Populations Of Species Research Articles

Characterization of Firmiana danxiaensis plastomes and comparative analysis of Firmiana: insight into its phylogeny and evolution

BackgroundFirmiana danxiaensis is a critically endangered and ecologically important tree currently only found in four locations in Danxia or Karst habitats in northern Guangdong Province, China. The specialized habitat preference makes it an ideal model species for study of adaptive evolution. Meanwhile, the phylogenetic relationships of F. danxiaensis in four locations under two landforms are unclear. Therefore, we sequenced its complete chloroplast (cp.) genomes and conducted comprehensive interspecific and intrageneric plastome studies.ResultsThe F. danxiaensis plastomes in four locations showed a typical quadripartite and circular structure that ranged from 160,832 to 161,206 bp in size, with 112 unique genes encoded. Comparative genomics showed that the plastomes of F. danxiaensis were relatively conserved with high similarity of genome organization, gene number, GC content and SSRs. While the genomes revealed higher biased codon preferences in Karst habitat than those in Danxia habitats. Eighteen and 11 divergent hotpots were identified at interspecific and intrageneric levels for species identification and further phylogenetic studies. Seven genes (clpP, accD, ccsA, ndhH, rpl20, rpoC2, and rps4) were under positive selection and may be related to adaptation. Phylogenetic analysis revealed that F. danxiaensis is sister to F. major and F. simplex. However, the interspecific relationships are not consistent with the habitat types.ConclusionsThe characteristics and interspecific relationship of F. danxiaensis plastomes provide new insights into further integration of geographical factors, environmental factors, and genetic variations on the genomic study of F. danxiaensis. Together, our study will contribute to the study of species identification, population genetics, and conservation biology of F. danxiaensis.

Gradual Emergence of East African cassava mosaic Cameroon virus in Cassava Farms in Côte d’Ivoire

Cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) are endemic threats to cassava production, causing significant yield losses. They are caused respectively by begomoviruses and ipomoviruses that are transmitted by whiteflies and infected cuttings. This study aimed to monitor and characterize viruses responsible for these diseases in order to fill existing gaps in understanding their epidemiology in Côte d’Ivoire. Field surveys were conducted in 2016, 2017, and 2020, and no CBSD symptoms were observed. However, an increase in CMD incidence was noted from 45.95% in 2016 to 51.37% in 2020, while CMD severity remained moderate over the years with a mean value of 2.29. The number of whiteflies was relatively low and decreased over the years. Molecular diagnostics carried out on cassava leaf samples allowed the detection of East African cassava mosaic Cameroon virus (EACMCMV) that occurs in single as well as in mixed infection with African cassava mosaic virus (ACMV). Single EACMCMV infection, which was detected only in three agroecological zones of eastern Côte d’Ivoire in 2016, spread throughout the country in 2017 and became more widespread in 2020 with a preponderance in central and southern zones, whereas ACMV and EACMCMV coinfection has spread to the entire zones. Phylogenetic analysis of the viral isolates showed that they are closely related to those from Burkina Faso, Ghana, and Nigeria. This changing population of cassava virus species constitutes a serious threat to cassava cultivation. Understanding the evolutionary dynamics of these viruses could help in adopting better disease management strategies to control the disease.

Reciprocal facilitation between ants and small mammals in tidal marshes.

The role of facilitation in shaping natural communities has primarily been studied in the context of plant assemblages, while its relevance for mobile animals remains less understood. Our study investigates whether reciprocal interspecific facilitation may exist between fire ants (Solenopsis richteri) and cavies (Cavia aperea), two mobile animals, in the SW Atlantic coast brackish marshes. Field samples showed a spatial association between ant mounds and cavies, and that ants prefer to use cavy runways for movement within the marsh. Through experiments involving transplanting the dominant plant, cordgrass (Spartina densiflora), and manipulating cavy presence in areas with and without ant mounds, we observed that cavies forage extensively (and defecate more) near ant mounds. The ants actively remove cavy droppings in their mound vicinity. These ant activities and interactions with cavy droppings led to reduced moisture and organic content while increasing nitrate and phosphate levels in marsh sediment. Consequently, this enhanced plant growth, indirectly facilitating the cavies, which preferred consuming vegetation near ant mounds. These cascading indirect effects persisted over time; even four months after cavies left the marshes, transplanted plants near ant mounds remained larger and exhibited more leaf senescence when exposed to cavy herbivory. Therefore, the networks of positive interactions appear to generate simultaneous selection among species (populations), promoting coexistence within the community. Although complex, these reciprocal facilitative effects among mobile animals may be more common than currently believed and should be further studied to gain a better understanding of the underlying mechanisms driving species coexistence in natural communities.

Termite species and functional diversity as determined by vegetation and edaphic characteristics in a savanna ecosystem

BackgroundSavanna ecosystems support a diversity of biota and are influenced by vegetation and edaphic characteristics, shaping resident communities. This study was carried out at Mlawula nature reserve, a protected savanna ecosystem to determine impacts of vegetation and edaphic characteristics on termite species and functional diversity, as well as their activity. Termites were sampled from November 2017 to March 2018 in two habitat types, i.e. encroached and non-encroached by Dichrostachys cinerea over five months.ResultsTwelve genera were collected over the study period, dominated by Microtermes sp. Termite species diversity and populations were significantly between habitat types, with higher numbers and species in non-encroached sites. Four functional groups (FG) were collected from both habitat types, with FGII being the most dominant group in both and no significant differences in FG diversity between the habitat types. Of the vegetational and edaphic variables measured, only canopy cover was significantly different between habitat types and was higher in encroached sites. Intensity and frequency of attack were significantly higher in non-encroached sites, indicating a decline in termite activity in encroached sites.ConclusionsResults indicated that, with the exception of canopy cover, vegetational and edaphic characteristics are not affected by increased woody vegetation invasion within the system assessed. However, due to reduction in termite diversity and activity, increased woody vegetation invasion is a threat to termites and associated ecosystem services they provide. The investigation provided information at both community and ecosystem level for the savanna assessed on the need for insect conservation both within protected areas and surrounding landscapes. Since the study suggested that termite populations and associated activity could be reduced due bush encroachment, monitoring of the impacts of increasing woody plant invasions is essential for insect conservation and maintenance of savanna ecosystem function and heterogeneity.

Cost-effective biodiversity protection through multiuse-conservation landscapes

ContextIntensive land use and exploitation of natural resources are the main direct drivers of biodiversity loss. Transformative changes in land management are called for as conservation and management actions have not been sufficient to support the viability of species populations. It has been proposed that to solve the sufficiency problem one could segregate the landscape into an intensively managed part, and into so-called multiuse-conservation landscapes that aggregate set asides with managed areas for multiple uses.ObjectivesWe describe a scenario analysis where we evaluate the effects and cost-efficiency of transforming the boreal forest from intensively managed production landscapes progressively towards multiuse-conservation landscapes.MethodsWe simulated Finnish boreal forests under various managements and optimized management to produce six scenarios to reveal the ecological, economic, climate and management regime implications of multiuse-conservation landscapes. Ecological effects explored included habitat availability and metacommunity capacity of dead wood dependent species.ResultsIncreasing the area of set aside and multiuse management increased the habitat availability and metacommunity capacity as well as climate benefits but caused economic losses in terms of timber revenues. Pooling the set asides and multiuse management areas together into the same landscapes reduced the economic losses, had negligible added climate benefits and produced mixed biodiversity effects: pooling decreased habitat availability but increased metacommunity capacity across all landscapes.ConclusionsChanging land management and aggregating conservation efforts can be a cost-efficient way to protect biodiversity. Our results suggest biodiversity benefits in landscapes where the set aside and multiuse is aggregated. Careful spatial planning can also alleviate the conflicts between ecological and economic values of land.

Population genetic structure in the critically endangered Crocodylus intermedius (Crocodilia: Crocodylidae): a shift in perspective for conservation actions in Colombia

Abstract Conservation actions for threatened species and populations aim to preserve their genetic diversity and prevent issues such as inbreeding or outbreeding depressions. This perspective has been incorporated into the management plans proposed for the critically endangered Orinoco crocodile (Crocodylus intermedius) in Colombia. A previous study, which used mitochondrial cytochrome b and cytochrome c oxidase subunit I, suggested that the in situ population management of the Orinoco crocodile in Colombia does not face genetic restrictions. In this research, we re-evaluated this proposal by using an expanded sampling and additional molecular markers (microsatellite nuclear DNA and the mitochondrial D-loop) that have successfully identified crucial information at the population level in other crocodilians. Our findings reveal, for the first time, a pattern of population structure consisting of three genetic clusters with geographical correspondence, matching three ecoregions in the Colombian Orinoco basin. This pattern might be a historical and current consequence of the ecological, bioclimatic, and/or geographical features of the ecoregion. Additionally, we examined the correspondence with the genetic clusters of the confiscated individuals that formed part of the initial population (F0) of the Colombian ex situ species population and successfully assigned most of them to one of these clusters. The genetically distinct clusters should be regarded as independent management units for conserving and managing the species in Colombia.

Convergent and environmentally associated chromatic polymorphism in Bryconops Kner, 1858 (Ostariophysi: Characiformes: Iguanodectidae).

Bryconops Kner, 1858, includes two well defined subgenera based on morphological evidence, with each containing at least one species (B. (Bryconops) caudomaculatus and B. (Creatochanes) melanurus) with a very wide distribution, within which regional populations present color variations. To test if phenotypic variation is related to cladogenetic events, we performed tests for phylogenetic independence and determined the strength of convergence for color characters in relation to water type, as the variation between clear, black and white waters is considered to be one of the major driving forces in the evolution of Amazonian fishes. Color characters for fins above the median line of the body were generally found to be independent from phylogeny and the Wheatsheaf test strongly supports convergence of the dorsal fin color between populations of species in the same type of water, with a similar trend suggested for the color of the dorsal lobe of the caudal fin. This means that simple color characters cannot necessarily be relied upon for taxonomic revisions of the genus as local phenotypic variants may represent environmentally determined plasticity or convergent evolution. Further studies are required to determine the validity of these characters.

Ca-dimers, solvent layering, and dominant electrochemically active species in Ca(BH4)2 in THF

Divalent ions (Mg, Ca, and Zn) are being considered as competitive, safe, and earth-abundant alternatives to Li-ion electrochemistry, but present challenges for stable cycling due to undesirable interfacial phenomena. We explore the formation of electroactive species in the electrolyte Ca(BH4)2∣THF using molecular dynamics coupled with a continuum model of bulk and interfacial speciation. Free-energy analysis and unsupervised learning indicate a majority population of neutral Ca dimers and monomers with diverse molecular conformations and an order of magnitude lower concentration of the primary electroactive charged species – the monocation, CaBH4+\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\rm{CaBH}}_{4}^{+}$$\\end{document} – produced via disproportionation of neutral complexes. Dense layering of THF molecules within ~1 nm of the electrode surface strongly modulates local electrolyte species populations. A dramatic increase in monocation population in this interfacial zone is induced at negative bias. We see no evidence for electrochemical activity of fully-solvated Ca2+. The consequences for performance are discussed in light of this molecular-scale insight.

Phylogenetic relationships and genetic differentiation of two Salamandrella species as revealed via COI gene from Northeastern China.

Due to traditional classification methods' limitations, some cryptic species remain undiscovered. To better explore the existence of the Schrenck salamander (Salamandrella tridactyla, a cryptic species of Siberian salamander S. keyserlingii) in China, we conducted a molecular phylogenetic analysis to confirm the taxonomic relationship among Salamandrella species and investigate genetic variation. We used complete sequences of the mitochondrial COI gene from 65 specimens collected across a wide range in Northeastern China. Thirty-five haplotypes were obtained from six populations. They showed medium-high haplotype diversity (Hd) and low nucleotide polymorphism (π). The phylogenetic tree and haplotype network analysis revealed that populations from Greater Khingan Ridge (Huma: HM) and Lesser Khingan Ridge (Tieli: TL) belong to S. keyserlingii, while populations from Changbai Mountain (Shangzhi-zhuziying: SZ, Shangzhi-cuijia: SC, Hailin: HL, and Baishan: BS) belong to S. tridactyla. This indicates the monophyly of Salamandrella and each of the two species. There was a substantial level of genetic differentiation between different species and within populations of the same species. This differentiation was significantly related to geographical distance. At last, the mismatch distribution and neutrality analyses indicated that the TL populations have undergone expansion of history. The study supplements the distributional range of Schrenck salamander. And it provides a theoretical basis for species conservation of Salamandrella species.

Comparative Mitogenome Analyses of Fifteen Ramshorn Snails and Insights into the Phylogeny of Planorbidae (Gastropoda: Hygrophila).

Ramshorn snails from the family Planorbidae are important freshwater snails due to their low trophic level, and some of them act as intermediate hosts for zoonotic trematodes. There are about 250 species from 40 genera of Planorbidae, but only 14 species from 5 genera (Anisus, Biomphalaria, Bulinus, Gyraulus, and Planorbella) have sequenced complete mitochondrial genomes (mitogenomes). In this study, we sequenced and assembled a high-quality mitogenome of a ramshorn snail, Polypylis sp. TS-2018, which represented the first mitogenome of the genus. The mitogenome of Polypylis sp. TS-2018 is 13,749 bp in length, which is shorter than that of most gastropods. It contains 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, and 2 ribosomal RNA (rRNA). We compared mitogenome characteristics, selection pressure, and gene rearrangement among all of the available mitogenomes of ramshorn snails. We found that the nonsynonymous and synonymous substitution rates (Ka/Ks) of most PCGs indicated purifying and negative selection, except for atp8 of Anisus, Biomphalaria, and Gyraulus, which indicated positive selection. We observed that transpositions and reverse transpositions occurred on 10 tRNAs and rrnS, which resulted in six gene arrangement types. We reconstructed the phylogenetic trees using the sequences of PCGs and rRNAs and strongly supported the monophyly of each genus, as well as three tribes in Planorbidae. Both the gene rearrangement and phylogenetic results suggested that Polypylis had a close relationship with Anisus and Gyraulus, while Bulinus was the sister group to all of the other genera. Our results provide useful data for further investigation of species identification, population genetics, and phylogenetics among ramshorn snails.

Predicting animal abundance through local ecological knowledge: An internal validation using consensus analysis

Abstract Given the ongoing environmental degradation from local to global scales, it is fundamental to develop more efficient means of gathering data on species and ecosystems. Local ecological knowledge, in which local communities can consistently provide information on the status of animal species over time, has been shown to be effective. Several studies demonstrate that data gathered using local ecological knowledge (LEK)‐based methods are comparable with data obtained from conventional methods (such as line transects and camera traps). Here, we employ a consensus analysis to validate and evaluate the accuracy of interview data on LEK. Additionally, we investigate the influence of social and bioecological variables on enhancing data quality. We interviewed 323 persons in 19 villages in the Western and Central Amazon to determine the level of consensus on the abundance of hunted and non‐hunted forest species. These villages varied in size, socio‐economic characteristics and in the experience with wildlife of their dwellers. Interviewees estimated the relative abundance of 101 species with a broad spectrum of bioecological characteristics using a four‐point Likert scale. High consensus was found for species population abundance in all sampled villages and for 79.6% of interviewees. The village consensus of all species abundance pooled was negatively correlated with village population size. The consensus level was high regardless of the interviewees' hunting experience. Species that are more frequently hunted or are more apparent had greater consensus values; only two species presented a low consensus level, which are rare and solitary species. We show in our study in the Amazon that information gathered by local peoples, Indigenous as well as non‐Indigenous, can be useful in understanding the status of animal species found within their environment. The high level of cultural consensus we describe likely arises from knowledge sharing and the strong connection between the persons interviewed and the forest. We suggest that consensus analysis can be used to validate LEK‐generated data instead of comparing these types of data with information obtained by conventional methods. Read the free Plain Language Summary for this article on the Journal blog.

Rapid evolution of flower phenology and clonality in restored populations of multiple grassland species

Abstract Restoration of terrestrial ecosystems often requires re‐introduction of plants. In restored sites, the plants often face environments that differ from those of natural populations. This can affect plant traits, reduce performance and impose novel selection pressures. As a response, restored populations might rapidly evolve and adapt to the novel conditions. This may enhance population survival and contribute to restoration success, but has been rarely tested so far. Here, we focused on populations of three grassland species restored 20 years ago (Galium wirtgenii, Inula salicina and Centaurea jacea) by the transfer of green hay, and compared them with donor populations that were the source of the hay. We measured plants both in situ, and in a common garden under control and three stress conditions. In situ, plants in restored sites flowered earlier than plants in donor sites in two out of the three species. In the common garden, plants from the restored populations flowered earlier (in Galium) or showed increased plasticity of clonal propagation in response to clipping (in Inula). Both these traits suggest rapid adaptation to the contrasting mowing regimes in restored in comparison with the donor sites. In Centaurea, we detected no differentiation, neither in situ, nor in the common garden. Synthesis and applications. Grassland plants introduced into degraded habitats within the framework of ecological restoration may quite commonly evolve in response to novel selection pressures at restored sites. This rapid evolution likely increases the plant's adaptation to the new conditions of the restored grassland and thus enhances the likelihood of survival of the population and ultimately restoration success. While most practitioners do not consider evolution to be part of restoration, our finding highlights that restored populations of grassland species can be systems with considerable eco‐evolutionary dynamics.

Structural and socioeconomic features of cities predict migratory bird species richness

Cities are aggregates of human activities where our decisions shape the environment creating heterogeneity across urban centers that can have significant ecological effects on wildlife. Many bird species are found in cities during the breeding season, which implies they find sufficient resources in cities to support them during this energetically costly time. As populations of many migratory bird species are declining, knowledge of how they are affected by urbanization is needed. Yet, we know little about how the species richness of migratory birds varies across different types of cities. Here we ask if cities' structural and socioeconomic features can predict the species richness of migratory birds that generally select different breeding habitats during the breeding season. We used eBird data from census‐designated urban areas in the US to model the relationship between features of cities (housing density, median income, city age, and commuting time), environmental disturbance (measured by the human footprint index) and species richness by fitting generalized linear models to data. We show that commuting time was the most important factor determining species richness across cities and the rest of the city features were weakly associated with species richness. Overall species were responding to city variation in similar ways. While we expected that cities with more disturbance would have lower species richness, our results indicate that some species are able to tolerate even highly disturbed cities and that cities in certain regions may act as a refuge to birds. This knowledge is important for our general understanding of cities as habitat for birds and how migratory birds respond to across‐city variation during the breeding season.

Current and future potential distribution of Culex (Melanoconion) (Diptera: Culicidae) of public health interest in the Neotropics.

Anthropogenic activities are altering ecosystem stability and climate worldwide, which is disturbing and shifting arbovirus vector distributions. Although the overall geographic range of some epidemiologically important species is recognized, the spatiotemporal variation for other species in the context of climate change remains poorly understood. Here we predict the current potential distribution of 9 species of Culex (Melanoconion) based on an ecological niche modeling (ENM) approach and assess spatiotemporal variation in future climate change in the Neotropics. The most important environmental predictors were the mean temperature of the warmest season (27 °C), precipitation during the driest month (50 mm), and precipitation during the warmest season (>200 mm). The best current model for each species was transferred to the future general circulation model IPSL-CM6A-LR, using 2 shared socioeconomic pathway scenarios (ssp1-2.6, ssp5-8.5). Under both scenarios of climatic change, an expansion of suitable areas can be observed followed by a strong reduction for the medium-long future under the worst scenario. The multivariate environmental similarity surface analysis indicated future novel climates outside the current range. However, none of the species would occur in those areas. Even if many challenges remain in improving methods for forecasting species responses to global climate change and arbovirus transmission, ENM has strong potential to be applied to the geographic characterization of these systems. Our study can be used for the monitoring of Culex (Melanoconion) species populations and their associated arboviruses, contributing to develop region-specific public health surveillance programs.

Репродуктивные показатели липы Нащокина (Tilia nasczokinii Stepanov)

Tilia nasczokinii Stepanov (Naszokin’s lime) is endemic to the south of the Krasnoyarsk Territory and is of relict origin. Two of its populations grow in the vicinity of Krasnoyarsk on the left and right banks of the Yenisey River, being a part of pine forests and mixed pine-deciduous herb forests. The total number of the species is about 500 plant units, of which only 43 plants are currently bearing fruit. This research has determined the sizes and qualitative characteristics of T. nasczokinii fruits and seeds. The lime-capsules of T. nasczokinii, for 2 populations in general, have had the length of 5.7 ± 0.026 mm and the width of 5.0 ± ± 0.017 mm. The seeds have had the length of 3.6 ± 0.019 mm and the width of 2.9 ± 0.015 mm. It has been established that the lime-capsules in the left bank population are characterized by an elongated pear-shaped form, while in the right bank population the lime-capsules are spherical and slightly pointed at the top. In terms of the size of lime-capsules and seeds, T. nasczokinii did not differ statistically from the introduced T. cordata, which grows in the plantation under similar environmental conditions. In the left bank population, the masses of lime-capsules (18.3 g/1000 pcs.) and seeds (11.9–12.7 g/1000 pcs.) have turned out to be noticeably less than in the right bank population (lime-capsules – 24.8–29.9 g/1000 pcs., seeds – 16.1–18.0 g/1000 pcs.). In the left bank population, up to 60 % of the lime-capsules have been seedless and up to 43 % of the seeds have been empty. Seed viability has been equal to 17–32 %.In the right bank population, most of the lime-capsules have contained seeds (up to 91 %), and the proportion of empty lime-capsules has been small (up to 18 %). Seed viability has been equal to 66–83 %. Field germination of the seeds has been equal to 9.2 % (for some trees – up to 10.5 %) in the left bank population and 12.2 % (up to 21.1 %) in the right bank population. Despite the low field germination of the seeds in both populations, it is possible to obtain seed planting stock for creating artificial plantings of T. nasczokinii in order to preserve and restore the population of this rare relict species in the south of Central Siberia.

Effect of planting geometry and weed-management practices on yield of scented rice (Oryza sativa) varieties

A field experiment was conducted at the Shaheed Gundadhur College of Agriculture and Research Station, of the Indira Gandhi Krishi Vishwavidhyalaya, Jagdalpur, Chhattisgarh during rainy season (Kharif) of 2019, to evaluate the effect of planting geometry and weed-management practices in transplanted scented rice varieties. Treatments consisting combination of 2 varieties, 2 planting geometry and 4 weed management practices were replicated thrice in a split-split plot design. The dominant weeds in transplanted rice were: Ludwigia peploides (Kunth) P.H. Raven., Spilanthes acmella (L.) C.B. Clarke ex Hook. f., Echinochloa colona L., Cyperus difformis L., Cyperus iria L., Commelina benghalensis L. and Fimbristylis miliacea (L.) Vahl. Significantly lowest population of different weed species, and the highest grain and straw yields, and harvest index were found with variety, ‘Tarunbhog Selection 1’ while the maximum test weight was observed with ‘Dubraj Selection 1’. The planting geometry of 20 cm × 20 cm recorded the minimum weed population and the highest yield and benefit cost ratio. Application of pyrazosulfuron ethyl 10% WP @ 20 g/ha at 3 Days after transplanting (DAT) + 1 hand weeding (HW) at 25 DAT was found the most effective for broad-spectrum weed control and increased the rice grain yield. The highest net returns and benefit cost were recorded with the pre-emergence application of pyrazosulfuron ethyl 10 % WP @ 20 g/ha.

Variation in RNA interference sensitivity in the southern pine beetle, Dendroctonus frontalis (Coleoptera: Curculionidae)

Abstract Intraspecific genetic variation underpins many evolutionary processes and phenomena. For species considered pests, the dynamics of how genetic variation is distributed geographically take on a greater importance, because they can impact pest-management strategies directly. This is particularly true when management strategies are genetic in nature, such as population manipulation via RNA interference (RNAi; a naturally occurring antiviral response that disrupts translation of messenger RNAs into proteins to silence genes). Using RNAi for gene silencing is highly species specific; however, the efficacy of this approach in geographically distinct populations of widespread pest species has not been evaluated comprehensively. Here, we present a preliminary study evaluating differential susceptibility of geographically disparate populations of southern pine beetle, Dendroctonus frontalis, to RNAi. Although the efficacy of RNAi has been demonstrated in localized populations, D. frontalis has a broad distribution across North and Central America and is expanding its range owing to climate change. We observe differences in response between and within geographically distinct populations from its core range and recently expanded range. Our findings have broad implications for the use of RNAi as a management tool in widely distributed species and highlight the need for a deeper understanding of intraspecific genetic variation in this species and others.

Landscape and farm environmental structure determinants of small mammal assemblages in agroecosystems of central Argentina

Abstract Natural processes and patterns are altered by human activity at different spatial and temporal scales, affecting species assemblages and population traits, modifying mechanisms or regulating dynamics at different scales. However, little is known about the influence of landscape structure on small mammal assemblages and populations on farms. Thus, in this work, we aimed to study the effect of landscape and environmental characteristics at the farm scale on the assemblage and populations of native and introduced small mammals in pig and dairy farms located in Buenos Aires province, Argentina. Our results showed that farms in contexts of higher environmental diversity at the landscape scale have higher species richness. Our results also showed that variations in assemblage composition were associated with the quantity of water body surfaces, cattle food, small mammal refugia, and impervious surfaces at the farm scale—and with woodland, grassland, and natural vegetation cover at the landscape scale. The abundance of commensal murids was higher on farms near towns, with higher vegetation cover at the farm scale and/or in landscape contexts with fewer crops. The abundance of Akodon azarae was higher on farms with a lower amount of cattle food at the farm scale and crop patches in the landscape. The abundance of Didelphis albiventris was higher during spring on farms with a low proportion of bare ground, while that of Lutreolina crassicaudata was higher on farms with high vegetation cover and a lower number of water body surfaces. These results show the relevance of multiscale determinants in the development of ecologically based management strategies to control pest small mammals.

How does vector diversity influence the transmission efficiency of yellow dwarf virus? Perspectives from a review

AbstractCereals are some of the most important global crops that contribute directly and indirectly to the production of food for human consumption. Cereal aphids can cause significant damage to wheat, barley and oats, particularly via the transmission of plant viruses that cause devastating plant diseases, such as yellow dwarf disease. High levels of yellow dwarf disease can result in yield losses of around 20%, rising to 80% if infection is severe. Yellow dwarf disease is caused by multiple viruses, including viruses within the families Tombusviridae and Solemoviridae. These include yellow dwarf virus species within the genus Luteovirus (Barley yellow dwarf virus) and Polerovirus (Cereal yellow dwarf virus, Wheat yellow dwarf virus, Maize yellow dwarf virus). Some yellow dwarf virus species are primarily vectored by one aphid species whereas others can be transmitted by multiple vectors. Biological diversity within a given vector species (e.g., genotype, biotype) can influence virus transmission efficiency. However, it is unclear what biological factors drive this variation within a given vector species. Understanding how biological variation in vector populations influences virus transmission efficiency can help to identify biological traits that underpin successful transmission in competent vector populations. Here, the available literature on yellow dwarf virus transmission efficiency is synthesized and significant variation in yellow dwarf virus transmission efficiency is detected between different populations for several vector species. Three biological mechanisms that potentially underpin this variation are proposed.

The unpredictability of scyphozoan jellyfish blooms

The study of jellyfish blooms has gained attention in the recent decades because of the importance of forecasting and anticipating them and avoiding their interference with human activities. However, after thirty years of scientific effort (monitoring systems, empirical laboratory and field studies, modeling, etc.), the occurrence of blooms remains unpredictable, and their consequences unavoidable. Climate change, eutrophication, overfishing, coastal construction, and species translocation have been suggested as stressors that increase them, but robust evidence to support these claims is limited. The widespread belief that jellyfish blooms are “increasing in number” has been challenged in recent years. Among the gelatinous zooplankton, the bloom forming species are concentrated in the class Scyphozoa, and the number of species with at least one recorded bloom has increased during the last decade. The analyses of long-term time series show seasonality in the dynamic of each blooming jellyfish species population, but the blooms vary in intensity and there are years of an unexplained absence of jellyfish. In this review, we focus on the current state of knowledge, uncertainties and gaps in the critical points that can strongly influence the intensity of the bloom or even lead to the absence of the medusa population. These points include ephyrae, planulae and scyphistoma natural, predatory or fishing mortality, the molecular pathway of strobilation, benthic population dynamics, planula settlement and ephyra to medusa transition success. Some of these points account for certain empirical laboratory evidence under controlled conditions, and are difficult to be studied on the field, but the different sources of non-typically recorded variability need to be addressed to improve our understanding of jellyfish population dynamics.