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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"Different aspects of the dispersal patterns and movements of various bark beetle species have been quantitatively measured and simulated (Duelli et al., 1997; Byers, 2000; Cronin et al., 2000; Lausch et al., 2011). Due to technical, financial and methodological limitations of the experimental design of mark-recapture methods for the bark beetle, many studies only relate to small-scale surveys and frequently to data from point counts. "
[Show abstract][Hide abstract] ABSTRACT: The Bavarian Forest National Park in Germany has experienced infestations of bark beetle (Ips typographus L.) since the 1980s, 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.
Full-text · Article · Aug 2013 · Ecological Indicators
"Several methods are available to study insect dispersal, e.g. mark-recapture (Cronin et al., 2000; Arellano et al., 2008), harmonic radar (Riley et al., 1996; O'Neal et al., 2005), tethering experiments (Boiteau & Colpitts, 2001; Dubois et al., 2010) and radio telemetry (Hedin & Ranius, 2002; Beaudoin-Ollivier et al., 2003; Rink & Sinsch, 2007). These methods give different types of information, with different risks of biases. "
[Show abstract][Hide abstract] ABSTRACT: 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).
Telemetered beetles spent their lifetime not only inside hollow trees but also in other habitats, such as above or under the ground surface.
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.
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.
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.
Full-text · Article · May 2013 · Insect Conservation and Diversity
"The number of recaptured (marked) insects was determined at each distance and direction. For T. dubius, we recorded the sex and measured elytral length of marked beetles because it appears that dispersal distance is related to beetle size (Cronin et al., 2000). The replicates and total numbers released are summarized in Table 1. "
[Show abstract][Hide abstract] 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
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.
Full-text · Article · Feb 2013 · Agricultural and Forest Entomology