An estimate of the area of occupancy and population size of Brachycephalus tridactylus (Anura: Brachycephalidae) to reassess its conservation status, with a proposal for conservation measures

Background We are experiencing a global crisis in conservation, which has led to the prioritization of targets, such as nations, regions, and animal groups, which are necessary while resources are disputed. Brazil is a priority not only because of its megadiversity, high rates of endemism, and frequent descriptions of new species but also because of its high levels of deforestation. Among the species groups prioritized for conservation is the anurans (Amphibia: Anura), the population of which is severely declining. One group of anurans is the genus Brachycephalus, which includes 37 endemic species in the Brazilian Atlantic Rainforest. Some of these species have highly restricted distributions (<100 ha). Thirty new species have been described since 2000, and 55.3% of all species are threatened with extinction. Brachycephalus tridactylus was only recently described and remains restricted to its type locality. Because of its reduced geographical distribution (0.41 km2), it has been proposed to be considered as Vulnerable. The objective of this study is to reevaluate the conservation status of Brachycephalus tridactylus and propose conservation measures. Methods We searched for new populations during 2016–2020, evaluated in loco impacts and potential impacts on the species’ population, and performed an analysis of the density of this population and estimated its size. International Union for Conservation of Nature (IUCN) criteria were used to assess the conservation status of the species. Results We recorded the species in seven new localities (from 715–1,140 m above sea level) in the state of São Paulo up to 33 km from the type locality of the species (in state of Paraná). We estimated the area of occupancy as 148.44 km2, densities as one calling male per 4.05 m2 and 130.00 m2, and a total population size of 4,429,722 adult individuals. Based on our finding, we proposed three lines of management: (1) formation of fire brigades, (2) management of residents’ mules in the conservation unit and surrounding areas, and (3) management of degraded areas. We recommend changing the species’ conservation status from Vulnerable to Endangered because of its fragmented distribution and decline in the area of occupancy and in the quality of its habitat. Our results have expanded the species previous geographic distribution and delimited areas without previous records. Our estimates of population density and size are in accordance with those verified for congeners. The conservation of this species benefits the environments and other species that inhabit them, being, therefore, strategic for receiving conservation actions that will spread throughout the ecosystem.

Aedes koreicus, a vector on the rise: pan-European genetic patterns, mitochondrial and draft genome sequencing

BackgroundThe mosquito Aedes koreicus (Edwards, 1917) is a recent invader on the European continent that was introduced to several new places since its first detection in 2008. Compared to other exotic Aedes mosquitoes with public health significance that invaded Europe during the last decades, this species’ biology, behavior, and dispersal patterns were poorly investigated to date.Methodology/Principal FindingsTo understand the species’ population relationships and dispersal patterns within Europe, a fragment of the COI gene was sequenced from 130 mosquitoes, collected from five countries where the species has been introduced and/or established. Oxford Nanopore and Illumina sequencing techniques were combined to generate the first complete nuclear and mitochondrial genomic sequences of Ae. koreicus from the European region. The complete genome of Ae. koreicus is 879 Mb. COI haplotype analyses identified five major groups (altogether 31 different haplotypes) and revealed a large-scale dispersal pattern between European Ae. koreicus populations. Continuous admixture of populations from Belgium, Italy, and Hungary was highlighted, additionally, haplotype diversity and clustering clearly indicate a separation of German sequences from other populations, pointing to an independent introduction of Ae. koreicus to Europe. Finally, a genetic expansion signal was identified, suggesting the species might be present in more locations than currently detected.Conclusions/SignificanceOur results highlight the importance of genetic research of invasive mosquitoes to understand general dispersal patterns, reveal main dispersal routes and form the baseline of future mitigation actions. The first complete genomic sequence also provides a significant leap in the general understanding of this species, opening the possibility for future genome-related studies, such as the detection of ‘Single Nucleotide Polymorphism’ markers. Considering its public health importance, it is crucial to further investigate the species’ population genetic dynamic, including a larger sampling and additional genomic markers.Author SummaryIn the present context of globalization and changing environment, the rapid spread of Invasive Mosquito Species (IMS) across Europe represents a serious public health threat because some species are competent vectors for several pathogens. A better knowledge of the IMS population relationships, demographic trends, and dispersal patterns can help the relevant authorities mitigating further spread. Aedes koreicus is an IMS that invaded the continent and has been expanding its geographic range over the last decade. In the present study, one of the most popular DNA marker (COI) was used to investigate the pan-European haplotype diversity and phylogenetic relatedness within and between Ae. koreicus populations. Also, the first complete mitochondrial genome and draft nuclear genome of Ae. koreicus were generated using combined high-throughput sequencing techniques (Oxford Nanopore, Illumina). This provides a significant leap in the general understanding of this species and opens the possibility for future genomic studies.

Does an Invasive Bivalve Outperform Its Native Congener in a Heat Wave Scenario? A Laboratory Study Case with Ruditapes decussatus and R. philippinarum

Global warming and the subsequent increase in the frequency of temperature anomalies are expected to affect marine and estuarine species’ population dynamics, latitudinal distribution, and fitness, allowing non-native opportunistic species to invade and thrive in new geographical areas. Bivalves represent a significant percentage of the benthic biomass in marine ecosystems worldwide, often with commercial interest, while mediating fundamental ecological processes. To understand how these temperature anomalies contribute to the success (or not) of biological invasions, two closely related species, the native Ruditapes decussatus and the introduced R. philippinarum, were exposed to a simulated heat wave. Organisms of both species were exposed to mean summer temperature (~18 °C) for 6 days, followed by 6 days of simulated heat wave conditions (~22 °C). Both species were analysed for key ecological processes such as bioturbation and nutrient generation—which are significant proxies for benthic function and habitat quality—and subcellular biomarkers—oxidative stress and damage, and energetic metabolism. Results showed subcellular responses to heat waves. However, such responses were not expressed at the addressed ecological levels. The subcellular responses to the heat wave in the invasive R. philippinarum pinpoint less damage and higher cellular energy allocation to cope with thermal stress, which may further improve its fitness and thus invasiveness behaviour.

Water vole (Arvicola amphibious) as an object of long-term biomonitoring in a floodplain area (Western Siberia, Russia)

The paper is devoted to the dynamics of the water vole population in the conditions of total deforestation of valley forests and their subsequent restoration. We analyzed the relative population of small mammals in the typical biotopes in the Tom River basin (Western Siberia) on the border of the forest-steppe and taiga zones. From 1978 to 2019, 1,139 water voles Arvicola amphibius (Linnaeus, 1758) (synonym of A. terrestris) were caught with 50-meter trapping grooves; for 788 individuals we assessed the condition of non-metric features (phenes) of the skull. It was found that changes in the population level are non-cyclical, while against the background of a generally low occurrence of the species in the region, the population level increased tenfold in some years. It was shown that such episodic population surges can significantly impact the structure of the community of small mammals. In the valley of the Tom River, the water vole prefers inhabit wet meadows and ecotone areas between the meadow and the dark coniferous taiga forest. During the years of population surges, the water vole intensely occupies new nesting sites due to the dispersal activity of young animals but at the same time retains the original biotopic preferences. Dispersal of the species takes place in waterlogged wetlands. Most of the animals caught during the peak of their numbers were young animals of late broods born from overwintered individuals. The conducted phenetic analysis revealed the heterogeneity of young animals during the population surge, which allowed us to assume the participation of several populations in the formation of the peak. In the final surge year, the surge was characterized by an extremely low percentage of participation in the breeding of young females and the appearance of a large number of weakened animals, which led to crisis in the species population and the disappearance of the water vole from the captures. The research shows that one cannot predict the success of this process at the current stage; therefore, after flooding, it is necessary to continue monitoring.

Context matters: the landscape matrix determines the population genetic structure of temperate forest herbs across Europe

Context Plant populations in agricultural landscapes are mostly fragmented and their functional connectivity often depends on seed and pollen dispersal by animals. However, little is known about how the interactions of seed and pollen dispersers with the agricultural matrix translate into gene flow among plant populations. Objectives We aimed to identify effects of the landscape structure on the genetic diversity within, and the genetic differentiation among, spatially isolated populations of three temperate forest herbs. We asked, whether different arable crops have different effects, and whether the orientation of linear landscape elements relative to the gene dispersal direction matters. Methods We analysed the species’ population genetic structures in seven agricultural landscapes across temperate Europe using microsatellite markers. These were modelled as a function of landscape composition and configuration, which we quantified in buffer zones around, and in rectangular landscape strips between, plant populations. Results Landscape effects were diverse and often contrasting between species, reflecting their association with different pollen- or seed dispersal vectors. Differentiating crop types rather than lumping them together yielded higher proportions of explained variation. Some linear landscape elements had both a channelling and hampering effect on gene flow, depending on their orientation. Conclusions Landscape structure is a more important determinant of the species’ population genetic structure than habitat loss and fragmentation per se. Landscape planning with the aim to enhance the functional connectivity among spatially isolated plant populations should consider that even species of the same ecological guild might show distinct responses to the landscape structure.

Ecological theory of mutualism: Robust patterns of stability and thresholds in two-species population models

Mutualisms are ubiquitous in nature, provide important ecosystem services, and involve many species of interest for conservation. Theoretical progress on the population dynamics of mutualistic interactions, however, comparatively lagged behind that of trophic and competitive interactions, leading to the impression that ecologists still lack a generalized framework to investigate the population dynamics of mutualisms. Yet, over the last 90 years, abundant theoretical work has accumulated, ranging from abstract to detailed. Here, we review and synthesize historical models of two-species mutualisms. We find that population dynamics of mutualisms are qualitatively robust across derivations, including levels of detail, types of benefit, and inspiring systems. Specifically, mutualisms tend to exhibit stable coexistence at high density and destabilizing thresholds at low density. These dynamics emerge when benefits of mutualism saturate, whether due to intrinsic or extrinsic density-dependence in intraspecific processes, interspecific processes, or both. We distinguish between thresholds resulting from Allee effects, low partner density, and high partner density, and their mathematical and conceptual causes. Our synthesis suggests that there exists a robust population dynamic theory of mutualism that can make general predictions.

Bacterial diversity and viral discovery in the invasive Argentine ant (Linepithema humile)

<p>Invasive species can lead to major economic and ecological issues. For this reason, biological controls are being developed in order to help with invasive species population management. Pathogenic bacteria and viruses offer good biological control opportunities as both micro-organisms have played a role in natural population declines. However, beneficial bacteria and viruses associated with the targeted invasive species may interfere with biological controls, by protecting their hosts from infections. Previous knowledge on both pathogenic and beneficial bacteria and viruses present in invasive species may then support the development of an active and efficient biological control. The Argentine ant, Linepithema humile, is a South American invasive ant species that has successfully spread over five continents. The ants were introduced to New Zealand after a complex invasion path, from Argentina their home range to Europe, then to Australia and finally to New Zealand. In their new environments, invasive Argentine ants affect species diversity and can cause agricultural losses. In the absence of any biological controls, the Argentine ant population is controlled by chemical sprays and poison baits. Management of these invasive ants in New Zealand is estimated to cost NZ$ 60 million a year. The Argentine ant population in New Zealand was reported to have unexpectedly declined. It was hypothesised that pathogens were the cause of this population collapse. In this study, bacteria and viruses present in the invasive ants were investigated using 454 sequencing and Illumina sequencing for future developments of possible biological controls for the Argentine ants, and a better understanding of the observed population decline in New Zealand. Bacterial diversity present in Argentine ants either declined or diminished along the invasion pathway. At the same time, the invasive ants maintained a core of nine bacteria genera, including Lactobacillus and Gluconobacter, two bacterial genera with members known for their beneficial associations with honey bees. The presence of these core bacteria may have participated in the success of Argentine ants in their new environments. In the laboratory, the use of ampicillin and gentamicin antibiotics on the ants increased bacterial diversity present in the ants. Furthermore, ampicillin, kanamycin and spectinomycin antibiotic treatments increased ant survival but did not affect the ant fitness or intra-species aggressiveness. Only spectinomycin treated ants presented a higher level of inter-species aggressiveness. Bacterial diversity may play an important role in the ant health and at length population dynamics. Finally, Argentine ants are the hosts of two viruses: the Deformed wing virus (DWV) involved in colony collapse disorder in honey bees, and Linepithema humile virus 1 (LHUV-1), a new virus related to DWV. Both viruses actively replicate within the ants, indicating a possible reservoir role of the ants. However, the effects of the viruses on the ants are not yet known. Further viral infection in the laboratory under different stress conditions and / or antibiotic treatment will give an insight in the role played by these viruses in the observed population collapse of Argentine ants in New Zealand. LHUV-1 may offer a possibility in the development of the first biological control for Argentine ants, depending on its specificity and its effects. This dissertation provides a first insight in the core bacteria as well as potential harmful viruses present in Argentine ants. These bacteria and viruses may play a role in the ant population dynamics. Invasive species may co-introduce harmful pathogens with them, and participate to the spread of local ones. The pathogens may affect both invasive ants and native species population dynamics.</p>

Bacterial diversity and viral discovery in the invasive Argentine ant (Linepithema humile)

<p>Invasive species can lead to major economic and ecological issues. For this reason, biological controls are being developed in order to help with invasive species population management. Pathogenic bacteria and viruses offer good biological control opportunities as both micro-organisms have played a role in natural population declines. However, beneficial bacteria and viruses associated with the targeted invasive species may interfere with biological controls, by protecting their hosts from infections. Previous knowledge on both pathogenic and beneficial bacteria and viruses present in invasive species may then support the development of an active and efficient biological control. The Argentine ant, Linepithema humile, is a South American invasive ant species that has successfully spread over five continents. The ants were introduced to New Zealand after a complex invasion path, from Argentina their home range to Europe, then to Australia and finally to New Zealand. In their new environments, invasive Argentine ants affect species diversity and can cause agricultural losses. In the absence of any biological controls, the Argentine ant population is controlled by chemical sprays and poison baits. Management of these invasive ants in New Zealand is estimated to cost NZ$ 60 million a year. The Argentine ant population in New Zealand was reported to have unexpectedly declined. It was hypothesised that pathogens were the cause of this population collapse. In this study, bacteria and viruses present in the invasive ants were investigated using 454 sequencing and Illumina sequencing for future developments of possible biological controls for the Argentine ants, and a better understanding of the observed population decline in New Zealand. Bacterial diversity present in Argentine ants either declined or diminished along the invasion pathway. At the same time, the invasive ants maintained a core of nine bacteria genera, including Lactobacillus and Gluconobacter, two bacterial genera with members known for their beneficial associations with honey bees. The presence of these core bacteria may have participated in the success of Argentine ants in their new environments. In the laboratory, the use of ampicillin and gentamicin antibiotics on the ants increased bacterial diversity present in the ants. Furthermore, ampicillin, kanamycin and spectinomycin antibiotic treatments increased ant survival but did not affect the ant fitness or intra-species aggressiveness. Only spectinomycin treated ants presented a higher level of inter-species aggressiveness. Bacterial diversity may play an important role in the ant health and at length population dynamics. Finally, Argentine ants are the hosts of two viruses: the Deformed wing virus (DWV) involved in colony collapse disorder in honey bees, and Linepithema humile virus 1 (LHUV-1), a new virus related to DWV. Both viruses actively replicate within the ants, indicating a possible reservoir role of the ants. However, the effects of the viruses on the ants are not yet known. Further viral infection in the laboratory under different stress conditions and / or antibiotic treatment will give an insight in the role played by these viruses in the observed population collapse of Argentine ants in New Zealand. LHUV-1 may offer a possibility in the development of the first biological control for Argentine ants, depending on its specificity and its effects. This dissertation provides a first insight in the core bacteria as well as potential harmful viruses present in Argentine ants. These bacteria and viruses may play a role in the ant population dynamics. Invasive species may co-introduce harmful pathogens with them, and participate to the spread of local ones. The pathogens may affect both invasive ants and native species population dynamics.</p>

Policy recommendations for environmental conservation in the Chindwin River Basin

The Chindwin Basin is facing habitat loss and species population decline driven by economic development activities combined with the impacts of climate change. Given the interdependency of livelihoods and biodiversity in this part of Myanmar, this brief explores ideas for enhancing community-based conservation in the Chindwin River Basin.