The pattern and range of movement of a checkered beetle predator relative to its bark beetle prey
ABSTRACT Theoretical studies of predator-prey population dynamics have increasingly centered on the role of space and the movement of organisms. Yet, empirical studies have been slow to follow suit. Herein, we quantified the long-range movement of a checkered beetle, Thanasimus dubius, which is an important predator of a pernicious forest pest, the southern pine beetle, Dendroctonus frontalis. Adult checkered beetles were marked and released at five sites and subsequently recaptured at traps baited with pine and pine beetle semiochemicals and located at distances up to 2 km away from the release point. While the pattern of recaptures-with-distance at each site provided a modest fit to a simple random-diffusion model, there was a consistent discrepancy between observed and expected recaptures: a higher than expected proportion of beetles were recaptured at the more distant traps. To account for this deviation, we developed a model of diffusion that allowed for simple heterogeneity in the population of marked beetles; i.e., a slow and fast moving form of the checkered beetle. This model provided a significantly better fit to the data and formed the basis for our estimates of intra-forest movement. We estimated that on average, one half of the checkered beetles dispersed at least 1.25 km, one third dispersed>2 km, and 5% dispersed>5 km. The source of the heterogeneous dispersal rates were partially due to differences in beetle size: smaller beetles (for both males and females) were more likely to be recaptured away from the release site than larger beetles. The southern pine beetle (prey for the checkered beetle) exhibited no significant heterogeneity in dispersal ability and provided a very good fit to the simple diffusion model. The only difference in dispersal between these two species was that checkered beetles were undergoing greater long-distance dispersal than the pine beetles (the radius containing 95% of the dispersing individuals was 5.1 km for the checkered beetle and 2.3 km for the pine beetle). Data on the movement of these two species is used to evaluate a general model of spatial pattern formation in a homogeneous environment, and the potential of the checkered beetle as a biological control agent for the southern pine beetle.
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ABSTRACT: The Bavarian Forest National Park in Germany has experienced infestations of bark beetle (Ips typographus, L.) since the 1980’s, resulting in considerable ecological loss due to the destruction of almost 5800 ha of spruce forests. Although there have been numerous investigations on the physiology and ecology of the bark beetle, until now the spatio-temporal infestation and dispersal dynamics of the bark beetle over a longer period have still not been satisfactorily understood. The understanding of the structure and the dispersal of bark beetle infestations is however of significant importance for forest management systems in order to predict the risk of outbreaks, especially in the face of climate change. The aim of this investigation was therefore (I) to analyse and describe the long term spatio-temporal infestation patterns of Ips typographus in the Bavarian Forest National Park, Germany on the landscape scale, (II) to conduct investigations on spatio-temporal shifts of the focal points of bark beetle infestations from 1988 to 2010 and (III) to compare the quantitative spatio-temporal infestation patterns obtained at the landscape level with the dispersal patterns of the spatially explicit agent-based simulation model (SAMBIA) for Ips typographus (Fahse and Heurich, 2011). The results of the study show that a shift in the infestation pattern of Ips typographus from 1988 to 2010 occurs at different time intervals both anisotropically as well as isotropically. Furthermore, the dispersal pattern of the bark beetle was recorded quantitatively and described extensively over a period of 23 years on the landscape scale. The quantification of the presence and dispersion pattern of Ips typographus in the Bavarian Forest National Park allows us to gain a better understanding of the distribution pattern of the bark beetle on the landscape scale. In this way, both the pattern and structure of infestation patterns obtained for Ips typographus serve as: (a) a basis for the criteria to improve the parameters of spatio-temporal simulation models, (b) a better understanding of the bark beetle pattern and existing processes such as disturbance patterns or damage patterns in the food web of spruces due to climate change, (c) a test for the hypotheses on the relationships between the presence of bark beetle and relevant habitat variables as well as (d) the compilation of forecast models on the dispersal of bark beetle. These predictions can help with the implementation of specific management strategies to prevent the dispersal of bark beetle.Ecological Indicators 01/2013; 31:73-81. · 2.89 Impact Factor
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ABSTRACT: Abstract. 1. Dispersal patterns of a beetle inhabiting tree hollows, Osmoderma eremita (Scopoli, 1763) (Coleoptera: Cetoniidae), were studied in a cork oak (Quercus suber) woodland in central Italy, the southernmost part of its distribution range. During 2 years, we used radio telemetry to monitor dispersal of 39 free-ranging individuals (16 males, 23 females). 2. Telemetered beetles spent their lifetime not only inside hollow trees but also in other habitats, such as above or under the ground surface. 3. Beetles were more active at the beginning of the season. Eighty-one per cent of the males and 69% of the females conducted dispersals during their lifetime. 4. The dispersal distance over individuals’ lifetime did not differ between sexes. The longest dispersal was conducted by a female that moved 1504 m. Thirty-nine per cent of dispersing individuals reached distances farther than 250 m. Both dispersal rate and range are higher than what has been found in Northern Europe. 5. The population size per tree is low, most of the adults leave their natal tree, and a high predation rate (at least 28%) was observed among dispersing beetles. Therefore, to balance the local extinction risk from single trees, a high density of hollow trees is probably required. It is desirable that suitable trees are concentrated at a spatial scale of a few hundred metres.Insect Conservation and Diversity 01/2013; 6:309-318. · 1.94 Impact Factor
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ABSTRACT: 1 Quantifying dispersal in predator–prey systems can improve our understanding of how these species interact in space and time, as well as their relative distributions across complex landscapes. 2 We measured the dispersal abilities of three forest insects associated with red pine decline: the eastern five spined pine engraver Ips grandicollis (Coleoptera: Curculionidae), its main predator Thanasimus dubius (Coleoptera: Cleridae) and the basal stem and root colonizer Dendroctonus valens (Coleoptera: Curculionidae). We also examined the edge behaviours of these species and the predator Platysoma spp (Coleoptera: Histeridae) between red pine stands (habitat) and clearings (nonhabitat). 3 Thanasimus dubius dispersed 12 times farther than its prey I. grandicollis, with 50% of predators dispersing farther than 1.54 km. This profound difference in dispersal behaviour between prey and predator may contribute to the clumped distribution of I. grandicollis. 4 Most T. dubius and D. valens were confined in the pine forest, thus showing strong edge behaviour. This differed from I. grandicollis and Platysoma spp., which were commonly found in open areas adjacent to red pine plantations. 5 The bark beetle I. grandicollis and one of its main predators, T. dubius, exhibited different patterns of movement within a fragmented landscape. Despite a greater dispersal ability of T. dubius within forests, the spatial distribution of this predator may be restricted by fragmentation of its habitat, and provide an opportunity for partial escape of its prey. 6 The present study contributes to our knowledge of top-down forces within red pine stands undergoing decline. Differences of dispersal patterns and edge behaviour could contribute to the initiation of new pockets of decline, as well as the connectedness among existing ones.Agricultural and Forest Entomology 01/2013; 15:1-11. · 1.47 Impact Factor