Incidence of bark- and wood-boring insects in firewood: a survey at Michigan's Mackinac Bridge

Firewood is a major pathway for the inadvertent movement of bark- and wood-infesting insects. After discovery of Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) in southeastern Michigan in 2002, quarantines were enacted including prohibition of transporting firewood across the Mackinac Bridge between Michigan's Lower and Upper peninsulas. Drivers are required to surrender firewood before crossing the bridge. We surveyed recently surrendered firewood in April, July, and September 2008 and categorized it by genus, cross-sectional shape (whole, half, or quarter), approximate age (years since it was a live tree), presence of bark, and evidence of bark- and wood-boring insects. The 1045 pieces of firewood examined represented 21 tree genera: primarily Acer (30%), Quercus (18%), Fraxinus (15%), Ulmus (12%), Betula (5%), and Prunus (5%). Live borers (Bostrichoidea, Brentidae, Buprestidae, Cerambycidae, Cossidae, Curculionidae [Scolytinae and non-Scolytinae], and Siricidae) were found in 23% of the pieces and another 41% had evidence of previous borer infestation. Of the 152 Fraxinus firewood pieces, 13% had evidence of past A. planipennis infestation, but we found no live A. planipennis. We discuss national "don't move firewood" campaigns and U.S. imports of fuelwood. During 1996-2009, the United States imported fuelwood valued at > dollars U.S. 98 million from 34 countries.     

Breaking taboos in the tropics: incest promotes colonization by wood-boring beetles

• 1 Inbreeding and parthenogenesis are especially frequent in colonizing species of plants and animals, and inbreeding in wood‐boring species in the weevil families Scolytinae and Platypodidae is especially common on small islands. In order to study the relationship between colonization success, island attributes and mating system in these beetles, we analysed the relative proportions of inbreeders and outbreeders for 45 Pacific and Old World tropical islands plus two adjacent mainland sites, and scored islands for size, distance from nearest source population, and maximum altitude.
• 2 The numbers of wood‐borer species decreased with decreasing island size, as expected; the degree of isolation and maximum island altitude had negligible effects on total species numbers.
• 3 Numbers of outbreeding species decreased more rapidly with island size than did those of inbreeders. Comparing species with similar ecology (e.g. ambrosia beetles) showed that this difference was best explained by differential success in colonization, rather than by differences in resource utilization or sampling biases. This conclusion was further supported by analyses of data from small islands, which suggested that outbreeding species have a higher degree of endemism and that inbreeding species are generally more widespread.
• 4 Recently established small populations necessarily go through a period of severe inbreeding, which should affect inbreeding species much less than outbreeding ones. In addition, non‐genetic ecological and behavioural (‘Allee’) effects are also expected to reduce the success of outbreeding colonists much more than that of inbreeders: compared with inbreeders, outbreeders are expected to have slower growth rates, have greater difficulties with mate‐location and be vulnerable to random extinction over a longer period.

     

Assessing the role of bark- and wood-boring insects in the decline of Scots pine (Pinus sylvestris) in the Swiss Rhone valley

Abstract.  1. In several dry inner Alpine valleys higher mortality levels of pine have been observed in recent years. This paper evaluates the role of xylophagous insects in the current pine decline and the influence of climate change on the infestation dynamics.
2. More than 200 trees of different levels of crown transparency (needle loss) were felled between 2001 and 2005 and sections of them incubated in insect emergence traps. Colonisation densities were related to the transparency level of each host tree at the time of attack.
3. Trees with more than 80% needle loss were colonised most frequently, but the breeding density was highest in trees with 65–80% needle loss.
4. The scolytine Ips acuminatus and the buprestid Phaenops cyanea colonised trees with 30–90% needle loss in high densities. The bark beetle Tomicus minor was less aggressive, preferring trees with 60–85% needle loss. The hymenopteran Sirex noctilio and the cerambycid Acanthocinus aedilis were restricted to greatly weakened trees with 50–85% needle loss. Most species colonised trees that had experienced a decline in vigour, that is an increase in crown transparency shortly before attack.
5. The infestation dynamics of P. cyanea covaried with the drought index as well as with temperature.
6. Increased temperatures not only trigger a drought stress rendering the host trees susceptible to insect attack, but also accelerate insect development. As more frequent drought periods are likely as a result of climate change, even trees only slightly or temporarily weakened will be more subject to attack by aggressive species such as I. acuminatus and P. cyanea .     

Effect of deadwood management on saproxylic beetle richness in the floodplain forests of northern Italy: some measures for deadwood sustainable use

Saproxylic beetles may act as bio-indicators of high-quality mature woodlands, and their conservation is strongly linked to the quality and quantity of deadwood in a biotope. We tested the effect of deadwood accumulation and habitat variables on saproxylic species richness by investigating six sampling sites under different deadwood management practices that belong to both alluvial and riparian mixed forests of the Po plain, Italy. We sampled 43 obligate saproxylic species. The main factor predicting saproxylic species richness was the amount of deadwood measured by both log diameter and volume. We found a threshold of 0.22 m diameter (confidence interval CI 0.18–0.37 m) and 32.04 m³/ha volume (CI 16.09–64.09 m³/ha) below which saproxylic beetle richness would be significantly reduced and a threshold of 35 m³/ha dead wood volume (CI 33–40 m³/ha) over which species richness increases by <5 %. The other deadwood and environmental components influenced saproxylic beetle richness to a lesser extent; some of them, however, should still be considered for proper management. Forest structure variables describing forest density such as large trees and basal areas have a negative effect on species richness. According to the results of our study, stumps and advanced decaying class are positively correlated, while small logs are negatively correlated to species richness. Thus, in extensively managed forests, the regular cutting of trees should be implemented to create artificial stumps, in order to assure a continuity of deadwood and, in the meantime, increase the number and width of openings in the forest. Moreover, prolonging rotation times can assure the presence of deadwood at intermediate/later stages of decay.     

Impacts of silvicultural thinning treatments on beetle trap captures and tree attacks during low bark beetle populations in ponderosa pine forests of northern Arizona

Our research used a combination of passive traps, funnel traps with lures, baited trees, and surveys of long-term thinning plots to assess the impacts of different levels of stand basal area (BA) on bark beetle tree attack and on trap captures of Ips spp., Dendroctonus spp., and their predators. The study occurred at two sites in ponderosa pine, Pinus ponderosa Dougl. ex Laws., forests, from 2004 to 2007 during low bark beetle populations. Residual stand BA ranged from 9.0 to 37.0 m2/ha. More predators and bark beetles were collected in passive traps in stands of lower BA than in stands of higher BA; however, significance varied by species and site, and total number of beetles collected was low. Height of the clear panel passive traps affected trap catches for some species at some sites and years. When pheromone lures were used with funnel traps [Ips pini (Say) lure: lanierone, +03/-97 ipsdienol], we found no significant difference in trap catches among basal area treatments for bark beetles and their predators. Similarly, when trees were baited (Dendroctonus brevicomis LeConte lure: myrcene, exo-brevicomin and frontalin), we found no significant difference for days to first bark beetle attack. Surveys of long-term thinning treatments found evidence of bark beetle attacks only in unthinned plots (approximately 37 m2/ha basal area). We discuss our results in terms of management implications for bark beetle trapping and control.     

Abundance,not diversity,of host beetle communities determines abundance and diversity of parasitoids in deadwood

Most parasites and parasitoids are adapted to overcome defense mechanisms of their specific hosts and hence colonize a narrow range of host species. Accordingly, an increase in host functional or phylogenetic dissimilarity is expected to increase the species diversity of parasitoids. However, the local diversity of parasitoids may be driven by the accessibility and detectability of hosts, both increasing with increasing host abundance. Yet, the relative importance of these two mechanisms remains unclear. We parallelly reared communities of saproxylic beetle as potential hosts and associated parasitoid Hymenoptera from experimentally felled trees. The dissimilarity of beetle communities was inferred from distances in seven functional traits and from their evolutionary ancestry. We tested the effect of host abundance, species richness, functional, and phylogenetic dissimilarities on the abundance, species richness, and Shannon diversity of parasitoids. Our results showed an increase of abundance, species richness, and Shannon diversity of parasitoids with increasing beetle abundance. Additionally, abundance of parasitoids increased with increasing species richness of beetles. However, functional and phylogenetic dissimilarity showed no effect on the diversity of parasitoids. Our results suggest that the local diversity of parasitoids, of ephemeral and hidden resources like saproxylic beetles, is highest when resources are abundant and thereby detectable and accessible. Hence, in some cases, resources do not need to be diverse to promote parasitoid diversity.     

Influence of the larval environment on performance and adult body size of the wood-boring beetle Phoracantha semipunctata

Large body size confers a reproductive advantage to adults of the wood‐boring beetle Phoracantha semipunctata (F.) (Cerambycidae: Cerambycinae: Phoracanthini). Larvae of this species feed subcortically in stressed and dying eucalypt trees and logs. We evaluated the influence of the larval environment on larval performance and adult body size by manipulating the post‐felling age of host logs (from freshly cut to 2‐weeks‐old) and the density of colonizing neonates (low density with minimal competition for resources vs. high density with intense competition). Adult beetles emerged in greater numbers from logs that had been subjected to the aging treatment which reduced bark moisture content and favored colonization by neonates. Survival was greatest in larger logs having lower densities of neonates, but was greatly diminished in all treatments by mortality during pupation. Development time varied from 2 months to more than a year and was shortest in smaller logs having high densities of larvae. The size of adult beetles emerging from a log was not influenced by larval density, but was positively correlated with the age of logs when the neonates colonized, and log size. These findings suggest that the optimal developmental conditions for P. semipunctata larvae, in terms of larval performance and adult body size, are available in large, aged host logs having low densities of larvae. Manipulation of the larval environment in this study resulted in a considerable variation in adult body size, but large individuals were relatively more common in the wild population that was the source of neonates for the experiment. Potential body size may have been constrained by our use of only one host species and a narrow range of log dimensions.     

Helicobacter pylori AddAB helicase-nuclease and RecA promote recombination-related DNA repair and survival during stomach colonization

Helicobacter pylori colonization of the human stomach is characterized by profound disease-causing inflammation. Bacterial proteins that detoxify reactive oxygen species or recognize damaged DNA adducts promote infection, suggesting that H. pylori requires DNA damage repair for successful in vivo colonization. The molecular mechanisms of repair remain unknown. We identified homologues of the AddAB class of helicase-nuclease enzymes, related to the Escherichia coli RecBCD enzyme, which, with RecA, is required for repair of DNA breaks and homologous recombination. H. pylori mutants lacking addA or addB genes lack detectable ATP-dependent nuclease activity, and the cloned H. pylori addAB genes restore both nuclease and helicase activities to an E. coli recBCD deletion mutant. H. pylori addAB and recA mutants have a reduced capacity for stomach colonization. These mutants are sensitive to DNA damaging agents and have reduced frequencies of apparent gene conversion between homologous genes encoding outer membrane proteins. Our results reveal requirements for double-strand break repair and recombination during both acute and chronic phases of H. pylori stomach infection.     

Assessing the origin of Neotropical mountain dung beetle assemblages (Scarabaeidae: Scarabaeinae): the comparative influence of vertical and horizontal colonization

Aims The fauna of mountains and their surrounding regions are likely to be influenced principally by two biological processes: horizontal colonization along similar altitudinal levels by elements originating from lineages inhabiting higher latitudes; and vertical colonization by lineages from the same latitude, but at lower altitudes. We examine whether the expected patterns derived from the latter process can be observed in mountain dung beetle assemblages. Specifically, we study the variation in species composition and richness with altitude in five regions spanning elevation gradients, analysing whether the altitudinal rates of change in the number of species and genera differ, and whether beta‐diversity scores for adjacent sites in each altitudinal gradient are different for species and genera. Location Eastern Cordillera of the Colombian Andes. Methods Field work was carried out in 1997–99 at 27 sites in five regions with elevation gradients, with 10–32 pitfall traps placed in each site. For each altitudinal level the numbers of species and genera were analysed with respect to altitude, and the slope of the linear regression between these variables was calculated. The slope of the curve of the altitude against the cumulative number of species and genera was also calculated for each altitudinal gradient to describe the compositional change between adjacent sites (beta diversity). Species and generic slopes were compared using analysis of covariance. The turnover of species along each altitudinal gradient was measured using presence/absence data and Cody's beta‐diversity index between adjacent pairs of sites. A cluster analysis was used to detect faunistically homogeneous groups of localities. Results Species richness always decreased with altitude, although the slopes did not differ significantly from zero. The number of genera also decreased with increasing altitude, but generally at a significantly slower rate than for species. Variation in the species beta‐diversity scores between altitudinal levels did not follow a homogeneous pattern in the different regions. Two main altitudinal groups of sites with a boundary c. 1500–1750 m a.s.l. can be detected with respect to faunistic similarity. Low‐ and mid‐altitude sites are inhabited by all of the genera (19) and 80% of all species collected. Eight genera and 61 species (c. 60% of the total) are unable to inhabit high‐altitude sites, and only 20 species appear to be exclusive to these high‐altitude environments (> 2000 m a.s.l.). Main conclusions The dominant processes explaining dung beetle composition in the high north‐eastern Andean mountains are probably those of vertical colonization. The limited role of horizontal colonization processes, or colonization from northern or southern lineages, could be a consequence of the isolation and recent geological origin of these mountains.     

Glacial survival and local adaptation in an alpine leaf beetle

The challenge in defining conservation units so that they represent evolutionary entities has been to combine both genetic properties and ecological significance. Here we make use of the complexity of the European Alps, with their genetic landscape shaped by geographical barriers and postglacial colonization, to examine the correlation between ecological and genetic divergence. Montane species, because of the fragmentation of their present habitat, constitute extreme cases in which to test if genetically distinct subgroups based on neutral markers are also ecologically differentiated and show local adaptation. In the leaf beetle Oreina elongata, populations show variation in host plant use and a patchy distribution throughout the Alps and Apennines. We demonstrate that despite very strong genetic isolation (F(ST) = 0.381), variation in host plant use has led to differences in larval life-history traits between populations only as a secondary effect of host defence chemistry, and not through physiological adaptation to plant nutritional value. We also establish that populations that are more ecologically different in terms of larval performance are also more genetically divergent. In addition, morphological variation used to define subspecies appears to be mirrored in the population genetics of this species, resulting in almost perfect clustering based on microsatellite data. Finally, we argue from their strong genetic structure and congruent distribution that the subspecies of O. elongata were divided among the same glacial refugia within the Alps that have been proposed for alpine plants.     

First record of the family Bothrideridae (Coleoptera) in Korea represented by the wood-boring beetle ectoparasite,Dastarcus helophoroides

The ectoparasitic beetle, Dastarcus helophoroides (Fairmaire), was observed for the first time in Korea as a result of a study of the natural enemies of Monochamus alternatus Hope and M. saltuarius Gebler, the vector of the pine wood nematode (Bursaphelenchus xylophilus (Steiner & Buhner)). Diagnostic illustrations are provided and the biology and host range of D. helophoroides (Fairmaire) are reviewed.     

Induced terpene accumulation in Norway spruce inhibits bark beetle colonization in a dose-dependent manner

Background

Tree-killing bark beetles (Coleoptera, Scolytinae) are among the most economically and ecologically important forest pests in the northern hemisphere. Induction of terpenoid-based oleoresin has long been considered important in conifer defense against bark beetles, but it has been difficult to demonstrate a direct correlation between terpene levels and resistance to bark beetle colonization.

Methods

To test for inhibitory effects of induced terpenes on colonization by the spruce bark beetle Ips typographus (L.) we inoculated 20 mature Norway spruce Picea abies (L.) Karsten trees with a virulent fungus associated with the beetle, Ceratocystis polonica (Siem.) C. Moreau, and investigated induced terpene levels and beetle colonization in the bark.

Results

Fungal inoculation induced very strong and highly variable terpene accumulation 35 days after inoculation. Trees with high induced terpene levels (n = 7) had only 4.9% as many beetle attacks (5.1 vs. 103.5 attacks m⁻²) and 2.6% as much gallery length (0.029 m m⁻² vs. 1.11 m m⁻²) as trees with low terpene levels (n = 6). There was a highly significant rank correlation between terpene levels at day 35 and beetle colonization in individual trees. The relationship between induced terpene levels and beetle colonization was not linear but thresholded: above a low threshold concentration of ∼100 mg terpene g⁻¹ dry phloem trees suffered only moderate beetle colonization, and above a high threshold of ∼200 mg terpene g⁻¹ dry phloem trees were virtually unattacked.

Conclusion/Significance

This is the first study demonstrating a dose-dependent relationship between induced terpenes and tree resistance to bark beetle colonization under field conditions, indicating that terpene induction may be instrumental in tree resistance. This knowledge could be useful for developing management strategies that decrease the impact of tree-killing bark beetles.     

Enhancing carrot somatic embryos survival during slow dehydration, by encapsulation and control of dehydration

In order to obtain dry artificial seeds, carrot somatic embryos were encapsulated and dehydrated. Encapsulation in some hydrogels delayed the dehydration and preserved the water content of carrot somatic embryos. In particular, a matrix made of alginate with gellan gum was found to be the most efficient in maintaining a high water activity (a_w) around somatic embryos. By delaying dehydration, and also rehydration, encapsulation seemed to protect somatic embryos against desiccation and imbibition damages, giving better germination and emergence of cotyledons. Matrices made of alginate mixed with kaolin or gellan gum were particularly adapted to protect the embryos during the dehydration. Apart from the matrix composition, the control of dehydration speed enhanced the survival and regeneration of encapsulated-dehydrated somatic embryos. Using a slow dehydration protocol (95-15% RH—relative humidity into the chamber—in 11.5 days), it was possible to exert different dehydration speeds. Slowing the dehydration between 70 and 45% RH stabilized the water activity (a_w) of the encapsulation matrix, and enhanced the survival and regeneration frequencies of encapsulated-dehydrated embryos. In the absence of any maturing pretreatment, alginate-gellan gum encapsulated carrot somatic embryos, dehydrated to 15% RH, and rehydrated in moistured air (90% RH), germinated up to 72.9%. Therefore, encapsulation in alginate-gellan gum, combined with a slow dehydration, leads to enhance the somatic embryos' desiccation tolerance.     

Sub-antarctic House mice: colonization, survival and selection

House mice have colonized and survived successfully on a number of Sub-Antarctic islands, where the mean annual temperature is only about 5°C, but where there is little seasonal fluctuation in climate. Surprisingly this allows almost continuous breeding. On at least two islands (Macquarie and Marion), there are significant changes in gene frequency in electro-phoretically detected enzymes between young (less than three months of age) and old animals from the same population. This indicates natural selection acting in opposite directions at different stages of the life cycle. However the genetical compositions of the Macquarie and Marion populations are more distinct from each other than either is from most British samples. This means that detailed studies of the Sub-Antarctic mouse populations are likely to reveal much about local adaptation, while comparison between the responses of different populations may lead to important generalisations about the possible reaction to evolutionary challenges of a species living close to its physiological limit.     

Flight initiation and survival in the bark beetle Ips typographus (Coleoptera: Scolytidae) during the spring dispersal

Temperatures in the forest litter of Norway spruce Picea abies were recorded throughout the day to obtain environmental parameters that could be used to design realistic flight-activity experiments in the laboratory. Flight activity and survival were monitored electronically in plastic chambers where the conditions were controlled by an environmental chamber. Flight attempts of the bark beetle Ips typographus were initially lower in chambers with forest duff but were prolonged compared with those of beetles in chambers with a metal screen substrate. Small bark slabs and spruce twigs in the duff were utilized as food and extended the period of flight and survival. A thermal gradient in duff from 25° at the surface down to 13.8°C at a depth of 4 cm also slightly increased the survival of beetles compared with a constant 25°. A daily ambient temperature cycle as well as the duff thermal gradient increased the survival from about 3 d to more than 8 d. The latter length in the laboratory agreed with survival rates of caged beetles in a clearcut forest area, while beetles caged in the forest survival for more than 14 d. Temperatures were monitored at the duff surface of the caged beetles and compared with the catches of beetles that were attracted to a pheromone trap and collected with an electronic fraction collector. Information on flight and survival during the dispersal period is necessary to the design of ecologically sound management programs for control of bark beetles.     

Parasitoid dispersal and colonization lag in disturbed habitats: biological control of cereal leaf beetle metapopulations

Natural enemies of insect pests of annual crops have been hypothesized either to lag, or alternatively not to lag, behind their prey in dispersing to and colonizing new habitat. We examined parasitoid dispersal and parasitism of the cereal leaf beetle (Oulema melanopus [L.]; Coleoptera: Chrysomelidae) by the host‐specific wasp Tetrastichus julis [Walker] (Hymenoptera: Eulophidae) in wheat fields of northern Utah to assess whether a colonization lag occurred. Equally high rates of parasitism of beetle larvae (including second instars early in the year) occurred in 2010 and 2011 in fields that were newly planted to wheat vs. in fields where wheat had been grown also the previous year. A caging experiment demonstrated that parasitism in these newly planted wheat fields did not arise from parasitoid adults that had matured within the fields; instead, upon emerging in other fields, parasitoid females dispersed a minimum of 100–250 m to parasitize beetle larvae early in the spring in the newly planted fields. A transect study in 2012 revealed that T. julis females dispersed rapidly at least 600 m into a newly planted wheat field to parasitize most of the early maturing beetle larvae, which occurred at very low density. Thus, the parasitoid has very strong ability to match its host in dispersal over long distances across a highly disturbed agricultural landscape, and colonization lag appears of little importance in affecting biological control associated with this host–parasitoid interaction.     

Host selection and colonization strategies with evidence for a female-produced oviposition attractant in a longhorn beetle

In longhorn beetles and many other internally feeding insects, oviposition choice by females is critical to the survival of their offspring because their larvae are incapable of moving between hosts. Here we report on the complex host selection and colonization strategies of a longhorn beetle, Glenea cantor (F.) (Coleoptera: Cerambycidae), which is an important pest of kapok trees [Bombax ceiba L.=Gossampinus malabaricus (DC.) Merr.] in southern Asia. It attacks weakened trees, eventually killing them. The typical oviposition behavioral sequence in the laboratory includes the following: oviposition site search and recognition using antennae and palpi, oviposition slit preparation with mandibles, turning body direction 180°, egg deposition with the ovipositor, and oviposition wound covering with a jelly-like material from the ovipositor. Bark moisture content significantly increases from the upper to lower sections in kapok trees. In accordance with this variation female adults select the upper section of trees first for oviposition. As infestation continues and the host becomes more weakened, ovipositing females move further down the tree for oviposition. Consequently, the larvae kill the hosts from the top down. We show that the jelly-like material or eggs or both have an olfactory role in attracting females to oviposit nearby. Our findings are important in terms of increasing our understanding of host selection and colonization mechanisms of internally feeding insects, particularly cerambycids, and the development of environmentally friendly pest management measures.     

Attraction of the bark beetle Tomicus piniperda and some other bark- and wood-living beetles to the host volatiles α-pinene and ethanol

The attraction of some bark- and ambrosia beetles as well as associated beetles to the host volatiles -pinene and ethanol was studied in field tests with flight barrier traps. Tomicus piniperda (L.) (Scolytidae), Thanasimus formicarius (L.) (Cleridae), and Rhizophagus ferrugineus (Payk.) (Rhizophagidae) were attracted by -pinene, while Hylurgops palliatus (Gyll.) and Trypodendron lineatum (Oliv.) (Scolytidae) were attracted by ethanol and Epuraea spp. (Nitidulidae) by both -pinene and ethanol. Combinations of -pinene and ethanol attracted high numbers of H. palliatus, T. lineatum, R. ferrugineus, Epuraea spp., and Glischrochilus spp. (Nitidulidae) and the catches increased with increasing release rates of ethanol. By contrast, lower numbers of T. piniperda were caught in traps baited with combinations of -pinene and ethanol than in traps baited with -pinene alone, and the catches of this species decreased with increasing release rates of ethanol. Traps baited with a combination of -pinene and ethanol or with -pinene alone caught similar numbers of T. formicarius. The results are discussed on the basis of species differences in preference for breeding substrate.

---

Zusammenfassung Die Anlockung mehrerer Borkenkäfer und assoziierter Käferarten zu den flüchtigen Wirtsstoffen -Pinen und Äthanol wurde in Feldversuchen mit Flugbarrierenfallen studiert. Tomicus piniperda (L.) (Scolytidae), Thanasimus formicarius (L.) (Cleridae) und Rhizophagus ferrugineus (Payk.) (Rhizophagidae) wurden durch -Pinen angelockt, die Borkenkäfer Hylurgops palliatus (Gyll.) und Trypodendron lineatum (Oliv.) durch Äthanol und die Epuraea-Arten (Nitidulidae) durch sowohl -Pinen als auch Äthanol.Kombinationen von -Pinen und Äthanol lockten viele Individen von H. palliatus, T. lineatum, R. ferrugineus, Epuraea spp. und Glischrochilus spp. (Nitidulidae) an, und die Fänge nahmen mit zunehmender Äthanol-Abgabe zu. Umgekehrt wurden weniger T. piniperda in Fallen mit Kombinationen von -Pinen und Äthanol gefangen als in Fallen mit -Pinen allein, und die Waldgärtner-Fänge nahmen mit zunehmender Äthanol-Abgabe ab. Die Fänge von T. formicarius in Fallen mit einer Kombination von -Pinen und Äthanol unterschieden sich nicht von denen in Fallen mit nur -Pinen.Die Ergebnisse werden auf der Grundlage der Unterschiede zwischen den Arten in der Wahl des Brut-substrats besprochen.

     

Tree leaf litter composition drives temporal variation in aquatic beetle colonization and assemblage structure in lentic systems

Tree leaf litter inputs to freshwater systems are a major resource and primary drivers of ecosystem processes and structure. Spatial variation in tree species distributions and forest composition control litter inputs across landscapes, but inputs to individual lentic habitat patches are determined by adjacent plant communities. In small, ephemeral, fishless ponds, resource quality and abundance can be the most important factor affecting habitat selection preferences of colonizing animals. We used a landscape of experimental mesocosms to assess how natural populations of aquatic beetles respond over time to variation in tree leaf litter composition (pine or hardwood). Patches with faster-decomposing hardwood leaf litter were initially colonized at higher rates than slower-decomposing pine pools by most species of Hydrophilidae, but this pattern reversed later in the experiment with higher colonization of pine pools by hydrophilids. Colonization did not differ between pine and hardwood for dytiscids and the small hydrophilid Paracymus, but there were distinct beetle assemblages between pine and hardwood patches both early and late in the experiment. Our data support the importance of patch quality and habitat selection as determinants of species abundances, richness, and community structure in freshwater aquatic systems, not only when new habitat patches are formed and initial conditions set, but as patches change due to interactions of processes such as decomposition with time.