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Ectotherms are largely impacted by extreme climate events, essentially heatwaves. In Tunisia, the pine processionary moth (PPM), Thaumetopoea pityocampa, is a defoliator typically laying eggs in summer. Its geographical range is expanding northwards in Europe while retracting from southern Tunisia where summer temperatures can reach extreme heats. We explored the effects of climate change over the last 30 years on PPM at its southern range edge. We investigated variations of fecundity and causes of egg mortality over time using historical and contemporary collections of egg masses. Due to incomplete historical series, a clustering method was used to group climatically homologous sampling sites and perform allochronic analyses on clusters instead of individual localities. Our results suggest negative effects of summer heat on egg survival, down to 0% hatching rate in one site during a major heatwave. Such high hatching failures resulted partly from high egg sterility and aborted embryos, with little effects of parasitism rate, suggesting heat susceptibility during embryonic development, but our results do not allow distinguishing impeded mating success from failed egg maturation or early embryo death. Decreasing female fecundity was observed in regions where allochronic comparisons were possible, associated with a decrease in parasitism rate, while climatic variability increased. Previous studies have confirmed experimentally the thermal sensitivity of PPM early instars to temperatures observed in the present work, including one population from southern Tunisia. However, further work is required to evaluate the relative importance of warming summers among populations, since the risk of heat stress depends on the phenology of sensitive instars, and populations from the warmest areas may not necessarily be the most vulnerable to climate change if they already evolved phenological heat avoidance. In addition to heat‐induced mortality, the ultimate fitness of heat survivors should also be explored to determine potential carry‐over effects on subsequent life stages. [ABSTRACT FROM AUTHOR]

The woolly poplar aphid Phloeomyzus passerinii Signoret (Aphididae: Phloeomyzinae) is a major pest of poplar plantations. We hypothesized that recent temperature increases may have contributed to the emergence and subsequent northward expansion of outbreaks in France.We reared P. passerinii at four temperatures to estimate its thermal requirements. We used experimental data to parametrize a mechanistic and temperature‐driven physiologically‐based demographic model. The model was used to simulate the effect of temperature on aphid dynamics and to assess the role of climate warming on the spatiotemporal dynamics of outbreaks.The lower developmental threshold was estimated at 6.4 °C and the development degree‐days at 171.Our model supports the hypothesis that recent warming may have promoted outbreaks in northern France. During recent exceptionally warm years, more than 70% of the northern poplar area was favourable for outbreaks.Our model suggests that climate warming is not the sole factor involved. The dominance of resistant poplar genotypes such as 'Robusta' or 'Beaupré' may have preserved plantations from outbreaks before 1996 in southern France and until 2000 in the central part. Other factors, including biological characteristics, biotic interactions, or precipitation should be investigated. [ABSTRACT FROM AUTHOR]

The invasive pine wood nematode (PWN) Bursaphelenchus xylophilus is one of the most serious threats to pine forests across the world. Detected in Europe in 1999, it has largely spread despite containment measures.Following the European Union regulations, the requested eradication measure is to fell, remove and dispose of all susceptible plants within a clear‐cut zone (CCZ) of a radius of 500 m around any infected tree. This measure is controversial since its effectiveness is questioned.An individual‐based model, describing the dispersal of the nematode vector and the nematode transmission, was used to estimate the relationship between the radius and the effectiveness of the CCZ at eradicating the PWN.Clear‐cutting of a 500‐m radius is poorly effective in non‐fragmented pine forests since it reduces the number of PWN transmissions by only 0.6%–11.5%. To significantly reduce the number of transmissions, the radius should be between 14 and 38 km, which is not technically nor ethically feasible.Policy implications. Our results, based on model simulations at a fine spatial scale, prove that clear‐cutting susceptible trees 500 m around any infested tree—as requested by EU regulation to eradicate the PWN—is not effective in large and continuous pine forests. Instead, strengthened surveillance and sanitation felling could be explored. [ABSTRACT FROM AUTHOR]

Pheromone traps are widely used for monitoring or managing insect pest populations. However, it is important to know their range of attraction to optimize the setting of pheromone trap networks.We propose an easy method based on the use of pairs of adjacent traps located at decreasing distance from each other. The range of attraction is deduced from the observation of reduced trap capture when the attraction range of two adjacent traps starts overlapping. The relationship between the relative trap capture and the distance between paired traps is fitted with a logistic curve.To empirically test these predictions, we conducted trapping experiments with the beetle Monochamus galloprovincialis, the insect vector of the pine wood nematode. Fifteen pairs of traps separated by 25 to 300 m, in France, and 18 pairs of traps distant from 25 to 400 m, in Portugal, were installed in maritime pine plantation landscapes.In both countries, the relative percentage of capture per trap per week was best fitted by a logistic model with two parameters. The estimated attraction ranges were 92 m (confidence interval = 62–211 m) in France and 123 m (confidence interval = 64–491 m) in Portugal.The interference between paired traps thus provides a simple and robust method for estimating the attraction range of pheromone traps. [ABSTRACT FROM AUTHOR]

The invasive yellow-legged hornet was first discovered in Europe, in south-western France, in 2004. It has since spread very rapidly and has caused significant mortality among honeybees and native entomofauna. It also poses a risk to humans because its sting provokes allergic reactions. The objectives of this study were the following: (i) to disentangle the roles played by human-mediated dispersal and self-mediated dispersal in the species' rapid range expansion and (ii) to estimate the intensity of control measures in France and determine what needs to be done to slow the hornet's spread and dramatically reduce its population densities., A mathematical model was developed to describe the hornet's potential spread. This model included parameters describing the population growth rate, carrying capacity, self-mediated dispersal, human-mediated dispersal and the efficacy of control measures (i.e. the destruction of detected nests). Model parameters were estimated using 2004-2009 occurrence data for France and the model was then validated using 2013 occurrence data. Several scenarios were tested: human-mediated dispersal was present or absent and control intensity varied. Then, the species' spread in coming years was simulated (from 2013 to 2020)., Despite some uncertainty on the value of the parameters, this model is relatively robust. Human-mediated dispersal may not be necessarily responsible for the hornet's rapid range expansion; the species could spread rapidly on its own. It is likely that to date, an average of 30-40% of detected nests have been destroyed each year., Increasing the percentage of destroyed nests from 30 to 60% could reduce the species' spread by 17% and its nest density by 29%. If 95% of nests are destroyed, the species' spread and nest density could decline by 43% and 53%, respectively., Synthesis and applications. The mathematical model developed in this study shows that human-mediated dispersal of the invasive yellow-legged hornet may not be the only factor explaining the hornet's rapid range expansion and that controlling this invasive pest is still possible. Therefore, there is an urgent need to reduce self-mediated dispersal and to intensify and improve control measures to diminish the species' impact and prevent its further spread. Control measures could combine the mechanical removal and destruction of individuals or infested materials with biological control techniques. [ABSTRACT FROM AUTHOR]

Effects of recent climate change have already been detected in many species, and, in particular, in insects. The present paper reviews the key impacts of global warming on insect development and dispersal. The effects of climate change appear to be much more complex than a simple linear response to an average increase in temperature. They can differ between seasons and bioclimatic regions. Earlier flight periods, enhanced winter survival and acceleration of development rates are the major insect responses. Differential response of insects and hosts to warming up might also lead to disruption of their phenological synchrony, but adaptive genetic processes are likely to quickly restore this synchrony. In a number of cases, warming results in removing or relocating the barriers that limit present species' ranges. It is also likely to facilitate the establishment and spread of invasive alien species. Finally, knowledge gaps are identified and future research interests are suggested. [ABSTRACT FROM AUTHOR]

Many defoliating forest lepidopterans cause predictable periodic deforestation. Several of these species exhibit geographical variation in both the strength of periodic behavior and the frequency of cycles. The mathematical models used to describe the population dynamics of such species commonly predict that gradual variation in the underlying ecological mechanisms may lead to punctuated (subharmonic) variation in outbreak cycles through period-doubling cascades. Gypsy moth, Lymantria dispar, in its recently established range in the northeastern United States may represent an unusually clear natural manifestation of this phenomenon. In this study we introduce a new statistical spatial-smoothing method for estimating outbreak periodicity from space-time defoliation data collected with spatial error. The method statistically confirms the existence of subharmonic variation in cyclicity among different forest types. Some xeric forest types exhibit a statistical 4-5 year period in outbreak dynamics, some mesic forest types a 9-10 year period, and some intermediate forest types a dominant 9-10 year period with a 4-5 year subdominant superharmonic. We then use a theoretical model involving gypsy moth, pathogens, and predators to investigate the possible role of geographical variationin generalist predator populations as the cause of this variation in dynamics. The model predicts that the period of gypsy moth oscillations should be positively associated with predator carrying capacity and that variation in the carrying capacity provides a parsimonious explanation of previous reports of geographical variation in gypsy moth periodicity. Furthermore, a two-patch spatial extension of the model shows that, in the presence of spatial coupling, subharmonic attractors can coexist whereas nonharmonic attractors (i.e., where the cycle lengths are not integer multiples of one another) cannot. [ABSTRACT FROM AUTHOR]

The article presents a study on the impact of the dispersal and Allee effects to the invasion pests specifically the Lymantria dispar, a gyspsy moth, in North America. It intends to identify the life history traits that promote invasion because of the increasing number of biological invasions. The dispersal, mating and growth of gypsy moth was simulated to be able to evaluate the spread of the species.

Allee effects have been applied historically in efforts to understand the low-density population dynamics of rare and endangered species. Many biological invasions likewise experience the phenomenon of decreasing population growth rates at low population densities because most founding populations of introduced nonnative species occur at low densities. In range expansion of established species, the initial colonizers of habitat beyond the organism’s current range are usually at low density, and thus could be subject to Allee dynamics. There has been consistent empirical and theoretical evidence demonstrating, and in some cases quantifying, the role of Allee dynamics in the gypsy moth, Lymantria dispar (L.), invasion of North America. In this review, we examine the potential causes of the Allee effect in the gypsy moth and highlight the importance of mate-finding failure as a primary mechanism behind an Allee effect, while the degree to which generalist predators induce an Allee effect remains unclear. We then explore the role of Allee effects in the establishment and spread dynamics of the gypsy moth system, which conceptually could serve as a model system for understanding how Allee effects manifest themselves in the dynamics of biological invasions. [ABSTRACT FROM AUTHOR]

A fundamental question in biological conservation and invasion biology is why do some populations go extinct? Allee effects, notably those caused by mate location failure, are potentially key factors leading to the extinction of sparse populations. Several previous studies have focused on the inability of males and females to locate each other in space when populations are at low densities but here we investigate the effects of differences in the timing of male and female maturation on mating success. We develop a generalized model to clarify the role of protandry (the appearance of males before female emergence) and variability in adult maturation times. We show that temporal asynchrony can substantially reduce the probability of successful mating. We then apply this generalized model to estimate mating success in invading populations of the gypsy moth in North America in relation to local climate and its associated seasonality. Considerable geographic heterogeneity was observed in simulated mating success and this variability was not correlated with previous evaluations of bioclimatic requirements and habitat suitability. Furthermore, we found that the generalized model of temporal asynchrony provided reliable predictions and that detailed modeling of gypsy moth development was not necessary. [ABSTRACT FROM AUTHOR]

Aim We investigated whether climate change has affected the potential feeding activity of a winter active larva, the pine processionary moth (PPM), Thaumetopoea pityocampa L., and whether it may explain its range expansion. Location The study area is France and, at a smaller scale, the Paris Basin. Methods We used a statistical model derived from Huchon and Démolin [1970 Revue Forestière Française (special issue: La lutte biologique en forêt), 220–234] to test whether their model, updated with climate change, could explain the observed range expansion. Since Battisti and colleagues have recently shown that climate could affect survival of the PPM through its effect on feeding activity, we also developed a mechanistic model based on larval feeding requirements (night air temperature above 0 °C and temperature inside the nest above 9 °C on the preceding day). We reconstructed the geographical distribution of feeding activity and we compared the resulting change with the PPM range expansion. Results The statistical model did not successfully predict the observed expansion but the mechanistic model showed considerable change in the feeding activity of the PPM. In the Paris Basin, the PPM border coincided with a zone unfavourable for feeding activity in the period 1992–96. Feeding conditions became more favourable in the period 2001–04, and the PPM succeeded in crossing this zone. Over larger temporal and spatial scales improved feeding conditions in the north-western part of France were forecast by the mechanistic model. Main conclusions (1) The range distribution of the PPM in the Paris Basin is no longer limited by unfavourable feeding conditions. (2) The pattern of range expansion of the PPM is now governed mainly by its dispersal capabilities and host tree distribution. (3) At the country scale, this approach gives an approximate prediction of the potential distribution of the PPM, though the model may not be reliable in mountainous regions. [ABSTRACT FROM AUTHOR]

The article analyzes the expansion of geographic range in the pine processionary moth, Thaumetopoea pityocampa, caused by the increased winter temperatures. The winter pine processionary moth, Thaumetopoea pityocampa , provides a classic example of an insect that is active in the winter, usually as a larva in the third and fourth instar. Latitudinal and altitudinal expansion areas for experimental investigations were selected in the Paris Basin, south of Paris, France, and in Venosta/Vinschgau Valley near Boizano/Bozen, northern Italy, respectively. In both France and Italy, natural gradients were utilized to simulate temperature conditions experienced by the insect, as spatial analogues for climate change. Larval activity of T. pityocampa at temperature around 0 degree Celsius was also observed by Fitz-gerald and Bias (2003), who monitored the movement events under field conditions and showed that, in induced colonies, larvae leave the nest with the onset of darkness and come back in the morning as long as the temperature is around 0 degree Celsius. Temperature conditions during both the precold period and the cold period influenced growth and survival of T. pityocampa at the expansion sites. The results indicate that while temperature during the pre-cold period significantly affects colony survival, it may have an even more important role during the cold period.