Search Results (32)

Adaptive radiations are characterized by increases in rates of lineage and trait evolution, typically due to the opening of new ecological opportunities such as may follow from dispersal to a new region or the evolution of a trait that allows exploitation of new niches. This results in clades that have accumulated unusually high biological diversity within a relatively short evolutionary timespan and hence the phenomenon has attracted longstanding interest amongst evolutionary biologists. Natricidae is a family of snakes with a primarily Old World distribution but which have colonized the New World on a single occasion. This dispersal event coincides with an increased speciation rate that has led to a species-rich New World clade. Herein, we take a phylogenetic comparative approach to investigate a likely adaptive radiation of New World natricids. We first confirmed previously reported findings of a single origin (providing new ecological opportunity) coinciding with a burst of lineage diversification. We then estimate the rates of evolution for three ecologically important traits (body size and broad categories of diet and habitat) separately for New World and Old World natricids. Of these three traits, our results provide evidence that only transition rates between terrestrial and (semi-)aquatic habitats are higher in the New World clade. Taken together, this supports a scenario of an adaptive radiation in natricids primarily associated with differentiation by habitat as the clade spread across the New World following its arrival there. Considering other adaptive radiations alongside our evidence for Natricidae, we propose the hypothesis that there is a common distinction between spatially constrained ‘island’ adaptive radiations (which often diverge along trophic axes) and continental adaptive radiations, which diverge as the clade spreads across a larger spatial scale and adapts to different habitats. Full article

To clarify the response mechanisms of soil nematodes as bioindicators of ecosystem health to precipitation variations in loess hilly forests, this study investigated soil nematodes in pure Populus hopeiensis forests across different precipitation gradients in Wuqi County. Through soil physicochemical analysis and high-throughput sequencing of soil nematodes, we analyzed the characteristics of soil nematode communities and their responses to precipitation variation. The results demonstrated the following: (1) Dominant genera and trophic groups of soil nematodes were significantly influenced by precipitation, with Acrobeloides prevailing across all gradients while Paratylenchus reached maximum abundance (26.8%) in moderate precipitation zones. (2) Bacterivorous nematodes prevailed in both low- and high-precipitation zones, while herbivorous nematodes constituted the highest proportion in moderate precipitation zones. The abundances of herbivorous and fungivorous nematodes exhibited an initial increase followed by a decrease with rising precipitation, whereas predatory–omnivorous nematodes displayed the opposite trend. (3) The Chao1 and Shannon indices of soil nematodes initially increased and then decreased with increasing precipitation, reaching a peak in the Jinfoping site. Moreover, there were significant differences in nematode community structure among different precipitation gradients. (4) Redundancy analysis and PLS-PM modeling identified soil water content (SWC), total nitrogen (TN), and capillary water holding capacity (CWHC) as key drivers of nematode communities. Precipitation indirectly regulated nematode functionality by modifying soil physicochemical properties and microbial activity. (5) Ecological function analysis revealed bacterial-dominated organic matter decomposition (Nematode Channel Ratio, NCR > 0.75) in the Changcheng and Baibao sites, contrasting with fungal channel predominance (NCR < 0.75) in Jinfoping. This research elucidates the mechanism whereby precipitation drives nematode community divergence through regulating soil physicochemical properties and microbial activity. The findings provide scientific basis for soil biodiversity conservation and ecological restoration benefit assessment in regional ecological restoration projects, and soil health management and sustainable land use in agricultural ecosystems. Full article

Climate change is a major challenge affecting marine environments, making it essential to understand species distribution responses in both time and space for effective conservation strategies. Meanwhile, varying responses of species to climate change may lead to changes in interspecific relationships and future spatial distributions. This study assessed spatial and temporal distributions of four trophically dependent species of economic importance in the China seas, including largehead hairtail (Trichiurus lepturus), Spanish mackerel (Scomberomorus niphonius), chub mackerel (Scomber japonicus), and anchovy (Engraulis japonicus). By incorporating fishery-dependent survey data and environmental variables, we developed a spatio-temporal mixed-effects model to analyze the distributional correlations among these species and predicted their distributions by the end of the century under different climate change scenarios. The results showed that the selected environmental factors influenced encounter probability and catch rates differently. Predictions for the end of the century under representative concentration pathways (RCPs) 2.6 and RCP8.5 suggested significant shifts in population densities, with species like T. lepturus and S. niphonius experiencing reduced densities and altered spatial patterns, while E. japonicus may benefit from climate change. The center of gravity for most species was projected to shift northward by the year 2050, with notable variations under RCP8.5. Additionally, spatial overlap among species was expected to decrease significantly by the year 2100, indicating increasing divergence in their distributions. This study underscores the effects of climate change on species habitat distribution and offers a scientific basis for future habitat protection. Full article

Soil biodiversity plays a critical role in supporting multiple ecosystem functions. As some of the most diverse and abundant metazoans on the Earth, soil nematode communities exhibit changes along environmental gradients, but the ways in which the abundance and diversity of nematode communities vary along elevational gradients remain poorly understood. Taking advantage of an investigation on Huangshan Mountain, Southeast China, with elevation ranging from 500 to 1200 m, we assessed the abundance and diversity of soil nematodes, as well as the soil physicochemical properties, across subtropical forest ecosystems. Nematode communities were analyzed at the genus level, and the α-diversity was calculated as the genus richness, while the β-diversity was based on the Bray–Curtis dissimilarity. The results showed that, among the top 20 nematode genera ranked by absolute abundance, most genera, such as Eucephalobus, Prismatolaimus, Filenchus, and Rotylenchulus, reached their peak abundance at the highest elevation (1000 m). Additionally, the abundances of Oriverutus, Tylenchus, Criconema, and Tripyla exhibited a positive correlation with the elevation. Moreover, the abundance and α-diversity of the total nematodes and each trophic group of nematodes increased linearly with the elevation, likely due to increased soil moisture at higher elevation. In contrast, the β-diversity of the total nematodes, bacterivores, and herbivores decreased with increasing elevation, indicating the importance of stochastic processes in shaping community assembly at high altitudes. This pattern suggests that as the elevation increases, the nematode communities become more homogeneous in structure. Taken together, our study’s findings demonstrate the divergent responses of nematodes’ α- and β-diversity to an elevation gradient, highlighting the importance of the soil nematode diversity in maintaining ecosystem functions such as nutrient cycling and food web stability in mountainous regions. These results emphasize the need to incorporate the below-ground biodiversity into conservation strategies, particularly in the face of environmental changes driven by climate and human activities. Full article

Climate change has led to significant fluctuations in marine ecosystems. As a component of the food web, the trophic diversity and spatiotemporal changes of fish communities are crucial for understanding ecosystems. In recent years, stable isotope analysis has been increasingly used as a comprehensive tool for quantitative assessment of trophic diversity to explore spatiotemporal variations in fish community diversity. This study is based on carbon ($\delta$¹³C) and nitrogen ($\delta$¹⁵N) stable isotope analysis using different biomass-weighted isotope diversity indices, including isotopic divergence index (IDiv), isotopic dispersion index (IDis), isotopic evenness index (IEve), and isotopic uniqueness index (IUni). The overall results indicate that IDis, IEve, and IUni values of fish communities were relatively low, while IDiv was relatively high in the Haizhou Bay ecosystem. IDiv, IDis, IEve, and IUni were lower in autumn than in spring; IDiv and IDis were relatively higher in offshore waters, while IEve and IUni were relatively higher in inshore waters. The changes in species composition and intensive pelagic–benthic coupling in Haizhou Bay may lead to significant spatiotemporal variations in the trophic diversity of fish communities in the area. These findings highlight the importance of incorporating trophic relationships into ecosystem models, which will help to enhance our understanding of the complexity of the trophic structure of fish communities. Full article

Fisheries and bottom seawater data were collected in July in 2022 and 2023 from 15 sampling stations in the Huanghe River estuary and adjacent seas in China. The patterns of functional alpha and beta diversity of fish communities in this area and their relationships with environmental factors were studied using trait-based analysis. Five functional classifications, which included 16 functional traits, four functional alpha diversity indices (functional richness, functional evenness, functional divergence, and community-weighted mean), three functional beta diversity indices (functional beta diversity and its turnover and nestedness components), and 14 bottom environmental factors were considered. The dominant traits of fish communities were the following: benthivorous feeding habits, small and front-facing mouths, high trophic level, demersal, anguilliform, low growth coefficient, medium resilience, low vulnerability, and adapted to warm temperate conditions. The dominant migration traits and types of fish eggs varied by year, and fish abundance was the main factor affecting the dominant traits of the communities. The results of multiple regression on distance matrices and variance partitioning analysis indicated that ammonia nitrogen content, total phosphorus content, and pH were the main environmental factors that affected fish functional diversity. The N/P ratio had a bottom-up control effect on fish functional diversity. Our findings also revealed that high pH gradients and distant geographical distances can inhibit trait turnover in fish communities. Full article

Notothenioid fishes, a perciform group, radiated in the cold shelf waters around the Antarctic continent and the 110 species dominate fish diversity, abundance, and biomass at levels of ≈77%, 92%, and 91%, respectively. This occurred in a locality with frequent glaciomarine cycles that fragmented and obliterated habitats, disrupted ecosystems, and made parts of the high latitude shelves periodically uninhabitable. The notothenioid radiation encompasses three stages and 10 axes: for the habitat stage, divergence in (1) depth and (2) biotope, meaning subdivisions within the pelagic and benthic realms; for the morphology stage, divergence in (3) body size, (4) body density based on proportions of skeletal and adipose tissues, (5) body shape, (6) trophic morphology, specifically head morphology related to feeding (jaws, teeth, head size, and pharyngeal gape), and (7) neuromorphology (brain and sensory systems); and for the communication stage, divergence in (8) fecundity and egg size, (9) sexual dichromatism and dimorphism in body and fins, and (10) parental care behavior associated with nesting. There was an antecedent Eocene fossil fauna that did not include notothenioids and that has minimal taxonomic representation in the modern fauna. Liparids (snailfishes) and zoarcids (eelpouts) also diversified in Antarctic waters but with minimal divergence. Hypotheses are offered as to why these radiations played out the way they did and why notothenioids are dominant. Full article

In marine ecology, the most studied interactions are trophic and are in networks called food webs. Trophic modeling is mainly based on weighted networks, where each weighted edge corresponds to a flow of organic matter between two trophic compartments, containing individuals of similar feeding behaviors and metabolisms and with the same predators. To take into account the unknown flow values within food webs, a class of methods called Linear Inverse Modeling was developed. The total linear constraints, equations and inequations defines a multidimensional convex-bounded polyhedron, called a polytope, within which lie all realistic solutions to the problem. To describe this polytope, a possible method is to calculate a representative sample of solutions by using the Monte Carlo Markov Chain approach. In order to extract a unique solution from the simulated sample, several goal (cost) functions—also called Ecological Network Analysis indices—have been introduced in the literature as criteria of fitness to the ecosystems. These tools are all related to information theory. Here we introduce new functions that potentially provide a better fit of the estimated model to the ecosystem. Full article

Rapid urbanization has triggered nutrient loading, which will inevitably lead to the eutrophication of water bodies and further affect the structure of aquatic populations. At present, eutrophication is a significant challenge for urban aquatic ecosystems. However, we still know little about the correlation between eutrophication in urban rivers and the composition of aquatic functional groups. The effects of urban river eutrophication on rotifer communities were investigated using an annual field survey of the Jinan section of the Xiaoqing River, a typical urban river in northern China. Using functional diversity (FD) and beta diversity, the spatiotemporal variation of the aquatic biological functional groups regime along stretches subject to different eutrophication was investigated. The functional evenness (FEve) and functional divergence (FDiv) decreased significantly with the increment of the trophic level index. Functional diversity exhibits an extremely low level across functional groups, with the richness difference (RichDiff) being an important component. The results indicate that eutrophication led to the homogenization of rotifer communities. This can be attributed to the functional homogenization of the rotifer community in the Jinan section of the Xiaoqing River. The observed homogenization may be due to widely distributed species complementing the ecological niche space. Our findings provide valuable information on the conservation of the urban river under the threat of eutrophication caused by high-intensity human activities. Full article

An advanced characterization of the trophic niche of non-indigenous species (NIS) may provide useful information on their ecological impact on invaded communities. Here, we used carbon and nitrogen stable isotopes to estimate pairwise niche overlaps between non-indigenous and native consumers in the winter food web of Lake Trasimeno (central Italy). Overall, a relatively low pairwise overlap of isotopic niches was observed between NIS and native species. The only exception was the Louisiana crayfish Procambarus clarkii, which showed a relatively high and diffuse overlap with other native invertebrates. Our findings highlighted a high niche divergence between non-indigenous and native species in Lake Trasimeno, suggesting a potentially low degree of interspecific competition that may facilitate coexistence and, in turn, limit the strength of impacts. The divergent results obtained for the Louisiana crayfish indicate that additional control measures for this invasive species are needed to mitigate its impact on the Lake Trasimeno system. Full article

Macroevolutionary patterns in the association between plant species and their herbivores result from ecological divergence promoted by, among other factors, plants’ defenses and nutritional quality, and herbivore adaptations. Here, we assessed the performance of the herbivores Lema trilineata daturaphila, a trophic specialist on Datura, and Spodoptera frugiperda, a polyphagous pest herbivore, when fed with species of Datura. We used comparative phylogenetics and multivariate methods to examine the effects of Datura species’ tropane alkaloids, leaf trichomes, and plant macronutrients on the two herbivores´ performances (amount of food consumed, number of damaged leaves, larval biomass increment, and larval growth efficiency). The results indicate that species of Datura do vary in their general suitability as food host for the two herbivores. Overall, the specialist performs better than the generalist herbivore across Datura species, and performance of both herbivores is associated with suites of plant defenses and nutrient characteristics. Leaf trichomes and major alkaloids of the Datura species are strongly related to herbivores’ food consumption and biomass increase. Although hyoscyamine better predicts the key components of the performance of the specialist herbivore, scopolamine better predicts the performance of the generalist; however, only leaf trichomes are implicated in most performance components of the two herbivores. Nutrient quality more widely predicts the performance of the generalist herbivore. The contrasting effects of plant traits and the performances of herbivores could be related to adaptive differences to cope with plant toxins and achieve nutrient balance and evolutionary trade-offs and synergisms between plant traits to deal with a diverse community of herbivores. Full article

Ants of the genus Formica play an important role in biogenesis by participating in various processes, including the formation of complex trophic networks. The role of ants in an ecosystem depends on their species and geographic population, which can be difficult to identify. Formica gagatoides with a wide range and F. kozlovi are among some examples. The question is whether the Siberian populations of F. kozlovi really belong to this species or are local populations of F. gagatoides. Based on the materials collected in Russia (Murmansk Region, the north of the Krasnoyarsk Territory, Altai, Far East), a morphological analysis (key diagnostic features) and molecular genetic analysis (COI, ITS1, D2 28S) were carried out. In all localities, there were individuals with pure (gagatoides, kozlovi) and mixed (gagatoides/kozlovi) morphotypes, with the exception of the Magadan Region, where the kozlovi morphotype was absent. According to the phylogenetic trees, F. gagatoides formed separate geographical branches, with the Siberian F. kozlovi being close and clearly conspecific to the Asian branch of F. gagatoides. A relatively high COI divergence, along with some differences in the ITS1 sequences, between the Asian and European F. gagatoides raises the question about the conspecificity of the Asian and European branches of this species. Full article

The Antarctic endemic fish genus Trematomus (Trematominae, Notothenioidei) includes 15 species very diverse in morphology, lifestyle and feeding ecology. Co-occurring on the continental shelf, they occupy different habitats and a wide range of ecological niches as the result of adaptive radiation during their evolutionary history. Ecomorphological differentiation is a key feature of adaptive radiations, with a general trend for specialization following divergence. Here, we investigated the trophic adaptive morphology and ecology of six Trematomus species from Terra Nova Bay (Ross Sea) through feeding apparatus metrics and geometric morphometrics. The suction index (SI), the mechanical advantage in jaw closing (MA), the relative surface of the adductor mandibulae muscle and nine morphological traits related to feeding structures were analysed. Head shape clearly differentiates the benthic (T. bernacchii, T. hansoni and T. pennellii) from the pelagic (T. eulepidotus and T. borchgrevinki) species. The position of the eyes and the orientation of the mouth also contribute to specific morphological differences and specialization. Interestingly, T. newnesi stands at an intermediate position and the mouth is clearly oriented upwards compared to the other congeneric species. Full article

Pachycormiformes is a diverse clade of stem-teleost actinopterygian fishes with a stratigraphic range from the Lower Jurassic (Toarcian) to Upper Cretaceous (Maastrichtian). The Toarcian Posidonienschiefer Formation in SW Germany records the earliest occurrence of †Pachycormiformes in the fossil record, offering unique and crucial insight into the clade’s origins and early adaptive radiation in the Early Jurassic. However, Early Jurassic taxa remain poorly studied with the taxonomic diversity and stratigraphic/geographic distributions insufficiently defined, thus masking the early part of this evolutionary radiation. Here, we report a new genus and species of pachycormid fish from the Posidonienschiefer Formation identified by phylogenetic analysis as falling in an intermediate position between Saurostomus and Ohmdenia at the base of the suspension-feeding clade. The new taxon shows a unique suite of cranial and postcranial characters. Several synapomorphies of the suspension-feeding clade, notably, the morphology of the hyomandibula, elongation of the skull, and reduced squamation are shared with the new taxon. The intestinal tract is exceptionally preserved, providing one of the most complete examples of pachycormid gastric anatomy. A comparison of the gastrointestinal anatomy of the new genus with other pachycormiforms indicates extensive taxonomic variation within the clade, in the configuration of both the midgut and spiral valve, potentially related to trophic divergence. The results highlight an underestimated high diversity and the rapid acquisition of trophic specializations in Pachycormiformes much earlier in the clade’s evolution than previously considered. Full article

Integrated multi-trophic aquaculture (IMTA) systems integrate the cultivation of species from different trophic levels. Uneaten feed, solid wastes, and dissolved nutrients are turned into harvestable and healthy food, making IMTA a driver for ecologically sustainable aquaculture. Its wider sustainability potentials arise from social, environmental, and economic sustainability enhancement options. Biological and economic outcomes are promising, while social equity and acceptance remain to be further investigated in the context of the long-term viability of aquaculture. Sustainable coastal and marine aquaculture development requires a holistic approach that involves social/cultural, economic, as well as environmental sustainability. This article examines IMTA as a pathway to socially, environmentally, and economically sustainable development. We collate evidence that shows that IMTA can minimize the negative environmental effects of aquaculture, assist local economies, and boost competitiveness and long-term economic viability. Available analyses of socio-economic and cost-effectiveness reveal positive prospects for IMTA systems, through product diversification, faster production cycles, and IMTA product prices and show a divergence between financial returns at the level of the entrepreneurial unit and economic returns at the macro level, which inhibits the uptake of IMTA. We conclude that the lack of governance analysis or inappropriateness of institutional development, in terms of aquaculture governance and management laws and regulations, is at the core of the hitherto weak engagement with IMTA. Unsuitable policies, regulations, and public and private sector decision policies and implementation, underlined by the scarcity of analyses of aquaculture governance institutions, are part of the reason for this. The evidence we have aggregated indicates that the relative scarcity of commercially successful coastal IMTA undertakings is not so much an intrinsic feature of the IMTA approach but is likely to have been generated by missing or inappropriate governance structures and procedures in the coastal realm. Full article