Preservation potential of Katharina tunicata and Mopalia muscosa (Mollusca, Polyplacophora) on two rocky shores of San Juan Island, Washington, USA

Taphonomic analyses of modern Katharina tunicata and Mopalia muscosa valves (Mollusca, Polyplacophora) collected from San Juan Island, Washington, USA, demonstrate that preservation potential of chitons varies by species and locality. Damage levels observed in the valves reflect differences in extrinsic environmental conditions, but intrinsic characters affect response of the skeletal material to local processes. Although both are more likely to become fossils at the lower energy site, K. tunicata valves in poor condition are more likely to occur than poor-condition M. muscosa valves at either site. Mopalia muscosa valves are least likely to be preserved at the higher energy site. Katharina tunicata valves appear more resistant to destruction than M. muscosa valves, suggesting that the former are more likely to become fossilized. The preservation potential of the three types of valves (normally one head, six medials, and one tail per individual) differs for both species. Medials are more likely to be preserved than either terminal valve of K. tunicata or M. muscosa . Head valves are least likely to be preserved, but K. tunicata heads are less likely to be preserved than M. muscosa heads. The biases are not due to greater frequency of medials, because valves do not occur in the 3:1 ratio seen in living animals. Divergence from expected ratios and variation in taphonomic condition for all three valve types in modern environments agrees with observations in the fossil record. The rarity of fossil chitons may be due to biases against preservation rather than absence in ancient environments.     

Taphonomy of modern communal burrow systems of the Plains vizcacha (Lagostomus maximus,Chinchillidae) in the Pampas region of Argentina: implications for the fossil record

The Plains vizcacha (Lagostomus maximus) is one of the largest rodents in South America. They live in communal burrow systems (vizcacheras) shaped by complex subterranean galleries which produce a strong impact on the local landscape. This paper presents the results of an actualistic study conducted with abandoned vizcacheras from the Pampas region of Argentina. The main objective is to evaluate the role of this rodent in the formation of the fossil record. Results indicate that the Plains vizcacha is responsible for the mixing, accumulation, and transport of materials; such as sticks, caliche, dung, feces, and abundant bone remains. Their burrowing activity and the accumulating habits, modifies the landscape, creating environments conducive to the buildup of objects and the reuse by different animals. These characteristics result in very complex associations of materials of different origins; making this rodent an important taphonomic agent with the potential to significantly impact the fossil record.     

Analysis of environmental factors and their effects on fungal spores in the atmosphere of a tropical urban area (San Juan,Puerto Rico)

In Puerto Rico, respiratory diseases affect a significant percentage of the population, and it is possible that the environmental factors unique to the island, such as easterly winds, dense vegetation, and high humidity, may increase the concentration of airborne biological particulates that could distress susceptible individuals. As most studies characterized fungal spores and pollen in temperate zones, we wanted to describe their concentrations in a tropical zone. The Allergenco^® (MK3) spore trap was used to monitor airborne spores and pollen concentrations for 12 months starting on May 2005. During the length of the study, silicone grease-coated microscope slides captured 12 impacts daily, which were then stained with calcofluor and observed under the microscope with bright field and ultraviolet light. Atmospheric conditions were recorded with the Precision Weather Station^®. Precipitation, dew point, and relative humidity promote the presence of fungal spores in San Juan throughout the year, with basidiospores being the most frequent. Spore concentrations were higher during the early morning hours all the year around. Wind and gusts were dispersal factors, and humidity and the dew point favored the release of spores into the atmosphere. In contrast to spores, pollens were not found to be affected by any of the meteorological factors and no distinctive patterns were found. Describing how airborne spores and pollens, many of which have allergenic potential, behave in the tropics, such as in San Juan, Puerto Rico, could be used to design preventive measures for the benefit of the sensitized population. Information about the presence and abundance of aeroallergens will assist in the diagnosis of allergic rhinitis and asthma on the island.     

Population dynamics of little brown bats (Myotis lucifugus) at summer roosts: Apparent survival,fidelity, abundance,and the influence of winter conditions

1. White‐nose syndrome (WNS) has caused the death of millions of bats, but the impacts have been more difficult to identify in western North America. Understanding how WNS, or other threats, impacts western bats may require monitoring other roosts, such as maternity roosts and night roosts, where bats aggregate in large numbers.
2. Little brown bats (Myotis lucifugus) are experiencing some of the greatest declines from WNS. Estimating survival and understanding population dynamics can provide valuable data for assessing population declines and informing conservation efforts.
3. We conducted a 5‐year mark–recapture study of two M. lucifugus roosts in Colorado. We used the robust design model to estimate apparent survival, fidelity, and abundance to understand population dynamics, and environmental covariates to understand how summer and winter weather conditions impact adult female survival. We compared the fidelity and capture probability of M. lucifugus between colonies to understand how bats use such roosts.
4. Overwinter survival increased with the number of days with temperatures below freezing (β > 0.100, SE = 0.003) and decreased with the number of days with snow cover (β < −0.40, SE < 0.13). Adult female fidelity was higher at one maternity roost than the other. Overwinter and oversummer adult female survival was high (>0.90), and based on survival estimates and fungal‐swabbing results, we believe these populations have yet to experience WNS.
5. Recapture of M. lucifugus using antennas that continuously read passive integrated transponder tags allows rigorous estimation of bat population parameters that can elucidate trends in abundance and changes in survival. Monitoring populations at summer roosts can provide unique population ecology data that monitoring hibernacula alone may not. Because few adult males are captured at maternity colonies, and juvenile males have low fidelity, additional effort should focus on understanding male M. lucifugus population dynamics.

     

Temperature influence on development and calcification of Herpetocypris brevicaudata Kaufmann, 1900 (Crustacea: Ostracoda) under experimental conditions

Cultures of the freshwater ostracod Herpetocyprisbrevicaudata were kept under laboratory conditions in ordertostudy effects of water temperature on development time andcalcification process. Four culture temperatures were used:12.4,14.6, 19.8 and 23.3 °C.H. brevicaudata cultured at 19.8 and 23.3 °Cshowedhigher survival rate and faster development than thosecultured at12.4 and 14.6 °C. Water temperature also has a clearinfluence on the degree of calcification of the ostracodshells.For H. brevicaudata, the 15–19 °C temperaturerangeconstitutes a threshold below which Ca content of valvessignificantly decreases. Time required to calcify is alsolongerbelow this threshold. The increase of the calcification timedue tolower water temperatures seems to induce low survivalrates.     

Effect of intrinsic and extrinsic factors on the variability of echolocation pulses of Myotis nigricans (Schinz, 1821) (Chiroptera: Vespertilionidae)

Bats may exhibit plasticity in echolocation pulses as response to intrinsic and extrinsic factors, and the estimation of the magnitude of such variation can provide confidence in acoustic monitoring. Myotis nigricans (Schinz, 1821) is a widely distributed but relatively understudied Neotropical species for which, during fieldwork, we found maternity colonies in the Lagunas de Montebello National Park, in Chiapas, South-east Mexico, and no previous information in the area. Therefore, we aimed to provide an acoustic characterization on the basis of intraspecific variability for its recognition using bat detectors. For this purpose, we examined the moulding of shape, frequency-based and time-based acoustic parameters, specifically by the effect of age group (sub-adults vs. adults) and acoustic environment (open space vs. background vegetation). By graphic comparison of echolocation pulses between acoustic environments, we observed changes in shape by an increase in bandwidth and steeper modulation along background vegetation. Statistically, on univariate basis, we did not find a significant effect of age group, but we did of acoustic environment, specifically on highest frequency (higher average), duration (shorter average) and interpulse interval (shorter average) along background vegetation. On multivariate basis, we confirmed shorter average interpulse interval along background vegetation. The overall classification accuracy was relatively high (82.22%): 80% in open space and 84% along background vegetation. Our work reinforces previous knowledge about sound constraints imposed by vegetation clutter, and provides a reliable framework for acoustic monitoring of this species across structurally variable, and hence acoustically variable, environments in the area.     

Seasonal abundance, number of annual generations, and effect of an entomopathogenic fungus on Phlebotomus papatasi (Diptera: Psychodidae)

The monthly density of the sand fly, Phlebotomus Papatasi Scopoli (Diptera: Psychodidae), was monitored during 2009 at Burg El-Arab, a rural district located close to the Mediterranean coast of Egypt. The number of annual generations and the efficacy of microbial control by the entomopathogenic fungus, Metrahizium anisopliae (Metsch.) Sorok (Ma79), were determined in the laboratory under atmospheric conditions, simulating those of the animal shelters in the study area. We used two collecting techniques; CDC light traps and oiled paper traps, to quantify sand fly density inside houses and in the open field. Adult flies exhibited a seasonal range from April to December. The seasonal pattern was bimodal, with one peak in July and the second one in October. Calculations of the correlation coefficient (r) revealed a significant role of temperature and relative humidity in the monthly abundance of the sand flies in the study area. P. papatasi colony completed seven annual generations under semifield conditions, but the mean developmental time of each immature stage and the mean total duration of development from egg to adult for each generation varied according to the prevailing temperature. The longest generation time was observed in winter (the mean ± SD was 118 ± 11.70 d), and the shortest one occurred at the highest temperatures in summer (the mean ± SD was 25.21 ± 2.04 d). In microbial control studies, the entomopathogenic fungus, M. anisopliae, was used at 15 × 10(8) spores/g food as a standard dose against the second-instar larvae of P. papatasi at the different seasons during 2009. Mortality reached 100% in winter and decreased to 56.0% as the prevailing temperature increased during the summer season.     

The effect of temperature and salinity on growth rate and azaspiracid cell quotas in two strains of Azadinium poporum (Dinophyceae) from Puget Sound,Washington State

Azaspiracids (AZA) are novel lipophilic polyether marine biotoxins associated with azaspiracid shellfish poisoning (AZP). Azaspiracid-59 (AZA-59) is a new AZA that was recently detected in strains of Azadinium poporum from Puget Sound, Washington State. In order to understand how environmental factors affect AZA abundances in Puget Sound, a laboratory experiment was conducted with two local strains of A. poporum to estimate the growth rate and AZA-59 (both intra- and extracellular) cell quotas along temperature and salinity gradients. Both strains of A. poporum grew across a wide range of temperatures (6.7 °C to 25.0 °C), and salinities (15 to 35). Growth rates increased with increasing temperature up to 20.0 °C, with a range from 0.10 d⁻¹ to 0.42 d⁻¹. Both strains of A. poporum showed variable growth rates from 0.26 d⁻¹ to 0.38 d⁻¹ at salinities from 15 to 35. The percentage of intracellular AZA-59 in both strains was generally higher in exponential than in stationary phase along temperature and salinity gradients, indicating higher retention of toxin in actively growing cells. Cellular toxin quotas varied by strain in both the temperature and salinity treatments but were highest at the lowest growth rates, especially for the faster growing strain, NWFSC1011.Consistent with laboratory experiments, field investigations in Sequim Bay, WA, during 2016–2018 showed that A. poporum was detected when salinity and temperature became favorable to higher growth rates in June and July. Although current field data of A. poporum in Puget Sound indicate a generally low abundance, the potential of local A. poporum to adapt to and grow in a wide range of temperature and salinity may open future windows for blooms. Although increased temperatures, anticipated for the Puget Sound region over the next decades, will enhance the growth of A. poporum, these higher temperatures will not necessarily support higher toxin cell quotas. Additional sampling and assessment of the total toxicity of AZA-59 will provide the basis for a more accurate estimation of risk for azaspiracid poisoning in Puget Sound shellfish.     

Influence of physical and chemical factors on the larval abundance of Neurothemis tullia (Drury) (Odonata:Libellulidae) in a rain fed rice field

The influence of physical and chemical factors such as pH, temperature, conductivity, dissolved oxygen, nitrate, phosphate and chlorophyll a on larval populations of Neurothemis tullia (Drury) (Odonata:Libellulidae) were studied in a rain-fed rice field by collecting larvae and water samples weekly over two seasons of rice planting. Water availability was the main factor determining the presence or absence of larvae in the rice field. The larvae were most abundant during extended periods of continuously plentiful water supply except during flooding. Rapid larval population build-ups were observed soon after chemical applications or spells of dry periods reflecting continual oviposition and hatching of eggs. Pesticides and fertilizer applications resulted in low population densities due to direct or indirect mortality. A stepwise multiple regression showed that within its range, none of the physical and chemical factors measured in this study affected the abundance of N. tullia. This revised version was published online in July 2006 with corrections to the Cover Date.     

Response of Pisum sativum (Fabales: Fabaceae) to Sitona lineatus (Coleoptera: Curculionidae) infestation: effect of adult weevil density on damage, larval population, and yield loss

Sitona lineatus L. (Coleoptera: Curculionidae) is an invasive pest in North America and its geographical range is currently expanding across the Canadian prairies. Adults and larvae of S. lineatus feed upon the foliage and root nodules, respectively, of field pea, Pisum sativum L. (Fabales: Fabaceae), and may contribute to economic losses when population densities are high. Integrated pest management (IPM) programs that incorporate economic thresholds should be used to manage S. lineatus populations in a sustainable manner. The impact of nitrogen fertilizer on field pea yield and the relationships between adult weevil density and above- and below-ground damage and yield were investigated in southern Alberta, Canada using exclusion cages on field pea plots. In each cage, 32 field pea plants were exposed to weevil densities ranging from zero to one adult weevil per plant. Nitrogen-fertilized plants yielded 16% more than unfertilized plants. Nitrogen-fertilized plants had fewer root nodules than unfertilized plants, but fertilizer had no effect on foliar feeding by S. lineatus. Adult density affected foliar feeding damage, with increases in above-ground damage associated with increases in S. lineatus density. Adult density did not affect root nodule damage, larval density, foliar biomass or seed weight. Overall, these results indicate that terminal leaf damage may be used to estimate adult weevil density but cannot be used to predict larval density or yield loss. Further research is required to better understand the impact of larval damage on yield and determine if economic thresholds can be developed using data from large-scale production systems.     

Road edge effect on the abundance of the lizard <Emphasis Type="Italic">Gallotia galloti</Emphasis> (Sauria: Lacertidae) in two Canary Islands forests

Transportation infrastructure is a main cause of environmental change in forest landscapes worldwide. In the Canary Islands, a dense road system fragment the native Canarian pine and laurel forests causing potential changes in population densities of endemic lacertid lizards (genus Gallotia). Our aim was to assess road edge effects on relative abundance patterns of the endemic Gallotia galloti in both forests. We also explored the species–habitat relationships in this road-fragmentation context. We found that lizard relative density in relation to road edges differed between forests. Lizards were more abundant along edges and leeward interior, but virtually absent from the interior of the windward laurel forest. In the pine forest, lizards were present at three distances from edge, with a net decrease in abundance from edge to interior. These patterns may be explained partly by differences in vegetation structure regarding road proximity in each forest that potentially affect the helio- and thigmothermic character of G. galloti, and thus its habitat use. A general suggestion of this study is that road margins create corridors that may be used by native lizards for dispersal through inhospitable forest matrix. The high road density in Tenerife may have negative implications for the conservation of the genetic variability of G. galloti. At the island scale, increased communication between lizard populations through road corridors might increase homogenization of the gene pool. Ecological processes in which this lizard plays important roles may also experience changes along road edges.     

Plants,mites and mutualism: leaf domatia and the abundance and reproduction of mites on Viburnum tinus (Caprifoliaceae)

Associations between mites and leaf domatia have been widely reported, but little is known about their consequences for either plants or mites. By excising domatia from leaves of the laureltinus, Viburnum tinus L. (Caprifoliaceae), in the garden and laboratory, we showed that domatia alter the abundance, distribution, and reproduction of potential plant mutualists. Over 4 months, leaves with domatia on six garden shrubs had 2–36 times more predatory and microbivorous mites, and more mite eggs than leaves without domatia. However, this effect varied among plants and was weaker on one shrub with few mites on its leaves. Domatia also influenced the distribution of mites on leaves. A significantly higher fraction of mites, representing all life stages, was found in vein axils of leaves with domatia than in vein axils on leaves without domatia. Single-leaf experiments in the laboratory showed that domatia enhanced reproduction by the predatory mite, Metaseiulus occidentalis, especially at low relative humidity (30–38%). When domatia were removed, oviposition was reduced significantly only at low relative humidity, suggesting that domatia provide mites with refuge from environmental extremes on the leaf surface. Moreover, the use of domatia by predatory mites may reduce the impact of some plant enemies. In two experiments where prey consumption was measured, M. occidentalis ate significantly higher percentages of the eggs of the two-spotted spider mite (Tetranychus urticae). Our results are consistent with the viewpoint that mite-domatia associations are mutualistic. By directly aiding and abetting the third trophic level, plants with leaf domatia may increase the efficiency of some predaceous and microbivorous mites in consuming plant enemies.     

Distribution and abundance of the herringbone leaf-miner,Ophiomyia camarae (Diptera: Agromyzidae) on Lantana camara (Verbenaceae) in selected areas of Swaziland

The distribution and abundance of Ophiomyia camarae was determined in three ecological regions, i.e., highveld, middleveld, and lowveld of Swaziland. Within each region, sites were selected based on Lantana camara L. density, with 10 plants randomly chosen per sampling site. Ten leaves from each shrub were collected and assessed for any damage caused by the herringbone leaf-miner. Relative abundance, based on the number of shrubs damaged by the herringbone leaf-miner, was scored per site. Three lantana varieties were observed during the sampling period. There were significant differences in mean leaf damage due to leaf-miner activity between varieties (P=0.0162), with 46±4.89% leaves of the pale pink variety damaged compared to 23±5.56 and 21±3.53% leaves of the orange and pink varieties, respectively. While there were no restrictions in terms of distribution, the highest levels of O. camarae populations were observed in the middleveld (P=0.0012), suggesting that this region had the most suitable environmental conditions for this natural enemy. Overall, the abundance was significantly different between regions (P=0.006) and months (P=0.000), with April scoring the highest population levels. Based on our observations, the variation in environmental conditions has an influence on the activity of O. camarae, with the middleveld having the most suitable conditions     

The effect of pod growth stages in cowpea on aphid reproduction and damage by the cowpea aphid, Aphis craccivora (Homoptera: Aphididae)

Cowpea, Vigna unguiculata was infested at the young, mid-fill and mature pod growth stages with, respectively, one, two and three pre-reproductive adult apterae of Aphis craccivora per pod in a screen house. A. craccivora caused pod shrivelling at the young and mid-fill pod stages, on which the aphid was more fecund. All levels of infestation caused significant reduction in seed yield irrespective of age of pod.     

Effects of climate change and crop planting structure on the abundance of cotton bollworm,Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

The interactions between plants and insects play an important role in ecosystems. Climate change and cropping patterns can affect herbivorous pest insect dynamics. Understanding the reasons for population fluctuations can help improve integrated pest management strategies. Here, a 25‐year dataset on climate, cropping planting structure, and the population dynamics of cotton bollworms (Helicoverpa armigera) from Bachu County, south Xinjiang, China, was analyzed to assess the effects of changes in climate and crop planting structure on the population dynamics of H. armigera. The three generations of H. armigera showed increasing trends in population size with climate warming, especially in the third generation. The relative abundances of the first and second generations decreased, but that of the third generation increased. Rising temperature and precipitation produced different impacts on the development of different generations. The population numbers of H. armigera increased with the increase in the non‐Bacillus thuringiensis (Bt) cotton‐planted area. Asynchrony of abrupt changes existed among climate change, crop flowering dates, and the phenology of H. armigera moths. The asynchronous responses in crop flowering dates and phenology of H. armigera to climate warming would expand in the future. The primary factors affecting the first, second, and third generations of moths were T_mean in June, the last appearance date of the second generation of moths, and the duration of the third generation of moths, respectively. To reduce the harm to crops caused by H. armigera, Bt cotton should be widely planted.     

Effect of zooplankton type and abundance on prey consumption by the fairy shrimp, Streptocephalus proboscideus (Anostraca: Crustacea)

Laboratory cultured Streptocephalus proboscideus (three sizes (mm), viz. 8.44 ± 0.95 (virgin), 14.18 ± 1.49 (adult I) and 19.24 ± 1.52 (adult II)) were offered (separately for males and females) field collected zooplankton (12 prey types) at three levels of abundance (1.0 ml⁻¹, 2.0 ml⁻¹ and 4.1 ind. ml⁻¹ in 30-minute feeding experiments. Gut contents, analyzed for abundance and diversity of prey type, showed that predator size, sex and their interaction had strong effects on prey consumption. Regardless of their size, and of prey density, S. proboscideus females consumed 25–90% more prey than males. Their filtration rates (adult II) were higher (125 ml ind.⁻¹ h.⁻¹) than those of males (30 ml ind.⁻¹ h.⁻¹) too. Rotifers had the highest numerical percentage in the gut, regardless of predator size or sex. Cladocerans were only consumed by adults I and II. Adult II females consumed 28.5–43.3 μg zooplankton dry weight ind.⁻¹ h.⁻¹. Size distribution of B. longirostris in the field and in the gut were closely similar. This study confirms S. proboscideus as a non-selective filter feeder. Since it did not eat jumping rotifers, copepod nauplii and copepodites, it may contribute to structuring its prey communities, because good escapers will be enriched in the medium, while poor escapers will be depleted.     

The effect of rabbit (Oryctolagus cuniculus) grazing damage on the growth, botanical composition and yield of a ryegrass re-seed

A perennial ryegrass sward was established in the autumn of 1989 in an enclosed 0.3 ha site and was exposed to captive wild rabbit (Oryctolagus cuniculus) grazing. Rabbit numbers were varied from 16 rabbits ha^-1 in winter to 55 rabbits ha^-1 corresponding to natural fluctuations in the field. The original sward was grown for three seasons (1989/1990 to 1990/1991) and a range of grazing regimes imposed. In 1989/1990 four grazing regimes were arranged in a replicated split block design in the experimental area. These were ungrazed, winter grazed, spring grazed and totally grazed. In the second year of the experiment all plots were exposed to grazing with the exception of the originally protected plots. This was to examine the effects of longer-term grazing damage on a ryegrass sward. In the final year half of all treatments were protected to study recovery of a sward which had been damaged previously. The remainder of the plots were exposed to grazing. Three cuts were harvested in each year and the productivity assessed in terms of yield and botanical composition. There was a significant reduction in ryegrass proportion in grazed swards following the first winter of grazing, while clover, other grasses and weeds were enhanced. The promotion of clover content in grazed swards was a feature throughout the 3 yr of the study. In the second year, protection of grazed swards led to a restoration of yields, although the botanical composition remained altered. The exposure of previously ungrazed plots in the final year of the experiment showed that these swards were particularly attractive to rabbits and they suffered the greatest yield losses relative to the protected plots at the first cut in 1991. In this year dry weather conditions were experienced following the first cut and demonstrated that yield losses are exacerbated when rabbit grazing is compounded with adverse growing conditions. The results overall indicate that protection of ryegrass swards at the establishment phase is important, but that a degree of recovery is possible by providing protection at a later stage, although the ryegrass component is still impaired in swards which suffer early damage.