On Ypsolopha micromoths (Lepidoptera, Ypsolophidae) associated with Adesmia shrubs (Fabaceae) in the arid western slope of the central Andes

Ypsolopha Latreille, 1796 (Lepidoptera, Ypsolophidae) is a genus comprised mostly of Holarctic micromoth species with a fairly broad range of larval hosts (e.g. Aceraceae, Rosaceae, and Fagaceae). The only previous record of herbivory on a representative of the South American genus Adesmia DC. (Fabaceae) was based on the discovery of Ypsolophamoltenii Vargas, 2018 larvae feeding on Adesmiaverrucosa Meyen in the Andes of northern Chile. Further surveys revealed Adesmiaatacamensis Phil. as another host for Y.moltenii, and Adesmiaspinosissima Meyen as the single host of Ypsolopha sp. The genetic distance between DNA barcodes of the two micromoth species was 7.9-8.1% (K2P). These results suggest narrow host ranges for Adesmia-feeding Ypsolopha and highlight the need to further explore the taxonomic diversity of these micromoths in other South American environments.

Nutritional strategy underlying plant specialization to gypsum soils

Gypsum soils are amongst the most widespread extreme substrates of the world, occurring in 112 countries. This type of hypercalcic substrate has a suite of extreme physical and chemical properties that make it stressful for plant establishment and growth. Extreme chemical properties include low plant-available nitrogen and phosphorus and high plant-available sulphur and calcium, which impose strong nutritional imbalances on plants. In spite of these edaphic barriers, gypsum soils harbour rich endemic floras that have evolved independently on five continents, with highly specialized species. Plants that only grow on gypsum are considered soil specialists, and they have a foliar elemental composition similar to the elemental availability of gypsum soils, with high calcium, sulphur and magnesium accumulation. However, the physiological and ecological role of the unique foliar elemental composition of gypsum specialists remains poorly understood, and it is unknown whether it provides an ecological advantage over other generalist species on gypsum soils. This article reviews available literature on the impact of gypsum soil features on plant life and the mechanisms underlying plant adaptation to gypsum environments. We conclude with a hypothesis on the potential role of the nutritional strategy underlying plant specialization to gypsum soils: Gypsum specialists primarily use SO₄^2- as a counter anion to tolerate high Ca²⁺ concentrations in cells and avoid phosphorus depletion, which is one of the most limiting nutrients in gypsum soils.

Improved statistical models for the relationship between riparian vegetation and river flow in arid environments: Implications for flow management

Riparian vegetation (RV) provides critical ecosystem services but has been degraded worldwide due to river flow change. Quantitative relationships between RV and river flow are essential for understanding RV developments and managing flow to conserve RV. Based on the improved statistical model framework that incorporates previous RV conditions into explanatory variables to estimate later RV conditions, this study quantified the RV-flow relationships on the annual scale in the arid Ejina Delta through regression analysis coupled with the normalized difference vegetation index (NDVI) and hydrological data during 2002-2020. The median of NDVIs over the April-October growing season (SMN) was used to indicate annual vegetation conditions, and annual RV cover was derived using a dynamic SMN threshold (0.077-0.084) based on its better vegetation conditions than surrounding deserts. The water year was determined as September-August based on the defoliation time and lag time of the groundwater response to river flow. The results showed that (1) the RV cover approximately expanded from 1619 to 2914 km^2, and the total SMN of RV cover increased from 3711 to 7880; (2) the spatial pattern of SMN declining away from rivers was well described by an exponential function with two physically meaningful parameters (R² = 0.99); (3) the water-year runoff ranged from 4.0 × 10⁸ to 10.6 × 10⁸ m³ with an increasing trend; and (4) the annual RV condition, including both the total SMN and the spatial pattern of SMN, was well estimated by the multiple linear models incorporating a previous RV condition with a coefficient <1 and the subsequent water-year runoffs (R² = 0.98). The results suggest that previous RV conditions are necessary to improve the rationality and performance of RV-flow relationship models, and in arid environments, annual RV conditions depend on the RV's degradation characteristics under zero flow conditions and the ecological benefit by river flow.

Hydrochemistry, isotope studies and salt formation in saline lakes of arid regions: Extra-Andean Patagonia, Argentina

The most favourable locations for the development of saline lakes are in the rain-shadow of mountain ranges, which provide large areas of precipitation catchment while the base of the basin is under arid climate and exposed to evaporation. These conditions are found in Extra-Andean Patagonia under the rain-shadow generated by the Andean cordillera. There, an endorheic basin with two shallow and saline lakes, Cari Laufquen Chica (CLC) and Cari Laufquen Grande (CLG), was studied with the aim of analysing the factors that condition the hydrochemical processes acting in the formation of evaporites associated with these environments. A monitoring network was installed and five surface and groundwater survey campaigns were carried out at different points in the basin to define groundwater flow and also to extract samples. In situ pH, electrical conductivity and temperature and laboratory physicochemical determinations of major ions and stable isotopes of the water were measured. SEM-EDS and XRD analyses of saline crusts from the edge of the lakes and adjacent sediments were carried out. The obtained results allowed identifying that CLC and CLG saline lakes have different surface water-groundwater configurations. CLC is a flow-through shallow lake, while CLG is a discharge shallow lake. The analysis of the saline precipitates and the chemical facies of the water allows identifying cycles of dissolution, evaporation and precipitation in both saline lakes. However, the different groundwater flow between the two lakes is reflected in their salinity as well as in the evolution and development of saline precipitates. CLC saline lake shows a dissolution-precipitation trend of thenardite and Ca-Mg carbonates, whereas CLG saline lake displays a trend of dissolution-precipitation of halite, thenardite and trona with strong dominance of halite. The present study identifies for the first time the main factors conditioning hydrochemical processes in these saline lakes of extra-Andean Patagonia. Our results indicate that the hydrological configuration with respect to the groundwater flow is the prevailing factor setting the hydrochemical processes that trigger the formation of salt crusts.

Plant functional traits shape growth rate for xerophytic shrubs

Trade-offs exist for xerophytic shrubs between functional traits, involving in water loss and assimilate accumulation, can contribute to its survival and growth rate regulation in arid environments. However, growth analysis based on plant functional traits has been focused on the study of herbs and woody species. It is still unclear how the functional traits of xerophytic shrubs regulate their growth rate. In this study, we selectedeight xerophytic shrubs as samples to analyze the regulation process of the functional traits of shrubs on growth rate. Plants were cultivated for three years, and three harvests (every one year) were carried out. Factors explaining between-species differences in relative growth rate (RGR) varied, depending on whether different ages were considered. The results showed that RGR was positively correlated with net assimilation rate, but there was a significant negative correlation with leaf area ration (LAR), specific leaf area (SLA), and leaf biomass ratio in the age 1. However, in the age 2, RGR showed a significant positive correlation with the morphological traits (i.e., leaf area ration and specific leaf area), but not with physiological traits (i.e., net assimilation rate) and leaf biomass allocation. Our results suggested that the fluctuation of environmental factors affects the regulation path of the plant functional traits on RGR of xerophytic shrubs. However, the analysis of causality model showed that no matter in which age, net assimilation rate and leaf area ration principally drive the variation in RGR among xerophytic shrubs.

A small neighborhood well-organized: seasonal and daily activity patterns of the community of large and mid-sized mammals around waterholes in the Gobi Desert, Mongolia

Background

Animal communities have complex patterns of ecological segregation at different levels according to food resources, habitats, behavior, and activity patterns. Understanding these patterns among the community is essential for the conservation of the whole ecosystem. However, these networks are difficult to study nowadays, due to anthropic disturbances and local extinctions, making it difficult to conclude if segregation patterns are natural or human-induced. We studied ecological segregation in a community of large and mid-sized mammals in the Great Gobi Desert, a remote arid area free from recent extinctions and human disturbances. Activity patterns of 10 sympatric mammal species were monitored around 6 waterholes through camera-trapping over a two-year period, and analyzed them primarily through circular statistics.

Results

Complex patterns of spatial, seasonal, and daily segregation were found. Overlap in seasonal activity was detected in only 3 of the 45 possible pairs of species. Four species used the waterholes all-year-round, while others peaked their activity during different periods. The Bactrian camel showed continuous daily activity, the grey wolf had bimodal activity, and the argali and Siberian ibex were diurnal, while the others had nocturnal peaks during different hours. Daily and spatial overlap were both detected in only 6 of the 45 pairs. Only one species pair (snow leopard and Eurasian lynx) showed an overlap at two levels: seasonal and daily. Climate and moon phase significantly affected the activity of certain species.

Conclusions

Altogether, the results showed complex patterns of ecological segregation at different levels in the use of the key resource in arid environments: waterholes. These results are important for understanding the biology of these species under natural conditions, as well as potential changes in altered ecosystems, and may help to design conservation strategies.

Saline groundwater in the Buffels River catchment, Namaqualand, South Africa: A new look at an old problem

Namaqualand, South Africa, is a global biodiversity hotspot but local populations are affected by challenging economic conditions largely because of poor access to water. In this study groundwater types are characterised and sources of salts and salinisation processes are identified using hydrochemistry and δ¹⁸O, δ²H and ⁸⁷Sr/⁸⁶Sr data. Analysis of δ¹⁸O and δ²H data suggests that evaporation does not play a major role in salinisation of the groundwater. However, major ion chemistry and ⁸⁷Sr/⁸⁶Sr ratios indicate that salts present in the groundwater are linked to dry deposition of marine aerosols and ion-exchange reactions in soils in the alluvial aquifer systems. The hydrochemical variability of the groundwater in the basement aquifer system suggests that there are strong local controls linked to weathering processes in individual basement rock types. The region is also notable for the high density of heuweltjies, biophysical features associated with increased nutrient levels, associated with termite activity. Electromagnetic scanning as well as measurement of water-soluble soil electrical conductivity values on and off heuweltjies, show that heuweltjies are saline with salinity increasing with depth. The level of groundwater salinity correlates with the level of heuweltjie salinity. Precipitation records from the last 150 years provide support for the hypothesis that accumulated salts, and in particular, heuweltjie salts are flushed into the groundwater system during sporadic large volume precipitation events. Thus, heuweltjies and hence termite activity, could potentially represent a previously unrecognized contributor to groundwater salinisation across Namaqualand and in other parts of the world.

Diversity of culturable bacteria isolated from ancestral crops of Arica and Parinacota Region, Atacama Desert

Arica and Parinacota Region is located at the extreme north of the Atacama Desert, where the high levels of salts and boron, lack of rain, high UV radiation, among other conditions, make this zone an extreme environment. Despite these characteristics, in the transversal valleys, different types of crops are cultivated in this region, which are associated to beneficial microorganisms with specific traits that allow plants surviving and developing under extreme conditions. However, there is incomplete information related to these microorganisms. In this work, bacteria associated with ancestral crops were isolated from oregano, alfalfa, maize, potato, and grapevine samples from Belén, Codpa, Molinos, Poconchile and Socoroma localities, representing the first report of these microorganisms in those sites. Bacteria were identified, being γ-Proteobacteria, the most frequent class (~ 74.4%), with members of Pseudomonas genus the most common isolated genus. All bacteria were functionally characterized for plant growth-promoting activities, including siderophores and auxins production, phosphate solubilization, and nitrogen fixation, revealing an extraordinary potential from these microorganisms for agricultural applications under arid and semiarid conditions.

Geochemical and hydrogeological factors influencing high levels of radium contamination in groundwater in arid regions

One of the most challenging environmental issues in arid regions is radionuclide groundwater contamination; typically, radionuclide sources, mobility, and spatial distributions are not well understood. The main objectives of this study are to investigate the groundwater hydrochemistry and identify the factors governing the radium occurrences and mobility. Groundwater samples were collected from shallow unconfined zone and deep confined Saq sandstone aquifer in the Hail area, Saudi Arabia. They were analyzed for major, minor, and trace elements as well as radium isotopes (²²⁶Ra and ²²⁸Ra). The hydrochemical relationships, water facies, spatial distribution, and the factor analysis were integrated to elucidate the governing processes in the system. The hydrochemical facies exhibited four water types characterized by earth alkaline and alkaline elements. Most samples contained sulfates and chlorides. The hydrochemical processes affecting groundwater included the dissolution of certain minerals, mixing between modern and fossil water types, and reverse ion exchange. There are high concentrations of nitrate in the unconfined zone, with low concentrations in areas under confining conditions. High radium concentrations were recorded in the groundwater, and the ²²⁶Ra and ²²⁸Ra activity concentrations of the examined samples were 11% and 98% above the World Health Organization (WHO) guidelines, respectively. The spatial distribution of ²²⁶Ra showed high activity concentration in the shallow zone under prevailing oxidizing conditions. High ²²⁸Ra contamination was identified in the confined zone where the redox potential appears to decrease and the temperature increases result in higher mobility or desorption of the radium ions. In the unconfined zone, the oxidation of Fe⁺² in the groundwater and precipitation of Fe⁺³ in the aquifer pore spaces and co-precipitation with barite can accelerate radium adsorption. The ²²⁸Ra/²²⁶Ra ratio classified the radium groundwater enrichment into three main clusters, namely, those depending on the redox potential values, the primary source distribution, and enrichment in ²²⁶Ra relative to ²²⁸Ra. Five major factors influencing groundwater hydrochemistry were identified using factor analysis. The first factor explained the processes resulting in the dissolution of the silicate minerals and thereby increased the uranium mobility. The second factor encompassed processes leading to a rise in the groundwater salinity. The third factor identified thorium minerals as the source of the ²²⁸Ra. The fourth factor was ascribed to the decrease in radium through sorption processes or co-precipitation with barite. The fifth factor referred to by the uneven distribution of Th and U containing minerals in the aquifer.

Are all patches worth exploring? Foraging desert birds do not rely on environmental indicators of seed abundance at small scales

Background

Consumers should show strong spatial preferences when foraging in environments where food availability is highly heterogeneous and predictable. Postdispersal granivores face this scenario in most arid areas, where soil seed bank abundance and composition associates persistently with vegetation structure at small scales (decimetres to metres). Those environmental features should be exploited as useful pre-harvest information, at least to avoid patches predicted to be poor. However, we did not find the expected spatial association in the algarrobal of the central Monte desert by observing foraging seed-eating birds, a field technique influenced by how much they exploit visited patches. In this work we tested if the first stage of foraging by granivorous birds (patch visit, encounter or exploration) is positively associated with environmental indicators of patch quality by recording the removal of single seeds from 300 scattered experimental devices during seasonal trials. Spatial selectivity was analysed by comparing the structural characteristics of used vs. available microhabitats, and evaluated against bottom-up and top-down hypotheses based on our previous knowledge on local seed bank abundance, composition and dynamics. Their foraging activity was also explored for spatial autocorrelation and environmental correlates at bigger scales.

Results

Postdispersal granivorous birds were less selective in their use of foraging space than expected if microhabitat appearance were providing them relevant information to guide their search for profitable foraging patches. No microhabitat type, as defined by their vegetation structure and soil cover, remained safe from bird exploration. Analyses at bigger temporal and spatial scales proved more important to describe heterogeneity in seed removal.

Conclusions

Closeness to tall trees, probably related to bird territoriality and reproduction or to their perception of predation risk, seemed to determine a first level of habitat selection, constraining explorable space. Then, microhabitat openness (rather than seed abundance) exerted some positive influence on which patches were more frequently visited among those accessible. Selective patterns by birds at small scales were closer to our predictions of a top-down spatial effect, with seed consumption creating or strengthening (and not responding to) the spatial pattern and dynamics of the seed bank.

Electronic supplementary material

The online version of this article (10.1186/s12898-019-0242-z) contains supplementary material, which is available to authorized users.

Beach vegetation as an indicator of human impacts in arid environments: Environmental conditions and landscape perception in the Canary Islands

Human occupancy of beaches is an important cause of environmental and landscape transformations, some of which are identifiable through vegetation analysis. Commonly, arboreal vegetation has been socially perceived in a positive way, as it contributes to the creation of environments appreciated as beautiful and natural. This type of vegetation has been recreated in urban coastal areas worldwide, including those located in arid environments where it is not always common or endemic to these areas. The typology of plant species, human impacts on beach environments, and the social perception of vegetation contrast were analyzed to understand the landscape influence and human impact on beach environments from arid regions. The study was carried out on 12 beaches with different degrees of human occupation (4 urban, 4 semi-urban and 4 natural) in Gran Canaria island (Spain). The results indicate that the number of exotic and ruderal (first to colonize human disturbed environments) species increases with human occupation of the beaches. A greater number of arboreal species were identified on urban beaches, while shrub and herbaceous species were more common on less occupied beaches (semi-urban and natural). However, when surveyed, the users of semi-urban and natural beaches, considered that arboreal vegetation compose a more attractive landscape than other with herbs or shrubs, even though tree species appear occasionally on these types of beaches. This inconsistency identifies a conflict of values between the development and conservation of beaches in arid environments. This study can be used to establish environmental sustainability strategies on beaches. Conservation and environmental information about ecosystem services related with indigenous plant species is and important issue for integrated management on beaches from arid regions, especially those that may be urbanized in the near future.

Do cacti form soil seed banks? An evaluation using species from the Southern Central Andes

There is controversy over whether cactus species form soil seed banks. Although it is commonly assumed that cacti do not form seed banks, very few studies have evaluated them. In this work, we analysed whether cactus species form soil seed banks, studying seed distribution, seed density and seed longevity in the Southern Central Andes. Soil samples were collected in two microhabitats (under nurse plants and in bare areas) at 12 selected sites. We determined seed presence-absence, density and distribution for 32 native cactus species. Seed longevity for six of these species was determined through a burial experiment. We recorded viable seeds for 62.5% of the 32 evaluated species, finding variation in seed density between microenvironments and among populations. In some species, the highest seed density was found under potential nurse plants. Seed germination and seed viability decreased with burial time, with seed longevity always being <24 months after burial. Our results show strong evidence that cactus species do form seed banks. Seed density can vary between microenvironments and among populations, suggesting that cactus-nurse plant associations can also be explained by differential seed dispersal and not only by differential establishment. We found that Echinopsis and Gymnocalycium species form short-term seed banks. Our results will help to better understand the population dynamics of cactus species, a focal species group for conservation actions because many of them are threatened by human activities.

Abiotic factors affect the recruitment and biomass of perennial grass and evergreen shrub seedlings in denuded areas of Patagonian Monte rangelands

Assessing the ability of key species to cope with environmental stresses in disturbed areas is an important issue for recovery of degraded arid ecosystem. Our objective was to evaluate the effect of soil moisture, exposure to UV radiation, and presence/absence of litter with different chemistry on soil N, recruitment and biomass of seedlings of perennial grass (Poa ligularis and Nassella tenuis) and evergreen shrub species (Atriplex lampa and Larrea divaricata) in denuded areas. We carried out a microcosm experiment with soil blocks (28 cm depth) sowed with seeds of the target species, subjected to different levels of litter type (perennial grass-evergreen shrub mixture, evergreen shrub mixture, and no litter), UV radiation (near ambient and reduced UV), and soil water (high: 15-25% and low 5-15%). Periodically, during 6 months, we assessed soil-N (total and inorganic) at two depths and species seedling recruitment at microcosms. Additionally, emerged seedlings of each species were transplanted to individual pots containing soil and subjected to the same previous factors during 12 months. Then, all plants were harvested and biomass assessed. Only inorganic soil-N at the upper soil varied among treatments increasing with the presence of evergreen shrub litter, exposure to ambient UV, and high soil water. Inorganic soil-N, promoted by near ambient UV and high soil water, had a positive effect on recruitment of perennial grasses and A. lampa. Both litter types promoted the recruitment of perennial grasses. Evergreen shrub litter and high soil water promoted the recruitment of L. divaricata. Seedling biomass of perennial grasses increased with high soil water and reduced UV. Ambient UV had positive or null effects on biomass of evergreen shrub seedlings. High soil water increased biomass of L. divaricata seedlings. We concluded that soil water appeared as the most limiting factor for seedling recruitment of all species whereas inorganic soil N limited the recruitment of the small-seeded perennial grasses and A. lampa. Ambient UV had negative effects on seedling biomass of perennial grasses. These complex relationships among abiotic factors and seed and plant traits should be taken into account when planning management actions after disturbances.

Prioritisation of native legume species for further evaluation as potential forage crops in water-limited agricultural systems in South Africa

In the face of climate change, identification of forage species suitable for dryland farming under low rainfall conditions in South Africa is needed. Currently, there are only a limited number of forage species suitable for dryland farming under such conditions. The objective of this study was to identify and prioritise native legume species that could potentially be used in dryland farming systems in water-limited agro-ecosystems in South Africa. Using a combination of ecological niche modelling techniques, plant functional traits, and indigenous knowledge, 18 perennial herbaceous or stem-woody legume species were prioritised for further evaluation as potential fodder species within water-limited agricultural areas. These species will be evaluated further for their forage quality and their ability to survive and produce enough biomass under water limitation and poor edaphic conditions.

A novel GIS-based approach to assess beekeeping suitability of Mediterranean lands

Honeybees are critically important for the environment and to the economy. However, there are in substantial decline worldwide, leading to serious threat to the stability and yield of food crops. Beekeeping is of pivotal importance, combining the wide economical aspect of honey production and the important ecological services provided by honeybees. In this scenario, the prompt identification of beekeeping areas is strategic, since it maximised productivity and lowered the risks of colony losses. Fuzzy logic is an ideal approach for problem-solving tasks, as it is specifically designed to manage problems with a high degree of uncertainty. This research tested a novel GIS-based approach to assess beekeeping suitability of lands located in Calabria (Southern Italy), without relying to Analytic Hierarchy Process – Multiple Criteria Decision Making (AHP-MCDM), thus avoiding the constraints due to the technique and decision makers’ influences. Furthermore, the data used here were completely retrieved from open access sources, highlighting that our approach is characterized by low costs and can be easily reproduced for a wide arrays of geographical contexts. Notably, the results obtained by our experiments were validated by the actual beekeeping reality. Besides beekeeping, the use of this system could not only be applied in beekeeping land suitability evaluations, but may be successfully extended to other types of land suitability evaluations.

Impact of treated wastewater reuse and floods on water quality and fish health within a water reservoir in an arid climate

Treated wastewater (TWW) reuse for agricultural irrigation is a well-established approach to coping with water shortages in semi-arid and arid environments. Recently, additional uses of TWW have emerged, including streamflow augmentation and aquatic ecosystem restoration. The purpose of the current study was to evaluate the water quality and fish health, in an artificial reservoir located in an arid climate (the Yeruham Reservoir, Israel), which regularly receives TWW and sporadic winter floods. The temporal distribution of water levels, nutrients and organic micropollutants (OMPs) were measured during the years 2013-2014. OMPs were also measured in sediment and fish tissues. Finally, the status of fish health was evaluated by histopathology. Water levels and quality were mainly influenced by seasonal processes such as floods and evaporation, and not by the discharge of TWW. Out of 16 tested OMPs, estrone, carbamazepine, diclofenac and bezafibrate were found in the reservoir water, but mostly at concentrations below the predicted no-effect concentration (PNEC) for fish. Concentrations of PCBs and dioxins in fish muscle and liver were much lower than the EU maximal permitted concentrations, and similar to concentrations that were found in food fish in Israel and Europe. In the histopathological analysis, there were no evident tissue abnormalities, and low to moderate infection levels of fish parasites were recorded. The results from the Yeruham Reservoir demonstrated a unique model for the mixture effect between TWW reuse and natural floods to support a unique stable and thriving ecosystem in a water reservoir located in an arid region. This type of reservoir can be widely used for recreation, education, and the social and economic development of a rural environment, such as has occurred in the Yeruham region.

Annual variation of (7)Be soil inventory in a semiarid region of central Argentina

Reliable information on environmental radionuclides atmospheric entrance, and their distribution along the soil profile, is a necessary condition for using these soil and sediment tracers to investigate key environmental processes. To address this need, (7)Be content in rainwater and the wet deposition in a semiarid region at San Luis Province, Argentina, were studied. Following these researches, in the same region, we have assessed the (7)Be content along a soil profile, during 2.5 years from September 2009 to January 2012. As expected, the specific activity values in soil samples in the wet period (November-April) were higher than in the dry period (May-October). During the investigated period (2009 - beginning 2012) and for all sampled points, the maximum value of the (7)Be specific activity (Bq kg(-1)) was measured at the surface level. A typical decreasing exponential function of (7)Be areal activity (Bq m(-2)) with soil mass depth (kg m(-2)) was found and the key distribution parameters were determined for each month. The minimum value of areal activity was 51 Bq m(-2) in August, and the maximum was 438 Bq m(-2) in February. The relaxation mass depth ranges from 2.9 kg m(-2) in March to 1.3 kg m(-2) in August. (7)Be wet deposition can explain in a very significant proportion the (7)Be inventory in soil. During the period of winds in the region (September and October), the (7)Be content in soil was greater than the expected contribution from wet deposition, situation that is compatible with a higher relative contribution of dry deposition at this period of the year.

Malaria control under unstable dynamics: reactive vs. climate-based strategies

In areas of the world where malaria prevails under unstable conditions, attacking the adult vector population through insecticide-based Indoor Residual Spraying (IRS) is the most common method for controlling epidemics. Defined in policy guidance, the use of Annual Parasitic Incidence (API) is an important tool for assessing the effectiveness of control and for planning new interventions. To investigate the consequences that a policy based on API in previous seasons might have on the population dynamics of the disease and on control itself in regions of low and seasonal transmission, we formulate a mathematical malaria model that couples epidemiologic and vector dynamics with IRS intervention. This model is parameterized for a low transmission and semi-arid region in northwest India, where epidemics are driven by high rainfall variability. We show that this type of feedback mechanism in control strategies can generate transient cycles in malaria even in the absence of environmental variability, and that this tendency to cycle can in turn limit the effectiveness of control in the presence of such variability. Specifically, for realistic rainfall conditions and over a range of control intensities, the effectiveness of such 'reactive' intervention is compared to that of an alternative strategy based on rainfall and therefore vector variability. Results show that the efficacy of intervention is strongly influenced by rainfall variability and the type of policy implemented. In particular, under an API 'reactive' policy, high vector populations can coincide more frequently with low control coverage, and in so doing generate large unexpected epidemics and decrease the likelihood of elimination. These results highlight the importance of incorporating information on climate variability, rather than previous incidence, in planning IRS interventions in regions of unstable malaria. These findings are discussed in the more general context of elimination and other low transmission regions such as highlands.

A new species of Metacyclops Kiefer, 1927 (Copepoda, Cyclopidae, Cyclopinae) from the Chihuahuan desert, northern Mexico

A new species of the freshwater cyclopoid copepod genus Metacyclops Kiefer, 1927 is described from a single pond in northern Mexico, within the binational area known as the Chihuahuan Desert. This species belongs to a group of Metacyclops species with a 3443 spine formula of swimming legs. It is morphologically similar to Metacyclops lusitanus Lindberg, 1961 but differs from this and other congeners by having a unique combination of characters, including a caudal rami length/width proportion of 3.5–3.8, a innermost terminal seta slightly longer than the outermost terminal seta, intercoxal sclerites of legs 1-4 naked, a strong apical spine of the second endopodal segment of leg 1 and one row of 6-8 small spinules at the insertion of this spine. The finding of this species represents also the first record of the genus in Mexico and the third in North America, where only two other species, Metacyclops gracilis (Lilljeborg, 1853)and Metacyclops cushae Reid, 1991 have been hitherto reported. This is also the first continental record of a species of Metacyclops from an arid environment in the Americas. This species appears to be endemic to the Chihuahuan Desert, thus emphasizing the high endemicity of this area.