Thermal limitations to the biological control of Gonipterus sp. n. 2 (Coleoptera: Curculionidae) in South African Eucalyptus plantations

BackgroundAn important objective of evolutionary biology is to understand the processes that govern phenotypic variation in natural populations. We assessed patterns of morphological and genetic divergence among coastal and inland lake populations of nine-spined stickleback in northern Sweden. Coastal populations are either from the Baltic coast (n = 5) or from nearby coastal lakes (n = 3) that became isolated from the Baltic Sea (< 100 years before present, ybp). Inland populations are from freshwater lakes that became isolated from the Baltic approximately 10,000 ybp; either single species lakes without predators (n = 5), or lakes with a recent history of predation (n = 5) from stocking of salmonid predators (~50 ybp).ResultsCoastal populations showed little variation in 11 morphological traits and had longer spines per unit of body length than inland populations. Inland populations were larger, on average, and showed greater morphological variation than coastal populations. A principal component analysis (PCA) across all populations revealed two major morphological axes related to spine length (PC1, 47.7% variation) and body size (PC2, 32.9% variation). Analysis of PCA scores showed marked similarity in coastal (Baltic coast and coastal lake) populations. PCA scores indicate that inland populations with predators have higher within-group variance in spine length and lower within-group variance in body size than inland populations without predators. Estimates of within-group PST (a proxy for QST) from PCA scores are similar to estimates of FST for coastal lake populations but PST >FST for Baltic coast populations. PST >FST for PC1 and PC2 for inland predator and inland no predator populations, with the exception that PST <FST for body size in inland populations lacking predators.ConclusionsBaltic coast and coastal lake populations show little morphological and genetic variation within and between groups suggesting that these populations experience similar ecological conditions and that time since isolation of coastal lakes has been insufficient to demonstrate divergent morphology in coastal lake populations. Inland populations, on the other hand, showed much greater morphological and genetic variation characteristic of long periods of isolation. Inland populations from lakes without predators generally have larger body size, and smaller spine length relative to body size, suggesting systematic reduction in spine length. In contrast, inland populations with predators exhibit a wider range of spine lengths relative to body size suggesting that this trait is responding to local predation pressure differently among these populations. Taken together the results suggest that predation plays a role in shaping morphological variation among isolated inland populations. However, we cannot rule out that a causal relationship between predation versus other genetic and environmental influences on phenotypic variation not measured in this study exists, and this warrants further investigation.

The acute thermal tolerances of six Daphnia species were compared at three acclimation temperatures. Of the species tested, all but one showed an increase in thermal tolerance when acclimated at higher temperature. Comparison of the regression relationships between thermal tolerances and acclimation temperature revealed no significant interspecific differences among species in their improvement of thermal tolerance caused by acclimation. However, significant intraspecific differences in thermal tolerance were noted. Daphnia obtusa had the highest tolerance, while D. pulex had the lowest. Among the other species acclimated at 10 C, thermal tolerance declined in a sequence of D. ambigua, D. magna, D. carinata, and D. nivalis. The differences in thermal tolerance noted among species were correlated with maximum temperatures of the environment from which they originated. While comparison of clones of D. pulex from several geographic localities revealed up to 2 C differences in acute thermal tolerance, there was no evidence of clonal variation in thermal tolerance of D. magna.

Variation in the endospermal protein patterns of seeds amongst and between inland and coastal populations of the dune building grassLeymus arenarius was examined in Iceland. Seeds were collected from six coastal populations and five inland populations in Iceland. Endospermal proteins (prolamins) of seeds were extracted with Tris-buffered 2-propanol (50%) and β-mercaptoethanol (0.5% v/v). We used 8% and 12% sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) to separate the prolamin protein bands, which were stained with Coomassie Brilliant Blue R. Coastal populations were differentiated from inland populations on the basis of high frequency of high molar weight (HMW) (110–150 kg mol−1) prolamins. Coastal populations had significantly higher proportions of their seed with more than two HMW prolamins, than those of inland populations. Subtle differences were found among the HMW prolamins of coastal and inland populations indicating limited intrapopulation variation. The dynamic environment of sand dunes probably influences the genetic composition of these populations. The results suggest that seeds of the inland and coastal populations should be treated separately in sand dune reclamation and restoration works

In the face of global warming, both the absolute thermal tolerance of an ectotherm, and its ability to shift its tolerance level via acclimation, are thought to be fundamentally important. Understanding the links between tolerance and its plasticity is therefore critical to accurately predict vulnerability to warming. Previous studies in a number of ectotherm taxa suggest trade-offs in the evolution of thermal tolerance and its plasticity, something which does not, however, apply to Deronectes diving beetles, where these traits are instead positively correlated. Here we revisit the relationship between thermal tolerance and plasticity in these beetles, paying attention to a recently discovered morphological adaptation supporting under water respiration – setal tracheal gills. Hollow setae on the elytra interconnect with the beetle’s tracheal system, providing a gas exchange surface that allows oxygen to be extracted directly from the water. This enables individuals to stay submerged for longer than their subelytral air stores would allow. We show that hypoxia reduced heat tolerance, especially when individuals were denied access to air, forcing them to rely solely on aquatic gas exchange. Species with higher densities of these gas-exchanging setae exhibited improved cold tolerance, but reduced heat tolerance and lower plasticity of heat tolerance. Differences in setal tracheal gill density across species were also related to habitat use: species with low gill density were found mainly in intermittent, warmer rivers, where underwater gas exchange is more problematic and risks of surfacing may be smaller. Moreover, when controlling for differences in gill density we no longer found a significant relationship between heat tolerance and its plasticity, suggesting that the previously reported positive relationship between these variables may be driven by differences in gill density. Differences in environmental conditions between the preferred habitats could simultaneously select for characteristic differences in both thermal tolerance and gill density. Such simultaneous selection may have resulted in a non-causal association between cold tolerance and gill density. For heat tolerance, the correlations with gill density could reflect a causal relationship. Species relying strongly on diffusive oxygen uptake via setal tracheal gills may have a reduced oxygen supply capacity and may be left with fewer options for matching oxygen uptake to oxygen demand during acclimation, which could explain their reduced heat tolerance and limited plasticity. Our study helps shed light on the mechanisms that underpin thermal tolerance and plasticity in diving air-breathing ectotherms, and explores how differences in thermal tolerance across species are linked to their selected habitat, morphological adaptations and evolutionary history.

Ecological compatibility of GM crops and biological control

Although hurricanes can cause severe hazard effects well inland, little is known about the evacuation behaviour of inland populations compared to coastal populations. Using survey data collected in the United States after Hurricanes Florence (2018), Michael (2018), Barry (2019), and Dorian (2019), we investigate differences between coastal and inland populations in evacuation decisions and timing, and their causes. The data indicate that coastal populations evacuated at a higher rate than their inland counterparts (those not in coastal counties) in every hurricane studied. Chi-square tests identified differences in characteristics of coastal and inland populations, and a multiple logistic regression identified variables associated with evacuation. Together they suggest multiple factors that help explain the difference in evacuation rates. The most significant findings were related to geographic differences in the issuance of evacuation orders and reported receiving of orders (whether or not orders were actually issued). Most interestingly, the analysis indicates that variance between inland and coastal evacuation is not fully explained by the factors suggested in existing literature. We suggest here that differences between inland and coastal evacuation may also result from risk perception, in particular, a view that hurricanes are a coastal phenomenon and therefore do not apply to inland populations.

Scant attention has been paid to invasive species whose range and abundance has decreased after an initial range expansion. One such species is the browntail moth Euproctis chrysorrhoea L, which was discovered in the eastern United States in 1897. Its range expanded until 1914; after 1915, however, its range contracted and now it persists in only two isolated coastal locations. Although a biological control agent has been implicated in this range collapse, cold inland winter temperatures may also help to restrict browntail moth populations. We surveyed coastal versus inland habitats in Maine and Massachusetts for browntail moth overwintering mortality and larval density per web. We also performed an experiment assessing these same variables in coastal versus inland habitats on different host plant species and at different initial larval densities. We also analyzed temperature records to assess whether winter temperatures correlated with changes in the invasive range. Overwintering mortality was lower in coastal populations for both the experimental populations and in the Maine field survey. Experimental populations in Cape Cod coastal areas also had lower rates of fall mortality and higher larval densities, suggesting that coastal areas are better year-round habitats than inland areas. There were no consistent differences between coastal and inland populations in their response to larval density or host plant, although overall survival in both areas was higher at low initial larval densities and affected by host identity. There was also no difference in two measures of the coldest winter temperatures during browntail moth's expansion and contraction. Our results show that climate affects browntail moth, but suggest that winter temperatures cannot explain both the rapid expansion and subsequent collapse of this pest.

Oligonychus perseae Tuttle, Baker and Abatiello (Acari: Tetranychidae) is a foliar pest of avocado, Persea americana Miller (Lauraceae), and both species are native to Mexico. Damaging O. perseae populations can occur in areas of the world where the Hass cultivar is grown commercially, including California (USA), Costa Rica, Spain and Israel. In California, the efficacy of biological control agents, including well studied predators such as Euseius hibisci (Chant) and Neoseiulus californicus (McGregor) (Acari: Phytoseiidae), for management of O. perseae populations in commercial orchards, is limited. This situation differs from the successful biological control of introduced heterospecifc tetranychids on California avocados during previous decades. Using California avocados as a model system, potential key factors responsible for the limitations of O. perseae biological control are discussed. One key factor that accounts for the prevalence of O. perseae infestations in California is the increasing distribution of avocado cultivars that are highly susceptible to O. perseae. Other attributes contributing to cultivar susceptibility could potentially include the limited searching ability of predators for O. perseae. Additionally, some life history traits of phytoseiids that have been used to target O. perseae populations likely restrict their utility as effective biological control agents of this pest. Future research directions for improving O. perseae biological control strategies are discussed. Among these is the prospect of using members of the family Stigmaeidae that occur naturally on avocado but whose potential as biological control agents has not been well studied.

Populations of common killifish, Fundulus heteroclitus, are distributed along the Atlantic coast of North America through a steep latitudinal thermal gradient. We examined intraspecific variation in whole-animal thermal tolerance and its relationship to the heat shock response in killifish from the northern and southern extremes of the species range. Critical thermal maxima were significantly higher in southern than in northern fish by approximately 1.5 degrees C at a wide range of acclimation temperatures (from 2-34 degrees C), and critical thermal minima differed by approximately 1.5 degrees C at acclimation temperatures above 22 degrees C, converging on the freezing point of brackish water at lower acclimation temperatures. To determine whether these differences in whole-organism thermal tolerance were reflected in differences in either the sequence or regulation of the heat shock protein genes (hsps) we obtained complete cDNA sequences for hsc70, hsp70-1 and hsp70-2, and partial sequences of hsp90alpha and hsp90beta. There were no fixed differences in amino acid sequence between populations in either hsp70-1 or hsp70-2, and only a single conservative substitution between populations in hsc70. By contrast, there were significant differences between populations in the expression of many, but not all, of these genes. Both northern and southern killifish significantly increased hsp70-2 levels above control values (T(on)) at a heat shock temperature of 33 degrees C, but the magnitude of this induction was greater in northern fish, suggesting that northern fish may be more susceptible to thermal damage than are southern fish. In contrast, hsp70-1 mRNA levels increased gradually and to the same extent in response to heat shock in both populations. Hsc70 mRNA levels were significantly elevated by heat shock in southern fish, but not in northern fish. Similarly, the more thermotolerant southern killifish had a T(on) for hsp90alpha of 30 degrees C, 2 degrees C lower than that of northern fish. This observation combined with the ability of southern killifish to upregulate hsc70 in response to heat shock suggests a possible role for these hsps in whole-organism differences in thermal tolerance. These data highlight the importance of considering the complexity of the heat shock response across multiple isoforms when attempting to make linkages to whole-organism traits such as thermal tolerance.

Resources added to agroecosystems to enhance biological control are potentially available to multiple members of the resident insect community—not only the biological control agents for which the resources are intended. Many studies have examined the effects of sugar feeding on the efficacy of biological control agents. However, such information is lacking for other, interacting species such as facultative hyperparasitoids, which may contribute to pest suppression but can also interfere with introduced biological control agents. Under greenhouse conditions, we tested the direct effects of sugar and nectar provisioning on the longevity, host‐killing impact and offspring production of two pupal parasitoids associated with leek moth, Acrolepiopsis assectella: the introduced biological control agent, Diadromus pulchellus, and the native facultative hyperparasitoid, Conura albifrons. Adding sucrose, buckwheat or a combination of buckwheat and common vetch to a sugar‐deprived system (potted leek plants in cages) increased parasitoid longevity and resulted in higher leek moth parasitism and mortality compared to water or common vetch treatments. However, the two parasitoid species exhibited a distinct temporal response to the treatments, likely influenced by differences in their life histories. This study provides insight into how integrating conservation biological control techniques could affect the success of a classical biological control programme.

Environmental change and habitat fragmentation will affect population densities for many species. For those species that have locally adapted to persist in changed or stressful habitats, it is uncertain how density dependence will affect adaptive responses. Anurans (frogs and toads) are typically freshwater organisms, but some coastal populations of green treefrogs (Hyla cinerea) have adapted to brackish, coastal wetlands. Tadpoles from coastal populations metamorphose sooner and demonstrate faster growth rates than inland populations when reared solitarily. Although saltwater exposure has adaptively reduced the duration of the larval period for coastal populations, increases in densities during larval development typically increase time to metamorphosis and reduce rates of growth and survival. We test how combined stressors of density and salinity affect larval development between salt‐adapted (“coastal”) and nonsalt‐adapted (“inland”) populations by measuring various developmental and metamorphic phenotypes. We found that increased tadpole density strongly affected coastal and inland tadpole populations similarly. In high‐density treatments, both coastal and inland populations had reduced growth rates, greater exponential decay of growth, a smaller size at metamorphosis, took longer to reach metamorphosis, and had lower survivorship at metamorphosis. Salinity only exaggerated the effects of density on the time to reach metamorphosis and exponential decay of growth. Location of origin affected length at metamorphosis, with coastal tadpoles metamorphosing slightly longer than inland tadpoles across densities and salinities. These findings confirm that density has a strong and central influence on larval development even across divergent populations and habitat types and may mitigate the expression (and therefore detection) of locally adapted phenotypes.

The durability of a control method for plant protection is defined as the persistence of its efficacy in space and time. It depends on (i) the selection pressure exerted by it on populations of plant pathogens and (ii) on the capacity of these pathogens to adapt to the control method. Erosion of effectiveness of conventional plant protection methods has been widely studied in the past. For example, apparition of resistance to chemical pesticides in plant pathogens or pests has been extensively documented. The durability of biological control has often been assumed to be higher than that of chemical control. Results concerning pest management in agricultural systems have shown that this assumption may not always be justified. Resistance of various pests to one or several toxins of Bacillus thuringiensis and apparition of resistance of the codling moth Cydia pomonella to the C. pomonella granulovirus have, for example, been described. In contrast with the situation for pests, the durability of biological control of plant diseases has hardly been studied and no scientific reports proving the loss of efficiency of biological control agents against plant pathogens in practice has been published so far. Knowledge concerning the possible erosion of effectiveness of biological control is essential to ensure a durable efficacy of biological control agents on target plant pathogens. This knowledge will result in identifying risk factors that can foster the selection of strains of plant pathogens resistant to biological control agents. It will also result in identifying types of biological control agents with lower risk of efficacy loss, i.e., modes of action of biological control agents that does not favor the selection of resistant isolates in natural populations of plant pathogens. An analysis of the scientific literature was then conducted to assess the potential for plant pathogens to become resistant to biological control agents.

Abstract. The dioecious shrub Ceratiola ericoides (Florida rosemary) dominates xeric, infrequently burned Florida scrub vegetation, often to the near‐exclusion of other woody species. We studied the spatial pattern, age, sex and size structure of four populations in Florida, USA: two coastal scrub populations subject to recurrent local disturbances due to sand movement, and two inland scrub populations in sites periodically burned by stand‐replacing fires. The age structure of individual genets was estimated from node counts and used to describe the age structure of the populations. The sex ratio of males to females was not significantly different from 1:1, except within a female‐biased coastal population subject to frequent sand movement. Node counts indicated that the mean age for reproductive individuals was 15 ‐ 16 yr for the inland populations and 13 ‐ 16 yr for the coastal populations. In all sites, there was no difference in mean age between males and females. Vegetative reproduction was uncommon except for the least‐disturbed coastal population where 72 % of the reproductive individuals originated through layering. Individuals were generally randomly dispersed at the coastal sites, whereas significant aggregation of males and females occurred in the inland sites where the populations were initiated following fire. Seedling recruitment was continuous in the disturbed coastal scrub site, where 35% of the individuals were juveniles. Most juveniles were dispersed from 0.5 to 0.75 m around females. At one of the inland sites, where juveniles comprised 11% of the population, juveniles were clustered at 0.25 to 5.75 m around females. Coastal populations were all‐aged, while inland populations were uneven‐aged. Recruitment appears to follow periods of disturbance; infrequent fire in the inland populations and continuous sand movement on the coast are factors initiating recruitment.

Species of plants and animals have characteristic climatic requirements for growth, survival and reproduction that limit their geographic distribution, abundance and interactions with other species. To analyze this complexity requires the development of models that include not only the effects of biotic factors on species dynamics and interactions, but also the effects of abiotic factors including weather. The need for such capacity has appreciably increased as we face the threat of global climate change. In this paper, bi- and tri-trophic physiologically based demographic models of alfalfa, cotton, grape, olive and the noxious weed yellow starthistle systems are used to explore some of the potential effects of climate change. A general model that applies to all species in all trophic levels (including the economic one) is used to simulate the effects of observed and projected weather on system dynamics. Observed daily weather and that of climate model scenarios were used as forcing variables in our studies. Geographic information system (GRASS GIS) is used to map the predicted effects on species across the varied ecological zones of California. The predictions of the geographic distribution and abundance of the various species examined accords well with field observations. Furthermore, the models predict how the geographic range and abundance of the some species would be affected by climate change. Among the findings are: (1) The geographic range of tree species such as olive that require chilling to break dormancy (i.e. vernalization) may be limited in some areas due to climate warming, but their range may expand in others. For example, olive phenology and yield will be affected in the southern part of California due to high temperature, but may expand in northern areas until limited by low winter temperatures. Pest distribution and abundance will also be affected. For example, climate warming would allow the cold intolerant pink bollworm in cotton to expand its range into formerly inhospitable heavy frost areas of the San Joaquin Valley, and damage rates will increase throughout its current range. The distribution and abundance of other cold intolerant pests such as olive fly, the Mediterranean fruit fly and others could be similarly affected. In addition, species dominance and existence in food webs could change (e.g. in alfalfa), and the biological control of invasive species might be adversely affected (e.g. vine mealybug in grape). The distribution and abundance of invasive weeds such as yellow starthistle will be altered, and its control by extant and new biological control agents will be difficult to predict because climate change will differentially affects each. (2) Marginal analysis of multiple regression models of the simulation data provides a useful way of analyzing the efficacy of biological control agents. Models could be useful as guides in future biological control efforts on extant and new exotic pest species. (3) Major deficiencies in our capacity to predict the effects of climate change on biological interactions were identified: (1) There is need to improve existing models to better forecast the effects of climate change on crop system components; (2) The current system for collecting daily weather data consists of a patchwork of station of varying reliability that often record different variables and in different units. Especially vexing, is the dearth of solar radiation data at many locations. This was an unexpected finding as solar energy is an important driving variable in biological systems.

Vegetable crops may be produced as both fresh market and processed commodities and can be grown under field conditions or in controlled environments, such as glasshouses or other similar structures. There are numerous fungal diseases that attack a wide range of these vegetable crops (Howard et al. 1994), thereby reducing crop yield and quality. Methods for disease control have included the use of cultural practices to reduce pathogen inoculum and disease incidence, development of resistant cultivars, as well as the application of chemical fungicides to inhibit pathogen development. The use of biological control strategies has also demonstrated the potential of fungi and yeasts in reducing a range of fungal pathogens that cause various diseases on vegetable crops. In this chapter, some examples of recent successes in biological control of fungal diseases of vegetable crops using fungi and yeasts, and the mechanisms by which pathogen control was achieved will be reviewed. In addition, the utilization of techniques in biotechnology to aid in the implementation of biological control strategies for disease control will be reviewed. These include techniques to investigate mechanism(s) of action of the biological control agent, development of strains with enhanced efficacy through genetic manipulation, monitoring the growth and spread of biocontrol agents using molecular techniques, and characterization of strains using geneticmarkers and biochemicalmethods. The diseases to be considered in this chapter for which biocontrol strategies have been described include those caused by pathogenic fungi that infect the seed and early stages of seedling growth, causing seed decay and damping-off. Examples of these fungi are Rhizoctonia solani Kuhn, various species of Fusarium and Pythium, and Sclerotium rolfsii Sacc. Fungal pathogens that infect the roots and crown of developing plants, causing root and crown rots and vascular wilts, have also been researched for biological control strategies. These include fungi such as Pythium spp., Fusarium spp., and Sclerotinia sclerotiorum (Lib.) de Bary. A third group of foliar-infecting fungi of vegetable crops that cause leaf spots and blights and stem infection, also have biological control strategies developed against them. These include Botrytis cinerea Pers. ex Fr. (gray mold), Didymella bryoniae (Auersw.) Rhem (gummy stem blight), S. sclerotiorum (white mold), and Sphaerotheca and Erysiphe spp. (powdery mildews). Many different fungal and yeast biological control agents have been identified and evaluated for disease control potential against the above-mentioned pathogens, and some have been formulated and brought to market to provide disease control options for producers of vegetable crops. The use of biological control agents may be particularly attractive for vegetable crops grown in glasshouses, due to the high market value of these crops and the possibility for control of environmental parameters, particularly temperature and relative humidity (Paulitz and Belanger 2001). These are important variables that can significantly influence the efficacy of biological control agents under natural field conditions (Paulitz 1997). The rationale for development of biological control agents against fungal diseases on vegetable crops was to provide an additional/alternative approach to augment/replace the use of