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A contribution to the explanation of the larch bud moth cycle, the polymorphic fitness hypothesis
Abstract
Studies of fluctuating insect populations generally discuss the regulating processes at high insect numbers, but very rarely why a cycling population at low densities switches immediately from the declining phase to the increasing phase of the cycle. A long-term study of the larch bud moth (Zeiraphera diniana Gn) has suggested that the key to recovery is assortative mating of specific phenotypes. Z. diniana exhibits distinct host races living either on the deciduous larch or evergreen pines and spruces. As an adaptation to its hosts Z. diniana is necessarily rather polymorphic in its life history parameters, i.e. developmental rate, fertility and survival. Apart from the direct association of the larva with the host tree, the colouration of the mature larva provides the only readily apparent trait by which the host race can be recognised; the larch form is black and the pine or spruce form has a light orange head capsule, anal plate and body colour. Evidence that frequencies of the colour morphs on larch regularly change from an intermediate colour type to black during the increasing phase of the cycle suggests that the combination of traits, such as earliest larval emergence, largest body size and homozygosity, characteristic of the black morph, constitutes the inherent driving force of population increase.
... One of the most intensively investigated and probably best-documentedcyclic behaviourin ecological systemsare regularlarch budmoth (Zeiraphera diniana [Gn.]; LBM) mass outbreaks (Berryman 1996, Baltensweiler et al. 2008, which occur every 8-10 years in travelling wavesacross most of the European Alps (Baltensweiler 1993). Periodical mass outbreaks of this foliage-feeding insect are mainlyrestricted to itshost species, the European larch (Larix decidua Mill.). ...
... Otherstudies assessedthe mechanisms ofthe varying LBM density including the drivers of itscyclicity(e.g. Fischlin & Baltensweiler 1979, Anderson & May 1980, Baltensweiler 1993, Turchin et al. 2003,as well as the synchronicity of outbreak events across the Alps (e.g. Bjørnstad et al. 2002, Johnson et al. 2004, Price et al. 2006). ...
... Cycles of the LBM mass infestation are intensively investigated in the core habitat of its host species European larch (cf. Baltensweiler 1993, Baltensweiler & Rubli 1999, Bjørnstad et al. 2002, Johnson et al. 2004, Price et al. 2006, Esper et al. 2007, Baltensweiler et al. 2008, Büntgen et al. 2009, Johnson et al. 2010, Battipaglia et al. 2014). However, all these studies focus on the main LBM outbreak region, although the distribution range of larch exceeds these well-known hotspot areas. ...
... One of the most intensively investigated and probably best-documentedcyclic behaviourin ecological systemsare regularlarch budmoth (Zeiraphera diniana [Gn.]; LBM) mass outbreaks (Berryman 1996, Baltensweiler et al. 2008), which occur every 8-10 years in travelling wavesacross most of the European Alps (Baltensweiler 1993). Periodical mass outbreaks of this foliage-feeding insect are mainlyrestricted to itshost species, the European larch (Larix decidua Mill.). ...
... Otherstudies assessedthe mechanisms ofthe varying LBM density including the drivers of itscyclicity(e.g. Fischlin & Baltensweiler 1979, Anderson & May 1980, Baltensweiler 1993, Turchin et al. 2003),as well as the synchronicity of outbreak events across the Alps (e.g. Bjørnstad et al. 2002, Johnson et al. 2004, Price et al. 2006). ...
... Cycles of the LBM mass infestation are intensively investigated in the core habitat of its host species European larch (cf. Baltensweiler 1993, Baltensweiler & Rubli 1999, Bjørnstad et al. 2002, Johnson et al. 2004, Price et al. 2006, Esper et al. 2007, Baltensweiler et al. 2008, Büntgen et al. 2009, Johnson et al. 2010, Battipaglia et al. 2014). However, all these studies focus on the main LBM outbreak region, although the distribution range of larch exceeds these well-known hotspot areas. ...
... One of the most intensively investigated and probably best-documentedcyclic behaviourin ecological systemsare regularlarch budmoth (Zeiraphera diniana [Gn.]; LBM) mass outbreaks (Berryman 1996, Baltensweiler et al. 2008, which occur every 8-10 years in travelling wavesacross most of the European Alps (Baltensweiler 1993). Periodical mass outbreaks of this foliage-feeding insect are mainlyrestricted to itshost species, the European larch (Larix decidua Mill.). ...
... Otherstudies assessedthe mechanisms ofthe varying LBM density including the drivers of itscyclicity(e.g. Fischlin & Baltensweiler 1979, Anderson & May 1980, Baltensweiler 1993, Turchin et al. 2003,as well as the synchronicity of outbreak events across the Alps (e.g. Bjørnstad et al. 2002, Johnson et al. 2004, Price et al. 2006). ...
... Cycles of the LBM mass infestation are intensively investigated in the core habitat of its host species European larch (cf. Baltensweiler 1993, Baltensweiler & Rubli 1999, Bjørnstad et al. 2002, Johnson et al. 2004, Price et al. 2006, Baltensweiler et al. 2008, Johnson et al. 2010, Battipaglia et al. 2014). However, all these studies focus on the main LBM outbreak region, although the distribution range of larch exceeds these well-known hotspot areas. ...
This publication is a result of the 14th TRACE conference (Tree Rings in Archaeology, Climatology and Ecology) organized by the Department Physical, Chemical and Natural Systems of the University Pablo de Olavide (UPO) and the Association for Tree-ring Research (ATR), in collaboration with Pyrenean Institute of Ecology-Spanish National Research Council (IPE-CSIC), University of Barcelona (UB), Forest and Wood Technology Research Centre (CETEMAS) and University of Valladolid (UVa). The TRACE 2015 conference was held on May 20-23, 2015 for the first time in the Iberian Peninsula, in Sevilla, Spain.
... The species consists of host-associated forms feeding on larch (Larix), pine (Pinus) and spruce (Picea). The population biology of the larch budmoth has been studied in great detail for over 30 years by Baltensweiler et al. (reviewed by Baltensweiler et a!., 1977;Baltensweiler, 1993). This moth has highly cyclical population dynamics above 1000 m in larch forests of the Alps: every 8-10 years there are outbreaks during which populations peak at 100,000-fold greater densities than during the subsequent crash. ...
... The differences between the dark and pale forms of larvae on larch are similar to the differences between larvae on larch and pine; on larch, larvae are predominately dark, on pine they are pale. This suggests that host-associated differentiation contributes to the cycles of genetic variation on larch, and may even be involved in population regulation (Baltensweiler, 1993). ...
... In spite of these differences, the two forms have always been considered members of the same species because: (i) they interbreed freely in the laboratory, with no distortion of sex ratio in the progeny (Table 1; Baltensweiler, 1977); (ii) studies of variation in female pheromone blend, variable response of males to these pheromones and the intermediacy of F1 hybrids suggests that introgression should be common in the wild (Priesner, 1979;Day, 1984;Guerin et al., 1984;Baltensweiler & Priesner, 1988); (iii) their populations fluctuate in synchrony; and (iv) probable hybrid forms are often found on larch Baltensweiler, 1993). ...
Eleven larch- and pine-feeding populations of the larch budmoth were studied in Western Europe using 24 allozyme loci. Hierarchical F-statistics between larch and pine forms (FST≍0.065) were much greater than those between localities within larch (FST≍0.002) and within pine (FST≍0.026), even when sympatric host-associated populations were considered. Analysis of Nei's genetic distance produced similar results, and a upgma tree of all populations consistently clustered samples from the same hosts together. Three loci, autosomal Pgm and Mdh-s and sex-linked Idh-s, were the most important loci involved in differences between the two forms. Previously considered to be conspecific, it is now clear that the larch and pine biotypes of Z. diniana are either host races (sensu Diehl & Bush, 1984) or good sympatric species which hybridize rarely. Regardless of taxonomic status, the distribution of larch and pine in the Pleistocene, phenological differences between the two hosts, together with the great vagility of Z. diniana, an outbreak pest, suggest that sympatric or parapatric differentiation is at least as likely as allopatric divergence.
... population density (LBM census since 1949) and AGC/ EY sequence of larch from site 12. LBM data from Baltensweiler (1993 b). The LE-values are set upon the AGC/EY values! ...
... Since, after the pupation of the larvae, a successful refoliation of the larch trees was possible, assimilation was partially restored and, thus, enough nutrients could be stored to facilitate a growth recovery in the following year. According to the data of the LBM population census (Baltensweiler 1993 b) the maximum larval density of this cycle was average. Case 2 (1972 outbreak). ...
... North or Middle Grisons, Bernese Uplands), was impracticable . The highly consistent cyclicity of the LBM fluctuations (Baltensweiler 1993 b) and the particular tree-ring patterns consequently were the only grounds for an out- break. ...
Outbreaks of the larch budmoth (LBM) (Zeiraphera diniana) recur cyclically approximately every 7 to 10 years in subalpine larch-cembran pine and montane to subalpine larch-Norway
spruce forests of the relatively dry valleys of the European Alps. By dendroecologically analyzing increment cores from 570
host (European larch –Larix decidua) and non-host trees (cembran pine –Pinus cembra, Norway spruce –Picea abies) through the use of skeleton plots, at least 57 (59) outbreaks could be reconstructed in the optimum Upper Engadine Valley
(suboptimum Goms Valley), Switzerland, during the time period 1503 (1472) to 1990. The average interval between initial years
of successive outbreaks was 8.58 (8.95) years, SD 1.66 (2.13) years. Over the centuries spatial shifts of LBM activity between
the two study areas occurred, probably due to climatic changes. Clear, site-specific differences in LBM attack could only
be found in the suboptimum area where high-lying (>1800 m) and/or south-facing stands were infested most. LBM-afflicted trees
proved to be unsuitable for climate reconstructions because the impact of the persistently recurring outbreaks on tree growth
is dominant. In order to provide sufficient information for a detailed ecological interpretation of the course of an outbreak,
latewood widths and/or densities have to be analyzed in addition to the ring-widths.
... These mechanisms include behavioural changes in population quality (Baltensweiler, 1993b), host-pathogen interactions (Anderson & May, 1980), induced host defences (Fischlin & Baltensweiler, 1979) and host-parasitoid interactions (Turchin et al., 2003). Larvae of LBM feed on the foliage of sub-alpine larch, which occurs extensively in a forest belt across the European Alps (Baltensweiler et al., 1977). ...
... The timing of late summer re-foliation, which theoretically could account for a positive relationship between summer warmth and LBM outbreaks, has been assessed recently (Kress et al., 2009). Such a relationship would also reflect the previously postulated effect of cold season temperatures on LBM diapause and, subsequently, population growth (Baltensweiler, 1993b). The development of first-stage larvae in spring is limited by the energy provided at the time of oviposition in the previous summer. ...
... The development of first-stage larvae in spring is limited by the energy provided at the time of oviposition in the previous summer. Optimal conditions for first instars are long and cold winters with more than 120 d below 2°C (Baltensweiler, 1993b). If summer temperatures are high, development from egg to moth is terminated sooner, leading to an earlier diapause with fewer frost days, resulting in an elevated egg mortality plus increased larval mortality when hatching before host needle flushing (Baltensweiler et al., 1977). ...
Knowledge of the persistence of regular larch budmoth outbreaks is limited in space and time. Although dendrochronological methods have been used to reconstruct insect outbreaks, their presence may be obscured by climatic influences. More than 5000 tree-ring series from 70 larch host and 73 spruce nonhost sites within the European Alps and Tatra Mountains were compiled. Site-specific assessment of growth-climate responses and the application of six larch budmoth detection methods considering host, nonhost and instrumental time-series revealed spatiotemporal patterns of insect defoliation across the Alpine arc. Annual maps of reconstructed defoliation showed historical persistence of cyclic outbreaks at the site level, recurring c. every 8-9 yr. Larch budmoth outbreaks occurred independently of rising temperatures from the Little Ice Age until recent warmth. Although no collapse in outbreak periodicity was recorded at the local scale, synchronized Alpine-wide defoliation has ceased during recent decades. Our study demonstrates the persistence of recurring insect outbreaks during AD 1700-2000 and emphasizes that a widely distributed tree-ring network and novel analysis methods can contribute towards an understanding of the changes in outbreak amplitude, synchrony and climate dependence.
... Morphologically, these host races are distinguishable only at the fifth instar; larvae on larch are black and those on pine are light yellow-orange. This color polymorphism in the larvae varies during population cycles (Baltensweiler et al., 1977;Baltensweiler, 1993). ...
... By contrast, LBM larvae exploiting cembran pine must cope with higher amounts of toxic oleoresins (Norin, 1972). It has been suggested that the more generalist cembran pine race surviving on evergreens represents the original form because of its more adaptive characteristics like slower rate of post-diapause development, significantly smaller adult size, and greater survival under nutritional stress (Baltensweiler, 1993;Khomentovsky et al., 1997). Seasonal and annual variation in relative host abundance and suitability, a common occurrence in nature (Boughton, 2000), tends to oppose the increase in host choice. ...
... This results in a less suitable resource for the larch race at regular 8-year intervals. At this point in the cycle, however, the proportion of light morphs capable of exploiting cembran pine (Baltensweiler, 1993) is highest on larch (Baltensweiler, unpublished). Since our data suggest that the larch host race does perceive chemostimuli from cembran pine, we have to assume the host plants may still function as rendezvous sites for both host races, but whether olfactory perception serves to permit utilization of the alternate resource is an open question. ...
The larch bud moth (LBM) Zeiraphera diniana Guenée causes defoliation on larch in the Alps at 8- to 10-year intervals, after which populations crash. There are two LBM host races, one on larch and the other on cembran pine. These host races are morphologically indistinguishable as adults but they differ genetically in larval color types. Furthermore, females of each host race produce distinct pheromone blends and show oviposition preferences for their respective hosts. It is not clear to what extent host choice contributes to assortative mating in the LBM. Here, we compare the olfactory sensitivities of the two host races to the odors of fresh foliage of the host plants using the electroantennogram (EAG) technique, and the responses of the two host races to volatiles collected from the two host plants as analyzed by gas-chromatography-linked antennographic detection (GC-EAD). Both sexes of the larch and cembran host races show the same EAG responses to vapors of fresh larch and cembran pine foliage. Fifteen plant volatiles identified as chemostimuli by GC-EAD from larch and cembran pine odors elicited the same antennogram responses from the two host races. However, the GC-EAD analyses indicate that the number and quantity of chemostimuli emanating from each host plant is different. It is, therefore, most probably the array of olfactory receptors responding to the bouquet of volatiles unique to each host plant that underlies the host preferences of the two races. What remains open is the extent to which the similarity of the olfactory systems may contribute to cross-attraction. The fact that LBM individuals with intermediate characteristics between the two host races exist, suggests that olfactory perception does not hinder gene flow and contributes to sustained genetic diversity within the species Z. diniana.
... The larch budmoth Zeiraphera diniana Guenée (Lepidoptera: Tortricidae) inhabits coniferous forests throughout the Palaearctic, where it feeds on larch (Larix spp.), pine (Pinus cembra) and spruce (Picea spp.) (Berryman, 1986). Larch-feeding populations in the French and Swiss Alps undergo large fluctuations in density (up to 10 5 fold over a ~9 year period, Baltensweiler 1993) and are a model system for the study of population biology (e.g. Bjørnstad et al. 2002). ...
... Fifth instar larch-race larvae are black while pine-race larvae are predominantly yellowgreen (Baltensweiler 1993), and components of female pheromones are released in different ratios by each race. The differences in host preference, hatch time, larval colour and pheromone composition are heritable, and there is also divergence in allozyme frequency and at AFLP loci (Emelianov et al. 1995(Emelianov et al. , 2003(Emelianov et al. , 2004. ...
Larch and pine associated populations of Zeiraphera diniana (Lepidoptera: Tortricidae) differ in a number of heritable traits, but pheromone-mediated cross-attraction occurs between them in the wild. Using a quartet mate choice design (one male and one female of each type per cage) we estimate that, following cross-attraction by pheromones, the subsequent probability of hybridization is approximately 28%. We also examined molecular data, and were unable to distinguish between the races on the basis of 695bp of mitochondrial COI, tRNA-leucine, and COII gene sequence. Both results support earlier field studies suggesting that larch- and pine-feeding populations are host races that hybridize at an appreciable level in the wild. The shared mitochondrial haplotypes we observed are also consistent with ongoing and successful gene flow between the two host races.
... The larch budmoth Zeiraphera diniana Guenée (Lepidoptera: Tortricidae) inhabits coniferous forests throughout the Palaearctic, where it feeds on larch (Larix spp.), pine (Pinus cembra) and spruce (Picea spp.) (Berryman, 1986). Larch-feeding populations in the French and Swiss Alps undergo large fluctuations in density (up to 10 5 fold over a ~9 year period, Baltensweiler 1993) and are a model system for the study of population biology (e.g. Bjørnstad et al. 2002). ...
... Fifth instar larch-race larvae are black while pine-race larvae are predominantly yellowgreen (Baltensweiler 1993), and components of female pheromones are released in different ratios by each race. The differences in host preference, hatch time, larval colour and pheromone composition are heritable, and there is also divergence in allozyme frequency and at AFLP loci (Emelianov et al. 1995(Emelianov et al. , 2003(Emelianov et al. , 2004. ...
Larch and pine associated populations of Zeiraphera diniana (Lepidoptera: Tortricidae) differ in a number of heritable traits, but pheromone-mediated cross-attraction occurs between them in the wild. Using a quartet mate choice design (one male and one female of each type per cage) we estimate that, following cross-attraction by pheromones, the subsequent probability of hybridization is approximately 28%. We also examined molecular data, and were unable to distinguish between the races on the basis of 695bp of mitochondrial COI, tRNA-leucine, and COII gene sequence. Both results support earlier field studies suggesting that larch- and pine-feeding populations are host races that hybridize at an appreciable level in the wild. The shared mitochondrial haplotypes we observed are also consistent with ongoing and successful gene flow between the two host races. Keywords biotypes, gene flow, host races, hybridization, mitochondrial DNA, introgression, mate choice
... I). Baltensweiler (1977Baltensweiler ( , 1993a proposed the following explanation for this pattern: During popula tion increases, the dark morphs become more abundant because they have faster development and higher survival than the light morphs. During popu lation collapses, the dark morphs decrease faster than the light morphs, because they rely primarily on larch for food, and the quality of larch foliage is reduced by defoliation. ...
... Once the effects of defoliation on host quality dissipate, dark morphs begin increasing faster than light ones, and the cycle repeats itself. Baltensweiler (1993a) argued that this polymorphism plays a key role in the LBM cycle. In particular, he suggested that it helps explain why low LBM populations switch immediately from the decline to the increase phase. ...
The population dynamics of the larch budmoth (LBM), Zeiraphera diniana, in the Swiss Alps are perhaps the best example of periodic oscillations in ecology (figure 7.1). These oscillations are characterized by a remarkably regular periodicity, and by an enormous range of densities experienced during a typical cycle (about 100,000-fold difference between peak and trough numbers). Furthermore, nonlinear time series analysis of LBM data (e.g., Turchin 1990, Turchin and Taylor 1992) indicates that LBM oscillations are definitely generated by a second-order dynamical process (in other words, there is a strong delayed density dependence—see also chapter 1). Analysis of time series data on LBM dynamics from five valleys in the Alps suggests that around 90% of variance in Rt is explained by the phenomenological time series model employing lagged LBM densities, R, =f(Ni-1,Ni-2,) (Turchin 2002). As discussed in the influential review by Baltensweiler and Fischlin (1988) about a decade ago, ecological theory suggests a number of candidate mechanisms that can produce the type of dynamics observed in the LBM (see also chapter 1). Baltensweiler and Fischlin concluded that changes in food quality induced by previous budmoth feeding was the most plausible explanation for the population cycles. During the last decade, the issue of larch budmoth oscillations was periodically revisited by various population ecologists looking for general insights about insect population cycles (e.g., Royama 1977, Bowers et al. 1993, Ginzburg and Taneyhill 1994, Den Boer and Reddingius 1996, Hunter and Dwyer 1998, Berryman 1999). These authors generally concurred with the view that budmoth cycles are driven by the interaction with food quality. A recent reanalysis of the rich data set on budmoth population ecology collected by Swiss researchers over a period of several decades, however, suggested that the role of parasitism is underappreciated (Turchin et al. 2002). Before focusing on the roles of food quality and parasitism in LBM dynamics, we briefly review the status of other hypotheses that were discussed in the literature on LBM cycles. First, the natural history of the LBM-larch system is such that food quantity is an unlikely factor to explain LBM oscillations.
... Population density on larch oscillates in an eight-to 10-year cycle; at their peak, populations may be 10 5 times denser than during a crash. What triggers a population outbreak is still not fully understood, but causes of population crashes likely involve delayed effects of defoliation on the quality of larch foliage in subsequent years (Baltensweiler 1993). Populations on pine appear more stable (Baltensweiler et al. 1977), although few data exist. ...
... Thus, the direction of gene flow could depend on the phase of the larch cycle. Periodic introgression of genes for pale larval color from the pine race into the larch race, whose mature larvae are normally black, may explain an observed synchrony between the population cycles and pale phenotypes on larch (Baltensweiler 1993). We are currently investigating evidence for gene flow and its periodicity using additional molecular markers. ...
The likelihood of sympatric speciation is enhanced when assortative mating is a by-product of adaptation to different habitats. Pleiotropy of this kind is recognized as important in parasites that use their hosts as a long-range cue for finding mates, but is generally assumed to have limited applicability for most other organisms. In the larch budmoth, Zeiraphera diniana (Lepidoptera: Tortricidae), sympatric host races feed on larch or pine. Zeiraphera diniana females attract males (call) by releasing host-independent long-range pheromones. Pheromone composition differs strongly between host races, but we show in an experimental field study that cross-attraction can occur at a rate of 0.03-0.38. Cross-attraction to larch females increases when they call from neighborhoods (8-m radius) rich in pine or from pine trees. Cross-attraction to pine females similarly increases when calling from neighborhoods rich in larch, but there is no significant effect of calling substrate. Males, as well as females, of this species preferentially alight on their own host, and in neighborhoods where their own host is common. This effect of tree species and host neighborhood on assortative mating is therefore due, at least in part, to the numbers of males of each host race present within approximately 200 m2 surrounding the female. This proximity effect is enhanced by the clumped distributions of the hosts themselves. Host chemistry might also affect pheromone production and/or response directly, but we have evidence neither for nor against this. This work provides empirical evidence that host adaptation has a pleiotropic effect on assortative mating in a species with host-independent long-range mating signals. Sympatric speciation via pleiotropy between ecological traits and assortative mating may thus be more common than generally supposed: Clumped resource distributions and habitat choice by adults are widespread.
... Several different mechanisms have been proposed to explain oscillations seen in LBM populations. These theories have invoked behavioural changes in population quality (Baltensweiler 1993b), budmoth/disease interactions (Anderson & May 1980), induced host defences (Fischlin & Baltensweiler 1979) and host/parasitoid interactions (Turchin et al. 2003) as causes of periodic outbreaks. Virtually all of these mechanisms have made some assumption of delayed density-dependent effects. ...
... parasitoids, predators and diseases) trophic levels and the unprecedented change in climate could thereby affect LBM populations indirectly, in addition to the direct mechanisms outlined above. Although LBM populations have not reached defoliating levels in most parts of the Alps since the early 1980s, they have attained sub-defoliating peak densities during this period (Baltensweiler 1993b;Baltensweiler & Rubli 1999). This suggests that the change in LBM population dynamics has been a diminishing of oscillation amplitude, but not necessarily an alteration of the period. ...
The long-term history of Zeiraphera diniana Gn. (the larch budmoth, LBM) outbreaks was reconstructed from tree rings of host subalpine larch in the European Alps. This record was derived from 47513 maximum latewood density measurements, and highlights the impact of contemporary climate change on ecological disturbance regimes. With over 1000 generations represented, this is the longest annually resolved record of herbivore population dynamics, and our analysis demonstrates that remarkably regular LBM fluctuations persisted over the past 1173 years with population peaks averaging every 9.3 years. These regular abundance oscillations recurred until 1981, with the absence of peak events during recent decades. Comparison with an annually resolved, millennium-long temperature reconstruction representative for the European Alps (r=0.72, correlation with instrumental data) demonstrates that regular insect population cycles continued despite major climatic changes related to warming during medieval times and cooling during the Little Ice Age. The late twentieth century absence of LBM outbreaks, however, corresponds to a period of regional warmth that is exceptional with respect to the last 1000+ years, suggesting vulnerability of an otherwise stable ecological system in a warming environment.
... Larch budmoth, larch tortrix Range: Europe, China, Korea, Japan, Russia, N. America (Baltensweiler et al. 1977;Baltensweiler 1993aBaltensweiler , 1993bBjørnstad et al. 2002;Peltonen et al. 2002;Dormont et al. 2006;Esper et al. 2007;Kress et al. 2009;Iyengar et al. 2016 (Daniel and Myers 1995;Parry 1995;Parry et al. 1997;Rothman and Roland 1998;Cooke and Roland 2000;Parry et al. 2001;Cooke and Roland 2003;Parry et al. 2003;Wood et al. 2009;Trudeau et al. 2010;Wood et al. 2010;Charbonneau et al. 2012;Cooke et al. 2012;Moulinier et al. 2013;Hughes et al. 2015;Uelmen et al. 2016 ...
One of the most significant categories of insect that cause damage to trees are the defoliators. While many orders of insects feed on tree foliage, in this chapter we will focus on Lepidoptera, as there are so many Lepidopteran larvae (caterpillars) that are known for their extensive tree damage. In this chapter we review the impact of foliage feeders on forest trees and stand composition, and the ways in which densities of these species or the defoliation they cause are monitored. We do not cover insects attacking ornamental trees in the landscape, nor do we cover insects feeding exclusively on foliage tips or buds.
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Darwin argued a role for sexual selection in the evolution of male sensory structures, including insect antennae, the strength of which will depend upon the importance of early arrival at receptive females. There is remarkable variation in the nature and degree of sexual dimorphism in moth antennae, with males of some species having spectacular, feathery antennae. Although it is widely assumed that these elaborate structures provide greater sensitivity to chemical signals (sex pheromones), the factors underlying the interspecific diversity in male antennal structure and size are poorly understood. Because male antennal morphology may be affected by several female life–history traits, including flight ability, we conducted a phylogenetic comparative analysis to test how these traits are linked, using data from 93 species of moths across 11 superfamilies. Our results reveal that elaborate antennae in males have evolved more frequently in species where females are monandrous. Further, female loss of flight ability evolved more frequently in species where males have elaborate antennae. These results suggest that elaborate antennae have evolved in response to more intense male competition, arising from female monandry, and that the evolution of elaborate antennae in males has, in turn, shaped the evolution of female flightlessness.
... The cyclic nature of LBM outbreaks is well known in the core habitat of its host species, European larch (Baltensweiler, 1993;Baltensweiler & Rubli, 1999;Bjørnstad et al., 2002;Johnson et al., 2004Johnson et al., , 2010Price et al., 2006;Esper et al., 2007;Baltensweiler et al., 2008;Büntgen et al., 2009;Battipaglia et al., 2014). All of these studies focus on the main LBM outbreak region, even though the range of larch extends well beyond these well-known outbreak areas (Fig. 1). ...
1 Outbreaks of the larch budmoth (LBM) in the European Alps are among the most documented population cycles and their historical occurrence has been reconstructed over 1200 years.
2 Causes and consequences of cyclic LBM outbreaks are poorly understood and little is known about populations near the margin of the host’s distribution range.
3 In the present study, we quantify historical LBM outbreaks and associated growth reductions in host trees (European larch). Tree-ring data collected from 18 sites between approximately 500 and 1700m a.s.l. in the Northern pre-Alps are compared with data from the Western Alps and Tatra Mountains, as well as with nonhost Norway spruce.
4 Highly synchronized host and nonhost growth in the Northern pre-Alps shows that periodic LBM outbreaks are largely absent near the distributional limit of larch. By contrast, growth patterns in the Western Alps LBM core region are indicative of LBM events. Although climatic conditions in the Northern pre-Alps and Tatra Mountains would allow LBM outbreaks, low host plant abundance is likely the key driver for the absence of cyclic outbreaks in these regions.
5 The results obtained in the present study suggest that, in addition to the climatic conditions, host-species abundance is critically important for the occurrence of periodic LBM outbreaks and the determination of the respective outbreak range.
... The dynamics of insect populations vary considerably among species with some exhibiting equilibrium dynamics, others having regular cycles, or chaotic patterns (Bjornstad and Grenfell 2001). Cyclic population behavior has been reported for many species of foliage-feeding Lepidoptera (Berryman 1996), including the larch budmoth (LBM: Zeiraphera diniana Gn.), which exhibits particularly regular cycles of 8-10 years, with recurrent high population densities causing extensive forest defoliation in the subalpine zone of the European Alps (Baltensweiler 1993a;Baltensweiler et al. 1977). These defoliation episodes alter ring width formation of host larch trees and dendrochronological methods have been used to reconstruct the timing of historical outbreaks over the past 1,200 years (Büntgen et al. 2009;Esper et al. 2007;Rolland et al. 2001;Weber 1997). ...
Key message
The absence of larch budmoth outbreaks and subsequent
consequences on tree rings together with a distinct climate–growth relationship enhance the dendroclimatic potential of larch ring width data from the Tatra Mountains.
Abstract
Regular population oscillations are generally considered to arise from trophic interactions, though it is unclear how such cycles are affected by biotic and abiotic factors. Cyclic outbreaks of the larch budmoth (LBM; Zeiraphera diniana), perhaps the most prominent example of periodic insect population dynamics, leave distinct “fingerprints” in the annual rings of host trees, and have been reconstructed over 1,200 years in the European Alps. Although LBM individuals are known to exist in other regions, it is unclear whether recurrent mass outbreaks historically occurred elsewhere. Here, we present new larch (Larix decidua) host and pine (Pinus cembra) non-host chronologies from the Slovakian Tatra that comprise 323 ring width samples dating back to 1612 AD. May–June and May–July temperatures control larch and pine growth (r
1951–2011 = 0.63 and 0.57; p < 0.001), respectively. LBM outbreak-induced defoliation patterns and subsequent ring width reductions were absent over the past three centuries, during which larch (host) and pine (non-host) growth was significantly synchronized (r
1725–2012 = 0.48; p < 0.001). Spatially limited host forests of overall low stand densities along the northwestern Carpathian arc together with a relatively warm climate envelope are most likely responsible for the absence of cyclic LBM outbreaks. Tree-ring chronologies from these ecotones, free of pulsed disruptions, therefore, represent unique paleoclimatic archives ideal for reconstructing interannual to multi-centennial variations in Eastern European summer temperature.
... This holistic approach notwithstanding several authors from the late 1980s and early 1990s continue to think of the problems in terms of genetic processes as ultimate factors maintaining cycles. This can be seen from several treatises dealing with microtines (Desjardins et al. 1986, Boonstra & Boag 1987, Tamarin & Sheridan 1987, Spears & Clarke 1988) and tetraonids (Moss & Watson 1991, Watson et al. 1994) as well as certain insects such as lepidopterans and moths (Mitter & Schneider 1987, Baltensweiler 1993. ...
The polymorphic-behaviour hypothesis alias Chitty hypothesis has been a very characteristic element of the evolving theoretical population ecology during the second half of the 20th cen-tury. This paper considers the origins and fates, among the scientific community, of the ideas upon intrinsic regulation of population fluctuations through balanced, especially behavioural, poly-morphisms. The final formulation — presumably quite independently in separate quarters — of such ideas into hypotheses identical as to their concep-tual contents has been examined. The maturation of the hypothesis into a conceptually unambigu-ous form advanced very differently in step, how-ever, in separate quarters. This, in turn, interest-ingly disclosed how such a difference can be based on differences in the interests or training of the pertinent authors in the special fields of theoreti-cal population biology. The vicissitudes of the concept in the writings of several eminent popu-lation ecologists before and after the well-known extensive period of painstaking efforts to test the polymorphic-behaviour hypothesis have also been surveyed. It appears that ideas upon genetic mechanisms associated with cycles have contin-ued in the treatises of population biologists through the 1980s until the present. This can be interpreted as a first rate indication indeed of how difficult it really is to imagine a population strong-ly fluctuating with cycles that would not possess any kind of intrinsic strategies specifically adopted for readiness to resist alternatively repeating stresses of different origins.
... Thus parasitoids could make up for the absent insect Áhost plant interaction and therefore account to some extent for the synchrony between the cycles observed on the two hosts. In view of the many competing theories and models to explain the LBM cycle on larch (Baltensweiler and Fischlin 1988, Baltensweiler 1993a, Ginzburg and Taneyhill 1994, Berryman 1996, Baltensweiler and Rubli 1999), it would be mere speculation to search for an explanation of the cycle on pine with the current knowledge. Nevertheless, it is tempting to associate the synchrony of the two cycles with a genetic interaction of the two host races. ...
Population cycles of many forest-defoliating insects often show synchronous fluctuations at both intra-specific (spatial synchrony) and inter-specific levels. However, population dynamics of different host-associated biotypes of the same species, such as those of the larch budmoth (LBM), Zeiraphera diniana (Lepidoptera: Tortricidae), have never been compared. This species causes extensive defoliation of larch forests every 8 to 9 years in the Alps, but it consists of two genetically-differentiated host races, the first one developing on European larch, Larix decidua, and the other one developing on Swiss stone pine, Pinus cembra. The dynamics of Zeiraphera populations have been extensively studied on larch, whereas little is known about larval density and possible population fluctuations on sympatric pines. A larval census on Swiss stone pine was conducted in the Swiss Alps intermittently between 1958 to 2004 and in the French Alps from 1992 to 2004. Population density of Zeiraphera on pine varied up to 5000-fold and showed periodic oscillations, with five peaks in Switzerland and one in France. Because the feeding activity of the pine race is restricted to the elongating shoot of the current year, no conspicuous defoliation of pine trees was noted during years of high larval densities. Zeiraphera populations on pine oscillated in significant synchrony with larch-associated populations, and peak densities were observed either the same year or shifted by±one year. Our results did not allow any explanation for cyclic fluctuations of LBM on pine, but the synchrony with the larch race's cycle suggests that studies on genetics as well as on parasitism should be intensified.
... The population cycles of LBM are affected by numerous interactions with lower (e.g., host plants, prey) and/or higher trophic levels (e.g., predators, diseases; Berryman 1996). Several mechanisms have been put forward to explain LBM oscillations, including behavioral changes in population quality (Baltensweiler 1993a), budmoth–disease interactions (Anderson and May 1980), induced host defenses (Fischlin 1982), and host– parasitoid interactions (Turchin et al. 2003). However, it remains unclear how these cycles are modulated by climatic influences (Esper et al. 2007). ...
Larch budmoth (LBM, Zeiraphera diniana Gn.) outbreaks cause discernable physical alteration of cell growth in tree rings of host subalpine larch (Larix decidua Mill.) in the European Alps. However, it is not clear if these outbreaks also impact isotopic signatures in tree-ring cellulose, thereby masking climatic signals. We compared LBM outbreak events in stable carbon and oxygen isotope chronologies of larch and their corresponding tree-ring widths from two high-elevation sites (1800-2200 m a.s.l.) in the Swiss Alps for the period AD 1900-2004 against isotope data obtained from non-host spruce (Picea abies). At each site, two age classes of tree individuals (150-250 and 450-550 years old) were sampled. Inclusion of the latter age class enabled one chronology to be extended back to AD 1650, and a comparison with long-term monthly resolved temperature data. Within the constraints of this local study, we found that: (1) isotopic ratios in tree rings of larch provide a strong and consistent climatic signal of temperature; (2) at all sites the isotope signatures were not disturbed by LBM outbreaks, as shown, for example, by exceptionally high significant correlations between non-host spruce and host larch chronologies; (3) below-average July to August temperatures and LBM defoliation events have been coupled for more than three centuries. Dampening of Alps-wide LBM cyclicity since the 1980s and the coincidence of recently absent cool summers in the European Alps reinforce the assumption of a strong coherence between summer temperatures and LBM defoliation events. Our results demonstrate that stable isotopes in tree-ring cellulose of larch are an excellent climate proxy enabling the analysis of climate-driven changes of LBM cycles in the long term.
... These host races cross freely in the laboratory and are commonly found in sympatry in nature (Emelianov et al. 1995, 2001, 2003). Despite probable hybridization, races remain strongly differentiated at genetic marker loci (Emelianov et al. 1995), as well as in traits involved in host utilization (Bovey & Maksymov 1959; Day 1984; Emelianov et al. 2003), morphology (particularly coloration of larvae; see Baltensweiler 1993) and mate choice via differentiated female pheromones (Baltensweiler et al. 1978; Priesner & Baltensweiler 1987; Emelianov et al. 2001). If these racial differences are maintained by selection in the face of continuous gene exchange, we expect an excess of differences between races on chromosomes under divergent selection, and a deficit of divergence elsewhere in the genome. ...
Ecological divergence in the face of gene flow has recently become implicated as a potentially important cause of speciation and adaptive radiation. Here, we develop a genomic approach to test for divergent selection in sympatric host races of the larch budmoth Zeiraphera diniana (Lepidoptera: Tortricidae). We analysed hundreds of amplified fragment length polymorphism markers in 92 individuals in sympatric and allopatric populations, and in two backcross broods used to map the markers to individual chromosomes. The results directly confirm the existence of natural hybridization and demonstrate strong heterogeneity between chromosomes in terms of molecular divergence between host races (the average level of divergence was FST = 0.216). However, genomic heterogeneity was not found when we analysed divergence between geographically separated populations of the same host race. We conclude that the variance of the level of sympatric divergence among chromosomes is the footprint of divergent selection acting on a few linkage groups, combined with appreciable gene flow that homogenizes between-race variation at the remaining linkage groups. These results, coupled with other recent multilocus analyses of sister species pairs, demonstrate that selection-driven sympatric phase of genetic divergence in the presence of gene flow is a likely feature of speciation.
This project investigates the host race status of larch and pine associated Zeiraphera diniana populations via studies of actual gene flow, hybrid fitness, and mitochondrial DNA. The formation of host races - genetically distinct, host associated biotypes connected by gene flow - is an essential step in sympatric speciation via host shift, and their existence provides strong support for this theory. However, the identification of these forms has been complicated by the use of multiple host race definitions that are often ambigous in an empirical context. Therefore a new, empirically based definition is developed in and employed throughout this thesis. A novel requirement of this definition is that at least 1% actual gene flow (movement of genes via hybridisation) occurs between the races each generation, and leads to backcrossing. Other requirements include sympatry, genetic differentiation, and host fidelity. Previous studies have shown that larch and pine associated Z. diniana meet most host race criteria, but little was known about the level of gene flow between the races. The main findings presented here are that the level of actual gene flow (the movement of genes via hybridisation) between the biotypes is approximately 2.4% per generation, that backcrossing is likely, and therefore that they are indeed host races. The extent of actual gene flow was estimated from the combined probabilities of long range, pheromone-mediated cross attraction (measured in the field), and hybridisation in competitive situations (measured in the laboratory). Evidence of backcrossing was obtained from several experiments. Proportions of non-hybrid, hybrid, and backcross broods hatching, and surviving to final larval instars in the laboratory did not differ. Hybrid females were able to obtain matings with larch males in competitive conditions, and hybrids of both sexes are fertile. In addition, there was no evidence of mitochondrial DNA differentiation between the forms across approximately 800bp of mitochondrial cytochrome oxidase I (partial), tRNA-leucine, and cytochrome oxidase II (partial).
While populations of all animals fluctuate in density, some cycle on a regular basis. Forest Lepidoptera, snowshoe hares, and red grouse cycle with an approximate 10-year periodicity, while voles and lemmings in some areas, cycle with a 3–5-year periodicitiy. Cyclical dynamics can be synchronized over tens to hundreds of kilometers. Predators and social behavior are the primary causes of small mammal cycles and parasitoids and/or disease are the dominant drivers of Forest Lepidoptera cycles. Red grouse cycles are associated with aggressive behavior of males and infection by a nematode. What causes the variation in peak and trough densities between cycles, the transition from decline to increase phase, and synchronizes fluctuations remains a mystery.
We investigated the factors responsible for changes in abundance of the spruce bud moth, Zeiraphera canadensis Mut. and Free. (Lepidoptera: Tortricidae) in one unmanaged and several managed (i.e., planted) young white spruce, Picea glauca (Moench.) Voss (Pinaceae), stands in northern New Brunswick, Canada. Spruce bud moth densities declined when one stand closed (branches from neighbouring trees overlapped) and had already declined in another similarly aged closed stand, but remained high on 8- to 22-year-old open-grown white spruce. Both the intrageneration survival rate and the egg-to-moth ratios increased when population densities increased, and generally decreased, although the egg-to-moth ratio fluctuated, during the population decline in a managed stand. Increases in intrageneration survival rates of spruce bud moth on 5- to 10-year-old trees were due to increased larval or pupal survival. Crown closure explained 76 and 81% of the variability in larval and intrageneration survival, respectively, in four managed stands. The strong inverse relationship between larval survival and degree of crown closure resulted in statistically significant but spurious relationships between larval survival and larval density and between larval survival and tree age. A reduction in larval survival occurring as degree of crown closure increased was the most important factor influencing decreases in intrageneration survival at the beginning of population decline. Increases in the egg-to-moth ratio during the population increase, and decrease during population decline, suggested that dispersal behaviour and (or) realized fecundity of females also contributed to annual changes in population.
An outbreak of the larch bud moth (Zeiraphera diniana Guenée) occurred from 1988 to 1993 on Pinus pumila [(Pall.) Regel] on Kamchatka Peninsula while the sympatric Larix gmelinii [(Rupr.) Litv.] remained unattacked. This first major outbreak of Z. diniana ever observed and reported on an evergreen host in Siberia and North East Asia is discussed in the larger context of its population dynamics throughout the Palaearctic. The complex interactions between site-, host plant- and insect-characteristics in conjunction with climatic release allows us to explain this unique event in a conventional manner:bull the eggs survive the extremely cold winter temperatures on dwarf pines underneath the snowbull the slow developing light colour morph, which is adapted to the phenology of evergreens, benefits from the mesoclimate close to the goundbull it was temporarily favoured by the significantly warmer spring and summer seasons during the outbreak 1988–1991. The occurrence of the pine-feeding Z. diniana in North East Asia supports the hypothesis that the host-associated genetic divergence might have evolved sympatrically.
The range of the moth Zeiraphera diniana Guénée and the regions where high population densities are infrequent and unpredictable are thought to be determined by high temperatures during egg pre-diapause. Exposure of eggs to incubation temperatures known to be optimal for Z. diniana elsewhere resulted in a pre-diapause mortality of 13% which corresponds to known rates of egg mortality in British forests. Evidence suggests that high temperature and its duration are both important determinants of pre-diapause egg mortality which, if experienced in forest conditions, may prevent populations from reaching outbreak levels. Historical records of outbreaks were associated with lower than average August temperature. However, high temperatures on their own are unlikely to determine the range of the insect in Britain since a high proportion of eggs survives extremes; more than 70% of British eggs survived 24 h exposure to a temperature of 30°C. Variations in egg mortality among families of moths suggests a genetic basis for differences in thermal tolerance. Furthermore, there may be selection for thermally-tolerant eggs in British forest environments and this could be connected with other forms of genetic differentiation in budmoth populations.
Pathogens have long been known to play a major role in the population dynamics of many important forest insects. For many
irruptive species, outbreaks are terminated by baculovirus epizootics that cause dramatic declines of host density. Such epizootics
are well known for Lepidoptera such as gypsy moth, Lymantria dispar; Douglas fir tussock moth, Orgyia pseudotsugata; nun moth, L. monacha; pine beauty moth, Panolis flammea; forest tent caterpillar, Malacosoma disstria; western tent caterpillar, M. californicum pluviale, and the European larch budmoth, Zeiraphera diniana. Similar epizootics are known in sawflies (Hymenoptera: Diprionidae) including the European pine sawfly, Neodiprion sertifer; the European spruce sawfly, Gilpinia hercyniae and the red-headed pine sawfly, Neodiprion lecontei.
In the Alps, larch (Larix decidua Mill.) forests show periodic discolouration due to larch budmoth (LBM) outbreaks (Zeiraphera diniana Gune, Lepidoptera: Tortricidae). Tree defoliation causes severe reductions in radial growth, visible in tree rings. This paper aims at reconstructing LBM outbreak history, and critically examining the potential for using dendrochronological data by comparing tree-ring estimates with insect surveys. The occurrence of LBM outbreaks was investigated using 249 cores from larch growing near the timberline in three regions of the French Alps (Brianonnais, Maurienne, and Tarentaise). Years with an abrupt decrease in radial growth (-40%) were considered as negative pointer years reflecting the potential impact of LBM. The comparison with three non-host conifers (Norway spruce, stone and mountain pines) permitted us to distinguish growth reductions in larch due to climatic effects from those due to defoliation by LBM. The dendrochronological data were matched with information reporting conspicuous discolouration in old forestry reports or recovered from systematic field observations. Twenty-two outbreaks are discernible within the period 1800-1983. A peak reduction in larch growth occurred at intervals of 8.86ǃ.01 years in the following years: 1801, 1811, 1820, 1830, 1838, 1846, 1857, 1867, 1875, 1884, 1892, 1901, 1909, 1918, 1926, 1936, 1945, 1953, 1963, 1972, 1980, and 1987. Our objective method based on ring measurements and comparison with non-host trees was compared with qualitative techniques based on the visual detection of conspicuous latewood anomalies. Larch in the Brianonnais (which experiences a continental climate) are infested first, whereas the Tarentaise region exhibits a much weaker impact of LBM. Complete tree recovery was observable 3 years after outbreak peaks.
Why do organisms become extremely abundant one year and then seem to disappear a few years later? Why do population outbreaks in particular species happen more or less regularly in certain locations, but only irregularly (or never at all) in other locations? Complex population dynamics have fascinated biologists for decades. By bringing together mathematical models, statistical analyses, and field experiments, this book offers a comprehensive new synthesis of the theory of population oscillations. Peter Turchin first reviews the conceptual tools that ecologists use to investigate population oscillations, introducing population modeling and the statistical analysis of time series data. He then provides an in-depth discussion of several case studies--including the larch budmoth, southern pine beetle, red grouse, voles and lemmings, snowshoe hare, and ungulates--to develop a new analysis of the mechanisms that drive population oscillations in nature. Through such work, the author argues, ecologists can develop general laws of population dynamics that will help turn ecology into a truly quantitative and predictive science. Complex Population Dynamics integrates theoretical and empirical studies into a major new synthesis of current knowledge about population dynamics. It is also a pioneering work that sets the course for ecology's future as a predictive science.
The existence of a continuous array of sympatric biotypes - from polymorphisms, through ecological or host races with increasing reproductive isolation, to good species - can provide strong evidence for a continuous route to sympatric speciation via natural selection. Host races in plant-feeding insects, in particular, have often been used as evidence for the probability of sympatric speciation. Here, we provide verifiable criteria to distinguish host races from other biotypes: in brief, host races are genetically differentiated, sympatric populations of parasites that use different hosts and between which there is appreciable gene flow. We recognize host races as kinds of species that regularly exchange genes with other species at a rate of more than ca. 1% per generation, rather than as fundamentally distinct taxa. Host races provide a convenient, although admittedly somewhat arbitrary intermediate stage along the speciation continuum. They are a heuristic device to aid in evaluating the probability of speciation by natural selection, particularly in sympatry. Speciation is thereby envisaged as having two phases: (i) the evolution of host races from within polymorphic, panmictic populations; and (ii) further reduction of gene flow between host races until the diverging populations can become generally accepted as species. We apply this criterion to 21 putative host race systems. Of these, only three are unambiguously classified as host races, but a further eight are strong candidates that merely lack accurate information on rates of hybridization or gene flow. Thus, over one-half of the cases that we review are probably or certainly host races, under our definition. Our review of the data favours the idea of sympatric speciation via host shift for three major reasons: (i) the evolution of assortative mating as a pleiotropic by-product of adaptation to a new host seems likely, even in cases where mating occurs away from the host; (ii) stable genetic differences in half of the cases attest to the power of natural selection to maintain multilocus polymorphisms with substantial linkage disequilibrium, in spite of probable gene flow; and (iii) this linkage disequilibrium should permit additional host adaptation, leading to further reproductive isolation via pleiotropy, and also provides conditions suitable for adaptive evolution of mate choice (reinforcement) to cause still further reductions in gene flow. Current data are too sparse to rule out a cryptic discontinuity in the apparently stable sympatric route from host-associated polymorphism to host-associated species, but such a hiatus seems unlikely on present evidence. Finally, we discuss applications of an understanding of host races in conservation and in managing adaptation by pests to control strategies, including those involving biological control or transgenic parasite-resistant plants.
Has species diversity in parasites evolved as a by-product of adaptive diversification driven by competition for limited resources? Or is it a result of gradual genetic drift in isolation? One can move closer to answering these questions by evaluating the ubiquity of host switching, the key stage of adaptive diversification. Studies dealing with evolutionary role of host switching suggest that this process is extremely common in the wild, thus pointing at adaptive nature of parasite species diversity. However, most of these studies are focused on the evidence that may or may not have emerged as a consequence of host switching, - an approach potentially associated with a degree of uncertainty. After an overview of the data I am making an attempt to get a clearer view on host switching by focusing on factors that cause this phenomenon. In particular, I review theoretical work and field observations in order to identify the type of genetic host-use variance and the type of dispersal that underpin host switching. I show that host switching is likely to require generalist modifier alleles which increase the host range of individual genotypes and is likely to be promoted by wave-like patterns of dispersal. Both factors appear to be common in parasites. I conclude by outlining key areas for future research, including: (i) direct testing for divergence with gene flow, the main "footprint" of adaptive speciation; (ii) investigating the association between demography, dispersal potential and the potential to colonise novel habitats; and (iii) determining the genetic mechanisms underpinning host range variance in parasites.
During the late 1940s, immediately after World War II, the lush green forests of the Engadine Valley, high in the Swiss Alps, turned an ugly red-brown in the midst of the tourist season. This was due to a spectacular outbreak of the larch budmoth, Zeiraphera
diniana Guenée (Lepidoptera: Tortricidae). Preparing for a revival of the tourist industry, and having the new insecticide DDT at hand, it seemed only appropriate that the tourist office urge the forest service to control the pest. This was the beginning of what was to become a 34-year study of the population dynamics of the larch budmoth (Fig. 1).
Examines how genetic change affects the size and dynamics of insect populations, distinguishing between short-term effects (reversible changes associated with individual outbreak episodes) and long-term ones (shifts in average abundance or outbreak patterns occasioned by directional evolutionary change). Evidence for a significant contribution to the origin of outbreaks from genetic change involves: 1) the presence of heritable differences between the outbreak population and its presumed progenitor, and 2) an absence of associated environmental changes sufficient in themselves to explain the outbreak. This is illustrated by reference to outbreaks of greenbug Schizaphis graminum on Sorghum, hessian fly Mayetiola destructor on wheat Triticum aestivum, codling moth Cydia pomonella on walnut Juglans regia, and tobacco budworm Heliothis virescens on cotton Gossypium hirsutum. -P.J.Jarvis
Phenotypic plasticity is discussed in the sense of environmentally induced adaptive behavioural, physiological and/or ecological variation among individuals of a population. Some theoretical issues are addressed, particularly questions of whether all life history traits are subjected to environmentally induced variation; how phenotypic plasticity is maintained; the relationship between phenotypic plasticity and insect outbreaks; and the extent to which species may be categorised as phenotypically plastic based on the capacity of the environment to support population growth. Illustrations are provided of the mechanisms that can trigger the expression of phenotypic plasticity. Species that populate intermittently favourable and unpredictable environments tend to exhibit phenotypic plasticity, are able to adapt to existence at various densities, and are thus potential outbreak species. Variability in population density depends not only on the reproductive potential of a species but also on the length of time over which that potential is expressed. -P.J.Jarvis
A study of pheromone polymorphism in Zeiraphera diniana Gn. (Lep., Tortricidae) 2. Pheromonal response types in F1 hybrids between three host races
Field-collected moths of the larch (LF), cembran pine (AF) and spruce (FiF) host races of Z. diniana were cross-mated in 22 reciprocal pairings LF × AF and LF × FiF and the F1 male progeny evaluated for pheromonal response polymorphism as reflected by the frequency of different “response types” occurring in each individual pairing. These types were based on the electrophysiological (EAG) efficacy of pheromone components (E)-9-dodecenyl acetate vs. (E)-11-tetradecenyl acetate as allocated to 9 half decade “response classes”, such as in studies on Z. diniana wild populations (part 1 of this series). The larval colour morphs of these same individuals were also noted.
The parental LF were taken from a subalpine “pure E11–14:Ac” pheromone type population characterized by a response relationship E9–12:Ac/E11–14:Ac of 1/≥100 in all test males. The AF parents were from a subalpine population living in close sympatry with a cyclic fluctuating LF (mixed larch - cembran pine stand) and showing a range of E9–12:Ac male response types, from ≥100/1 to 10/1. For both the LF≥ × AF♂ and the AF♀ × LF♂ pairings the F1 data (193 test males) revealed the dominance of the AF (E9–12:Ac) over the LF (E11–14:Ac) pheromonal response though response polymorphism was generally greater in the F1 compared to the parental AF. However, this male polymorphism differed greatly between individual pairings: some revealing only type ≥100/1 and 30/1 males; others, the full range from type ≥100/1 to type 1/1 males; and one pairing, even a few reciprocal response types 1/3 to 1/≥100 (tables ′1a, b). These results indicate considerable genetic heterogeneity for the AF parents, probably due to partial LF introgression into this population prior to our experiments. Colour morphs of the F1 males were intermediate to light, similar to the parent AF. There was no apparent relationship between a particular parental colour morph, either LF or AF, and the frequency of different morphotypes or pheromonal response types occurring in the respective F1 progeny. A few F2 pairings (LF♀/AF♂) × (LF♀/AF♂) revealed ≥ 100/1 and 30/1 type males some of which showed the dark LF colour morph, not present among the F1 hybrids.
Reciprocal crossings LF × FiF were made using FiF parents collected in 1977 from the large incipient outbreak of Z. diniana on Norway spruce in northeastern Bohemia. Samples from this parent FiF population showed only response types ≥ 100/1 and 30/1, combined with intermediate to dark colour morphs. The F1 hybrid data (224 test males) indicated a low but distinct shift towards more intermediate response types (range, ≥ 100/1 to 3/1), for both the LF♂ × FiF♀ and FiF♂ × LF♀ pairings (tables 2a, b). The response type frequencies were not significantly different between individual pairings, thus indicating genetic homogeneity for both the LF and FiF parent populations. Colour morph frequencies were not altered for the F1 hybrids compared to the parent FiF. Backcrosses LF♂ × (LF/FiF)♀ and (LF/FiF)♂ × LF♀ showed the expected split into E9–12:Ac and E11–14:Ac response type males.
The results permit an interpretation of some phenomena observed with Z. diniana wild populations, described in part 1 of this series. Thus, the high portion of E9–12:Ac response type males with light to intermediate colour morphs, found in LF populations of mixed larch - cembran pine stands at a certain stage of the population cycle, can be tentatively referred to the progeny of LF females mated with AF males. The analogous conclusion should apply to other LF populations with respect to introgression of other E9–12:Ac type host races. However, potential backcrosses or F2 hybrid males present in a wild population cannot be safely distinguished from the native population, neither by response type nor colour morph, and no prediction as to the further fate of such interpopulational hybrids can be made from the present data.
Falter der Lärchenform (LF), Arvenform (AF) und Fichtenform (FiF) von Z. diniana wurden in 22 reziproken Paarungen LF × AF und LF × FiF gekreuzt und für jede Paarung der Polymorphismus der Pheromonantwort der F1-Männchen bestimmt. Die Männchen wurden dazu anhand der elektrophysiologischen Wirksamkeit der Pheromonkomponenten (E)-9-Dodecenylacetat gegenüber (E)-11-Tetradecenylacetat einer Skala von 9 halbdekadisch abgestuften „Reaktionstypen” zugeordnet, wie bei der Untersuchung von Z. diniana-Wildpopulationen (Teil 1 dieser Serie). Der Farbtypus des letzten Raupenstadiums (L5-Morphotyp) wurde ebenfalls wieder notiert.
Die LF-Elterntiere entstammten einer subalpinen Population des „reinen E11-14:Ac-Typs”, charakterisiert durch ein Antwortverhältnis E9-12:Ac / E11-14:Ac von 1/≥100 bei allen Testmännchen. Die AF-Eltern wurden einer Population entnommen, die in enger Sympatrie mit einer zyklisch fluktuierenden LF lebt (subalpiner Lärchen-Arvenmischwald) und zum Testzeitpunkt E9-12:Ac-Reaktionstypen des Bereichs ≥100/1 bis 10/1 aufwies. Unter den F1-Nachkommen (193 Testmännchen) dominierte zwar in beiden Paarungsrichtungen, LF♀ × AF♂ und AF♀ × LF♂, die E9–12:Ac-Antwort der AF durchwegs über die E11-14:Ac-Antwort der LF, der Polymorphismus der Antworten war für die F1 jedoch insgesamt größer als in der elterlichen AF. Dabei differierte die Bandbreite von Antworten allerdings stark zwischen den einzelnen Paarungen (Tab. 1a, b): In einigen Paarungen traten nur Reaktionstypen ≥100/1 und 30/1 auf, in anderen ein breites Spektrum von Typ ≥100/1 bis 1/1; eine Paarung lieferte neben derartigen E9-12:Ac-Antworttypen auch solche des E11-14:Ac-Typs. Diese Ergebnisse weisen auf eine starke genetische Heterogeneität der elterlichen AF, vermutlich als Folge teilweiser LF-Introgression in diese Population vor unseren Kreuzungsexperimenten. Die Farbtypen der F1-Männchen waren intermediär bis hell, wie in der elterlichen AF. Zwischen dem Farbmorphotyp eines Elternteils (LF oder AF) und der Häufigkeit verschiedener Morphotypen oder Pheromon-Reaktionstypen in der betreffenden F1-Nachzucht war keine Beziehung erkennbar. Einige F2-Paarungen (LF♀/AF♂) × (LF♀/AF♂) lieferten Falter der Reaktionstypen ≥100/1 und 30/1, von denen einige den unter den F1-Hybriden nicht vertretenen dunklen LF-Farbmorphotyp aufwiesen.
Die FiF-Elterntiere wurden 1977 einer starken Population der Fichtenwälder Nordostböhmens entnommen, die sich zu dieser Zeit in Progradation befand. Stichproben dieser Elterngeneration enthielten nur intermediäre bis dunkle Farbtypen, verbunden mit Pheromonantworten des Typs ≥100/1 oder 30/1. Die F1-Meßergebnisse (224 Testmännchen; Tab. 2a, b) lassen für beide Paarungsrichtungen eine Verschiebung in Richtung mehr intermediärer Pheromonantworten (Bandbreite, ≥100/1 bis 3/1) erkennen. Die Verteilung dieser Antworttypen differierte dabei nicht wesentlich zwischen den individuellen Paarungen, ein Hinweis auf genetische Homogeneität sowohl der LF-wie der FiF-Elternpopulation. Die Häufigkeiten von Farbmorphotypen waren für die F1 im Vergleich zur elterlichen FiF nicht verändert. Rückkreuzungen LF♀ × (LF/FiF)♂ und (LF/FiF)♂ × LF♂ zeigten die erwartete Aufspaltung in E9-12:Ac- und E11-14:Ac-Antwort-typen.
Die Ergebnisse erlauben eine Interpretation einiger in Teil 1 dieser Serie beschriebener Beobachtungen an Z. diniana-Wildpopulationen. So würde der hohe Anteil von E9-12:Ac-Antworttypen mit hellem bis intermediärem Farbtyp, wie er etwa in LF-Populationen subalpiner Lärchen-Arvenmischwälder in bestimmten Phasen des Populationszykius gefunden wird, den F1-Nachkommen aus Paarungen von LF-Weibchen mit AF-Männchen entsprechen. Die analoge Deutung gilt für andere LF-Populationen in Hinblick auf Einkreuzung anderer Wirtsrassen des E9-12:Ac-Typs. Dagegen lassen sich in einer Wildpopulation eventuell vorhandene F2- und Rückkreuzungshybriden weder am L5-Farbtyp noch Pheromon-Reaktionstyp sicher erkennen, auch können zum weiteren Schicksal von Z. diniana-Rassenhybriden gegenwärtig keine Aussagen gemacht werden.
In the course of a population cycle of the Grey Larch Bud Moth it was observed that the proportions of larval colourtypes change. This was believed to be attributable to density induced changes in the food quality of the host plant during the cycle. Selected representatives of naturally occurring larval populations were reared in controlled laboratory conditions on freshly cut larch shoots and on a semi‐synthetic food medium. Larval mortality on the laboratory culture media was shown to be different and the proportions of colour forms in the resultant and corresponding groups also differed. These experiments suggest higher mortality of early‐instar larvae of the dark colourtype under food‐stress conditions and a resulting change in colourtype composition of the next generation. Further to this there is an indication that effective true‐breeding is more likely under food‐stress conditions. The results support the hypothesis for a changing population fitness with regard to food‐stress conditions throughout a gradation cycle.
Zusammenfassung
VERÄNDERUNGEN DER ANTEILE LARVALER FARBTYPEN DER LÄRCHENFORM VON ZEIRAPHERA DINIANA ALS FOLGE VON ZWEI VERSCHIEDENEN FUTTERARTEN
Im Verlaufe einer Massenvermehrung des Grauen Lärchenwicklers verändern sich die relativen Anteile der larvalen Farbtypen. Es wurde vermutet, daß diese Erscheinung mit der dichtebedingten Schädigung der Wirtspflanze und einer nachfolgenden Änderung der Nahrungsqualität gekoppelt sei. Zwecks Abklärung dieser Hypothese wählte man aus Freilandpopulationen Individuen bestimmter Farbtypen aus und züchtete die F 1 ‐Generation auf frischen Kurztrieben der Lärche und auf einem semi‐synthetischen Nährmedium. Es konnte gezeigt werden, daß nicht nur die Larval‐Mortalitäten auf den beiden Nährmedien voneinander abweichen, sondern daß auch die Anteile der Farbtypen in den entsprechenden Gruppen verschieden sind. Die Versuche lassen schließen, daß unter Nahrungsstress die dunklen Farbtypen während der frühen Larvenstadien eine höhere Mortalität erleiden und somit die Selektion zu einem Wechsel in der Zusammensetzung der Farbtypen der folgenden Generation beiträgt. Zusätzlich beobachtet man aber, daß unter Nahrungsstress die Übereinstimmung zwischen dem elterlichen Farbtyp und jenem der Nachkommen größer ist. Somit bekräftigen die Resultate die Annahme einer variablen Leistungsfähigkeit der Population in bezug auf Nahrungsstress während einer Massenvermehrung.
A study of pheromone polymorphism in Zeiraphera diniana Gn. (Lep., Tortricidae). 3. Specificity of attraction to synthetic pheromone sources by different male response types from two host races
The specificity of male attraction to synthetic sex lures was studied for Z. diniana wild populations representing a range of different pheromone response types. Standard series of 35 different lures, made up of varying combinations of pheromone components (E)-9-dodecenyl acetate and (E)-11-tetra-decenyl acetate, were exposed at sites of allopatric and sympatric occurrence of the larch form (LF) and cembran pine form (AF) host races and catch rates were compared among lure sources and test sites. In addition, samples of captured males were analysed for their pheromone response types as based on the response relationship E9–12:Ac/E11–14:Ac in electroantennogram (EAG) measurements, such as in studies of Z. diniana wild populations and their F1 hybrids (parts 1 and 2 of this series).
The AF samples analysed contained only E9–12:Ac response types ≥100/1 to 10/1; and the LF samples, only E11–14:Ac response types 1/≥100 to 1/10. No individuals representing a more intermediate EAG type, 3/1 to 1/3, were found during these tests. The trapping results indicate a highly selective response by the two host races to the single chemicals, the E9–12:Ac sources attracting only AF and the E11–14:Ac sources only LF males. Traps baited with compound mixtures, on the other hand, usually contained individuals from both host populations. The AF attraction response to the E9–12:Ac lure component was not markedly affected by admixture of up to the 10 fold amount of E11–14:Ac and was only partially reduced by even higher E11–14:Ac additions. In contrast, the admixture of an equal amount of E9–12:Ac to E11–14:Ac significantly reduced the attraction of LF males, and higher amounts of E9–12:Ac almost prevented any attraction. Individuals representing the three AF response types, ≥100/1, 30/1 and 10/1, were found on the same lure sources; for the LF response types 1/≥100, 1/30 and 1/10 an analogous statement is not yet possible. There was no evidence for a synergistic response to both lure components by either host race.
The present data permit, when combined with the reported pheromone compositions of individual AF and LF females, some inferences as to female luring specificities towards males of the two host races. Thus, LF males could be expected to show only slight attraction to AF females, whereas the mixed pheromone signals of some LF females, which may contain small amounts of E9–12:Ac in addition to E11–14:Ac, are likely to attract AF males as well. The observed introgression of AF criteria into some LF populations, reported previously, may thus be due to pheromonal attraction of AF males to females of this other host race.
Für Z. diniana-Männchen unterschiedlichen Pheromon-Reaktionstyps wurde die Spezifität des Freilandanflugs an synthetische Lockstoffquellen untersucht. Diese enthielten die Weibchenpheromone (E)-9-Dodecenylacetat (E9–12:Ac) und (E)-11-Tetradecenylacetat (E11–14:Ac) als Einzelsubstanz oder in binären Mischungen verschiedener Mengenrelation und Gesamtdosis. Dieselbe Serie von 35 Ködervarianten war vergleichend an Standorten allopatrischen und sympatrischen Vorkommens der Lärchenform- und Arvenform-Wirtsrasse (LF, AF) exponiert. Für jede Testpopulation wurde einerseits die Verteilung des Gesamtanflugs an die 35 Varianten bewertet, andererseits anhand von Stichproben gefangener Männchen die Anflugspezifität der verschiedenen Reaktionstypen. Letztere basieren auf der Wirksamkeitsrelation E9–12:Ac/ E11–14:Ac im Elektroantennogramm-Test (EAG) und entsprechen der Typisierung männlicher Falter bei der Untersuchung von Z. diniana-Wildpopulationen und ihrer F1-Rassenhybriden (Teil 1 und 2 dieser Studie).
Die untersuchten Stichproben angelockter Falter der AF-Population enthielten nur E9–12:Ac-Reaktionstypen des Bereichs ≥100/1 bis 10/1; und die LF-Stichproben, E11–14:Ac-Reaktionstypen des Bereichs 1/≥100 bis 1/10. Stärker intermediäre Reaktionstypen, 3/1 bis 1/3, waren in den Stichproben nicht vertreten. Nach den vorliegenden Ergebnissen locken die Reinsubstanzen, E9–12:Ac bzw. E11–14:Ac, offenbar streng selektiv nur AF- bzw. nur LF-Männchen an. Dagegen fanden sich an den meisten Mischködern Falter beider Wirtsrassen. Der AF-Anflug an den E9–12:Ac-Anteil der Köder war selbst bei Zusatz einer 10fach höheren E11–14:Ac-Menge noch nicht wesentlich reduziert, erst die 100fache E11–14:Ac-Menge verminderte den Anflug dieser Wirtsrasse. Dagegen wurde der LF-Anflug an den E11–14:Ac-Anteil der Köder bereits durch eine gleich hohe E9–12:Ac- Menge deutlich, durch noch höhere E9–12:Ac-Zusätze stark reduziert. Die AF-Reaktionstypen 30/1 und 10/1 fanden sich an denselben Ködervarianten wie der vorherrschende Typ ≥100/1; für die LF-Reaktionstypen 1/≥100, 1/30 und 1/10 erlaubt die geringere Stichprobe noch keine analoge Feststellung. Für keine der beiden Wirtsrassen lassen die Ergebnisse eine eindeutig synergistische Reaktion auf beide Köderkomponenten erkennen.
Bezogen auf Literaturangaben zur Zusammensetzung der Pheromone individueller AF- und LF-Weibchen, erlauben die jetzigen Daten erste Rückschlüsse auf deren Lockspezifität gegenüber Männchen der beiden Wirtsrassen. Danach sollten LF-Männchen an AF-Weibchen allenfalls schwach angelockt werden, während die Mischsignale von LF-Weibchen, selbst wenn sie nur kleine Anteile an E9–12:Ac enthalten, auch für AF-Männchen attraktiv sein sollten. Die in vorausgegangenen Untersuchungen aufgezeigte Introgression von AF-Merkmalen in sympatrische LF-Populationen ließe sich damit auf pheromongesteuerte Anflüge von AF-Männchen auch an Weibchen der anderen Wirtsrasse zurückführen.
Negative feed-back by competition for food and space, and by cyclic induced changes in the nutritional base as regulatory principles in the population dynamics of the larch budmoth Zeiraphera diniana (Guenée). At high density of the larvae of Z. diniana on larch trees in subalpine forests, intraspecific competition causes an increase in mortality of larvae and pupae, as well as reduction of pupal weight and fecundity of the emerging moths. The negative effects become more pronounced by shortage of food at population levels leading to complete defoliation of the larch trees. Defoliation in turn activates specific mechanisms in the trees, which lead to late and slow sprouting of the needles in spring (weak coincidence), short needles (reduced mass of nutritional base), and reduced quality of the needles (elevated contents of fibres and reduced protein contents). Thus the succeeding bud moth populations are depressed by negative feed-back. The cyclic numeric fluctuations with a periodicity of 8 to 10 years, which are characteristic of populations of Z. diniana in its optimum area, may thus be regarded as the expression of an autoregulating life system in which the species multiplies for 4–5 generations under favorable conditions and thus, transgressing the carrying capacity, changes the nutritional base in such a way that environmental resistance to the species becomes high for another 4 generations.
Im Hinblick auf eine Erklärung der zyklischen Massenwechsel des Lärchenwicklers Z. diniana in den subalpinen Arven-Lärchenwäldern wurde der Einfluß der Populationsdichte, besonders aber der Nahrungsgrundlage auf Vitalität und Fekundität des Schädlings untersucht. Die Untersuchungen führten zu folgenden Ergebnissen:
Diese Mechanismen steigern die Raupenmortalität im 1. und 2. Nachschadensjahr auf 80–90% und bewirken weiterhin eine stark reduzierte Fekundität.
Analysis of the sex gland content ofZeiraphera diniana females and field responses of males to synthetic compounds show that the sympatrically occurring food specialists on various coniferous hosts use different blends ofE-9-dodecenyl acetate andE-11-tetradecenyl acetate as sex pheromones.
The larch bud-moth cycle has been observed in the sub-alpine larch-cembran pine forests 16 times since 1850. Infestation is easily recognized by the characteristic red-brown discoloration of the larch crowns due to the wasteful feeding of the bud moth larvae. The heaviest defoliation recurs at intervals of 8.470.27 (SE) years, and the larval density per kilogram of larch branches varies more than 10000-fold over four or five generations. The basic regulatory mechanism for this cycle is the induced change in food quality for the two or more subsequent larval generations. Defoliation functions as a negative feedback mechanism acting on larval density. In 1989 local discoloration in the Upper Engadine valley was observed in the usual first focus. In 1990 and 1991, however, instead of the expected widespread defoliation damage, larval densities decreased drastically. Based on extensive field data collected from 1961 to 1991 on the development and the survival of the bud moth (Zeiraphera diniana Gn.) and the phenology of the host, Larix decidua L., this paper shows the effect of weather on survival in the egg stage and on the coincidence of larval hatching with the sprouting of the larch. It is shown that the winter and spring weather conditions in 1989–1991 were conducive to unusually high egg mortality. Since these conditions occurred in three successive generations, population growth was effectively reduced and the cycle collapsed prematurely. Thus the rather persistent cyclicity of the larch-larch bud-moth system was disturbed by weather conditions with a very low probability of occurrence, but due to the inherent high resilience of the system, the next population peak with visible defoliation is expected to occur 1996/1997, provided that the weather conditions return to the climatic standard.
Although the possibility of complex dynamical behaviors--limit cycles, quasiperodic oscillations, and aperiodic chaos--has been recognized theoretically, most ecologists are skeptical of their importance in nature. In this paper we develop a methodology for reconstructing endogenous (or deterministic) dynamics from ecological time series. Our method consists of fitting a response surface to the yearly population change as a function of lagged population densities. Using the version of the model that includes two lags, we fitted time-series data for 14 insect and 22 vertebrate populations. The 14 insect populations were classified as: unregulated (1 case), exponentially stable (three cases), damped oscillations (six cases), limit cycles (one case), quasiperiodic oscillations (two cases), and chaos (one case). The vertebrate examples exhibited a similar spectrum of dynamics, although there were no cases of chaos. We tested the results of the response-surface methodology by calculating autocorrelation functions for each time series. Autocorrelation patterns were in agreement with our findings of periodic behaviors (damped oscillations, limit cycles, and quasiperiodicity). On the basis of these results, we conclude that the complete spectrum of dynamical behaviors, ranging from exponential stability to chaos, is likely to be found among natural populations.
The relevance of changes in the composition of larch bud moth populations for the dynamics of its numbers In: den Boer PS, Gradwell GR (eds) Dynamics of Populations
- Baltensweiler
Chaos and insect ecology. Virginia Exp Station Virginia Information Series 91-3 Herbivory in relation to plant nitrogen content
- Logan Ja Hain
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Logan JA, Hain FP (eds) (1991) Chaos and insect ecology. Virginia Exp Station Virginia Information Series 91-3, Blacksburg Virginia Polytechnic Inst and State University Mattson WJ Jr (1980) Herbivory in relation to plant nitrogen content. Annu Rev Ecol Syst 11:119-61
Dynamik von L/irchenwicklerpopulationen 1/ings des Alpenbogens Eidg Anst Forstl Versuchwes Mitt The relevance of changes in the composition of larch bud moth populations for the dynamics of its numbers
- Auer
Auer C (1977) Dynamik von L/irchenwicklerpopulationen 1/ings des Alpenbogens. Eidg Anst Forstl Versuchwes Mitt. 53:71-105 Baltensweiler W (1971) The relevance of changes in the composition of larch bud moth populations for the dynamics of its numbers.
Ergebnisse zw61fjfihriger quantitativer Untersuchun-gender Populationsbewegung des grauen L/irchenwicklers Zeiraphera griseana Hfibner (= diniana Guen6e) im Oberengadin (1949-1960) Eidg Anst Forstl Versuchswes Mitt
- Auer
Auer C (1961) Ergebnisse zw61fjfihriger quantitativer Untersuchun-gender Populationsbewegung des grauen L/irchenwicklers Zeiraphera griseana Hfibner (= diniana Guen6e) im Oberengadin (1949-1960) Eidg Anst Forstl Versuchswes Mitt 37:173-263
Unterschiedliche Sexuallockstoffe bei Lärchen- und Arvenform des grauen Lärchenwicklers
- W Baltensweiler
- E Priesner
- H Arn
- V Delucchi
Vergleichende Untersuchungen über die Entwicklungsgeschwindigkeiten von Eiern und Larven der Lärchen- und Fichtenformen von Zeiraphera diniana Gn
- R Baumann
Le problème des races biologiques chez la tordeuse grise due mélèze Zeiraphera griseana (HB)
- P Bovey
- Jk Maksymov
Untersuchungen zur Dispersionsdynamik des grauen Lärchenwicklers, Zeiraphera diniana Gn. (Lep., Tortricidae). I Morpho- und biometrische Untersuchungen des Puppenund Falterstadiums
- K Vaclena
Chaos and insect ecology. Virginia Exp Station Virginia Information Series 91?
- J A Logan
- F P Hain
Variable Reproductive Patterns within Populations: Ecological and Evolutionary Consequences
- Ca Istock
- W Engels
- Wh Clark
- Jr
- A Fischer
- Pjw Olive
Systems analysis of the larch bud moth system. Part I: the larch-larch bud moth relationship
- A Fischlin
Variable Reproductive Patterns within Populations: Ecological and Evolutionary Consequences Advances in Invertebrate Reproduction
- CA Istock
The rôle of stress in the population dynamics of forest pests. The case of the larch bud moth (Zeiraphera diniana Gn
- W Baltensweiler
Variable Reproductive Patterns within Populations: Ecological and Evolutionary Consequences
- C A Istock
- CA Istock