Lower Species Richness Research Articles

Mycorrhizal dominance influences tree species richness and richness-biomass relationship in China's forests.

Mycorrhizal associations drive plant community diversity and ecosystem functions. Arbuscular mycorrhiza (AM) and ectomycorrhiza (EcM) are two widespread mycorrhizal types and are thought to differentially affect plant diversity and productivity by nutrient acquisition and plant-soil feedback. However, it remains unclear how the mixture of two mycorrhizal types influences tree diversity, forest biomass, and their relationship at large spatial scales. Here, we explored these issues using data from 1247 plots (600 m2 for each) across China's natural forests located mostly in temperate and subtropical regions. Both AM-dominated and EcM-dominated forests show relatively lower tree species richness and stand biomass, whereas forests with the mixture of mycorrhizal strategies sustain more tree species and higher biomass. Interestingly, the positive effect of tree diversity on biomass is stronger in forests with low (≤50%) than high AM tree proportion (>50%), reflecting a shift from the complementarity effect to functional redundancy with increasing AM trees. Our findings suggest that mycorrhizal dominance influences tree diversity and richness-biomass relationship in forest ecosystems.

ECOLOGICAL INDICES OF MANGROVE GASTROPODS COMMUNITY IN NICKEL MINING IMPACTED AREA OF POMALAA, SOUTHEAST SULAWESI

Article Highlights- Gastropods (Invertebrates: Mollusca) have the potential to be developed as biological indicators of the health of coastal aquatic environments- The development of gastropod communities has been proven to provide a significant ecological response in assessing environmental quality in the mangrove in relation to overburden waste input from nickel mining activities.- Overburden waste systemically degrades the ground floor (substrate) of the mangrove ecosystem as an area where the entire life cycle of the gastropod community is carried out.AbstractThis research aimed to determine the structure of gastropod community in the nickel mining impact area in the mangrove ecosystem of Tambea Village, Pomalaa District, Southeast Sulawesi Province. The scope of this research was gastropod community influenced by nickel mining activities, especially the impact of overburden waste input (reddish-orange colored sediment) toward the health status of the aquatic environment based on the ecological indices of the gastropod community in the mangrove ecosystem of Tambea Village. Two sampling methods were adopted in this research: (1) purposive sampling method to determine stations (locus) and (2) simple random sampling method to determine the distribution of substations or sampling points. Gastropod samples were taken using handpicking techniques. The structure of gastropod community in mangrove area affected by overburden waste showed low diversity index values (H’ = 0.81), low species richness (R = 1.75), moderate evenness (E = 0.50), and dominance of certain species (C = 0.54). The results of this research showed the massive impact of overburdened waste, which can systemically degrade the life of the typical fauna that make up the mangrove ecosystem. Three gastropods species were observed to live in the research location, namely Telescopium telescopium, Terebralia sulcata, and Terebralia palustris having low abundance (1-9 ind./m2) which can survive in environment exposed to overburden waste. Many of gastropod species were found dead, indicated by the finding of 2 shells of Ellobium aurisjudae. The input of overburdened waste may imply degradation system of the aquatic environment, especially in the mangrove ecosystem. This research offers outlooks of overburden waste on aquatic biota in mangrove ecosystems and other complimentary ecosystems. In the end, the condition of the gastropod community in a watered area becomes a basis of the health status of the water environment.

Spatiotemporal Changes and Recovery of Benthic Macroinvertebrate Communities after the Hebei Spirit Oil Spill in the Subtidal Area around the Taean Peninsula in South Korea

Marine oil pollution is a significant environmental issue that significantly threatens ocean ecosystems. It occurs frequently and has devastating consequences for marine life, coastal habitats, and human communities. We examined the recovery of benthic macroinvertebrate communities in shallow subtidal areas following the Hebei Spirit oil spill around the Taean Peninsula, South Korea, in 2007. Benthic macroinvertebrates were collected seasonally from 15 survey sites between 2008 and 2015. Immediately after the spill in 2008, species richness and density of benthic macroinvertebrates decreased by 66.7% and 37.0%, respectively, compared to before the oil spill in 2007. Cluster analysis based on benthic macroinvertebrate communities delineated the communities from 2008 to 2009 as a distinct cluster characterized by markedly low species richness. Communities from other periods exhibited spatiotemporal variability based on the sampling location and sediment characteristics. By 2011, species richness and density had recovered to levels similar to those in 2007, which was particularly pronounced regarding the resurgence of arthropods and mollusks. Notably, populations of amphipods that are particularly sensitive to oil, such as Urothoe sp. and Byblis spp., showed signs of recovery in 2011; however, recovery of the benthic community at the site nearest to the oil spill area, was not evident until July 2013, as indicated by the benthic opportunistic polychaete amphipod index. This underscores that prolonged time periods are required for communities to fully recuperate after oil spills.

Effects of farming intensification on avian species richness and abundance within Jos metropolis, Nigeria

With an emphasis on pesticide use and landscape features, this study examines how agricultural development affects the diversity and abundance of farmland bird species. The purpose of the study is to evaluate the effects of many factors on bird populations, including cropping patterns, pesticide frequency, and landscape elements including trees, water bodies, hedgerows, and grass cover. The issue being addressed is the decline in biodiversity brought on by an increase in farming practices and a reliance on pesticides that upset ecosystems. The study uses interviews in addition to line transect surveys over five farmlands to collect data on pesticide use and landscape features. The methodology comprised 200-meter transects separated into 100-meter parts for morning and evening bird surveys. Statistical approaches, including species richness and abundance comparison across farmlands with different pesticide use levels and cropping techniques, were used to analyse the data. The results showed that farmlands without pesticides had better biodiversity, while areas with frequent pesticide usage had significantly lower species richness and abundance. Bird diversity was only slightly increased by mixed cropping systems, grass cover, trees, hedgerows, and adjacent water bodies. The study comes to the conclusion that fostering diverse landscapes and lowering pesticide use can help lessen the loss of biodiversity. To improve agricultural bird conservation, it suggests focused interventions, education initiatives, and policies that support biodiversity.

Biodiversity and relative abundance of benthic invertebrates in the intertidal of Taraba Sound, Magellan Region, Chile.

The Taraba Sound is situated north of the Strait of Magellan within the Chilean fjord and channel system. In this inlet, samples were collected at three beach levels (supralittoral, mesolittoral and infralittoral) along four transects perpendicular to the coastline. A total of 2,754 specimens were collected and identified, representing seven phyla and 24 operational taxonomic units (OTUs). The dominant components across the four beaches were bivalves and crustaceans, with Choromytiluschorus and Paramoeracf.fissicauda contributing significantly to zone similarity. Beaches 2 and 4, located adjacent to river mouths, had lower salinity and consequently lower species richness, abundance, diversity and evenness, particularly in the supra- and mesolittoral zones where freshwater influence is more pronounced. Our study represents the first comprehensive characterisation of intertidal benthic invertebrate biodiversity in the region. Its findings provide valuable baseline data for future research, especially considering the anticipated increase in aquaculture concession applications and the establishment of offshore sea farming centres in the region.

Immediate Response of Carabids to Small-Scale Wildfire Across a Healthy-Edge-Burnt Gradient in Young Managed Coniferous Forest in Central Europe

Wildfire is a type of disturbance that plays a critical role in affecting forest ecosystems. Wildfires also have a significant effect on shaping arthropods communities. Carabids (family Carabidae) are often used as a bioindicator group of altered biocenoses. Methods: For carabid sampling, pitfall traps were used in three habitats, healthy-edge-burnt, fifteen days after the suppression of wildfire. Seven traps were evenly placed on each transect. In total, twenty-one traps were used for the study. Aim of the study: (i) evaluate the overall diversity of carabids, (ii) sex change and distribution within the studied habitats, (iii) dynamics of pyrophilous carabids. Results: In total, 1051 individuals within 42 species were recorded. The total number of species was higher in the edge and burnt habitats and differed from the healthy habitat. The abundance of carabids did not differ significantly across the three habitats. However, the healthy habitat exhibited both lower species numbers and abundance. Communities, species richness, and diversity indices were similar in the edge and burnt habitats, while the healthy habitat had lower species richness, diversity indices, and more homogenized communities. The overall sex ratio was nearly equal, with females comprising 519 individuals (49.4%) and males 532 individuals (50.6%), showing nonsignificant differences among study habitats. Among the nine most dominant species, a general trend of female dominance was observed. Many species showed different patterns in sex distribution in relation to the study habitats. Pyrophilous species accounted for the majority of individuals, comprising 55% of all carabids in the burnt habitat, predominantly represented by Pterostichus quadrifoveolatus. The rare species Sericoda quadripunctata was observed infrequently with only twenty-three individuals recorded. These two species are highly correlated, potentially indicating their near-habitat requirements. Males of pyrophilous species in general colonize the area in the earliest post-fire period. Conclusions: The immediate response of carabids to forest wildfire is significant, primarily influencing species richness and communities. While wildfire did not affect overall sex distribution, it shaped interspecies sex distribution across the study habitats.

Comparison of Environmental DNA Metabarcoding and a Traditional Survey Method for Assessing Fish Diversity and Distribution Along Salinity Gradient in an Urban Brackish Reservoir, China.

With the decrease in fish diversity, the monitoring of fish has become a current research hotspot. Here, the fish diversity and spatial distribution along a salinity gradient (0.28‱-3.32‱) in Xinglinwan Reservoir, China, were investigated using eDNA and the TSM. With the combination of both methods, 12 species from 6 orders, 9 families, and 11 genera were observed. The invasive species Oreochromis niloticus had the highest relative abundance, accounting for 56.91% in the TSM and 89.80% in eDNA, respectively. eDNA detected 83.33% of the species detected using the TSM, and an additional six species (50.0% of the total species) were detected via only eDNA. Moreover, eDNA supplemented the unavailable abundance data from the TSM. The TSM revealed that the diversity and relative abundance of fish inhabiting seawater and brackish water increased with an increase in salinity, but this was not found using eDNA. Thus, our study highlights that Xinglinwan Reservoir has a low species richness and is suffering from the great harm of ecological invasion. Our findings also show that eDNA could be reliable for providing a comprehensive picture of fish, but discriminating the spatial heterogeneity of fish communities is a challenge for its widespread adoption in lentic brackish systems.

Suitability of invasive gobies as paratenic hosts for acanthocephalans of the genus Pomphorhynchus sp.

Ponto-Caspian gobies became highly abundant in many regions outside their native distribution range (e.g. in the Rhine River system). In the newly invaded habitats, the parasite communities of the invasive gobies are characterized by a lower species richness compared to their native range. Interestingly, acanthocephalans of the genus Pomphorhynchus are highly abundant, although they do not become mature and mostly remain encapsulated in the abdominal cavity as preadults. Thus, gobiids could either represent a dead-end host for Pomphorhynchus sp. declining its population (dilution effect) or act as a paratenic host that could increase the infection pressure if the infected gobies are preyed upon by appropriate definitive hosts (spill back). To determine which of the 2 scenarios the gobiids contribute to, we conducted 2 infection experiments using smaller and larger individuals of the definitive host chub (Squalius cephalus), infected with preadults of Pomphorhynchus sp. collected from the abdominal cavity of Neogobius melanostomus. The results showed that preadults were able to complete their development and mature in the definitive host with mean recovery rates of 17.9% in smaller and 27.0% in larger chubs. Successful infections were observed in 62.0% and 80.0% of the smaller and larger chubs, respectively. Our study demonstrated that gobies can theoretically serve as a paratenic host for acanthocephalans of the genus Pomphorhynchus, and that infection might spill back into the local fish community if infected gobies are preyed upon by suitable definitive hosts of Pomphorhynchus sp. such as large barbel or chub.

Nutrients, isolation and lack of grazing limit plant diversity in restored wetlands

Abstract Agricultural intensification has led to the loss of most natural wetlands from human‐dominated landscapes but, in recent decades, wetland restoration has gained traction worldwide. Restoration of suitable habitat conditions is hampered by nutrient residues from decades of high‐input farming, by continued input of nutrients from surrounding farmland and by incomplete restoration of natural hydrology. We assessed the effect of wetland restoration and disturbance (grazing) on vascular plant and bryophyte diversity in restored wetlands in Denmark at plot and landscape scales. Compared to near‐natural wetlands, we found a lower species richness and community uniqueness in restored wetlands, but we also found that grazing had a positive effect on vascular plant richness in restored wetlands. The size of the local species pool, presence of near‐natural habitat prior to restoration and near‐natural restored hydrology all had positive effects on plant diversity, whereas high soil iron and nitrogen had negative effects. Synthesis and applications: Restoration of plant diversity in wetlands is challenging, but our results point to potential remedies: plan restoration areas near colonisation sources of the target biota, restore hydrology to near‐natural conditions, discontinue nutrient loads from surrounding arable land and restore near‐natural grazing regimes. Bryophytes may be particularly useful as indicators for successful restoration of wetlands.

Effects of weed management on soil metagenomic composition in cultivated chickpea fields

Abstract Non-chemical methods, including mechanical and manual weed management are important for improving crop yields and preserving soil microbial diversity. In Tunisia, chickpea cultivation uses a combination of these methods to suppress weeds. This study aimed to evaluate the impact of weeding practices on chickpea (Cicer arietinum L. cultivar REBHA) yield and soil microbial diversity. Field experiments were conducted at the Technical Center for Biological Agriculture in Essaida, Tunisia, using six plots with manual and no weeding treatments. Chickpea yield was measured, and soil samples were collected for metagenomic analysis. Floristic surveys identified 13 weed species, with Chenopodium album L., Rumex acetosa L., and Urtica dioica L. being the most dominant. Seed yield ranged from 23.2 to 26.2 qls/ha in non-weeded plots and from 25.1 to 30.1 qls/ha in weeded plots, showing an increase in yield (11.75%) with manual weeding.
Soil metagenomics revealed changes in bacterial community composition between the two treatments. The dominant phylum was Pseudomonadota, whose relative abundance increased from 24.88% in non-weeded plots to 34.76% in weeded plots. Alpha diversity indices showed lower species richness and diversity in weeded soils, with 62000 OTUs in weeded plots compared to 43202 OTUs in non-weeded plots. Betaproteobacteria and Alphaproteobacteria exhibited higher OTU counts in weeded soils. The Simpson diversity index was lower in non-weeded soils (0.025) than in weeded soils (0.075), indicating a more irregular microbial distribution in non-weeded plots. Thus, manual weeding improved chickpea yield and altered the soil bacterial community, increasing diversity in key microbial taxa. This study highlights the complex interaction between weed management practices and soil microbial ecosystems, which may influence crop productivity.

High functional vulnerability across the world’s deep-sea hydrothermal vent communities

At the nearly pristine hydrothermal vents of the deep sea, highly endemic animals depend upon bacteria nourished by hydrothermal fluids that emerge as outflows from the seafloor. These animals are remarkable in tolerating extreme conditions, including high heat, toxic reduced sulfide, and low oxygen. Here, we test whether the extreme vent environment has selected for functionally similar species across the world's deep ocean, despite well-established global geographic patterns of high phylogenetic distinctness. High functional redundancy in species pools within regions suggests that the extreme environments select for species with specific traits. Yet, some regions emerge as functional hotspots where species pools with distinct functional trait compositions may represent geological idiosyncrasies of the habitats. Moreover, many species are functionally unique, an outcome of low species richness in a system where the species pool is small at all scales. Given the high proportion of functionally unique species, simulated species extinctions indicate that species losses would rapidly translate to the elimination of functionally irreplaceable species and could tip vent systems to functional collapse. Ocean changes and human-induced threats are expected to significantly impact many vent species as human activities expand in the remote deep sea. The opportunity exists now to take precautionary actions to limit the rates of extinction now ubiquitous in more accessible areas of Earth.

Small Streams Support Beta Diversity in Neotropical Fish Assemblages in the Upper Paraná River Basin

ABSTRACTVariation in species composition along an environmental gradient (β‐diversity) can inform our understanding of biodiversity patterns and species composition. Beta diversity can be partitioned into species contributions to beta diversity (SCBD) and local contributions to beta diversity (LCBD). While SCBD describes the variations in species composition among samples, LCBD measures the uniqueness of a biological community within a larger ecosystem. Recently developed metrics enabled the estimation of species contribution to total beta diversity (SCBD) and the contribution of individual sites to total beta diversity (LCBD). Utilising these metrics, a one‐time survey of 275 sampling points within four sub‐basins of the Upper Paraná River Hydrographic Basin (low‐flow streams, < 5 m3/s) was conducted to assess fish community composition. Our results show that limnological influences at different scales contribute to higher LCBD. However, land use and species richness were not directly linked to this outcome, suggesting that sites with fewer fish species along sub‐basins contributed to higher beta diversity. It was concluded that beta diversity is more influenced by limnological characteristics and the position of sampling sites along the longitudinal gradient than that based on variations in species composition (SCBD). Moreover, high LCBD values were even found in portions of the gradient with lower species richness. This means that small streams in the sub‐basins of the upper Paraná River are unique and are comprised of varied habitats that contribute to increasing diversity. As such, they should be seen as a target in the development of environmental policies designed to conserve their pristine condition.

Evaluating Environmental Programs: Long-Term Monitoring of Crustacean Assemblages in a Polluted Estuary

We assessed the environmental quality of the Odiel-Tinto estuary, one of the most polluted in the world, by analysing the spatial variation of subtidal soft-bottom crustacean assemblages from 2000 to 2016. Our primary goal was to evaluate whether corrective measures implemented since 1986 have resulted in significant ecological improvement. The assemblages were structured according to the natural gradient from the estuary to the marine environment. Throughout the study, the assemblages exhibited low species richness and abundance (e.g., over 3 species and 180 individuals/m2 in the inner areas; 19 species and 510 individuals/m2 in the mouth zone). However, 2016 saw an increase in both species number and total abundance (e.g., over 5 and 24 species in the inner and mouth areas, respectively). Despite these observations, the Odiel-Tinto system harboured fewer species (24 species) compared to nearby estuaries like the Guadiana and Guadalquivir (over 50 species). Although there were signs of changes in the estuary over the sampling periods (e.g., a slight increase in richness and diversity in 2016 compared to 2002 and 2004), these fluctuations are likely characteristic of a highly dynamic environment rather than indications of genuine ecological recovery. These findings highlight the need for a long-term monitoring program, which should also encompass intertidal mudflats due to their higher density and biomass, easy accessibility, and reduced exposure to the impacts of recurrent maintenance dredging of the navigation channel.

Interannual differences vs small-scale spatiotemporal variability of spring zooplankton in the Crimean marine hypersaline lake

Ecosystems in the shallow marine hypersaline environment, such as marine lakes, are among the most changeable and have significantly lower species richness than freshwater and marine. It could be assumed that the intricate interconnections in hypersaline water ecosystems are easier to understand than in other aquatic ecosystems. Interannual differences vs small-scale spatiotemporal variabilities were studied in the spring zooplankton of hypersaline Lake Moynaki from 2019 to 2023. Salinity, water temperature, wind speed and direction were measured along with zooplankton sampling. The average spring wind speed and water temperature varied significantly from year to year, seemingly with a certain cyclicity. In total, 17 species were noted in zooplankton. The copepods Acanthocyclops vernalis and Arctodiaptomus salinus were not previously recorded in the lake. Bottom species were found in the plankton, among which the oligochaete Nais pseudobtusa, the gastropod Bittium reticulatum, and dragonfly larvae Gomphus sp. had not previously been found in the lake. Only four species, Gammarus aequicauda, Eucypris mareotica, Moina salina, and Cletocamptus retrogressus were regularly observed en masse. On average, the total zooplankton abundance near the windward shore was 2 times higher than that near the leeward shore and the abundance of individual species was from 2 to 5 times higher. If the values near only one coast were used, then the range of interannual differences would be underestimated or overestimated by approximately 2–4 times. Based on the zooplankton similarity in different years, all years except 2019, are grouped into a single cluster. Various changes are occurring in the lake, which are difficult to present as a complete picture of the cause-and-effect relationships that determine them.

Elevational and Seasonal Patterns of Plant-Hummingbird Interactions in a High Tropical Mountain.

Tropical mountain ecosystems harbor diverse biological communities, making them valuable models for exploring the factors that shape ecological interactions along environmental gradients. We investigated the spatial and temporal drivers of plant-hummingbird interaction networks across three forest types (pine-oak, fir, and subalpine) along a tropical high mountain gradient in western Mexico (2400 to 3700 m.a.s.l.). We measured species abundance, diversity, morphology, and interaction frequencies. Plant diversity metrics significantly declined in the highest elevation subalpine forest, whereas hummingbird diversity remained consistent across elevations. Interaction networks were similarly nested across elevations, but they were more specialized in the subalpine forest, where lower plant species richness and higher floral abundance led to greater resource partitioning among hummingbirds. Plant-hummingbird networks were larger and less specialized during the dry season, driven by greater species diversity and abundance. Species turnover explained network variation along the elevational gradient, while interaction rewiring and the arrival of migratory hummingbirds explained changes between seasons. Phenological overlap was the most important driver of the observed variation in interaction frequencies across elevations and seasons. Flower abundance had a minor influence on interaction frequencies at low- and mid-elevation networks, and hummingbird abundance was significant for dry- and rainy-season networks. Morphological matching was significant in the low-elevation forest and in the dry season. Plant phylogenetic relatedness had negligible effects on interaction patterns, but hummingbird phylogeny influenced feeding preferences in high-elevation and rainy-season networks. Our findings highlight the role of species turnover, interaction rewiring, and phenological overlap in structuring plant-hummingbird networks, with specific effects of abundance, morphology, and phylogeny varying with elevation and season. High-elevation ecosystems play a crucial role as reservoirs of floral resources for both resident and migratory hummingbirds during resource-scarce periods, emphasizing their importance in maintaining biodiversity in tropical mountain gradients.

Edinburgh postpartum depression scores are associated with vaginal and gut microbiota in pregnancy

BackgroundPrenatal and postpartum depression may be influenced by the composition of host associated microbiomes. As such, the objective of this study was to elucidate the relationship between the human gut or vaginal microbiomes in pregnancy with prenatal or postpartum depression. Methods140 female participants were recruited at their first prenatal visit and completed the Edinburgh Postnatal Depression Scale (EPDS) to screen for depression and anxiety, in addition the EPDS was completed one month postpartum. Vaginal and stool biospecimens were collected in the third trimester, analyzed using 16S rRNA gene sequencing, and assessed for alpha and beta diversity. Individual taxa differences and clustering using the k-medoids algorithm enabled community state type classification. ResultsParticipants with higher postpartum EPDS scores had higher species richness and lower abundance of L. crispatus in the vaginal microbiota compared to those with lower EPDS scores. Participants with a higher prenatal EPDS score had lower species richness of the gut microbiome. Participants with a vaginal community state type dominated by L. iners had the highest mean prenatal EPDS scores, whereas postpartum EPDS scores were similar regardless of prenatal vaginal state type. LimitationsOur small sample size and participant's self-report bias limits generalizability of results. ConclusionsDepression in the prenatal and postpartum period is associated with the composition and diversity of the gut and vaginal microbiomes in the third trimester of pregnancy. These results provide a foundational understanding of the microbial relationships between maternal health and depression for identifying potential therapeutic treatments.

Isolation limits spring pollination in a UK fragmented landscape

Animal-mediated pollination determines the reproductive success of most flowering plants; this process however can be disrupted by environmental degradation, with habitat loss and fragmentation highlighted as a top driver of pollination deficits. Despite being a pervasive stressor worldwide, we still have rather limited empirical evidence on its effects on pollination services, especially for early spring pollination syndromes. We investigate this using a potted plant phytometry experiment in which we placed English Bluebell (Hyacinthoides non-scripta)—a species largely pollinated in spring—into a fragmented woodland habitat. We selected 51 woodland patches which varied in both size and distance from each other and placed 153 pots of bluebell plants in the patches for c.4 weeks to measure pollination. The woodlands were located in a matrix of grassland, the latter being of low plant species richness and overall in the patches, woodland plants showed a positive species-area relationship. We collected traits on bluebell reproduction, these included the number, size, quality of seeds, the number of seed capsules and the number of flowers that failed to set any seeds. We found that seed traits responded differently to patch area and isolation. Patch isolation negatively affected the number of seeds and capsules, whilst it did not affect the size and quality of seeds. Patch area had no effect on any traits, suggesting that patch area might not necessarily be a factor that affects pollination in this species. The number of flowers that failed to set seed was unaffected by either patch area or isolation. Our study suggests that woodland fragmentation impacts the pollination of understory spring flowering plants. Our results highlight the use of multiple traits of phytometer plants to evaluate pollination and the importance of connectivity in maintaining pollination services in small-fragmented landscapes.

Mangrove forest ecological function is influenced by the environmental settings and the benthic fauna composition

Benthic communities perform many important roles within mangrove ecosystems and are responsible for facilitating many of the functions attributed to mangrove forests. For instance, they are instrumental in mediating mangrove system productivity, and provide crucial food for juvenile nekton. Despite their importance, very few studies have investigated the benthic community of mangrove forests, and among those the results are inconsistent. This variability manifests in strong location effects, with low organism density and species richness in Indo-Pacific mangroves, compared to West Atlantic sites. These regional difference are confounded by differences in within-region environmental settings (e.g. rainfall, tidal range, spatial location along the coastal mosaic), and this complicates the development of a clear understanding of underlying consistencies. To assess the influence of contrasting environmental influences on the benthic community of mangrove forests we studied the benthic community of Rhizophora stylosa forests at two coastal estuaries and along the shores of two islands within a 75 km radius. The results showed that the community composition differed among settings, with several taxa only occurring at one of the two forests type. Furthermore, Peracarida, a common prey found in the gut of juvenile fish, was only found through the island forests, but never observed within the estuarine forests. This indicates that environmental setting can play a key role in determining the nature of mangrove benthic assemblages and their potential ecological roles. Consequently, caution is required when attributing the ecological roles of mangrove forests without accounting for changes in settings. Additionally, we only investigated a single mangrove species within the same climatic region, meaning that even greater variability is likely when the full range of mangrove types, conditions and areas are assessed. Understanding this variation is important because it implies that mangrove forest restoration projects are unlikely to achieve their desired outcomes unless setting-specific conditions are understood and taken into account.

Investigating the Effect of Bacilli and Lactic Acid Bacteria on Water Quality, Growth, Survival, Immune Response, and Intestinal Microbiota of Cultured Litopenaeus vannamei.

Shrimp is one of the most important aquaculture industries. Therefore, we determined the effect of nitrifying-probiotic bacteria on water quality, growth, survival, immune response, and intestinal microbiota of Litopenaeus vannamei cultured without water exchange. In vitro, only Bacillus licheniformis used total ammonia nitrogen (TAN), nitrites, and nitrates since nitrogen bubbles were produced. TAN decreased significantly in the treatments with B. licheniformis and Pediococcus pentosaceus and Leuconostoc mesenteroides, but no differences were observed in nitrites. Nitrates were significantly higher in the treatments with bacteria. The final weight was higher only with bacilli and bacilli and LAB treatments. The survival of shrimp in the bacterial treatments increased significantly, and superoxide anion increased significantly only in lactic acid bacteria (LAB) treatment. The activity of phenoloxidase decreased significantly in the treatments with bacteria compared to the control. Shrimp treated with bacilli in the water showed lower species richness. The gut bacterial community after treatments was significantly different from that of the control. Linoleic acid metabolism was positively correlated with final weight and superoxide anion, whereas quorum sensing was correlated with survival. Thus, bacilli and LAB in the water of hyperintensive culture systems act as heterotrophic nitrifers, modulate the intestinal microbiota and immune response, and improve the growth and survival of shrimp. This is the first report on P. pentosaceus and L. mesenteroides identified as nitrifying bacteria.

Rock outcrops as interglacial refugia for plants: Ecological evidence from the forest‐steppe transition of Patagonia

AbstractIn the forest‐steppe transition of Patagonia from Argentina, the intense physical variability promotes the occurrence of contrasting vegetation units, among which is the saxicolous meadow developed on rock outcrops. In temperate and tropical regions, these geoforms of highly variable climate and topography, and poor soil development play an ecological and evolutionary role disproportionate to their reduced area. In Aguas Frías (38°46′S, 70°54′W), the range, diversity, density and adaptation of vascular plant species growing in the saxicolous meadow were compared to those of the surrounding steppe, forest and hygrophilous meadow. We hypothesize that rock outcrops exhibit a compositionally and functionally divergent, cold‐adapted flora of a previously more widespread distribution, allowing them to be categorized as refugia for species whose range retreated during the current interglacial. In comparison to the other units, the saxicolous meadow exhibited a small area, low plant cover, high total, native and rare species richness, high density and diversity of species, high richness of unique families and species and an exclusive presence of (rock) ferns. It also presented a high richness of endemic species with more extreme latitudinal and altitudinal distribution, particularly >46° S and >3000 m a.s.l. The similarity of species between the saxicolous meadow and the other units was low. Chamaephytes and nanophanerophytes were dominants, hemicryptophytes and geophytes were infrequent and mesophanerophytes and therophytes were absent. Equivalent results in terms of area of rock outcrops, and origin, strategy, composition, diversity and range of species were found in different regions. The biological and physical attributes would allow these outcrops to be characterized as reduced habitats of high diversity which could be acting as refugia for cold‐adapted plants. Conservation actions must prevent and mitigate the effects of fire, biological invasion and cattle grazing that represent the current threats to this ecosystem.