Diagnostic Genetic Marker That Differentiates Eastern Fox Squirrels From Eastern Gray Squirrels

Abstract The Delmarva fox squirrel (Sciurus niger cinereus) has been listed as endangered by the United States Department of Interior since 1967. A high-priority task for the recovery of this taxon is to determine its current geographic distribution. Toward this end, we have identified a microsatellite locus that unambiguously differentiates Delmarva fox squirrels from eastern gray squirrels (S. carolinensis), which frequently co-occur with Delmarva fox squirrels. Analysis of this marker in noninvasively collected hair samples will allow unequivocal identification of localities occupied by Delmarva fox squirrels with a minimum investment of funds, time, and effort because handling individuals will be unnecessary. This protocol will expedite site review in connection with the Endangered Species Act consultation process.     

Nest Site Selection by Western Gray Squirrels at Their Northern Range Terminus

ABSTRACT The western gray squirrel (Sciurus griseus) in Washington, USA, is limited to 3 disjunct areas and is a state threatened species. Information is lacking for the North Cascades population, which is the northernmost population for the species. Squirrels in this population exist without oaks (Quercus spp.) that provide forage and cavities for maternal nests elsewhere in their range. During May 2003 to August 2005, we studied selection of nest sites and nest trees by 18 radiocollared squirrels in Okanogan County, Washington. Without oak cavities, females reared their young in dreys. General nest-tree characteristics were similar to characteristics of western gray squirrel nest trees in Southeastern Cascades: relatively tall ponderosa pines (Pinus ponderosa) ≥ 40 cm diameter at breast height. Results from conditional logistic models determined that the odds of a squirrel selecting a tree for nesting increased with greater diameter at breast height and with infection by dwarf mistletoe (Arceuthobium spp.). Nest sites with high selection probability by squirrels had greater basal area and number of tree species than available unselected sites. Retention of forest patches that include a mix of conifer species or conifer and deciduous trees and moderate to high basal area could promote nesting opportunities, connectivity for arboreal travel, as well as abundance and diversity of hypogeous fungi. Experiments to test the efficacy of retaining untreated patches of varying size (including trees infected with mistletoe) on nesting by western gray squirrels within stands managed for fire suppression and forest health would provide important information about the effects of forest fuel management on arboreal wildlife.     

Diets of native and introduced tree squirrels in Washington

Competition for food resources can be a primary mechanism for displacement of native species by introduced species. Investigation of dietary partitioning between potential competitors and spatiotemporal variability in food resources can reveal contested food items and intensity of competition. Introduced eastern gray squirrels (Sciurus carolinensis) have been implicated as competitors with western gray squirrels (S. griseus) and Douglas’ squirrels (Tamiasciurus douglasii), but little is known about interactions among these species. We collected foraging observations and fecal pellets of sympatric gray and Douglas’ squirrels trapped and radio-tracked in western Washington, USA, from 2007 to 2012. We compared food resources consumed across species, seasons, and years to evaluate dietary overlap and the potential for competitive interactions. All squirrel species ate hypogeous fungi throughout all seasons; spores of several genera were present in 272 of 275 fecal samples and observed in all months. Rhizopogon, Geopora, and Melanogaster spp. occurred in most fecal pellets for all squirrels, but the diet of the Douglas’ squirrels had slightly lower richness of hypogeous fungi than gray squirrels. Although foraging observations suggest that eastern and western gray squirrels shared important dietary items such as acorns, strong differences in consumption of seeds of a common conifer may facilitate their coexistence. Our results suggest that dietary overlap among arboreal squirrels could lead to competitive interactions during periods of food scarcity, but subtle differences may be sufficient to permit long-term coexistence. Tree squirrels in Washington would likely benefit from forest management practices that promote or sustain robust crops of hypogeous fungi. © 2019 The Wildlife Society.     

Field Use of Isoflurane for Safe Squirrel and Woodrat Anesthesia

Abstract: We evaluated a chamber and nose cone method of isoflurane delivery for anesthetizing eastern gray squirrels (Sciurus carolinensis; summer n = 43, winter n = 48) and Allegheny woodrats (Neotoma magister; summer n = 24, winter n = 13) for use when pain or stress was possible from sampling procedures. Mean induction time for squirrels (from beginning of isoflurane administration to safe removal from trap), was 4.63 ± 0.58 minutes. Squirrels awoke more quickly in summer (1.40 ± 0.15 min) than in winter (3.62 ± 0.24 min) after removal of the nose cone. We manually restrained woodrats and administered the nose cone for 0.5 minutes to each animal. Woodrats awoke after 4.76 ± 0.58 minutes following the final dose of isoflurane for both seasons. These methods are useful for working with small mammals in the field and provide an appropriate anesthetic when there may be more than slight pain or distress.     

Complex relationships between physiological stress and endoparasite infections in natural populations

Short-term elevation of glucocorticoids (GCs) is one of the major physiological mechanisms by which vertebrates cope with challenging environmental or social factors (stressors). However, when exposure to stressors occurs repeatedly or over a prolonged period of time, animals may experience chronic elevation of GCs, which reduces the immune response efficiency and can lead to higher intensity of parasitic infection. Here, we used invasive gray squirrels Sciurus carolinensis introduced in Northern Italy and their 2 most prevalent gastrointestinal parasites, the nematode Strongyloides robustus and coccidia of the genus Eimeria, as a model to investigate relationships among macroparasite infection and concentrations of fecal glucocorticoid metabolites (FGMs), an integrated measure of circulating GCs. Our results revealed an association of FGMs with infection by St. robustus, but not with coccidia. Individuals with higher FGMs appear to be responsible for the greatest St. robustus egg shedding within gray squirrel populations, thus possibly acting as superspreaders. However, FGMs were negatively associated with adult St. robustus, suggesting that the abundance of adults of this nematode species does not induce elevation in FGMs, but is only affected by it through immune-mediated effects on its fecundity. Finally, the relationship between St. robustus (both eggs and adult parasites) and FGMs was not linear, suggesting that only high levels of physiological stress influence parasite infection. Our findings highlight that the direction and magnitude of the stress–infection relationship may depend not only on the specific host–parasite system, but also on the different life stages of the same parasite.     

Timescale analyses of fluctuations in coexisting populations of a native and invasive tree squirrel

1. Competition from invasive species is an increasing threat to biodiversity. In Southern California, the western gray squirrel (Sciurus griseus, WGS) is facing competition from the fox squirrel (Sciurus niger, FS), an invasive congener.
2. We used spectral methods to analyze 140 consecutive monthly censuses of WGS and FS within a 11.3 ha section of the California Botanic Garden. Variation in the numbers for both species and their synchrony was distributed across long timescales (>15 months).
3. After filtering out annual changes, concurrent mean monthly temperatures from nearby Ontario Airport yielded a spectrum with a large semi‐annual peak and significant spectral power at long timescales (>28 months). The cospectrum between WGS numbers and temperature revealed a significant negative correlation at long timescales (>35 months). Cospectra also revealed significant negative correlations with temperature at a six‐month timescale for both WGS and FS.
4. Simulations from a model of two competing species indicate that the risk of extinction for the weaker competitor increases quickly as environmental noise shifts from short to long timescales.
5. We analyzed the timescales of fluctuations in detrended mean annual temperatures for the time period 1915–2014 from 1218 locations across the continental USA. In the last two decades, significant shifts from short to long timescales have occurred, from <3 years to 4–6 years.
6. Our results indicate that (i) population fluctuations in co‐occurring native and invasive tree squirrels are synchronous, occur over long timescales, and may be driven by fluctuations in environmental conditions; (ii) long timescale population fluctuations increase the risk of extinction in competing species, especially for the inferior competitor; and (iii) the timescales of interannual environmental fluctuations may be increasing from recent historical values. These results have broad implications for the impact of climate change on the maintenance of biodiversity.

     

福建大仙峰杜鹃属植物资源特征及其应用研究

通过样线法调查福建省大田县大仙峰野生杜鹃属(Rhododendron)植物资源,掌握其种类及形态特征、适生环境、花期等特性。大仙峰共记录11种杜鹃属植物,分属4亚属,其中映山红亚属3种、马银花亚属4种、常绿杜鹃亚属3种、羊踟蹰亚属1种,种类不同,花期、花色均有所不同。从春季开始至夏季均可欣赏到不同景色的杜鹃。对溪畔杜鹃(R. rivulare)、羊踯躅(R. molle)2种杜鹃进行扦插育苗,二者成活率皆在45%以上,达到资源保存的目的。大仙峰杜鹃属植物种质资源丰富,类型多样,分布范围广,有较大的开发潜力和应用前景。     

Interactions between European rabbits and native marsupials in the absence of terrestrial predators

European rabbits (Oryctolagus cuniculus) are ubiquitous across Australia and have the ability to influence native species directly and indirectly. Despite this, limited research focuses on interspecific interactions between rabbits and native mammals. We aimed to determine how site occupancy, detection probability, and temporal activity periods of native mammals changed in response to the presence or absence of rabbits. We monitored three native mammal species using 85 camera traps in a systematic grid at Mt Rothwell Conservation and Research Reserve (Victoria, Australia), a predator-barrier fenced reserve with two distinct sections—an area with rabbits and an area without. Bettongs (rufous Aepyprymnus rufescens and eastern Bettongia gaimardi), eastern barred bandicoots (Perameles gunni), and southern brown bandicoots (Isoodon obesulus) had a naïve site occupancy of 71%, 42%, and 24%, respectively. Site occupancy for both bandicoot species decreased in areas with more clumping grass with eastern barred bandicoot occupancy increasing with leaf litter cover, and southern brown bandicoots with vegetation height. Rabbit presence did not influence site occupancy of any species. Species detection probabilities were generally positively associated with open vegetation and rabbit presence, except for southern brown bandicoots which were more detectable without rabbits. Both bandicoot species shifted their peak activity periods in the absence of rabbits having an earlier, and more defined activity peak. Our results demonstrate that the presence of rabbits in the absence of invasive predators may not influence the site occupancy of co-occurring native mammals, however, could influence the behaviour of smaller co-occurring mammals, either directly or indirectly.     

Behavioral and Genetic Differentiation Between Native and Introduced Populations of the Argentine Ant

In this paper, we examine the hypothesis that reduced intraspecific aggression underlies the competitive prowess of Argentine ants in their introduced range. Specifically, we test three predictions of this hypothesis by comparing the genetic diversity, behavior, and ecology of Argentine ants in their native range to introduced populations. Differences between native and introduced populations of Argentine ants were consistent with our predictions. Introduced populations of the Argentine ant appear to have experienced a population bottleneck at the time of introduction, as evidenced by much reduced variation in polymorphic microsatellite DNA markers. Intraspecific aggression was rare in introduced populations but was common in native populations. Finally, in contrast to the Argentine ant's ecological dominance throughout its introduced range, it did not appear dominant in the native ant assemblages studied in Argentina. Together these results identify a possible mechanism for the widespread success of the Argentine ant in its introduced range.     

Thermal adaptation affects interactions between a range‐expanding and a native odonate species

1. Increasing temperature and invading species may interact in their effects on communities. In this study, we investigated how rising temperatures alter larval interactions between a naturally range‐expanding dragonfly, Crocothemis erythraea, and a native northern European species, Leucorrhinia dubia. Initial studies revealed that C. erythraea grow up to 3.5 times faster than L. dubia at temperatures above 16 °C. As a result, we hypothesised that divergent temperature responses would lead to rapid size differences between coexisting larvae and, consequently, to asymmetric intraguild predation at higher ambient temperatures. 2. Mortality and growth rates were measured in interaction treatments (with both species present) and non‐interaction controls (one species present) at four different temperature regimes: at an ambient temperature representative of central Germany, where both species overlap in distribution, and at temperatures increased by 2, 4 and 6 °C. 3. The mortality of C. erythraea did not differ between treatment and control. In contrast, mortality of L. dubia remained similar over all temperatures in the controls, but increased with temperature in the presence of the other species and was significantly higher there than in the controls. We concluded that L. dubia suffered asymmetric intraguild predation, particularly at increased temperature. Reduced growth rate of L. dubia in the interaction treatment at higher temperatures also suggested asymmetric competition for prey in the first phase of the experiment. 4. The results imply that the range expansion of C. erythraea may cause reduction in population size of syntopic L. dubia when temperature rises by more than 2 °C. The consequences for future range patterns, as well as other factors that may influence the interaction in nature, are discussed.     

Poxviral Disease in Red Squirrels Sciurus vulgaris in the UK: Spatial and Temporal Trends of an Emerging Threat

The squirrel poxvirus (SQPV) is the probable mediator of apparent competition between the introduced invading gray squirrel (Sciurus carolinensis) and the red squirrel (Sciurus vulgaris) in the UK, and modeling studies have shown that this viral disease has had a significant impact on the decline of the red squirrel in the UK. However, given our limited understanding of the epidemiology of the disease, and more generally the effects of invasive species on parasite ecology, there is a need to investigate the transmission dynamics and the relative pathogenicity of the virus between species. We aimed to increase our knowledge of these processes through an empirical study in which we: (i) used pathological signs and transmission electron microscopy (TEM) to diagnose SQPV disease in red squirrels found dead during scanning surveillance between 1993 and 2005; (ii) detected antibody to SQPV using an enzyme-linked immunosorbent assay (ELISA) in the same animals; and (iii) mapped cases of the disease, and the gray squirrel distribution, using a geographical information system. We analyzed the distribution of cases of SQPV disease according to woodland type, a measure of squirrel density. SQPV disease occurred only in areas of England also inhabited by seropositive gray squirrels, and as the geographical range of gray squirrels expanded, SQPV disease occurred in these new gray squirrel habitats, supporting a role for the gray squirrel as a reservoir host of the virus. There was a delay between the establishment of invading gray squirrels and cases of the disease in red squirrels which implies gray squirrels must reach a threshold number or density before the virus is transmitted to red squirrels. The spatial and temporal trend in SQPV disease outbreaks suggested that SQPV disease will have a significant effect on Scottish populations of red squirrels within 25 years. The even spread of cases of disease across months suggested a direct rather than vector-borne transmission route is more likely. Eight juvenile and sub-adult free-living red squirrels apparently survived exposure to SQPV by mounting an immune response, the first evidence of immunity to SQPV in free-living red squirrels, which possibly suggests a changing host-parasite relationship and that the use of a vaccine may be an effective management tool to protect remnant red squirrel populations.     

入侵种西花蓟马与其它昆虫的种间竞争

西花蓟马Frankliniella occidentalis作为一种重要的入侵害虫,在全球范围的入侵过程中,为获取更多资源以建立自己的种群,势必会和处于同一营养级的昆虫发生种间竞争。本文对近年来有关西花蓟马与其它种蓟马、粉虱及叶螨等昆虫种间竞争的研究进行了综述,分析了温度、CO 2、寄主植物、农药和天敌等主要因素在竞争取代中的作用,并对今后的研究方向以及种间竞争的研究方法进行了讨论,以期为揭示西花蓟马在我国的种群动态和变化规律奠定基础。     

Differential effect of inter- and intraspecific competition on the performance of invasive and native Taraxacum species

Inter- and intraspecific competitive abilities are significant determinants of invasive success and the ecological impact of non-native plants. We tested two major hypotheses on the competitive ability of invasive species using invasive (Taraxacum officinale) and native (T. platycarpum) dandelions: differential interspecific competitive ability between invasive and native species and the kin recognition of invasive species. We collected seeds from two field sites where the two dandelion species occurred nearby. Plants were grown alone, with kin (plants from the same maternal genotype) or strangers (plants from different populations) of the same species, or with different species in a growth chamber, and the performance at the early developmental stage between species and treatments was compared. The invasive dandelions outcompeted the native dandelions when competing against each other, although no difference between species was detected without competition or with intraspecific competition. Populations of native species responded to interspecific competition differently. The effect of kinship on plant performance differed between the tested populations in both species. A population produced more biomass than the other populations when grown with a stranger, and this trend was manifested more in native species. Our results support the hypothesis that invasive plants have better competitive ability than native plants, which potentially contributes to the establishment and the range expansion of T. officinale in the introduced range. Although kin recognition is expected to evolve in invasive species, the competitive ability of populations rather than kinship seems to affect plant growth of invasive T. officinale under intraspecific competition.