Artificial resting sites: An alternative sampling method for adult mosquitoes.

Mosquito collections are commonly conducted with baited traps predominantly attracting host-seeking females. In contrast, resting sites are generally colonized by a broader range of the mosquito population, including a higher proportion of males and blood-engorged females. This study evaluates the sampling success of different artificial resting sites, attached to a deciduous or coniferous tree at different heights. As standard sampling method, carbon dioxide-baited Biogents Sentinel traps (BG traps) were operated in parallel. BG traps caught a higher number of specimens compared to the resting sites. However, the proportion of blood-engorged females and males was higher in resting sites. More Culiseta spp. specimens were collected in resting sites compared to BG traps, but less Aedes spp. specimens. In general, fewer specimens and species were recorded in small resting sites and at top height level compared to medium or large resting sites at medium or ground level. The proportion of males was highest at the ground, while the proportion of engorged females was highest at medium and top level. Due to the higher proportion of blood-engorged females, artificial resting sites are especially useful for studies of host-feeding patterns or xenosurveillance. Low costs and efforts allow a cost-effective increase of the number of resting sites per sampling site to collect more mosquitoes.

Ixodes frontalis: a neglected but ubiquitous tick species in Germany.

The ornithophilic tick species Ixodes frontalis (Panzer) is spatially distributed in Europe, Asia and northern Africa. It can serve as a carrier of different bacteria and viruses, but little is known of its actual vector competence. In addition, adult females of this species are associated with the avian "tick-related syndrome" (TRS). Like most ornithophilic tick species, I. frontalis is usually collected from bird nests or directly from their hosts. Reports of I. frontalis being collected with the flagging method are scarce. In Germany, the species is considered as very rare. In the few reports that are available, the majority of ticks has been discovered on migrating birds. Therefore, knowledge of the actual distribution of this species in Germany was strictly limited. In this study, we report the finding of 1084 individuals of I. frontalis collected with the flagging method in urban areas and gardens in several regions of Germany. Furthermore, the species was discovered on 35 dead Eurasian blackbirds (Turdus merula) from all over Germany. Finally, we report of five new possible cases of TRS, three in free-ranging birds and two in captive birds, including a Harris's hawk (Parabuteo unicinctus) kept for falconry.

Evaluating the risk for Usutu virus circulation in Europe: comparison of environmental niche models and epidemiological models.

BACKGROUND: Usutu virus (USUV) is a mosquito-borne flavivirus, reported in many countries of Africa and Europe, with an increasing spatial distribution and host range. Recent outbreaks leading to regional declines of European common blackbird (Turdus merula) populations and a rising number of human cases emphasize the need for increased awareness and spatial risk assessment. METHODS: Modelling approaches in ecology and epidemiology differ substantially in their algorithms, potentially resulting in diverging model outputs. Therefore, we implemented a parallel approach incorporating two commonly applied modelling techniques: (1) Maxent, a correlation-based environmental niche model and (2) a mechanistic epidemiological susceptible-exposed-infected-removed (SEIR) model. Across Europe, surveillance data of USUV-positive birds from 2003 to 2016 was acquired to train the environmental niche model and to serve as test cases for the SEIR model. The SEIR model is mainly driven by daily mean temperature and calculates the basic reproduction number R0. The environmental niche model was run with long-term bio-climatic variables derived from the same source in order to estimate climatic suitability. RESULTS: Large areas across Europe are currently suitable for USUV transmission. Both models show patterns of high risk for USUV in parts of France, in the Pannonian Basin as well as northern Italy. The environmental niche model depicts the current situation better, but with USUV still being in an invasive stage there is a chance for under-estimation of risk. Areas where transmission occurred are mostly predicted correctly by the SEIR model, but it mostly fails to resolve the temporal dynamics of USUV events. High R0 values predicted by the SEIR model in areas without evidence for real-life transmission suggest that it may tend towards over-estimation of risk. CONCLUSIONS: The results from our parallel-model approach highlight that relying on a single model for assessing vector-borne disease risk may lead to incomplete conclusions. Utilizing different modelling approaches is thus crucial for risk-assessment of under-studied emerging pathogens like USUV.

Experimental risk assessment for chikungunya virus transmission based on vector competence, distribution and temperature suitability in Europe, 2018.

BackgroundOver the last decade, the abundant distribution of the Asian tiger mosquito Aedes albopictus in southern Europe and the import of chikungunya virus (CHIKV) by infected travellers has resulted in at least five local outbreaks of chikungunya fever in France and Italy. Considering the ongoing spread of Ae. albopictus to central Europe, we performed an analysis of the Europe-wide spatial risk of CHIKV transmission under different temperature conditions. Methods:Ae. albopictus specimens from Germany and Italy were orally infected with CHIKV from an outbreak in France and kept for two weeks at 18 °C, 21 °C or 24 °C. A salivation assay was conducted to detect infectious CHIKV. Results: Analyses of mosquito saliva for infectious virus particles demonstrated transmission rates (TRs) of > 35%. Highest TRs of 50% for the mosquito population from Germany were detected at 18 °C, while the Italian population had highest TRs of 63% at 18 °C and 21 °C, respectively. Temperature data indicated a potential risk of CHIKV transmission for extended durations, i.e. sufficiently long time periods allowing extrinsic incubation of the virus. This was shown for areas already colonised by Ae. albopictus, as well as for large parts of central Europe that are not colonised. Conclusion: The current risk of CHIKV transmission in Europe is not primarily restricted by temperature, which allows extrinsic incubation of the virus, but rather by the vector distribution. Accordingly, all European countries with established populations of Ae. albopictus should implement respective entomological surveillance and monitoring systems, as basis for suitable control measures.

Distribution of Usutu Virus in Germany and Its Effect on Breeding Bird Populations.

Usutu virus (USUV) is an emerging mosquitoborne flavivirus with an increasing number of reports from several countries in Europe, where USUV infection has caused high avian mortality rates. However, 20 years after the first observed outbreak of USUV in Europe, there is still no reliable assessment of the large-scale impact of USUV outbreaks on bird populations. In this study, we identified the areas suitable for USUV circulation in Germany and analyzed the effects of USUV on breeding bird populations. We calculated the USUV-associated additional decline of common blackbird (Turdus merula) populations as 15.7% inside USUV-suitable areas but found no significant effect for the other 14 common bird species investigated. Our results show that the emergence of USUV is a further threat for birds in Europe and that the large-scale impact on population levels, at least for common blackbirds, must be considered.

West Nile Virus lineage-2 in Culex specimens from Iran.

OBJECTIVE: Screening of mosquitoes for viruses is an important forecasting tool for emerging and re-emerging arboviruses. Iran has been known to harbour medically important arboviruses such as West Nile virus (WNV) and dengue virus (DENV) based on seroepidemiological data. However, there are no data about the potential mosquito vectors for arboviruses in Iran. This study was performed to provide mosquito and arbovirus data from Iran. MATERIALS AND METHODS: A total of 32 317 mosquitos were collected at 16 sites in five provinces of Iran in 2015 and 2016. RT-PCR for detection of flaviviruses was performed. The PCR amplicons were sequenced, and 109 WNV sequences, including one obtained in this study, were used for phylogenetic analyses. RESULTS: The 32 317 mosquito specimens belonging to 25 species were morphologically distinguished and distributed into 1222 pools. Culex pipiens s.l. comprised 56.429%. One mosquito pool (0.08%), containing 46 unfed Cx. pipiens pipiens form pipiens (Cpp) captured in August 2015, was positive for flavivirus RNA. Subsequent sequencing and phylogenetic analyses revealed that the detected Iranian WNV strain belongs to lineage 2 and clusters with a strain recently detected in humans. No flaviviruses other than WNV were detected in the mosquito pools. CONCLUSION: Cpp could be a vector for WNV in Iran. Our findings indicate recent circulation of WNV lineage-2 strain in Iran and provide a solid base for more targeted arbovirus surveillance programs.

Experimental transmission of Zika virus by mosquitoes from central Europe.

Mosquitoes collected in Germany in 2016, including Culex pipiens pipiens biotype pipiens, Culex torrentium and Aedes albopictus, as well as Culex pipiens pipiens biotype molestus (in colony since 2011) were experimentally infected with Zika virus (ZIKV) at 18 °C or 27 °C. None of the Culex taxa showed vector competence for ZIKV. In contrast, Aedes albopictus were susceptible for ZIKV but only at 27 °C, with transmission rates similar to an Aedes aegypti laboratory colony tested in parallel.

Widespread activity of multiple lineages of Usutu virus, western Europe, 2016.

In the summer of 2016, Belgium, France, Germany and the Netherlands reported widespread Usutu virus (USUV) activity based on live and dead bird surveillance. The causative USUV strains represented four lineages, of which two putative novel lineages were most likely recently introduced into Germany and spread to other western European countries. The spatial extent of the outbreak area corresponded with R0 values > 1. The occurrence of the outbreak, the largest USUV epizootic registered so far in Europe, allowed us to gain insight in how a recently introduced arbovirus with potential public health implications can spread and become a resident pathogen in a naïve environment. Understanding the ecological and epidemiological factors that drive the emergence or re-emergence of USUV is critical to develop and implement timely surveillance strategies for adequate preventive and control measures. Public health authorities, blood transfusion services and clinicians in countries where USUV was detected should be aware of the risk of possible USUV infection in humans, including in patients with unexplained encephalitis or other neurological impairments, especially during late summer when mosquito densities peak.

Surveillance of maternal antibodies against West Nile virus in chicken eggs in South-West Germany.

OBJECTIVE: The emergence of West Nile virus (WNV) in several European countries increases the risk of its introduction to Germany. This study evaluated a new method for WNV surveillance by testing for maternal antibodies in chicken eggs. METHODS: A total of 1,990 eggs were collected in 35 sampling sites in the south-west of Germany and tested for WNV-specific antibodies. RESULTS: The results did not indicate evidence for WNV circulation in the study area. CONCLUSION: This work serves as a proof-of-concept that such a method is useful and a potential alternative to use of sentinel chicken for regular WNV surveillance.

Detection of Dirofilaria repens and Dirofilaria immitis DNA in mosquitoes from Belarus.

During the last two decades, Belarus faces an increase of human cases of Dirofilaria (Nematoda, Spirurida, Onchocercidae) infections. However, comprehensive analyses explaining this development and the identification of mosquito vector species are missing. Here, we present results using temperature data from Belarus and show that the annual number of human Dirofilaria cases is significantly correlated with the yearly average temperatures (Spearman's rho = 0.49, p < 0.05) and the average sum of potential Dirofilaria transmission days (Spearman's rho = 0.46, p < 0.05), suggesting that autochthonous transmission is at least in part responsible for the increasing number of clinical Dirofilaria cases in the country. In addition, 467 female mosquitoes were collected from different sampling sites in the regions of Brest and Minsk, which were analyzed by molecular methods for the presence of Dirofilaria repens and Dirofilaria immitis DNA, respectively. Two pools (5.56 %) were tested positive for Dirofilaria (estimated infection rate per 100 specimens = 0.44, 95 % confidence interval = 0.08-1.43), comprising one Anopheles claviger s.l. pool that was positive for D. repens and one Culex pipiens s.l./Culex torrentium pool positive for D. immitis DNA. This, to our knowledge, is the first molecular evidence for the presence of Dirofilaria in mosquitoes from Belarus, suggesting a high probability of autochthonous Dirofilaria transmission in the country.

Physico-Chemical Characteristics of Culex pipiens sensu lato and Culex torrentium (Diptera: Culicidae) Breeding Sites in Germany.

Culex pipiens sensu lato (L.) and Culex torrentium Martini, 1925 are two widely distributed mosquito species in Europe. Due to difficulties in morphological discrimination, the current knowledge on differences in the breeding ecology is fragmentary. Therefore, this study evaluated the relation between the presence-absence of both species at various types of breeding habitats in response to physico-chemical parameters, using a recently developed molecular assay that allows reliable species-specific typing of larvae and pupae. The results revealed that the two species often occur in sympatry at the studied breeding sites, and there were no substantial differences concerning presence-absence of the two species with regard to the various environmental parameters investigated.

Topsoil conditions correlate with the emergence rates of Culicoides chiopterus and Culicoides dewulfi (Diptera: Ceratopogonidae) from cowpats.

Culicoides chiopterus (Meigen), 1830 and Culicoides dewulfi Goetghebuer, 1936 (Diptera: Ceratopogonidae) are considered to develop exclusively in dung, but do not necessarily show an equal distribution and abundance on livestock farms in Northern Europe. Recent modelling studies identified soil parameters to explain these differences. The present study addressed the question whether topsoil conditions underneath cowpats correlate with the number of emerging C. chiopterus and C. dewulfi. We recorded the emergence of biting midges from 24 cowpats over a period of 4 weeks and analysed samples from the topsoil. In agreement with species distribution models based on remote data, our results detected the correlation of soil moisture, organic matter and soil texture with the number of emerging C. chiopterus and C. dewulfi. With increasing soil moisture, the number of emerging adults increased for both species and the amount of organic matter was positively correlated with the number of emerging C. chiopterus. In contrast, soil textures showed conflicting results, i.e. a positive and negative relationship with the same variables. According to our results, soil underneath dung can explain the number of emerging Culicoides species. The knowledge of these effects might improve the interpretation of large-scaled distribution models for dung-breeding biting midges.

Impact of mechanical disturbance on the emergence of Culicoides from cowpats.

The outbreaks of Bluetongue virus and Schmallenberg virus between 2006 and 2012 highlighted the need for control methods for north-western Palaearctic biting midge species. There is especially a demand for alternative control methods without application of insecticides. Therefore, the objective of this paper was to evaluate the impact of mechanical disturbance as a control method for Culicoides biting midges in cowpats. We used a trash rake to destroy the compact structure of cowpats and spread the dung over the ground. We expected the disturbance to cause a faster alteration of physical characteristics and drying of the dung, resulting in lower emergence from disturbed cowpats. Emerging biting midges were collected with emergence traps. The number of emerged Culicoides was compared between treated and control cowpats. A total of 12,979 biting midges emerged, all belonging to the Obsoletus group. The majority of the 6,758 male individuals were identified as Culicoides chiopterus (Meigen, 1830) (91.4%), followed by Culicoides dewulfi (Goetghebuer, 1936) (6.5%), and a small number of Culicoides scoticus (Downes & Kettle, 1952) (1.2%). Our results showed no significant differences between the emergence of Culicoides (males and females) from disturbed and control cowpats. The lack of differences is discussed in light of the time period chosen for the experiment and the climatic conditions (especially low temperatures) during the study period. The climatic conditions during the study did not favour desiccation effects and therefore did not cause a severe alteration of the dung and the biotic parameters. In conclusion, immature Culicoides showed a high tolerance against mechanical disturbance.

Culicoides biting midge density in relation to the position and substrate temperature in a cattle dung heap.

Dung heaps offer warm breeding sites, which might be suitable for a continuing development or even emergence at low air temperatures in winter. Therefore, this study collected substrate samples from the outer surface and core of a cattle dung heap at the beginning of the winter period. We aimed to analyze the density of immature Culicoides in relation to substrate position and temperature. We took samples from the outer layer and core of the dung heap at different heights. Floatation was used to extract Culicoides larvae from the dung heap samples. In order to rear larvae individually, we separated them in glass tubes. A total of 229 Culicoides larvae were extracted from the dung heap samples. Highest densities (99.1% of all larvae) were recorded for the outer layers of the dung heap but hardly any in the core (0.9% of all individuals). While the density of larvae was negatively correlated with increasing substrate temperatures, Culicoides larvae were found in a temperature range between 7.9 and 38.0 °C (mean 16.6 °C). Extracted larvae were reared to adults. All male individuals were identified as Culicoides obsoletus (Meigen), 1818 and all female individuals as C. obsoletus/Culicoides scoticus. It can be concluded that dung heaps offer temperature conditions, which allow the survival and probably also the development to adults for immature Culicoides also under harsh climate conditions in winter.

A mathematical model for malaria disease dynamics with vaccination and infected immigrants.

The world is aiming to eliminate malaria by 2030. The introduction of the pilot project on malaria vaccination for children in Kenya, Ghana, and Malawi presents a significant thrust to the elimination efforts. In this work, a susceptible, infectious and recovered (SIR) human-vector interaction mathematical model for malaria was formulated. The model was extended to include a compartment of vaccinated humans and an influx of infected immigrants. Qualitative and quantitative analysis was performed on the model. When there was no influx of infected immigrants, the model had a disease-free equilibrium point that was globally asymptotically stable when a threshold known as the basic reproductive number denoted by $ R_0 $ was less than one. When there was an influx of infected immigrants, the model had endemic equilibrium points only. Parameter sensitivity analysis on $ R_0 $ was performed and results showed that strategies must be implemented to reduce contact between mosquitoes and humans. Results from different vaccine coverage indicated that in the absence of an influx of infected immigrants, it is possible to achieve a malaria-free society when more children get vaccinated and the influx of infected humans is avoided. The analysis of the optimal control model showed that the combined use of vaccination, personal protective equipment, and treatment is the best way to curb malaria incidence, provided the influx of infected humans is completely stopped.

A convolutional neural network to identify mosquito species (Diptera: Culicidae) of the genus Aedes by wing images.

Accurate species identification is crucial to assess the medical relevance of a mosquito specimen, but requires intensive experience of the observers and well-equipped laboratories. In this proof-of-concept study, we developed a convolutional neural network (CNN) to identify seven Aedes species by wing images, only. While previous studies used images of the whole mosquito body, the nearly two-dimensional wings may facilitate standardized image capture and reduce the complexity of the CNN implementation. Mosquitoes were sampled from different sites in Germany. Their wings were mounted and photographed with a professional stereomicroscope. The data set consisted of 1155 wing images from seven Aedes species as well as 554 wings from different non-Aedes mosquitoes. A CNN was trained to differentiate between Aedes and non-Aedes mosquitoes and to classify the seven Aedes species based on grayscale and RGB images. Image processing, data augmentation, training, validation and testing were conducted in python using deep-learning framework PyTorch. Our best-performing CNN configuration achieved a macro F1 score of 99% to discriminate Aedes from non-Aedes mosquito species. The mean macro F1 score to predict the Aedes species was 90% for grayscale images and 91% for RGB images. In conclusion, wing images are sufficient to identify mosquito species by CNNs.

Mosquitoes from Europe Are Able to Transmit Snowshoe Hare Virus.

Snowshoe hare virus (SSHV) is a zoonotic arthropod-borne virus (arbovirus) circulating in colder areas of the Northern Hemisphere. SSHV is maintained in an enzootic cycle between small mammals and mosquitoes, assumably of the genera Aedes and Culiseta. Symptoms of SSHV human infection can range from asymptomatic to severe neuroinvasive disease. Studies on SSHV transmission are limited, and there is no information available on whether mosquitoes of the genus Culex are able to transmit SSHV. Therefore, we investigated six mosquito species via salivation assay for their vector competence. We demonstrated that SSHV can be transmitted by the abundant European Culex species Cx. pipiens biotype pipiens, Cx. pipiens biotype molestus, and Cx. torrentium with low transmission efficiency between 3.33% and 6.67%. Additionally, the invasive species Ae. albopictus can also transmit SSHV with a low transmission efficiency of 3.33%. Our results suggest that local transmission of SSHV after introduction to Europe seems to be possible from a vector perspective.

Wolbachia strains wMel and wAlbB differentially affect Aedes aegypti traits related to fecundity.

Two Wolbachia strains, wMel and wAlbB, have been transinfected into Aedes aegypti mosquitoes for population replacement with the aim of reducing dengue transmission. Epidemiological data from various endemic sites suggest a pronounced decrease in dengue transmission after implementing this strategy. In this study, we investigated the impact of the Wolbachia strains wMel and wAlbB on Ae. aegypti fitness in a common genetic background. We found that Ae. aegypti females infected with the wMel strain exhibited several significant differences compared with those infected with the wAlbB strain. Specifically, wMel-infected females laid significantly fewer eggs, ingested a lower amount of blood, had a reduced egg production rate, and exhibited a decreased Wolbachia density at a later age compared with mosquitoes infected with the wAlbB strain. Conversely, the wAlbB strain showed only mild negative effects when compared with Wolbachia-uninfected specimens. These differential effects on Ae. aegypti fitness following infection with either wMel or wAlbB may have important implications for the success of population replacement strategies in invading native Ae. aegypti populations in endemic settings. Further research is needed to better understand the underlying mechanisms responsible for these differences in fitness effects and their potential impact on the long-term efficacy of Wolbachia-based dengue control programs.IMPORTANCEThe transmission of arboviruses such as dengue, Zika, and chikungunya is on the rise globally. Among the most promising strategies to reduce arbovirus burden is the release of one out of two strains of Wolbachia-infected Aedes aegypti: wMel and wAlbB. One critical aspect of whether this approach will succeed involves the fitness cost of either Wolbachia strains on mosquito life history traits. For instance, we found that wMel-infected Ae. aegypti females laid significantly fewer eggs, ingested a lower amount of blood, had a reduced egg production rate, and exhibited a decreased Wolbachia density at a later age compared with mosquitoes infected with the wAlbB strain. Conversely, the wAlbB strain showed only mild negative effects when compared with Wolbachia-uninfected specimens. These differential effects on mosquito fitness following infection with either wMel or wAlbB may have important implications for the success of population replacement strategies in invading native Ae. aegypti populations.

Evaluation of the vector competence for Batai virus of native Culex and exotic Aedes species in Central Europe.

BACKGROUND: Batai virus (BATV) is a zoonotic arbovirus of veterinary importance. A high seroprevalence in cows, sheep and goats and infection in different mosquito species has been observed in Central Europe. Therefore, we studied indigenous as well as exotic species of the genera Culex and Aedes for BATV vector competence at different fluctuating temperature profiles. METHODS: Field caught Culex pipiens biotype pipiens, Culex torrentium, Aedes albopictus and Aedes japonicus japonicus from Germany and Aedes aegypti laboratory colony were infected with BATV strain 53.3 using artificial blood meals. Engorged mosquitoes were kept under four (Culex species) or three (Aedes species) fluctuating temperature profiles (18 ± 5 °C, 21 ± 5 °C, 24 ± 5 °C, 27 ± 5 °C) at a humidity of 70% and a dark/light rhythm of 12:12 for 14 days. Transmission was measured by testing the saliva obtained by forced salivation assay for viable BATV particles. Infection rates were analysed by testing whole mosquitoes for BATV RNA by quantitative reverse transcription PCR. RESULTS: No transmission was detected for Ae. aegypti, Ae. albopictus or Ae. japonicus japonicus. Infection was observed for Cx. p. pipiens, but only in the three conditions with the highest temperatures (21 ± 5 °C, 24 ± 5 °C, 27 ± 5 °C). In Cx. torrentium infection was measured at all tested temperatures with higher infection rates compared with Cx. p. pipiens. Transmission was only detected for Cx. torrentium exclusively at the highest temperature of 27 ± 5 °C. CONCLUSIONS: Within the tested mosquito species, only Cx. torrentium seems to be able to transmit BATV if the climatic conditions are feasible.

Large-scale performance assessment of the BG-Counter 2 used with two different mosquito traps.

BACKGROUND: Mosquitoes are important vectors of pathogens. They are usually collected with CO2-baited traps and subsequently identified by morphology. This procedure is very time-consuming. Automatic counting traps could facilitate timely evaluation of the local risk for mosquito-borne pathogen transmission or decision-making on vector control measures, but the counting accuracy of such devices has rarely been validated in the field. METHODS: The Biogents (BG)-Counter 2 automatically counts mosquitoes by discriminating the size of captured objects directly in the field and transmits the data to a cloud server. To assess the accuracy of this counting device, 27 traps were placed at 19 sampling sites across Germany and used in daily, weekly or bimonthly intervals from April until October 2021. The BG-Counter 2 was attached to a CO2-trap (BG-Pro trap = CO2-Pro) and the same trap was converted to also attract gravid mosquitoes (upside-down BG-Pro trap with a water container beneath = CO2-Pro-gravid). All captured mosquitoes were identified by morphology. The number of females (unfed and gravid), mosquito diversity and the number of identified specimens in relation to the counting data of the BG-Counter were compared between the two trapping devices to evaluate sampling success and counting accuracy. RESULTS: In total 26,714 mosquitoes were collected during 854 trap days. The CO2-Pro-gravid trap captured significantly more mosquitoes per trap day for all specimens, gravid females and non-gravid females, while there was no difference in the mosquito diversity. The linear model with the captured mosquitoes as a response and the counted specimens as a predictor explained only a small degree of the variation within the data (R2 = 0.16), but per individual trap the value could reach up to 0.62 (mean R2 = 0.23). The counting accuracy for the daily samples had a significant positive correlation with sample size, resulting in higher accuracy for the CO2-Pro-gravid trap and higher accuracy for sites and sampling months with high mosquito abundance. CONCLUSIONS: While the accuracy of the BG-Counter 2 is quite low, the device is able to depict mosquito phenology and provide information about local population dynamics.