@article {13471, title = {From Attack to Emergence: Interactions between Southern Pine Beetle, Mites, Microbes, and Trees}, journal = {U S Forest Service General Technical Report SRS}, volume = {140}, year = {2011}, month = {2011}, pages = {141-152}, abstract = {Bark beetles are among the most ecologically and economically influential organisms in forest ecosystems worldwide. These important organisms are consistently associated in complex symbioses with fungi. Despite this, little is known of the net impacts of the fungi on their vectors, and mites are often completely overlooked. In this chapter, we will describe interactions involving the southern pine beetle (SPB), among the most economically damaging of North American forest insects. We examine SPB interactions with mites, fungi, and other microbes, following the natural temporal progression from beetle attack to offspring emergence from trees. Associations with fungi are universal within bark beetles. Many beetle species possess specialized structures, termed mycangia, for the transport of fungi. The SPB consistently carries three main fungi and numerous mites into the trees it attacks. One fungus, Ophiostoma minus, is carried phoretically on the SPB exoskeleton and by phoretic mites. The mycangium of each female SPB may contain a pure culture of either Ceratocystiopsis ranaculosus or Tntomocorticiumr sp. A. The mycangial fungi are, by definition, transferred in a specific fashion. The SPB possesses two types of gland cells associated with the mycangium. The role of these cells and their products remains unknown. Preliminary studies have observed yeast-like fungal spores in the mycangium and several surrounding tubes that presumably carry secreted chemicals from gland cells (or bacteria) to the mycangium. The degree to which there is selective activity of the glandular chemical secretions remains to be seen. While O. minus may play some role in tree killing, none of these three fungi are highly virulent in their pine hosts. All three fungi grow within the phloem, sporulating heavily in beetle tunnels within which the SPB larvae graze. Though their ecological roles arc complex and context-dependent, these three fungi can be divided into an antagonist (O. minus) and two mutualists (both mycangial fungi, though F,ntnnmcorticium sp. A appears to be of greater benefit to the beetles than C. ranaculosus). Naturally, all three of the fungi compete for access to uncolonized pine phloem. The results of these competitions can have significant impacts on their beetle and mite hosts, and ultimately on the population dynamics of this destructive pest.}, author = {Klepzig, Kier D. and Hofstetter, Richard W.} } @article {12591, title = {Presence and Diversity of Streptomyces in Dendroctonus and Sympatric Bark Beetle Galleries Across North America}, journal = {Microbial Ecology}, volume = {61}, number = {4}, year = {2011}, month = {May}, pages = {759-768}, abstract = {Recent studies have revealed several examples of intimate associations between insects and Actinobacteria, including the Southern Pine Beetle Dendroctonus frontalis and the Spruce Beetle Dendroctonus rufipennis. Here, we surveyed Streptomyces Actinobacteria co-occurring with 10 species of Dendroctonus bark beetles across the United States, using both phylogenetic and community ecology approaches. From these 10 species, and 19 other scolytine beetles that occur in the same trees, we obtained 154 Streptomyces-like isolates and generated 16S sequences from 134 of those. Confirmed 16S sequences of Streptomyces were binned into 36 distinct strains using a threshold of 0.2\% sequence divergence. The 16S rDNA phylogeny of all isolates does not correlate with the distribution of strains among beetle species, localities, or parts of the beetles or their galleries. However, we identified three Streptomyces strains occurring repeatedly on Dendroctonus beetles and in their galleries. Identity of these isolates was corroborated using a house-keeping gene sequence (efTu). These strains are not confined to a certain species of beetle, locality, or part of the beetle or their galleries. However, their role as residents in the woodboring insect niche is supported by the repeated association of their 16S and efTu from across the continent, and also having been reported in studies of other subcortical insects.}, keywords = {Dendroctonus frontalis, Dendroctonus rufipennis}, isbn = {0095-3628}, author = {Hulcr, Jiri and Adams, Aaron S. and Raffa, Kenneth and Hofstetter, Richard W. and Klepzig, Kier D. and Currie, Cameron R.} } @article {12459, title = {Mutualists and Phoronts of the Southern Pine Beetle}, journal = {U S Forest Service General Technical Report SRS}, volume = {140}, year = {2011}, month = {2011}, pages = {161-181}, abstract = {The large numbers of invertebrates and microbes that exist only within dying and decayed pines killed by the southern pine beetle (SPB) make this system ideal for the study of species interactions, including mutualism and phorecy. The associated organisms comprise an entire functioning community that includes fungivores, herbivores, detritovores, scavengers, parasitoids, and predators. Because the SPB causes physical state changes in biotic materials and creates a stable supply of resources for an extensive assemblage of species, it can be considered a keystone species, ecosystem engineer, or foundation species. Within the SPB community, species interactions range from mutualistic to commensafistie to antagonistic, depending on the species composition, environmental conditions, and quality of available resources. These species often use SPB adults to access and disperse among trees and can affect the population dynamics, behavior, and evolution of the SPB. In addition, interactions among the community can impact bark beetle-fungal associations and thus, beetle fitness. In this chapter, I provide an overview of the known associations with the SPB, both mutualistic and phoretic, and discuss how these associations impact the SPB and the evolution and ecology within this community.}, author = {Hofstetter, Richard W.} } @article {12461, title = {Attraction to monoterpenes and beetle-produced compounds by syntopic Ips and Dendroctonus bark beetles and their predators}, journal = {Agricultural and Forest Entomology}, volume = {14}, number = {2}, year = {2012}, month = {May}, pages = {NIL_0094-NIL_0103}, abstract = {1 Bark beetles are significant mortality agents of conifers. Four beetle species, the pine engraver Ips pini, the six-spined pine engraver Ips calligraphus sub. ponderosae, the southern pine beetle Dendroctonus frontalis, and the western pine beetle Dendroctonus brevicomis, cohabitate pines in Arizona. 2 A pheromone trapping study in ponderosa forests of Arizona determined the attraction of beetles to conspecific and heterospecific pheromone components in the presence and absence of host volatiles, and tested whether predators differ in their attraction to combinations of pheromone components and tree monoterpenes. 3 All four bark beetle species differed in their responses to heterospecific lures and monoterpenes. Ips calligraphus was the only species that increased in trap catches when heterospecific lures were added. Heterospecific lures did not inhibit the attraction of either Dendroctonus or Ips species. The replacement of myrcene with a-pinene increased the attraction of Dendroctonus, whereas the addition of a-pinene had mixed results for Ips. The prominent predators Temnochila chlorodia and Enoclerus lecontei were more attracted to the I. pini lure than the D. brevicomis lure, and the combination of the two lures with a-pinene was most attractive to both predator species. 4 Cross attraction and limited inhibition of bark beetles to heterospecific pheromones suggest that some of these species might use heterospecific compounds to increase successful location and colonization of trees. Predator responses to treatments suggest that tree volatiles are used to locate potential prey and predators are more responsive to Ips than to Dendroctonus pheromone components in Arizona.}, keywords = {Dendroctonus}, isbn = {1461-9555}, author = {Hofstetter, Richard W. and Gaylord, Monica L. and Martinson, Sharon and Wagner, Michael R.} } @article {12462, title = {OBSERVATIONS ON THE MITE SCHIZOSTHETUS LYRIFORMIS (ACARI: PARASITIDAE) PREYING ON BARK BEETLE EGGS AND LARVAE}, journal = {Entomological News}, volume = {120}, number = {4}, year = {2009}, month = {September-Octobe}, pages = {397-400}, isbn = {0013-872X}, author = {Hofstetter, Richard W. and Moser, J. C. and McGuire, R.} } @article {11986, title = {Effects of sunlight exposure and log size on pine engraver (Coleoptera: Curculionidae) reproduction in ponderosa pine slash in Northern Arizona, U.S.A}, journal = {Agricultural and Forest Entomology}, volume = {11}, number = {3}, year = {2009}, month = {August}, pages = {341-350}, abstract = {1 Abiotic conditions within logs can affect pine engraver Ips pini (Say) reproductive success, and slash management techniques have been developed that exploit these relationships to reduce brood production. In the present study, we investigated the affect of sunlight exposure on phloem temperature and moisture in logs of two diameters and the subsequent effects on pine engraver reproduction.2 Logs, 30 cm in length, with diameters of 10 and 15 cm, were cut, left in the field for natural colonization by I pini, and then placed in an open meadow and under shade cloth, providing 27\% and 66\% shade, until offspring beetles had left the logs. Phloem temperature and moisture were recorded over the duration of the experiment and, at the end of the field experiment, logs were dissected and galleries were measured to gauge beetle reproductive success.3 As sunlight exposure increased, phloem temperatures increased and potentially lethal temperatures were often reached in the high-sunlight exposure but seldom in the low-sunlight. Smaller diameter logs had drier phloem than larger diameter logs. All logs dried with time but sunlight level did not affect desiccation rates. Ips pini preferred attacking larger logs and the bottom side of logs. Sunlight exposure had a significant effect on net reproductive success in smaller diameter logs, with very little net reproductive success in high-sunlight exposed logs, and the highest reproductive success was found in small diameter logs in the low-sunlight treatments.4 Management implications of these results are discussed.}, isbn = {1461-9555}, author = {Hayes, Christopher J. and Hofstetter, Richard W. and DeGomez, Tom E. and Wagner, Michael R.} } @article {11984, title = {Factors influencing pine engraver (Ips pini Say) colonization of ponderosa pine (Pinus ponderosa Dougl. ex. Laws.) slash in Northern Arizona}, journal = {Forest Ecology and Management}, volume = {255}, number = {8-9}, year = {2008}, month = {15 May}, pages = {3541-3548}, type = {Article}, abstract = {Thinning projects have increased in recent years to reduce standing fuels and fire hazard within the Wildland Urban Interface (WUI) and to improve general forest conditions through forest health restoration treatments. As a consequence, large volumes of thinning slash have been generated, increasing the potential for growth of bark beetle (Ips spp.) populations. Because slash can initiate outbreaks in standing trees, a critical examination of slash management guidelines is needed to minimize bark beetle impacts associated with thinning treatments. Specifically, we examined effects of season of slash cutting, sunlight intensity (stand density) and log size on pine engraver (Ips pini Say) reproduction in North-central Arizona, USA. Ponderosa pine (Pinus ponderosa Dougl ex. Laws.) trees were felled and cut to 16 sizes (diameters of 10, 15, 20, and 25 cm and lengths of 15, 30, 45, and 60 cm) in October, January, April and July, for 2 years. The 16 logs of differing size were placed in groups in overstory stand densities of 5, 14, and 27.5 m2/ha (representing high, partial, and low sunlight levels). Response variables included attack density, emergence density, and beetle population growth rate. Log length had a positive relationship with both attack and emergence density. Log diameter had a significant effect on attack and emergence density, with a preference shown for intermediate diameter bolts. During a year with above average winter precipitation, cutting date and the interaction of cutting date and light level had significant effects on attack density. Fewer beetles attacked both bolts that had been exposed for longer periods of time and logs exposed to high sunlight levels. Cutting date, and the interaction of cutting date and light level, influenced emergence density, but light level alone did not. Emergence density was lowest in spring-cut logs in both years. Cutting date also had an effect on beetle population growth rate, with fall-cut logs having the highest population growth, while light level had no effect. Extended time-since-cutting (e.g. fall cutting), high light levels and small log diameter did not consistently cause reductions in beetle attack and reproductive performance as was hypothesized. Implications of these results for slash management guidelines are discussed.}, keywords = {Ips pini}, isbn = {0378-1127}, author = {Hayes, Christopher J. and DeGomez, Tom E. and McMillin, Joel D. and Anhold, John A. and Hofstetter, Richard W.} } @article {10611, title = {Oleoresin Chemistry Mediates Oviposition Behavior and Fecundity of a Tree-Killing Bark Beetle}, journal = {Journal of Chemical Ecology}, volume = {37}, number = {11}, year = {2011}, month = {Nov}, pages = {1177-1183}, abstract = {Many herbivores are sensitive to the secondary chemistry of their host plants. However, the influence of pine secondary chemicals (monoterpenes) on bark beetle fitness is poorly understood. We tested the hypothesis that the monoterpene composition of the phloem oleoresin of ponderosa pine, Pinus ponderosa var scopulorum, mediates rates of host acceptance, oviposition behavior, and fecundity of the western pine beetle, Dendroctonus brevicomis. We performed reciprocal rearing experiments, controlling for the monoterpene composition (chemotype) of host material. We tested the effects of two geographically interspersed host chemotypes on beetles with unknown (wild) and known (reared F1) chemical histories. Host chemotype and insect chemical history did not affect rates of acceptance of host material by female beetles. Insect chemical history affected egg gallery construction, and beetles constructed egg galleries that were on average 24.3\% longer when reared in host material that was chemically similar to their natal host material. However, mean egg gallery lengths did not differ between host chemotypes. Insect chemical history also influenced fecundity: F1 beetles produced 52.7\% more offspring on average when reared in host material that was chemically similar to their natal host. Our experiments demonstrate that the chemical history of bark beetles mediates egg gallery construction and fecundity, but not host acceptance. This implicates chemical history as a more important factor than host chemotype in the oviposition behavior and fecundity of D. brevicomis.}, keywords = {Dendroctonus brevicomis}, isbn = {0098-0331}, author = {Davis, Thomas S. and Hofstetter, Richard W.} } @article {10612, title = {Plant secondary chemistry mediates the performance of a nutritional symbiont associated with a tree-killing herbivore}, journal = {Ecology (Washington D C)}, volume = {93}, number = {2}, year = {2012}, month = {Feb}, pages = {421-429}, abstract = {Many herbivores consume microbial food sources in addition to plant tissues for nutrition. Despite the ubiquity of herbivore-microbe feeding associations, few studies examine how host plant phenotypes affect microbial symbionts of herbivores. We tested the hypothesis that chemical polymorphism in a plant population mediates the performance of nutritional microbial symbionts. We surveyed the composition of ponderosa pine resin in northern Arizona, USA, for variation in six monoterpenes, and we approximated four chemical phenotypes. We reared populations of an herbivorous tree-killing beetle (Dendroctonus brevicomis) in ponderosa pine host material, controlling for three monoterpene compositions representing an [alpha]-pinene to [DELTA]-3-carene gradient. Beetles were reared in host material where the dominant monoterpene was [alpha]-pinene, [DELTA]-3-carene, or a phenotype that was intermediate between the two. We isolated nutritional fungal symbionts (Entomocorticium sp. B) from beetle populations reared in each phenotype and performed reciprocal growth experiments in media amended to represent four "average{\textquoteright}{\textquoteright} monoterpene compositions. This allowed us to test the effects of natal host phenotype, chemical polymorphism, and the interaction between natal host phenotype and chemical polymorphism on a nutritional symbiont. Three important findings emerged: (1) fungal isolates grew 25-32\% faster when acquired from beetles reared in the intermediate phenotype; (2) the mean growth rate of nutritional fungi varied up to 44\% depending on which monoterpene composition media was amended with; and (3) fungal isolates uniformly performed best in the intermediate phenotype regardless of the chemical composition of their natal host. The performance of nutritional fungi related to both the chemical "history{\textquoteright}{\textquoteright} of their associated herbivore and the chemical phenotypes they are exposed to. However, all fungal isolates appeared adapted to a common chemical phenotype. These experiments argue in favor of the hypothesis that chemical polymorphism in plant populations mediates growth of nutritional symbionts of herbivores. Intraspecific chemical polymorphism in plants contributes indirectly to the regulation of herbivore populations, and our experiments demonstrate that the ecological effects of plant secondary chemistry extend beyond the trophic scale of the herbivore-plant interaction.}, isbn = {0012-9658}, author = {Davis, Thomas S. and Hofstetter, Richard W.} } @article {8574, title = {Why does longleaf pine have low susceptibility to southern pine beetle?}, journal = {Canadian Journal of Forest Research}, volume = {37}, number = {10}, year = {2007}, month = {October}, pages = {1966-1977}, abstract = {Pine forests throughout the world are subject to disturbance from tree-killing bark beetles, but pine species differ in their susceptibilities. In the southeastern United States, Pinus palustris Mill. suffers far less mortality from the southern pine beetle, Dendroctonus frontalis Zimmermann, than do its sympatric congeners. We tested the commonly invoked hypothesis that P. palustris has relatively low susceptibility because it has higher oleoresin flow than other pines, especially Pinus taeda L. However, seven studies in three states over 6 years refuted the hypothesis that P. palustris and P. taeda differ in their constitutive resin flow or in their capacity to replace resin depleted by either experimental wounding or natural beetle attacks. Additionally, surveys of natural beetle attacks revealed that P. taeda and P. palustris were equally likely to be attacked and killed when they cooccurred in front of growing infestations. Thus, the relative susceptibility of these two species changes with the spatial scale at which they are mixed, and the strong landscape-scale pattern of low mortality in P. palustris is not because individual trees are physiologically less susceptible. Ultimately, the conspicuous differential impact of D. frontalis on P. taeda and P. palustris may be the product of coevolution between tree defenses and beetle behavior.}, keywords = {Dendroctonus frontalis}, isbn = {0045-5067}, author = {Martinson, Sharon and Hofstetter, Richard W. and Ayres, Matthew P.} }