Mating Behavior of Cephalonomia tarsalis (Ashmead) (Hymenoptera: Bethylidae) and the Effect of Female Mating Frequency on Offspring Production

The courtship behavior of Cephalonomia tarsalis, a solitary semiectoparasitoid of Oryzaephilus surinamensis, was investigated in the laboratory. Courtship behavior includes a series of stereotypic movements. Males play the most active role, executing the majority of courtship action, and females respond with relatively limited observable behaviors. Males typically keep antennae still during encounters with females prior to mounting, which may be correlated with recognition of the female's sexual status. After mounting, males display a series of movements on females, such as antennae touching female's antennae, antennae or mouth touching female's head or thorax, and walking around on female, which may serve to stimulate females towards increased receptivity. Females signal receptivity by assuming a stereotypical posture of remaining stationary, with head down, and antennae still in front of the body. The male then inserts his aedeagus and the pair copulates. After an average of 40.4 s of copulation, females signal the end of copulation by waving the antennae and moving away from the copulation site. Males continue copulating for a short time after females start moving but dismount soon thereafter. After dismounting, the two wasps move away from each other immediately, and they typically begin grooming. Neither males nor females exhibit mating preference based on mate's mating status in both choice and no-choice tests. The male is polygynous and the mated female can mate multiple times within the first 3 days after starting oviposition. However, female mating frequency does not affect the production of female progeny.     

The effects of host plant species on adult oviposition and larval performance of the aphid predator Aphidoletes aphidimyza

1. Although preference–performance relationships in insects are typically studied in a bi-trophic context, it is well known that host plants can affect both the preference and performance of natural enemies of herbivorous insects. 2. This study presents evidence from field and laboratory studies that two species of milkweeds, the putatively less defended Asclepias incarnata and the putatively more defended Asclepias syriaca, differentially affect adult oviposition and larval performance in Aphidoletes aphidimyza, an aphid-feeding predatory midge, independent of aphid density. 3. Host plant species affected predatory fly larvae abundance by a factor of 50 in the field and a factor of 8 in the laboratory. Larval and adult emergence rates in our laboratory studies provided strong evidence for reduced performance on A. syriaca. Oviposition in choice and no-choice settings provided some evidence for preference for A. incarnata, and a potentially suppressive effect of A. syriaca. 4. The results provide limited support for the hypothesis that natural selection can lead to positive correlations between adult oviposition preferences and larval performance upon various food sources, even when predatory insects oviposit onto host plants of their herbivorous prey. 5. Preference and performance are not perfectly aligned in this system, however, because ovipositing females do not reject A. syriaca entirely. Potential explanations for mismatches between preference and performance in this system include the neural constraints associated with being a generalist, adaptive time-limited foraging strategies, and unique evolutionary histories of laboratory colonies compared with wild insects.     

Seasonal Shifts in Nocturnal Habitat Use by Coastal Bat Species

Sensitivity of bats to land use change depends on their foraging ecology, which varies among species based on ecomorphological traits. Additionally, because prey availability, vegetative clutter, and temperature change throughout the year, some species may display seasonal shifts in their nocturnal habitat use. In the Coastal Plain of South Carolina, USA, the northern long-eared bat (Myotis septentrionalis), southeastern myotis (Myotis austroriparius), tri-colored bat (Perimyotis subflavus), and northern yellow bat (Lasiurus intermedius) are species of conservation concern that are threatened by habitat loss. Our objective was to identify characteristics of habitat used by these species during their nightly active period and compare use between summer and winter. We conducted acoustic surveys at 125 sites during May–August and at 121 of the same 125 sites December–March 2018 and 2019 in upland forests, bottomland forests, fields, ponds, and salt marsh and used occupancy models to assess habitat use. The northern long-eared bat and southeastern myotis (i.e., myotis bats) used sites that were closer to hardwood stands, pine stands, and fresh water year-round. We did not identify any strong predictors of tri-colored bat habitat use in summer, but during winter they used bottomland forests, fields, and ponds more than salt marsh and upland forests. During summer and winter, northern yellow bats used sites close to fresh water and salt marsh. Additionally, during summer they used fields, ponds, and salt marsh more than upland and bottomland forests, but in winter they used bottomland forests, fields, and ponds more than upland forest and salt marsh. Our results highlight important land cover types for bats in this area (e.g., bottomland forests, ponds, and salt marsh), and that habitat use changes between seasons. Accounting for and understanding how habitat use changes throughout the year will inform managers about how critical habitat features may vary in their importance to bats throughout the year. © 2021 The Wildlife Society.     

Characterization of moorland vegetation and the prediction of bird abundance using remote sensing

Aims To characterize and identify upland vegetation composition and height from a satellite image, and assess whether the resulting vegetation maps are accurate enough for predictions of bird abundance. Location South‐east Scotland, UK. Methods Fine‐taxa vegetation data collected using point samples were used for a supervised classification of a Landsat 7 image, while linear regression was used to model vegetation height over the same image. Generalized linear models describing bird abundance were developed using field‐collected bird and vegetation data. The satellite‐derived vegetation data were substituted into these models and efficacy was examined. Results The accuracy of the classification was tested over both the training and a set of test plots, and showed that more common vegetation types could be predicted accurately. Attempts to estimate the heights of both dwarf shrub and graminoid vegetation from satellite data produced significant, but weak, correlations between observed and predicted height. When these outputs were used in bird abundance–habitat models, bird abundance predicted using satellite‐derived vegetation data was very similar to that obtained when the field‐collected data were used for one bird species, but poor estimates of vegetation height produced from the satellite data resulted in a poor abundance prediction for another. Conclusions This pilot study suggests that it is possible to identify moorland vegetation to a fine‐taxa level using point samples, and that it may be possible to derive information on vegetation height, although more appropriate field‐collected data are needed to examine this further. While remote sensing may have limitations compared with relatively fine‐scale fieldwork, when used at relatively large scales and in conjunction with robust bird abundance–habitat association models, it may facilitate the mapping of moorland bird abundance across large areas.     

Virus population extinction via ecological traps

Populations are at risk of extinction when unsuitable or when sink habitat exceeds a threshold frequency in the environment. Sinks that present cues associated with high-quality habitats, termed ecological traps, have especially detrimental effects on net population growth at metapopulation scales. Ecological traps for viruses arise naturally, or can be engineered, via the expression of viral-binding sites on cells that preclude viral reproduction. We present a model for virus population growth in a heterogeneous host community, parameterized with data from populations of the RNA bacteriophage Φ6 presented with mixtures of suitable host bacteria and either neutral or trap cells. We demonstrate that viruses can sustain high rates of population growth in the presence of neutral non-hosts as long as some host cells are present, whereas trap cells dramatically reduce viral fitness. In addition, we demonstrate that the efficacy of traps for viral elimination is frequency dependent in spatially structured environments such that population viability is a nonlinear function of habitat loss in dispersal-limited virus populations. We conclude that the ecological concepts applied to species conservation in altered landscapes can also contribute to the development of trap cell therapies for infectious human viruses.     

Niche properties of Central European spiders: shading, moisture and the evolution of the habitat niche

Aim  Niche theory emphasizes the importance of environmental conditions for the distribution and abundance of species. Using a macroecological approach our study aimed at identifying the important environmental gradients for spiders. We generated numerical values of niche position and niche width. We also investigated relationships between these niche properties as well as the degree of phylogenetic conservatism in order to draw conclusions about the evolution of the habitat niche.
Location  Central Europe: lowlands of Austria, Belgium, Germany, Luxembourg, the Netherlands and Switzerland.
Methods  We analysed 244 published spider communities from 70 habitat types by correspondence analysis. The resulting community scores were used to test for correlations with habitat characteristics. Species scores were used to derive niche position (mean scores) and niche width (standard deviation of scores). To test for niche conservatism we estimated variance components across the taxonomic hierarchy.
Results  The first two axes of the correspondence analysis were correlated with shading and moisture, respectively. Niche width had a hump-shaped relationship to both environmental gradients. β-diversity was strikingly higher in open habitats than in forests. Habitat niche conservatism was lower than phylogenetic conservatism in body size.
Main conclusions  Environmental factors are important drivers for the β-diversity of spiders, especially across open habitats. This underlines the importance of preserving the whole range of moisture conditions in open habitats. Narrow niches of species occurring at the ends of both environmental gradients indicate that adaptations to extreme habitats lead to constraints in ecological flexibility. Nevertheless, the habitat niche of species seems to evolve much faster than morphological or physiological traits.     

Risks of Biological Invasion on the Belt and Road

1. Download high-res image (299KB)
2. Download full-size image

     

七姊妹山常绿落叶阔叶混交林物种多样性格局及其环境解释

依托七姊妹山自然保护区6 hm²森林动态监测样地研究平台,基于样地和物种基本信息数据,采用多元回归树和冗余分析研究方法,探讨地形因子对生境的塑造作用及物种分布特征,分析不同群丛类型下物种多样性的变化规律。结果表明：(1)依据“1 SE”规则,4次分割依次以海拔(1 453 m)、坡度(23.13°)、海拔(1 398 m)、凹凸度(4.094)为分界点可将150个样地分为5个群丛。(2)冗余分析表明地形因子对物种分布解释量为0.077 6,解释率为16.36%,各环境因子对物种分布的解释力度依次为：海拔>坡度>凹凸度;坡向与物种的分布无显著相关性。(3)5个群丛中立木密度与胸高截面积最高的均为群丛5(527.4株/400 m²;3.495 cm²/株),立木密度与平均胸高截面积最低为群丛4(225.4株/400 m²;3.057 cm²/株)。(4)5个群丛中Shannon Winener丰富度指数与Simpson优势度指数最高的均为群丛2,最低的为群丛5,物种多样性尺度效应明显;Pielou均匀度指数最高为群丛4,最低为群丛5。(5)两两群丛间Jaccard相似性系数最低为群丛1 群丛2(0.331),最高的为群丛4 群丛5(0.645),海拔对β多样性格局影响较大。研究认为,七姊妹山自然保护区6 hm²样地地形因子对该区域生境的塑造具有一定作用,海拔、坡度、凹凸度组成的“环境筛”影响了该区域的物种分布及多样性格局。     

Nest success of northern bobwhite on managed and unmanaged landscapes in southeast Iowa

Range-wide declines in northern bobwhite populations (Colinus virginianus) have been attributed to concomitant loss of breeding habitat. Bobwhite management efforts to restore this habitat resource can be informed by empirical studies of associations between breeding success and multi-scale habitat attributes. We compared bobwhite nest success in 2 southern Iowa landscapes as a function of microhabitat and landscape composition. Lake Sugema Fish and Wildlife Area (LSWA) was managed to promote bobwhite recruitment, and Harrisburg Township (HT) was an adjacent landscape dominated by private agricultural production. Survival rate modeling based on telemetry data provided evidence for age-specific daily nest survival rate. Daily survival rates decreased as nest age increased, but the decline was more severe at HT. Nest survival at LSWA (S = 0.495, SE = 0.103) was nearly twice that on HT (S = 0.277, SE = 0.072). We found no evidence that habitat composition or spatial attributes within 210 m of a nest site significantly influenced nest success. Forb canopy at the nest site had a positive influence on nest success at HT but not at LSWA. We suggest nesting habitat with greater forb canopy cover will increase the opportunity for nesting success in landscapes with limited nesting habitat. © 2010 The Wildlife Society.