Life-History and Behavior of the Diamondback Moth Plutella xylostella on Brassicaceae Cultivars over Multiple Generations

The diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a cosmopolitan pest that causes leaf-area reduction in Brassicaceae plants. DBM populations have significant genetic variability that manifests in different feeding preferences and reproductive behaviors across generations. We evaluated the influence of Brassicaceae cultivars on biological and behavioral parameters across 18 generations of DBM populations that were separated and held on three varieties of Brassicaceae: Brassica oleracea var. acephala (kale), Brassica oleracea var. italica (broccoli), and Brassica oleracea var. capitata (cabbage). P, F6, F12, and F18 generations were evaluated, and biological aspects of young adulthood and fertility parameters of adults held on each host plant were examined over multiple generations. Additionally, larvae and adults were subjected to dual-choice and multiple-choice (feeding and oviposition) between cultivars, over generations. The results indicated that larvae of P. xylostella consumed greater quantities of kale and broccoli cultivars, on average (4.05 cm2), than cabbage (2.7 cm2). The number of eggs per female in F18 generation was 1.95 and 2.17 times higher than those in the parental (P) generation, when reared on kale and cabbage. The population reared exclusively on kale had higher net population growth rate (R0), intrinsic rate (rm), finite rate (λ) and generation time (T) than that reared on broccoli and cabbage. Last generations evaluated, the larval stage reared on cabbage showed feeding preference (F18) and oviposition preference (F12 and F18) for cabbage. Thus, we note the existence of learning, characterized as pre-imaginal conditioning to cabbage cultivars, over various DBM generations

The context dependence of the interaction between a semi-arid herb and its herbivores

La herbivoría es la tasa de consumo por parte de los animales de cualquier parte de la planta, incluidas las raíces, el follaje, los tallos o las estructuras reproductivas. La relación entre las plantas y sus herbívoros es uno de los aspectos cruciales de la ciencia biológica, ya que es una ubicua interacción biótica esencial para comprender la diversidad biológica actual, la distribución y abundancia de las diferentes especies de plantas y animales, los procesos biogeoquímicos, el funcionamiento de ecosistemas y sus servicios ecosistémicos. Durante las últimas décadas se han realizado importantes avances en el estudio multifocal de esta interacción, aunque dada su complejidad intrínseca aún quedan muchas cuestiones por resolver. Aún hoy tenemos un conocimiento algo sesgado hacia sistemas más simples como los de las plantas cultivables, con pocos sistemas en los que se haya estudiado conjuntamente el conglomerado de herbívoros naturales de una determinada planta con tasas de consumo realistas, y menos aún que hayan considerado simultáneamente su resistencia y tolerancia frente a su comunidad de herbívoros. Esto es necesario tanto para el avance de este amplio campo y todas sus ramificaciones (por ejemplo, la dinámica de la comunidad), como para poder seguir desarrollando un control de plagas vegetales cada vez más respetuoso con el medio ambiente. En el presente trabajo hemos evaluado experimentalmente la interacción entre la herbácea silvestre Moricandia moricandioides (Brassicaceae) y diversas combinaciones de sus principales herbívoros, la respuesta defensiva de la planta y parte del contexto en el que tanto el daño infligido a la planta como la capacidad de la planta para hacer frente a sus herbívoros pueden variar. Además, profundizamos en aspectos novedosos como son los efectos transgeneracionales, la variación subindividual inducida por herbívoros y la potencialidad del cambio climático para modular las interacciones planta-herbívoro.Herbivory is the rate of consumption by animals of any plant parts, including roots, foliage, stems or reproductive structures. The relationship between plants and their herbivores is one of the crucial aspects of biological science, as it is an ubiquitous biotic interaction essential to understand the current biological diversity, the distribution and abundance of the different plant and animal species, biogeochemical processes, the functioning of ecosystems and their ecosystem services. During the last decades, important advances have been made in the multifocal study of this interaction, although given its intrinsic complexity there are still many questions to be resolved. Even today we have a somewhat biased knowledge towards simpler systems such as like those of crop plants, with few systems in which the set of natural herbivores of any plant has been jointly studied with realistic rates of consumption, and even fewer that have considered simultaneously the plant resistance and tolerance towards its community of herbivores. This is necessary both for the advancement of this broad field and all its ramifications (e.g. community dynamics), as well as for being able to further develop an environmentally-friendly crop protection. In the present work we have experimentally evaluated the interaction between the wild herb Moricandia moricandioides (Brassicaceae) and various combinations of its main herbivores, the defensive response of the plant and part of the context in which both the damage inflicted on the plant and the ability of the plant to deal with its herbivores can vary. In addition, we delve into novel aspects such as transgenerational effects, herbivore-induced subindividual variation and the potentiality of climate change to modulate plant-herbivore interactions.Tesis Univ. Granada.Ministerio de Economía y Competitividad (CGL2011-24840), mediante la concesión de una beca predoctoral (BES-2012-059576)

Limit Laws for Functions of Fringe trees for Binary Search Trees and Recursive Trees

We prove limit theorems for sums of functions of subtrees of binary search trees and random recursive trees. In particular, we give simple new proofs of the fact that the number of fringe trees of size $k=k_n$ in the binary search tree and the random recursive tree (of total size $n$) asymptotically has a Poisson distribution if $k\rightarrow\infty$, and that the distribution is asymptotically normal for $k=o(\sqrt{n})$. Furthermore, we prove similar results for the number of subtrees of size $k$ with some required property $P$, for example the number of copies of a certain fixed subtree $T$. Using the Cram\'er-Wold device, we show also that these random numbers for different fixed subtrees converge jointly to a multivariate normal distribution. As an application of the general results, we obtain a normal limit law for the number of $\ell$-protected nodes in a binary search tree or random recursive tree. The proofs use a new version of a representation by Devroye, and Stein's method (for both normal and Poisson approximation) together with certain couplings

Tree Dependent Identically Distributed Learning

We view a dataset of points or samples as having an underlying, yet unspecified, tree structure and exploit this assumption in learning problems. Such a tree structure assumption is equivalent to treating a dataset as being tree dependent identically distributed or tdid and preserves exchange-ability. This extends traditional iid assumptions on data since each datum can be sampled sequentially after being conditioned on a parent. Instead of hypothesizing a single best tree structure, we infer a richer Bayesian posterior distribution over tree structures from a given dataset. We compute this posterior over (directed or undirected) trees via the Laplacian of conditional distributions between pairs of input data points. This posterior distribution is efficiently normalized by the Laplacian's determinant and also facilitates novel maximum likelihood estimators, efficient expectations and other useful inference computations. In a classification setting, tdid assumptions yield a criterion that maximizes the determinant of a matrix of conditional distributions between pairs of input and output points. This leads to a novel classification algorithm we call the Maximum Determinant Machine. Unsupervised and supervised experiments are shown

Search for top-down and bottom-up drivers of latitudinal trends in insect herbivory in oak trees in Europe

AimThe strength of species interactions is traditionally expected to increase toward the Equator. However, recent studies have reported opposite or inconsistent latitudinal trends in the bottom‐up (plant quality) and top‐down (natural enemies) forces driving herbivory. In addition, these forces have rarely been studied together thus limiting previous attempts to understand the effect of large‐scale climatic gradients on herbivory.LocationEurope.Time period2018–2019.Major taxa studiedQuercus robur.MethodsWe simultaneously tested for latitudinal variation in plant–herbivore–natural enemy interactions. We further investigated the underlying climatic factors associated with variation in herbivory, leaf chemistry and attack rates in Quercus robur across its complete latitudinal range in Europe. We quantified insect leaf damage and the incidence of specialist herbivores as well as leaf chemistry and bird attack rates on dummy caterpillars on 261 oak trees.ResultsClimatic factors rather than latitude per se were the best predictors of the large‐scale (geographical) variation in the incidence of gall‐inducers and leaf‐miners as well as in leaf nutritional content. However, leaf damage, plant chemical defences (leaf phenolics) and bird attack rates were not influenced by climatic factors or latitude. The incidence of leaf‐miners increased with increasing concentrations of hydrolysable tannins, whereas the incidence of gall‐inducers increased with increasing leaf soluble sugar concentration and decreased with increasing leaf C : N ratios and lignins. However, leaf traits and bird attack rates did not vary with leaf damage.Main conclusionsThese findings help to refine our understanding of the bottom‐up and top‐down mechanisms driving geographical variation in plant–herbivore interactions, and indicate the need for further examination of the drivers of herbivory on trees.</p

The sub-lethal effects of repeated cold exposure in insects

While insect cold tolerance has been well studied, the vast majority of work has focused on the effects of a single cold exposure. However, many abiotic environmental stresses, including temperature, fluctuate within an organism\u27s lifespan. In this thesis I address two major questions. First, does frequency of cold exposure impose additional stress on insects? Second, how does this stress translate to performance and fitness? I first summarize the literature on the effects of repeated cold exposure in insects, critically examining experimental designs. I then address my questions experimentally using four insect species with contrasting life histories and responses to cold exposure. I examine the fitness costs of repeated cold exposure in the chill-susceptible fly Drosophila melanogaster by recording survival, generation time, and number of offspring in flies that had received five 2 h, one 2 h, or one 10 h exposure to -0.5 ºC. I found that D. melanogaster trades off immediate survival and reproductive output in response to repeated cold exposure. In the freeze-tolerant caterpillar Pyrrharctia isabella, repeated freezing did not deplete energy reserves, but did damage hemocytes and Malpighian tubules, and led to decreased survival in repeatedly-frozen caterpillars. Similarly, I found in the freeze-avoiding caterpillar Choristoneura fumiferana that frequency of exposure, independent of period, intensity, or duration of cold exposures significantly decreased mortality, likely due to increased investment in cryoprotection at the expense of glycogen reserves. Finally, in the freeze-tolerant fly Eurosta solidaginis, the frequency of exposure, again independent of period, intensity, or duration of cold exposures led to a significant decline in egg production. Repeated cold exposure therefore imposes additional costs to insects, even when intensity and duration of cold are controlled for. This cost may either be a result of accrued damage, or may be energetic as individuals trade off investment in survival mechanisms for reproductive output. Given that many environments are not static, these effects indicate that investigating the effects of repeated stress exposure is important for understanding and predicting physiological responses in the wild