Decrease In Population Density Research Articles

Genetic variability of the striped venus Chamelea gallina in the northern Adriatic Sea

Chamelea gallina is a valuable commercial species in the Mediterranean Sea. The strong fishing pressure on C. gallina in the northern and central Adriatic Sea has paralleled a clear-cut decrease in clam population density and the occurrence of several irregular mortality events. Despite the commercial interest in this species, nothing is known about its genetic sub-structuring at the geographic and/or temporal scale, nor its levels of genetic variability. Analyzing microsatellite genotypes for samples collected in the Adriatic Sea, we detected large geographic genetic homogeneity with gene flow guided by broad scale circulation in the north-south direction. Our results also indicate weak genetic differentiation among size classes at the local and temporal scale. These small genetic differences might be determined by variability of local circulation and reproductive success, partial overlapping generations and high larval mortality rates as suggested by our estimates of the effective number of breeders. In fact, global effective population size estimates over multiple generations are medium-high, but a low number of breeders are responsible for the small clams size class recruitment. Notwithstanding, it was not possible to detect signatures of bottleneck. Future efforts in fishery management should aim to maintain genetic diversity – essential to the long-term sustainability of the resource – and limit effective population size fluctuations while considering the need to improve water quality to avoid mass mortality events.

The effect of thinning and cue:density ratio on risk perception by Rana dalmatina tadpoles

The “risk assessment hypothesis” considers prey density as an important variable to properly assess the actual level of risk, and predicts that, when the ratio between predator cue concentration and prey density is constant, the level of risk perceived by prey is the same. All previous studies which tested this hypothesis with Anurans manipulated density by placing tadpoles into experimental tubs at fixed group sizes. As predation is a process that produces a progressive decrease in prey density, i.e. “thinning”, prey may respond to the rate of group size reduction rather than the absolute number of conspecifics in a given place at a given time. To test if Rana dalmatina tadpoles perceive the progressive decrease in population density due to predation and are able to use this information to fine-tune anti-predator responses, we combined thinning with a constant cue:density ratio and evaluated how these two types of information affected the level of activity of tadpoles. Our results showed no effect of density reduction on prey level of activity, and thinning did not interact with cue intensity to modify tadpoles’ behaviour. However, we observed no difference in tadpole behavioural responses between treatments with the same cue:density ratio.

Variability in size at maturity and reproductive season of queen conch Lobatus gigas (Gastropoda: Strombidae) in the Wider Caribbean Region

Queen conch (Lobatus gigas), is an economically and culturally important marine gastropod. The species is subject to extensive exploitation throughout large parts of the Caribbean which has led to a decrease in population densities across much of the species’ distribution range. Hence, there is a need for protective measures to safeguard the reproductive stock. This requires a better estimation of its size at maturity, which is best quantified as the thickness of the lip that the shell develops after reaching its maximum length. The lip thickness at 50% maturity (LT50) was determined using a logistic and an accumulation model, from seven representative location of distribution of this species in the Wider Caribbean Region. LT50 of both females (7–14 mm) and males (4–11.5 mm) varied between different locations in the Caribbean, although it did not correspond with variation in water temperature. In most cases females had a larger LT50 than males indicating sexual dimorphism. LT50 values estimated with the logistic model were smaller (7–14 mm for females, 4–11.5 mm for males) than values estimated with the accumulation model (13–26 mm for females, 16–24 mm for males), showing an overestimation of LT50 in queen conch in previous studies which used the accumulation model to estimate LT50. Locations with a relatively high variation in water temperature had a significantly shorter reproductive season. The implementation of adequate minimum size regulation based on lip thickness (ca. 15 mm) and a Caribbean wide seasonal closure (May–September) using the most recent biological information from this study, taking into consideration the local differences in LT50 and reproductive season, will assist in developing a long term sustainable queen conch fishery in the Caribbean.

Aquatic ecosystem health and trophic status classification of the Bitter Lakes along the main connecting link between the Red Sea and the Mediterranean.

The Bitter Lakes are the most significant water bodies of the Suez Canal, comprising 85% of the water volume, but spreading over only 24% of the length of the canal. The present study aims at investigation of the trophic status of the Bitter Lakes employing various trophic state indices, biotic and abiotic parameters, thus reporting the health of the Lake ecosystem according to the internationally accepted classification criteria’s. The composition and abundance of phytoplankton with a dominance of diatoms and a decreased population density of 4315–7376 ind. l−1 reflect the oligotrophic nature of this water body. The intense growth of diatoms in the Bitter Lakes depends on silicate availability, in addition to nitrate and phosphate. If the trophic state index (TSI) is applied to the lakes under study it records that the Bitter Lakes have an index under 40. Moreover, in the total chlorophyll-a measurements of 0.35–0.96 µg l−1 there are more indicative of little algal biomass and lower biological productivity. At 0.76–2.3 µg l−1, meanwhile, the low quantity of Phosphorus is a further measure of low biological productivity. In the Bitter Lakes, TN/TP ratios are high and recorded 147.4, and 184.7 for minimum and maximum ratios, respectively. These values indicate that in Bitter lakes, the limiting nutrient is phosphorus and confirm the oligotrophic status of the Bitter Lakes. The latter conclusion is supported by Secchi disc water clarity measurements, showing that light can penetrate, and thus algae can photosynthesize, as deep as >13 m. This study, therefore, showed that the Bitter Lakes of the Suez Canal exhibit oligotrophic conditions with clear water, low productivity and with no algal blooming.

Analysing urban sprawl and land consumption patterns in major capital cities in the Himalayan region using geoinformatics

In the present study, spatio-temporal urban sprawl and land consumption patterns were analysed in seven capital cities located in the Himalayan region during 1972, 1991 and 2015 using multi-temporal satellite images. The study exhibits that capital Himalayan cities experienced rapid growth (830.92%) with high population increase (333.45%) during the observation period (1972–2015). The significant urban growth was observed in the cities of western and middle Himalayan region viz., Srinagar (9.36 km2–142.19 km2), Kathmandu (11.38 km2–92.58 km2) and Dehradun (4.1 km2–50.09 km2) in the higher altitudes due to remarkable increase in the population (0.5–1 million persons) during 1972–2015. On the contrary, Itanagar (7.19 km2), Gangtok (7.09 km2), Shimla (3.04 km2) and Thimphu (2.93 km2) observed less urban growth with moderate to low population growth (i.e., 0.05 to 0.15 million persons). The Shannon entropy based study exhibits that the cities viz., Kathmandu, Gangtok and Itanagar observed comparatively more dispersed urban growth during later period (1991–2015) as compared to the previous period (1972–1991) whereas, the remaining cities observed comparatively less dispersed urban growth during later period. The temporal land consumption pattern exhibits low density urban growth in Srinagar, Dehradun and Kathmandu, as observed with decrease in population density and increasing land consumption during 1972–2015 as compared to other cities, wherein urban densification was evident with increase in population density and decrease in land consumption. The cities in central and western Himalayan region observed high urban growth as compared to cities in eastern Himalayan region. The result shows that the capital cities contributes insignificant proportion (0.5%; 314 km2) of urban area in Himalayan region and accommodating large (ca. 4 million) population during 2015. The study indicates unplanned and haphazard growth in all capital Himalayan cities, leading towards urban densification as well as dispersion in the periphery with varied pattern and intensity. The specific trends and patterns of urban and population growth are governed by geographical as well as socio-economic-political factors at local to regional scale. The high population pressure induced higher risk to the urban residents as well as constrained urban growth over higher vulnerable zones. The study necessitates implementation of suitable urban planning methods considering socio-economic and physico-cultural characteristics of the region.

Red king crab (Paralithodes camtschaticus) fisheries in Russian waters: historical review and present status

The red king crab (Paralithodes camtschaticus) is a highly valued delicacy on the international market and currently contributes significantly to the income from fisheries in the regions where it is harvested. Russian income from red king crab export is $200–250 million per year. We review both the biology and fishery of the two largest populations of this species in Russia, i.e., in western Kamchatka (Sea of Okhotsk) and in the Barents Sea. The latter was established in the mid-1990s after introduction of red king crab to the area in the 1960s. The Barents Sea crabs are larger, grow faster and mature earlier than the crabs from the Sea of Okhotsk owing to more favorable temperature conditions in the Barents Sea. Additionally, we provide fishery information for the Prymorie population of red king crab (Sea of Japan) that remains depressed and closed for commercial fishery at present. Although the fishery period of red king crab in western Kamchatka is much longer than in the Barents Sea (1930–present time vs. 2004–present time), similar patterns were observed for the exploited king crab populations. High annual landings led to a pronounced decrease in population density and total abundance that, in turn, led to closures or some limitations of fisheries. Subsequent rehabilitations of the populations provided an opportunity for reopening of the fisheries and further exploration of red king crab populations under sustainable management. The main reason explaining a decline in red king crab populations both in the North Pacific and in the Barents Sea is high, mainly illegal, fishing pressure. Sustainable harvest strategies for the fisheries could prevent negative scenarios (overfishing) in the future.

Application of underpasses to expand nature reserves: responses of a critically endangered marsupial, the woylie, Bettongia penicillata

Despite the conservation benefits that it yields, fencing for conservation presents management challenges. One major problem is that populations in fenced reserves can increase beyond the carrying capacity of the area. This was a concern for a population of woylies, Bettongia penicillata ogilbyi at Whiteman Park’s fenced reserve in Western Australia. Two underpasses were constructed linking the original reserve to a larger, newly established fenced reserve to provide the resident woylies with opportunities for expansion. Underpasses were monitored with microchip readers and infrared cameras. Woylies were also tracked using GPS technology to determine if they would use the underpasses to disperse into the new area and if, in doing so, there would be a decrease in population density and associated expansion in home range size of woylies in the original reserve. The use of underpasses by woylies was clearly demonstrated with 1657 crossings by at least 51 individuals. Contrary to expectations most woylies used the underpasses to move between the two reserves, rather than permanently dispersing into the new area. Although there was an apparent decrease in population density from 3.4±0.8/ha (S.E.) to 1.36±0.08/ha (S.E.), only the core home range of males increased by 38% after the underpasses were opened. However, woylies using the underpass did shift their home ranges to incorporate the underpasses and parts of the second reserve. Findings from this study demonstrate that the use of underpasses to connect reserves separated by roads or other barriers is an effective method to manage populations limited in their expansion by natural or anthropogenic barriers.

Biofuel consumption, biodiversity, and the environmental Kuznets curve: trivariate analysis in a panel of biofuel consuming countries.

This study examined the relationship between biofuel consumption, forest biodiversity, and a set of national scale indicators of per capita income, foreign direct investment (FDI) inflows, trade openness, and population density with a panel data of 12 biofuels consuming countries for a period of 2000 to 2013. The study used Global Environmental Facility (GEF) biodiversity benefits index and forest biodiversity index in an environmental Kuznets curve (EKC) framework. The results confirmed an inverted U-shaped relationship between GEF biodiversity index and per capita income, while there is flat/no relationship between carbon emissions and economic growth, and between forest biodiversity and economic growth models. FDI inflows and trade openness both reduce carbon emissions while population density and biofuel consumption increase carbon emissions and decrease GEF biodiversity index. Trade openness supports to increases GEF biodiversity index while it decreases forest biodiversity index and biofuel consumption in a region.

Seven-year monitoring of pyrethroid resistance in the pollen beetle (Brassicogethes aeneus F.) during implementation of insect resistance management.

An increase in the spread of pyrethroid resistance in the pollen beetle has been documented in many European countries. Pyrethroid resistance in the pollen beetle in the Czech Republic has been detected using a topical application bioassay. Resistance monitoring has been carried out during the implementation of insect resistance management. The susceptibilities of nine pollen beetle populations to four pyrethroids in 2009 - 2015 in the Czech Republic are presented in this paper. The highest resistance ratio (RR) values [based on the lethal dose for 50% of the population (LD50 )] obtained for deltamethrin, lambda-cyhalothrin, tau-fluvalinate and etofenprox were 500, 299, 108 and 66.9, respectively. Pollen beetle mortality after application of deltamethrin or lambda-cyhalothrin gradually decreased from 2009 to 2013. High cross-resistance between lambda-cyhalothrin and deltamethrin and low cross-resistance between lambda-cyhalothrin and etofenprox were demonstrated. A kdr mutation known to cause resistance in the pollen beetle was not detected. A high level of resistance was recorded in most of the nine populations of the pollen beetle in 2013. In the following 2 years, a decrease in resistance associated with a population density decrease of the pollen beetle was observed in all nine populations as a result of insect resistance management based on pyrethroid reduction in winter oilseed rape. © 2017 Society of Chemical Industry.

Microstructure – Toughness relationships in sub-zero treated and tempered Vanadis 6 steel compared to conventional treatment

The influence of sub-zero treatment and tempering on the microstructure, flexural strength, and fracture toughness of Cr-V ledeburitic steel was examined with reference to the same material processed without the sub-zero period. The experimental results lead to the following findings: (i) Sub-zero treatment induces a considerable reduction of the amount of retained austenite, refinement of newly formed martensite, and increase in population density of small globular carbides. (ii) The hardness is improved by the sub-zero treatment in the prior-to-tempering state as well as in the state after low-temperature tempering; after high-temperature tempering, the situation is changed in favour of conventionally quenched specimens, whereas the secondary hardening peak disappears in sub-zero treated steel. This is due to combined effect of the population density decrease of small globular carbides, accelerated decomposition rate of retained austenite, coarsening of cementitic precipitates, and retardation of precipitation of stable M7C3 carbide. (iii) There is almost no effect of sub-zero treatment on the flexural strength in the low-temperature tempering range but this property is improved after tempering into the secondary hardening range. Sub-zero treatment causes a worsening of fracture toughness after low-temperature tempering but a slight improvement after tempering in the secondary hardening temperature range.

Impact of feeding essential oils on feed fermentation and rumen microbial profile in crossbred cattle calves

The essential oils (EOs), viz. ajwain (Trachyspermum copticum, AjO), lemongrass (Cymbopogon citratus, LO), clove (Syzygium aromaticum) oleoresin (CO) and a blend (BEO) of the 3 were screened using in vitro gas production test for their potential to mitigate methane production. Inclusion of all the 3 EOs and BEO at the rate of 1.0 μl/ml of incubation medium resulted in a depression in total gas and methane production with a maximum reduction of 91.6 and 97.2% by BEO. Feed digestibility was significantly reduced by all the 3 EOs and BEO as compared to control but was similar among the 4 treatments. The level of total volatile fatty acids, acetic and propionic acids in fermented medium was significantly decreased by inclusion of EOs and BEO. Based on the results of these results, BEO was selected for the feeding trial. Ten crossbred cattle calves (average body weight, 68±5 kg) were divided into 2 groups of 5 animals each and subjected to 2 treatments i.e. diet without (control) and with BEO @ 0.1 mL/kg BW (treated). The diet comprised concentrate mixture (21.9%, CP and 71.1% TDN) and wheat straw in 50:50 ratio. There was no impact of BEO feeding on rumen metabolites and enzyme profile. As assessed by real time PCR, the population of protozoa and Ruminococcus albus reduced, whereas, bacteria, fungi, Fibrobacter succinogenes and Ruminococcus flavefaciens remained unaffected by BEO feeding. Methanogen population density tended to reduce by BEO feeding. The results clearly indicated that BEO exhibited antimethanogenic activity in in vitro system. By feeding BEO, the decreased population density of protozoa and methanogens in the rumen, the 2 major microbial groups involved in methanogenesis, also supported antimethnogenic property of BEO.

Habitat Selection, Interspecific Competition, and Coexistence of a Habitat Generalist and Specialist in Temperate Rainforest of Southeastern Alaska

Communities include habitat generalists whose resource use overlaps specialists. Habitat selection is a mechanism that allows competing species to coexist. Interspecific competition can facilitate coexistence directly or through promoting differential habitat selection. Habitat selection and interspecific competition can vary with population density; however, their roles in determining relative abundance of species across habitat space are poorly understood. We studied Peromyscus keeni, which flourishes in a range of habitats in southeastern Alaska, and Myodes gapperi, a specialist of mature coniferous forests in western North America, to elucidate how these mechanisms may facilitate coexistence in temperate rainforest. We used stepwise multiple regressions of minimum known alive (standardized to unit variance) across 1 ha grids during spring 1999–2000 and autumn 1998–2000 to determine contributions each variable, in each significant regression model, made to the variance in abundance for each species. We determined relative contributions of interspecific competition versus habitat selection in explaining species' habitat use among four different types of rainforest habitat. Intensity of interspecific competition (both directions) varied with population density and season. Habitat variables, rather than interspecific competition, explained variation in species' abundance at population peaks when intraspecific competition would be intense. Interspecific competition, with habitat, was significant at all other times. Our findings suggest habitat selection and interspecific competition explain variation in the abundance of both species among habitats, but contributions vary seasonally and with density. During spring, interspecific competition seemingly plays a greater role at higher densities, but during autumn interspecific competition increases its relative contribution as population density decreases.

Long-term impact of socio-economic changes on agricultural land use in the Polish Carpathians

The impact of socio-economic changes on land use on the period 1846–2009 are studied in village of Ochotnica (105km2) and the Jaszcze and Jamne catchments in the Polish Carpathians. The analysis of maps, aerial photos, historical and census reports indicates that during the investigated period the forest area in Ochotnica increased by 77% and in the Jaszcze and Jamne catchments by 29% and 43%, respectively and cultivated land decreased by 94% in both catchments. The population density increased from 33 to more than 50people/km2, while employment in agriculture decreased from 98% to below 30%. The analysed period shows diverging trends of land use, referring to the three stages of socio-economic development in the Polish Carpathians. Until World War II, agricultural land contribution was the highest throughout the history of human activity. After World War II, a communist maintenance system of the land use structure was inherited from the past. A free market economy, introduced after 1989, forced the largest increase in forest area since the first colonisation of the Gorce Mountains. In contrast to the mid-mountains of Western Europe, a decrease in population density did not accompany forest expansion, nor did a dominance of small farms in the ownership system.

Rapid increase in genetic diversity in an endemic Patagonian tuco-tuco following a recent volcanic eruption

Catastrophic natural events can have profound impacts on patterns of genetic diversity. Due to the typically unpredictable nature of such phenomena, however, few studies have been able to directly compare patterns of diversity before and after natural catastrophic events. Here, we examine the impacts of a recent volcanic eruption in southern Chile on genetic variation in the colonial tuco-tuco (Ctenomys sociabilis), a subterranean species of rodent endemic to the area most affected by the June 2011 eruption of the Puyehue-Cordon Caulle volcanic complex. To provide a comparative context for interpreting changes in genetic variation in this species, we also analyze the effects of this eruption on genetic variation in the geographically proximate but more widely distributed Patagonian tuco-tuco (C. haigi). Our analyses indicate that while both C. sociabilis and C. haigi displayed significant post-eruption decreases in population density, the apparent impacts of the eruption on genetic diversity differed between species. In particular, genetic diversity at multiple microsatellite loci increased in C. sociabilis after the eruption while no comparable post-eruption increase in C. haigi was observed at these loci. No changes in post-eruption diversity at the mitochondrial cytochrome b locus were detected for either species. To place these findings in a larger spatiotemporal context, we compared our results for C. sociabilis to genetic data from additional modern and ancient populations of this species. These comparisons, combined with Bayesian serial coalescent modeling, suggest that post-eruption gene flow from nearby populations represents the most probable explanation for the apparent increase in post-eruption microsatellite diversity in C. sociabilis. Thus, detailed comparisons of pre- and post-eruption populations provide important insights into not only the genetic consequences of a natural catastrophic event, but also the demographic processes by which these changes in genetic diversity likely occurred.

Investigating brushtail possum (Trichosurus vulpecula) home-range size determinants in a New Zealand native forest

Context The Australian brushtail possums (Trichosurus vulpecula) introduction to New Zealand has exacted a heavy toll on native biodiversity and presented the country with its greatest wildlife reservoir host for bovine tuberculosis (TB). Management efforts to control both possums and TB have been ongoing for decades, and the biology of possums has been studied extensively in Australia and New Zealand over the past 50 years; however, we still do not have a clear understanding of its home-range dynamics. Aims To investigate determinants of home range size by using a uniquely large dataset in the Orongorongo Valley, a highly monitored research area in New Zealand and compare our findings with those of other studies. Methods Possum density was estimated, for subpopulations on four 13-ha cage-trap grids, by the spatially explicit capture–mark–recapture analysis of trapping data from 10 consecutive months. Home ranges were estimated from trap locations using a 100% minimum convex polygon (MCP) method for 348 individuals and analysed with respect to grid, age and sex. Key results Mean (standard error) possum density, estimated as 4.87 (0.19), 6.92 (0.29), 4.08 (0.21) and 4.20 (0.19) ha–1 for the four grids, was significantly negatively correlated with mean MCP home-range size. Grid, age, and the interaction of age and sex were significantly related to home-range size. Older possums had larger home ranges than did younger possums. When ‘juvenile cohort’ and ‘adult cohort’ data were analysed separately, to investigate the significant interaction, males in the ‘adult cohort’ had significantly larger home ranges than did females, with the grid effect still being apparent, whereas neither sex nor grid effects were significant for the ‘juvenile cohort’. Conclusions Our findings indicate that, in addition to density, age and sex are likely to be consistent determinants of possum home-range size, but their influences may be masked in some studies by the complexity of wild-population dynamics. Implications Our findings have strong implications regarding both disease transmission among possums and possum management. The fact that adult males occupy larger home ranges and the understanding that possum home range increases as population density decreases are an indication that males may be the primary drivers of disease transmission in possum populations. The understanding that possum home range increases as population density decreases could be a direct reflection of the ability of TB to persist in the wild that counteracts current management procedures. If individuals, and particularly males, infected with TB can withstand control measures, their ensuing home-range expansion will result in possible bacteria spread in both the expanded area of habitation and new individuals becoming subjected to infection (both immigrant possums and other control survivors). Therefore, managers should consider potential approaches for luring possum males in control operations.

The Expansion of Densely Inhabited Districts in a Megacity - Case of Tokyo

Understanding the patterns of human concentrations within megacities is of fundamental importance to our understanding of megacity dynamics, and for megacity management and policy making. This study presents an updated investigation of the historical expansion of densely inhabited districts (DIDs) in the world's largest megacity, Tokyo. Long-term DID data (1960-2010) at 5- year intervals were analyzed in a geographic information systems framework. Results show that Tokyo completed rapid growth phase and is now in a maturity phase with minimal growth. Extension was the main form of expansion, although fragmented growth in the form of patches was also noted. The rate of DID expansion was strongly related to economic trends. However the direction and shape of expansion was influenced much by geographic and policy related factors. West and southern directions had earlier and greater expansion, likely related to the historical Tōkaidō corridor. Over 95% of all DIDs are located within 4km distance from a railway line. The coastline and distance from the CBD had some modifying influence. During the course of expansion, there was substantial decrease of population density in the inner wards. Future trends in Tokyo's DIDs will be greatly influenced by aging demographic trends. This study therefore shows that megacity spatial expansion is a dynamic process influenced by various processes whose roles vary over time.

Stabilization of a salamander moving hybrid zone.

When related species meet upon postglacial range expansion, hybrid zones are frequently formed. Theory predicts that such zones may move over the landscape until equilibrium conditions are reached. One hybrid zone observed to be moving in historical times (1950–1979) is that of the pond‐breeding salamanders Triturus cristatus and Triturus marmoratus in western France. We identified the ecological correlates of the species hybrid zone as elevation, forestation, and hedgerows favoring the more terrestrial T. marmoratus and pond density favoring the more aquatic T. cristatus. The past movement of the zone of ca. 30 km over three decades has probably been driven by the drastic postwar reduction of the “bocage” hedgerow landscape, favoring T. cristatus over T. marmoratus. No further hybrid zone movement was observed from 1979 to the present. To explain the changing dynamics of the hybrid zone, we propose that it stalled, either because an equilibrium was found at an altitude of ca. 140 m a.s.l. or due to pond loss and decreased population densities. While we cannot rule out the former explanation, we found support for the latter. Under agricultural intensification, ponds in the study area are lost at an unprecedented rate of 5.5% per year, so that remaining Triturus populations are increasingly isolated, hampering dispersal and further hybrid zone movement.

Allee effect: the story behind the stabilization or extinction of microbial ecosystem.

A population exhibiting Allee effect shows a positive correlation between population fitness and population size or density. Allee effect decides the extinction or conservation of a microbial population and thus appears to be an important criterion in population ecology. The underlying factor of Allee effect that decides the stabilization and extinction of a particular population density is the threshold or the critical density of their abundance. According to Allee, microbial populations exhibit a definite, critical or threshold density, beyond which the population fitness of a particular population increases with the rise in population density and below it, the population fitness goes down with the decrease in population density. In particular, microbial population displays advantageous traits such as biofilm formation, expression of virulence genes, spore formation and many more only at a high population density. It has also been observed that microorganisms exhibiting a lower population density undergo complete extinction from the residual microbial ecosystem. In reference to Allee effect, decrease in population density or size introduces deleterious mutations among the population density through genetic drift. Mutations are carried forward to successive generations resulting in its accumulation among the population density thus reducing its microbial fitness and thereby increasing the risk of extinction of a particular microbial population. However, when the microbial load is high, the chance of genetic drift is less, and through the process of biofilm formation, the cooperation existing among the microbial population increases that increases the microbial fitness. Thus, the high microbial population through the formation of microbial biofilm stabilizes the ecosystem by increasing fitness. Taken together, microbial fitness shows positive correlation with the ecosystem conservation and negative correlation with ecosystem extinction.

Localized removal affects white‐tailed deer space use and contacts

ABSTRACTTransmission and impact of infectious diseases can be altered if host social structure is disrupted by disease outbreaks or lethal management. Specifically, if remnants of depopulated groups join or increase contact with neighboring groups, between‐group transmission may increase even as population density decreases. We tested whether this phenomenon could apply to diseases of white‐tailed deer (Odocoileus virginianus) by using a before‐after‐control‐impact design. We monitored space use and contacts among adult female and juvenile deer in southern Illinois during 2011–2014; midway through each study season, we removed all members except 1 collared deer from centrally located groups and left control groups intact. After group removal, remnant adult females shortened duration of contacts with neighboring groups, whereas remnant juveniles responded with greater shifts in space use and appeared to join neighboring groups. Together, our study points to potential age‐specific responses of deer to social disruption, with evidence that juveniles respond in ways that could shift disease transmission dynamics toward frequency dependence. These findings highlight the need for focused research into the importance of social disruption in disease dynamics, and lend support for complete group removal (if possible) when culling for disease management. © 2016 The Wildlife Society.

Tourism in Austria: biodiversity, environmental sustainability, and growth issues.

This study examined the long-run and causal relationships between international tourism, biodiversity loss, environmental sustainability, and specific growth factors under the premises of sustainable tourism in Austria, by using a consistent time series data from 1975 to 2015. The results reveal that inbound tourism, per capita income, and population density affected the potential habitat area while population density largely affected the food production in a country. Inbound tourism and population density both deteriorate the environmental quality in a form of increasing carbon dioxide (CO2) emissions and fossil fuel energy consumption while per capita income reduces the fossil fuel energy consumption. Food exports increase per capita income, while food imports and population density both decrease economic growth. Inbound tourism and economic growth advance population density while forest area and food exports decrease the population density. The study supports growth-led tourism and growth-led food production in a country.