Potential Population Growth Research Articles

Potential impact of climate change on whiteflies and implications for the spread of vectored viruses

Whiteflies (Hemiptera: Aleyrodidae) are important insect pests causing serious damage to plants and transmitting hundreds of plant viruses. Climate change is expected to influence life history and trophic interactions among plants, whiteflies and their natural enemies. Here, we review the potential impacts of climate change on whiteflies and the likely consequences for agricultural systems. This review concludes that while climatic stress tends to negatively affect life history traits, the effects differ with the tolerance of the whiteflies and the amount of stress experienced. Whiteflies also differ in their adaptability. Better adapted species will likely experience increased distribution and abundance provided their tolerance limits are not exceeded, while species with lower tolerance and adaptation limits will suffer reduced fitness, which will have overall effects on their distribution and abundance in space and time. The majority of methods used to control whiteflies will still be useful especially if complementary methods are combined for maximum efficacy. Parasitism and predation rates of whitefly natural enemies could increase with temperature within the optimum ranges of the natural enemies, although life history traits and population growth potential are generally maximised below 30 °C. Changes in climatic suitability modifying the distribution and abundance of whiteflies, and environmental suitability for plant viruses, will likely affect epidemics of viral diseases. Greater efforts are required to improve understanding of the complex effects of climate change on multi-species and multi-trophic interactions in the agro-ecological systems inhabited by whiteflies, and to use this new knowledge to develop robust and climate-smart management strategies.

Optimizing release strategies: a stepping‐stone approach to reintroduction

AbstractEvaluation of alternative management strategies enables informed decisions to accelerate species recovery. For reintroductions, post‐release survival to reproductive age is a key parameter influencing population growth. Here, we trial a ‘stepping‐stone’ method to maximize the success of captive‐bred animals when the availability of more suitable wild‐born release candidates is limited. Our approach makes use of relatively safe and established wild populations to prepare captive‐bred individuals for eventual translocation to a final release destination, thus building resilience through establishment of multiple populations over time. We developed a novel multievent model integrating encounter history and biotelemetry data to evaluate reintroduction strategies for the critically endangered Vancouver Island marmot Marmota vancouverensis. We compared post‐release survival of 176 individuals (52 wild‐born, 47 captive‐bred marmots released directly to destinations, and 77 captive‐bred marmots released with a stepping‐stone approach). Survival estimates to prime breeding‐age (PBA), were then used to quantify expected success of potential release strategies. Our analysis indicates that post‐release survival varies by source population and release method, as well as age, season, year, and years since release. Conditional on an objective of maximizing survival to PBA, our results suggest that using wild‐born marmots for translocations as often as possible, and stepping‐stone captive‐bred marmots prior to final release, will result in the best outcomes. There was a 0.86 probability that survival to PBA was greater for captive‐bred marmots released as yearlings using a stepping‐stone approach (survival to PBA mode = 0.13, 95% CRI = 0.05–0.30) than for captive‐bred animals that were directly released to destination sites as one‐year‐olds (survival to PBA mode = 0.04, 95% CRI = 0.01–0.24). Consequently, the stepping‐stone approach yields much higher population establishment or growth potential than previous release strategies that used captive‐bred marmots. Optimizing the combination of release candidates, sites and timing can thereby increase the effectiveness of reintroductions.

Population growth and reproductive potential of five important fishes from the freshwater bodies of Bangladesh

Population growth (length-weight relationship), and reproductive potential (e.g. fecundity, and sex-ratio) of five important fish species (‘mola’: Amblypharyngodon mola, ‘puti’: Puntius sophore, ‘tengra’: Mystus vittatus, ‘shing’: Heteropneustes fossilis and ‘taki’: Channa punctatus) collected from two important fresh waters bodies (namely Hilna beel and Beel Kumari beel) Rajshahi, Bangladesh, were studied. Population growth pattern by length-weight relationship (W=aLb) for the species differed, and exhibited positive allometric growth (P. sophore in Hilna beel), isometric growth (A. mola and C. punctatus in Hilna beel) and negative allometric growth (M. vittatus & H. fossilis in Hilna beel and A. mola, P. sophore, M. vittatus, C. punctatus & H. fossilis in Beel Kumari beel). The results denoted that the fecundity of mature females followed non-linear relationship (F=aLb) with total length and exhibited positive allometric growth (b>3) with some exception (A. mola in Hilna beel and M. vittatus in Beel Kumari beel). The fecundity of mature females also increased with total body weight and ovary weight following the linear relationship (F=a+bW). Differences in values of sex-ratios with seasons for all species in this study may have resulted from different environmental factors as well as breeding seasons. The findings of this study would be useful in imposing adequate regulations for the conservation of these fascinating fishes in the fresh water bodies of Bangladesh.

Bioclimatic assessment of abiotic factors affecting relative abundance and distribution of wheat stem sawfly (Hymenoptera: Cephidae) in western Canada

AbstractWheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), indigenous to North America, quickly adapted from host native grasses to wheat crops (Triticum Linnaeus (Poaceae)) with expansion of agriculture on the Great Plains of North America. Bioclimatic simulation tools, such as Climex, predict the potential geographic distribution and establishment of insects in ecosystems, based on climate. The ecoclimatic index, a measure of ecological suitability, integrates potential population growth with stresses to produce estimates of relative abundance. This simulation software was used to develop a bioclimate model for C. cinctus in western Canada. Results fostered a better understanding of how C. cinctus responded to selected climate variables. Two general circulation models were then applied to assess the response of C. cinctus populations to future climate. Relative to current climate, predicted changes in C. cinctus distribution and relative abundance were greatest for 2030, with a small further increase for 2070. Across the Prairies and Boreal Plains Ecozones, changes in ecoclimatic index were greater than in geographic distribution. Both general circulation models indicated most of this area would be categorised as very favourable. This suggests that the potential for pest populations could expand into areas that do not currently experience economic losses associated with C. cinctus.

Slow growth and delayed maturation in a Critically Endangered insular flying fox (Pteropus natalis).

Flying foxes (family Pteropodidae) have distinct life histories given their size, characterized by longevity, low reproductive output, and long gestation. However, they tend to decouple the age at which sexual maturity is reached from the age at which they reach adult dimensions. We examined growth, maturation, and reproduction in the Critically Endangered Christmas Island flying fox (Pteropus natalis) to determine the timing of sex-specific life cycle events and patterns of growth. We estimated that juvenile growth in forearm length and body mass increased at a mean rate of 0.029 ± 0.005 mm/day and 0.33 ± 0.07 g/day for both males and females alike. Using these growth rates, we determined that the birth of pups occurs between December and March, with young becoming volant between June and August. The age at maturation for P. natalis is one of the oldest among all bat species. Juvenile males began to mature 15 months after birth and reached maturity 27 months after birth. Females reached maturity 24 months after birth at a significantly smaller body mass (3.6%) and forearm length (1.4%) than males. Significant sexual dimorphism and bimaturation was observed, with juvenile males being 1.5% and adult males being 1.9% larger on average than females for skeletal dimensions only. Growth and maturation are even slower in P. natalis than in the few other Pteropus species studied to date. The slow growth and delayed maturation of P. natalis imply slower potential population growth rates, further complicating the recovery of this Critically Endangered single-island endemic.

Assessing the sensitivity of bivalve populations to global warming using an individual-based modelling approach.

Climate change exposes benthic species populations in coastal ecosystems to a combination of different stressors (e.g., warming, acidification and eutrophication), threatening the sustainability of the ecological functions they provide. Thermal stress appears to be one of the strongest drivers impacting marine ecosystems, acting across a wide range of scales, from individual metabolic performances to geographic distribution of populations. Accounting for and integrating the response of species functional traits to thermal stress is therefore a necessary step in predicting how populations will respond to the warming expected in coming decades. Here, we developed an individual-based population model using a mechanistic formulation of metabolic processes within the framework of the dynamic energy budget theory. Through a large number of simulations, we assessed the sensitivity of population growth potential to thermal stress and food conditions based on a climate projection scenario (Representative Concentration Pathway; RCP8.5: no reduction of greenhouse gas emissions). We focused on three bivalve species with contrasting thermal tolerance ranges and distinct distribution ranges along 5,000km of coastline in the NE Atlantic: the Pacific oyster (Magallana gigas), and two mussel species: Mytilus edulis and Mytilus galloprovincialis. Our results suggest substantial and contrasting changes within species depending on local temperature and food concentration. Reproductive phenology appeared to be a core process driving the responses of the populations, and these patterns were closely related to species thermal tolerances. The nonlinear relationship we found between individual life-history traits and response at the population level emphasizes the need to consider the interactions resulting from upscaling across different levels of biological organisation. These results underline the importance of a process-based understanding of benthic population response to seawater warming, which will be necessary for forward planning of resource management and strategies for conservation and adaptation to environmental changes.

Life History, Growth, and Reproductive Biology of Four Mobulid Species in the Bohol Sea, Philippines

In light of the global decline of mobulid populations and the necessity for sustainable fisheries management, baseline data for population dynamics were collected from a targeted fishery in the Bohol Sea, Philippines. This study focused on life-history parameters and reproductive cycles of four mobulid rays (Mobula thurstoni, M. japanica, M. tarapacana, and Manta birostris), and re-estimated their intrinsic population growth rates. Size and reproductive data were collected from 1,509 specimens (30% of catch) landed in two fishing seasons in 2015 and 2016. Size-at-birth was reviewed, and analysis of the embryos and follicles did not show any clear seasonality in the reproductive cycle, but supported an interbreeding interval. Females of all species matured at a larger size than males, and exhibited a larger size-at-pregnancy than -at-maturity. This delay in reproduction resulted in population growth rates lower than the actual rmax when based on size-at-pregnancy (rmat=rmax=0.016-0.055 year-1 and rpreg=0.008-0.044 year-1), and a population doubling time of 15.8-86.6 years. This study suggests that population growth rates previously reported were overestimated. In light of the Convention on International Trades of Endangered Species (CITES) and Convention on Migratory Species (CMS) assessments, while fisheries management should reflect the delayed maturation of these species and the slower population growth potential, at the current status of these population, the sustainability of any exploitation level seems unrealistic and strongly discouraged.

Population growth potential of rotifers from a high altitude eutrophic waterbody, Madín reservoir (State of Mexico, Mexico): The importance of seasonal sampling

To understand the population growth potential of different species of rotifers in nature, field collections through seasons are essential. We sampled zooplankton (and measured selected physicochemical variables) from the Madín reservoir, a high altitude eutrophic urban waterbody from Mexico, every month for a year. Qualitative analysis of zooplankton revealed 28 rotifer species and four cladoceran crustaceans plus one unidentified copepod. Cephalodella catellina (1400 ind L-1), Horaella thomassoni (550 ind L-1), Conochilus dossuarius (380 ind L-1) and Filinia longiseta (25 ind L-1) had higher peak density than other rotifers. Based on the concentrations of nitrates and phosphates, chlorophyll a levels or different diversity indices (e.g., Carlson, Shannon-Wiener, Pantle and Buck, Ejsmont-Karabin’s TSIRot), the waterbody is eutrophic to hypertrophic, depending on the season. In this waterbody we observed high densities of Aphanothece sp. which is a toxic picocyanobacterium. During the blooms of Aphanothece, we also recorded higher densities of H. thomassoni and C. catellina. Based on the gut contents we found that both these rotifer species feed on Aphanothece in this waterbody. This study thus suggests the potential growth of Horaella, Cephalodella, Conochilus and Filinia in this eutrophic reservoir containing blooms of Aphanothece.

Matrix Models of Hierarchical Demography: Linking Group- and Population-Level Dynamics in Cooperative Breeders

For highly social species, population dynamics depend on hierarchical demography that links local processes, group dynamics, and population growth. Here, we describe a stage-structured matrix model of hierarchical demography, which provides a framework for understanding social influences on population change. Our approach accounts for dispersal and affords insight into population dynamics at multiple scales. The method has close parallels to integral projection models but focuses on a discrete characteristic (group size). Using detailed long-term records for meerkats (Suricata suricatta), we apply our model to explore patterns of local density dependence and implications of group size for group and population growth. Taking into account dispersers, the model predicts a per capita growth rate for social groups that declines with group size. It predicts that larger social groups should produce a greater number of new breeding groups; thus, dominant breeding females (responsible for most reproduction) are likely to be more productive in larger groups. Considering the potential for future population growth, larger groups have the highest reproductive value, but per capita reproductive value is maximized for individuals in smaller groups. Across a plausible range of dispersal conditions, meerkats' long-run population growth rate is maximized when individuals form groups of intermediate size.

A Population Model Exploring Factors Influencing Black Oystercatcher(Haematopus bachmani)Population Dynamics

Count data suggest that Black Oystercatcher (Haematopus bachmani) has locally variable but globally stable populations. A simple, stage-based matrix population model for Black Oystercatcher was built and Monte Carlo simulations of the model were conducted using vital rates from peer-reviewed and gray literature. Simulations yielded a distribution of potential population growth rates that extended from 0.87 to 1.14 and was centered at 1.00, supporting the hypothesis of a globally stable Black Oystercatcher population. Sensitivity and elasticity analyses of the population model showed that potential population growth is particularly sensitive to changes in hatching success (i.e., proportion of eggs hatched), fledging success (i.e., proportion of chicks fledged), and breeding adult annual survival. These rates could be possible targets for population management should it become necessary given future changes in sea temperature, sea level, and coastal development. Pair productivity, which integrates hatching and fledging success, is suggested as a simple and valuable metric for monitoring population growth potential of Black Oystercatcher.

Emergency Department Visits and Ambient Temperature: Evaluating the Connection and Projecting Future Outcomes.

The U.S. Global Climate Change Research Program has identified climate change as a growing public health threat. We investigated the potential effects of changes in ambient daily maximum temperature on hyperthermia and cardiovascular emergency department (ED) visits using records for patients age 64 and younger from a private insurance database for the May–September period for 2005–2012. We found a strong positive relationship between daily maximum temperatures and ED visits for hyperthermia but not for cardiovascular conditions. Using the fitted relationship from 136 metropolitan areas, we calculated the number and rate of hyperthermia ED visits for climates representative of year 1995 (baseline period), as well as years 2050 and 2090 (future periods), for two climate change scenarios based on outcomes from five global climate models. Without considering potential adaptation or population growth and movement, we calculate that climate change alone will result in an additional 21,000–28,000 hyperthermia ED visits for May to September, with associated treatment costs between $6 million and $52 million (2015 U.S. dollars) by 2050; this increases to approximately 28,000–65,000 additional hyperthermia ED visits with treatment costs between $9 million and $118 million (2015 U.S. dollars) by 2090. The range in projected additional hyperthermia visits reflects the difference between alternative climate scenarios, and the additional range in valuation reflects different assumptions about per‐case valuation.

Prediction of ecological effects of potential population and impervious surface increases using a remote sensing based ecological index (RSEI)

The ecological impact of urban development and population increase is an area of increasing relevance as human modification of the landscape continues unabated. The prediction of this impact will help inform urban planning and decision making around population growth, impervious surface (IS) increase and associated ecological effects. The Xiong’an New Area is a state-level new area to be established in North China. The population growth goal for the area is going to reach 2.5 million and the area is planned to expand to 2000 km2. The potential population growth and area expansion will result in a massive increase in IS area and thus may impact the regional ecological quality. A clear understanding of the impact would help to minimize the influence of the new area’s development on regional ecological quality. Therefore, this study investigated current land cover types and ecological status in the Xiong’an New Area using feature inversion techniques and the improved remote sensing-based ecological index (RSEI). Statistical models were developed to predict ecological effects responding to the forthcoming population and associated IS increase in the new area. This was achieved by relating population growth to IS area increase and exploring the relationships between IS area and RSEI. The results show that the area’s land surface has not been intensively developed and the current ecological status is good. The RSEI-based prediction shows that IS area has a noteworthy effect on regional ecological conditions. The variation of IS proportions in the new area can result in a significant shift of RSEI. A balance amount of total IS area in the 2000 km2 new area is 433 km2. Exceeding/reducing the amount would result in a decline/rise of the area’s ecological quality. Introducing a quantity of IS area-related population density (IPD) reveals that the area’s ecological quality is actually related to IPD rather than to traditional population density when the total area and future population of the new area are given. Therefore, the forthcoming regional master planning for the new area should include specific efforts to control IS area increase.

High pregnancy rates in humpback whales (Megaptera novaeangliae) around the Western Antarctic Peninsula, evidence of a rapidly growing population.

Antarctic humpback whales are recovering from near extirpation from commercial whaling. To understand the dynamics of this recovery and establish a baseline to monitor impacts of a rapidly changing environment, we investigated sex ratios and pregnancy rates of females within the Western Antarctic Peninsula (WAP) feeding population. DNA profiling of 577 tissue samples (2010–2016) identified 239 males and 268 females. Blubber progesterone levels indicated 63.5% of the females biopsied were pregnant. This proportion varied significantly across years, from 36% in 2010 to 86% in 2014. A comparison of samples collected in summer versus fall showed significant increases in the proportion of females present (50% to 59%) and pregnant (59% to 72%), consistent with demographic variation in migratory timing. We also found evidence of annual reproduction among females; 54.5% of females accompanied by a calf were pregnant. These high pregnancy rates are consistent with a population recovering from past exploitation, but appear inconsistent with recent estimates of WAP humpback population growth. Thus, our results will help to better understand population growth potential and set a current baseline from which to determine the impact of climate change and variability on fecundity and reproductive rates.

Predicting effect of forthcoming population growth–induced impervious surface increase on regional thermal environment: Xiong'an New Area, North China

The Xiong'an New Area is a state-level new area to be established in the Baoding area of Hebei province, North China. The planning population growth goal for the area is going to reach 2.5 million and the area is planned to expand to 2000 km2. The potential population growth and area expansion will result in massive increase in impervious surface (IS) dominated built land and thus may impact the area's thermal environment. Therefore, based on current land cover types and thermal environment status in the area, this study developed a statistical model to predict thermal effects responding to the forthcoming population and associated IS increase in the new area using remote sensing technology. This was achieved by relating population growth to IS area increase, exploring the relationships among population, land cover, and land surface temperature (LST), and developing a metric for estimating a balance amount of total IS area to be expanded. The prediction shows that IS has a noteworthy effect on regional thermal environment. The variation in the proportions of the IS in the new area can result in a significant shift of LST. A balance amount of total IS area in the 2000 km2 new area is 433 km2. Exceeding/reducing the amount would result in a rise/decline of the area's LST. Introducing a quantity of IS area-related population density (IPD) reveals that the area's LST is closely related to IPD when the total area and future population of the new area are given.

Mesopelagic fish assemblages across oceanic fronts: A comparison of three frontal systems in the southern California Current Ecosystem

With strong horizontal gradients in physical properties, oceanic frontal regions can lead to disproportionately high biological productivity. We examined cross-frontal changes in mesopelagic fish assemblages at three separate frontal systems in the southern California Current Ecosystem (CCE) as part of the CCE Long Term Ecological Research program: the A-Front sampled in October 2008, the C-Front in June/July 2011, and the E-Front in July/August 2012. We analyzed the differential effects of front-associated regions on density and species composition of adult migratory and non-migratory fishes and larvae, and the larval to adult ratio (as a possible index of a population growth potential) for migratory and non-migratory species. The fronts did not have a strong effect on densities of any subset of the mesopelagic fish assemblage. The species composition of the vertical migratory fishes (and their larvae) was typically altered across fronts, with different assemblages present on either side of each front. The migratory assemblages at the fronts themselves were indistinguishable from those at the more productive side of the frontal system. In contrast, the assemblage composition of the non-migratory fishes was indistinguishable between regions across all three of the fronts. The differences between the Northern and Southern assemblages at the A-Front were primarily based on biogeographic provinces, while the assemblages at the E-Front were largely distinguishable by their oceanic or coastal-upwelling zone associations. These results generally confirm those of previous studies on frontal systems in the California Current Ecosystem and elsewhere. The ratio of larvae to adults, a potential index of population growth potential, was altered across two of the fronts for migratory species, elevated on the colder side of the A-Front and the warmer side of the E-Front. This finding suggests that fronts may be regions of enhanced reproduction. The larvae to adult ratio was indistinguishable for non-migratory species at all three frontal systems. The non-migratory component of the community was little influenced by the presence of a front, apparently because the regions of strongest horizontal spatial gradients were too shallow to be experienced directly. We speculate that there was no change in larval community composition and population growth index at the most dynamic frontal system (C-Front) compared to the other fronts surveyed because the frontal feature was short-lived relative to the time scale for population growth of the fish. However, the difference in results of the C-Front may also be due to a change in methodology used in this study. If mesoscale features such as fronts increase in frequency off the California coast in the future as predicted, they have the potential to alter population growth potential and restructure mesopelagic fish assemblages, which are dominated by migratory species.

Biology of Maconellicoccus hirsutus (Hemiptera: Pseudococcidae) on Hibiscus rosa-sinensis

Maconellicoccus hirsutus Green, 1908 (Hemiptera: Pseudococcidae) is an introduced pest that threatens fruit and ornamental plant production in Brazil. Reported in Brazil for the first time in 2010, in the state of Roraima, M. hirsutus, has spread rapidly to other regions of the country. The objective of this study was to investigate the biology of M. hirsutus on Hibiscus rosa-sinensis L. (Malvaceae) leaves in laboratory conditions with climatic parameters similar to those of the Brazilian North and Northeast (27 ± 1 °C, 60 ± 10% relative humidity and 12 hours light and 12 hours dark). Eighty M. hirsutus nymphs were individualized on rooted H. rosa-sinensis leaves and their survival, mortality, sex ratio, and egg numbers per female emerged were recorded. Maconellicoccus hirsutus can have up to nine generations per year, taking 6.5 days to double its population size. The female numbers of this pest are about three times higher than those for its male counterparts, with 98 eggs per female and 97% viability. The survival curve of the species is type I, that is, mortality rates are higher in adulthood. Maconellicoccus hirsutus, especially, a pest of fruit trees and ornamental plants, presents great potential for population growth in Brazilian tropical conditions.

Role of population genetics in guiding ecological responses to climate.

Population responses to climate were assessed using 3-7years height growth data gathered for 266 populations growing in 12 common gardens established in the 1980s as part of five disparate studies of Pinus contorta var. latifolia. Responses are interpreted according to three concepts: the ecological optimum, the climate where a population is competitively exclusive and in which, therefore, it occurs naturally; the physiological optimum, the climate where a population grows best but is most often competitively excluded; and growth potential, the innate capacity for growth at the physiological optimum. Statistical analyses identified winter cold, measured by the square root of negative degree-days calculated from the daily minimum temperature (MINDD01/2 ), as the climatic effect most closely related to population growth potential; the colder the winter inhabited by a population, the lower its growth potential, a relationship presumably molded by natural selection. By splitting the data into groups based on population MINDD01/2 and using a function suited to skewed normal distributions, regressions were developed for predicting growth from the distance in climate space (MINDD01/2 ) populations had been transferred from their native location to a planting site. The regressions were skewed, showing that the ecological optimum of most populations is colder than the physiological optimum and that the discrepancy between the two increases as the ecological optimum becomes colder. Response to climate change is dependent on innate growth potential and the discrepancy between the two optima and, therefore, is population-specific, developing out of genotype-environment interactions. Response to warming in the short-term can be either positive or negative, but long term responses will be negative for all populations, with the timing of the demise dependent on the amount of skew. The results pertain to physiological modeling, species distribution models, and climate-change adaptation strategies.

Comparative development and reproduction ofPlanococcus ficusandPlanococcus citri(Hemiptera:Pseudococcidae) on grapevine under field conditions

AbstractMealybugs are major pests in grape‐growing areas worldwide, causing direct and indirect crop damage. The vine mealybugPlanococcus ficus(Signoret) is a key pest in most of grape‐producing countries, whereas the citrus mealybugPlanococcus citri(Risso) is reported as being destructive inBrazilian andSpanish vineyards.We examined the adaptation of the citrus mealybug to grapevine by investigating its development, reproduction and life‐history parameters underMediterranean field conditions in comparison with those ofP. ficus.Both mealybug species developed and reproduced successfully on grapevine. However,P. ficusshowed a shorter development time, larger female body size, and higher fecundity, fertility and survival thanP. citri.The life‐history parameters further highlighted the different growth potential of vine and citrus mealybug populations becauseP. ficusexhibited a net reproductive rate and an intrinsic rate of increase two‐ to four‐fold higher than that ofP. citri. Furthermore, the vine mealybug population doubled its number in approximately half time with respect to the citrus mealybug.Overall, the results of the present study show a better development and reproductive performance and a higher population growth potential ofP. ficuscompared withP. citri, indicating a higher capacity of the vine mealybug to develop on grapevine inMediterranean vineyards.

Quantifying the demographic cost of human-related mortality to a raptor population.

Raptors are exposed to a wide variety of human-related mortality agents, and yet population-level effects are rarely quantified. Doing so requires modeling vital rates in the context of species life-history, behavior, and population dynamics theory. In this paper, we explore the details of such an analysis by focusing on the demography of a resident, tree-nesting population of golden eagles (Aquila chrysaetos) in the vicinity of an extensive (142 km2) windfarm in California. During 1994–2000, we tracked the fates of >250 radio-marked individuals of four life-stages and conducted five annual surveys of territory occupancy and reproduction. Collisions with wind turbines accounted for 41% of 88 uncensored fatalities, most of which were subadults and nonbreeding adults (floaters). A consistent overall male preponderance in the population meant that females were the limiting sex in this territorial, monogamous species. Estimates of potential population growth rate and associated variance indicated a stable breeding population, but one for which any further decrease in vital rates would require immigrant floaters to fill territory vacancies. Occupancy surveys 5 and 13 years later (2005 and 2013) showed that the nesting population remained intact, and no upward trend was apparent in the proportion of subadult eagles as pair members, a condition that would have suggested a deficit of adult replacements. However, the number of golden eagle pairs required to support windfarm mortality was large. We estimated that the entire annual reproductive output of 216–255 breeding pairs would have been necessary to support published estimates of 55–65 turbine blade-strike fatalities per year. Although the vital rates forming the basis for these calculations may have changed since the data were collected, our approach should be useful for gaining a clearer understanding of how anthropogenic mortality affects the health of raptor populations, particularly those species with delayed maturity and naturally low reproductive rates.

Population growth potential of Epilachna vigintioctopunctata (F.) (Coleoptera: Coccinellidae) on some solanaceous medicinal plants

ABSTRACTThe spotted ladybird beetle, Epilachna vigintioctopunctata (F.) (Coleoptera: Coccinellidae), is an important pest of solanaceous medicinal plants in India. In this study, we investigated population growth potential of E. vigintioctopunctata in the laboratory at 28 ± 1°C with 80% ± 5% RH and 14:10 L:D photoperiod on seven solanaceous medicinal plants, viz. Solanum nigrum (L.), Datura metel (L.), Datura alba (L.), Solanum surattense Burm. (F.), Withania somnifera (L.) Dunal (wild) and cultivars of W. somnifera, viz. “JA 20” and “JA 134”. The lowest rate of population growth occurred on D. metel, where immature development time, immature survival and pre oviposition period were highest, and fecundity was lowest (183.96 eggs per female). The highest growth rate occurred on S. surrattense and fecundity was also highest (637.08). The lowest net reproductive rate (Ro) (56.60) and the intrinsic rate of population increase (rm) (0.07) were obtained on D. metel and were highest on S. surattense (305.90 and 0.14 respectively). The mean generation time (T) was shortest on S. surattense (40.95 days). Using these measures, it is recognized that E. vigintioctopunctata performance was best on S. surattense and worst on D. metel. The findings of this study will contribute to the development of effective integrated pest management strategies for E. vigintioctopunctata on cultivated W. somnifera.