Long adult life, low reproduction and competition in two sub-Antarctic carabid beetles

ABSTRACT. 1. On the biologically impoverished sub-Antarctic Ile de la Possession, Iles Crozet, Amblystogenium pacificum Putzeys and A.minimum Luff (Carabidae), both opportunistic carnivores, coexist in fellfield habitat above 120 m altitude, where they hunt prey in inter-stone spaces.
2. Beetles show marked claw wear showing that many individuals survive to breed in their third or later year of adult life, and in some years, particularly in A.minimum , populations consisted largely of very old beetles. This coupled with evidence from ripe egg numbers, of rarity of tenerals and of larvae, shows that adult recruitment rates were usually very low.
3. In fellfield the coexisting species pair have non-overlapping size distributions with A.pacificum the larger. In moorland A.pacificum adults occur in isolation and are smaller and overlap the size ranges of both species in fellfield. These facts are interpreted as character displacement or release, reflecting present-day interspecific competition, probably for food. Supporting evidence was obtained in terms of apparent size-differential survival of beetles of different ages.     

Recolonisation and distribution of spiders and carabids in cereal fields after spring sowing

Generalist predators are important for pest suppression during pest establishment because they may occur in the crop before and during pest arrival. However, different crop management practices can have a negative effect on predator populations. If so, there is a need for recolonisation by the predators to the crop fields. An important pest in Sweden is the bird cherry‐oat aphid, Rhopalosiphum padi, which migrates to cereal fields in spring. In turn, many cereal fields are spring sown and thus are disturbed by harrowing and sowing a short time before aphid arrival. In this study, three different questions about the populations of spiders and carabids in spring cereal crops were asked. First, does sowing in spring have a negative effect on the predators present in the fields? Second, if sowing has a negative effect on predator populations, do they recolonise the fields before pest arrival? Third, how are the predators distributed in the fields? We found that most carabids and most lycosid spiders were not affected by sowing and were distributed uniformly in the fields after sowing. Most linyphiid spiders were negatively affected by sowing, but then they recolonised the fields and were uniformly distributed in the fields after recolonisation. Thus, many spiders and carabids are present in the fields after sowing in spring and have the opportunity to suppress aphids during their establishment phase, which in turn may prevent a possible outbreak.     

Isolation and characterization of microsatellite loci in the ground beetle Carabus problematicus (Coleoptera,Carabidae)

Six microsatellite loci were isolated from the ground beetle Carabus problematicus. The polymorphism ranged from two to 17 alleles and observed and expected heterozygosities ranged from 0.137 to 0.676 and 0.147 to 0.710, respectively.     

Conservation genetics of three flightless beetle species in southern California

Regional scale conservation decisions can be aided by information on the distribution of intraspecific diversity, especially the extent to which patterns are common to multiple species. We compare patterns of intraspecific mitochondrial cytochrome oxidase I (COI) variation among three flightless beetles (Coleoptera: Tenebrionidae: Nyctoporis carinata LeConte; Staphylinidae: Sepedophilus castaneus (Horn); Carabidae: Calathus ruficollis Dejean) in the southern part of the California Floristic Province biodiversity hotspot. All species exhibit moderate to high levels of total variation, ranging from 2% to 10% (maximum uncorrected distance). Most populations of all species exhibit unique haplotypes, but few populations’ haplotypes constitute exclusive clades. Many adjacent pairs of populations show indications of some, though limited, genetic connectedness, due either to gene flow or ancestral polymorphism. However, in most cases this diminishes sharply over greater distances. By both statistical and phylogenetic measures, Sierra Nevadan populations are highly distinct from those in the coast and transverse ranges. Among the latter, the eastern transverse ranges are generally most unique and isolated, with diversity in the western parts of these ranges showing fewer barriers. Otherwise, few measures agree on areas of highest conservation value, and overall patterns tend to be species-specific.     

Mechanisms in the Shift of a Riparian Ground Beetle (Carabidae) Between Reproduction and Hibernation Habitat

Factors affecting the light response of the riparian species Bembidion petrosum (Coleoptera: Carabidae) were studied with various experimental designs in laboratory and in field. B. petrosum, which lives in open gravely/stony sites, oriented towards directed light at higher temperatures (above 15.0°C). This positive phototaxis was replaced by an orientation towards a dark silhouette (screen) at low temperatures. The orientation towards silhouettes is mainly a simple type of form vision, although a fraction of the individuals seems to exhibit a negative phototaxis. In experiments with a dark zone and a zone with directed light, individuals of B. petrosum mainly selected the dark zone. However, if two stones were placed in the light part of the arena, individuals tended to hide under them. This applied independent of light intensity and whether a tuft of grass was present or absent in the dark part of the arena. The experiments indicate that the shift of the species between the reproduction (spring/summer) and hibernation (autumn/winter) habitat involves a change from an orientation towards silhouettes at low temperatures in autumn to an orientation towards directed light at higher temperatures in spring. This is combined with a specialized low thigmokinesis (preference of heavy and rough objects) and lower moisture requirements of the species in autumn/winter than in spring/summer.     

Molecular genetic evidence for the post-Pleistocene divergence of populations of the arctic-alpine ground beetle Amara alpina (Paykull) (Coleoptera: Carabidae)

Aim This study examines the hypothesis that the biogeographic history of a species is reflected in the distribution of molecular genetic diversity and the phylogenies of extant populations. Location Populations of arctic-alpine ground beetle Amara alpina were analysed from Beringia (Alaska and northernmost British Columbia), the Hudson Bay region, the northern Appalachian Mountains, and the central Rocky Mountains of North America. Methods Mitochondrial restriction site variation of specimens from twenty-two populations were assayed by using radioactively labelled mtDNA to probe Southern membranes containing restriction enzyme digested total DNA. Restriction sites were mapped and genetic distances were calculated by pairwise comparison of presence and absence of restriction sites. Genetic distances were used in a molecular analysis of variance and to construct a minimal spanning tree. Parsimony methods were used to investigate the phylogenetic relationships between the haplotypes. These results were compared to an existing model for postglacial dispersal based on fossil and modern occurrences of arctic-alpine beetles. Results Among the twenty-two populations, fifteen haplotypes were detected. Genetic variation within each of the four regions corresponded to that expected from the palaeontologically based model. Beringian populations were the most genetically diverse. In contrast, no restriction site variation was observed in populations from the Hudson Bay region. Intermediate amounts of variation were observed in alpine populations of the Rocky and Appalachian Mountains. Maximum parsimony and cluster analysis provide evidence that at least two ancestral haplotypes existed in the Southern refugium from which the Rocky and the Appalachian Mountains populations were founded. Main conclusions The genetic results are generally consistent with the palaeontologically based model. The diversity of Beringian populations is consistent with this region having been continuously inhabited by Amara alpina throughout the Pleistocene. The Hudson Bay region was not deglaciated until about 6000 years, and its populations have no restriction site variation. The molecular genetic data support the interpretation that the Hudson Bay region was colonized from Beringia based on the occurrence of the same haplotype in both regions.     

Fecundity and juvenile survival of shape Bembidion lampros and Tachyporus hypnorum

Fecundity and development from first instar larvae to adult beetles were studied for Bembidion lampros Herbst (Coleoptera; Carabidae) and Tachyporus hypnorum F. (Coleoptera; Staphylinidae). Both species reproduce in arable fields, where they are known to contribute to the natural control of cereal aphids. They are univoltine and have similar life cycles and development times. T. hypnorum females laid approximately 3 times more eggs than B. lampros females. Relative lifetime fecundity of B. lampros was very low with an average of 10 eggs per female. Based on the time where half of the populations had dispersed from the overwintering sites into an arable field B. lampros started egg-lay 100°D (°C>9) and T. hypnorum 200°D (°C>3) after dispersal. Mortality in the juvenile stages was found to be an important factor in the population dynamics of both B. lampros and T. hypnorum. The survival from first instar larvae to adults was on average 34% for B. lampros independent of soil type, 21% for T. hypnorum developed in sandy soil and 49% when developed in clayey soil under semi-field conditions. Enlargement of B. lampros and T. hypnorum populations to increase the natural control of aphids during their establishment in cereal fields may be possible if the conditions for juvenile development are improved.     

Notes onLaboulbenia stenolophi andLaboulbenia anoplogenii (Ascomycetes, Laboulbeniales)

Laboulbenia stenolophi is reported for the first time from Japan.Stenolophus iridicolor andS. propinquus are added as new hosts. The crowded antheridia and the protruding (bulging) cell IV are characteristic of this fungus, although thalli with an almost normal cell IV sometimes occur.Laboulbenia anoplogenii onAnoplogenius is easily distinguished from what has been calledL. anoplogenii onStenolophus, Astigis, Abacetus andChlaeminus by the following characters: 1) no crowded antheridia can be observed throughout thallus development, but many sterile long branches can be observed instead; 2) cell IV starts to undergo cell division early in thallus development; 3) cell V extends downward to the level of cell VII, rather than extending only as far as the perithecial basal cells; and 4) cell VI is usually longer and extends farther distally than cell III.Anoplogenius is the host genus ofL. anoplogenii and the records from other hosts represent misapplied names.     

Adult polyphagous coleopterans overwintering in cereal boundaries: winter mortality and susceptibility to the entomopathogenic fungus Beauveria bassiana

Autumn-collected Bembidion lampros and Agonum dorsale were kept outdoors under semi field conditions to determine winter mortality. On three occasions (autumn, mid-winter and late winter) sub-samples of the population were incubated in the laboratory at room temperature and mortality was recorded. Generally the mortality was low in autumn and mid-winter, not exceeding 5%. A more pronounced post-winter mortality of up to 30% was observed at the end of hibernation. Only a negligible number were infected by the entomopathogenic fungi Beauveria bassiana and Paecilomyces farinosus. Infection experiments with B. bassiana isolates from Sitona lineatus, Tachyporus hypnorum and three species of ground beetles showed a similarly low susceptibility of B. lampros and A. dorsale to B. bassiana and, although Tachyporus spp. showed a distinct mycophagy and a significantly higher mortality, this could not be related to mycosis.