Variation In Species Composition Research Articles

River flow intermittence influence biodiversity-stability relationships across spatial scales: Implications for an uncertain future.

Climate change is increasing the proportion of river networks experiencing flow intermittence, which in turn reduces local diversity (i.e., α-diversity) but enhances variation in species composition among sites (i.e., β-diversity), with potential consequences on ecosystem stability. Indeed, the multiscale theory of stability proposes that regional stability can be attained not only by local processes but also by spatial asynchrony among sites. However, it is still unknown whether and how scale-dependent changes in biodiversity associated with river flow intermittence influence stability across spatial scales. To elucidate this, we here focus on multiple metacommunities of French rivers experiencing contrasting levels of flow intermittence. We clearly show that the relative contribution of spatial asynchrony to regional stability was higher for metacommunities of intermittent than perennial rivers. Surprisingly, spatial asynchrony was mainly linked to asynchronous population dynamics among sites, but not to β-diversity. This finding was robust for both truly aquatic macroinvertebrates and for taxa that disperse aerially during their adult stages, implying the need to conserve multiple sites across the landscape to attain regional stability in intermittent rivers. By contrast, metacommunities of truly aquatic macroinvertebrates inhabiting perennial rivers were mainly stabilized by local processes. Our study provides novel evidence that metacommunities of perennial and intermittent rivers are stabilized by contrasting processes operating at different spatial scales. We demonstrate that flow intermittence enhances spatial asynchrony among sites, thus resulting in a regional stabilizing effect on intermittent river networks. Considering that climate change is increasing the proportion of intermittent rivers worldwide, our results suggest that managers need to focus on the spatial dynamics of metacommunities more than on local-scale processes to monitor, restore, and conserve freshwater biodiversity.

How important is Forest Age in explaining the species composition of Near-natural Spruce Forests?

Multiple ecological drivers, along with forest age, determine the species composition of boreal forest ecosystems. However, the role of age in successional changes in forests cannot be understood without taking site conditions, the disturbance regime and forest structure into account. In this study, we ask two research questions: 1. What is the relationship between forest age and overall species composition in older near-natural spruce forests, i.e. forests of age beyond harvest maturity? 2. Do species associated with different forest habitats respond similarly to variation in forest age? Data were collected in 257 Norway spruce dominated 0.25 ha plots from three study areas in Southeastern and Central Norway. Species inventories were conducted for lichens and bryophytes on trees and rocks, vascular plants on the forest floor, and for deadwood-associated bryophytes and polypore fungi. Although NMDS ordination analyses of the total species composition identified a main axis related to the age of the oldest trees in two of the study areas, variation partitioning analyses showed that age explained a small fraction of variation of the species composition compared to site conditions, logging history, forest structure, and differences between the sites in all habitats. The unique variation explained by forest age species was, however, significant for all habitats. The fraction of variation in species composition explained by forest age was the largest for lichens and bryophytes on trees, and for deadwood-associated bryophytes and polypore fungi. Our results suggest that practical mapping of near-natural forests for management purposes inventories should include site conditions, forest structure and between site differences in addition to forest age.

Long‐term changes in taxonomic and functional composition of European marine fish communities

Evidence of large‐scale biodiversity degradation in marine ecosystems has been reported worldwide, yet most research has focused on few species of interest or on limited spatiotemporal scales. Here we assessed the spatial and temporal changes in the taxonomic and functional composition of fish communities in European seas over the last 25 years (1994–2019). We then explored how these community changes were linked to environmental gradients and fishing pressure. We show that the spatial variation in fish species composition is more than two times higher than the temporal variation, with a marked spatial continuum in taxonomic composition and a more homogenous pattern in functional composition. The regions warming the fastest are experiencing an increasing dominance and total abundance of r‐strategy fish species (lower age of maturity). Conversely, regions warming more slowly show an increasing dominance and total abundance of K‐strategy species (high trophic level and late reproduction). Among the considered environmental variables, sea surface temperature, surface salinity and chlorophyll‐a most consistently influenced communities' spatial patterns, while bottom temperature and oxygen had the most consistent influence on temporal patterns. Changes in communities' functional composition were more closely related to environmental conditions than taxonomic changes. Our study demonstrates the importance of integrating community‐level species traits across multi‐decadal scales and across a large region to better capture and understand ecosystem‐wide responses and provides a different lens on community dynamics that could be used to support sustainable fisheries management.

METAZOAN PARASITE COMMUNITY OF THE YELLOW SNAPPER LUTJANUS ARGENTIVENTRIS: FACTORS THAT INFLUENCING SPECIES COMPOSITION AND RICHNESS.

A total of 366 individuals of Lutjanus argentiventris (Peters, 1869) were collected over a 5-yr period (October 2018 to June 2022) from Acapulco Bay, Mexico. Parasite communities in Lutjanus argentiventris were quantified and analyzed to determine the main factors that generate changes in species richness and/or species composition over time. The digeneans and copepods were the best-represented parasite groups. The parasite communities were characterized by a high numerical dominance of ectoparasites, mainly isopod larvae. Species richness at the component community level (9-23 species) was similar to the reported richness in other Lutjanus spp. The parasite communities of Lutjanus argentiventris exhibited high variability in species composition, suggesting that each parasite species may respond differently to environmental changes. However, the species richness and diversity were fairly stable over time; therefore, a clear pattern of interannual variation was not observed. Variations in the community structure probably were due to factors such as host traits (e.g., feeding behavior and body size), and possible interannual differences in environmental factors amplified by the occurrence of the anomalous event of La Niña.

High‐resolution spectral data predict taxonomic diversity in low diversity grasslands

Abstract Mitigating impacts of global change on biodiversity is a pressing goal for land managers, but understanding impacts is often limited by the spatial and temporal constraints of traditional in situ data. Advances in remote sensing address this challenge, in part, by enabling standardized mapping of biodiversity at large spatial scales and through time. In particular, hyperspectral imagery can detect functional and compositional characteristics of vegetation by measuring subtle differences in reflected light. The spectral variance hypothesis (SVH) expects spectral diversity, or variability in reflectance across pixels, to predict vegetation diversity. However, the majority of research testing the SVH to date has been conducted in systems with controlled conditions or spatially homogenous assemblages, with little generalizability to heterogeneous real‐world systems. Here, we move the field forward by testing the SVH in a species‐rich system with high heterogeneity resulting from variable species composition and a recent fire. We use very high spatial resolution (~1 mm) hyperspectral imagery to compare spectrally derived estimates of vegetation diversity with in situ measures collected in Boulder, CO, USA. We find that spectral diversity and taxonomic diversity are positively correlated only for low to moderate diversity transects, or in transects that were recently burned where vegetation diversity is low and composed primarily of C3 grasses. Additionally, we find that the relationship between spectral and taxonomic diversity depends on spatial resolution, indicating that pixel size should remain a priority for biodiversity monitoring. Practical implication: The context dependency of this relationship, even with high spatial resolution data, confirms previous work that the SVH does not hold across landscapes and demonstrates the necessity for repeated, high‐resolution data in order to tease apart the biological conditions underpinning the SVH. With refinement, however, the remote sensing techniques described here will offer land managers a cost‐effective approach to monitor biodiversity across space and time.

Drivers of β-diversity and its component-dependence along the natural restoration in an extremely heterogeneous forest ecosystem

β-diversity usually refers to species turnover along a gradient or changes in species diversity between communities. It is a key concept in understanding the mechanisms of biodiversity pattern formation. However, the component dependence and the driving factors of β-diversity during natural restoration remain unclear. In this study, a series of forest dynamic plots (FDPs) were established through the natural restoration stages in degraded karst forests, including the shrub-canopy mixed forest stage (SC), the secondary-growth forest stage (SG), and the old-growth forest stage (OG). After comparing species composition during natural restoration and its dependence on species turnover and nestedness, it was found that natural restoration significantly influenced the species composition by altering the species turnover in degraded karst forests rather than the nestedness. The contribution of turnover to β-diversity gradually increased, while the contribution of nestedness decreases gradually. Furthermore, the PER-SIMPER method was used to quantify the first-order assembly process that drives variations in species composition during restoration stages. To identify the factors influencing β-diversity, both variation partitioning analysis and a random forest model were employed. The results suggested that differences in species compositions across restoration stages were mainly driven by stochastic processes, and the deterministic processes were strengthened during the natural restoration. In addition, topographic factors contributed more to β-diversity than soil nutrient factors. This study highlighted changes in component dependence of degraded karst forests during natural restoration and emphasized the importance of a more comprehensive framework in assessing the restoration of degraded forest ecosystems. More attention should be paid to topographic structure in understanding biodiversity patterns, especially in highly heterogeneous forest ecosystems.

Phytosociological Study of Tree Species of Dabla Beed Area, Churu District Rajasthan, India

This study presents a comprehensive phytosociological analysis of tree species in the Dabla beed area of Churu District, Rajasthan, India, exploring seasonal variations in species composition, diversity, dominance, and evenness. The research was conducted across three seasons: rainy, winter, and summer, utilizing quadrat sampling methods to assess various ecological parameters. The findings reveal distinct seasonal shifts in the dominance and distribution of key species. During the rainy season, species such as Acacia senegal and Acacia tortilis exhibit high dominance and contribute to elevated species diversity and evenness. In winter, Maytenus emarginata and Acacia senegal emerge as prominent species, maintaining moderate diversity with increased dominance. The summer season sees a notable decline in diversity and evenness, accompanied by heightened dominance, with Calotropis procera and Clerodendrum phlomidis being particularly influential. These seasonal dynamics underscore the importance of adaptive management and conservation strategies to maintain the ecological integrity and biodiversity of the tree community in this arid region. The study highlights the critical need for targeted conservation efforts to ensure the sustainability of the diverse and dynamic tree populations in the Dabla beed area.

Seasonality and relative abundance within an elasmobranch assemblage near a major biogeographic divide.

Nearshore waters are utilized by elasmobranchs in various ways, including foraging, reproduction, and migration. Multiple elasmobranch species have been previously documented in the nearshore waters of North Carolina, USA, which has a biogeographic break at Cape Hatteras on the Atlantic coast. However, comprehensive understanding of the elasmobranch community in this region is still lacking. Monthly year-round trawling conducted along two ocean transects (near Cape Lookout and Masonboro Inlet in 5 to 18 m depth) in Onslow Bay, North Carolina provided the opportunity to examine the dynamics and seasonal patterns of this community using a multivariate approach, including permutational multivariate analysis of variance and nonparametric BIO-ENV analysis. From November 2004 to April 2008, 21,149 elasmobranchs comprised of 20 species were caught, dominated by spiny dogfish (Squalus acanthias) and clearnose skate (Rostroraja eglanteria). All species exhibited seasonal variation in abundance, but several key species contributed the most to seasonal differences in species composition within each transect. Spiny dogfish was most abundant in the winter at both locations, comprised mainly of mature females. Although clearnose skate was caught in all seasons, the species was most abundant during the spring and fall. Atlantic sharpnose (Rhizoprionodon terraenovae) was one of the most abundant species in the summer, and two distinct size cohorts were documented. Temperature appeared to be the main abiotic factor driving the community assemblage. The extensive year-round sampling provided the ability to better understand the dramatic seasonal variation in species composition and provides new information on the relative abundance of several understudied elasmobranch species that may be of significant ecological importance. Our results underscore the importance of inner continental shelf waters as important elasmobranch habitat and provide baseline data to examine for future shifts in timing and community structure at the northern portion of the biogeographic break at Cape Hatteras.

Within-well patterns in bigeye tuna catch composition and implications for purse-seine port-sampling and catch estimation for the Eastern Pacific Ocean

In response to concerns about the stock status of bigeye tuna (BET) in the Eastern Pacific Ocean, the Inter-American Tropical Tuna Commission adopted additional management measures for BET in 2021, including an individual-vessel catch threshold system for the purse-seine fishery. Development of an enhanced port-sampling program for estimation of trip-level BET catch was also mandated to support member countries and their purse-seine vessels in their conservation efforts. To this end, a pilot study was conducted in the ports of Manta and Posorja, Ecuador, in 2022. In these ports, well unloading often takes place with small containers, which are used to transport fish from inside the well to the vessel’s wet deck. Using a high-frequency systematic sampling protocol, 63 wells of 37 trips with catch exclusively from floating-object (OBJ) sets were sampled from the start to the end of unloading, at a fixed interval from a random starting point, sampling about 10 % of all the containers of fish unloaded from each well. Notable large-scale pattern in the proportion of BET per container was found for 38 of the 56 wells that had BET catch. The proportion of BET per container, which could be high at the beginning, middle or end of the well unloading, sometimes varied by 0.40 or more. The magnitude of this large-scale within-well pattern had a significant increasing relationship with the number of OBJ sets associated with the well catch, consistent with variability in species composition among OBJ sets being an important factor in determining variability in species composition during catch unloading. Simulation studies demonstrated that such large-scale within-well pattern has potential implications for OBJ-set well-level sampling design, where, as expected from sampling theory, a systematic sampling protocol for containers of fish generally resulted in lower mean squared error (MSE) on the proportion of BET in the well, compared to simple random sampling of containers of fish. The reduction in MSE was largely due to a reduction in variance. Simulations also showed that the within-well variance component of the trip-level estimator for the proportion of BET can be larger than the among-well variance component, unless the within-well sampling coverage is relatively high. To minimize the negative impact of within-well variability on the precision of the estimator, results indicate that for a sampling protocol with one systematic sample per well, the within-well coverage should be at least 2 % of containers of fish unloaded from the well, and preferably more than 3 %. Finally, simulation studies were conducted with observer well plan data from 2013 to 2022 to put the well-level results in a larger context. Results indicated that the level of within-well sampling coverage may affect the variance on fleet-level estimates of the proportion of BET in the catch, with potentially substantially higher variance when the within-well sampling coverage is low. Taken together, these results suggest that both the type of within-well sampling and the level of within-well sampling coverage have important implications for the variance on BET catch estimates, from the well level to the fleet level.

Untangling the complex food webs of tropical rainforest streams.

Food webs depict the tangled web of trophic interactions associated with the functioning of an ecosystem. Understanding the mechanisms providing stability to these food webs is therefore vital for conservation efforts and the management of natural systems. Here, we first characterised a tropical stream meta-food web and five individual food webs using a Bayesian Hierarchical approach unifying three sources of information (gut content analysis, literature compilation and stable isotope data). With data on population-level biomass and individually measured body mass, we applied a bioenergetic model and assessed food web stability using a Lotka-Volterra system of equations. We then assessed the resilience of the system to individual species extinctions using simulations and investigated the network patterns associated with systems with higher stability. The model resulted in a stable meta-food web with 307 links among the 61 components. At the regional scale, 70% of the total energy flow occurred through a set of 10 taxa with large variation in body masses. The remaining 30% of total energy flow relied on 48 different taxa, supporting a significant dependency on a diverse community. The meta-food web was stable against individual species extinctions, with a higher resilience in food webs harbouring omnivorous fish species able to connect multiple food web compartments via weak, non-specialised interactions. Moreover, these fish species contributed largely to the spatial variation among individual food webs, suggesting that these species could operate as mobile predators connecting different streams and stabilising variability at the regional scale. Our results outline two key mechanisms of food web stability operating in tropical streams: (i) the diversity of species and body masses buffering against random and size-dependent disturbances and (ii) high regional diversity and weak omnivorous interactions of predators buffering against local stochastic variation in species composition. These mechanisms rely on high local and regional biodiversity in tropical streams, which is known to be strongly affected by human impacts. Therefore, an urgent challenge is to understand how the ongoing systematic loss of diversity jeopardises the stability of stream food webs in human-impacted landscapes.

Evaluation of shrimp-associated species in abandoned ponds in Mati City, Philippines

This study aimed to identify, characterize, and evaluate the biodiversity of shrimp-associated species in abandoned shrimp ponds, specifically assessing the trophic levels of bycatch species in Barangay Dahican, Mati City. Using a scoop net, researchers collected macrobenthic samples from Maitum, Lahusan, and Butuasan, finding 1,528 individuals with varying species compositions namely: Oreochromis niloticus (Nile tilapia), Coenobita cavipes (Land hermit crab), Canarium labiatum (Plicate conch), Rochia nilotica (Commercial top), Clithon oualaniense (Guamanian nerite), Cerithium coralium (Coral cerith), and Callinectes sapidus (Blue crab). Cerithium coralium was the most abundant species with 70% relative abundance, followed by Clithon oualaniense, with 29%. In contrast, the least abundant species were the Oreochromis niloticus and Canarium labiatum, with 1% relative abundance. Moreover, biodiversity indices revealed that Lahusan 1 (H' = 0.731; D=0.46) and Butuasan (H' = 0.714; D = 0.5) had higher biodiversity, whereas Lahusan 2 had the lowest (H' = 0.318; D = 0.15). In contrast, Lahusan 2 appeared to be the least diverse (H' = 0.318; D = 0.15). There were significant differences in terms of species abundance (df = 6, MS = 34.18, F = 6.02, P = 0.000) and none in terms of site locations (df = 3, MS = 18.71, F=2.08, P= 0.188). The study results showed that these associated species were mainly benthic and came from the nearby environment. Providing good management for the abandoned shrimp ponds in the area could mean reverting them to their original state to provide a habitat for other organisms.

Validation and development of eDNA metabarcoding primers for comprehensive assessment of Chinese amphibians.

Environmental DNA (eDNA) metabarcoding has emerged as a powerful, non-invasive tool for biodiversity assessments. However, the accuracy and limitations of these assessment techniques are highly dependent on the choice of primer pairs being used. Although several primer sets have been used in eDNA metabarcoding studies of amphibians, there are few comparisons of their reliability and efficiency. Here, we employed lab- and field-tested sets of publicly available and de novo-designed primers in amplifying 83 species of amphibian from all three orders (Anura, Caudata, and Gymnophiona) and 13 families present in China to evaluate the versatility and specificity of these primers sets in amphibian eDNA metabarcoding studies. Three pairs of primers were highly effective, as they could successfully amplify all the major clades of Chinese amphibians in our study. A few non-amphibian taxa were also amplified by these primers, which implies that further optimization of amphibian-specific primers is still needed. The simultaneous use of three primer sets can completely cover all the species obtained by conventional survey methods and has even effectively distinguished quite a number of species (n = 20) in the Wenshan National Nature Reserve. No single primer set could individually detect all of the species from the studied region, indicating that multiple primers might be necessary for a comprehensive survey of Chinese amphibians. Besides, seasonal variations in amphibian species composition were also revealed by eDNA metabarcoding, which was consistent with traditional survey methods. These results indicate that eDNA metabarcoding has the potential to be a powerful tool for studying spatial and temporal community changes in amphibian species richness.

Multi-year three-dimensional simulation of seasonal variation in phytoplankton species composition in a large shallow lake

Lake Erie has been negatively impacted by multiple stressors, including nutrient enrichment and climate change, that have exacerbated eutrophication and harmful algal blooms. Management of these long-term water quality problems requires numerical models that can be run over years to decades. The three-dimensional hydrodynamics and biogeochemistry models applied to date, however, have not been tested for continuous runs longer than one year and have not been shown to accurately reproduce seasonal variation in phytoplankton species composition (e.g., the development of harmful algal blooms) over decadal timescales. We simulated the three-dimensional nutrient and phytoplankton concentrations in western Lake Erie continuously from 2002 to 2014. Using a single parameter set, we were able to reproduce both seasonal and inter-annual variation in phytoplankton species composition. The model qualitatively reproduced the observed seasonal succession (i.e., variation in phytoplankton species composition), including the spring diatom bloom and late summer cyanobacterial growth. This study demonstrates that three-dimensional models can be applied for multi-year simulations of nutrients and phytoplankton to inform large lake research and management.

Above Ground Biomass and Carbon Sequestration of Urban Green Spaces in Danang City, Vietnam

Green space in cities is an essential component of the urban environment. Different forms of urban green spaces, with varying populations, plant communities, and roles, offer varying urban ecological advantages. Using the i-Tree Eco model, this study examined the structural characteristics of urban green trees and calculated the biomass storage capacity and carbon sequestration in urban green spaces in Da Nang City. The results revealed a considerable diversity of species composition among 7,513 trees belonging to 42 species of 20 families studied in four types of green spaces, with Terminalia catappa, Cyrtostachys renda, and Roystonea regia dominating. The average Shannon biodiversity index was 2.9, with the institution having the highest at 2.6 and the park having the lowest at 2.2. The total leaf biomass per hectare was 588.0 kg/ha, and the carbon sequestration rate was 2,845.30 kg/ha. Ficus subpisocarpa was the species with the highest value for these two advantages, and the park was the green space with the highest benefit in terms of biomass and carbon sequestration.

Determinants of taxonomic, functional, and phylogenetic beta diversity in breeding birds within urban remnant woodlots: Implications for conservation.

Examining beta diversity of animal assemblages in fragmented habitats, which measures variation in species composition among different fragments, is important for understanding the impact of habitat fragmentation on biodiversity. However, relying solely on taxonomic composition may not provide a comprehensive understanding. Incorporating measures of functional and phylogenetic diversities is essential for elucidating the ecological mechanisms underlying changes in community composition. In addition, prevailing studies often prioritize the evaluation of landscape characteristics within fragments as determinants of beta diversity, neglecting differences in habitat type and plant community composition. In this study, we surveyed birds in 26 remnant woodlot patches (ranging from 0.3 to 290.4 ha) in an urban landscape, southwest China, during the breeding season from 2017 to 2022. We recorded 70 bird species (excluding those recorded only once and high-flying birds, including raptors, swallows, and swifts), with the number of species per patch varying from 14 to 56. The overall bird taxonomic and phylogenetic beta diversities were primarily contributed by the turnover component, while functional beta diversity was dominated by the nestedness-resultant component. Patch area and perimeter area ratio significantly influenced the taxonomic, functional, and phylogenetic beta diversities, primarily mediated through the nestedness-resultant component, while inter-patch distance had a significant effect via the turnover component. In addition, there was a considerable correlation of bird taxonomic, functional, and phylogenetic beta diversities with habitat type and woody plant beta diversities, including their respective partitioned turnover and nestedness-resultant components. Our results suggest that bird assemblages in these patches may be regulated by selective extinction, interspecific competition, and environmental filtering. The findings have significant implications for sustainable landscape planning and habitat restoration. Conserving habitat patches of different sizes and maintaining or enhancing habitat heterogeneity between patches can facilitate the persistence of metacommunities.

Plant and soil microbial community assembly processes across urban vacant lots

AbstractQuestionsNumerous studies on community assembly processes have been conducted in natural ecosystems. However, we know little about community assembly processes in human‐dominated urban ecosystems. Here, we asked: (1) how are the composition and functional diversity of native and exotic plant species shaped by local environment and landscape factors across urban vacant lots; and (2) how is microbial (bacterial and fungal) community composition influenced by the local environment, landscape factors, and plant species composition across urban vacant lots?LocationWe investigated 69 urban vacant lots in Yokohama, Japan.MethodsBy using a variation partitioning approach, we examined the relative importance of local environmental and landscape factors (including land use and spatial structure) in explaining variation in plant species composition and functional diversity of native or exotic species. We also explored the relative importance of local environmental and landscape factors, and plant species composition in explaining variation in microbial community composition.ResultsThe spatial structure of vacant lots determined the species composition and functional diversity of plant communities, suggesting that plant community assembly is determined by dispersal limitation. However, the functional diversity of the exotic species varied randomly, which reduced the relative importance of the spatial structure of vacant lots. Plant species composition as well as the spatial structure of vacant lots were the important drivers of the composition of soil microbial communities, despite a higher proportion of unexplained variation in their composition. Finally, we found an essential contribution of earthmoving methods in explaining the variations in both plant and microbial community composition.ConclusionPlant and microbial community composition would be largely determined by dispersal limitation across urban vacant lots. Understanding urban community assembly is critical for predicting plant and microbial communities that play an essential role in regulating urban ecosystem functioning and services.

Environmental DNA recovers fish composition turnover of the coral reefs of West Indian Ocean islands.

Islands have been used as model systems to study ecological and evolutionary processes, and they provide an ideal set-up for validating new biodiversity monitoring methods. The application of environmental DNA metabarcoding for monitoring marine biodiversity requires an understanding of the spatial scale of the eDNA signal, which is best tested in island systems. Here, we investigated the variation in Actinopterygii and Elasmobranchii species composition recovered from eDNA metabarcoding along a gradient of distance-to-reef in four of the five French Scattered Islands in the Western Indian Ocean. We collected surface water samples at an increasing distance from reefs (0 m, 250 m, 500 m, 750 m). We used a metabarcoding protocol based on the 'teleo' primers to target marine reef fishes and classified taxa according to their habitat types (benthic or pelagic). We investigated the effect of distance-to-reef on β diversity variation using generalised linear mixed models and estimated species-specific distance-to-reef effects using a model-based approach for community data. Environmental DNA metabarcoding analyses recovered distinct fish species compositions across the four inventoried islands and variations along the distance-to-reef gradient. The analysis of β-diversity variation showed significant taxa turnover between the eDNA samples on and away from the reefs. In agreement with a spatially localised signal from eDNA, benthic species were distributed closer to the reef than pelagic ones. Our findings demonstrate that the combination of eDNA inventories and spatial modelling can provide insights into species habitat preferences related to distance-to-reef gradients at a small scale. As such, eDNA can not only recover large compositional differences among islands but also help understand habitat selection and distribution of marine species at a finer spatial scale.

Larval dynamics suggest phenological strategies and positive effect of marine protected areas controlling indigenous and non-indigenous crab populations

The early life of most decapod crustaceans takes place in the water column as larvae before they settle in benthic habitats. The spatial and temporal variability in the settling of larval stages offers valuable insights into the potential recruitment of natural populations. To explore this, we studied megalopa assemblages at various segments of coastline on El Hierro and Lanzarote islands, both within and outside the Marine Protected Areas (MPAs) of each island. The study spanned four consecutive oceanographic periods in the Canary Islands (NW Africa), employing light traps for sample collection. The low number of recorded species suggested that light traps exhibit selectivity, particularly for megalopae belonging to Portunidae and Grapsidae. El Hierro, which experienced warmer sea surface temperatures, displayed higher megalopa abundance values than Lanzarote and distinct larval assemblages was observed between these two islands. Similarly, we identified significant variations in abundance and species composition between stratified and mixing seasons. These seasonal differences were influenced by the dominance of Achelous hastatus, Percnon gibessi, and Cronius ruber during the stratified season. In Lanzarote, C. ruber was not recorded during the mixing season, suggesting that the colder conditions there may constrain its reproduction. Interestingly, we observed that species traditionally harvested from the intertidal zone for human consumption (Plagusia depressa) or used as bait for recreational fishing (Pachygrapsus spp. and P. gibessi) exhibited higher megalopa abundances within the MPAs. In contrast, we noted lower megalopa densities of the non-indigenous species C. ruber within the protected areas. These results indicate a positive effect of MPAs controlling indigenous and non-indigenous crab populations. Moreover, the study provides novel data, showing that light traps are suitable for monitoring the temporal occurrence, abundance, and spatial distribution of non-indigenous and commercially exploited species. This is key for adopting an ecosystem-based approach to manage marine resources.

Divergence of zooplankton assemblages in unstable fishless and stable fish ponds

This study aimed to achieve a better understanding of the features of zooplankton assemblages in small water bodies and their biodiversity and composition in relation to the presence of fish and accompanying environmental characteristics. This study was conducted in 16 mid-field ponds. Compositional and biodiversity indexes and ordination methods were used to analyze the relationship between zooplankton assemblages in unstable fishless and stable fish ponds. A total of 121 zooplankton taxa were identified. Compositional indicators revealed significant differences in zooplankton assemblages between fish ponds (FPs) and fishless ponds (FLPs). Canonical correspondence analysis indicated that variation in zooplankton assemblages depended on the ponds’ features. Most of the high trophic state indicator species were present only in FPs or occurred sporadically in FLPs. Rarefaction and extrapolation indicated a higher number of zooplankton taxa in FPs than in FLPs. The stability of the ecosystem was essential for maintaining the high species richness of zooplankton. Diversity indices were not influenced by variations in species composition or environmental differences among ponds. Diversified pond types are necessary to maintain the heterogeneity of mid-field ponds, which support the high regional biodiversity of zooplankton assemblages.

Seasonal species composition, abundance and public health importance of mosquito vectors (Diptera: Culicidae) in Huai Tha Khoei Reservoir, Ratchaburi, Thailand

Abstract. Chaiphongpachara T, Laojuna S. 2024. Seasonal species composition, abundance and public health importance of mosquito vectors (Diptera: Culicidae) in Huai Tha Khoei Reservoir, Ratchaburi, Thailand. Biodiversitas 25: 1264-1275. Mosquitoes are vectors for pathogens that cause life-threatening diseases in humans and animals. Significant mosquito-borne diseases include malaria, dengue, chikungunya, Zika, Japanese encephalitis, and filariasis. Anthropogenic environmental changes can significantly impact the dynamics of disease vector populations, which can lead to outbreaks of mosquito-borne diseases. This study investigated the seasonal variation in species composition and abundance of mosquito vectors around the Huai Tha Khoei Reservoir in Ratchaburi Province, Thailand, across cool, hot, and rainy seasons. A total of 1363 mosquitoes, representing 30 species from five genera, were collected. In particular, 25 of these species, accounting for 83.33% of the total, were identified as vectors of human pathogens. The most dominant species across all seasons was Culex tritaeniorhynchus Giles 1901, representing 39.47% (n=538) of the total, followed by Anopheles barbirostris Wulp 1884 s.l. (14.38%, n = 196) and Culex vishnui Theobald 1901 (9.02%, n=123). The Shannon diversity index was highest during the rainy season (H’= 2.144) and lowest in the hot season (H’=1.788). This is consistent with the results of the UPGMA tree based on beta diversity, indicating that mosquito diversity in the rainy season differs significantly from that in the cool and hot seasons. The findings enhance our understanding of the impact of seasonality on mosquito vectors in this region, which is crucial for developing effective disease control strategies. Additionally, this study serves as a valuable reference for understanding the diversity of mosquito vectors in other areas.