The interactions between different species in an ecosystem, such as predation and herbivory, are crucial for maintaining the ecosystem’s functioning, including pest control and nutrient cycling. Unfortunately, human activities are increasingly affecting these trophic relationships, contributing to the current decline in biodiversity, particularly due to urbanization and climate change. The intensity of trophic interactions is also affected by latitudinal gradients, which may be further impacted by urbanization, such as the urban island heat effect. This study aimed to investigate the hypothesis that the impact of human pressure on trophic interactions varies across different latitudes. To test this hypothesis, we selected 18 study sites at two latitudes (i.e., ~53°N and ~50°N) with varying human population density. We used artificial caterpillars placed on European beech branches to assess bird predation and took standardized pictures of the leaves to estimate insect herbivory. Remote sensing techniques were used to estimate human pressure. We found that the intensity of both bird predation and insect herbivory varied in response to human pressure, with opposite trends observed depending on the latitude. At the upper latitude, bird predation increased with human impact, while the opposite was observed at the lower latitude. All types of herbivory in both latitudes increased with urbanization. Moreover, at lower latitudes, species may face a disadvantage due to the urban heat island effect, as they tend to be relatively sensitive to temperature changes. Conversely, at higher latitudes, some species may benefit from a softer winter. Overall, this study highlights the complex and dynamic nature of trophic relationships in the face of human-driven changes to ecosystems. It also emphasizes the importance of considering both human pressure and latitudinal gradients when assessing the ecological consequences of future climate change scenarios, particularly in urban environments.
Monitoring is a prerequisite for evidence-based wildlife management, yet conventional monitoring approaches are often ineffective for species occurring at low densities. However, some species such as large mammals are often observed by lay people and this information can be leveraged through citizen science monitoring schemes. Assessing the quantity, quality, and potential biases of such data sources is crucial before making inferences at scale. For Eurasian moose (Alces alces), a species currently reoccurring in north-eastern Germany in low numbers, we compared three different citizen science tools: a mail/email report system, a smartphone application, and a webpage. Among these monitoring tools, the mail/email report system yielded the greatest number of moose reports in absolute and in standardized (corrected for time effort) terms. The reported moose were predominantly identified as single, adult, male individuals, and reports occurred mostly during late summer. Overlaying citizen science data with independently generated habitat suitability and connectivity maps showed that members of the public detected moose in suitable habitats but not necessarily in movement corridors. Also, moose detections were often recorded near roads, suggestive of spatial bias in sampling effort. Our results suggest that citizen science-based data collection can be facilitated by brief, intuitive digital reporting systems. However, inference from the resulting data can be limited due to unquantified and possibly biased sampling effort. To overcome these challenges, we offer specific recommendations such as engaging outdoor enthusiasts in suitable moose habitats, for improving quantity, quality and analysis of citizen science-based data for making robust inferences about wildlife populations.
1. Grassy ecosystems cover ~40% of the global land surface and are an integral component of the global carbon cycle. Grass litter decomposes via a combination of ultraviolet radiation degradation (which returns carbon to the atmosphere rapidly) and biological decomposition (a slower carbon pathway). As such, decomposition and carbon storage in grasslands may vary with climate and exposure to solar radiation. We investigated rates of grass litter decomposition in Australian temperate grasslands along a climate gradient to uncouple the relative importance of UV radiation and climate on decomposition. 2. Litterbags containing two common native grass species were deployed at six grassland sites across a precipitation gradient (380-890 mm) in south-eastern Australia. Bags were retrieved over 39 weeks to measure mass loss from decomposition. We used shade treatments to partition UV degradation from biological decomposition. 3. The shade treatment consistently reduced the rate of decomposition relative to full-sun treatments at all sites; there was no significant difference in the effect size of the shade treatment among sites. The rate of decomposition was positively correlated with rainfall midway through the experiment, but there were no significant differences in total decomposition among sites after 39 weeks. In general, the shape of decomposition curves was more linear than has typically been observed in global decomposition studies. 4. Synthesis: We found that UV exposure was a strong contributor to litter decomposition in temperate Australian grasslands. This effect was not influenced by climatic variables and may be related to a period of photopriming prior to further biotic decomposition. This study highlights the importance of litter composition and UV exposure in our understanding of how decomposition patterns contribute to global carbon cycling.
The molluscan feeding structure is the radula, a chitinous membrane with teeth, which are highly adapted to the food and the substrate. In Polyplacophora and Patellogastropoda, the handling of hard ingesta can be facilitated by high content of chemical compounds containing Fe or Si in the tooth cusps. Other taxa, however, possess teeth that are less mineralized, even though animals have to avoid structural failure or high wear during feeding as well. Here, we investigated the gastropod Gastropteron rubrum, feeding on hard Foraminifera, diatoms and Porifera. Tooth morphologies and wear were documented by scanning electron microscopy and their mechanical properties were tested by nanoindentation. We determined, that gradients of hard- and stiffness run along each tooth, decreasing from cusp to basis. We also found, that inner lateral teeth are harder and stiffer than the outer ones. These findings allowed us to propose hypotheses about the radula-ingesta interaction. In search for the origins of the gradients, teeth were visualized using confocal laser scanning microscopy, to determine the degree of tanning, and analyzed with energy-dispersive X-ray spectroscopy, to test the elemental composition. We found that the mechanical gradients probably have their origin in the degree of tanning, as the teeth did not contain high proportions of metals or other minerals. However, in the tooth surfaces, which interact with the ingesta, high Si and Ca content was determined, which is likely an adaptation to reduce wear.
C4 is one of three known photosynthetic processes of carbon fixation in flowering plants. It evolved independently more than 61 times in multiple angiosperm lineages and consists of a series of anatomical and biochemical modifications to the ancestral C3 pathway increasing plant productivity under warm and light-rich conditions. The C4 lineages of eudicots belong to seven orders and 15 families, are phylogenetically less clustered than those of monocots, and entail an enormous structural and ecological diversity. Eudicot C4 lineages likely evolved the C4 syndrome along different evolutionary paths. Therefore, a better understanding of this diversity is key to understanding the evolution of this complex trait as a whole. Compiling 1,207 recognized C4 eudicots species described in the literature and presenting trait data among these species, we identify global centres of species richness and of high phylogenetic diversity. Furthermore, we discuss climatic preferences in the context of plant functional traits. We identify two hotspots of C4 eudicot diversity: arid regions of Mexico/Southern United States and Australia, where several C4 eudicot lineages diversified independently. Further eudicot C4 hotspots with many different families and genera represented are in South Africa, West Africa, Patagonia, Central Asia and the Mediterranean. In general, C4 eudicots were abundant in deserts and xeric shrublands, tropical and subtropical grasslands, savannas and shrublands. We found C4 eudicots to occur in areas with less annual precipitation than C4 grasses which can be explained by frequently associated adaptations to drought stress such as among others succulence and salt tolerance. We conclude that in most eudicot lineages C4 evolved in ancestrally drought adapted clades and enabled these to further spread in these habitats and colonise even drier areas.
Biological invasions are recognized as one of the factors causing biodiversity loss. Incomplete reproductive isolation with a closely related species can result in hybridization when a non-native species is introduced into a new habitat. Management of hybrids is essential for biodiversity conservation; however, the distinction between the two species becomes a challenge in cases of hybrids with similar characteristics to native species. Although image recognition technology can be a powerful tool for identifying hybrids, studies have yet to utilize deep learning approaches. Hence, this study aimed to identify hybrids between native Japanese giant salamanders (Andrias japonicus) and non-native Chinese giant salamanders (Andrias davidianus) using EfficientNet and smartphone images. We used smartphone images of 11 native individuals (with 5 training and 6 test images) and 20 hybrid individuals (with 5 training and 15 test images). In our experimental environment, an AI model constructed with efficientNet-V2 showed 100% accuracy in identifying hybrids. In addition, highlighting the regions that influenced the AI model’s predictions using Grad-CAM revealed that salamander head spots are responsible for correctly classifying native and hybrid species. The results of this study revealed that our approach is one of the methods that enable the identification of hybrids, which was previously considered difficult without identification by the experts. Furthermore, since this study achieved high-performance identification using smartphone images, it is expected to be applied to a wide range of low-cost identification using citizen science.
As climate changes, understanding the genetic basis of local adaptation in plants becomes an ever more pressing issue. Combining Genotype-Environment Association (GEA) with Genotype-Phenotype Association (GPA) analysis has an exciting potential to uncover the genetic basis of environmental responses. We use these approaches to identify genetic variants linked to local adaptation to drought in Pinus ponderosa. Over 4 million SNPs were identified using 223 individuals from across the Sierra Nevada of California. We found 1458 associated with five largely uncorrelated climate variables, with the largest number (1151) associated with April 1st snowpack. We also conducted a greenhouse study with various drought-tolerance traits measured in seedlings grown in control and drought treatments. 817 SNPs were associated with control-condition trait values, while 1154 were associated with responsiveness of these traits to drought. While no individual SNPs were associated with both the environmental variables and the measured traits, several annotated genes were associated with both, particularly those involved in cell wall formation, biotic and abiotic stress responses, and ubiquitination. However, the functions of many of the associated genes have not yet been determined due to the lack of gene annotation information for conifers. Future studies are needed to assess the developmental roles and ecological significance of these unknown genes.
Information on freshwater mussel behavior in the sediment is scarce in the Neotropics, especially in the Amazon. Laboratory experiments were used to measure the responses of the mussel Castalia ambigua in relation to combinations of two different morphotypes (Morphotype I with an elongated shell and Morphotype II with a rounded shell) and three different densities (4, 8 and 16 mussels). Horizontal movements (cm) were calculated by summing changes in the position of each specimen and the shell exposure at the sediment-water interface was obtained by measuring (mm) the exposed part of the shell. Castalia ambigua presents different patterns of shell exposure and horizontal movements linked with shell shape and density. Castalia ambigua Morphotype I remained less exposed with 4 mussels. In contrast, this morphotype was more exposed and tended to aggregate in treatments with 8 and 16 mussels, similar to observations of Morphotype II at all densities. Morphotype II is mainly found in low hydrodynamic energy habitats, suggesting that patches with high densities may stabilize the substrate around the shells of Morphotype I, which is associated with high hydrodynamic energy habitats. We suggest that these patterns may be associated with intrinsic factors of the species, such as reproduction and feeding. Moreover, additional studies using other mussel species belonging to the families Hyriidae and Mycetopodidae are important, since the behavior of these mussels in the sediment may provide useful information on their functional roles in river ecosystems.
A better understanding of the impact of habitat loss on population density can be achieved by evaluating effects of both, parameters within remnant habitat patches and parameters of the landscape surrounding those patches. The integration of predictors at the patch and landscape level is scarce in animal ecological studies, especially for reptiles. In this study, a patch-landscape approach was applied to evaluate the combined effects of within patch habitat quality, patch geometry and landscape configuration and composition on the density of remnant populations of the eastern green lizard, Lacerta viridis, in a highly modified landscape in Bulgaria. Landscape composition variables (proportion of different land covers) were measured at different spatial scales surrounding patches. Single scale models were built to evaluate combined effects of all predictors on density, when including all landscape composition variables at a specific spatial scale. Multiscale models were applied to analyze combined effects when including landscape composition variables at the scale of their strongest effect (scale of effect, SoE). Results showed that the SoE of proportion of cropland and urban areas was small (50 m), while for proportion of habitat was large (1.5 Km). The overall effect of habitat loss was better explained by the multiscale model. Population density increased with patch area and decreased with patch shape irregularity and with the proportion of three land cover types surrounding patches -cropland, urban areas and habitat. Combining patch and landscape parameters is important to identify ecological processes that occur simultaneously at different spatial levels and landscape scales, and which would imply the application of multiscale approaches for the protection of wild animal populations. Results are contrasted with what is known about occupancy patterns of the species in the same region, and approaches to integrate both, occupancy and density, in the field design of animal ecological studies are suggested.
The purpose of inter-animal communication is to allow signals released by the animal to be perceived by others. Scent marking, with its characteristics of specificity and delay, is thought to be the primary mode of communication in giant pandas (Ailuropoda melanoleuca). The “signal detection theory” predicts that animals choose the substrate and location of their scent marks so that the signals released are transmitted more widely and remain longer. As an energetically marginal species, the cost of generating and marking chemical signals is costly for pandas, so they are predicted to make trade-offs in scent marking. However, existing studies do not account for the selective preferences of pandas for marking, as they are only explained by the density of marks at a certain location. Our study wanted to investigate whether the marking behavior of pandas is indeed consistent with signal detection theory. For the first time, we propose to use fecal counts to reflect the intensity of habitat use by pandas, combined with mark counts to determine the selective preference for marking. Our findings show that the scent marking behavior of pandas is consistent with signal detection theory, and that they go out of their way to ensure that their marks are detected. The results of the study will help us to further develop the conservation of pandas and their habitats.
Sharks, rays and chimaera form the clade Chondrichthyes, an ancient group of morphologically and ecologically diverse vertebrates that has played an important role in our understanding of gnathostome evolution. Increasingly studies have are seeking to investigate evolutionary processes operating within the chondrichthyan crown group, with the broad aim of understanding the driving forces behind the vast phenotypic diversity observed amongst its constituent taxa. Genetic, morphological and behavioural studies have all contributed to our understanding of phenotypic evolution yet are typically considered in isolation in the context of Chondrichthyes. I argue that integrating these core fields of organismal biology is vital if we are to understand the evolutionary processes operating in contemporary chondrichthyan taxa, and how such processes have contributed to past phenotypic evolution. In light of the global extinction crisis facing this clade, this understanding is crucial if we are to successfully conserve rapidly declining chondrichthyan populations.
The biogeography research of orchids through species distribution models (SDMs), a vital tool in the biogeography field, is critical to understanding the fundamental geographic distribution patterns and identifying conservation priorities. The correspondence between species occurrence and environmental information is crucial to the model’s performance. However, ecological preferences unique to different orchid species, such as their life forms, are often overlooked during the modeling process. This oversight can introduce bias and increase model uncertainty. Additionally, human activities, as an important potential predictor, have not been quantified in any orchid SDMs. Taking the Hengduan Mountains as an example, we preprocessed all orchid species’ occurrences based on physiological characteristics. Choosing five spatial factors related to human activities to quantify the interference and enter into models as HI factor. Using different modeling methods (GLM, MaxEnt, and RF) and evaluation indices (AUC, TSS, and Kappa), diverse modeling strategies have been constructed in the study. A double-ranking method has been adopted to select the critical orchid distribution regions. The results showed that classification models based on physiological characteristics significantly improved the model’s accuracy while adding the HI factor had the same effect but the absence of enough significance. Suitability maps indicated that highly heterogeneous mountainous areas were vital for the distribution of orchids in the Hengduan Mountains. Different distribution patterns and critical regions existed between various orchid life forms geographically - terrestrial orchids were dominant in the mountain, and mycoherterophical orchids were primarily located in the north, more influenced by vegetation and temperature. Critical regions of epiphytic orchids were in the south due to a greater dependence on precipitation and temperature. These studies are informative for understanding the orchids’ geographic distribution patterns in the Hengduan Mountains, promoting conservation, and providing references for similar research beyond orchids.
Changing climate and growing human impacts are resulting in globally rising temperatures and the widespread loss of habitats. How species will adapt to these changes is not well understood. The Northern Goshawk (Accipiter gentilis) can be found across the Holarctic but is coming under more intense pressure in many places. Studies of recent populations in Finland and Denmark have shown a marked decline in body size of Northern Goshawks over the past century. Here we investigate long-term changes to Norwegian populations of Northern Goshawk by including material from the Middle Ages and Viking Age. We measured 240 skeletons of modern Northern Goshawks from Norway, Sweden, Denmark and Finland, and 89 Medieval Goshawk bones. Our results show that Norwegian and Swedish female Goshawks have decreased in size over the past century, whilst males showed little decline. Medieval female Goshawks were larger than contemporary females. The Viking Age specimens showed little difference to modern populations but appeared smaller than specimens from the Medieval period. A decline in forest habitats and a concomitant shift towards smaller prey likely drove a shift to smaller body size in Northern Goshawks. Our study shows that significant body size changes in birds can occur over relatively short time spans in response to environmental factors, and that these effects can sometimes differ between sexes.
Eucalyptus snout beetles (Curculionidae: Gonipterus scutellatus complex), native to mainland Australia and Tasmania, defoliate Eucalyptus trees and are considered important pests. Since the 19th century, species of the G. scutellatus complex have been introduced to other continents. Here, we document the presence of Eucalyptus snout beetles in Ecuador and use ecological niche models to analyze their potential distribution in South America. Phylogenetic analyses of DNA sequences unambiguously demonstrated that the Ecuadorian specimens belong to the species G. platensis, which has low genetic diversity compared with other species in the complex. Ecological niche models revealed several areas of high to intermediate climatic suitability for the pest in South America, even in countries where it has not been registered, like Peru and Bolivia. Accurate identification of species in the Gonipterus scutellatus complex and understanding of their potential distribution are essential tools for improved management and prevention tactics.
Urbanization and the expansion of human activities foster radical ecosystem changes with cascading effects also involving host-pathogen interactions. Urban pollinator insects face several stressors related to landscape and local scale features such as green habitat loss, fragmentation, and availability reduction of floral resources with unpredictable effects on parasite transmission. Furthermore, beekeeping may contribute to the spread of parasites to wild pollinators by increasing the number of parasite hosts. Here we used DNA-based diagnostics tools to evaluate how the occurrence of parasites, namely microsporidians (Nosema spp.), trypanosomatids (Crithidia spp.) and neogregarines (Apicystis bombi), is shaped by the above-mentioned stressors in two bumblebee species (i.e, Bombus terrestris and B. pascuorum). Infection rates of the two species were different and generally higher in B. terrestris. Moreover, they showed different responses towards the same ecological variables, possibly due to differences in body size and foraging habits supposed to affect their susceptibility to parasite infection. The probability of infection was found to be reduced in B. pascuorum by green habitat fragmentation, while increased along with floral resource availability. Unexpectedly, B. terrestris had a lower parasite richness nearby apiaries probably because parasites are prone to be transmitted among the most abundant species. Our finding supports the need to design proper conservation measures based on species-specific knowledge, as suggested by the variation in the parasite occurrence of the two species. Moreover, conservation policies aiming at safeguarding pollinators through flower planting should consider the indirect effects of these measures for parasite transmission together with pollinator biodiversity issues.
Monitoring the effect of ecosystem restoration can be difficult and time consuming. Autonomous sensors, such as acoustic recorders, can aid monitoring across long time scales. This project successfully developed, tested and implemented call recognisers for eight species of frog in the Murray-Darling Basin. Recognisers for all but one species performed well and substantially better than many species recognisers reported in the literature. We achieved this through a comprehensive development phase, which carefully considered and refined the representativeness of training data, as well as the construction (amplitude cut-off) and the similarity thresholds (score cut-offs) of each call template used. Recogniser performance was high for almost all species examined. Recognisers for C. signifera, L. fletcherii, L. dumerilii, L. peronii, and C. parinsignifera all performed well, with most templates having ROC values (the proportion of true positive and true negatives) over 0.7, and some much higher. Recognisers for L. peronii, L. fletcherii and L. dumerilii performed particularly well in the training dataset, which allowed for responses to environmental watering events, a restoration activity, to be clearly observed. While slightly more involved than building recognisers using commercial packages, the workflows ensure that a high quality recogniser can be built and the performance fine-tuned using multiple parameters. Using the same framework, recognisers can be improved in future iterations. We believe that multi-species recognisers are a highly effective and precise way to detect the effects of ecosystem restoration.
Bird diversity has declined as native birds have avoided using the green desert after the Smooth Cordgrass Spartina alterniflora invaded coastal China. After many years of coexistence, a few passerine birds began to enter and use Smooth Cordgrass, but only birds of nonspecialised habitat. In this study, we first found that a native reed-specific bird, the Parrotbill Calamornis heudei, flocked and sang in a Smooth Cordgrass habitat in the whole overwintering period near Sheyang Port in Yancheng, Jiangsu Province. This phenomenon indicates that native obligate birds may be forced to adapt to exotic Smooth Cordgrass habitats after long-term coexistence; obviously, the distribution, feeding and reproduction of birds would be affected. Is this an ecological trap? Which may lead to unknown ecological consequences. We suggest that more research attention should be given to this process occurring along the Chinese coast.