Habitat fragmentation can increase the chance of population bottlenecks and inbreeding, and may ultimately lead to reduced fitness and local extinction. Notelaea lloydii is a native olive species endemic to Australia and listed as vulnerable due to its restricted distribution. A recent molecular systematics study has revealed there might be some geographic structuring among the N. lloydii populations. Therefore, we undertook a genome wide Single Nucleotide Polymorphism (SNP) analysis to determine levels and patterns of genetic diversity, inbreeding and gene flow within and among N. lloydii populations in south-eastern Queensland (SE-QLD). Furthermore, as the reproductive phase of a plant’s life history has a profound influence on genetic diversity, life history reproductive traits were also studied. Our SNP analysis revealed low genetic diversity, inbreeding and significant genetic structuring even among proximate populations. Results of a flower and fruit bagging experiment in two consecutive seasons revealed that N. lloydii produced many flowers but only a few fruits survived to maturity. There were no differences in bagged and un-bagged flowering and fruiting rates and therefore, we conclude that the high fruit abortion rate was probably due to inbreeding depression and/or suboptimal conditions, rather than pollinator availability and insect attack. Overall, results of this study indicate that the populations of N. lloydii are small, inbred and genetically isolated and represent unique management units that require local conservation management due to ongoing threats associated with urbanisation.
Several theoretical models have been proposed as the underlying mechanisms behind occupancy frequency distribution (OFD) patterns. For instance, the metapopulation dynamic model predicts bimodal OFD pattern indicating the dominance of dispersal processes in structuring the assemblages, while the niche-based model predicts unimodal right-skewed OFD pattern, and thus assemblages are driven mostly by niche processes. However, it is well known that the observed OFD pattern reflects the interplay of several other factors (e.g., habitat heterogeneity, species specificity, sampling protocol parameters). It follows that the individual contribution of each factor to the OFD pattern is rather complicated to explore. Our main objective was to examine the role of the spatial extent of the sampling and the dispersal strategies of species in shaping OFD pattern. For this, we collected samples of stream insect assemblages inhabiting near-natural streams in the Pannon Ecoregion. We formed groups of species representing contrasting dispersal strategies (referred to as dispersal groups). Applying a computer program algorithm, we produced samples from different levels of a stream habitat hierarchy (reach, subbasin, basin, and regional) representing different spatial sample extents. We found that with increasing spatial extent, the OFD pattern changed from bimodal to unimodal for two dispersal groups. Insect groups with contrasting dispersal strategies differed in OFD patterns at reach, subbasin and basin levels. Dispersal groups also differed considering the change in OFD patterns with increasing spatial extent. Our results reflected the underlying changes in the niche and dispersal processes that structure assemblages with increasing spatial extent. We also concluded that the stream insect dispersal strategy influenced the relative role of dispersal and niche processes with increasing spatial extent. Based on our results, we could define spatial extents and dispersal strategies within which different metacommunity models (dispersal and niche processes) could be applied.
Distyly, a floral dimorphism that promotes outcrossing, is controlled by a hemizygous genomic region known as the S-locus. Disruptions of genes within the S-locus are responsible for the loss of distyly and the emergence of homostyly, a floral monomorphism that favors selfing. Using whole genome resequencing data of distylous and homostylous individuals from populations of Primula vulgaris and leveraging high-quality reference genomes of Primula we tested, for the first time, predictions about the evolutionary consequences of transitions to selfing on S-locus genes. Our results confirm the presence of previously reported homostyle-specific, loss-of-function mutations in the exons of the S-locus gene CYPᵀ, while also revealing a previously undetected structural rearrangement in CYPᵀ associated with the shift to homostyly. Additionally, we discovered that the promoter region of CYPᵀ in distylous and homostylous individuals is identical, suggesting that down-regulation of CYPᵀ via mutations in its promoter region is not a cause of shift to homostyly. Furthermore, we found that hemizygosity leads to reduced genetic diversity and less efficient purifying selection in S-locus genes compared to genes outside the S-locus, and that the shift to homostyly further lowers genetic diversity, as expected for mating-system shifts. Finally, we tested, for the first time, long-standing theoretical models of changes in S-locus genotypes during early stages of the transition to homostyly, supporting the assumption that two (diploid) copies of the S-locus might reduce homostyle viability.
Fire is increasingly driving loss and degradation of tropical habitats, but factors influencing biodiversity responses to fire are inadequately understood. We conduct a pan-tropical analysis of systematically collated data – 5257 observations of 1705 plant species (trees and shrubs, forbs, graminoids and climbers) in burnt and unburnt plots from 28 studies. We use model averaging of mixed effect models assessing how plant species richness and turnover (comparing burnt and unburnt communities) vary with time since fire, fire type, protected area status and biome type. More long-term studies are needed, but our analyses highlight three key findings. First, prescribed and non-prescribed burns have contrasting impacts on plant communities, the direction of which depends on focal life form and biome. Forb richness, for example, increases following non-prescribed (but not prescribed) burns in savannahs and flooded grasslands, but in moist broadleaved forest forb richness increases strongly following prescribed (but not non-prescribed) burns. Second, protected areas mitigate fire impacts on plant communities. Species richness of trees/shrubs increased (by ~50%) following fires in non-protected sites but tended to remain similar in protected sites. Similarly, ten years after a fire event graminoid community composition had recovered fully to resemble non-burnt communities in protected areas, but remained highly divergent in unprotected sites. Finally, this persistence in divergence of community composition following fire events occurs across a number of life forms. Composition of tree/shrub communities remained divergent from unburnt communities ten years after a fire, and composition of forb communities only returned to those of unburnt sites after ten years. Fire intervals are already less than ten years in some tropical locations, and future climate and land use change are predicted to further shorten these intervals. Plant communities across much of the tropics are thus likely to change substantially in response increased exposure to fire.
Honey bees play a vital role in providing essential ecosystem services and contributing to global agriculture. However, the potential effect of climate change on honey bee distribution is still not well understood. This study aims to identify the most influential bioclimatic and environmental variables, assess their impact on honey bee distribution, and predict future distribution. An ensemble modelling approach using the BIOMOD2 package in R was employed to develop three models, i.e., a climate-only model, an environment-only model, and a combined climate and environment model. The climate-only model focused on the bioclimatic factors: radiation of the wettest and driest quarters, and temperature seasonality. By utilizing bioclimatic data from 1990 to 2009, combined with observed honey bee presence and pseudo absence data, this model predicted honey bee distribution for two future time spans: 2020-2039 and 2060-2079. The climate-only model exhibited a True Skill Statistic (TSS) value of 0.85, underscoring the pivotal role of radiation and temperature seasonality in shaping honey bee distribution. The environment-only model incorporated environmental variables: proximity to regional ecosystems (floral resources), foliage projective cover, and elevation. This model demonstrated strong predictive performance, with a TSS of 0.88, emphasizing the significance of environmental variables in determining habitat suitability for honey bees. Remarkably, the combined model had a higher TSS of 0.96, indicating that the combination of climate and environmental variables enhances the model’s performance. Predictions for the 2060-2079 period revealed a concerning trend of 100% transition of highly suitable land into moderately (0.54%), marginally (17.56%) or not suitable areas (81.9%) for honey bees. These results emphasize the critical need for targeted conservation efforts and the implementation of policies aimed at safeguarding honey bees and the vital apiary industry.
Climate change is altering the distribution and abundance of marine species, especially in Arctic and sub-Arctic regions. In the eastern Bering Sea, home of the world’s largest run of sockeye salmon (Oncorhynchus nerka), juvenile sockeye salmon abundance has increased and their migration path shifted north with warming, 2002-2018. For these sockeye salmon, we quantify environmental and biological covariate effects within spatio-temporal species distribution models. Spatio-temporally, with respect to juvenile sockeye salmon densities: 1) sea surface temperature had a nonlinear effect, 2) Calanus, a minor prey item, and age-0 pollock (Gadus chalcogrammus), a major prey item during warm years, had no significant effect, and 3) juvenile pink salmon (Oncorhynchus gorbuscha) had a positive linear effect on juvenile sockeye salmon densities. Temporally, juvenile sockeye salmon abundance was positively correlated with sea surface temperature, age-0 pollock abundances, and juvenile pink salmon abundance. Changes in population dynamics of sockeye salmon in response to environmental have potential implications for projecting specific future food securities and management of fisheries in Arctic waters.
The existence of adult sexual dimorphism is typically explained as a consequence of sexual selection, yet coevolutionary drivers of sexual dimorphism frequently remain untested. Here, I investigate the role of sexual dimorphism in host-parasite interactions of the brood parasitic diederik cuckoo, Chrysococcyx caprius. Female diederik cuckoos are more cryptic in appearance and pose a threat to the clutch, while male diederik cuckoos are conspicuous and not a direct threat. Specifically, I examine whether sexual dimorphism in diederik cuckoos provokes threat-level sensitive responses in Southern red bishop, Euplectes orix, hosts. I use experimentally simulated nest intrusions to test whether hosts have the capacity to differentially (i) detect, and/or (ii) discriminate between, male and female diederik cuckoos, relative to controls. Overall, I found no evidence that diederik cuckoos differ in detectability, since both sexes are comparable to controls in the probability and speed of host detection. Furthermore, neither male nor female hosts discriminate between sexually dimorphic diederik cuckoos when engaging in frontline nest defences. However, hosts that witnessed a male diederik cuckoo during the trial were more than twice as likely to reject odd eggs compared to those that saw a control. Moreover, hosts were more likely to reject experimental eggs when exposed to a male compared to a female diederik cuckoo: the reverse of a beneficial threat-level sensitive response. While the cryptic appearance of female diederik cuckoos does not differentially avoid detection by hosts, it does appear to provide the benefit of anonymity given the egg rejection costs of male-like appearance in the nest vicinity. These findings have implications for the evolution and maintenance of sexual dimorphism across the Cuculidae, and highlight the value of testing assumptions about the ecological drivers of sexual dimorphism.
Taxus baccata is a relic declining species, especially at the southern margins of its natural distribution, such as the Mediterranean and Irano-Turanian biogeographic regions. On the Island of Sardinia, it is still present in many mountain sites. This study identified 232 locations where yews grow. The species is indifferent to substrates, but prefers moist sites with northern aspects, and has elevation range is 695-1225 m a.s.l. To predict yew’s potential distribution in Sardinia, we collected data from the literature and field observations and applied the Maximum Entropy algorithm (MaxEnt). We used 202 field-based sites and 19 bioclimatic variables to model the potential distribution area under current climatic conditions. Annual precipitation, mean temperature of the warmest month and isothermality were the key drivers for the distribution of T. baccata in Sardinia. In terms of permutation importance, mean diurnal range and precipitation of the warmest quarter were the main environmental variables. The response curves showed that T. baccata prefers annual mean temperatures ranging from 8.65 to 12.55°C and annual mean precipitation from 770 to 1085 mm. Most potential suitable conditions were found in northern and central Sardinia. Using the Global Circulation Model, we also modelled future habitat suitability for T. baccata under two different scenarios, highlighting a substantial reduction of the habitat suitability for the species by the end of this century. This reduction is associated with climate change and poses an increasing concern about the future of the species and the priority habitat described in many parts of Sardinia.
1. Temperature is essential for the survival and development of eggs. Some anurans have evolved and developed foam nesting traits, with thermal insulation considered to be among their functions. Foam nesting frogs tend to exhibit reproductive plasticity. For example, they oviposit on both trees and the ground. How such plasticity affects foam nest function is of major relevance and is likely related to the adaptation of foam nesting frogs. However, this has not been well studied. 2. In this study, we studied the interaction between foam nest site, foam nest function, and egg fate using the Japanese green tree frog, Zhangixalus arboreus, and analysed how nest site differences (arboreal or terrestrial) affect the thermal function of foam nests. 3. We compared the thermal functions of foam nests between arboreal and terrestrial oviposition sites of Z. arboreus. We artificially replaced half of the arboreal nests to terrestrial environments and recorded temperature in and outside of the experimental terrestrial nest and original arboreal nests. We also examined egg survival and hatching rate for all the nests. 4. The results indicated superior heat insulation in terrestrial nests, with warmer temperatures inside than outside the nests, especially at night, which led to a high egg survival rate. Therefore, terrestrial ovipositing should be valid under cold weather conditions. This may be related to the evolutionary history of oviposition site plasticity of this genus, which originally had an arboreal oviposition trait but evolved into terrestrial site use owing to global cooling. 5. Our novel insights into the evolution and adaptivity of foam nesting and oviposition site use in Z. arboreus make a significant contribution to animal ecology.
The increasing spread of marine non-indigenous species (NIS) due to the growth in global shipping traffic is causing widespread concern for the ecological and economic impacts of marine bioinvasions. Risk management authorities need tools to identify pathways and source regions of priority concern in order to better target efforts for preventing NIS introduction. The probability of a successful NIS introduction is affected by the probability that a marine species entrained in a transport vector will survive the voyage between origin and destination locations, and establish an independently reproducing population at the destination. Three important risk factors are voyage duration, range of environmental conditions encountered during transit, and environmental similarity between origin and destination. In this study, we aimed for a globally comprehensive approach of assembling quantifications of source-destination risk factors from every potential origin to every potential destination. To derive estimates of voyage-related marine biosecurity risk, we used computer-simulated vessel paths between pairs of ecoprovinces in the Marine Ecoregions Of the World biogeographic classification system. We used the physical length of each path to calculate voyage duration risk, and the cross-latitudinal extent of the path to calculate voyage path risk. Environmental similarity risk was based on comparing annual average sea surface temperature and salinity within each ecoprovince to those of other ecoprovinces. We derived three separate sets of risk quantifications, one each for voyage duration, voyage path, and environmental similarity. Our quantifications can be applied to studies that require source-destination risk estimates. They can be used separately or combined, depending on the importance of the types of source-destination risks that might be relevant to particular scientific or risk management questions or applications.
Ecological stoichiometry is an important approach to understand the nutrient cycling and balance through the leaf-litter-soil system of Mongolian pine among different stand origins in desert regions. To reveal the variations in Mongolian pine carbon (C), nitrogen (N), and phosphorus (P) stoichiometry and stoichiometric homeostasis among different stand origins, we measured C, N, and P concentrations of leaves, litter, and soil, and analyzed the nutrient resorption efficiencies of leaves in differently aged plantations and natural forests from semi-arid and dry sub-humid regions. The results showed that (a) the stand origin had a significant effect on the C-N-P stoichiometry, and also significantly affected leaf N and P reabsorption efficiencies. Leaf N/P ratios indicated that Mongolian pine was co-limited by N and P in the NF, HB and HQ, and was mainly limited by P in MU. (2) With increasing stand age, C concentrations in the leaf-litter-soil system initially increased and then decreased, the N and P concentrations and reabsorption efficiencies in the leaf-litter-soil system were gradually increased. Overall, stand age had a significant effect on N concentrations, C/N and C/P ratios in the leaf-litter-soil system. (3) The C and N elements between the leaf-litter-soil system had a strong coupling relationship, and the P element between litter-soil had a strong coupling relationship. In addition, plantations exhibited greater N/P homeostasis than natural forests, and N/P exhibited greater homeostasis than N and P alone, which may be a nutrient utilization strategy for forests to alleviate N or P limitation. (4) Environmental factors have a significant influence on C-N-P stoichiometry in the leaf-litter-soil system, the most important soil properties and meteorological factors being soil water content and precipitation, respectively. These results will be essential to provide guidance for plantation restoration and management in desert regions.
Plant reproductive ecology is one of the research hotspots in ecology. With the increasing attention paid to the conservation of plant diversity, the research on reproductive characteristics and flowering biological characteristics of more species has attracted more attention. However, plant reproduction is affected by multiple interacting factors such as pollen limitation and resource availability. Vitex negundo var. heterophylla (Franch.) Rehder (Lamiaceae) is a significant species for water and soil conservation. Previous studies have revealed its mating system by the biological characteristics of flowering and SSR markers, but its reproductive strategies remain to be further studied. We evaluated reproductive success through artificial pollination to explore the reproductive characteristics of V. negundo var. heterophylla for the first time. From the results of fruit set, there is a mixed mating system dominated by outcrossing in V. negundo var. heterophylla accompanied by self-compatibility, and it cannot carry out autonomous selfing. Our data shows the pollinator-mediated interaction in the success of reproduction, whereas the effect of anemophily is very weak. And the seed germination rate of inbred line progenies was lower than that of hybrid progenies, which is suspected to be caused by inbreeding depression. The research will provide scientific information for the protection and conservation of V. negundo var. heterophylla from the point of view of reproduction. In sum, the results are necessary to protect animal vectors in the background of insect decline.
The effect of mixing litter on decomposition has received considerable attention in terrestrial and aquatic (but rarely in both) ecosystems, with a striking lack of consensus in the obtained results. We studied the decomposition of a mixture of poplar and alder in three terrestrial:aquatic exposures to determine (1) if the effect of mixing litter on mass loss, associated decomposers and detritivores differs between the stream (fully aquatic exposure) and when litter is exposed to a period of terrestrial exposure prior to immersion and (2) the global effect of the mixture across exposure scenarios. The effect of the mixture was additive on mass loss and synergistic on decomposers and detritivores across exposure scenarios. Within scenarios, mass loss and decomposers showed synergistic effects only in the fully aquatic exposure, detritivores showed synergistic effects only when the period of terrestrial was shorter than the period of aquatic exposure, and when the period of terrestrial was equal to the period of aquatic exposure the effect of the mixture was additive on mass loss, decomposers, and detritivores. The species-specific effects also differed among exposure scenarios. Alder affected poplar only when there was a period of terrestrial exposure, with increased sporulation rates and fungal richness in exposure 25:75, and increased mass loss in exposure 50:50. Poplar affected alder only under fully aquatic exposure, with increased mass loss. In conclusion, the synergistic effects of the mixture changed with a period of terrestrial exposure prior to immersion. These results provide a cross-boundary perspective on the effect of mixing litter, showing a legacy effect of exposure to terrestrial decomposition on the fate of plant litter in aquatic ecosystems and highlighting the importance of assessing the effect of mixing litter on the associated biota and not only on mass loss.
Aim Identification of taxonomically cryptic species is essential for the effective conservation of biodiversity. Freshwater-limited organisms tend to be genetically isolated by drainage boundaries, and thus may be expected to show substantial cryptic phylogenetic and taxonomic diversity. By comparison, populations of diadromous taxa, that migrate between freshwater and marine environments, are expected to show less genetic differentiation. Here we test for cryptic diversity in Australasian populations (both diadromous and non-diadromous) of two widespread Southern Hemisphere fish species. Location Throughout both their Australian ranges (including Lord Howe Island) and localities in New Zealand (including the Subantarctic Islands and Chatham Island). Taxon Galaxias brevipinnis and Galaxias maculatus. Methods mtDNA and nuclear markers were used to assess the presence of cryptic species and to determine if differences in species ecology could influence the degree of cryptic diversity. Results Both mtDNA and nuclear markers reveal putative cryptic species within these taxa. The substantial diversity detected within G. brevipinnis may be explained by its strong climbing ability which allows it to form isolated inland populations. In island populations, G. brevipinnis similarly show deeper genetic divergence than those of G. maculatus, which may be explained by the greater abundance of G. maculatus larvae in the sea allowing more ongoing dispersal. Main conclusions Our study highlights that even widespread, ‘high-dispersal’ species can harbour substantial cryptic diversity and therefore warrant increased taxonomic and conservation attention.
Insect herbivores, such as lepidopteran larvae, often have close evolutionary relationships with their host plants, with which they may be locked in an evolutionary arms race. Larval grouping behaviour may be one behavioural adaptation that improves host plant feeding, but aggregation also comes with costs, such as higher competition and limited resource access. Here, we use the Heliconiini butterfly tribe to explore the impact of host plant traits on the evolution of larval gregariousness. Heliconiini almost exclusively utilise species from the Passifloraceae as larval host plants. Passifloraceae display incredible diversity of form, leaf shape and a range of anti-herbivore defences, suggesting they are locked in an arms race with Heliconiini larvae. By analysing larval social behaviour as both a binary (solitary or gregarious) and categorical (increasing larval group size) trait, we revisit the multiple origins of larval gregariousness across Heliconiini. We investigate whether host habitat, leaf defences and leaf size are important drivers of, or constraints on, larval gregariousness. Whereas our data do not reveal links between larval gregariousness and the host plant traits included in this study, we do find an interaction between larval host specialisation and behaviour, revealing gregarious larvae to be more likely to feed on a narrower range of host plant species than solitary larvae. We also find evidence that this increased specialisation typically precedes the evolutionary transition to gregarious behaviour. The comparatively greater host specialisation of gregarious larvae suggests that there are specific morphological and/or ecological features of their host plants that favour this behaviour.
Poyang Lake is an essential natural wetland in the Yangtze River basin and plays a vital role in maintaining the ecosystem function and ecological security in the middle and lower reaches of the Yangtze River. However, the relative importance and spatial heterogeneity of the impacts of human activities and land use changes on ecological security needs to be further explored. Here, we analyzed the habitat quality level around Poyang Lake in 2022 and explored the factors of habitat quality change from a geographical perspective. The land use structure changes around the Poyang Lake basin from 2000 to 2022 were quantitatively analyzed, and then the relative importance and spatial heterogeneity of each factor on ecological security changes were investigated using geographic probes. The results show that (1) The worst quality habitat (0–0.1) consists mainly of construction land (1624.9 km2) with an area of 1634.64 km2; (2) Construction land continues to increase with the most significant change, and the dynamic land use attitude is 0.47. Grassland and mudflats have the greatest decrease. The increase in cultivated land in different periods is mainly due to the shift of water surface and forest land; (3) Wetland land use change drivers are more influenced by the interaction of socioeconomic factors. The explanatory degrees of the interaction between population density and total year-end population and population density and administrative area are greater than 0.84. The data are greater than the explanatory degrees of every single factor, indicating that the land use change is mainly coupled with population density, total year-end population, and administrative area. These results reveal that human activities influence the degradation of wetlands around the Poyang Lake area. This study has significant reference value for coordinating human–land relationships in Poyang Lake, optimizing land management policy, and improving the sustainable development of cities
The subgenus Aschizomys belongs to the genus Alticola (Central Asian mountain vole) and consists of two species: Alticola macrotis and Alticola lemminus. Phylogenetic relationships within the subgenus Aschizomys remain obscure due to limited sampling, an insufficient number of molecular markers used in phylogenetic studies, and paraphyly observed on mitochondrial trees. In this work, to infer reliable phylogenetic relationships and evaluate putative scenarios of ancient hybridization within the subgenus, we applied double-digest restriction site–associated DNA paired-end (quaddRAD) sequencing to 20 DNA samples (20 individuals), including five species of the genus Alticola, and dated the divergence of cytochrome b (cytb) lineages within Aschizomys using a “second calibration” approach. We showed monophyly of the two species on the basis of thousands of nuclear loci and demonstrated traces of introgression also in the nuclear genome. Observed paraphyly in cytb could be explained by an introgression event rather than incomplete lineage sorting. This explanation was confirmed by an analysis of the cytb divergence time. Overall, our results support the hypothesis of extensive migration of the Aschizomys species during the Late Pleistocene, with this migration leading to population divergence and introgression. We expect our article to become a starting point for a series of rigorous studies on the population history of the genus Alticola as a whole.
1. Cyanobacterial blooms in freshwater sources are a global concern, and gaining insight into their causes is crucial for effective resource management and control. 2. In this study, we present a computational framework for the causal analysis of cyanobacterial harmful algal blooms (cyanoHABs) in Lake Kinneret. Our framework integrates Convergence Cross Mapping (CCM) and Extended CCM (ECCM) causal networks with Bayesian Network (BN) models. 3. The constructed CCM - ECCM causal networks and BN models unveil significant interactions among factors influencing cyanoHAB formation. These interactions have been validated by domain experts and supported by evidence from peer-reviewed publications. Our findings suggest that M. flos-aquae levels are influenced not only by community structure but also by nitrate, nitrite, ammonium, phosphate, oxygen, and temperature levels in the weeks preceding bloom occurrences. 4. We have demonstrated a non-parametric computational framework for the causal analysis of a multivariate ecosystem. Our framework offers a more comprehensive understanding of the underlying mechanisms driving M. flos-aquae in Lake Kinneret. It captures complex interactions and provides an explainable prediction model. By considering causal relationships, temporal dynamics, and joint probabilities of environmental factors, the proposed framework enhances our understanding of cyanoHABs in Lake Kinneret.