Beetle Population Dynamics Research Articles

Population dynamics of cerambycid beetles in the Northern Western Ghats of Sindhudurg District (MS) India

Population dynamics of cerambycid beetles in the Northern Western Ghats of Sindhudurg District (MS) India

The Relationships between the Population Density of Fir Bark Beetles and Niche Breadth.

Bark beetles are a significant link in the chain of diseases that lead to the accelerated dying of firs (Abies alba Mill.), a key species in the cultivation of stable mixed-tree stands. The aim of this work was to evaluate biotic interactions in populations of bark beetles that colonised natural traps made from firs. The tested hypothesis was that the niche breadth of the species increases with the increasing density of the population. The research was carried out in near-natural forests containing fir, growing in the Suchedniów-Oblęgorek Landscape Park in central Poland. Data were collected from 30 traps trees and 30 windfalls in the years 2010-2023. Cryphalus piceae Ratz. prefers heavily weakened trees, as shown by the fact that it colonised all of the natural traps, which lack any defensive reactions. The sampling method used in the study proved effective, as confirmed by the segregation of the niches of all of the bark beetles. Using nonlinear regression (linearisable model and piecewise linear regression), models were constructed that describe the niche breadths of the bark beetles. The niche parameter is correlated with the density of colonisation. The derived models explain around 77-84% of the variation in the niche breadth of bark beetles on natural traps. The mean relative errors of estimation do not exceed 20%. The niche breadth parameter obtained from the derived regression equations may be used in models that describe-for example-the impact of observed climate change on the population dynamics of bark beetles.

Population’s preference of rhinoceros beetle (Oryctes rhinoceros) between oil palm (Elaeis guineensis) and coconut palm (Cocos nucifera l.): Contributing to pest’s controlling strategy

The rhinoceros beetle (Oryctes rhinoceros) began to establish itself in Malaysia with the emergence of coconut cultivation. Rhinoceros beetles were well adapted to survive on oil palm (Elaeis guineensis) and coconut (Cocos nucifera L.) trees. Different host plants could have different interactions and food preferences with the Rhinoceros beetle against their host plant, even within the same family. Additionally, climatic change, particularly rainfall, could also influence the population dynamics of O. rhinoceros especially in terms of the biological aspect of the pest. This study was carried out to evaluate the difference in population of rhinoceros beetles between oil palm and coconut palm as a preference host comparison in relation to the climatic factors on the plantation scale. The population of rhinoceros beetles was found to be higher in oil palm as compared to coconut palm. It can be concluded that rhinoceros beetles highly prefer oil palms when compared to coconut palms. This study highlighted the importance of planting similar families in order to reduce the risk of pest attacks. This study also found that climate is one of the factors influences the population dynamics of rhinoceros beetles and puts pressure on plants, subsequently making it a favorable condition for rhinoceros beetles in the field. Interestingly, female rhinoceros beetle in an oil palm field was significantly correlated with the rainfall. Therefore, preventive measures need to be taken during the rainy season, considering the high risk of planting nearby and/or similar plants.

Coupling Mountain Pine Beetle and Forest Population Dynamics Predicts Transient Outbreaks that are Likely to Increase in Number with Climate Change.

Mountain pine beetle (MPB) in Canada have spread well beyond their historical range. Accurate modelling of the long-term dynamics of MPB is critical for assessing the risk of further expansion and informing management strategies, particularly in the context of climate change and variable forest resilience. Most previous models have focused on capturing a single outbreak without tree replacement. While these models are useful for understanding MPB biology and outbreak dynamics, they cannot accurately model long-term forest dynamics. Past models that incorporate forest growth tend to simplify beetle dynamics. We present a new model that couples forest growth to MPB population dynamics and accurately captures key aspects of MPB biology, including a threshold for the number of beetles needed to overcome tree defenses and beetle aggregation that facilitates mass attacks. These mechanisms lead to a demographic Allee effect, which is known to be important in beetle population dynamics. We show that as forest resilience decreases, a fold bifurcation emerges and there is a stable fixed point with a non-zero MPB population. We derive conditions for the existence of this equilibrium. We then simulate biologically relevant scenarios and show that the beetle population approaches this equilibrium with transient boom and bust cycles with period related to the time of forest recovery. As forest resilience decreases, the Allee threshold also decreases. Thus, if host resilience decreases under climate change, for example under increased stress from drought, then the lower Allee threshold makes transient outbreaks more likely to occur in the future.

Climate-driven tree growth and mortality in the Black Forest, Germany-Long-term observations.

Episodic tree mortality can be caused by various reasons. This study describes climate-driven tree mortality and tree growth in the Black Forest mountain range in Germany. It is based on a 68-year consistent data series describing the annual mortality of all trees growing in a forest area of almost 250 thousand ha. The study excludes mortality caused by storm, snow and ice, and fire. The sequence of the remaining mortality, the so-called "desiccated trees," is analyzed and compared with the sequence of the climatic water balance during the growing season and the annual radial growth of Norway spruce in the Black Forest. The annual radial growth series covers 121 years and the climatic water balance series 140 years. These unique time series enable a quantitative assessment of multidecadal drought and heat impacts on growth and mortality of forest trees on a regional spatial scale. Data compiled here suggest that the mortality of desiccated trees in the Black Forest during the last 68 years is driven by the climatic water balance. Decreasing climatic water balance coincided with an increase in tree mortality and growth decline. Consecutive hot and dry summers enhance mortality and growth decline as a consequence of drought legacies lasting several years. The sensitivity of tree growth and mortality to changes in the climatic water balance increases with the decreasing trend of the climatic water balance. The findings identify the climatic water balance as the main driver of mortality and growth variation during the 68-year observation period on a landscape-scale including a variety of different sites. They suggest that bark beetle population dynamics modify mortality rates. They as well provide evidence that the mortality during the last 140 years never was as high as in the most recent years.

Suitability of a Historical, Novel, and Occasional Host for Mountain Pine Beetle (Coleoptera: Curculionidae)

The mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae), recently underwent a notable range-expansion event in western Canada, resulting in access to the novel host jack pine, Pinus banksiana Lamb. We assessed the suitability of jack pine for mountain pine beetle, as well as the historic host lodgepole pine, Pinus contorta Dougl. var. latifolia Engelm., and the non-Pinus host white spruce, Picea glauca (Moench) Voss, to help inform an assessment of the risk of future spread into Canada’s boreal forest and to further our understanding of host use in bark beetles. Several performance traits we measured were similar between lodgepole pine and jack pine, but gallery length and productivity indicated that lodgepole pine was the more suitable host. Development appeared to be faster in jack pine; however, in contrast to previous studies, we attribute it to oviposition arresting earlier in the novel host compared to the other hosts and not a difference in development rate. Initial productivity was surprisingly high in spruce, but we found evidence of a delayed negative effect that manifested as reduced cold tolerance, delayed development, and high mortality of late-instar larvae. Although jack pine is a suitable host for the mountain pine beetle, our results indicate that the beetle’s eruptive potential could be lower in jack pine compared to lodgepole pine, given all other factors are equal. Other factors that may also affect mountain pine beetle population dynamics require additional research and include the composition and structure of jack pine forests, environmental conditions, and biotic interactions.

Flexibility in the ambrosia symbiosis of Xyleborus bispinatus.

Ambrosia beetles maintain strict associations with specific lineages of fungi. However, anthropogenic introductions of ambrosia beetles into new ecosystems can result in the lateral transfer of their symbionts to other ambrosia beetles. The ability of a Florida endemic ambrosia beetle, Xyleborus bispinatus, to feed and establish persistent associations with two of its known symbionts (Raffaelea subfusca and Raffaelea arxii) and two other fungi (Harringtonia lauricola and Fusarium sp. nov.), which are primary symbionts of invasive ambrosia beetles, was investigated. The stability of these mutualisms and their effect on the beetle's fitness were monitored over five consecutive generations. Surface-disinfested pupae with non-developed mycangia were reared separately on one of the four fungal symbionts. Non-treated beetles (i.e., lab colony) with previously colonized mycangia were used as a control group. Xyleborus bispinatus could exchange its fungal symbionts, survive, and reproduce on different fungal diets, including known fungal associates and phylogenetically distant fungi, which are plant pathogens and primary symbionts of other invasive ambrosia beetles. These changes in fungal diets resulted in persistent mutualisms, and some symbionts even increased the beetle's reproduction. Females that developed on Fusarium sp. nov. had a significantly greater number of female offspring than non-treated beetles. Females that fed solely on Harringtonia or Raffaelea symbionts produced fewer female offspring. Even though some ambrosia beetles like X. bispinatus can partner with different ambrosia fungi, their symbiosis under natural conditions is modulated by their mycangium and possibly other environmental factors. However, exposure to symbionts of invasive beetles can result in stable partnerships with these fungi and affect the population dynamics of ambrosia beetles and their symbionts.

A Mass Reproduction Outbreak and Estimation of the Spreading Risks for the Small Spruce Bark Beetle in Cedar Pine Forests of the Tomsk Region

The results of studying the mass reproduction outbreak of a new invasive pest of the Siberian pine (Pinus s-ibirica Du Tour), the small spruce bark beetle (Ips amitinus (Eichh.)), observed in Siberia for the first time, are presented in this paper. The studies were carried out in the south-eastern part of Western Siberia, within the Tomsk region, in pine forests damaged by an invasive bark beetle. It is shown that the occurrence of the outbreak was provoked by favourable weather conditions of recent decades and the abundance of trees, weakened for various reasons, in the recipient ecosystems of the invasion, among which the outbreak of the Siberian moth in 2016–2018 was of great importance. The small spruce bark beetle population dynamics in new habitats was compared with the native area in Europe, and certain peculiarities were revealed: an increase in the populations’ numbers level, a narrowing of trophic specialisation up to a regional monophagy, a decrease in the role of an interspecific competition due to the displacement of local stem dendrophagous species by the invader, the simultaneous existence of outbreak foci in different development stages and the correlation between their characteristics, the species composition of the forest stands and the weakening factors. An original method for assessing the spreading risk for an outbreak of the small spruce bark beetle breeding in the Tomsk region under the influence of a complex of factors that contribute to an increase in its number has been proposed and implemented at the forestries level.

Is the effectiveness of policy-driven mitigation measures on carabid populations driven by landscape and farmland heterogeneity? Applying a modelling approach in the Dutch agroecosystems.

The growing challenges of protecting biodiversity in agro-ecosystems and maintaining high agricultural productivity has become an important issue within the European Union, shaping both European and national agro-policies. The presented study is part of a broader evaluation of the interim targets of the 2013 Dutch policy plan on sustainable use of pesticides, carried out in 2019 by the PBL (Planbureau voor de Leefomgeving) Netherlands Environmental Assessment Agency. We aimed to assess the effectiveness of selected mitigation measures suggested in the policy plan on non-target terrestrial arthropods using a common carabid beetle Bembidion lampros as a model species. We combined dynamic landscape models with detailed agent-based population modelling to simulate impacts of reduction of toxicity of insecticides, reduction of spray drift to the off-crop area, and increase in area of field margins on the beetle population dynamics in ten agricultural landscapes representing different farming systems. Our simulations showed that a shift towards low-risk products should be the priority if the goal is to increase beetle range. To promote local beetle abundance this needs be coupled with increasing amount of field margins in a landscape. Overall, the observed treatment and landscape effects were highly context-specific and therefore we suggest that care is used when defining and interpretting metrics based on population effects of policy measures. This caveat notwithstanding, the use of simulation to assess complex interactions between landscape, ecology and behaviour of species, and policy measures can be a powerful tool supporting innovative policy management. This should include the development of landscape-context specific targets and/or mitigation measures.

Resource amount and discontinuity influence flight and reproduction in Hippodamia convergens (Coleoptera: Coccinellidae)

AbstractIndustrial‐scale agriculture creates a mosaic of large monocultures in the landscape, where seasonal cropping cycles generate discontinuous resource availability for insect predators both spatially and temporally. In this environment, selection will favor predator movement and reproductive behaviors that optimize the location and effective utilization of resource (prey) pulses that are both patchy and ephemeral in nature. Using a model system to study predator movement and reproduction, we tested how discontinuous periods of food resource access that mimic fluctuating resource populations (aphids) would influence flight behavior and reproduction of a highly mobile predator, Hippodamia convergens (convergent lady beetle), and possibly modify energetic trade‐offs between these behaviors. Adult beetles were provided either short (3 h) or long (6 h) food pulses daily (continuous availability) or short (6 h) or long (12 h) food pulses every other day (discontinuous availability). We measured preoviposition period, fecundity, and fertility during an 18‐day oviposition period, and female tethered flight activity (3 h) before and after the oviposition period. We found that discontinuous food access delayed the onset of oviposition in the high food quantity treatment; fewer females laid eggs overall, and 18‐day fecundity was lower compared with continuous provision of the same food quantity. A longer preoviposition period was associated with fewer reproductive days and lower fitness. Flight distance and fecundity were negatively correlated, suggesting that energetic expenditure in flight can deplete energetic reserves otherwise used for subsequent reproduction. The negative effects of discontinuous resource access at fine temporal scales reveal how gaps in resource availability could influence lady beetle population dynamics and their ecosystem services within the agricultural landscape.

Population dynamics of predatory ground beetles (Coleoptera, Carabidae) in agrocenoses with different levels of intensification in the forest-steppe zone of Western Siberia

Population dynamics of predatory ground beetles (Coleoptera, Carabidae) in agrocenoses with different levels of intensification in the forest-steppe zone of Western Siberia

Incidence of Wood Boring Bostrychid Beetles in Different Wood Yards at Mettupalayam

An experiment was conducted to document the population dynamics of wood-boring bostrychid beetles collected from different wood yards at Mettupalayam, Tamil Nadu. The abundance of wood boring beetles showed that out of 455 individual beetles collected from different wood pieces, 319 beetles belonged to the family bostrychidae. Sinoxylon sp. (Coleoptera: Bostrychidae) was the dominant species accounting 76.70 percent. Diversity indices were calculated for the wood-boring beetles recorded as Shannon Diversity Index (H) (1.34), Species richness (Margalef) (0.43), Species Diversity (D) (3.67) and Pielou’s Species Eveness (0.97). The number of exit holes were evaluated, which showed that the wood samples from sites 3, 4 and 5 had significantly higher number of exit holes than those recorded at sites 1 and 2. The size of exit holes bored by beetles showed that the wood samples of teak, silver oak, neem and eucalyptus have the maximum number of exit holes with 1.1-2.0 mm

Review of the Potential Effects of Shifting Southern Pine Beetle (Dendroctonus Frontalis) Population and Outbreak Dynamics

Review of the Potential Effects of Shifting Southern Pine Beetle (Dendroctonus Frontalis) Population and Outbreak Dynamics

Warming increased bark beetle-induced tree mortality by 30% during an extreme drought in California.

Quantifying the responses of forest disturbances to climate warming is critical to our understanding of carbon cycles and energy balances of the Earth system. The impact of warming on bark beetle outbreaks is complex as multiple drivers of these events may respond differently to warming. Using a novel model of bark beetle biology and host tree interactions, we assessed how contemporary warming affected western pine beetle (Dendroctonus brevicomis) populations and mortality of its host, ponderosa pine (Pinus ponderosa), during an extreme drought in the Sierra Nevada, California, United States. When compared with the field data, our model captured the western pine beetle flight timing and rates of ponderosa pine mortality observed during the drought. In assessing the influence of temperature on western pine beetles, we found that contemporary warming increased the development rate of the western pine beetle and decreased the overwinter mortality rate of western pine beetle larvae leading to increased population growth during periods of lowered tree defense. We attribute a 29.9% (95% CI: 29.4%-30.2%) increase in ponderosa pine mortality during drought directly to increases in western pine beetle voltinism (i.e., associated with increased development rates of western pine beetle) and, to a much lesser extent, reductions in overwintering mortality. These findings, along with other studies, suggest each degree (°C) increase in temperature may have increased the number of ponderosa pine killed by upwards of 35%-40% °C-1 if the effects of compromised tree defenses (15%-20%) and increased western pine beetle populations (20%) are additive. Due to the warming ability to considerably increase mortality through the mechanism of bark beetle populations, models need to consider climate's influence on both host tree stress and the bark beetle population dynamics when determining future levels of tree mortality.

Population dynamics of red flour beetle (Tribolium castaneum (Herbst)) under different temperatures and patch sizes

Population dynamics of red flour beetles, Tribolium castaneum (Herbst), was determined using three different sizes of grain patch (bulk) at different temperature profiles. Grain patches were 0.03 kg, 2 kg, and 14 kg of wheat with 14.5% moisture content (wb). The temperature profiles tested were constant temperatures of 21, 25, 30, 35 °C, and incrementally decreased or increased temperatures (T-decrease (Td) and T-increase (Ti)). Every 28 d up to 168 d, the live and dead adults were separated from the wheat and their numbers counted. At Td, adults were separated and counted every 28 d during the first 140 d, then one last time 70 d later. After separating and counting, these adults were discarded and the wheat, which contained immature stages, was incubated at 30 °C. Four weeks later the emerged adults (referred to as “offspring”) were counted. The number of both adults and offspring showed great variation among temperatures at the same storage time and the same patch size. The peak number and density of insects also showed variation among different temperatures and patch sizes. Peak live adult density was the highest in the small patches. The peak live adult densities were 300 ± 50 at 21 °C, 673 ± 118 at 25 °C, 689 ± 48 at 30 °C, 1100 ± 150 at 35 °C, 1150 ± 150 at Td, and 1133 ± 94 adults/kg at Ti. The offspring density at 35 °C was higher than that at other temperatures in the small patches. Even though many factors and their interaction influenced population dynamics of T. castaneum, the number of insects was mainly influenced by temperature at the same patch size, while large patch size could provide more room for insects to multiply.

Landscape-Scale Drivers of Resistance and Resilience to Bark Beetles: A Conceptual Susceptibility Model

Bark beetle (Dendroctonus spp.) outbreaks in the middle latitudes of western North America cause large amounts of tree mortality, outstripping wildfire by an order of magnitude. While temperatures play an important, and direct role in the population dynamics of ectothermic bark beetles, an equally important influence is the nature of the host substrate—the structure and composition of forested communities. For many of the dominant tree species in the western United States, “hazard” indices have been developed for specific bark beetles, which generally include three key variables—host tree size, absolute or relative density of the stand, and percentage of host composition. We provide a conceptual model to apply these three variables across forest ecosystems and bark beetles that shifts the thinking from a species–specific model to a model which focuses on the underlying ecological factors related to bark beetle outbreak susceptibility. We explored the use of our model across multiple scales using the Forest Inventory and Analysis database: Interior West, USA; the states of Colorado and Arizona; and specific national forests within Arizona that are implementing a large-scale restoration effort. We demonstrated that across the Interior West and Colorado, the vast majority of forests have moderate to high susceptibility to bark beetles. Our conceptual model maintains the simplicity of previous “hazard” models but acknowledges the need to consider scale when managing bark beetles. It also shifts the management approach from resistance thinking to the development of “associational resilience”, where the focus is not on any one individual stand or area but the longer-term perspective of forest persistence across the landscape.

Field Translocation of Mountain Pine Beetles Suggests Phoretic Mite Communities Are Locally Adapted, and Mite Populations Respond Variably to Climate Warming.

Simple SummaryClimate warming has significant effects on forest insect populations, particularly bark beetles, which cause millions of hectares of forest tree damage. Bark beetles live alongside a diverse host of other organisms which affect the success of beetle attacks on trees and are also affected by climate changes. Here, we explore climate effects on symbiotic mite communities associated with the mountain pine beetle (Dendroctonus ponderosae). We show that warming causes significant shifts in the abundance of mites. These effects were dependent on source population, suggesting mite populations are adapted to their local climates. Understanding beetle–mite patterns is important because mites can directly affect beetle reproduction by feeding on eggs, or indirectly affect beetle health by introducing fungi. Our results provide foundational information for understanding how climate change will affect beetle–mite associations; and serve to help determine how these shifting associations will affect the success of bark beetles in forest ecosystems.Temperature is a key determining factor in the population dynamics of forest insects and their associated biota. Bark beetles, often considered key agents of change in forest ecosystems, are particularly affected by warming in their environment. Beetles associate with various phoretic mite species that have direct/indirect effects on beetle fitness and population dynamics, although there is limited knowledge of how temperature affects these communities. Here, we use a field reciprocal translocation experiment with the addition of a novel “warming” environment to represent future changes in local environment in two populations of a keystone bark beetle species (Dendroctonus ponderosae). We hypothesize that mite community abundances as carried by bark beetles are significantly altered when not in their native environments and when subjected to climate warming. We use multivariate generalized linear models based on species abundance data to show that mite community compositions significantly differ across different field climates; and that these patterns diverge between source populations, indicating local adaptation. Our study offers foundational information on the general effects of simulated climate-warming on the compositional shifts of common and abundant biotic associates of mountain pine beetles and may be used as a model system for other important insect–mite systems.

Spread of Dutch elm disease in an urban forest

A complex network model for the spread of Dutch Elm Disease in an urban forest is formulated. American elms are the focus of the model. Each elm can be in one of five states, a combination of their life and epidemiological status. Each tree is also potentially a host to a population of elm bark beetles, the vectors of Dutch Elm Disease. The epidemiological dynamics of trees is governed by a stochastic process that takes into account the dispersal of spore-carrying beetles between trees and potential contacts between tree root systems. The model describes seasonal variations of beetle activity and population dynamics. Numerical simulations and sensitivity analyses of the model are carried out. In this introductory paper, we use data from the City of Winnipeg, where Dutch Elm Disease is prevalent, and focus on two neighbourhoods representative of a residential area and an area with urban parks.

Physical and chemical characteristics of blue and Engelmann spruce relative to spruce beetle host selection and colonization

Bark beetles are keystone species that can alter the structure and function of forested ecosystems, yet the mechanisms underlying host selection and successful colonization remain poorly understood for most species. Comparison of closely related tree species that vary in their susceptibility to bark beetles could provide insights into such mechanisms. Here, we compare physical and chemical characteristics of blue (Picea pungens Engelm.) and Engelmann (Picea engelmannii Parry ex Engelm.) spruce, species rarely (blue) and frequently (Engelmann) selected and colonized by the spruce beetle (Dendroctonus rufipennis Kirby) in the western U.S. At three sites (Utah, U.S.) where these species co-occur, 15 trees of each species were selected and traits important for bark beetle survival and population dynamics were measured and compared (bark and phloem thickness, resin flow, phloem and volatile chemistry, beetle landing and colonization success). There were significant differences in bark and phloem thickness and resin flow between species. Bark was thicker and phloem was thinner in blue spruce than Engelmann spruce whereas resin flow was highly variable but greater in blue spruce. Concentrations of within-phloem terpenes in blue spruce were more than double those for Engelmann spruce. Engelmann spruce foliage emitted greater concentrations of volatiles than blue spruce. Spruce beetles landed at higher rates on baited Engelmann spruce than baited blue spruce, and Engelmann spruce was more likely to be colonized. Collectively, these results suggest that blue spruce is a less suitable host for spruce beetle than Engelmann spruce due to a combination of factors including: thicker bark, thinner phloem, higher resin flow, lower concentrations of volatile terpenes, and higher concentrations of constitutive terpenes in phloem tissue, several which are known to be toxic to spruce beetles.

Lightning Damage Facilitates Beetle Colonization of Tropical Trees

Abstract Lightning is a common agent of disturbance in many forest ecosystems. Lightning-damaged trees are a potentially important resource for beetles, but most evidence for this association is limited to temperate pine forests. Here, we evaluated the relationship between lightning damage and beetle colonization of tropical trees. We recorded the number of beetle holes on the trunks of trees from 10 strike sites (n = 173 lightning-damaged trees) and 10 matching control sites (n = 137 control trees) in Panama. The trunks of lightning-struck trees had 370% more beetle holes than control trees. The abundance of beetle holes increased with increasing total crown dieback among both control and lightning-damaged trees, and with larger tree diameter among lightning-struck trees. Beetle holes also were more abundant in trunk sections of lightning-damaged trees located directly below a damaged section of the crown. The results of this study suggest that lightning damage facilitates beetle colonization in tropical forest trees and provide a basis for investigations of the effects of lightning-caused disturbance on beetle population dynamics and assemblage structure.