Variation In Population Dynamics Research Articles

Seasonal Variations in Population Dynamics of Insect Pests in Tiruvallur District, Tamil Nadu, India

Understanding the complex relationship between seasonal changes and pest dynamics is essential for establishing effective protection methods in contemporary agriculture and guaranteeing long-term agricultural sustainability and food security. The study was conducted in the Tiruvallur District of Tamil Nadu, India, which is characterized by a tropical climate with distinct wet and dry seasons [1]. Shannon-Wiener Index and Simpson's Index biodiversity indices reflected the moderate to high pest diversity of species in the region. Values for Shannon-Wiener indexes ranged between about 1.93-1.95 for different species of insect pests, and Simpson's indexes were found to range between about 0.85-0.86. All these indices indicate a well-balanced insect pest community with high species richness and even distribution, which is necessary to maintain ecological resilience. The findings enrich our understanding of pest ecology in tropical agriculture and provide valuable insights applicable to other regions facing similar issues. The observed seasonal patterns emphasize the importance of ongoing monitoring and adaptive management to tackle the challenges posed by insect pests amid climate variability and agricultural intensification. Additionally, this research offers a thorough framework for comprehending and managing insect pest populations in the Tiruvallur District.

Seasonal Patterns and Abiotic Influences on Fall Armyworm Dynamics in Chhattisgarh's Maize Agroecology

The fall armyworm Spodoptera frugiperda (J. E. Smith), an invasive pest in India, exhibits variations in population dynamics and incidence levels compared to its native regions. Understanding these variations is crucial for developing effective management strategies. Given India's diverse agroecosystems and climatic conditions, continuous watch on pest dynamics is essential. In this context a fixed plot experiment for comprehensive analysis of fall armyworm population dynamics, incidence patterns across seasons, and damage potentials in the maize crop ecosystem of the Chhattisgarh plains, India was conducted across three seasons of the year 2022-23. The year-round activity of the pest and its potential to cause huge losses in the early stages of maize was reported. Specifically, the study provided insights into the comparative incidence of fall armyworm in the different maize growing seasons of the area with a maximum incidence in the rainy season (0.58 larvae/plant) followed by winter (0.56 larvae/plant) and summer (0.53 larvae/plant) seasons. Moreover, the incidence trends of fall armyworm in different growing stages of maize were analysed by considering egg laying pattern, leaf damage, larval incidence and plant damage parameters, which highlighted the plant age-dependent response of fall armyworm. The impact of various weather parameters in shaping the damage and population fluctuations was analysed, where the influence of temperature was significant. Results obtained in this study are crucial in devising ETL levels and developing integrated pest management strategies against fall armyworm.

Spatio-temporal metapopulation trends: The coconut crabs of Zanzibar.

Species experience a variety of environmental and anthropogenic conditions across their ranges leading to spatial variation in population dynamics. Understanding population dynamics under different conditions is important but it is challenging to allocate limited effort to spatial and temporal subpopulation monitoring. Using GLMMs, we analyze survey data of a metapopulation of coconut crabs spanning 7 years and 15 sites in and near the Pemba archipelago, Zanzibar, to estimate trends in population size (based on catch per unit effort), weight and sex ratio at the meta- and subpopulation level and investigate anthropogenic drivers of these trends. We found that the overall metapopulation has remained stable in terms of size and composition over the survey period, but observed diverging trends in population size and sex ratio at some subpopulations. Formal protection of sites was associated with positive population trends. Of nine sites for which we could estimate site-specific trends, three showed increasing and two decreasing trends, whereas four sites had stable subpopulations. Although anthropogenic factors affected the average weight, and the incidence of small and large individuals, we found no temporal trends in any weight-related measures. Furthermore, there were no apparent patterns between weight-related measures and subpopulation trends. The metapopulation was biased toward males, and exploitation appeared to be associated with declining trends in the proportion of females, likely an artifact of a strong decline in the proportion of females in one of only two exploited sites in the dataset. Educational campaigns implemented in 2020 at six sites were not related to higher population sizes in later surveys. The variable trends in subpopulation sizes and composition highlight the need for spatially replicated monitoring in metapopulations. The analyses further provide a detailed baseline for future subpopulation studies of this vulnerable species in one of its last remaining metapopulations in the Western Indian Ocean.

California steelhead populations were regionally buffered and individually resistant to a severe multi-year drought

Weather extremes, such as drought, are predicted to be a strong determinant of species persistence under climate change. Yet predictions often fail to consider that variation in streamflow responses, variation in population dynamics, or adaptations to drought could buffer species against extremes. In this study, we examined the responses of eight California (USA) steelhead populations to a severe drought from 2012 to 2016. We observed that streamflows were highly synchronous across the region in all seasons and did not appear to buffer drought impacts. Population dynamics were variable across the region and did appear to buffer the region from drought impacts. Some populations had very low productivity for 4 years associated with the drought, while others had slightly below-average productivity for only 2 years. Population synchrony was associated with spring-smolt flow, temperature, and drought over time, but was not associated with winter-spawner or summer-juvenile drought, suggesting populations may be adapted to drought conditions. Our results highlight how regional buffering and adaptation can be important mechanisms against climate extremes both now and into the future.

How to quantify developmental synchrony in malaria parasites

Malaria infections represent an iconic example of developmental synchrony, where periodic fevers can result when the population of parasites develops synchronously within host red blood cells. The level of synchrony appears to vary across individual hosts and across parasite species and strains, variation that—once quantified—can illuminate the ecological and evolutionary drivers of synchrony. Yet current approaches for quantifying synchrony in parasites are either biased by population dynamics or unsuitable when population growth rates vary through time, features ubiquitous to parasite populations in vitro and in vivo. Here we develop an approach to estimate synchrony that accounts for population dynamics, including changing population growth rates, and validate it with simulated time series data encompassing a range of synchrony levels in two different host-parasite systems: malaria infections of mice and human malaria parasites in vitro. This new method accurately quantifies developmental synchrony from per capita growth rates using obtainable abundance data even with realistic sampling noise, without the need to sort parasites into developmental stages. Our approach enables variability in developmental schedules to be disentangled from even extreme variation in population dynamics, providing a comparative metric of developmental synchrony.

Accounting intra-annual variability in mortality and recruitment in stock status evaluation of Parapenaeopsis stylifera fishery of north-eastern Arabian Sea under moderate data scenario

Length-based integrated mixed effect (LIME) approach was applied for the assessment of Parapenaeopsis stylifera stock, the most prominent penaeid resource along Gujarat coast. Month was selected as a temporal step size to improve estimate precision and capture intra-annual variation in population dynamics. Catch was provided as an additional input to create a moderate data scenario and reduce bias in estimates of reference indices. The values of key life history priors Linf, K, M, t0, Lm50, Lm95 were 160.59 mm total length (TL), 1.68 yr−1, 2.406 yr−1, −0.01 yr, 89.1 mm TL, 95.06 mm TL, respectively. The LWR was established as W = 0.0117*TL2.652. The estimated SPR ranged between 0.33 and 0.70. The monthly fishing mortality was estimated between 0.06 and 0.31. In 37.5% of the observed month, the fishing mortality was above optimum, which by and large coincides with the peak fishing months. The recruitment is continuous, with a coefficient of variation of only 18.5%. Based on these indices, the stock can be considered as healthy or sustainable. A continuous monitoring and collection of abundance data through experimental surveys are recommended as a future course of action.

Human infrastructures correspond to higher Adélie penguin breeding success and growth rate.

Anthropogenic activities generate increasing disturbance in wildlife especially in extreme environments where species have to cope with rapid environmental changes. In Antarctica, while studies on human disturbance have mostly focused on stress response through physiological and behavioral changes, local variability in population dynamics has been addressed more scarcely. In addition, the mechanisms by which breeding communities are affected around research stations remain unclear. Our study aims at pointing out the fine-scale impact of human infrastructures on the spatial variability in Adélie penguin (Pygoscelis adeliae) colonies dynamics. Taking 24 years of population monitoring, we modeled colony breeding success and growth rate in response to both anthropic and land-based environmental variables. Building density around colonies was the second most important variable explaining spatial variability in breeding success after distance from skua nests, the main predators of penguins on land. Building density was positively associated with penguins breeding success. We discuss how buildings may protect penguins from avian predation and environmental conditions. The drivers of colony growth rate included topographical variables and the distance to human infrastructures. A strong correlation between 1-year lagged growth rate and colony breeding success was coherent with the use of public information by penguins to select their initial breeding site. Overall, our study brings new insights about the relative contribution and ecological implications of human presence on the local population dynamics of a sentinel species in Antarctica.

Demographic approaches for assessing the conservation status of Scopoli’s Shearwater Calonectris diomedea and the Balearic Shearwater Puffinus mauretanicus

In the north-western Mediterranean there are two breeding species of procellariforms from the Procellariidae family: Scopoli’s shearwater Calonectris diomedea and the Balearic shearwater Puffinus mauretanicus. Long-term monitoring carried out in a number of breeding colonies provides enough data to be able to assess the conservation status of both species using demographic approaches that estimate parameters such as survival, recruitment and fertility. This type of approach is recommended because it provides a reliable conservation diagnosis and knowledge of the processes that determine variations in population dynamics. Both species were found to have critically low adult survival rates, unexpected in such long-lived species, which makes these populations unviable under current conditions. This agrees with previous available information on incidental bycatch on fishing gears, and confirms that this threat, together with predation by terrestrial carnivores are of critical concern for the conservation of the populations. The fact that some of the breeding colonies did not show a declining trend indicates that several compensatory mechanisms, such as an immigration rescue effect, may be acting at local level. Nevertheless, all the evidence gathered to date suggests that these compensatory mechanisms are not permanent and that if no action is taken these populations could become extinct. In the case of Scopolis’ shearwater, the global population is much more abundant, so there may be time for mitigation actions to be undertaken. Given the size of the breeding population of Balearic shearwaters, we recommend urgent measures be carried out to reduce adult mortality in this endemic species to prevent its extinction.

Mito‐nuclear discordance and phylogeography of the surf clam Mesodesma donacium along the Southeast Pacific coast

AbstractMesodesma donacium is a surf clam endemic to the southeast Pacific coast, and it is an important resource species of the sandy beach artisanal fishery in Peru and Chile. Over time, the species has shown high variability in population dynamics (presence and abundance), which has been attributed to overfishing and environmental events. In this study, we assess the phylogeography of seven natural beds of M. donacium (17 to 42° S), to reveal the geographic distribution of the genetic diversity through the analysis of 278 sequences of the mitochondrial gene COI. Sequences of the nuclear genes 18S and 28S were used to evaluate the divergence of COI haplogroups. Two divergent parapatric mitochondrial haplogroups were found, which lacked divergence at nuclear markers (18S and 28S); this mito‐nuclear discordance allows inferring that there is no reproductive isolation of mitochondrial haplogroups. The North haplogroup is the only one present at the northernmost site, while only the South haplogroup was present in Cucao in the south. Between 28° and 32° S, coincident with a coastal biogeographic break at 30° S, both haplogroups are in sympatry. Haplogroups differed in their genetic structure, with the North haplogroup representing a single, highly diverse population and the South haplogroup with genetic differentiation and more restricted genetic diversity and gene flow. The divergence in mitochondrial haplogroups without nuclear divergence suggests a past scenario of geographic isolation in the northern and southern areas, without developing reproductive isolation, followed by secondary contact. Given the phylogeography, genetic information should be considered in restocking and management activities.

Life History Traits of the Stygophilous Amphipod Synurella ambulans in the Hyporheic Zone of the Lower Reaches of the Upper Sava River (Croatia)

Estimating the growth and population dynamics of crustaceans is important for understanding the role of species in ecosystems and for conservation and monitoring purposes. This study investigated temporal and spatial variation in population dynamics (growth rate, instantaneous mortality rates, and longevity) of the stygophilous freshwater amphipod Synurella ambulans (F. Müller, 1846), and influencing environmental factors. Seasonal sampling was conducted from December 2018 to October 2019 at two sampling sites (Jarun and Medsave) along the Sava River in northwestern Croatia. A Bhattacharya cohort analysis was applied to the length-frequency data using the FISAT software package. At least four cohorts were distinguished during the year. The possible influence of environmental factors on growth parameters was investigated using Canonical Correspondence Analysis (CCA), which revealed that the important environmental factors influencing S. ambulans abundance were water temperature and dissolved oxygen concentration. The average total body length (TBL) of females was 4.25 mm, while the TBL of males was 3.34 mm. The asymptotic length (L∞) and growth coefficient (K) were estimated to be 6.30 mm and 0.92 year−1 for females and 5.40 mm and 0.59 year−1 for males, respectively, at the Jarun site. L∞ and K were estimated to be 7.20 mm and 0.34 year−1, respectively, for females and 4.00 mm and 1.20 year−1, respectively, for males at the Medsave site. Estimated total mortality (Z) for each sex had higher values for males than females at both sampling sites. The lack of ecological knowledge on S. ambulans populations and relationships with invertebrate communities in the hyporheic zone of the large river ecosystems emphasises the importance of a detailed study for protecting this species and its vulnerable ecotonal groundwater-connected environment.

The living dead: Demography of Australian sandalwood in Australia's western rangelands

AbstractOne‐third of the world's trees are at risk of extinction, with large, old, long‐lived trees among the most vulnerable. Long‐lived trees in arid and semi‐arid biomes are particularly at risk, including Australian sandalwood (Santalum spicatum, Santalaceae), which is experiencing substantial population decline due to a suite of natural and anthropogenic drivers, with no appreciable recruitment estimated for more than 80 years. To contextualize this range‐wide collapse and quantify regional variation in population dynamics across Australia's western rangelands, we investigated the size‐class profiles of 12 sandalwood populations in a 1,500‐kilometre arc between Shark Bay and the Gibson Desert in central Western Australia including Indigenous Protected Areas, pastoral leases and public and private conservation parks and reserves. Stem diameters, indicative of age using known growth rates, were recorded for 1,355 sandalwood plants, along with a set of another plant structural and ecological parameters. Using size‐class profiles and associated demographic data, we estimated the population age structure and trajectory to determine whether each population was increasing, stable or declining. Our surveys revealed sandalwood populations are declining and are composed almost entirely of very old trees in advanced states of senescence. Of 1,355 plants sampled, 1,198 (88.4%) individuals were large (old) trees. A total of 23 seedlings and 21 saplings were recorded across all sites, almost all of which (22 and 19, respectively) were in one population, and located under the canopies of parent trees where they would not be expected to survive to maturity. Our findings reinforce the urgent need to list Santalum spicatum as a threatened species in Western Australia (where wild plants are still being commercially harvested) and to initiate effective conservation actions to secure the species' continued existence across its natural range.

Improving sustainable crop protection using population genetics concepts.

Growing genetically resistant plants allows pathogen populations to be controlled and reduces the use of pesticides. However, pathogens can quickly overcome such resistance. In this context, how can we achieve sustainable crop protection? This crucial question has remained largely unanswered despite decades of intense debate and research effort. In this study, we used a bibliographic analysis to show that the research field of resistance durability has evolved into three subfields: (1) "plant breeding" (generating new genetic material), (2) "molecular interactions" (exploring the molecular dialogue governing plant-pathogen interactions) and (3) "epidemiology and evolution" (explaining and forecasting of pathogen population dynamics resulting from selection pressure[s] exerted by resistant plants). We argue that this triple split of the field impedes integrated research progress and ultimately compromises the sustainable management of genetic resistance. After identifying a gap among the three subfields, we argue that the theoretical framework of population genetics could bridge this gap. Indeed, population genetics formally explains the evolution of all heritable traits, and allows genetic changes to be tracked along with variation in population dynamics. This provides an integrated view of pathogen adaptation, in particular via evolutionary-epidemiological feedbacks. In this Opinion Note, we detail examples illustrating how such a framework can better inform best practices for developing and managing genetically resistant cultivars.

Unravelling the causes and consequences of dispersal syndromes in a wild passerine.

Evidence accumulates that dispersal is correlated with individual behavioural phenotype (dispersal syndrome). The evolutionary causes and consequences of such covariation depend on the degree of plasticity versus inheritance of the traits, which requires challenging experiments to implement in mobile organisms. Here, we combine a forced dispersal experiment, natural colonization and longitudinal data to establish if dispersal and aggression levels are integrated and to test their adaptive nature in pied flycatchers (Ficedula hypoleuca). We found that (forced) dispersers behaved more aggressively in their first breeding year after dispersal and decreased their aggression in following years. Strength of dispersal syndrome and direction of fecundity selection on aggression in newly colonized areas varied between years. We propose that the net benefits of aggression for dispersers increase under harsh conditions (e.g. low food abundance). This hypothesis now warrants further testing. Overall, this study provides unprecedented experimental evidence that dispersal syndromes can be remodelled via adaptive plasticity depending on the individuals' local breeding experience and/or year-specific ecological conditions. It highlights the importance of individual behavioural variation in population dynamics.

A novel statistical framework for exploring the population dynamics and seasonality of mosquito populations.

Understanding the temporal dynamics of mosquito populations underlying vector-borne disease transmission is key to optimizing control strategies. Many questions remain surrounding the drivers of these dynamics and how they vary between species—questions rarely answerable from individual entomological studies (that typically focus on a single location or species). We develop a novel statistical framework enabling identification and classification of time series with similar temporal properties, and use this framework to systematically explore variation in population dynamics and seasonality in anopheline mosquito time series catch data spanning seven species, 40 years and 117 locations across mainland India. Our analyses reveal pronounced variation in dynamics across locations and between species in the extent of seasonality and timing of seasonal peaks. However, we show that these diverse dynamics can be clustered into four ‘dynamical archetypes’, each characterized by distinct temporal properties and associated with a largely unique set of environmental factors. Our results highlight that a range of environmental factors including rainfall, temperature, proximity to static water bodies and patterns of land use (particularly urbanicity) shape the dynamics and seasonality of mosquito populations, and provide a generically applicable framework to better identify and understand patterns of seasonal variation in vectors relevant to public health.

Variation in population dynamics and abundance of the bigeye croaker Micropogonias megalops in the Northern Gulf of California

The bigeye croaker Micropogonias megalops is an endemic Sciaenidae fish species of the Gulf of California. Although it is a stock that has been exploited for nearly three decades, its biological and fishery information has been limited over time. Therefore, its recent and current population status is poorly known. This study analyzed biological and fishery data for M. megalops in the Northern Gulf of California for the period 1995–2020. Variation of species population dynamics has been analyzed for years with biological information (2000, 2010, and 2020), finding points in time with relative decreases and increases in growth and natural mortality values. An interannual abundance analysis was performed, obtaining biological reference points for the resource through two surplus production models, the Monte Carlo (CMSY+) and the Bayesian state–space Schaefer surplus production model (BSM) methods. The results for management (based on the BSM analysis) indicated that the currently relative stock biomass level is at 79% of virgin biomass (k), which means a recovery compared to the 2017 biomass level (64% k) that has been the lowest in this fishery history. According to the Kobe phase plot, the resource has been harvested in a healthy way, showing a maximum sustainable yield of 8 248.52 t and current status of sub-exploited.

Spatio‐temporal variation in post‐recovery dynamics in a large Peregrine Falcon (Falco peregrinus) population in the Jura mountains 2000–2020†

After spectacular population crashes in the 1960 and 1970s, Peregrine Falcon Falco peregrinus populations recovered worldwide, and in the 2000s many study populations were back to normal. However, post‐recovery trends have been documented less well. We combined three long‐term population studies covering the entire Jura mountain range (16 304 km2) to examine spatio‐temporal variation in population dynamics during 2000–2020 in 420 known nesting sites in five regions: Ain, Jura and Doubs in France, and Jura Sud and Jura Nord in Switzerland. Every year about 60% of all sites were surveyed at least once, and this proportion increased over time. We used Bayesian occupancy modelling to investigate site persistence and colonization probabilities and correct status and trend estimates for bias due to non‐random site coverage. Based on the average of two models correcting for preferential sampling, we estimated that population size peaked in 2002 (Jura), 2005 (Doubs), 2007 (Ain, Jura Nord) and in 2007 for the Jura as a whole. Thereafter, the population declined significantly in four regions and in the Jura as a whole, with the strongest decline found in the Jura Nord ( –38%, 95% credible interval –34%/–41%) during 2007–2020. Thus, we found considerable spatial heterogeneity in post‐recovery trends and widespread post‐recovery declines. Reasons for the latter may include Eagle Owl Bubo bubo predation, illegal persecution and human disturbance. Our results illustrate how quickly positive population trends may be reversed, such that continuous long‐term monitoring even for species seemingly ‘out of danger’ remains invaluable. Our study also emphasizes the importance of correcting for both coverage bias in general and preferential sampling in particular when assessing population trends in studies where not every territory can be surveyed in all years.

Small-Scale and Long-Term Variability in Population Dynamics of the Cockle Cerastoderma edule in a Southern North Sea Tidal Flat System

The cockle Cerastoderma edule is one of the most common macrofauna species in the Wadden Sea areas of the North Sea. Cockle population dynamics are influenced by various abiotic and biotic factors such as temperature, food availability, and inter- and intraspecific competition. Cockles play an important role in the food web of the Wadden Sea, for instance, large shellfish-eating birds, such as oystercatchers and common eiders, use the cockle C. edule and the blue mussel Mytilus edulis as a main diet component. However, the populations of shellfish-eating bird species have been declining dramatically across the Wadden Sea since the beginning of the 21st century. While there are detailed monitoring programs in blue mussels due to commercial interests, little information is known about the stocks and long-term dynamics of cockles in the German Wadden Sea. To fill this gap, in 2005 a local conservation society (“Der Mellumrat e.V.”) initiated a study to sample cockles at one transect per year south of the island of Mellum, which was extended by 5 more transects in 2011. In addition to the spatial analysis, we analyzed the long-term variability in cockle population dynamics. Min/max autocorrelation factor analysis (MAFA) revealed a decline in cockle abundance, while no clear length trends were found. Canonical and spearman correlation analyses exposed significant correlations between cockle abundance and length and chlorophyll a, mussel bank area as well as oystercatcher and common eider populations. This study clearly shows that there is an urgent need for comprehensive time series of cockle data to analyze and explain ecological long-term changes in cockle population dynamics in relation to environmental changes and to point out how parts of the Wadden Sea food web, such as shellfish-eating birds are affected by these changes.

Effects of climate variability on an estuarine green crab Carcinus maenas population

The increase in frequency and intensity of extreme climate events over the last few decades has been leading to profound changes in estuarine and marine ecosystems worldwide, with strong implications for the species inhabiting these ecosystems as well as for the services provided by them. In this study, we analysed the effects of climate variability on the temporal and spatial variations in population dynamics of the green crab Carcinus maenas in the Mondego estuary (Portugal), between 2003 and 2018. In this 15-year period, a greater recruitment of C. maenas was observed during drought periods, periods which was matched by an increase in secondary production. Ontogenic stage segregation was also observed, with juveniles being found mainly in the further upriver areas of the estuary. The estuarine population was mainly composed of the green morphotype, with the orange and red morphotypes present in more downstream areas of the estuary. Redundancy analysis (RDA) showed high spatial and temporal variability of C. maenas in the estuary which was related with environmental changes over the 15-year period. A correlation between C. maenas biological features and several local-scale (salinity and river runoff) and large-scale (North Atlantic Oscillation index and Eastern Atlantic pattern) environmental variables was identified through cumulative sums analysis (CUSUM), indicating a strong environmental control on C. maenas population dynamics. This paper shows the importance of relatively long-term datasets to unravel the effects of extreme weather events due to climate change on key epibenthic estuarine species, and also how they might cope with a changing marine environment.

Abundance and phenology of two pest species, Cacoecimorpha pronubana and Epiphyas postvittana (Lepidoptera: Tortricidae)

AbstractCacoecimorpha pronubana (Hübner, [1799]) and Epiphyas postvittana (Walker, 1863) are economically important polyphagous pest species. The larvae of these moths affect a wide range of horticultural crops. We evaluated the seasonal abundance and population dynamics of these two species, hypothesising that both species of moth exhibit similar patterns in their seasonal abundance and respond to abiotic factors. The study was carried out on a wide range of protected ornamental crops grown on a total area of 1 ha at a commercial nursery. The study was completed over five consecutive years from 2015 to 2019, where both populations were monitored weekly during the months of moth activity, from April to November, using sex pheromone traps to trap the males of both species. The timing and abundance of catches were analysed in relation to local meteorological data. The mean yearly abundance of adult males was 604 ± 23.89 (mean ± SE; C. pronubana) and 1706 ± 167.18 (E. postvittana) also differing significantly between years for both species. There was no influence of any weather measures on the abundance of E. postvittana, but sunshine duration (4.84 ± 0.26 hr) and temperature (13.04 ± 0.57°C) affected the mean seasonal abundance of C. pronubana. There was an overall difference in the seasonal pattern of abundance between the species studied. While we demonstrate a seasonal abundance difference between years for C. pronubana, we found no significant seasonal differences for E. postvittana. Improved understanding of seasonal abundance, phenological patterns and inter‐seasonal variations in population dynamics of these two species may be useful in developing forecasting models that can be used in improving integrated pest management strategies for these two pests.

Molecular mechanisms of self-regulation in multiannual rodent populations: Experimental test of an updated hypothesis.

Edwards, P. D., Frenette-Ling, C., Palme, R., & Boonstra, R. (2021). Social density suppresses GnRH expression and reduces reproductivity in voles: A mechanism for population self-regulation. Journal of Animal Ecology, 90, 784-795. Intrinsic population processes are important in the regulation of populations of small rodents, including those which display multiannual cycles. By measuring reproductive parameters, faecal androgen metabolites, and gene expression and DNA methylation in the CNS of juvenile voles, this paper demonstrates that suppression of reproduction occurs in female voles at high density compared to low density in enclosures, and that this maternal, epigenetic effect is also apparent in their offspring. This suggsests that direct density dependence influences reproduction and, hence, immediate rate of population growth, while gene expression mediated by DNA methylation blocking transcription, may have a delayed density-dependent effect in juveniles. Both direct and delayed density dependence are necessary to generate multiannual population cycles. Edwards et al. (2021) break new ground in demonstrating the molecular and physiological basis of variation in population dynamics of small mammals ranging from multiannual cycles to stability that have fascinated researchers for nearly a century.