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Successful anti-poaching policies and effective conservation of Asian elephants Elephas maximus require input and support from all stakeholders, including the public. But although Myanmar has one of the largest remaining populations of wild Asian elephants, there has been little research on public attitudes there towards elephants and poaching. We developed a questionnaire to assess attitudes of people in rural and urban areas towards elephants and conservation, and their perceptions of and experience with elephant poaching. We conducted 178 interviews across two regions in Myanmar. Although both rural and urban participants supported elephant conservation, people from urban areas expressed more favourable attitudes towards elephants than their rural counterparts. Similarly, conservation priorities differed between rural and urban communities, with rural communities less likely to believe that peaceful human–elephant coexistence was possible and preferring conservation initiatives that prioritize human activities over elephant conservation. Both groups were familiar with elephant poaching in Myanmar, but rural communities appeared to be better informed regarding the challenges faced by conservation agencies, and were more negatively affected by poaching. Our findings highlight potential areas for intervention by government and conservation agencies to reduce criminal activity and to protect both Myanmar's citizens and its elephants.

Despite containing the largest extent of unfragmented landscape in the Asian elephant (Elephas maximus) range, Myanmar has high levels of human–elephant conflict. The Bago Yoma mountain region of central Myanmar has previously been identified as an elephant conflict hotspot, characterized by high levels of crop-raiding and illegal killing of elephants for the ivory and skin trades. We used non-invasive fecal sampling to evaluate the population structure and demography of wild and captive elephants in the Bago Yoma using microsatellite loci and mitochondrial DNA in combination with crop-raiding status, age, and sex. We were able to collect 252 samples from wild elephants –119 directly following conflict events– and 25 from captive elephants from which we identified 127 unique wild and 21 captive individuals. The population was biased toward subadults, which could be an important contributor to the high rates of conflict, as these individuals may lack the experience to avoid dangerous behaviors. Conflict elephants were primarily male, although both sexes and all ages engaged in crop-raiding, including females with juveniles. We found that elephants that commit solo raids were all male, while larger raiding parties often included both related and unrelated individuals of both sexes. Repeat offenders were common. These wild elephants contained high levels of genetic diversity, differentiated from local captive populations, and valuable for the species’ conservation. Overall, the elephants of Bago Yoma, Myanmar have been heavily affected by conflict, and managers could utilize the knowledge presented to aid in the preservation of this population.

Human-wildlife conflict has direct and indirect consequences for human communities. Understanding how both types of conflict affect communities is crucial to developing comprehensive and sustainable mitigation strategies. We conducted an interview survey of 381 participants in two rural areas in Myanmar where communities were exposed to human-elephant conflict (HEC). In addition to documenting and quantifying the types of direct and indirect impacts experienced by participants, we evaluated how HEC influences people’s attitudes towards elephant conservation. We found that 99% of participants suffered from some type of indirect impact from HEC, including fear for personal and family safety from elephants and fear that elephants will destroy their home. Despite experiencing moderate levels of indirect impacts from HEC at the community level, participants expressed attitudes consistent with supporting future elephant conservation programs.

Protected areas provide some of the last refuges for Asian elephants in the wild. Managing these areas for elephants will be critical for elephant conservation. Scientists know little about elephant habitat use in Asia and how invasive species or livestock grazing influence habitat use. We studied these issues in two protected areas in Sri Lanka, Udawalawe National Park and Hurulu Eco-Park. These areas contain some of Sri Lanka's largest remaining grasslands. These grasslands are threatened by the invasive and toxic shrub, Lantana camara, and are used for illegal livestock grazing. To measure habitat use by elephants and livestock, we conducted dung surveys along over 50 km of transects stratified across grassland, scrub, and forest. We surveyed 159 vegetation plots along these transects to assess plant composition, and mapped habitat types based on satellite images. We used mixed-effect models to determine the relative importance of habitats, livestock presence, and plant associations for elephant use. Elephant presence was greatest in scrub and grassland habitats, positively associated with both livestock presence and short graminoids, and unaffected by L. camara, which was widespread but at low densities. Given the importance of these areas to elephants, we recommend a precautionary management approach that focuses on curbing both illegal grazing and the spread of L. camara.

Over the next century, temperatures are expected to rise by 1-4°C in the Greater Yellowstone Region. This will force alpine species such as the American pika (Ochotona princeps) to compensate, shift in distribution, or disappear. If pika are limited by temperatures, they may disappear from warmer, lower elevation southwest-facing sites and find refuge in cooler, higher elevation northeast-facing sites. However, populations have been found across a range of elevations, suggesting they are instead limited by food or a need for large talus slopes. We explored these possibilities in the Beartooth Mountains, near Yellowstone, by surveying 31 pika populations and asking whether pika density varied with elevation, food availability, or aspect, all related to temperatures, or with talus area, which is not. Pika density was estimated by latrine density, which ranged from 14.6 to 167.4 per ha and declined slightly with elevation but was unrelated to vegetation. From a preliminary analysis of 61 sites, we estimated an occupancy probability of 0.89, with occupancy most strongly related to talus area. We will test and refine these results by predicting the locations of additional colonies, and by incorporating microclimate data into an ecophysiological model of temperature dependence in pika, with the long-term goal of predicting the fate of pika under a warming climate. Featured photo by Diana R on Unsplash. https://unsplash.com/photos/g6CD00mDN5A

The Double-crested Cormorant (Phalacrocorax auritus) is culled in many states because of the real and presumed damages it inflicts on farmed and recreational fisheries and other ecosystem services. Resident cormorant colonies breeding in the southeastern United States are protected in some areas, so it is important to distinguish these from co-occurring but unprotected migratory cormorants. Migratory P. auritus are likely to contain helminthic parasite communities that differ from those of non-migratory, resident birds, because they will encounter a wider variety of habitats and intermediate host communities during migrations. Here, we document five distinct assemblages of helminth parasites collected from 218 P. auritus culled from 11 sites in Alabama, Minnesota, Mississippi, and Vermont. The assemblages of P. auritus parasites are distinct among many sampling locations and can be used to correctly predict where a host cormorant has been feeding. We provide evidence for mixing of cormorants at a regional scale using discriminant analysis, which suggests there is a single population of migratory cormorants. Furthermore, our models strongly differentiate between migratory and resident P. auritus in the southeastern United States. In conjunction with species-by species latitudinal and longitudinal trends, our models could serve as effective tools for managers interested in both the population control of migratory cormorants and the conservation of non-migratory, resident birds. Finally, parasite counts per host are notoriously variable with many zeros and a few large numbers, leading many researchers to use simple prevalence in their analyses. We show that an intermediate level of data resolution, using species occurrence ranks within individual hosts, behaves well statistically and provides the greatest discrimination among distinct host groupings.

Climate change is predicted to alter the geographic distribution of a wide variety of taxa, including butterfly species. Research has focused primarily on high latitude species in North America, with no known studies examining responses of taxa in the southeastern United States. The Diana fritillary (Speyeria diana) has experienced a recent range retraction in that region, disappearing from lowland sites and now persisting in two phylogenetically distinct high elevation populations. These findings are consistent with the predicted effects of a warming climate on numerous taxa, including other butterfly species in North America and Europe. We used ecological niche modeling to predict future changes to the distribution of S. diana under several climate models. To evaluate how climate change might influence the geographic distribution of this butterfly, we developed ecological niche models using Maxent. We used two global circulation models, the community climate system model (CCSM) and the model for interdisciplinary research on climate (MIROC), under low and high emissions scenarios to predict the future distribution of S. diana. Models were evaluated using the receiver operating characteristics area under curve (AUC) test and the true skill statistics (TSS) (mean AUC = 0.91 &plusmn, 0.0028 SE, TSS = 0.87 &plusmn, 0.0032 SE for representative concentration pathway (RCP) = 4.5, and mean AUC = 0.87 &plusmn, 0.0031 SE, TSS = 0.84 &plusmn, 0.0032 SE for RCP = 8.5), which both indicate that the models we produced were significantly better than random (0.5). The four modeled climate scenarios resulted in an average loss of 91% of suitable habitat for S. diana by 2050. Populations in the southern Appalachian Mountains were predicted to suffer the most severe fragmentation and reduction in suitable habitat, threatening an important source of genetic diversity for the species. The geographic and genetic isolation of populations in the west suggest that those populations are equally as vulnerable to decline in the future, warranting ongoing conservation of those populations as well. Our results suggest that the Diana fritillary is under threat of decline by 2050 across its entire distribution from climate change, and is likely to be negatively affected by other human-induced factors as well.

Climate change is predicted to alter the geographic distribution of a wide variety of taxa, including butterfly species. Research has focused primarily on high latitude species in North America, with no known studies examining responses of taxa in the southeastern United States. The Diana fritillary (Speyeria diana) has experienced a recent range retraction in that region, disappearing from lowland sites and now persisting in two phylogenetically distinct high elevation populations. These findings are consistent with the predicted effects of a warming climate on numerous taxa, including other butterfly species in North America and Europe. We used ecological niche modeling to predict future changes to the distribution of S. diana under several climate models. To evaluate how climate change might influence the geographic distribution of this butterfly, we developed ecological niche models using Maxent. We used two global circulation models, the community climate system model (CCSM) and the model for interdisciplinary research on climate (MIROC), under low and high emissions scenarios to predict the future distribution of S. diana. Models were evaluated using the receiver operating characteristics area under curve (AUC) test and the true skill statistics (TSS) (mean AUC = 0.91 ± 0.0028 SE, TSS = 0.87 ± 0.0032 SE for representative concentration pathway (RCP) = 4.5; and mean AUC = 0.87 ± 0.0031 SE, TSS = 0.84 ± 0.0032 SE for RCP = 8.5), which both indicate that the models we produced were significantly better than random (0.5). The four modeled climate scenarios resulted in an average loss of 91% of suitable habitat for S. diana by 2050. Populations in the southern Appalachian Mountains were predicted to suffer the most severe fragmentation and reduction in suitable habitat, threatening an important source of genetic diversity for the species. The geographic and genetic isolation of populations in the west suggest that those populations are equally as vulnerable to decline in the future, warranting ongoing conservation of those populations as well. Our results suggest that the Diana fritillary is under threat of decline by 2050 across its entire distribution from climate change, and is likely to be negatively affected by other human-induced factors as well.

In the southern Bago Yoma mountain range in Myanmar, Asian elephants are being killed at a disturbing rate. This emerging crisis was identified initially through a telemetry study when 7 of 19 of collared elephants were poached within a year of being fitted with a satellite-GPS collar. Subsequent follow up of ground teams confirmed the human caused death or disappearance of at least 19 elephants, including the seven collared individuals, within a 35 km2 area in less than two years. The carcasses of 40 additional elephants were found in areas located across south-central Myanmar once systematic surveys began by our team and collaborators. In addition to the extreme rate of loss, this study documents the targeting of elephants for their skin instead of the more common ivory, an increasing trend in Myanmar. Intensive research programs focused on other conservation problems identified this issue and are now encouraging local authorities to prioritize anti-poaching efforts and improve conservation policies within the country. Myanmar represents one of the last remaining countries in Asia with substantial wildlands suitable for elephants. Increasing rates of human-elephant conflict and poaching events in this country pose a dire threat to the global population.

The Diana fritillary, Speyeria diana (Cramer 1777) (Lepidoptera: Nymphalidae), is a North American endemic butterfly that disappeared from low elevation sites throughout its range in the twentieth century. It now persists in two geographically isolated mountainous regions, with an 800 km disjunction. Using mitochondrial cytochrome oxidase II DNA sequences from museum and field-sampled specimens, we found greater mtDNA diversity and more widespread differentiation among eastern populations than western ones. In addition, using coalescent-based population divergence models we dated the earliest splitting of eastern and western populations at least 20,000 years ago, during the Last Glacial Maximum. Therefore, the recent range collapse across the center of the historical species distribution may have exacerbated an ancient genetic differentiation between eastern and western populations. Finally, the loss of lowland haplotypes and the relatively large variation among local populations suggests that dispersal is low and lowland populations did not move to higher elevations, perhaps in response to climate change but, rather, appear to have vanished. Our results highlight the value of incorporating genetic data from preserved specimens when investigating the phylogeographic history and conservation status of a threatened species.

Global warming can affect the distributions, phenology and, ultimately, conservation status of species worldwide, but most published studies on its biological effects have focused on higher latitude species. We extended this work to the Diana fritillary, a butterfly which once ranged throughout the Southeastern United States but now is severely restricted in range. We searched for all scientific records of this species, from publications, catalogued and uncatalogued specimens in public and private collections in the United States and Europe, online databases, contemporary field surveys by scientists and amateurs, and our own field surveys. We analysed these records for shifts in latitude, longitude, elevation and phenology. We found that the Diana fritillary has disappeared entirely from the Atlantic coastal plain, where it was first described, and from interior lowland sites. It now persists in two disjunct parts of its former range, the Southern Appalachian Mountains and the Interior Highlands of Oklahoma and Arkansas, and is shifting to higher elevations at about 18 m per decade. In addition, females are being collected 4.3 days earlier per decade though males, which emerge first, have not shifted their phenology. All these patterns are weakly dependent on latitude. These shifts in distribution and phenology are consistent with the predicted effects of global warming, but we review other large scale changes to the region which also might contribute singly or jointly to these patterns. We also comment on the implications for the conservation of this species.

Myanmar is an ideal location for Asian elephant ( Elephas maximus L.) conservation because it still contains large expanses of elephant habitat. However, increasing human–elephant conflict (HEC) threatens to derail ongoing elephant conservation programs. We conducted 303 interviews in rural communities living near elephants to help inform long-term management strategies to conserve this endangered species. We sought to understand the main challenges that people in these communities face in improving their quality of life, as well as the types and levels of HEC they experience and their attitudes toward elephant conservation. Poverty, not conflict with elephants, was the greatest obstacle reported by our participants. However, HEC was deemed a moderate to major problem, with 38% of farmers indicating they lost half or more of their crops to elephants the previous year. Our results showed that communities living in proximity to and often harmed by elephants were nevertheless supportive of elephant conservation and willing to contribute to conservation efforts. This result offers hope in the quest to maintain elephant populations in Myanmar. We conclude that conservation policies that also address societal challenges such as poverty may be more effective in protecting elephants than policies that address HEC alone.

The role of inbreeding depression in the extinction of wild populations is controversial, largely because there are no quantitative estimates of its impact using realistic levels of inbreeding depression. To address this deficiency, this study (1) provides a comprehensive estimate of the impact of inbreeding depression on wild, mammalian and avian species via a meta-analysis, and (2) determines the impact of this level of inbreeding depression on extinction risk over a broad taxonomic range via stochastic computer projections with and without inbreeding depression for populations with carrying capacities of 100, 500 and 2000 individuals. An average overall effect of 12 diploid lethal equivalents was found across the life-history of the species in the meta-analysis. In the stochastic computer projections, 12 diploid lethal equivalents of inbreeding depression (with purging) decreased median times to extinction by an average of 37%. These decreases were significant and of very similar magnitude, regardless of the carrying capacity modelled. Disregarding the influence of inbreeding depression on extinction risk will lead to serious overestimates of the survival prospects of threatened mammalian and avian taxa. Further, inappropriate recovery plans may be instituted if the causes of extinction risk and their relative contributions are not recognized.

All models of speciation involve some mechanism for the separation of biological populations that eventually leads to the formation of new species. In the case of aquatic species, biological evolution is often coincident with geological evolution, because populations can become geographically isolated among river systems as drainage morphologies evolve. Thus, for species that are completely restricted to aquatic habitats (e.g., Wshes), river drainages provide a powerful framework for reconstructing phylogeny and historical biogeography (Avise, 1994). The southern region of the Appalachian mountains is a model setting for investigating the historical diVerentiation of populations in aquatic environments. The region’s communities and topography are very old as they were well south of the maximum extent of Pleistocene glaciation. The result has been the persistence of biota in the region and the opportunity for diversiWcation with time. For example, the Tennessee River system, which drains the western slopes and interior of the southern Appalachians, has the highest species richness and greatest number of endemic species of Wshes in North America (Jenkins et al., 1972; Starnes and Etnier

Root-colonizing bacteria have little inherent dispersal ability. However, we have shown previously that they routinely move into plant stems, sometimes at high densities, and might therefore be acquired and transmitted by foliage-feeding insects. Here we describe laboratory and field experiments on the transmission of a genetically engineered strain of the root-colonizing bacterium Pseudomonas chlororaphis (formerly aureofaciens) by a common herbivorous insect, the red-legged grasshopper Melanoplus femurrubrum. In laboratory and field microcosms, the engineered P. chlororaphis were applied to corn seeds at planting and allowed to colonize the developing roots and to invade the aerial tissues naturally. Adult M. femurrubrum that later fed on the foliage of these plants became infested with the bacteria. The bacteria were harbored throughout the digestive tracts and elsewhere in the exposed grasshoppers and could be recovered from their frass. Grasshoppers carried the bacteria for ≥1 wk after removal from the source of inoculum and could transmit the bacteria to new plants. In the laboratory, the likelihood of transmission declined as the proportion of grasshoppers remaining infested decreased through time. Transmission was less predictable in the field. Transport by insects may make naturally occurring soil bacteria more mobile than previously thought and could make the containment of engineered strains unlikely. However, at least in this system, microbial movement through plants and insects in the field was accurately predicted by laboratory studies, which therefore remain useful in basic research in microbial ecology, and in risk assessment.

The southern corn rootworm, Diabrotica undecimpunctata subsp. howardi, a common and mobile insect pest, was shown to transmit the rhizobacte-rium Pseudomonas chlororaphis strain L11 between corn plants. Strain L11 has been genetically modified to contain the lacZY genes from Escherichia coli. It can reach high densities on roots and invade the roots and move into the foliage. D. undecimpunctata subsp. howardi became infested with L11 as larvae while feeding on roots of seed-inoculated corn and retained the bacteria through pupation, molting to the adult stage, and emergence from the soil. Bacterial densities on or in the insects increased 100-fold after they fed again as adults on L11-infested foliage. Adults retained the bacteria for at least 2 weeks after last exposure and could transmit L11 to new plants. The likelihood of transmission decreased with time since last exposure to L11, but increased with time spent on the new plants. This research demonstrates that rhizobacteria can escape the rhizosphere by moving in or onto foliage, where they can then be acquired and transmitted by insects. This transmission route may be common among naturally occurring rhizobacteria and facilitate the dispersal of both beneficial and harmful soilborne microorganisms.

Following inoculation onto seeds, the rhizobacterium Pseudomonas aureofaciens Ps3732RNL11 (L11), which contains the constituitively expressed lacZ and lacY genes from Escherichia coli, was recovered from the interior of aerial tissues of all 16 monocot and dicot plants tested, and the exterior of aerial surfaces of 15. In more detailed studies with corn, wheat, and broccoli, both Ps3732RNL11 and its nonengineered parent strain PS3732RN (RN) rapidly established large populations on all root systems and smaller densities within the aerial tissues, all of which persisted at stable levels throughout 12- to 23-day test periods. There were no differences in the behavior of L11 and RN on any of the three plant species. L11 invaded the aeriel tissues of corn in at least two distinct ways. First, it moved into the interior of leaves following inoculation of guttation drops, suggesting that the bacteria may contaminate the developing shoot prior to its emergence from the soil and then invade through natural openings. However, when this route was blocked by inoculating the roots after shoot emergence in either soil or hydroponic systems, the bacteria still invaded the aerial tissues within 24 h, suggesting direct vascular transport from the roots. Such bacterial movement is an important consideration in future field releases of both native and genetically modified rhizobacteria.Key words: rhizosphere, genetically engineered microorganism, Pseudomonas aureofaciens.

We describe a rearing protocol that allowed us to raise the threatened butterfly,Argynnis diana(Nymphalidae), while bypassing the first instar overwintering diapause. We compared the survival of offspring reared under this protocol from field-collectedA. dianafemales from North Carolina, Georgia, and Tennessee. Larvae were reared in the lab on three phylogenetically distinct species of Southern Appalachian violets (Viola sororia, V. pubescens, andV. pedata). We assessed larval survival inA. dianato the last instar, pupation, and adulthood. Males reared in captivity emerged significantly earlier than females. An ANOVA revealed no evidence of host plant preference byA. dianatoward three native violet species. We suggest that restoration ofA. dianahabitat which promotes a wide array of larval and adult host plants, is urgently needed to conserve this imperiled species into the future.

Two approximations are provided to the frequency of an autosomal allele after any number of generations of selection and, conversely, to the number of generations required for any given frequency change. These estimates are accurate over a wide range of selection coefficients and initial conditions, and have the added advantage of providing strict upper and lower bounds to the true values under quite general conditions. The approach employed here, of finding exact solutions to approximating difference equations, could easily be applied to models with migration, mutation, etc. and, indeed, to any non-linear difference equation. In such applications, it offers several advantages over traditional methods from approximation theory.

We describe a new discrete probability distribution with several useful properties for the analysis and modelling of survival processes and dispersion. First, the model can be used to describe survival processes with monotonically decreasing, constant, or increasing hazard functions, simply by tuning one parameter. Also, the model can describe counts that are overdispersed (contagious) or underdispersed, since the variance can exceed, equal, or be less than the mean. All of these properties are demonstrated both theoretically and with ecological examples, using ad-hoc parameter estimation techniques. Finally, the equations are tractable compared with, say, the negative binomial, and easily incorporated into larger models.

Many vertebrate populations exhibit large variation in natal dispersal dis- tances. Murray (1967) showed by simulation that this variation need not have a genetic basis, but could result from two factors, chance variation in proximity to suitable sites, and competition with sibs and neighbors for those sites. Waser (1985) developed an analytic model of the first of these effects, which predicts the probability that an individual will locate an available site within any given distance, under two limiting search strategies. We extend the model to consider the distances traveled by multiple dispersers from a site, under both search strategies, and show that competitive exclusion by early dispersers can further increase the variation in dispersal distances. This incorporates the effects of com- petition with siblings, but not with dispersers from other natal sites, and brings us part way toward an analytic solution to Murray's original model. In -addition, we discuss both the difficulties inherent in testing models of dispersal, and the importance of doing so for the understanding of various behavioral, population, and evolutionary processes.

"Wild populations face threats both from deterministic factors, e.g., habitat loss, overexploitation, pollution, and introduced species, and from stochastic events of a demographic, genetic, and environmental nature, including catastrophes. Inbreeding reduces reproductive fitness in naturally outbreeding species, but its role in extinctions of wild populations is controversial. To evaluate critically the role of inbreeding in extinction, we conducted realistic population viability analyses of 20 threatened species, with and without inbreeding depression, using initial population sizes of 50, 250, and 1000. Inbreeding markedly decreased median times to extinction by 28.5, 30.5, and 25% for initial populations of 50, 250, and 1000, respectively, and the impacts were similar across major taxa. The major variable explaining differences among species was initial population growth rate, whereas the impact of inbreeding was least in species with negative growth rates. These results demonstrate that the prospects for survival of threatened species will usually be seriously overestimated if genetic factors are disregarded, and that inappropriate recovery plans may be instituted if inbreeding depression is ignored."

Size ratios are convenient indexes of the morphological differences between species. They have been variously used to predict multidimensional niche separation, explain coexistence, and even indicate "missing species," depending on whether they are small, moderate, or large. From a statistical viewpoint, ratios of ranked species' sizes are ratios of successive order statistics, which are largely independent of the underlying size distribution. We derive probability density functions for these ratios, assuming that species' sizes are independently drawn from uniform or unimodal distributions. In the absence of frequent character displacement, distributions of ratios should be negative exponential in form, with average values decreasing with increasing guild size. These predictions, which differ from those under a purely competitive model, are tested with several large data sets. In contrast, the statistical analysis of ratios in small data sets, such as individual guilds, depends on arbitrary assumptions a...

In most population models, the per-capita growth rate is assumed to decline monotonically with density. Here, I consider a model of one or more species in which the per-capita growth rate increases with population size at low densities. These populations will interact as intra- and interspecific mutualists if natural enemies can stabilize them at low levels. This idea is tested with examples of phytophagous insects that have humped per-capita growth curves because of plant physiological responses to herbivory. As predicted, these insects exploit this effect with a wide array of subsocial behaviors, parthenogenesis, and even the evolution toward gregarious, sessile living. This model differs from others in the literature in two ways: the mutualism only occurs at low densities and therefore requires the action of natural enemies; and the benefit may be conferred to individuals of the same as well as of other species.

An early motivation for this study was the problem of relocation of scarce or endangered species of animals for breeding and/or reintroduction to establish new populations in the wild. In this paper, we introduce single and multiple objective optimization models which are designed to comprehend a wide variety of objectives which are of interest to conservation and wildlife managers. We present the models in a general way and point out special features relative to ecology as they arise. Thus, the models may be used for relocation decisions analysis in diverse fields, not only in conservation and ecology. After presentation of the models in such a general way, we reformulate the models to make use of the special structure present. Such reformulation reduces the number of decision variables and constraints and, in general, makes solutions easy to obtain. By easy to obtain, we mean that tools from linear and mixed-integer programming together with elementary sorting procedures provide the basis for solving the models. In order to illustrate the capabilities of the models and solution techniques developed, we present the results of their application to the real-life relocation problem arising while analyzing restoration of the globally endangered Przewalski's horse population.

A formula is developed which allows sweep net data to be reported as the number of insects caught per unit volume of vegetation sampled. Presenting results in these absolute units will facilitate comparisons with other sampling methods and with other sweep net data when parameters of the sweeps employed differ.

Oxidized kaurene derivatives were isolated from the leaves of Solidago missouriensis and S. rigida and identified as kauran-16β-ol, kaur-16-en-19-oic acid and 7β-hydroxykaur-16-en-19-oic acid. The structure of the latter compound was determined by X-ray crystallographic analysis of its methyl ester.

We measured variation in gender among individuals within populations of ragweed (Ambrosia artemisiifolia) in an abandoned old-field and in the greenhouse. There was great variability in sex expression, from all-female to approximately 78% male. Plants differed significantly in gender in different locations within the field. Plants in an area abandoned from agriculture one year previously were more male than plants in a nearby area abandoned four years previously. In the greenhouse, soil moisture treatments and levels of attack by spittlebugs (Philaenus spumarius) did not affect gender. Height was positively correlated with relative maleness in both populations. Plants with greater shoot weight were relatively more male in the greenhouse, but not in the field. The gender variation we observed either has a genetic basis or is controlled by environmental variables other than those we investigated.

The goldenrod leaf beetle, Trirhabda canadensis, is known to respond to odors of host and non-host species in the laboratory. Here we report movements of T. canadensis in the field in response to volatile odors from monocultures and polycultures of host plants. Overall, beetles preferentially colonized plots with a higher density of host plants and lower diversity of allelochemicals, but under some wind conditions there were marked exceptions. At high windspeeds, they colonized whichever plot(s) was upwind. At low windspeeds, beetles colonized preferred plots even when they were not upwind. The data suggest that odor dispersion varies in a complex way with windspeed: at low windspeeds beetles received information from a wide are of vegetation and made choices while at high windspeeds information was available only from upwind plot(s).

Two large orders of insects—the Hemiptera and Homoptera—possess mouthparts that are highly modified for piercing tissues and extracting their fluid contents. Food sought by hemipterans may be the blood of vertebrates [e.g., Cimicidae (bed bugs)], the hemolymph of other invertebrates [e.g., Reduviidae (ambush bugs) and Gerridae (water striders)] or the cytoplasm and sap of plants [many Miridae (plant bugs) and Pentatomidae (stink bugs) (76)]. The Homoptera are strictly plant feeders (23), the only exceptions being several species of aphids with predatory early instars (2).

SUMMARY (1) Insect populations frequently suffer some density dependent effect in addition to mortality from insect parasitoids. This paper follows Wang & Gutierrez (1981) in examining the question: 'Does the ordering of density dependence and parasitism in the host life cycle have a significant effect on the dynamics of the interaction?' (2) The properties of three models in which density dependence either acts before or after parasitism are displayed in terms of the hosts' rate of increase and the extent to which parasitism depresses the host equilibrium below its carrying capacity. (3) From this analysis, we conclude that the sequence of these events in the host life cycle can indeed have a marked affect on the population dynamics. In particular, the model with parasitism acting before density dependence stands apart in permitting a stable host-parasitoid interaction with the host population above its parasite-free carrying capacity. (4) These conclusions have implications for the use of parasitoids as biological control agents.