Habitat choice of some field-inhabiting carabid beetles (Coleoptera: Carabidae) studied by recapture of marked individuals

ABSTRACT.

• 1 Habitat choice of some field-inhabiting carabid beetles was studied in the field, and included the adult-overwintering Bembidion lampros Herbst, Pterostichus cupreus L. and Agonum dorsale Pontoppidan, and the larval-overwintering Trechus secalis Paykull, Pterostichus melanarius Illiger, P.niger Schaller and Harpalus rufipes De Geer. These were compared to the forest-inhabiting and adult-overwintering species, Carabus nemoralis Müller.
• 2 Marked beetles were released in the centre of a circular enclosure which was placed on the edge between a cereal field and a wood. The direction of movement in this circle was compared with that in a control circle placed entirely in the cereal field.
• 3 In the field/wood circle, adult-overwinterers and the larval-overwin-terer H.rufipes choose to move into the cereal field. The majority of T.secalis. P.melanarius and C.nemoralis, however, moved into the wood, while P.niger exhibited no preference.
• 4 In the field circle, adult-overwinterers moved towards the more sun-exposed parts of the circle, whereas the movements of larval-overwin-terers were random.
• 5 Some species-specific characteristics considered important for habitat choice by these carabid beetles, and the relevance of these characteristics for their dispersal behaviour are discussed.

     

Position of the labrum in agnostid trilobites

Specimens of Peronopsis and Ptychagnostus from the House Range of western Utah provide new information on the location of the labrum (hypostoma) of agnostid trilobites. A labral position as that described here, beneath the second glabellar lobe, has two implications: (1) anomalous cephalic muscle scars described by previous workers may be interpreted as attachment areas for labral muscles; and (2) the mouth probably migrated posteriorly in agnostids. Posterior displacement of the mouth was probably one of several feeding modifications associated with a pelagic mode of life.     

Concanavalin A Improves the Polyethylene Glycol Method for Fusing Plant Protoplasts

An improved method for polyethylene glycol-induced fusion of protoplasts isolated from auxotrophic mutants of Nicotiana tabacum L. cv. Gatersleben was developed. By using Petri dishes coated with concanavalin A the attachment of protoplasts induced by polyethylene glycol was strengthened. As a consequence of the stronger attachment more fusion products remained after the dilution and washing procedure. It was also found that a shorter treatment combined with a more rapid dilution of the polyethylene glycol solution was superior to previous fusion methods used for plant protoplasts.     

Foraging activity and dietary spectrum of wood ants (Formica rufa group) and their role in nutrient fluxes in boreal forests

Abstract 1. We monitored three different‐sized wood ant (Formica aquilonia Yarrow) mounds over a 3‐year period in Finnish boreal forests dominated by Norway spruce (Picea abies Karst.), to assess the seasonal temperature dependency of ant activity. Additionally, we also monitored Norway spruce trees around the mounds for descending honeydew foragers. 2. The amount of collected honeydew and prey and its composition, as well as the carbon (C), nitrogen (N), and phosphorus (P) in honeydew and invertebrate prey was also investigated. 3. The number of warm days (average temperature above 20 °C) and the amount of precipitation differed among the years. Ant activity at the mounds (but not on the trees) was highly correlated with air temperature throughout the ant‐active season (May–September), but ant activity in spring and autumn was lower than in summer at similar temperatures. During all 3 years, honeydew played a major role in wood ant nutrition (78–92% of dry mass). Invertebrate prey was mainly Diptera (on average 26.2%), Coleoptera (12.5%), Aphidina (9.3%), and Arachnoida (8.5%). 4. The total amounts of C, N, and P input brought into the ant mounds in the form of food (both honeydew and prey) on the stand level were 12.6–39.0, 1.6–4.6 and 0.1–0.4 kg ha^?1 year^?1, respectively, which is equivalent to 2–6%, 12–33% and 27–58% of the fluxes in annual needle litterfall in typical boreal Norway spruce forests. Thus, wood ants can play a significant role in short term and local N and P cycling of boreal forest ecosystems.     

Predation on Moose Calves by European Brown Bears

Abstract: In North America, brown bears (Ursus arctos) can be a significant predator on moose (Alces alces) calves. Our study in Sweden is the first in which brown bears are the only predator on moose calves. Bears and moose occurred at densities of about 30/1,000 km² and 920/1,000 km², respectively, and bears killed about 26% of the calves. Ninety-two percent of the predation took place when calves were <1 month old. Bear predation was probably additive to other natural mortality, which was about 10% in areas both with and without bears. Females that lost their calves in spring produced more calves the following year (1.54 calves/F) than females that kept their calves (1.11 calves/F), which reduced the net loss of calves due to predation to about 22%.     

Maximizing information in systematic revisions: a combined molecular and morphological analysis of a cryptic green pitviper complex (Trimeresurus stejnegeri)

Although the integration of DNA information in taxonomy has been invaluable, logistical problems relating to sampling can seriously limit its applicability. Here we describe the analysis of a morphologically cryptic species complex, in which we maximize the information present by using both a DNA phylogeny and a multivariate morphometric approach. The green pitviper Trimeresurus stejnegeri s.l. is widespread in Asia, with a number of described subspecies (some of which are considered full species by some workers) and two new species that have recently been described from Thailand. The phylogeny indicates three clades, which can also be discerned in the principal component analyses of morphological variation. Combining molecular and morphological information permits evaluation of the taxonomic position of populations not represented in the phylogeny − in particular, the subspecies T. s. chenbihui and T. s. yunnanensis . We discuss nomenclatural issues raised by this analysis, although these cannot be fully resolved until the holotypes of these subspecies can be examined. Finally, we apply a molecular clock calibrated in New World pitvipers, and discuss some of the palaeoclimatic changes that might have impacted upon diversification in this group.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82 , 219–235.     

Linking above- and belowground responses to global change at community and ecosystem scales

Cryptic belowground organisms are difficult to observe and their responses to global changes are not well understood. Nevertheless, there is reason to believe that interactions among above- and belowground communities may mediate ecosystem responses to global change. We used grassland mesocosms to manipulate the abundance of one important group of soil organisms, arbuscular mycorrhizal (AM) fungi, and to study community and ecosystem responses to CO₂ and N enrichment. Responses of plants, AM fungi, phospholipid fatty acids and community-level physiological profiles were measured after two growing seasons. Ecosystem responses were examined by measuring net primary production (NPP), evapotranspiration, total soil organic matter (SOM), and extractable mineral N. Structural equation modeling was used to examine the causal relationships among treatments and response variables. We found that while CO₂ and N tended to directly impact ecosystem functions (evapotranspiration and NPP, respectively), AM fungi indirectly impacted ecosystem functions by influencing the community composition of plants and other root fungi, soil fungi and soil bacteria. We found that the mycotrophic status of the dominant plant species in the mesocosms determined whether the presence of AM fungi increased or decreased NPP. Mycotrophic grasses dominated the mesocosm communities during the first growing season, and the mycorrhizal treatments had the highest NPP. In contrast, nonmycotrophic forbs were dominant during the second growing season and the mycorrhizal treatments had the lowest NPP. The composition of the plant community strongly influenced soil N, and the community composition of soil organisms strongly influenced SOM accumulation in the mesocosms. These results show how linkages between above- and belowground communities can determine ecosystem responses to global change.