategies. However, data on forest stands for the initialisation of such models that are representative at large spatial scales, e.g., countries or ecoregions, are often lacking. National Forest Inventories (NFIs) provide forest data from small sample plots at large spatial scales, yet deriving full stand information based on such data is challenging. Here, we evaluate seven methods of varying complexity for deriving quantitative stand descriptions based on sample data as provided by the Swiss NFI. We selected 271 extensively measured Swiss forests stands with unimodal diameter distributions, classified them as beech- vs. spruce-dominated in five development stages and randomly placed a small sized sample plot in each stand using the Swiss NFI sampling design (i.e., a circular plot of 500 m2). Seven modelling approaches were used to derive diameter distributions and species-specific stem numbers (i.e., tree species composition) from the sample data that are representative for a particular stand (local scale) and for stand types in general (generalised scale). The prediction performance of the modelling approaches was evaluated using 100 random samples per stand to calculate prediction errors. Generalised even-aged diameter distributions were best predicted by the simultaneous parameter prediction method (PPM), i.e. a combined three-step regression approach, with on average 1.3 to 2.5 times lower prediction errors compared to the simple pooling of diameter samples. However, uneven-aged diameter distributions were best predicted by pooling. At the local scale, the simultaneous PPM performed best for data from sample plots with fewer than 17 to 19 trees across all development stages. Prediction performance of the PPMs increased for structurally and spatially diverse local stands with positively skewed diameter distributions. A Random Forest approach was most suitable for predicting species composition at both the generalised and the local scale. Our study evaluates the strengths and weaknesses of methods to model stands based on data from small sample plots. We emphasise terminological pitfalls by consequently distinguishing local accuracy and generalised representativity of the stand descriptions. We demonstrate the feasibility of deriving locally accurate stands using data from small forest sample plots and evaluate the derivation of generalised stands representative at large regions. At both scales, our developments contribute to an improved initialisation of forest models and thus to a more realistic modelling of forest development under future boundary conditions.

Effects of Environmental Changes on Gerromorpha (Heteroptera: Hemiptera) Communities from Amazonian Streams

The presence of environmental conditions that are suitable for the development of agricultural and cattle-raising activities has favored the expansion of land use in the Brazilian Amazon. This expansion changes the environmental conditions of aquatic ecosystems by altering the structure of the streambeds and the physicochemical conditions of the water. Therefore, this manuscript aimed to assess the effect of changes in environmental conditions along a gradient of different land uses on the richness and species composition of Gerromorpha (Heteroptera: Hemiptera) communities in streams from the Brazilian Amazon. We sampled Gerromorpha communities and environmental variables (physical structure of the habitat and physicochemical characteristics of the water) in 45 streams in the municipality of Paragominas in the state of Pará, Brazil. We then performed variation partitioning analyses to assess the relative contribution of habitat structure and water physicochemical variables on the richness and species composition. The Habitat Integrity Index (HII), which measures the habitat physical structure, was the best predictor of species richness. The HII and physicochemical variables were jointly the best predictors of species composition. Our results show that Gerromorpha communities respond to gradients of environmental anthropization in the Amazon region, which reinforces the importance of habitat integrity and water quality for the maintenance of Gerromorpha communities.

Variation in floristic and trait composition along environmental gradients in the herb layer of temperate forests in the transition zone between Central and SE Europe

Species- and trait-environment linkages in forest plant communities continue to be a frequent topic in ecological research. We studied the dependence of floristic and functional trait composition on environmental factors, namely local soil properties, overstory characteristics, climatic parameters and other abiotic and biotic variables. The study area comprised 50 monitoring plots across Slovenia, belonging to the EU ICP Forests monitoring network. Vegetation was surveyed in accordance with harmonized protocols, and environmental variables were either measured or estimated during vegetation sampling. Significant predictors of species composition were identified by canonical correspondence analysis. Correlations between plant traits, i.e. plant growth habit, life form, flowering features and CSR signature, were examined with fourth-corner analysis and linear regressions. Our results show that variation in floristic composition was mainly explained by climatic parameters (mean annual temperature, mean annual precipitation), soil properties (pH) and tree layer-dependent light conditions. Trait composition was most closely related with tree layer characteristics, such as shade-casting ability (SCA, a proxy for light availability in the understory layer), tree species richness and tree species composition. Amongst soil properties, total nitrogen content and soil texture (proportion of clay) were most frequently correlated with different species traits or trait states. The CSR signature of herb communities was associated with tree layer SCA, soil pH and mean annual temperature. The floristic composition of the studied herb-layer vegetation depended on temperature and precipitation, which are likely to be influenced by ongoing climate change (warming and drying). Trait composition exhibited significant links to tree layer characteristics and soil conditions, which are in turn directly modified by forest management interventions.

Prediction of species composition ratios in pooled specimens of the Anopheles Hyrcanus group using quantitative sequencing

BackgroundPlasmodium vivax is transmitted by members of the Anopheles Hyrcanus Group that includes six species in the Republic of Korea: Anopheles sinensis sensu stricto (s.s.), Anopheles pullus, Anopheles kleini, Anopheles belenrae, Anopheles lesteri, and Anopheles sineroides. Individual Anopheles species within the Hyrcanus Group demonstrate differences in their geographical distributions, vector competence and insecticide resistance, making it crucial for accurate species identification. Conventional species identification conducted using individual genotyping (or barcoding) based on species-specific molecular markers requires extensive time commitment and financial resources.ResultsA population-based quantitative sequencing (QS) protocol developed in this study provided a rapid estimate of species composition ratios among pooled mosquitoes as a cost-effective alternative to individual genotyping. This can be accomplished by using species- or group-specific nucleotide sequences of the mitochondrial cytochrome C oxidase subunit I (COI) and the ribosomal RNA internal transcribed spacer 2 (ITS2) region as species identification alleles in a two-step prediction protocol. Standard genomic DNA fragments of COI and ITS2 genes were amplified from each Anopheles species using group-specific universal primer sets. Following sequencing of the COI or ITS2 amplicons generated from sets of standard DNA mixtures, equations were generated via linear regression to predict species-specific nucleotide sequence frequencies at different positions. Species composition ratios between An. sineroides, An. pullus and An. lesteri were estimated from QS of the COI amplicons based on the mC.260A, mC.122C and mC.525C alleles at the first step, followed by the prediction of species composition ratios between An. sinensis, An. kleini and An. belenrae based on QS of the ITS2 amplicons using the rI.370G and rI.389T alleles. The COI copy number was not significantly different between species, suggesting the reliability of COI-based prediction. In contrast, ITS2 showed a slightly but significantly higher copy number in An. belenrae, requiring an adjustment of its predicted composition ratio. A blind test proved that predicted species composition ratios either from pooled DNA specimens or pooled mosquito specimens were not statistically different from the actual values, demonstrating that the QS-based prediction is accurate and reliable.ConclusionsThis two-step prediction protocol will facilitate rapid estimation of the species composition ratios in field-collected Anopheles Hyrcanus Group populations and is particularly useful for studying the vector ecology of Anopheles population and epidemiology of malaria.

Time-Varying Epipelagic Community Seascapes: Assessing and Predicting Species Composition in the Northeastern Pacific Ocean

The vast spatial extent of the ocean presents a major challenge for monitoring changes in marine biodiversity and connecting those changes to management practices. Remote-sensing offers promise for overcoming this problem in a cost-effective, tractable way, but requires interdisciplinary expertise to identify robust approaches. In this study, we use generalized additive mixed models to evaluate the relationship between an epipelagic fish community in the Northeastern Pacific Ocean and oceanographic predictor variables, quantified in situ as well as via remote-sensing. We demonstrate the utility of using MODIS Rrs555 fields at monthly and interannual timescales to better understand how freshwater input into the Northern California Current region affects higher trophic level biology. These relationships also allow us to identify a gradient in community composition characteristic of warmer, offshore areas and cooler, nearshore areas over the period 2003–2012, and predict community characteristics outside of sampled species data from 2013 to 2015. These spatial maps therefore represent a new, temporally and spatially explicit index of community differences, potentially useful for filling gaps in regional ecosystem status reports and is germane to the broader ecosystem-based fisheries management context.

Carbon Dioxide and Methane Flux Response and Recovery From Drought in a Hemiboreal Ombrotrophic Fen

Globally peatlands store 500 Gt carbon (C), with northern blanket bogs accumulating 23 g C m−2 y−1 due to cool wet conditions. As a sink of carbon dioxide (CO2) peat bogs slow anthropogenic climate change, but warming climate increases the likelihood of drought which may reduce net ecosystem exchange (NEE) and increase soil respiration, tipping C sinks to sources. High water tables make bogs a globally important source of methane (CH4), another greenhouse gas (GHG) with a global warming potential (GWP) 34 times that of CO2. Warming may increase CH4 emissions, but drying may cause a reduction. Predicted species composition changes may also influence GHG balance, due to different traits such as erenchyma, e.g., Eriophorum vaginatum (eriophorum) and non-aerenchymatous species, e.g., Calluna vulgaris (heather). To understand how these ecosystems will respond to climate change, it is vital to measure GHG responses to drought at the species level. An automated chamber system, SkyLine2D, measured NEE and CH4 fluxes near-continuously from an ombrotrophic fen from August 2017 to September 2019. Four ecotypes were identified: sphagnum (Sphagnum spp), eriophorum, heather and water, hypothesizing that fluxes would significantly differ between ecotypes. The 2018 drought allowed comparison of fluxes between drought and non-drought years (May to September), and their recovery the following year. Methane emissions differed between ecotypes (p < 0.02), ordered high to low: eriophorum > sphagnum > water > heather, ranging from 23 to 8 mg CH4-C m−2 d−1. Daily NEE was similar between ecotypes (p > 0.7), but under 2018 drought conditions all ecotypes were greater sources of CO2 compared to 2019, losing 1.14 g and 0.24 g CO2-C m−2 d−1 respectively (p < 0.001). CH4 emissions were ca. 40% higher during 2018 than 2019, 17 mg compared to 12 mg CH4-C m−2 d−1 (p < 0.0001), and fluxes exhibited hysteresis with water table depth. A lag of 84–88 days was observed between rising water table and increased CH4 emissions. A significant interaction between ecotype and year showed fluxes from open water did not return to pre-drought levels. Our findings suggest that short-term drought may lead to a net increase in C emissions from northern wetlands.

High diversity of native plants and vegetation types in the Morialta Conservation Park and the threat of invasive species

ABSTRACT Morialta Conservation Park is a scenic protected area that contains important vegetation remnants of the Mount Lofty Ranges. Here we investigate the vegetation ecology, soils and plant diversity of the park. Using a stratified, quantitative survey of woody vegetation and topsoils throughout the park within forty-five 10 × 10 m plots, we identified ten distinct vegetation types, nine being native and the other being dominated by the invasive European olive (Olea europaea). Soil conductivity and fertility, as well as aspect, were significant predictors of species composition, indicating that high environmental heterogeneity in soils and topography are important in facilitating the high biodiversity in the Morialta Conservation Park. The European olive and Boneseed (Chrysanthemoides monilifera ssp. monilifera) are widespread in the park and a threat to native vegetation. Using published plant lists and the Atlas of Living Australia, we report 486 native (and 300 introduced) plant taxa from the park and its immediate surrounds, including species considered endangered at either the state or national level, or the IUCN Red List. Therefore, the park is highly important for conservation and the threat posed by the European olive, Boneseed and other invasive species should be effectively managed.

Dimensions of Phyllostomid Bat Diversity and Assemblage Composition in a Tropical Forest-Agricultural Landscape

Tropical rainforests are suffering rapid habitat loss with large extensions of land transformed into agriculture. We wanted to know whether the type of agricultural activity in forest-agricultural landscapes affects how species composition as well as taxonomic and functional dimensions of diversity respond. We worked in the Amazon forests of southeast Peru and used bats as model organisms. We sampled mosaics characterized by forest adjacent to papaya plantations or cattle pastures. At each sampling site we established a transect in each of the three different vegetation types: forest interior, forest edge and agricultural land. We found that vegetation type was a better predictor of species composition than the type of agricultural land present. Vegetation structure characteristics explained differences in bat species composition between forest interior and edge. Agricultural land type chosen was not irrelevant as we found higher estimated species richness in papaya than in pasture sites. Agricultural land type present in a site and vegetation type affected functional diversity, with both agricultural land types showing a lower number of functionally distinct species than forests. We found papaya plantation sites showed species more evenly dispersed in trait space, suggesting they do better at conserving functional diversity when compared to cattle pasture sites. We demonstrate that sites that harbor agricultural activities can maintain a considerable proportion of the expected bat diversity. We note that this region still has large tracts of intact forest adjacent to agricultural lands, which may explain their ability to maintain relatively high levels bat diversity.

Long-term responses of desert ant assemblages to climate.

Productivity is a key driver of ecosystem structure and function, so long-term studies are critical to understanding ecosystems with high temporal variation in productivity. In some deserts, productivity, driven by moisture availability, varies immensely over time (rainfall) and space (landscape factors). At high productivity, species richness is expected to be driven in opposing directions by abundance (More Individuals Hypothesis - MIH) and competition. While studies investigating the impacts of spatial variation in productivity on community structure are common, the impacts of temporal variability on productivity are poorly understood. We tested how well rainfall predicted the activity, species numbers and assemblage composition of ants and if responses were moderated by landscape position. We also asked whether the number of species (richness per sampling unit and estimated species richness) responded directly to rainfall or was moderated by ant activity or competition from dominant ants. Over a 22-year period, when annual rainfall fluctuated between 79mm and 570mm, we sampled ants using pitfall traps in paired dune and swale habitats in the Simpson Desert, Australia. We used climate records over this period to model changes in ant assemblages. Activity of dominant ants responded primarily to long-term rainfall, increasing exponentially, while subordinate ants responded to short-term weather and time. Consistent with the MIH, the number of ant species was best predicted by activity, particularly that of subordinate ants. Activity of dominant ants had a declining positive effect on numbers of species. Landscape position strongly predicted species composition, while long-term rainfall determined composition at genus level but not species level. Over time, species composition fluctuated, but several genera consistently increased in activity. Productivity moderators such as long-term rainfall and landscape position are key drivers of ant activity and composition in the study ecosystem, acting indirectly on numbers of species. Numbers of species were explained largely by ant activity, making a strong case for the MIH, but not competition. Longer periods of low rainfall may indirectly reduce species richness in desert ecosystems. However, a trend to increasing richness over time may indicate that conservation management can ameliorate this impact.

Predicting the response of nekton assemblages to seagrass transplantations in the Venice lagoon: An approach to assess ecological restoration

Abstract One of the major challenges to ensure effective restoration of estuarine habitats is to establish success criteria to determine whether the goals of restoration are met. The aim of this work is to propose and test an approach to identify reference conditions and assess the recovery of nekton (fish, decapods and cephalopods) assemblages at seagrass restoration sites. Nekton sampling took place from 2014 to 2017 in the northern Venice lagoon (northern Adriatic Sea, Italy) during spring at eight sites subjected to seagrass (Zostera marina and Zostera noltei) transplantation. In spring 2016, five natural seagrass sites in the same area were additionally sampled, and physico‐chemical water parameters and habitat structure were also recorded. A multivariate generalized linear model approach was adopted in order to disentangle the relative effect of water quality and seagrass habitat structure on nekton assemblages of natural habitats. Models were subsequently employed to predict species composition of nekton fauna at each transplantation site, to identify the reference assemblage expected under site‐specific abiotic and habitat characteristics. The average distance of the observed assemblage from reference conditions was used to track temporal trajectories of nekton colonization at transplantation sites, and to ultimately evaluate the recovery rate towards restoration goals. This study highlights how a predictive approach could serve management purposes in ecological restoration, providing a concise tool to assess the functionality of restored habitats for associated fauna.

The history of mycological studies in Khanty-Mansi autonomous okrug: 1) the period of isolated studies, lignicolous basidiomycetes and phytopathological studies

Регулярные микологические исследования на территории Ханты-Мансийского автономного округа-Югры начались во второй половине 20-го века. В настоящее время известно около 100 публикаций, посвященных вопросам изучения микобиоты, экологии, таксономии, лесо- и фитопатологии и охране грибов на территории региона. В публикации проведен обзор всех работ, опубликованных на территории ХМАО по микологической тематике и их систематизация по разным направлениям. Первая часть статьи состоит из введения, упоминания первых разрозненных работ и обзора изучения дереворазрушающих базидиомицетов и фитопатологических исследований. Во второй части будут рассмотрены другие направления, проанализировано состояние коллекций грибов, собранных на территории региона, и обобщены результаты выявления видового разнообразия.
 Одной из наиболее подробно изученных экологических групп на территории ХМАО являются ксилотрофные базидиомицеты: их видовой состав, географическое распространение, экологические ниши, уязвимость под воздействием нефтегазодобычи и природоохранная значимость. Развиваются также лесо- и фитопатологические направления, проведены исследования патогенов лесообразующих пород, а также фитосанитарные обследования городских насаждений города Сургута и других территорий.

CFD simulation of reactor furnace of sulfur recovery units by considering kinetics of acid gas (H2S and CO2) destruction

In the present study, a 3D model of the industrial thermal reactor furnace of sulfur recovery units (SRUs) was simulated using the commercial CFD code ANSYS-FLUENT. The RNG-k-ε turbulence model and the eddy-dissipation-concept for taking into account the interactions of chemical reactions and turbulent flow were used in the computational model. The radiative transport was analyzed using the discrete ordinates method. Detailed reaction mechanisms were introduced in the CFD model for providing accurate predictions of combustion and the resulting species concentrations. The furnace geometry that was identical to those used in the industry was simulated. The predicted species composition distribution, temperature distribution, and absolute pressure, were in close good agreement with the corresponding measured data. Relative errors between the CFD results and the industrial data in terms of H2S conversion and overall efficiency were, respectively, 0.081% and 0.56%. New aspects of influence of geometric parameters such as burner, choke ring, and checker wall on the hydrodynamics and thermal behavior of the reactor furnace were also discussed.

Commonness, rarity, and oligarchies of woody plants in the tropical dry forests of Mexico

AbstractWe assessed woody plant communities in two widely separated forests in the tropical dry forest (TDF) biome of Mexico for evidence of similar patterns of species commonness and rarity. We used belt transects laid out along contour lines (i.e., constant elevation) and stratified across elevation gradients at sites in Jalisco and Oaxaca to sample woody plant species diversity, abundance, relative frequency and basal area. We assembled a combined species list and compared species found in both sites (shared) to species found in only one site, assessing whether the most and least common species at a site tended to be shared or unshared. Of the 8242 individuals sampled, 370 species or morpho‐species were identified, with 222 species recorded at the Jalisco site and 270 at the Oaxaca site—122 (33%) species were shared across sites. Abundance, frequency and basal area of shared species were greater on average than for unshared species, and were positively correlated across sites. A subset of 68 shared species (18%) accounted for over half of all individuals encountered at the two sites. Species in the most common quartile were more likely to be shared than expected by chance, while species in the least common quartile were less likely. A genus‐level analysis found similar patterns. Our findings suggest that the TDF of Pacific coast Mexico shows evidence of widespread dominance by a small subset of species. These findings have potentially important implications for predicting species composition, understanding the role of oligarchic species in ecological processes, and conserving rare species.

Clinical Observations on the Treatment of Solitary Rectal Ulcer Syndrome (SRUS) with Stapled Transanal Rectal Resection (STARR) Surgery

In the present study, a 3D model of the industrial thermal reactor furnace of sulfur recovery units (SRUs) was simulated using the commercial CFD code ANSYS-FLUENT. The RNG-k-ε turbulence model and the eddy-dissipation-concept for taking into account the interactions of chemical reactions and turbulent flow were used in the computational model. The radiative transport was analyzed using the discrete ordinates method. Detailed reaction mechanisms were introduced in the CFD model for providing accurate predictions of combustion and the resulting species concentrations. The furnace geometry that was identical to those used in the industry was simulated. The predicted species composition distribution, temperature distribution, and absolute pressure, were in close good agreement with the corresponding measured data. Relative errors between the CFD results and the industrial data in terms of H2S conversion and overall efficiency were, respectively, 0.081% and 0.56%. New aspects of influence of geometric parameters such as burner, choke ring, and checker wall on the hydrodynamics and thermal behavior of the reactor furnace were also discussed.

Effects of neutrality, geometric constraints, climate, and habitat quality on species richness and composition of Atlantic Forest small-mammals

Aim To compare the fit of models of climate, habitat quality, neutral processes, and geometric constraints to species richness and composition of small mammal assemblages. Location The South American Atlantic Forest biome. Methods Using neutral models and mid-domain effect models, we simulated species spread in a spatially explicit array of grid cells representing the Atlantic Forest domain. We compared empirical patterns of species richness and composition with predictions of the neutral and mid-domain effect models. We also modeled individual species responses to climatic conditions and forest integrity, a measure of habitat quality. Results Habitat quality was the single best predictor of local species richness (α-diversity), but was a poor predictor of local species composition and of the decay in species similarity with distance (β-diversity). The neutral and mid-domain models generated very similar predictions, and were better predictors of species composition than of species richness. Climate variables were also strongly associated with overall species composition, but not with species richness. Main Conclusions The species richness of small-mammal assemblages in the Atlantic Forest is best explained by variation in habitat quality. In contrast, the composition of small-mammal assemblages is best explained by models of limited dispersal (neutral and mid-domain) and effects of climate on local species composition. Collectively, these results suggest that regional patterns of species richness may be uncoupled from patterns of species composition. Both species richness and composition should be considered when evaluating the predictions of neutral and mid-domain effect models, and of correlations of community structure with climatic or habitat variables.

Predicting local extinctions of Amazonian vertebrates in forest islands created by a mega dam

Hydropower projects are rapidly expanding across lowland Amazonia, driving the conversion of large tracts of once-continuous forests into archipelagos embedded within a vast open-water matrix. Forest vertebrate populations thus become stranded in habitat islands, with their persistence governed by a combination of species life-history traits, habitat patch, and landscape context. We investigate the patterns of species extinction of 34 arboreal and terrestrial vertebrate species within three continuous forest sites and 37 land-bridge islands within one of the largest South American hydroelectric reservoirs, based on a combination of camera trapping, line-transect censuses, sign surveys, and armadillo burrow counts. Forest area was the best predictor of species persistence, so we classified all species into three levels of vulnerability to habitat insularization, with most species defined as ‘area-sensitive’. However, island occupancy was decisively determined by individual species traits, with wide-ranging species and poor dispersers showing high local extinction rates. We detected higher island occupancy rates of large vertebrate species compared to other Neotropical fragmented forest landscapes, suggesting that this is critically attributed to the absence of hunting pressure at Balbina. Nevertheless, most terrestrial and arboreal species have been driven to local extinction within the vast majority of islands, which have been largely defaunated. We predicted species composition across all 3546 islands within the reservoir, indicating that only ⩽2% of all islands continue to harbour at least 75% of all species. To minimise loss of vertebrate diversity, future hydroelectric dam projects in lowland tropical forests, if unavoidable, should consider their geographic location and landscape structure to maximise both island size and landscape connectivity, and set aside strictly protected reserves within reservoir areas.

Evaluation of a fishing captain's ability to predict species composition, sizes, and quantities of tunas associated with drifting fish-aggregating devices in the eastern Pacific Ocean

Abstract Experiments were conducted to evaluate a fishing captain's ability to predict species composition, sizes, and quantities of tunas associated with drifting fish-aggregating devices (FADs), before encirclement with a purse-seine net. Operating in the equatorial eastern Pacific Ocean, during 11 May–23 July 2011, Captain Ricardo Diaz detected small quantities of bigeye (Thunnus obesus) and yellowfin (Thunnus albacares) tunas within large FAD-associated aggregations dominated by skipjack tuna (Katsuwonus pelamis). The captain's predictions were significantly related to the actual total catch and catch by species, but not to size categories by species. His predictions of species composition were most accurate when estimates of bigeye and yellowfin tuna were combined. If purse-seine captains are able to make accurate predictions of the proportion of bigeye and yellowfin tunas present in mixed-species aggregations associated with FADs, managers may wish to consider incentives to fishers to reduce the fishing mortality on those species.

Environmental determinants of leech assemblage patterns in lotic and lenitic habitats

Leeches (Clitellata: Hirudinida) are abundant predators or ecto-parasites inhabiting various freshwater habitats; however many biotic and abiotic drivers of their assemblage patterns have been deduced rather than directly tested. To study species richness and composition changes in leech assemblages, 109 sites of running and stagnant water bodies were sampled in three regions of the Czech Republic in 2007–2010, together with several explanatory variables that are known or expected to be important predictors of leech distribution. In total, 17 species of leeches were recorded, varying between 0–7 and 0–9 species in lotic and lenitic sites, respectively. These differences in species richness of lotic and lenitic sites were highly significant, contrary to the abundances, which varied between 0–283 and 0–295 individuals. The main change in species composition was controlled by water temperature and morphological characteristics (e.g. substrate and cover of macrophytes), mostly reflecting the differences between lotic and lenitic habitats. We found the density of benthos (i.e. prey availability) to be the best predictor of species composition in both lotic and lenitic sites, together with the percentage of canopy cover. However, the other significant predictors (i.e. the substrate and water conductivity found to be significant in lotic sites, and the mean annual temperature and PO 4 3− in lenitic sites), differed between these habitats. Other than mean annual temperature and water temperature, which had different effects on species richness in lotic and lenitic sites, there were no other differences between lotic and lenitic sites in terms of how species richness and abundance responded to all other analyzed predictors. Our results stress the importance of prey availability and canopy for leech distribution patterns. Differences in the significant predictors of leech assemblage patterns between lotic and lenitic sites raise fundamental questions about the underlying mechanisms and ecological constraints to leech distribution in these main types of aquatic systems.

An empirical model of seasonal depth-dependent fish assemblage structure to predict the species composition of mixed catches

Reliable catch statistics are essential for assessing fishing impacts on individual stocks. However, fisheries that capture a mixture of stocks or species for which catch statistics are not disaggregated pose a challenge. Nonetheless, catch composition can be inferred given information on fishing date and location and a prevalent role of season and habitat in structuring fish assemblage composition. Here, a harmonic regression model for multinomial data, intended to predict the species composition of catches based on season and depth, is developed using bottom-trawl survey data. Model development was motivated by the need to quantify catches of individual skate (Rajidae) species in fisheries for which landing and discard data are only reliable at the family level. The model was validated by applying it to flatfishes (Pleuronectidae), whose catches are generally reliably and consistently disaggregated by species. The predicted species composition of flatfish matched the composition observed in fishery catches well. The present approach should be applicable to other well-surveyed ecosystems where assemblage composition is structured by one or more key environmental variables of known spatial distribution.