Biological Assemblages Research Articles

Effects of Breeding Habitat on the Abundance and Body Condition of Two <i>Pelophylax</i> Species in Agriculture and Urban Landscapes

Amphibians play a key role in structuring biological assemblages of agricultural landscapes, but they are threatened globally by agricultural intensification. Numerous studies have considered the morphology of animals to be an indicator of the health of a population, but data about the differences in amphibian morphology in different breeding habitats in agricultural landscapes are still missing. Here, we investigated the differences in the abundance and morphology of Pelophylax plancyi and Pelophylax nigromaculatus in the three waterbody types: fields, forests, and parks in agricultural landscapes in Nanjing, China. Our results emphasize that both frog species in forests and parks had significantly higher body condition indexes than those in fields, whereas their abundance in fields habitat was higher than those of the two other habitat types. Our results demonstrated the importance of non-agricultural habitats (such as forests and parks) in agricultural landscapes to the persistence of both Pelophylax species. We recommend preserving field ecosystems by constructing diverse waterbodies other than fields in rural areas and maintaining microhabitats in parks and forests to improve amphibian biodiversity in Nanjing.

Taxonomic diversity of terrestrial vertebrates in west-central Mexico: Conservation from a multi-taxa perspective.

Multi-taxa approaches are increasingly used because they describe complementary aspects of ecosystem dynamics from a community ecology perspective. In west-central Mexico, the complex biogeography and topography have created an environment where temperate and tropical forests converge, resulting in great biological diversity. Within this region, the Sierra de Quila Natural Protected Area (SQPA) offers an important example for understanding ecological community dynamics. We analyze the taxonomic diversity of terrestrial vertebrates in the SQPA by incorporating taxonomic levels associated with species. We evaluated the taxonomic diversity with i) an average taxonomic distinctiveness analysis (alpha diversity) and ii) an analysis of taxonomic dissimilarity and partitioning of turnover and differences in richness components (beta diversity). Tropical forests boast the highest taxonomic diversity of amphibians, reptiles, and birds, while temperate gallery forests exhibit lower values. Our results showed that terrestrial vertebrate alpha and beta diversity patterns respond mainly to contrasting vegetation types (tropical vs. temperate). Regarding beta diversity, the multi-vegetation type analysis showed the highest values for reptiles, followed by amphibians, birds, and mammals. Turnover had the highest contribution to beta diversity, while differences in richness were relevant for amphibians and reptiles, which could be related to their low mobility and sensitivity to environmental conditions. Despite the local scale, the SQPA presented high beta diversity, reflecting historical ecological processes in taxonomic composition derived from contrasting environments and constraints imposed on species. Evaluating taxonomic structure from a multi-taxa perspective is essential for conservation efforts because it allows the spatial recognition of biological assemblages as a first step for local interventions.

Hydromorphological pressure explains the status of macrophytes and phytoplankton less effectively than eutrophication but contributes to water quality deterioration

Hydromorphological alterations are among the human-induced pressures that must be considered when assessing the ecological status of aquatic ecosystems. We investigated the effects of hydromorphological pressures on the ecological status of lowland lakes in Poland, focusing particularly on macrophyte and phytoplankton conditions. The analysis was based on biological, hydromorphological, and physicochemical data collected from 30 lowland lakes. Almost all biological and physicochemical indices correlated significantly (Spearman's |R|>0.5) with the hydromorphological index LHMS_PL. Using the variation partitioning method, we found that hydromorphological pressures explained only a small proportion (5.5%) of the variability in ecological status assessed using macrophytes. These pressures had no direct effects on the ecological status assessed using phytoplankton. The shared effects of physicochemistry and hydromorphology explained a large proportion of the variability in ecological status indices based on both phytoplankton and macrophytes. The results demonstrated that in the analysed lakes, hydromorphological alterations were usually accompanied by increased nutrient concentrations. This finding indicates that physical alterations may affect lake biological assemblages not only directly but also indirectly by reducing the ecosystem's natural buffering capacity, thereby promoting the eutrophication process.

Lack of Small-Scale Changes in Breeding Birds after a Fire: Does the Resilience of Cork Oaks Favor Rapid Recolonization in Suburban Wood Patches?

Forest fires are disturbance events that can impact biological assemblages at multiple scales. In this study, the structures of breeding bird communities in cork oak patches located in an agro-mosaic suburban landscape of central Italy (Rome) were compared at the local scale with a fine-grained mapping method before (2018) and after (2023) a fire event occurred in July 2022. The analyses did not reveal any significant changes in the density of territorial pairs or in the diversity metrics, both univariate (Shannon–Wiener index, evenness, Margalef normalized richness) and bivariate (Whittaker and k-dominance plots, abundance/biomass curves) of diversity. Even when the guilds of strictly forest-related species were compared, no differences emerged before and after the fire. This counterintuitive phenomenon may be due to the characteristics of the dominant tree, the cork oak (Quercus suber), a sclerophilous tree that is very resilient to fires and able to recover foliage in the following spring season, thus allowing rapid bird recolonization. However, other small-scale phenomena (e.g., the ‘crowding effect’ and local dispersal of territorial pairs from remnant wood patches not affected by fire) may explain this lack of change in breeding bird density and diversity. Further studies should be carried out at larger spatial and temporal scales and at different levels of fire frequency and intensity to confirm these responses at the guild/community level in suburban cork oak wood patches.

Bayesian clustering of spatially distributed compositional data with application to the Great Barrier Reef.

The relative abundance of groups of species is often used in ecological surveys to estimate community composition, a metric that reflects patterns of commonness and rarity of biological assemblages. The focus of this paper is measurements of the abundances of four benthic groups (that live on the seafloor) at several reefs on Australia's Great Barrier Reef (GBR) gathered between 2012 and 2017. In this paper we develop a statistical model to find clusters of locations with similar composition. We examine the changes in clusters during a period impacted by an unprecedented sequence of extreme environmental disturbances. To achieve this, we propose a model that incorporates the geographical location of the data, accounting for the possibility that nearby reefs are similar in composition. This is accomplished with a Dirichlet mixture model and a Potts distribution on the cluster assignments. Non-availability of the normalised Potts distribution makes Bayesian inference a doubly-intractable task. To circumvent this additional inferential challenge, an approximate exchange algorithm is specified. The analysis of the 2012 data, collected before the weather disturbances, reveals four clusters. The four groups highlight the primary habitat patterns in the 2012 GBR, each with distinct ecological characteristics: (1) areas with above-average soft coral abundance, (2) sand-dominated regions commonly found in the central part, (3) southern reefs with a more balanced distribution of species, and (4) habitats dominated by algae and hard corals. Compared to subsequent surveys conducted after disturbances, there is evidence of a decline in the number of clusters and a simplification of reef composition at the regional scale.

Macroinvertebrate, algal and diatom assemblages respond differently to both drying and wetting transitions in non‐perennial streams

Abstract Biological assemblages in streams are influenced by hydrological dynamics, particularly in non‐perennial systems. Although there has been increasing attention on how drying impacts stream organisms, few studies have investigated how specific characteristics of drying and subsequent wetting transitions influence biotic responses via resistance and resilience traits. Here, we characterized how hydrologic metrics, including those quantifying drying and wetting transitions as well as dry and wet phases, alter diversity and composition of three aquatic assemblages in non‐perennial streams in southern California: benthic macroinvertebrates, soft‐bodied algae and diatoms. We found that flow duration prior to sampling was correlated with variation in macroinvertebrate and soft‐bodied algal assemblage composition. The composition and richness of diatom assemblages, however, were predominantly influenced by the drying start date prior to sampling. Contrary to other studies, the duration of the dry phase prior to sampling did not influence the composition or richness of any assemblage. Although our study was conducted within a region in which each assemblage experienced comparable environmental conditions, we found no single hydrologic metric that influenced all assemblages in the same way. The hot‐summer Mediterranean climate of southern California likely acts as a strong environmental filter, with taxa in this region relying on resistance and resilience adaptations to survive and recolonize non‐perennial streams following wetting. The different responses of algal and diatom assemblages to hydrologic metrics suggest greater resilience to drying and wetting events, particularly for primary producers. As drying and wetting patterns continue to change, understanding biodiversity responses to hydrologic metrics could inform management actions that enhance the ecological resilience of communities in non‐perennial streams. In particular, the creation and enhancement of flow regimes in which natural timing and duration of dry and wet phases sustain refuges that support community persistence in a changing environment.

Threshold Response Identification to Multi-Stressors Using Fish- and Macroinvertebrate-Based Diagnostic Tools in the Large River with Weir-Regulated Flow

Biodiversity response-based diagnostic tools are nonlinear approaches that simultaneously consider complex environmental stressors. Such approaches have been used to quantify biological responses to environmental changes. This study identified the major environmental stressors of community turnover and corresponding thresholds by applying diagnostic tools that use multiple biological assemblages in a large river with artificially controlled flow. Four Gradient Forest models were constructed using the relationships between stream biological assemblage and 66 parameters over 12 years. The multi-stressors that caused community turnover and their thresholds differed depending on the biological assemblage, even under the same environmental conditions. Specifically, they showed that operation of weirs has increased the importance of certain species (e.g., non-native species). In addition, specific-taxon response to multi-stressors analysis identified the ecological or management thresholds of endangered species, Korean endemic species, non-native species, and legal pollution indicator species, which must be managed from a biodiversity perspective. These thresholds are significant as the first reference points presented in similar ecological environments and can be used as guidelines for species over the long term. We propose that ‘true’ threshold identification requires efforts to recognize and improve the limitations of GF techniques confirmed in this study. This may ultimately enable a sustainable aquatic ecosystems maintenance and biodiversity preservation.

The influence of stream nutrients and habitat on three biological assemblages

The influence of stream nutrients and habitat on three biological assemblages

Geographic patterns and climatic drivers of phylogenetic structure of liverworts along a long elevational gradient in the central Himalaya

AbstractFor clades originating in warm climates, the tropical niche conservatism hypothesis predicts that current biological assemblages in colder or drier climates are expected to have lower phylogenetic diversity, and species in colder or drier climates are expected to be more closely related to each other (i.e., higher phylogenetic clustering). Liverworts are one of the oldest clades of extant land plants. They originated about 500 Ma during a warm (“greenhouse”) period and experienced multiple major cycles of warm and cold periods. Here, I test the tropical niche conservatism hypothesis using liverwort assemblages distributed along an elevational gradient crossing about 5000 m of elevation in the central Himalaya. I found that, in general, phylogenetic diversity and dispersion decrease with increasing elevation and thus with decreasing temperature, which is consistent with the tropical niche conservatism hypothesis. Phylogenetic diversity decreases with elevation monotonically, but phylogenetic dispersion decreases with elevation in a triphasic (zig‐zag) pattern, which is generally consistent with the triphasic pattern found in angiosperms and polypod ferns along the same elevational gradient. Temperature‐related variables explained approximately the same amount of the variation in phylogenetic diversity and dispersion as did precipitation‐related variables, although mean annual temperature explained 9%−15% more variation than did annual precipitation. Climate extreme variables explained approximately the same amount of variation in phylogenetic diversity and dispersion as did climate seasonality variables.

Weak congruence between biological assemblages of streams and their relationship with the environmental gradient in the Cerrado–Amazon transition area, Brazil

Weak congruence between biological assemblages of streams and their relationship with the environmental gradient in the Cerrado–Amazon transition area, Brazil

Bioindicator aquatic insects at risk from climate change in a biodiversity hotspot

Climate change can affect biological assemblages by shifting their species' geographic range and changing species richness. Aquatic insects represent more than half of the freshwater animal species but have been neglected mainly in climate change assessments, particularly in tropical ecosystems. Among the aquatic insect taxa, Ephemeroptera, Plecoptera, and Trichoptera (EPT) are well-known bioindicators of environmental changes and encompass an essential metric for rivers and streams' biomonitoring. Here, we use ecological niche models to project the impact of climate change on the distribution range and richness of EPT in the Atlantic Forest biodiversity hotspot. We found EPT to be at high risk from future climate change, with Plecoptera as the order of greatest concern. We projected range contraction of ca. 90 % of the analyzed EPT genera, resulting in a reduction in the richness of EPT genera under future climatic conditions. We projected >50 % contraction in the distribution of 50 % of Plecoptera, ≈14 % of Trichoptera, and ≈7 % of Ephemeroptera genera. The remaining climatically suitable regions in the Atlantic Forest are concentrated in the high-altitude areas, which may act as climate refuges for EPT biodiversity in the future. The projected changes in EPT's distribution range and richness may impact biomonitoring programs conducted in tropical ecosystems. Restricting EPT's geographic distribution may undermine its potential as a bioindicator and influence the composition of EPT assemblages at reference sites, which may lead to shifting baseline conditions. We reinforce the importance of considering future climatic conditions when planning long-term biomonitoring and priority areas for conservation.

Fish and macroinvertebrates respond differently to seasonal drying in tropical non‐perennial streams

AbstractSurface water drying challenges the persistence of lotic biological assemblages in non‐perennial streams and rivers. However, the effects of natural hydrological disturbances on an assemblage depend on individual species characteristics. In this study, we investigated the structure and association of fish and macroinvertebrate assemblages during two phases in non‐perennial streams (flowing vs. disconnected pools). We sampled fish and macroinvertebrate assemblages in five non‐perennial stream reaches located in the Caatinga (Brazilian semi‐arid region). Fish species were resistant to hydrological dynamics in the streams. On the other hand, some macroinvertebrate taxa from the flowing phase disappeared, and new taxa colonized the disconnected pools. The absence of lotic insects following flow cessation and the colonization of disconnected pools by lentic taxa facilitated macroinvertebrate assemblages persistence in these dynamic streams. Our study showed that fish and macroinvertebrate assemblages respond differently to the same natural flow cessation, which leads us to predict that flow changes will yield different assemblages, depending on the taxa. Thus, it is crucial to consider multi‐assemblage responses to effectively manage and conserve non‐perennial stream ecosystems in a tropical semi‐arid region.

Flower-visiting lizards as key ecological actors for an endemic and critically endangered plant in the Canary Islands

Oceanic islands are places where biological assemblages are relatively simple, as compared to the mainland. On islands, however, pollinator assemblages may to be composed of a taxonomically disparate group of organisms (e.g. insects, lizards, and birds), some of them with opportunistic nectar-feeding behaviour. Here we investigated some components of pollination effectiveness of Lotus maculatus (Fabaceae), an endangered Canary Islands endemic. In a flower exclusion experiment, we bagged flowers and compared their subsequent fruit and seed set to that of control flowers. Number of interactions with vertebrate and invertebrate flower visitors was counted and it was recorded whether interactions were legitimate (potentially pollinating) or non-legitimate (nectar robbing). Additionally, we estimated pollen loads on lizards and looked for any relationship between reproductive success of individual plants and number of visits made by the top three flower-visiting species (in terms of both frequency of occurrence at censuses and number of floral visits). Bagged flowers fruited less and with fewer seeds than control flowers. The only observed flower-visiting vertebrate was the Tenerife lizard Gallotia galloti, whose interactions were always legitimate and with around a half of captured individuals carrying pollen grains. The most frequent flower-visiting insect was the honeybee Apis mellifera followed by the solitary bee Lasioglossum arctifrons. The honeybee, however, was only a nectar robber, and the solitary bee was not an effective pollinator, but rather a pollen gatherer. Fruit set by individual plants was positively related only to frequency of visits by the lizard. Thus, the lizard seems to play a key role in the conservation management of L. maculatus.

Effects of a beaver dam on the benthic copepod assemblage of a Mediterranean river

As known “ecosystem engineers”, beavers influence river hydrology, geomorphology, biochemistry, and biological assemblages. However, there is a lack of research regarding the effects of beaver activities on freshwater meiofauna. In this study, we investigated the taxonomic and functional composition of the benthic copepod assemblage of a segment of the Tiber River (Italy) where a beaver dam, created about 7 weeks before our survey, had formed a semi-lentic habitat upstream and a lotic habitat downstream of the dam. We also analyzed the copepod assemblage before and after a flood event that destroyed the beaver dam, providing a unique opportunity to observe changes in a naturally reversing scenario. Our analyses revealed that, while the taxonomic composition and functional traits of the copepod assemblage remained largely unchanged across the recently formed semi-lentic and lotic habitats, substantial differences were evident between the dammed and undammed states. The dammed state showed lower copepod abundances, biomass, and functionality than the undammed one. These results highlight the role of beaver dams in changing the composition and functionality of meiofaunal assemblages offering insights into the dynamic interactions within aquatic ecosystems.

Characteristics of Key Biological Assemblage Dynamics and Biotic Integrity Assessment in the Upper Yellow River, China

Characteristics of Key Biological Assemblage Dynamics and Biotic Integrity Assessment in the Upper Yellow River, China

Effects of climate and environmental heterogeneity on the phylogenetic structure of regional angiosperm floras worldwide

The tendency of species to retain ancestral ecological distributions (phylogenetic niche conservatism) is thought to influence which species from a species pool can persist in a particular environment. Thus, investigating the relationships between measures of phylogenetic structure and environmental variables at a global scale can help understand the variation in species richness and phylogenetic structure in biological assemblages across the world. Here, we analyze a comprehensive data set including 341,846 species in 391 angiosperm floras worldwide to explore the relationships between measures of phylogenetic structure and environmental variables for angiosperms in regional floras across the world and for each of individual continental (biogeographic) regions. We find that the global phylogenetic structure of angiosperms shows clear and meaningful relationships with environmental factors. Current climatic variables have the highest predictive power, especially on phylogenetic metrics reflecting recent evolutionary relationships that are also related to current environmental heterogeneity, presumably because this favors plant speciation in various ways. We also find evidence that past climatic conditions, and particularly refugial conditions, play an important role in determining the phylogenetic structure of regional floras. The relationships between environmental conditions and phylogenetic metrics differ between continents, reflecting the different evolutionary histories of their floras.

Low diversity and abundance of predatory fishes in a peripheral coral reef ecosystem.

Semi-enclosed seas are often associated with elevated local threats and distinct biogeographic patterns among marine fishes, but our understanding of how fish assemblage dynamics vary in relation to relatively small semi-enclosed seas (e.g., the Gulf of Aqaba) remains limited. Baited remote underwater video surveys (n = 111) were conducted across ~300 km of coral reef habitats in the Gulf of Aqaba and the northern Red Sea. A total of 55 predatory fish species were detected, with less than half of all species (n = 23) observed in both basins. Relative abundance patterns between the Gulf of Aqaba and the northern Red Sea were variable among taxa, but nearly twice as many predatory fish were observed per unit of effort in the northern Red Sea. In general, assemblages in both basins were dominated by three taxa (Epinephelinae, Carangidae, and Lethrinidae). Large-bodied and threatened species were recorded at very low abundances. Multivariate analysis revealed distinct assemblage structuring of coral reef predators between the Gulf of Aqaba and the northern Red Sea. Most of the species driving these differences were recorded in both basins, but occurred at varying levels of abundance. Environmental factors were largely unsuccessful in explaining variation in assemblage structuring. These findings indicate that biological assemblages in the Gulf of Aqaba are more distinct than previously reported and that reef fish assemblage structuring can occur even within a relatively small semi-enclosed sea. Despite inter-basin assemblage structuring, the overall low abundance of vulnerable fish species is suggestive of overexploitation in both the Gulf of Aqaba and the northern Red Sea of Saudi Arabia. As the region surveyed is currently undergoing large-scale coastal development, the results presented herein aim to guide spatial management and recovery plans for these coral reef systems in relation to this development.

Marine protection enhances the resilience of biological communities on temperate rocky reefs

Abstract Conservation science faces the urgent challenge of halting the biodiversity loss caused by the biological crisis of the present era. To achieve this, conservation science requires cutting‐edge tools to focus on vital properties of ecosystems, such as the resilience. Resilience informs about the cost of recovering biological communities. Here, we developed a metric to quantify the ecological assemblage recovery cost based on the dissimilarity between unprotected and partially protected communities compared with totally protected communities in Cabo de Gata Marine Reserve. Our results show that the biological assemblage composed of fish, macroinvertebrates and cryptic fish, and macroalgae species in unprotected zones requires a higher ecological recovery cost than in partially protected zones when moving towards a fully protected community. This research contributes to monitoring marine the effectiveness of marine protection from a resilience perspective, with the goal of promoting the use of the recovery cost metric for building resilient coastal ecosystems.

Geomorphometric maps of Australia’s Marine Park estate and their role in improving the integrated monitoring and management of marine ecosystems

The loss of marine biodiversity is a major global issue that needs to be prioritised. In Australia, a considerable proportion (48%) of its Exclusive Economic Zone is dedicated to marine protected areas. To effectively manage this network of marine protected areas Australia has recently introduced a Management Effectiveness system. This system is designed to identify, monitor, and manage natural values and the various activities and pressures affecting the Australian Marine Parks (AMPs). Key to this approach is the identification and accurate mapping of the location of these values and pressures acting on the seabed. The AusSeabed program is a national initiative in Australia aimed at improving access to bathymetric data and coordinating efforts to collect such data in Australian waters. This manuscript proposes a novel systematic processing method to create detailed and scalable geomorphometric maps from AusSeabed’s bathymetric data holdings, intended as a standard operating procedure for initial bathymetric data interpretation in the AMPs. Utilising this workflow, we produce seafloor geomorphometry maps across 37 AMPs within which sufficient bathymetric data has been collected. These maps can be used 1) for predictive mapping of biological assemblages; 2) in field sampling design for the collection of ‘ground truthing’ data (e.g. underwater imagery and sediment samples) to validate habitat maps from bathymetric datasets; and 3) as input datasets for subsequent geomorphological mapping with a deeper understanding of seafloor processes. This research highlights the importance of robust geomorphometry classification standards to ensure consistency in mapping Australia’s marine estate in preparation for the Decade of Oceans plans. The Seamap Australia program provides a stepwise approach to advancing Australia’s national collection of bathymetric data into derived products that can enable habitat mapping of Australian waters, providing a foundational tool for the adaptive management of AMPs.

It is not a mere piece of the mainland: Fluvial islands contribute to regional spider diversity in a seasonally flooded Amazonian archipelago

Abstract Islands and analogous insular habitats are found in several ecological contexts. With the exception of oceanic islands, however, the contribution of these insular habitats to regional biodiversity remains poorly investigated, especially in tropical regions. We investigated the understory spider assemblages in an Amazonian river archipelago to evaluate the contribution of fluvial islands to regional spider diversity. We collected spiders on 30 islands ranging from 1 to 1527 ha and at 23 sites in mainland habitats represented by continuous igapó flooded forests and terra firme forests. Spiders were collected by shaking the vegetation over a white sheet during a standardised time of 30 min. From 1404 adult individuals, we identified 290 spider species or morphospecies, with 150 species being recorded on the fluvial islands, 122 in the igapó flooded forests and 103 in the terra firme forests. Spider assemblages of fluvial islands exhibit lower alpha diversity and equitability compared with mainland habitats. The species composition of fluvial islands was significantly distinct from that of mainland habitats, even when compared with neighbouring igapó flooded forests. Several families and species of spider were significantly associated with a particular habitat, including 8 families and 10 species identified as indicators of fluvial islands. Fluvial islands effectively contribute to regional diversity since their spider fauna is not a mere impoverished subset of species from mainland habitats. Events that alter the flood pulse in Amazonian rivers (e.g., construction of hydroelectric dams) could threaten the unique biological assemblages of the floodplain habitats, especially the fluvial islands.