Composition Of Assemblages Research Articles

The Effects of Cattle Grazing on the Composition of Diatom Assemblages in the Peatland Pools of the Southeastern Alps (Italy, Adamello-Brenta Nature Park)

Mires are significant C-sinks and important habitats for biodiversity conservation. Particularly in the Alpine peatlands, grazing and trampling cause mires to degrade, causing changes in plant communities that increase bulk density, peat erosion, and nutrient excesses. We took sixteen samples of epipelic and epiphytic diatoms from mire pools subjected to varying degrees of grazing in the Adamello-Brenta Nature Park (Trento, Italy). We identified >100 diatom species (ca. 70% included in Red List threat categories). We used nMDS to identify groups of diatom species. Their statistical significance was checked with an ANOSIM and, to identify the species that contributed most to the difference between the two groups, a BEST-SIMPER procedure was carried out. The multivariate analyses allowed us to identify significant differences among the most and least grazed sites, and to select the species that contributed most to this distinction. We confirmed that some species were more frequent and abundant in the most grazed sites and behaved as opportunists in the presence of a greater nutrient input, to the detriment of rare and sensitive species, which were more numerous and abundant in the less grazed sites. We provided useful information on grazing effects, underlining the importance of managing and protecting habitats of unique environmental value.

Nereidid polychaetes (Annelida) inhabiting the inside of decaying fronds of the mangrove palm Nypa fruticans in a tropical estuary in Malaysia, with special reference to the life history of the dominant species, Namalycastis sp

ABSTRACT Since relatively dense assemblages of nereidid worms were discovered from a unique habitat within the decaying fronds of the mangrove palm Nypa fruticans, we conducted a one-year survey from September 2015 to September 2016 at six sites in Setiu Wetlands, Malaysia, to clarify the species composition of the nereidid assemblages and the life history of the dominant species. The majority of specimens collected from the plant body (507 out of a total 678 specimens) belonged to Namalycastis sp. with remaining specimens belonging to Namanereis sp. (n=168), Namalycastis rhodochorde (n=1), and Perinereis aibuhitensis (n=2). Specimens of P. aibuhitensis (n=2) and Dendronereis sp. (n=2) were also collected from sediments around the palm trees. The taxonomic accounts of two Namalycastis spp. and Perinereis aibuhitensis are provided here. The life history of the dominant species Namalycastis sp. is evaluated based on the population characteristics. This species is gonochoric, with the sex ratio close to 1:1. The ovigerous females were found throughout the year, with their body width (BW) ranging from 1.3 to 4.8 mm. The ovigerous rate (no. of ovigerous females/no. of worms larger than the minimum ovigerous female) was lowest in February and March 2016 (8–9%) and highest from July to November 2016 (23–29%), when the ovigerous females had the largest coelomic oocytes of 100–120µm in diameter. Probable epitokes with additional neuropodial sesquigomph spinigers occurred most abundantly in November 2015 (21% of adults), which was also the only month when a mature male with mature spermatozoa appeared. Few juveniles with BW of less than 1.3 mm occurred from February to July, whereas large adults with BW of more than 3.5 mm occurred from May to November. These results suggest semelparous reproduction with peak spawning in November, coinciding with low salinity during the north-east monsoon.

Changes in the composition of subfossil algae and invertebrate assemblages along the depth gradient in dimictic Lake Valdayskoye (Novgorod Area, Russia)

Changes in the composition of subfossil algae and invertebrate assemblages along the depth gradient in dimictic Lake Valdayskoye (Novgorod Area, Russia)

The structure of epiphytic and planktonic bacterial assemblages under two contrasting lake regimes

Abstract In contrast to the macrophyte‐dominated regime (MDR), the phytoplankton‐dominated regime (PDR) in shallow lakes is characterized by relatively high nutrient concentrations, excessive phytoplankton growth and turbid water column. Some floating‐leaved plants can grow under both regimes and aid in reducing nutrient concentrations in water bodies. Their epiphytic bacterial assemblages play an essential role in the health and adaptation of these plants; however, there is limited understanding of this plant‐bacteria interaction. Here, we used 16S rRNA gene‐based high‐throughput sequencing to compare the diversity, composition and co‐occurrence patterns of planktonic and epiphytic bacterial assemblages associated with the submerged roots and floating leaves of Trapa natans, growing under the PDR and MDR in Lake Taihu, China. Alpha diversity of PDR epiphytic bacterial assemblages was lower than in MDR. The opposite trend was observed for planktonic bacterial assemblages. We detected a strong compositional difference between epiphytic and planktonic bacterial assemblages. Bacterial assemblages found on root and leaf surfaces showed only minimal compositional overlap with those in the water column. The composition of epiphytic bacterial assemblages differed more between the two regimes than did planktonic bacterial assemblages. The PDR co‐occurrence network of bacterial assemblages was more complex than that of the MDR, with the PDR epiphytic habitats enriched more network keystone taxa. The proportion of positive edges was also greater in the PDR networks of epiphytic bacterial assemblages than in the epiphytic MDR networks, whereas it was lower in the planktonic bacterial network from the PDR than from the MDR. The comprehensive view of the diversity, composition and co‐occurrence patterns of epiphytic and planktonic bacterial assemblages of MDR and PDR in large shallow lakes provided by our results showed that the structure of epiphytic bacterial assemblages was mediated by both host and water properties, and the observed core taxa and network keystone species may play an important role in maintaining plant growth and adaptation to environmental change.

Spatial and temporal variation of marine megafauna off coastal beaches of south-eastern Queensland, Australia

Context Coastal beach environments provide habitats for marine megafauna, including turtles, rays, marine mammals and sharks. However, accessing these variable energy zones has been difficult for researchers by using traditional methods. Aims This study used drone-based aerial surveys to assess spatio-temporal variation of marine megafauna across south-eastern Queensland, Australia. Methods Drones were operated at five south-eastern Queensland beaches. Megafauna sightings and key variables including location, month and turbidity were analysed to assess variation across locations. Key results Overall, 3815 individual megafauna were detected from 3273 flights. There were significant differences in the composition of megafauna assemblages throughout the year and among beaches, with megafaunal sightings in >80% of flights conducted off North Stradbroke Island. Conclusions Strong temporal presence was found that is congruent with other studies examining seasonality. This supports the use of drones to provide ecological data for many hard-to-study megafauna species and help inform long-term sustainable management of coastal ecosystems. Implications Results indicated that environmental conditions can influence the probability of sighting marine megafauna during aerial surveys.

Forest restoration benefits common and rare wood-decomposing fungi with a delay

Decline in the amount of dead wood deteriorates habitats for saproxylic organisms globally. This could be compensated by restoration, but it is poorly understood how created dead wood corresponds to the habitat requirements of saproxylic species. Using a large-scale field experiment of 30 restoration sites across Finland, we studied the long-term (5–15 years) effects of dead wood creation on wood-decomposing fungi (polypores) in Norway spruce and Scots pine dominated forests. All studied conservation areas had been used for timber production prior to conservation. The average amount and diversity of woody debris was higher on the restoration treatments than on the non-restored controls. Altogether, 56 polypore species were recorded. Restoration treatments had 1.4 and 8 times more species and observations than controls. Eight red-listed polypore species were observed, six on the restored plots (four only from the created dead wood) and two on the controls. Species composition of polypore assemblages differed between the restoration and control treatments, as well as between the spruce- and pine-dominated forests. Following restoration, temporal changes in the polypore assemblages were clear but only partly related to dead wood creation. Unlike previous short-term studies, our results show that dead wood creation by felling and ring-barking trees benefits not only common but also indicator and red-listed polypore species; indeed, 15 years after restoration all red-listed species occurred on created dead wood. As some red-listed species occurred solely on naturally fallen trees five to ten years after restoration, created dead wood alone cannot substitute for natural dead wood.

Eutrophication is better indicated by functional traits than taxonomic composition of macroinvertebrate assemblages in floodplain lakes

Eutrophication is better indicated by functional traits than taxonomic composition of macroinvertebrate assemblages in floodplain lakes

Fine‐scale variation in the medium and large‐sized mammal assemblage composition in northeastern Amazon: Drivers of β‐diversity and species interactions

AbstractUnderstanding fine‐scale assemblage composition patterns of mammals is important to increase ecological knowledge and support conservation actions. We investigated whether β‐diversity of medium and large‐sized mammals and its components (replacement and richness difference) are related to distance to major rivers, height above the nearest drainage (HAND), and vegetation height; and whether species interactions shape their spatiotemporal distribution. We used camera traps to monitor the mammal assemblage of the Tumucumaque Mountains National Park, Northeastern Amazon. The difference (Δ) in distance to major rivers and geographic distance between sites affected positively the total β‐diversity and both its components. ΔVegetation height affected total β‐diversity and species replacement, while ΔHAND affected richness differences, and to a lower extent, species replacement. We found evidence that spotted pacas (Cuniculus paca) and ocelots (Leopardus pardalis) adjust their spatiotemporal dynamics to escape from predation and to overlap with abundant prey, respectively. However, we did not find evidence that competition affects the spatiotemporal distribution of any other species. Vegetation height, distance to rivers and HAND influenced mammal assemblages probably through shaping the quality and amount of resources. Predation risk seems to be important in shaping the use of time and space by prey, while the distribution of prey is important for the use of time and space for predators. Furthermore, other niche differentiation mechanisms may explain why competition did not affect the species' spatiotemporal dynamics. We highlight the need to include different environmental contexts within protected areas to promote mammal diversity and conservation.

Sulawesi stream fish communities depend on connectivity and habitat diversity.

Streams provide an array of habitat niches that may act as environmental filters for fish communities. The tropical island of Sulawesi in Indonesia is located in the Wallacea, a region isolated by marine barriers from the Asian and Australian faunas. Primary freshwater fishes are naturally absent in the Wallacea, including Sulawesi's numerous coastal streams. Diadromous species are in contrast species-rich in the area. The knowledge available on stream fishes in the Wallacea is largely restricted to taxonomic work and studies targeting single species groups, whereas baseline data on fish ecology remain extremely scarce. Such data and a deeper understanding of stream fish ecology are, however, urgently required for purposes such as informed management. We assumed that the stream fish assemblages are dominated by recruitment from the sea and are structured by macro- and microhabitat diversity. To test this hypothesis, we quantified the occurrence of individual fishes by point abundance electrofishing at 33 streams across Sulawesi. The 4632 fishes obtained represent 58 species out of 24 families. The native fishes recorded are mainly amphidromous (34 species), euryhaline (five species), and catadromous (five species). Gobiiformes make up the vast majority of records, dominated by Oxudercidae (22 species) and Eleotridae (five species). Only two of the species recorded are endemic to Sulawesi, including a single species strictly confined to freshwaters. Ten species, making up 6% of the fishes caught, are not native to Sulawesi. The outlying mean index (OMI) and BIOENV analyses suggest that effects on the scale of macro- and microhabitat shape fish assemblage composition, ranging from pH, conductivity, and temperature to current velocity, substrate, canopy cover, and elevation. Habitat niche use of species along the first two OMI axes is complementary and fine-scaled, covering a wide range of the available habitat space. Juvenile and adult conspecifics share similar habitat niches in most of the cases. Niche breadths overlap, but niche specialization is significant in most of the species. Non-native fishes link into the assemblages at the margins of habitat space, with substantial niche overlaps to native species. The present findings show that the native fish communities in coastal streams of Sulawesi are largely composed of species depending on access to the sea, highlighting the importance of connectivity down to the estuaries and sea. The ichthyofauna shows a rich diversity in habitat use, and the availability of alternative habitats along the altitudinal gradient provides plausible filters for species establishment. Non-native fishes are locally abundant, pose substantial potential for changing communities, but are still stocked intentionally. We stress the need for incorporating the need for connectivity and maintained habitat quality into management decisions, and a critical evaluation of stocking activities.

Beaver dams in Mediterranean ecosystems: trait‐specific effects on macroinvertebrates

AbstractAfter centuries of extinction due to human persecution, Eurasian beavers Castor fiber L. have been released to Southern Europe in the last decades. Being ecosystem engineers, beavers have attracted great attention regarding restoration of aquatic and terrestrial ecosystems. Nonetheless, the effects of the species on aquatic invertebrates known to date are not univocal and mostly refer to central European riverine systems. Here, we evaluated the effects of beaver presence on aquatic macroinvertebrates for the first time in a Mediterranean riverine ecosystem, by applying a sound control‐impact sampling design and controlling for seasonal variation in macroinvertebrate assemblage composition. A significant variation in response to season was evident for macroinvertebrate communities, revealing distinct assemblages during spring and summer. Furthermore, the presence of beavers was also identified as a significant driver of species composition, as samples near the beaver dam showed significant variation from control sites. Macroinvertebrate community traits changed according to the relative position to the beaver dam, as control sites featured on average higher abundances of taxa with higher values of bioindication score, larger size, lower adaptation to drag, and were less frequently of introduced origins. Yet, these differences were strongly taxon‐ and season‐specific in their intensity and direction. Differences across sites were mainly driven by the relative abundances of few taxa—including both alien species and high environmental quality indicators—such as those from genera Potamopyrgus, Baetis, Habrophlebia, Ephemerella, Leuctra, and Radix, which explained about 70% of the observed divergence among conditions. Our results indicate that beavers and their engineering activity may induce highly variable species‐specific responses in macroinvertebrates, thus possibly representing a driver of environmental heterogeneity along Mediterranean rivers, and that both bioindicators and alien species may exploit such heterogeneity.

Influence of climate, weather and floral associations on pollinator community composition across an elevational gradient

Insect pollinators, which are ectothermic, are especially sensitive to abiotic conditions, which often drive predictable patterns of pollinator species turnover along environmental gradients. However, pollinator activity is also reliant on suitable biotic conditions, such as the presence of host plants. High‐elevation environments provide a useful setting to examine the relative contribution of abiotic and biotic factors in shaping species interactions as they are often characterised by strong environmental gradients over short geographic distances. Here, we examined pollination interaction networks across an elevational gradient from 930–2000 m a.s.l. in southern Australia, to determine the underlying patterns of pollinator activity and their interactions with flowers. Interaction frequency of Diptera increased at high elevations, while interaction frequency of Hymenoptera and Coleoptera decreased. We provide evidence that this elevational pattern of activity is partly driven by floral associations, with interactions dominated by Hymenoptera‐attracting plant families at lower elevations (Proteaceae, Fabaceae) and a Diptera‐attracting family at high elevation (Asteraceae). Pollinator activity was also influenced by weather conditions, with reduced activity for all three orders at lower temperatures, and Diptera active across the broadest range of temperature, humidity and wind conditions. We suggest that changes across elevation gradients in pollinator community composition are driven by both direct responses to abiotic conditions such as temperature, as well as the elevational distribution patterns of associated flowering plants. Despite these distinct shifts in composition of the pollinator assemblage with elevation, pollination network structure was stable across the elevational gradient, with moderate levels of specialisation and low levels of connectance and nestedness present across the gradient. By considering both abiotic conditions and biotic processes, our results provide insight for predicting the impacts of upslope vegetation shifts on pollinator communities in the face of climate change.

Australia's recently established predators restore complexity to food webs simplified by extinction.

Since prehistory, humans have altered the composition of ecosystems by causing extinctions and introducing species. However, our understanding of how waves of species extinctions and introductions influence the structure and function of ecological networks through time remains piecemeal. Here, focusing on Australia, which has experienced many extinctions and introductions since the Late Pleistocene, we compared the functional trait composition of Late Pleistocene (130,00-115,000 years before present [ybp]), Holocene (11,700-3,000 ybp), and current Australian mammalian predator assemblages (≥70% vertebrate meat consumption; ≥1kg adult body mass). We then constructed food webs for each period based on estimated prey body mass preferences. We found that introduced predators are functionally distinct from extinct Australian predators, but they rewire food webs toward a state that closely resembles the Late Pleistocene, prior to the megafauna extinctions. Both Late Pleistocene and current-day food webs consist of an apex predator and three smaller predators. This leads to food web networks with a similar total number of links, link densities, and compartmentalizations. However, this similarity depends on the presence of dingoes: in their absence, food webs become simplified and reminiscent of those following the Late Pleistocene extinctions. Our results suggest that recently established predators, even those implicated in species extinctions and declines, can restore complexity to food webs simplified by extinction.

Early warning indicators of decadal shifts in the planktonic assemblage of the Cabo Frio upwelling ecosystem

Long-term monitoring of coupled environmental and biological components in upwelling ecosystems is critical for early warning under the global warming context. Temperature, salinity, nutrients, and plankton populations are promising indicators of the ecosystem state that help us to address the current status of the oceans and construct better predictions for the future. The Cabo Frio Upwelling System (CFUS) is a regionally productive wind-driven coastal upwelling ecosystem on the northern boundary of the South Brazilian Shelf sustaining diverse marine life including large stocks of fish and squid. Like other cold marine ecosystems, most of its functioning is likely threatened by ocean warming which emphasizes the need for ecological indicators. This study aimed to analyze the causal relationships between the temporal changes in the physical and chemical properties and the dominant planktonic communities leveraging long-term observations (20 years). The results suggested a link between the temporal changes in the ecosystem conditions and the composition of the plankton assemblage, notably an increasing proportion of dinoflagellates relative to diatoms and cladocerans relative to copepods. This increase in the proportional abundance of dinoflagellates and cladocerans over time suggests a regime shift in the plankton assemblages during the 2000s, highlighting some large phytoplankton and zooplankton groups as early indicators of productivity shifts in upwelling ecosystems.

Interactive effects of aridity and local environmental factors on the functional trait composition and diversity of macroinvertebrate assemblages in dryland rivers

Drought and local habitat alteration are major environmental stressors shaping the aquatic biota in dryland rivers. However, the combined effects of these factors on aquatic biodiversity remain poorly understood. We collected macroinvertebrate data from Central Asian dryland rivers in Xinjiang, China, from 2012 to 2022, to investigate the individual and interactive effects of drought (as indicated by increasing values of Aridity, AI) and local habitat conditions (fine sediments, velocity and pH) on aquatic macroinvertebrate functional trait composition and diversity. We found that interactions of the selected environmental stressors exhibited more frequent additive than synergistic or antagonistic effects, leading to shifts in macroinvertebrate functional trait composition and diversity accordingly. Interaction of AI and fine sediments showed more pronounced synergistic effects (positive or negative) compared to others and had positive influences on traits like small body size, ovoviviparity, etc. Functional diversity metrics responded differently to stressor interactions, with FRic and FDis being negatively affected, whereas FEve was positively correlated to stressor interaction, suggesting the complementary roles of functional diversity metrics to diagnose impacts of stressor interactions. Overall, our study provides new insights into macroinvertebrate assemblage-stressor relationships in dryland rivers and can help better assess, predict and manage aquatic biodiversity in these rivers under ongoing environmental change.

The impacts of fire vary among vertical strata: Responses of ant communities to long-term experimental burning.

Fire is a powerful tool for conservation management at a landscape scale, but a rigorous evidence base is often lacking for understanding its impacts on biodiversity in different biomes. Fire-induced changes to habitat openness have been identified as an underlying driver of responses of faunal communities, including for ants. However, most studies of the impacts of fire on ant communities consider only epigeic (foraging on the soil surface) species, which may not reflect the responses of species inhabiting other vertical strata. Here, we examine how the responses of ant communities vary among vertical strata in a highly fire-prone biome. We use a long-term field experiment to quantify the effects of fire on the abundance, richness, and composition of ant assemblages of four vertical strata (subterranean, leaf litter, epigeic, and arboreal) in an Australian tropical savanna. We first document the extent to which each stratum harbors distinct assemblages. We then assess how the assemblage of each stratum responds to three fire-related predictors: fire frequency, fire activity, and vegetation cover. Each stratum harbored a distinct ant assemblage and showed different responses to fire. Leaf litter and epigeic ants were most sensitive to fire because it directly affects their microhabitats, but they showed contrasting negative and positive responses, respectively. Subterranean ants were the least sensitive because of the insulating effects of soil. Our results show that co-occurring species of the same taxonomic group differ in the strength and direction of their response to fire depending on the stratum they inhabit. As such, effective fire management for biodiversity conservation should consider species in all vertical strata.

Variability and Composition of Mysid Assemblages in a Northwest Iberian Estuary: Insights from a 10-Year Data Series

Long-term temporal studies have been used to assess the effects of climate change on mysid populations and their complex ecological interplay within heterogeneous ecosystems. This study is the first to investigate the mysid community in the Mondego estuary, western Portugal, for a decade, from 2003 to 2012. Monthly data collected from five stations along the estuary was used to investigate variations in mysid assemblage composition, patterns, phenology, and the interactions with environmental variables. Thirteen taxa were found in the assemblages. The community was dominated by Mesopodopsis slabberi, which was found in great numbers in the upper estuarine region. Praunus flexuosus and Schistomysis spiritus dominated the assemblages in the middle estuary, while Gastrossacus spinifer and Heteromysis formosa were very abundant at the mouth of the estuary. Overall, mysids were mostly present during autumn periods, when local environmental factors such as water temperature and chlorophyll-a concentrations influenced assemblage abundances. The high productivity of the system played a pivotal role in fostering greater species abundance. However, lower abundances were detected during warmer years, further evidencing changes in these key species’ communities under future climatic scenarios of increasing water temperatures.

Herbivore regulation of savanna vegetation: Structural complexity, diversity, and the complexity–diversity relationship

AbstractLarge mammalian herbivores exert strong top‐down control on plants, which in turn influence most ecological processes. Accordingly, the decline, displacement, or extinction of wild large herbivores in African savannas is expected to alter the physical structure of vegetation, the diversity of plant communities, and downstream ecosystem functions. However, herbivore impacts on vegetation comprise both direct and indirect effects and often depend on herbivore body size and plant type. Understanding how herbivores affect savanna vegetation requires disaggregating the effects of different herbivores and the responses of different plants, as well as accounting for both the structural complexity and composition of plant assemblages. We combined high‐resolution Light Detection and Ranging (LiDAR) with field measurements from size‐selective herbivore exclosures in Kenya to determine how herbivores affect the diversity and physical structure of vegetation, how these impacts vary with body size and plant type, and whether there are predictable associations between plant diversity and structural complexity. Herbivores generally reduced the diversity and abundance of both overstory and understory plants, though the magnitude of these impacts varied substantially as a function of body size and plant type: only megaherbivores (elephants and giraffes) affected tree cover, whereas medium‐ and small‐bodied herbivores had stronger effects on herbaceous diversity and abundance. We also found evidence that herbivores altered the strength and direction of interactions between trees and herbaceous plants, with signatures of facilitation in the presence of herbivores and of competition in their absence. While megaherbivores uniquely affected tree structure, medium‐ and small‐bodied species had stronger (and complementary) effects on metrics of herbaceous vegetation structure. Plant structural responses to herbivore exclusion were species‐specific: of five dominant tree species, just three exhibited significant individual morphological variation across exclosure treatments, and the size class of herbivores responsible for these effects varied across species. Irrespective of exclosure treatment, more species‐rich plant communities were more structurally complex. We conclude that the diversity and architecture of savanna vegetation depend on consumptive and nonconsumptive plant–herbivore interactions; the roles of herbivore diversity, body size, and plant traits in mediating those interactions; and a positive feedback between plant diversity and structural complexity.

Coccolithophore assemblage composition during the Greenland Interstadial-Stadial 20 transition and their response to the Youngest Toba Tuff (YTT) supereruption ∼74,000 years ago in the northeastern Arabian Sea.

Here we present a new 850-year long coccolithophore record from core SO130-289KL in the northeastern Arabian Sea that spans the Greenland Interstadial 20-Greenland Stadial 20 transition including the timing of the ∼74 ka Youngest Toba Tuff (YTT) supereruption. During the warm interstadial, the coccolithophore assemblage is characterized by Gephyrocapsa oceanica (41%) and Florisphaera profunda (30%) while the succeeding cold stadial is distinguished by the abundance of small placolith species (Emiliania huxleyi + G. ericsonii) (52%). However, the oldest samples of the study interval seem to show a stadial-like coccolithophore assemblage. Spectral analysis revealed an interdecadal cycle imprinted in the coccolithophore record during the interstadial that was also independently reported in other terrestrial and marine proxies. Immediately after the YTT eruption, small placoliths increased by 42% from 5% right below the YTT layer to 47% ∼1 mm above the YTT layer, while G. oceanica and Helicosphaera carteri increased and F. profunda decreased within the ∼1.15 cm layer representing about 8-19 years. Subsequently, the coccolithophore assemblage returned to a composition similar to the warm interstadial period before abruptly changing to a stadial composition characterized by the abundance of small placoliths about 100-130 years after the YTT eruption. Therefore, the YTT eruption had a significant impact on the overall coccolithophore assemblage but appears to have not caused the climate transition from interstadial to stadial conditions, supporting proxy and modeling data. However, the overall mechanism driving the observed changes and cyclicities remains unknown but might be related to rapid atmospheric teleconnections of North Atlantic climate variability to the low latitudes.

Drivers of Pinus halepensis Plant Community Structure across a Post-Fire Chronosequence

The Pinus halepensis (Aleppo pine) forests prevailing in the western part of the Mediterranean Basin are amongst the most severely affected by fire due to their inherent flammability. Our understanding of the environmental factors driving post-fire community dynamics is currently limited by the lack of time-series data at temporal scales. In this present study, we analyzed a chronosequence of Greek Aleppo pine forests spanning a post-fire period of 65 years. Our goal is to explore the role of post-fire age, altitude, exposure, slope level, parent-rock material, rock cover, and cover of evergreen sclerophyllous shrubs (maquis) on plant assemblage diversity (species richness and Menhinick’s diversity index) and composition. Post-fire age had a significant effect on taxonomic distinctness and community turnover but not on species richness. Taxonomic distinctness increased with post-fire age due to a higher prevalence of the families Fabaceae, Asteraceae, and Poaceae during the early post-fire period. Maquis cover was significantly associated with Menhinick’s diversity index, taxonomic distinctness, and community turnover. Exposure and slope influenced only Menhinick’s diversity index. The turnover in species composition was primarily driven by the geographical proximity of the forests and secondarily by post-fire age and the maquis cover. This highlights the importance of the initial floristic composition in the process of autosuccession after a fire in Mediterranean-climate ecosystems.

Spatio-temporal variation in mangrove crab diversity in five estuaries of Kerala, India

The present study investigated the community structure and faunal composition of mangrove crab assemblage of five estuaries in Kerala. Mangrove crabs were collected from different estuaries namely Puthuvype, Ayiramthengu, Dhalavapuram, Pullichira and Kottaramthuruth from January 2015 to December 2015. The numerical abundance was directly enumerated by handpicking crabs from the estuarial mangrove region from 100×100 cm quadrats from the estuarine mangrove regions. Thirteen brachyuran crab species were identified across the five estuaries, along with environmental and sedimentological parameters. Various diversity indices were calculated for spatial temporal comparisons. The study revealed that four of the estuaries exhibited similar crab species diversity, while Pullichira differed, displaying the lowest diversity due to habitat characteristics such as small islands or sand dunes and shallow depth. The calculated indices for species diversity, richness, dominance, evenness, taxonomic and phylogenetic relationships provide insights into the spatio-temporal variations of mangrove crab diversity. This study serves as a benchmark reference for future studies in these estuaries, and further monitoring and assessment of mangrove ecosystem health could support the development of ecosystem-based management strategies for deteriorating mangrove ecosystems.