Effects of management regimes and extreme climatic events on plant population viability in Eryngium alpinum

Extreme climatic events like the 2003 summer heatwave and inappropriate land management can threaten the existence of rare plants. We studied the response of Eryngium alpinum, a vulnerable species, to this extreme climatic event and different agricultural practices. A demographic study was conducted in seven field sites between 2001 and 2010. Stage-specific vital rates were used to parameterize matrix population models and perform stochastic projections to calculate population growth rates and estimate extinction probabilities. Among management regimes, spring grazing and land abandonment decreased vital rates and population growth, while autumn grazing and late mowing had positive effects on population viability. The 2003 heatwave reduced fecundity rates and survival rates. Only spring grazed sites presented considerable extinction risk. Stochastic projections showed that an increased frequency of 2003-like events may exacerbate extinction risk, but extinction probability depends mainly on land management regimes. To better conserve E. alpinum populations, we recommend conversion of presently spring grazed and abandoned sites to late mowing or autumn grazing.     

Savanna herbivore dynamics in a livestock-dominated landscape: I. Dependence on land use, rainfall, density, and time

Ecosystem processes in African savannas can be better conserved if management is based on a mechanistic understanding of wildlife dynamics in livestock-dominated landscapes. For Laikipia District, a non-protected savanna region in northern Kenya, we used spatially explicit estimates of density to characterize factors influencing the dynamics of large herbivores on three land-use types: commercial ranches that favor wildlife, communal ‘group ranches’ practicing pastoralism, and the remainder (‘transitional’ properties). For 21-year time series of nine wild and two domestic species, linear model selection was used to ascribe between 45% (Grant’s gazelle) and 95% (plains zebra) of observed variation in biomass density to land use, rainfall-dependence, density-dependence, and trends over time.Strongly opposing patterns of variation across the landscape in wildlife and livestock densities affirmed the primacy of land use among factors influencing wildlife abundance in non-protected areas. Rainfall limited densities of only the dominant grazing species throughout the monitoring period (plains zebra and cattle), and of most other species while their densities were high. Regulating effects of density were detected only for the dominant wild grazing and browsing species (zebra and giraffe). All but two wild species (zebra and Grant’s gazelle) declined on at least one land-use type, for reasons that varied among land uses.Where favored, diverse and abundant wild herbivores (mean of 1.7 t km⁻² on pro-wildlife ranches) can thrive even when sharing the landscape with a slightly higher biomass density of livestock (mean of 2.7 t km⁻²). Where not favored, only a few resilient wild species (e.g. gazelles and plains zebra) persist with high densities of livestock (mean of 4.6 t km⁻² on transitional ranches). Maintaining higher wild species diversity in the landscape will depend on the creation of a network of unfenced conservation areas in which livestock densities are persistently low or zero, which are sufficiently large to act as ‘sources’ of wild species that are prone to displacement by humans and livestock, and which generate benefits to community members that exceed opportunity costs.     

Dragonfly crisis in Japan: A likely consequence of recent agricultural habitat degradation

Many Japanese dragonfly species depend on habitat complexes maintained in rice paddy systems. We postulated that recent alterations to habitat complexes in paddy systems have had adverse effects on dragonfly populations, especially those ‘once common species’ that have come to depend primarily on paddy systems following losses of natural floodplain habitats. A high proportion of Japanese lentic dragonfly species depends on paddy fields or agricultural ponds that have been extensively degraded, while lotic species can often use both paddies and natural river systems. Thus we also postulated that lentic species are more susceptible to changes in agricultural habitats and are subject to higher extinction risks than lotic species. We aimed to extend previous work on estimating dragonfly extinction risk by developing mechanistic insights into the processes involved. Postulates were tested by analyzing relationships between (1) previous quantitative extinction risk assessments for dragonfly species and (2) species’ ecological characteristics (i.e., distribution range and habitat type [lentic or lotic]). Lentic species were disproportionately represented among those with elevated extinction risk. Species with large distribution ranges were also subject to higher extinction risks than those with narrower ranges, reflecting a driving force acting at a national scale (i.e., intensive degradation of paddy systems).     

Factoring species, non-species values and threats into biodiversity prioritisation across the ecoregions of Africa and its islands

Biodiversity in Africa, Madagascar and smaller surrounding islands is both globally extraordinary and increasingly threatened. However, to date no analyses have effectively integrated species values (e.g., richness, endemism) ‘non-species’ values (e.g., migrations, intact assemblages), and threats into a single assessment of conservation priorities. We present such an analysis for the 119 ecoregions of Africa, Madagascar and smaller islands. Biodiversity is not evenly distributed across Africa and patterns vary somewhat among taxonomic groups. Analyses of most vertebrates (i.e., birds, mammals, amphibians) tend to identify one set of priority ecoregions, while plants, reptiles, and invertebrates highlight additional areas. ‘Non-species’ biological values are not correlated with species measures and thus indicate another set of ecoregions. Combining species and non-species values is therefore crucial for assembling a comprehensive portfolio of conservation priorities across Africa. Threats to biodiversity are also unevenly distributed across Africa. We calculate a synthetic threat index using remaining habitat, habitat block size, degree of habitat fragmentation, coverage within protected areas, human population density, and the extinction risk of species. This threat index is positively correlated with all three measures of biological value (i.e., richness, endemism, non-species values), indicating that threats tend to be focused on the region’s most important areas for biodiversity. Integrating biological values with threats allows identification of two distinct sets of ecoregion priority. First, highly imperilled ecoregions with many narrow endemic species that require focused actions to prevent the loss of further habitat leading to the extinction of narrowly distributed endemics. Second, less threatened ecoregions that require maintenance of large and well-connected habitats that will support large-scale habitat processes and associated area-demanding species. By bringing these data together we can be much more confident that our set of conservation recommendations serves the needs of biodiversity across Africa, and that the contribution of different agencies to achieving African conservation can be firmly measured against these priorities.     

Restoring habitat permeability to roaded landscapes with isometrically-scaled wildlife crossings

Globally, human activities impact from one-third to one-half of the earth’s land surface; a major component of development involves the construction of roads. In the US and Europe, road networks fragment normal animal movement patterns, reduce landscape permeability, and increase wildlife-vehicle collisions, often with serious wildlife population and human health consequences. Critically, the placement of wildlife crossing structures to restore landscape connectivity and reduce the number of wildlife-vehicle collisions has been a hit-or-miss proposition with little ecological underpinning, however recent important developments in allometric scaling laws can be used to guide their placement. In this paper, we used cluster analysis to develop domains of scale for mammalian species groups having similar vagility and developed metrics that reflect realistic species movement dynamics. We identified six home range area domains; three quarters of 102 species clustered in the three smallest domains. We used HR^0.5 to represent a daily movement metric; when individual species movements were plotted against road mile markers, 71.2% of 72 species found in North America were included at distances of ?1 mi. The placement of wildlife crossings based on the HR^0.5 metric, along with appropriate auxiliary mitigation, will re-establish landscape permeability by facilitating wildlife movement across the roaded landscape and significantly improve road safety by reducing wildlife vehicle collisions.     

The efficacy of small-scale conservation efforts, as assessed on Australian golf courses

Habitat remnants on urban green-space areas (i.e. parks, gardens and golf courses) sometimes provide refuge to urban-avoiding wildlife, leading some to suggest these areas may play a role in wildlife conservation if they are appropriately designed and managed. The high densities observed on some green-space areas may however be attributed to external influences. Localised efforts to enhance the habitat value of urban green-space areas may therefore have little more than a cosmetic effect. This study investigated environmental factors influencing bird, reptile, mammal and amphibian diversity on Australian golf courses to assess the efficacy of small-scale conservation efforts. Abundance and species richness did not simply reflect local habitat qualities but were instead, partly determined by the nature of the surrounding landscape (i.e. the area of adjacent built land, native vegetation and the number of connecting streams). Vertebrate abundance and species richness were however, also associated with on-site habitat characteristics, increasing with the area of native vegetation (all vertebrates), foliage height diversity and native grass cover (birds), tree density, native grass cover and the number of hollows (mammals), woody debris, patch width and canopy cover (reptiles), waterbody heterogeneity and aquatic vegetation complexity (frogs). Localised conservation efforts on small land types can benefit urban-avoiding wildlife. Urban green-space areas can provide refuge to urban-avoiding vertebrates provided combined efforts are made at patch (management), local (design) and landscape (planning) scales.     

Incorporating parametric uncertainty into population viability analysis models

Uncertainty in parameter estimates from sampling variation or expert judgment can introduce substantial uncertainty into ecological predictions based on those estimates. However, in standard population viability analyses, one of the most widely used tools for managing plant, fish and wildlife populations, parametric uncertainty is often ignored in or discarded from model projections. We present a method for explicitly incorporating this source of uncertainty into population models to fully account for risk in management and decision contexts. Our method involves a two-step simulation process where parametric uncertainty is incorporated into the replication loop of the model and temporal variance is incorporated into the loop for time steps in the model. Using the piping plover, a federally threatened shorebird in the USA and Canada, as an example, we compare abundance projections and extinction probabilities from simulations that exclude and include parametric uncertainty. Although final abundance was very low for all sets of simulations, estimated extinction risk was much greater for the simulation that incorporated parametric uncertainty in the replication loop. Decisions about species conservation (e.g., listing, delisting, and jeopardy) might differ greatly depending on the treatment of parametric uncertainty in population models.     

Population viability and species interactions: Life outside the single-species vacuum

Population viability analysis (PVA) has become a widely used set of tools for evaluating relative extinction risk and prioritizing management options among imperiled populations. While PVA is a widely sanctioned tool in conservation biology, the field of population viability is in its infancy with respect to species interactions. In this paper, I review available methods for evaluating extinction risk when species interactions contribute significantly to population viability. This review includes an evaluation of six broad categories of species interactions (predation, disease, competition, mutualism, parasitism and host-parasitoid interactions) in population viability analysis, with a particular focus on predation as a case study. I first evaluated how often species interactions are considered when PVA is applied to population data from imperiled species. I identified 378 articles in commonly cited conservation journals, of which 24 attempted a viability analysis for populations threatened by interactions with other species. Most of these PVA’s treat a putative species interaction as a constant source of mortality rather than a coupled, dynamic population process. Second, I reviewed the literature to identify the availability of time-series of abundance data for two interacting species in which at least one species was threatened or endangered. Adequate time-series data were available for both species comprising an interacting pair in only 9 out of 407 papers reviewed. Third, I used a stochastic, fully stage-structured predator prey model to create time-series data (vital rates and projection matrices) in order to quantify the efficacy of two matrix-based, single-species PVA approaches. Simple single-species PVAs confound stochastic variation with population cycles induced by species interactions (in this case predation). As a result these models provide conservatively biased forecasts of viability. Unfortunately, the data needed to construct more complex PVA’s with feedback and multi-species stochasticity are rarely collected. I close with a discussion of key advances needed to “escape the population vacuum” in a move toward more realistic estimates of extinction risk.     

利用马尔柯夫过程预测蒙阴县土地利用/覆被格局变化

为了解蒙阴县土地利用/覆被的变化规律及其未来变化,由蒙阴县1997年和2007年2个时期的遥感图像获得的土地利用/覆被数据,确定土地利用/覆被的初始状态矩阵和转移概率矩阵,据此用马尔柯夫模型对研究区的土地利用/覆被格局的未来变化趋势进行了预测。结果表明:蒙阴县土地利用/覆被格局正处在一种变化状态,耕地、草地、水域及水利设施用地、未利用地面积在今后一段时期内仍呈减少趋势,到2017年耕地面积比例较2007年减少3.22%,林地、城镇村及工矿交通用地仍呈增加趋势,其中以林地增长幅度较大,到2017年其占比将达到43.45%。根据模拟结果可调整各类土地利用/覆被格局,为宏观决策提供科学依据。     

Extinction risk assessment of the world’s seagrass species

Seagrasses, a functional group of marine flowering plants rooted in the world’s coastal oceans, support marine food webs and provide essential habitat for many coastal species, playing a critical role in the equilibrium of coastal ecosystems and human livelihoods. For the first time, the probability of extinction is determined for the world’s seagrass species under the Categories and Criteria of the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species. Several studies have indicated that seagrass habitat is declining worldwide. Our focus is to determine the risk of extinction for individual seagrass species, a 4-year process involving seagrass experts internationally, compilation of data on species’ status, populations, and distribution, and review of the biology and ecology of each of the world’s seagrass species. Ten seagrass species are at elevated risk of extinction (14% of all seagrass species), with three species qualifying as Endangered. Seagrass species loss and degradation of seagrass biodiversity will have serious repercussions for marine biodiversity and the human populations that depend upon the resources and ecosystem services that seagrasses provide.     

A risk analysis methodology for assessing natural resources degradation

Risk analysis has been employed, amongst other things, both to estimate the probability of future water demand emergencies in reservoir systems (using simulation modelling), and to estimate environmental and public health risks (using empirical data). We assert that this framework, when coupled with simulation modelling, can be applied to examine and compare the impacts of resource exploitation, land use and production strategies which may cause land degradation. Our representation of risk analysis relies on the assumption that each land use strategy is associated with a risk of the system (i.e., social system, production system, ecosystem) attaining a subjectively unacceptable environmental condition (e.g. poor human nutrition, crop failure, degradation of a natural resource) sometime during a management planning period. The research methodology entails: (1) the identification of critical variables in the social and biological environment that are affected by exploitation and management of resources; (2) the identification through interviews, surveys, and research of regions of unacceptability in these variables that determine the dynamics of local environmental degradation; (3) the translation of resource policy and practice into a computer model of impact on the resource system; (4) many iterations of simulation of the system to determine the ‘risk of failing’ in each of the critical variables. The presentation of risk probabilities to decision-makers represents a reduction of many simulations into an understandable estimate of environmental impact. More importantly, risk analysis is potentially a learning tool for human system studies, and an interface for applied social science and ecological research.     

Removing erosion control projects increases bank swallow (Riparia riparia) population viability modeled along the Sacramento River, California, USA

Spatially-explicit population viability analysis (PVA) is a powerful method for modeling the extinction risk of populations that show variation over space and time. It is especially effective for comparing relative effect of different management scenarios on population dynamics. Here, I present a habitat patch-based PVA for a population of the California state-listed threatened bank swallow (Riparia riparia) nesting along the Sacramento River. This model incorporates the effects of habitat availability and location, density dependence, site fidelity, and stochasticity in survival and fecundity. River bank habitat patches suitable for this species were delineated using a geographic information systems (GIS) model of river bank height and were used in a PVA scenario analysis to assess the effects of habitat restoration—that could occur by removing bank erosion control projects (bank revetment)—on population viability. Sensitivity analysis showed that the model estimated probability of quasi-extinction (dropping below 2000 breeding pairs) ranged from 0 to 0.8 depending on the input parameters, with juvenile survival causing the greatest variability. However, comparing changes to the probability of quasi-extinction between the restored habitat scenario and current conditions showed a consistent 40-60% decrease in probability of quasi-extinction across all parameter combinations. The results of this research reaffirm the need for continued protection of the bank swallow as a listed species indicate that the removal of bank erosion control projects would increase viability of this population.     

Using Penrose distance to identify potential risk of wildlife–vehicle collisions

Knowledge of the relationship between wildlife and roads is important for management of wildlife–vehicle collisions, which represent a serious threat to many wildlife populations and to human life and property. Effective reduction of these threats requires identification of variables influencing collision locations, and the use of these variables in spatially-explicit predictive models. We used Penrose distance modeling and 61 confirmed bobcat (Lynx rufus) road mortality locations in southern Illinois, USA, to demonstrate a rapid and accurate technique for the spatial mapping of wildlife–vehicle collision risk. We used the Penrose distance statistic to quantify the similarity between the mean multivariate habitat signature at bobcat-collision areas and road sections throughout the study area. Habitat variables assessed included road-related variables (e.g., traffic volume) and land cover characteristics (e.g., mean patch area of the landscape). Bobcat-collision areas were characterized by smaller, less-clustered habitat patches and more, large independent patches of grass cover than were study area roadway sections in general. As expected for a generalist carnivore in highly-suitable habitat, risk mapping indicated that large sections of the roaded landscape had high similarity to bobcat-collision areas. Unlike other modeling techniques used to identify risk of road mortality, our method requires little field data collection and relies on readily available digital spatial data. This technique can be used by wildlife managers and road planners, and may be particularly important in reduction of road mortality for species such as the Iberian lynx (Lynx pardinus), Florida panther (Puma concolor coryi), and Texas ocelot (Leopardis pardalus), which exist in small populations fragmented by development, and are limited by road mortalities.     

Population viability of Cape mountain zebra in Gamka Mountain Nature Reserve, South Africa: the influence of habitat and fire

The small Cape mountain zebra population in Gamka Mountain Nature Reserve represents a third of the entire gene pool of this endangered species and is thus vital for it’s conservation. Presently, management of this population is largely hands off, with the belief that it will grow to levels which will allow it to form a source for the mixing of mountain zebra stocks in the future. The growth of this population however, has been slow and we investigated the influence of habitat and fire on this growth. Firstly, we used a diffusion model to perform a population viability analysis. This analysis indicated that the population had a low probability of attaining quasi-extinction in the next 50 years (G = 0.0032). However, our findings indicated that less than 30% of the reserve was suitable for mountain zebra and that the preferred habitat would have to be burnt at unnaturally short intervals to sustain the present growth. We therefore argue that the risk of quasi-extinction to this population is greater than predicted and suggest that management options need to be implemented to reduce this risk. These options include; translocation to another protected area; acquisition of adjacent land; burning preferred habitat at unnaturally short intervals; forming a conservancy with adjacent landowners; leasing cultivated land for pasture. We suggest that only the latter two options are likely to stimulate mountain zebra population growth in the short term and that these should receive immediate attention.     

New data on the status and distribution of the bush dog (Speothos venaticus): Evaluating its quality of protection and directing research efforts

The bush dog (Speothos venaticus), listed as CITES Appendix 1 - vulnerable, is a small (5-6 kg), rarely seen canid from Central and South America. The World Conservation Union Canid Specialist Group (IUCN CSG) recommended that research with this species focus on their basic ecology so that a data-driven conservation strategy can be formulated. Information on the bush dog, however, has been lacking since standard field techniques have had little or no success with this species. The S. venaticus Status and Distribution Survey was developed in an attempt to use indirect methodologies to determine the bush dog’s conservation status in the wild, its current distribution, and identify ecological needs by correlating habitat types to bush dog sightings. Survey responses and literature generated a database with 399 historic bush dog locations recorded between 1834 and 2004. These locational records were used to update the species’ range extent map, an important conservation planning tool. With year and precision of data accounted for, we analyzed land use coverage at known locations where bush dogs have historically been reported to evaluate the likelihood that the species persists in the area today. In addition, these locations provided training data for generation of potential distribution maps (i.e., areas of occupancy) using ecological niche modeling (i.e., Maximum Entropy) and bioclimatic data. These analyses revealed that 20% of the historic bush dog locations are associated with fragmented or altered habitat. These results allowed the status of bush dog habitat to be re-evaluated and areas that require more intensive research and protection to be identified.     

基于限制程度排序的卢龙县耕地质量提升重点区域划定研究

耕地是保证国家粮食安全的先决条件,也是保障社会安全及社会可持续发展的物质基础。中国耕地总体数量基数大,但整体的质量水平却很低。为明确耕地整治方向,针对不同地区进行不同重点的耕地整治,本文基于秦皇岛卢龙县农用地分等定级,构建耕地质量评价指标体系,运用得分因子标识法,确定限制因子组合类型,引入障碍度模型对限制因子组合进行修正,对卢龙县进行限制因子重点区域划定。结果显示,卢龙县15 981个耕地地块都存在高限制因子,汇总95种限制因子组合类型,共计43 909.71 hm~2。引入障碍度模型修正后卢龙县耕地可划分为5个主导限制因子重点区域:道路通达度限制因子主导区、地形坡度限制因子主导区、灌溉保证率限制因子主导区、农田防护林比率限制因子主导区和有效土层厚度限制因子主导区;其中农田防护林比率限制因子主导区整治面积最大,为37 680.91 hm~2,占耕地总面积的85.81%,主要分布在卢龙镇、燕河营镇和双望镇;其次为有效土层厚度限制因子主导区,面积为3 861.32 hm~2,主要分布在印庄乡;道路通达度限制因子主导区整治面积为1 876.16 hm~2,主要分布在双望镇;灌溉保证率限制因子主导区整治面积为319.44 hm~2,主要分布在燕河营镇;地形坡度限制因子主导区整治面积最小,为171.87 hm~2,占耕地总面积的0.39%,主要分布在刘田各庄镇。结合重点区域内限制因子可知,卢龙县主要限制因子以农田防护林比率和有效土层厚度为主,灌溉保证率和道路通达度为辅;在进行耕地整治时,可重点加强防护林建设,增加有效土层厚度,改良土壤,提高土壤肥力,加强农田设施及田间道路建设,确保粮食稳中增产,保障区域内粮食安全。研究结果可为丘陵山区整治规划、划定耕地质量提升重点区域提供技术支持,为今后耕地整治提供科学依据。     

Patch dynamics and the timing of colonization-abandonment events by male Kirtland’s Warblers in an early succession habitat

Habitat colonization and abandonment affects the distribution of a species in space and time, ultimately influencing the duration of time habitat is used and the total area of habitat occupied in any given year. Both aspects have important implications to long-term conservation planning. The importance of patch isolation and area to colonization-extinction events is well studied, but little information exists on how changing regional landscape structure and population dynamics influences the variability in the timing of patch colonization and abandonment events. We used 26 years of Kirtland’s Warbler (Dendroica kirtlandii) population data taken during a habitat restoration program (1979-2004) across its historical breeding range to examine the influence of patch attributes and temporal large-scale processes, specifically the rate of habitat turnover and fraction of occupied patches, on the year-to-year timing of patch colonization and abandonment since patch origin. We found the timing of patch colonization and abandonment was influenced by patch and large-scale regional factors. In this system, larger patches were typically colonized earlier (i.e., at a younger age) and abandoned later than smaller patches. Isolated patches (i.e., patches farther from another occupied patch) were generally colonized later and abandoned earlier. Patch habitat type affected colonization and abandonment; colonization occurred at similar patch ages between plantation and wildfire areas (9 and 8.5 years, respectively), but plantations were abandoned at earlier ages (13.9 years) than wildfire areas (16.4 years) resulting in shorter use. As the fraction of occupied patches increased, patches were colonized and abandoned at earlier ages. Patches were abandoned at older ages when the influx of new habitat patches was at low and high rates. Our results provide empirical support for the temporal influence of patch dynamics (i.e., patch destruction, creation, and succession) on local colonization and extinction processes that help explain large-scale patterns of habitat occupancy. Results highlight the need for practitioners to consider the timing of habitat restoration as well as total amount and spatial arrangement of habitat to sustain populations.     

Foraging in the fallows: Hunting patterns across a successional continuum in the Peruvian Amazon

Studies comparing hunting between secondary and mature forests are critical to understanding secondary forests’ potential as sustainable hunting grounds. I examined hunting across a successional continuum by surveying 67 households in three communities near the Cordillera Azul National Park, Peru, and analyzing the potential for sustainable hunting. Ninety-nine percent of households surveyed went hunting during the six-month study. Ninety-one species were recorded from seven vertebrate and invertebrate classes, with mammals the most hunted. Five percent of extraction events were species of concern on IUCN’s Red List. Households extracted significantly more, in terms of number of species, number of collection events, and biomass, from older forests (>20 y) than from young secondary (1-5 y) or old secondary forests (5-20 y). However, when extraction is measured per unit area (kg/km² or collection events/km²), households extracted more wildlife from old secondary forest. Households consumed meat at rates below Amazon regional averages. However, because human population densities are well above carrying capacity, current low harvest rates are likely a relic of past overharvests and do not reflect sustainability. Even if management focuses on source-sink dynamics with buffer zone hunting resupplied by protected area populations, long-term sustainability seems doubtful. As more agricultural clearing converts older forests to fields and fallows, the role of secondary forests in resource management plans will increase. The impact of high human population densities in the region means conservation and development programs should focus more on supplying alternative sources of protein and income and limiting immigration into the area.     

Biotic homogenization of the California flora in urban and urbanizing regions

Biotic homogenization, driven by native species losses and invasive species gains was investigated for the flora of California. Data from a variety of available databases were aggregated at the county level to examine patterns in county population density and growth in relation to floristic change. Based on population, California was divided into three zones: high (n = 9; 257-1320 people/km²), medium (n = 25; 28-177 people/km²), and low (n = 24; 1-24 people/km²) density counties. Examining patterns of rare plant occurrences among these counties revealed that high and medium density counties contained, on average, as many or more rare and endemic species than low density counties. The largest pool of these species, 48 percent of the 962 highly threatened taxa in California, is restricted to high and medium density counties. Thus, urban and urbanizing counties play a strategic role in maintaining a part of California’s flora that is both globally significant and threatened with extinction. Examining species losses and noxious weed additions across high density counties, reveals a consistent pattern of low similarity among species that have been extirpated from high density counties and a high similarity among noxious weeds that these counties now share. The consequence is that California’s urban county floras appear to be homogenizing. Examining homogenization using the entire flora for urban counties demonstrates that less similar counties become more similar. The effect of loss of rare species could outweigh the gain in exotics, under an assumption of strong extinction. Finally, a strong negative relationship between population density and the proportion of county land in public ownership suggests that high and medium density counties are in a poor position to protect rare plant populations on a localized basis.     

Parasite infection rates of impala (Aepyceros melampus) in fenced game reserves in relation to reserve characteristics

Under certain conditions reserves can pose a threat to wildlife conservation by increasing the transmission of parasites and pathogens. In this study, I investigated associations between reserve characteristics including area, density and species richness and parasite infection rates in impala (Aepyceros melampus). Using coprological methods to measure gastrointestinal parasitism rates of impala inhabiting five fully or partially fenced game reserves in central Kenya, I found that bovid species richness was correlated with parasite taxa richness across reserves, and that prevalence rates of multi-host strongyle nematodes were higher in reserves with more species. In addition, reserve size was also implicated as a potential predictor of infection risk. Overall, these results suggest that wildlife inhabiting highly diverse and small reserves may suffer from higher than normal rates of infection. Given the potential debilitating effects increases in parasitism can have on wildlife, these results underscore the importance of considering parasite transmission dynamics in the management of small, fenced protected areas.