Seasonal Population Fluctuations Research Articles

Temporal and Spatial Dynamics of Plankton Communities in the Lower Haora River, Tripura, India

Planktons are significant bioindicator of ecosystem functioning, knowledge of the seasonal fluctuation in the plankton population in riverine waters of Indian subcontinent is rather limited. In the present study, analysis regarding spatio-temporal variations based on different multivariate statistics and indicator value analysis is done along with analysis of community structure of plankton assemblages. A total of 46 plankton taxa out of which 38 phytoplankton and 8 zooplankton taxa have been identified based on examination of samples taken from four locations over three sampling seasons. The primary phytoplankton families that involve Chlorophyceae, Bacillariophyceae, Cyanophyceae, Euglenophyceae and Composopogonophyceae. Chlorophyceae dominated the phytoplankton population, followed by Bacillariophyceae and Cyanophyceae. The plankton abundance was recorded highest in spring, followed by winter, and the least reported in monsoon season. The high average percent contribution of Aulacoseira, Oscillatoria, and Spirogyra species is well represented through SIMPER analysis. In addition, the Shannon–Wiener index (H) was calculated to determine plankton diversity, and Pielous' Evenness index (E) was calculated to determine individual distribution within a community whereas Margalef’s Richness index showed species richness of the study area. This qualitative and quantitative study will aid future research on the occurrence of plankton as well as the more trustworthy information generation on fish diet and feeding behaviors. The condition of planktons as bioindicators would indirectly provide an estimation of the ecosystem's natural state or amount of pollution.

Seasonal population fluctuation and life history in different temperatures of Myzus cerasi (Hemiptera: Aphididae) on cherry trees: a field and laboratory study.

This study determined the seasonal population fluctuation of Myzus cerasi (Fabricius) (Hemiptera: Aphididae) in cherry orchards and the effect of different temperatures on the life-history parameters of these aphids under laboratory conditions. Our field results showed that the population fluctuations and densities of M. cerasi on cherry trees were positively affected by the temperature increase between seasons. Also, our laboratory results showed that M. cerasi survived and reproduced at all temperatures tested under laboratory conditions. Female longevity was observed as 19.00 ± 2.38, 18.72 ± 0.49, and 12.59 ± 0.74 days, and fecundity was 10.14 ± 2.26, 9.36 ± 0.59, and 7.27 ± 0.84 offspring/female at 20, 25, and 30 °C, respectively. Although the highest net reproductive rate (R0) was observed numerically at 25 °C (7.80 offspring/female), there was no significant difference compared to 20 °C (7.10 offspring/female). The highest intrinsic rate of increase (r) and the highest finite rate of increase (λ) were calculated at 30 °C (0.15 ± 0.01 and 1.16 ± 0.01 day-1, respectively), and there was no significant difference compared to 25 °C. The mean generation time (T) of M. cerasi showed a significant difference at all temperatures tested and decreased from 22.59 ± 0.33 days at 20 °C to 12.78 ± 0.37 days at 30 °C. Consequently, our results revealed that the seasonal population fluctuation and the life history of M. cerasi in the field and laboratory conditions were affected significantly by different temperatures. Our data obtained in the field and the laboratory will contribute to the understanding of M. cerasi biology and to the management of the pest.

Maruca vitrata (Fabricius) (Lepidoptera: Crambidae): comparative infestation and seasonal population fluctuations on different pigeonpea genotypes in Punjab, India

Maruca vitrata (Fabricius) (Lepidoptera: Crambidae): comparative infestation and seasonal population fluctuations on different pigeonpea genotypes in Punjab, India

Seasonal variation in the relative strength of bottom-up <em>vs</em> top-down effects in pelagic cladoceran populations identified through contribution analysis of birth rate

Pelagic freshwater communities are characterized by the presence of strong trophic interactions, with the dominance of either food limitation (bottom-up effect) or predation pressure (top-down effect) alternating in time. Though this temporal variation should have a major impact on zooplankton dynamics, few studies have examined it. We consider here an approach that involves identifying signatures of food availability and size-selective fish predation based on the demographic characteristics of cladoceran populations. The relative strength of top-down vs bottom-up effects was assessed on short sampling intervals as contributions of the proportion of adults and fecundity, respectively, to the resulting change in birth rate. The dominant effect on each sampling interval was determined based on the absolute value of the ratio of those contributions (R). From previous experiments, we expected that under the dominant effect of food, R should be less than unity, while under fish predation it should be 1 < R < 3.4. We analyzed two datasets – one collected for a pelagic cladoceran community of three species, and another retrieved from the published data for Daphnia catawba in 1986. In the former case, the temporal variation in the dominant effect was assumed from the pattern of cladoceran populationdynamics as well as limited data on zooplankton consumption by planktivorous fish; in the latter case, the seasonal change in predation pressure by fish on the daphnids was known from the original data. Our results show that the probability density functions for R values from the two datasets indicate an increased probability of the ratio values associated with the abovementioned ranges, suggesting that both bottom-up and top-down effects should have been driving cladoceran population dynamics during the study periods. Based on the results of the Generalized Additive Models (GAMs), the fitted R values for the most abundant species from the first dataset - Bosmina longirostris - changed from the values indicative of strong food effect at the beginning of the study period to those indicative of strong top-down effect when fish with substantial numbers of bosminids in the gut were caught. In the second dataset, for the two time intervals associated with increased predation pressure by fish, the fitted R values were predominantly located between 1 and 3.4, as expected. For both datasets, our results indicate that contribution analysis of birth rate can be used as an informative, albeit preliminary, tool to identify trophic interactions driving zooplankton seasonal population fluctuations in freshwater communities.

Amik Ovasındaki pamuk bitkilerinde bitki tahtakurularının (Hemiptera: Miridae) mevsimsel popülasyon dalgalanmalarının değerlendirilmesi

Aims: Evaluation of seasonal population fluctuation of plants bugs (Lygus gemellatus (HerrichSchäffer), Lygus pratensis Linnaeus, and Creontiades pallidus (Rambur) (Hemiptera: Miridae) on cotton plants of Amik Plain.Methods and Results: The studies were carried out at fifty cotton fields located in Kırıkhan, Reyhanlı, Kumlu, Demirköprü and Uydukent districts of Amik Plain in Hatay province. Each of district contained 10 different cotton fields. The samplings were weekly taking by using a 45-cm diameter sweep-net, taking 25 (back-forth) sweep samples per site. The adults and nymphs of plant bugs were sorted out from plants materials, counted and recorded for each of the sampling locality and cotton field. A total of 1855 of plant bugs were caught by sweep-net at five (fifty cotton fields) sampled districts. The largest number of plants bugs were recorded in Demirköprü, followed by Reyhanlı, Uydukent, Kumlu and Kırıkhan. In addition, the highest mean of plant bugs were recorded on 8 October comparing to others sampling dates. Moreover, the largest amount of plants bugs were recorded in September, followed in October, August and July. In general, population density of plant bugs in Demirköprü, Reyhanlı, Uydukent and Kumlu districts were significantly higher than in Kırıkhan district.Conclusions: The highest number of plants bugs (Lygus gemellatus (HerrichSchäffer), Lygus pratensis Linnaeus, and Creontiades pallidus (Rambur) were recorded in Demirköprü, followed by Reyhanlı, Uydukent, Kumlu and Kırıkhan districts. Moreover, the largest number of plants bugs were recorded in September, followed in October, August and July.Significance and Impact of the Study: A total of 1855 of plant bugs were caught by sweep-net at five sampled districts. The highest number of plants bugs were recorded in Demirköprü, followed by Reyhanlı, Uydukent, Kumlu and Kırıkhan districts. Moreover, the largest amount of plants bugs were recorded in September, followed in October, August and July. In general, population density of plant bugs in Demirköprü, Reyhanlı, Uydukent and Kumlu districts were significantly higher than in Kırıkhan district.

Studies on seasonal population fluctuations and feeding damage induced by Dolichotetranychus floridanus (Banks) (Acari: Tenuipalpidae) on areca palms of Kerala, India

The state of Kerala is home to nearly 10,035 plant species as per the diversity scenario, thereby constituting 22% of the total plant diversity of India. Areca catechu L. (Arecales: Arecaceae) is an important plantation crop of Kerala with a multitude of economic utility and constitutes an important source of income for the people. The areca palms of Kerala are under the threat of many arthropod pests, of which tenuipalpid mites represent a major group causing severe damage to the foliage as well as the nuts. The present study reports a new host record for the tenuipalpid species viz Dolichotetranychus floridanus, which was found to infest the areca palms inducing severe damage to the developing nuts in various Areca plantations of Kerala. To understand the extent of damage induced by the species to its new host A. catechu, sampling was carried out monthly to collect nut samples from areca plantations distributed in two districts viz. Kozhikode and Malappuram of North Kerala, for a period of two years from 2013 and 2015. The collected nut samples were examined in the laboratory under a stereozoom microscope (MVNSZ-450) and data were collected on the population density of the mite as well as the qualitative aspects of feeding damage induced by the mite on the nuts. Results of population studies enabled to record peak population density of D. floridanus during July–August months. A positive correlation was found to exist between mite population and relative humidity and a negative correlation was recorded between mite population and temperature. The mean longevity of the females of this species at different temperatures and humidity conditions was recorded as 17.64 ± 0.17 days at 25 + 2oC & 80 + 5% RH, 13.64 ± 0.12 days at 30 + 2oC & 70 + 5% RH and 11.37 ± 0.12 days at 35 + 2oC & 60 + 5% RH. The feeding activity of the species was found to induce severe alterations, leading to the drying up of epidermal tissue, and formation of cracks at the affected region and the latter often served to permit the entry of fungal and bacterial pathogens, leading to tissue rot.

Surveillance of Aedes populations in Jiangsu Province in 2020

To investigate the seasonal Aedes population fluctuation and the resistance of Aedes populations to common insecticides in Jiangsu Province in 2020, so as to provide insights into vector-borne infectious diseases control. One village was randomly sampled from each of Xinbei District of Changzhou City and Zhangjiagang County of Suzhou City in southern Jiangsu Province, Hai'an County of Nantong City and Yandu District of Yancheng City in Central Jiangsu Province, and Suining County of Xuzhou City and Sihong County of Suqian City in northern Jiangsu Province during the period between May and October, 2020. A small ponding container was sampled, and larval Aedes mosquitoes were collected using straws once each in early and late stages of each month. All larvae were bred in laboratory to adults for population identification. In addition, larval breeding were observed in all small ponding containers in and out of 30 households that were randomly sampled from six surveillance sites, and the larval mosquito density was estimated using Breteau index. Larval A. albopictus mosquitoes were sampled around Cuiyuan New Village in Jintan District of Changzhou City, and bred in laboratory to the first offspring generation, and the susceptibility of adult female mosquitoes to deltamethrin, lambda-cyhalothrin, malathion, and propoxur was tested using the filter-paper bioassay recommended by WHO. A total of 1 165 larval Aedes mosquitoes were captured from small ponding containers in six surveillance sites of Jiangsu Province in 2020, and all were identified as A. albopictus following eclosion. The largest number of Aedes larvae captured was found in July. A total of 1 152 households were investigated in six surveillance sites, and the mean Breteau indexes were 9.58, 13.20, 13.71, 13.20, 12.18 and 5.58 from May to October, respectively, while a high Aedes transmission risk was seen in Xinbei District of Changzhou City, with a higher Breteau index than in Suining (H = 23.667, Padjusted = 0.001) and Sihong (H = 22.500, Padjusted = 0.003) counties. The field-captured A. albopictus from Cuiyuan New Village in Jintan District of Changzhou City remained sensitive to malathion, but was resistant to propoxur, and developed high-level resistance to deltamethrin and lambda-cyhalothrin. A. albopictus was present in southern, central and northern Jiangsu Province in 2020, and the larval density peaked in July. A. albopictus captured from Cuiyuan New Village in Jintan District of Changzhou City has developed high-level resistance to pyrethroid pesticides.

Seasonal Amphibian Species Richness and Population Fluctuations at Powdermill Nature Reserve, Pennsylvania, U.S.A.

Amphibians are a highly vulnerable taxonomic group that have suffered population declines worldwide. As amphibians serve critical links between trophic levels and facilitate nutrient recycling, it is critical to understand how their species richness, abundance, and phenology shift over time. Because amphibian populations naturally fluctuate, short-term monitoring can provide insight into how amphibian communities respond to proximate changes in weather conditions, which is helpful for predicting long-term responses to climate change. We used pitfall traps to examine interannual variation of the amphibian community at Powdermill Nature Reserve (PNR) in Pennsylvania during 2020–2021 to provide critical details for future long-term monitoring. Mean monthly temperature and precipitation did not vary significantly between years, but monthly captures per sampling effort declined and monthly biomass per sampling effort increased from 2020 to 2021. Despite a lack of significant relationships between total amphibian captures and temperature and precipitation, peak abundance shifted earlier, and individuals were larger in 2021 compared to 2020. Interestingly, individual species biomass was predicted by an interaction between temperature and precipitation, suggesting individual species will vary in vulnerability to climate change, but the amphibian community as a whole at PNR is resilient to minor fluctuations in temperature and precipitation.

Exploring the impacts of tourism and weather on water consumption at different spatiotemporal scales: evidence from a coastal area on the Adriatic Sea (northern Italy)

Abstract The growth of tourism in the last decades has left behind a significant footprint on water resources, which is particularly evident in the regions affected by water scarcity or consistent seasonal population fluctuations. However, only limited efforts were spent in evaluating the effects of tourism on water consumption with regard to specific non-residential users such as bathing facilities. The current work aimed at providing an insight into the effects of seaside tourism on water consumption in a case study coastal area in northern Italy that is typically subjected to high tourist fluctuations throughout the year. Analyses were carried out at multiple spatiotemporal scales—from urban to user level, and from yearly to daily scale—by exploiting hourly flow data collected at the inflow points of the area and at some touristic users (i.e. nine bathing facilities and a holiday home). In addition, the impact of weather—temperature and rainfall—on water use was explored. The study revealed consistent inflow fluctuations in the area concerned based on tourism (with a ratio between the maximum and minimum monthly average inflow of about 15.7) and demonstrated that the touristic component of water inflow was considerably higher than the residential component at the height of tourist season (i.e., 176 L/s against 42 L/s). Moreover, significant variations in the water inflow due to tourism and weather were also observed on a daily scale, along with considerable water consumption fluctuations in bathing facilities.

Malatya ili kayısı bahçelerinde Capnodis tenebrionis L. ve Capnodis carbonaria L. (Coleoptera: Buprestidae) türlerinin mevsimsel popülasyon yoğunluğu ve zarar oranları

Aims: Seasonal population fluctuations and damage rates of Capnodis tenebrionis L. and Capnodis carbonaria L. (Coleoptera: Buprestidae) in apricot orchards in Malatya province.Methods and Results: The study was conducted in 2010-2011 in thirteen apricot orchards in Akçadağ, Battalgazi and Doğanşehir districts of Malatya province. The study was carried out in seven and six apricot orchards in 2010 and 2011 respectively. In both years, the sampled apricot orchards were visited every week and counts were done by visual inspection method. After two years of the study, the population density of pest varied between each sampling year. A total of 1020 Capnodis adults were collected in 2010 from all the sampling areas. Among these, 805 were C. tenebrionis (688♂:117♀) and 215 were C. carbonaria (193♂:22♀). The first adult male and female emergence for C. tenebrionis was observed on 27th April and 18th May in 2010 respectively. For C. carbonaria first male and female emergence was observed on 22nd June and 20th July respectively. A total of 1170 Capnodis adults were collected in 2011 from all the sampling areas. Among these, 903 were C. tenebrionis (790♂:113♀) and 267 were C. carbonaria (225♂:42♀). The first adult male and female emergence for C. tenebrionis was observed on 23rd April and 30th April in 2011 respectively.Conclusions: In 2010, the largest percentages of C. tenebrionis male were collected in August, July and September, while those of its female were collected in August, September and July. The highest number of C. carbonaria male and female were collected in August, September and July. In 2011, the largest percentages of C. tenebrionis male and female were collected in July, August, September and June. The largest percentages of C. carbonaria male were collected in July, August, September and June, while those of its female were collected in July, August and June.Significance and Impact of the Study: The higher number of C. tenebrionis was collected by visual inspection method. The higher number of C. tenebrionis was collected than C. carbonaria in both years. The damage rates were observed on various varieties between 0.7-30 % in 2010 and 1.3-30 % in 2011.

Male meiotic recombination rate varies with seasonal temperature fluctuations in wild populations of autotetraploid Arabidopsis arenosa.

Meiosis, the cell division by which eukaryotes produce haploid gametes, is essential for fertility in sexually reproducing species. This process is sensitive to temperature, and can fail outright at temperature extremes. At less extreme values, temperature affects the genome‐wide rate of homologous recombination, which has important implications for evolution and population genetics. Numerous studies in laboratory conditions have shown that recombination rate plasticity is common, perhaps nearly universal, among eukaryotes. These studies have also shown that variation in the length or timing of stresses can strongly affect results, raising the important question whether these findings translate to more variable field conditions. Moreover, lower or higher recombination rate could cause certain kinds of meiotic aberrations, especially in polyploid species—raising the additional question whether temperature fluctuations in field conditions cause problems. Here, we tested whether (1) recombination rate varies across a season in the wild in two natural populations of autotetraploid Arabidopsis arenosa, (2) whether recombination rate correlates with temperature fluctuations in nature, and (3) whether natural temperature fluctuations might cause meiotic aberrations. We found that plants in two genetically distinct populations showed a similar plastic response with recombination rate increases correlated with both high and low temperatures. In addition, increased recombination rate correlated with increased multivalent formation, especially at lower temperature, hinting that polyploids in particular may suffer meiotic problems in conditions they encounter in nature. Our results show that studies of recombination rate plasticity done in laboratory settings inform our understanding of what happens in nature.

Abundance of microarthropods population in different sites of Midnapore east coast of West Bengal, India

Soil represents one of the most important reservoirs of biodiversity. Soil fauna is an important reservoir of biodiversity and plays an essential role in several soil ecosystem functions; furthermore it is often used to provide soil quality indicators. An ecological study of microarthropods communities from East Midnapore coast, West Bengal, India was undertaken. Four different biotopes were studied over the course of 30 months. A total 44 species of soil microarthropods were studied in details with regard to seasonal population fluctuation, variation in their community structure, relationship with physiochemical parameters of soil, life cycle pattern and their functional role in the ecosystem.

Global analysis of the seasonal abundance of the invasive pest Drosophila suzukii reveal temperature extremes determine population activity potential.

The global pest spotted winged drosophila (Drosophila suzukii) continues to have a significant economic impact on fruit production in areas where it is established, in addition to newly invaded ranges. Management activities spanning national biosecurity responses to farm-scale pest control are limited by the inability to predict the timing and severity of seasonal outbreaks of D. suzukii and its climatic drivers. Here, we compiled and analysed data on international seasonal abundances for D. suzukii under different climates, crop types and management contexts to improve the predictability of seasonal population dynamics. In relating seasonal abundances to environmental predictors, specifically temperature, we found strong negative effects of exposure to high and low temperatures during the preceding month. Unlike most regional studies on D. suzukii phenology that focus on temperature in the physiological development range, we show that thermal extremes better explain seasonal population fluctuations. Although trap catches remain an indirect measure of infestations and must be interpreted carefully in terms of crop risk, our results should support monitoring programmes through enhanced knowledge of the climatic factors affecting D. suzukii population activity. The negative impact of high temperatures suggests that late-season management strategies focusing on manipulating crop microclimates to temperatures above 25 °C can reduce D. suzukii abundance. We show that early season abundance is modulated by climate, particularly the depth of cold extremes experienced in the preceding time interval. These associations may be further developed into early-season crop risk forecasts to support monitoring programs. © 2021 Society of Chemical Industry.

Seasonal Abundance and Population Fluctuation of Leucaena Tree Beetle, Acanthoscelides macrophthalmus (Schaeffer) (Coleoptera: Chrysomelidae: Bruchinae) and its Accompaniment Parasitoids

The data presented in this study provide some basic information regarding seasonal abundance and population fluctuation, the influence of temperature and relative humidity, monthly population and emergence percentages, time and peacks number, and emergence ratios of population density of each leucaena pods and seeds beetle, Acanthoscelides macrophthalmus and its accompaniment parasitoids (Dinarmus basalis Rondani and Lyrcus sp.) emerged from infested Leucaena leucocephala trees. Insects are abundant throughout the year. The highest monthly population of beetles recorded during November, followed by May and December, the highest population of parasitoids observed during February, followed by March and January (D. basalis) also January and August (Lyrcus sp.).Nine peaks for beetles are recoded, the higher peak observed at 4th week Nov. followed by 3rd week of May, then 4th week of January, the same number of peaks recorded for D. basalis parasitoid, the highest peak noticed at 3rd week of Jan. and March, whereas Lyrcus sp. parasitoid has 8 peaks, the higher found at 3rd week of Jan.General ratio of insect’s emergence was 1:0.384:0.047 (beetles: Dinarmus: lyrcus). Highest ratios between beetles: parasitoids noticed during February (1:2), July (1:1.774) and March. (1:1.287). The dominant weather factors (MaxTemp., Min.Temp. & RH%.) evidently showed effective changes in the population density of beetles and parasitoids during annual activity months. The correlation between parasitoids and beetles population differed during the different seasons. The current work shows that Dinarmus basalis (26.8% seasonal emergence) and Lyrcus sp. (3.3% seasonal emergence) parasitoids develop within infested leucaena seeds with A. macrophthalmus beetle. Numerous numbers of each beetle (69.9% seasonal emergence) and parasitoids (31.3% seasonal emergence) were observed throughout the year, therefore A. macrophthalmus beetles can be used as a substitute host for mass rearing of D. basalisparasitoids, which are biological agent to control stored seed bruchids.

Highly mobile seed predators contribute to interisland seed dispersal within an oceanic archipelago

Long‐distance dispersal (LDD) is an essential event for species colonization and expansion in oceanic island ecosystems. Endozoochory by birds is an important factor promoting the LDD of plant seeds, but its contribution to interisland seed dispersal is still unclear. Here, we show possible seed dispersal by a seed predator pigeon, the Japanese wood pigeon Columba janthina, among oceanic islands in the Izu archipelago, Japan. Although some previous studies showed that most seeds swallowed by this pigeon are crushed, intact seeds were found in 44.5% of pigeon feces, indicating the contribution of these birds to seed dispersal. Seasonal population fluctuations and movements by pigeons between neighbouring islands which are 4 km apart by pigeons can promote interisland seed dispersal. We found seeds from fruiting trees not located on the islands where the pigeon feces were collected, which could have been transported from another island. Although many tree species overlap their fruiting phenology with pigeon movement between islands, the seeds of only six species were dispersed by pigeons, and most of the dispersed seeds were from species with small seeds less than 1.5 mm in diameter. Fruit consumption and frequent interisland movement of Japanese wood pigeons might homogenize the distribution of plants with small seeds among neighboring islands. In contrast, their intensive seed consumption might disturb the recruitment of plants with large seeds and make their expansion to other islands difficult. Such effects of mutualistic (dispersal) and antagonistic (predation) interactions with highly mobile seed predators may modify plant distributions and gene flow in oceanic archipelagos.

Seasonal population fluctuation of foliar nematode, Aphelenchoides besseyi infecting Dendrobium nobile under Poly house condition

Seasonal population fluctuation of foliar nematode, Aphelenchoides besseyi infecting Dendrobium nobile under Poly house condition

Identification and seasonal distribution of mosquito species in Telangana state, India

An entomological study was conducted to determine species composition, relative abundance, and seasonal population fluctuation of mosquitoes. Thirty localities were randomly selected and sampled once in summer, monsoon and winter seasons for a period of three years. Adult mosquitoes were collected from in and around human dwellings and animal sheds using aspirator and flash light between 6 PM and 7:30 PM hrs and 06:00 AM and 7:00 AM hrs. Larvae were collected from ditches, rock pool and other domestic habitats, reared to formation of adults in the lab. A total of 18425 mosquitoes were collected. Five genera (Culex, Anopheles, Aedes, Mansonia and Armigeres) were found to be circulating. Further, with respect to habitat, more number of mosquitoes were observed around cattle sheds and houses. Culex quinquefasciatus occupies top place, followed by Aedes albopictus and Culex gelidus, Culex tritaeniorhynchus with respect to density, whereas Mansonia uniformis occupies last place. Culex quinquifasciatus is top again followed by Culex gelidus and Aedes albopictus, Mansonia uniformis is last again with respect to distribution. The vector species studied were Aedes aegypti, Aedes albopictus for chikungunya and dengue, Anopheles stephensi, Anopheles culicifacies for malaria, Culex tritaeniorhynchus for Japanese encephalitis and Culex quiquefasciatus for lymphatic filaria.

Population dynamics of Scutylenchus rugosus under cultivation of maize and wheat and survival in dry fallow conditions

Summary The ectoparasitic nematode, Scutylenchus rugosus, is common in Europe and Asia, feeding on several plant species and limiting productivity. Its seasonal population fluctuation was monitored on maize and wheat crops, in glasshouse and open field conditions, respectively. Its survival in the absence of a host plant was also investigated in a microplot field trial. The population of S. rugosus increased gradually during 4 months of maize growth in glasshouse conditions, and more than 50% increase occurred during the second month after sowing. Under wheat growth, in open field conditions, the lowest population was observed during July, 1 month after wheat harvesting, and the highest in August, after the first post-harvest irrigation. About 50% of the nematode population survived after a 5-month period of drought in the absence of a host and the percentage of surviving nematodes was greater under a dry soil regime than under a dry-wet regime. Most of the inactive S. rugosus were adults. After 24 h of soil wetting, most inactive nematodes resumed their activity and the optimum temperature for activation was 25°C.

Unravelling the spatio-temporal variation of zooplankton community from the river Matla in the Sundarbans Estuarine System, India

Zooplankton is an important bioindicator of ecosystem functioning. Knowledge of the seasonal fluctuation in the zooplankton population in estuarine waters of the Indian Sundarbans is rather limited. In the present study, we analysed the community structure of zooplankton assemblages and their spatio-temporal variations based on different multivariate statistics and indicator value analysis. A total of 56 taxa were identified and the density was primarily dominated by planktonic copepods and few meroplankton communities during four sampling seasons. The most abundant species were: Acartia spinicauda, Acartia sp., Bestiolina similis, Euterpina acutifrons, Labidocera acuta, Paracalanus aculeatus, Paracalanus parvus and Paracalanus indicus. Canonical Correspondence Analysis highlighted that temperature, pH, DO, salinity and nutrients were the prevailing environmental parameters associated with significant spatio-temporal changes of zooplankton distribution in this area. The highest abundance of zooplankton was recorded in winter, followed by monsoon, summer and spring. Throughout the study period, different zooplankton indices were observed in good condition. Seasonal occurrence of dominant zooplankton with high IndVal index was markedly observed and it might be used as a potential bioindicator for a particular season and environmental condition in this estuarine complex. The results of this study provide evidence for the presence of warm water species in the estuarine waters of the Indian Sundarbans and can be a clear indication of climate change-mediated elevated temperature in the estuarine system. Our results underscore the high diversity of zooplankton from mangrove dominated estuarine complex and emphasize the need for long-term monitoring in ecologically fragile ecosystems like the Sundarbans Estuarine System.

Seasonal Population Fluctuations in Some Non-Passeriformes at Marala Head, Pakistan

Point count method was used to determine the relative abundance of non-passerine species at Marala wetlands (District Sialkot, Pakistan) during different calendar months between October, 2000 and September, 2001. Six species (Hoopoe, Lapwing, Spotted Owlet, Osprey, Indian Roller and Indian Nightjar) were recorded. Osprey and Spotted Owlet appearing in smaller numbers and Red Wattled Lapwing as a dominant resident. All the species were resident with some variation in population sizes during different seasons, though Osprey was a winter visitor.