Invertebrate Species Richness Research Articles

Macrozoobenthos of Communities of Higher Aquatic Vegetation

The article presents the results of a comprehensive study of two components of the aquatic biocenosis: its floristic component and benthos in the shallow waters of the Gorky reservoir within the water area of the Yaroslavsky nature reserve. The composition and structure of plant communities at the boundary of the macrophyte belt was assessed, followed by the identification of dominant associations. In parallel, the taxonomic composition and quantitative characteristics of macrozoobenthos were assessed in the main plant biotopes. Plant communities in the water area are represented by two ecological groups: helophytes and hydrophytes. Macrophytes occupy up to 25% of the water area of the shallow area of the studied water body. Most of the plant communities are concentrated in the northern and northeastern parts of the reserve. 11 species of macrophytes belonging to 10 genera and 9 families were noted. In macrophyte communities, 8 typical associations were identified, where benthos sampling was carried out. In the benthos of typical macrophyte associations, 35 lower definable taxa (LTOs) were identified, of which 17 LUTs are chironomid larvae. In the biotope, 11 HOTs were found out of vegetation. The highest species richness of benthic invertebrates was noted in the communities of Butomus umbellatus L. (1753) and Sparganium erectum L. The benthos of plant communities in August 2021 can be characterized as chironomid-oligochaete, while chironomids dominated in the open littoral. Mollusks played a significant role in the formation of benthos in plant communities. The maximum quantitative indicators of benthic invertebrates in general and the abundance of chironomids of the river. Glyptotendipes in particular have been noted in the community of the burr Sparganium erectum. This is probably due to the morphological structure of this plant and the specifics of the formation of the community by this species. The benthos of plant communities was dominated by phytodetritophages–filterers and phytodetritophages–filterers + gatherers, while in the open littoral, phytodetritophages–filterers prevailed. In all studied biotopes, there were no detritophages–gatherers. In general, according to the abundance of macrozoobenthos, the areas of plant communities can be classified as high-nutrient and very high-nutrient.

Association of Aquatic Invertebrates with the Water Quality in the Ponds of Bhaktapur

Aquatic invertebrates are representative of the health of habitats they live in. This study was conducted to evaluate aquatic invertebrate diversity and relate them with physico-chemical factors in the ponds of Bhaktapur. Rani pokhari, Bhajya pokhari, Na pokhari and Kamal pokhari were selected for the study. Plankton net was swiped out for approximately one minute in each corner of all the ponds. Five subsequent sweeps were taken repeatedly at each site. Invertebrates collected in the net were kept in a plastic container covered with a lid. The collected species were preserved in 70% alcohol. For physico-chemical analysis, water samples were collected from 10cm below the surface water in BOD bottles from each site and taken to the laboratory of Department of Zoology, Bhaktapur Multiple Campus for the further identification and laboratory work. Total 16 species of aquatic invertebrates belonging to five phyla, 10 orders and 16 families were recorded from the ponds of Bhaktapur. Species richness of aquatic invertebrates was found to be 13, 11, four and five in Rani pokhari, Bhajya pokhari, Na pokhari and Kamal pokhari respectively. Phylum Arthropoda was most abundant in all four ponds. The correlation of species richness with physico-chemical parameters showed a positive correlation with water temperature (r = 0.96), electric conductivity (r = 0.98), free carbon dioxide (r = 0.99) and dissolved oxygen (r = 0.51) while the negative correlation with pH (r = -0.83) and alkalinity (r = -0.83). The result obtained is valuable and useful for continuous water quality monitoring activities and the conservation of freshwater fauna in the ponds of Bhaktapur. Further detailed studies on aquatic invertebrates were highly recommended.

Influence of isolation on the resilience of tank bromeliad ecosystems to drought in a Neotropical rainforest

AbstractLittle is known of how Neotropical freshwater ecosystems will respond to future climate scenarios. In Neotropical rainforests, a substantial fraction of the freshwater available to the aquatic fauna is found within phytotelmata, plant-held waters that form aquatic islands in a terrestrial matrix. We hypothesized that phytotelmata in close proximity have higher resilience capacity to severe drought than the isolated ones, under the assumption that immigration from nearby sources promotes faster recovery. We used rainshelters to emulate an extreme drought (67 days without rainfall) in tank-forming bromeliads arranged in patches of 1, 3 or 6 plants in a primary forest of French Guiana. Habitat size was a stronger determinant of invertebrate species richness and biomass per bromeliad than patch size. Larger bromeliad patches attenuated the adverse effect of drought on the biomass of predators, probably because short-range migration within dense patches allowed individuals to find moist refuges. However, the recovery of aquatic communities and ecosystem functions was mostly supported by in situ resistance, and a rescue effect of immigration was weak. Whilst environmental management plans tend to focus on dense networks of connected water bodies, our study shows that efforts should not omit the isolated ones.

Gut Bacterial Communities in the Ground Beetle Carabus convexus.

Biological interactions, including symbiotic ones, have vital roles in ecological and evolutionary processes. Microbial symbionts in the intestinal tracts, known as the gut microbiome, are especially important because they can fundamentally influence the life history, fitness, and competitiveness of their hosts. Studies on the gut-resident microorganisms of wild animals focus mainly on vertebrates, and studies on species-rich invertebrate taxa, such as ground beetles, are sparse. In fact, even among the species-rich genus Carabus, only the gut microbiome of two Asian species was studied, while results on European species are completely missing. Here, we investigated the gut bacterial microbiome of a widespread European Carabus species, targeting the V3 and V4 regions of the 16S ribosomal RNA genes by next-generation high-throughput sequencing. We identified 1138 different operational taxonomic units assigned to 21 bacterial phyla, 90 families, and 197 genera. Members of the carbohydrate-degrading Prevotellaceae family, previously not detected in ground beetles, were the most abundant in the gut microbiome of the carnivorous C. convexus. Presumably, individuals from the studied wild populations also consume plant materials, especially fruits, and these carbohydrate-degrading bacterial symbionts can facilitate both the consumption and the digestion of these supplementary foods.

Linking hydrological connectivity with the richness and composition of aquatic invertebrates across the Paraná River floodplain, Argentina

Lateral hydrological connectivity can affect the community characteristics by promoting dispersal of organisms between the river and its floodplain. We investigated the species richness, specific diversity, and relative abundance of microcrustaceans transported by the flood and the macroinvertebrates retained by Pontederia crassipes Mart. roots in five floodplain lakes with different connectivity within the RAMSAR Site Humedales Chaco. Due to differences in the slopes of the floodplain studied, the connectivity was determined by the topographic location of each lake, rather than by the distance from the river. During the hydrological connection, there was a transverse gradient in the physical and chemical characteristics of the water, with an increase in the electrical conductivity and a decrease in dissolved oxygen and suspended solids in the more isolated sites. A total of 62 species of microcrustaceans (48 cladocerans and 14 copepods) and 63 taxa of macroinvertebrates were identified. The microcrustaceans had high species richness in the three most connected lakes, whereas the macroinvertebrates had a peak in taxa richness in the lakes with intermediate connectivity. The low beta diversity (βw) for both microcrustaceans (14.63 %) and macroinvertebrates (16.9 %) indicated that taxa richness varied little between sites with different hydrological connectivity. In both assemblages, cluster analysis based on the similarity of the relative abundance grouped the three sites more connected and separated from the less connected sites. Our results suggest that species richness followed different patterns in different assemblages across the lateral gradient and that the hydrological connectivity was more related to the relative abundance of microcrustaceans and macroinvertebrates than to the classical measures of βw. Species diversity indices did not vary between sites. The high total species richness of invertebrates is mainly a result of the spatial arrangement of the different floodplain lakes.

Aquatic invertebrates and their correlation with the basic abiotic factors in the coastal water of Can Gio, Southern Vietnam

Macroinvertebrates metrics are reliable indicators to assess the environmental quality and ecological health. In water systems, estuarine areas are sinks and sources of nutrients and pollutants, and strongly influenced by anthropogenic activities and emission from inland. Benthic macroinvertebrates and zooplankton living in estuary and coastal are not very active organisms hence heavily impacted by surrounding environmental conditions. In this study, we assessed the water quality at the tropical coastal of Can Gio located in Southern Vietnam, based on the aquatic invertebrates and environmental variables. The organisms were monitored at 20 sampling sites along the Can Gio coastal in November 2021, April, June and August 2022. Totally, 45 invertebrate species were recorded in the Can Gio coastal. The zooplankton and benthic macroinvertebrate abundance, respectively, varied between 900 to 13,000 individuals/m3, and ranged from 30 to 120 individuals/m2. The copepods and polychaetes were dominant in both species number and abundance of the zooplankton and benthic macroinvertebrates, respectively. The water quality at the Can Gio coastal during the monitored period was from low pollution to high-moderate pollution based on the invertebrate structure, abundance and indices. The results also showed the correlation between environmental variables (e.g., turbidity and dissolved oxygen) and species richness and abundance of aquatic invertebrates. Our study revealed the important and valuable application of aquatic invertebrates for the environmental quality monitoring to protect the border of the most mangrove biosphere reserve in Vietnam.

Do different camera trap lures result in different detection rates of vertebrates because of their attractiveness to invertebrates?

SummaryThe type of attractant used in camera trap lures is recognised as an important methodological decision. We investigated whether the type of attractant in lures indirectly influences detectability of wildlife on cameras via differential attraction of invertebrates which themselves constitute prey of insectivorous animals. We indexed invertebrate abundance using pitfall and sticky‐traps at 36 camera stations deployed in a Latin Squares design for 5 days, with three lure options (peanut‐butter, tuna oil and control) in a coastal mosaic, at Cape Otway, Victoria, Australia. We classified vegetation types (habitat) as: low (no or sparse), medium (grass), and high (shrubs) from aerial imagery and estimated their percentage cover at each grid point (medium and high were uncorrelated and included as separate variables in models). We first examine if attractant types or the habitat influence invertebrate abundance and assemblage, and then examine whether invertebrate abundance influences vertebrate detectability on cameras. There was a trend for the composition of terrestrial invertebrate assemblages to be influenced by lure type (peanut‐butter, tuna oil and control attractants) and the proportional cover of medium height vegetation within 20 m; however, assemblage composition was clearly influenced by the proportional area of high vegetation cover within 20 m. The detection probability of insectivorous birds increased where medium‐sized (2.5–5 mm) flying invertebrates were present whereas insectivorous mammal detectability increased with terrestrial invertebrate species richness. Mammal detections are more likely associated with use of habitats that have more diverse invertebrate communities. This study provides some support to the hypothesis of the indirect mechanism whereby bird detections are influenced by invertebrate attraction to lures. Therefore, lure choice for camera traps is critical and the possibility of guild‐level biases in detection suggests that cautious interpretation of results is required.

Crop cover and nutrient levels mediate the effects of land management type on aquatic invertebrate richness in prairie potholes.

Aquatic invertebrates provide important ecosystem services, including decomposition and nutrient cycling, and provide nutrition for birds, fish, amphibians, and bats. Thus, the effects of agricultural land management practices on aquatic invertebrates are relevant to farmers, wildlife biologists, and policymakers. Here, we used data on aquatic invertebrates (159 taxa, 73 to species, 75 to genus/family) collected in 40 wetlands in the Canadian prairies to test for direct and indirect relationships among land management types (perennial cover, organic, minimum tillage, conventional), landscape structure (cropland and wetland cover within the surrounding landscape), and water quality (total nutrient levels, turbidity) on species richness of invertebrates using structural equation modelling. Additionally, we assessed variation in community composition within and among wetlands in different land use management types using a direct gradient analysis and variance partitioning. The direct effects of land management type were not supported but we found strong supportive evidence that effects of land management on richness were significantly mediated through cropland cover, nutrient levels, and turbidity. After controlling for these indirect effects, aquatic invertebrate richness decreased along a gradient from the lowest to the highest farming intensity, i.e., richness decreased from perennial cover sites to organic to minimum tillage to conventional sites. Support was also found for negative effects of nutrient levels and turbidity on richness. We did not find significant support for differences in gamma diversity or a simple test (homogeneity of multivariate dispersions) of differences in turnover among land management types; however, land management had a significant effect in distance-based redundancy analysis. Taken together, these results suggest that focusing conservation efforts on reducing cropland erosion and nutrient inputs to wetlands and creating more permanent cover may be effective strategies for conserving richness of aquatic invertebrates in agricultural landscapes in this region.

Impact of Cropland Management on Invertebrate Richness and Abundance in Agroforestry Systems in Bali, Indonesia

The intensive management of cropland refers to a reduction in habitat complexity (i.e., shade tree cover, tree species richness, crop species richness) to gain more profits. This usually entails a decrease in biodiversity, but agroforestry systems have been shown to provide a solution to the need for profits while maintaining biodiversity and ecosystem services. Invertebrates are important bioindicators since they are not just affected by a decrease in habitat complexity; they are also key for the maintenance of ecosystems given their ecological roles. We aimed to understand how agricultural intensification impacted invertebrate abundance and richness in an agroforestry system in Bali, Indonesia. We set up 53 × 25 m2 plots and collected data via pitfall and pan traps. We linked those data to vegetation data (canopy cover, tree species richness, crop species richness), habitat type (rustic vs. polyculture), and productivity. Overall, we found that the abundance and richness of invertebrate taxa were positively influenced by increasing canopy cover and crop and tree species richness. This supports the habitat heterogeneity hypothesis, which indicates that increased habitat complexity promotes higher invertebrate species richness and abundance. The abundance and richness of certain invertebrate taxa, including agents of biocontrol, were shown to increase in plots with higher yields, thus solidifying the important role of invertebrate communities in the provision of ecosystem services. Harvesting crops from complex agroforestry systems ensures a sustainable income for local communities as well as habitats for invertebrates.

Regional impacts of warming on biodiversity and biomass in high latitude stream ecosystems across the Northern Hemisphere

Warming can have profound impacts on ecological communities. However, explorations of how differences in biogeography and productivity might reshape the effect of warming have been limited to theoretical or proxy-based approaches: for instance, studies of latitudinal temperature gradients are often conflated with other drivers (e.g., species richness). Here, we overcome these limitations by using local geothermal temperature gradients across multiple high-latitude stream ecosystems. Each suite of streams (6-11 warmed by 1-15°C above ambient) is set within one of five regions (37 streams total); because the heating comes from the bedrock and is not confounded by changes in chemistry, we can isolate the effect of temperature. We found a negative overall relationship between diatom and invertebrate species richness and temperature, but the strength of the relationship varied regionally, declining more strongly in regions with low terrestrial productivity. Total invertebrate biomass increased with temperature in all regions. The latter pattern combined with the former suggests that the increased biomass of tolerant species might compensate for the loss of sensitive species. Our results show that the impact of warming can be dependent on regional conditions, demonstrating that local variation should be included in future climate projections rather than simply assuming universal relationships.

Water-filled leaf axils in teasel plants: A study of often overlooked aquatic habitats

Teasels (Dipsacus spp.) are among the few European plant species that can create small aquatic ecosystems, known as phytotelmata, in their leaf axils. However, these unique environments have received little research attention. We performed the first detailed study of phytotelmata in teasels, aiming to describe the physical habitat and macroinvertebrate communities across different leaf axil levels. We explored 64 phytotelmata on 20 teasel plants in Slovakia (Central Europe). These small aquatic ecosystems contained less than 100 ml of water, exhibited a pH ranging from slightly acidic to neutral, had very low oxygen content, and showed highly variable conductivity. We collected more than 1000 larvae of Diptera, representing at least ten aquatic invertebrate taxa. The dominant species found in these communities were the chironomid Metriocnemus eurynotus (Holmgren, 1883), followed by ceratopogonids of the genus Dasyhelea. The oldest, bottom-situated phytotelmata showed the highest invertebrate density and species richness, suggesting an important role of ecosystem age and the probability of colonization in the community assembly process. These highly replicated ecosystems with simple communities may serve as useful models for studying various ecological phenomena such as metacommunity dynamics, succession, community assembly, biodiversity-ecosystem functioning or mutualistic interactions.

Two new species of Hyalella (Amphipoda, Dogielinotidae) from the Humid Chaco ecoregion of Paraguay.

The freshwater amphipod genus Hyalella Smith, 1874 is widely distributed in the Neotropics, with several biogeographically restricted species and a high cryptic diversity throughout South America. Tens of species of Hyalella have been documented from nearby Brazil and Argentina, but no systematic record of the genus exists for Paraguay. Here we describe two new species of Hyalella: H.mboituisp. nov. and H.juliasp. nov. from the Ñeembucú wetlands of southwestern Paraguay. Hyalellamboituisp. nov. and H.juliasp. nov. are characterised by a dorsally smooth body, pigmented eyes, uropod 1 endopod with a curved seta, the dorsal margin of uropod 3 ramus without setae, and uropod 3 peduncle longer than wide and with six setae apically. The two species are distinguished by their diagnostic mouthparts, with a median serrated edge on the lacinia mobilis in H.mboituisp. nov. and two elongated lateral denticles with a serrated edge in H.juliasp. nov., and by the presence of a pronounced cup for the dactylus on gnathopod 2 in H.mboituisp. nov. In addition, they show differences in the number of articles on antennae 1 and 2, in the relative length of the pereiopods, and in the numbers and types of setae on their gnathopods and uropods 1-3. Hyalellamboituisp. nov. and H.juliasp. nov. represent the first taxonomically documented occurrence of Paraguayan freshwater amphipods. These new taxa attest to the largely unmapped species richness of freshwater invertebrates in the Humid Chaco of Paraguay. This potential biodiversity hotspot is currently under threat from land conversion, highlighting the need for more systematic studies and effective conservation of the local invertebrate biodiversity.

Invasion of farmland hedgerows by non-native small mammals is associated with lower soil surface invertebrate diversity, abundance, body size and biomass

Small mammals in farmland hedgerows feed on soil surface invertebrates with non-native invasive species potentially affecting prey species and populations. We investigated terrestrial invertebrates using pitfall traps and leaf litter samples across four zones of invasion in Ireland: (1) native species only (wood mouse Apodemus sylvaticus and pygmy shrew Sorex minutus), (2) natives plus the non-native bank vole (Myodes glareolus), (3) natives plus the non-native greater white-toothed shrew (Crocidura russula) and (4) natives plus both. After accounting for regional and local environmental variation, small mammal invasion was associated with lower invertebrate species richness (9–39% lower than uninvaded zones), reduced abundance (18–56% lower), shorter arthropod body length (24–52% shorter) and lower arthropod biomass (63–89% lower). Negative effects were observed on a wide range of disparate functional groups spanning phytophagous, detritivorus, zoophagous and omnivorous taxa including: the Staphylinidae, Carabidae and Coleoptera larvae, Isopoda, Diplopoda, Diptera, Hymenoptera, Pulmonata and Acari. The greater white-toothed shrew had greater negative effects than the bank vole with presence of both having greater effects than either alone though the majority of their combined effects were largely attributable to the former. The bank vole may mitigate some of the negative effects of the greater white-toothed shrew on invertebrate abundance perhaps indicating of some form of trophic interaction. Predation of detritivores and large invertebrate predators may impact farmland ecosystem service delivery i.e. nutrient cycling and pest biocontrol. Hedgerow biodiversity loss may induce indirect trophic cascades negatively impacting other taxa including farmland birds.

Anthropogenic land uses influence stream dissolved organic matter quality more than decomposition rates and macroinvertebrate diversity

In the era of the Anthropocene, streams and rivers are among the most heavily impacted ecosystems due to the influence of catchment land use on stream water quality and ecological condition. In practice, structural and functional indicators collected by biomonitoring programs are underused and thus limited in their ability to offer practical insight into functional-based restoration approaches. Here we applied a novel combination of indicators—cotton strip decomposition, benthic invertebrate sampling together with dissolved organic matter (DOM) composition — to determine if streams highly impacted by urbanized and agricultural land use across Windsor-Essex (southwestern Ontario, Canada) were consistent across season, anthropogenic land use or some combination of both. Overall, our results suggest that urbanized and agricultural streams are indeed degraded at a similar level, with high decomposition rates and low levels of macroinvertebrate diversity. Moreover, DOM quality proved to be the most predictable indicator spatially and seasonally, integrating insights from both decomposition and macroinvertebrate indices. Microbial humic-like DOM correlated positively with decomposition rates, and negatively with invertebrate species richness. Our findings show that functional changes in stream ecological condition can be effectively tracked by structural indicators, namely DOM composition. DOM offers a cost-effective approach to assessing ecosystem health and should be explored as a reliable indicator in monitoring programs and to inform functional-based indicators in ecosystem restoration.

Effect of nature protection and management of grassland on biodiversity – Case from big flooded river valley (NE Poland)

Agriculturally used meadows are habitats whose biodiversity depends on anthropogenic disturbances such as fertilization or mowing. Intensified agricultural practices (too frequent mowing, use of mineral fertilizers and insecticides) lead to declines in the abundance and species diversity of the biota inhabiting them. The intensification of agricultural production in north-eastern Poland relates primarily to the increase in cattle numbers and the intensification of grassland management, but many areas were included in Natura 2000 network. Our study was aimed at indicating the impact of diverse use of meadows on the species richness and diversity of invertebrates, amphibians, and birds in the grasslands of Narew river valley, Special Bird Protection Area, where the intensification of grassland use was noted in the last decades, and part of the meadows was included in the agri-environmental program. The agri-environmental program is a very good tool for the protection of grassland biotic diversity. The highest taxonomic richness and diversity of the studied animal groups were found in meadows included in these programs with extensive use, while the lowest was in the over- and intensively used meadows fertilized with mineral fertilizers and liquid manure. Only the meadows in the agri-environment program were inhabited by the fire-bellied toad and the tree frog - amphibians from Annex IV of the Habitats Directive. The number of breeding bird species globally threatened (IUCN Red List), listed in Annex I of the EU Birds Directive, and with negative population trend in Europe (SPEC1–3) was highest in meadows included in EU conservation programs. The main factors reducing biotic diversity in the grassland of flooded river valley were the high number of grassland mowing per season, intensive fertilization, especially with liquid manure, the great distance of meadows to the river, low soil humidity, and low share of shrubs and trees in the meadows border zone.

Landscape and Marine Environmental Factors Jointly Regulate the Intertidal Species Richness and Community Structure in the Islands of South Korea

Most studies on island biogeography have focused on the terrestrial taxa; however, there are few studies on the drivers of diversity and community structure of intertidal organisms on islands. We evaluated the effect of landscape and marine environmental factors on the species richness (SR), functional diversity (FD), and community structure (SES.MFD) of intertidal invertebrates among the overall, inhabited, and uninhabited islands. Using the data on the intertidal organisms from 78 islands in South Korea, we implemented variable selection and piecewise structural equation modeling to determine the causal relationships between the SR, FD, and SES.MFD with four landscapes (i.e., island area, coastline length, distance from the mainland, and structural connectivity) and three marine environment factors (i.e., mean annual sea surface temperature variation, wind speed, and evapotranspiration). The coastline length had a positive effect on the SR and SES.MFD in the overall islands including inhabited and uninhabited islands. The SR and FD were negatively affected by the variation in sea surface temperature. The relative importance of the landscape and marine environmental factors differed between the inhabited and uninhabited islands. That is, the inhabited islands were mainly affected by the coastline length, whereas uninhabited islands were regulated by marine environmental factors. Our results demonstrated that the biotic factors of the island intertidal ecosystems are controlled by the interactions between the biotic and various environmental factors. Moreover, the results emphasize that the water stress on the intertidal organisms due to climate change may lead to a loss of biodiversity and functional clustering.

Biogenic habitats as drivers of invertebrate benthic community variability in Tongoy Bay (SE Pacific coast): implications of macroalga harvesting

Habitat biogenic complexity is thought to exert a significant positive influence on benthic communities. We examined the link between the seasonal variability of macroinvertebrate community structure (species and trophic richness, diversity and biomass) and habitats with different macroalgal assemblages. We identified macroinvertebrates and algae from 336 samples spread over four types of habitat: sand, mud, sand-gravel and seagrass meadows. Considering the whole macroalgal and macroinvertebrate assemblage, we confirmed that macroinvertebrate community variability within and among habitats can be mainly (but not only) explained by a few macroalgal structuring species. The variability of macroinvertebrate communities between habitats and seasons depended on the changes in the relative contribution of the explanatory biostructuring species in the overall algal community. Biomass, trophic behaviour and species richness remained stable in habitats with conspicuous macroalgal communities in contrast with habitats devoid of macroalgae. However, invertebrate species richness and biomass remained stable only in habitats whose dominant species did not change between seasons and not in those where dominant structuring species shifted. The seasonal change in a key structuring macroalgal species (Condracanthus chamissoi), probably as a result of harvesting, led to a major reduction in invertebrate community biomass and richness both in the particular habitat and in those nearby at species level. These consequences are especially important for invertebrates linked by trophic relationships and targeted by fisheries.

Species Richness of Benthic Macrofauna on Rocky Outcrops in the Adriatic Sea by Using Species-Area Relationship (SAR) Tools

In the northern Adriatic Sea, rocky outcrops called “trezze” or “tegnúe” are known as biodiversity hotspots. A total of 45 rocky outcrops were studied by using non-destructive photographic sampling during SCUBA diving. Ten invertebrate phyla with 196 taxa were recorded, 86% of which were determined at species level. Among them, 65% of the taxa were sessile, primarily represented by the phyla Porifera and Chordata. The aims of the study were: to characterize the species richness and composition of epifaunal invertebrates living on rocky outcrops; to test the efficiency of using the outcrop area as a predictor of epifauna richness, using the Arrhenius Species-Area Relationship (SAR) model; and to compare the expected richness resulting from the SAR model with the richness observed from the analysis of random photo-squares. Our results show that the SAR model describes the relationship between epibenthic species richness and outcrop size well and may have important practical applications for biodiversity estimations and nature conservation implications. It provides a useful tool, also in terms of economy and speed, to estimate the species richness of the benthic epifauna of the numerous outcrops that remain unsurveyed, based on their size.

Differential abundance, composition and mesohabitat use by aquatic macroinvertebrate taxa in ponds with and without fish

Fish are known to pose strong effects on invertebrate abundance, species richness and assemblage structure. Littoral vegetation may play a crucial role as a refuge for invertebrates vulnerable to fish predation. We studied relative densities and taxonomic composition of water mites, aquatic beetles and bugs in large lake-like ponds with different fish status (fish-free and containing fish) and mesohabitats (emergent littoral vegetation and open water zone). The macroinvertebrate taxa differed in their responses to the fish presence and in mesohabitat preferences. The density and species richness of water mites were greater in fish-containing ponds, while no differences were found between littoral and open-water habitats. In contrast, beetles were far more numerous and species-rich in fish-free ponds and in littoral vegetation. Total densities of aquatic bugs were non-significantly higher in fish-containing ponds, and they preferred littoral areas, but species richness was independent of fish presence and mesohabitat. No statistical interactions between fish presence and the densities of individual macroinvertebrate groups in the littoral habitat were detected, indicating that their use of emergent littoral vegetation was not an antipredator response to fish. The assemblages of the three macroinvertebrate taxa exhibited nested structures of a different order, consistent with their species richness patterns. Our research stresses the importance of littoral vegetation for the distribution and abundance of aquatic insects; however, high fish presence may not affect or may even benefit ecologically important macroinvertebrate groups, such as water mites or bugs.

Temporal consistency of a facilitation cascade on shallow rocky reefs

Facilitation cascades are increasingly recognized as key drivers of biodiversity in a variety of habitats, yet their temporal variability remains poorly investigated. On shallow subtidal rocky reefs, positive interactions between the canopy-forming species, Halopithys incurva, and its epiphyte, Jania rubens, enhance the abundance and diversity of the associated mobile invertebrate assemblage. By means of a field experiment manipulating the presence of J. rubens on H. incurva plants, we investigated whether the effects of this facilitation cascade varied over time scales of months. Despite seasonal fluctuations in its biomass, J. rubens enhanced total invertebrate abundance and species richness by 64% and 45%, respectively, throughout the experiment. Our results suggest that the presence of J. rubens, likely by providing novel microhabitats and increasing resource availability, sustains invertebrate biodiversity of shallow macroalgal forests consistently between warm and cold periods. Understanding the temporal dynamics of facilitation cascades and their mechanisms can help inform management strategies targeting biodiversity conservation and restoration under current and future climates.