Review of the genus Bursaphelenchus Fuchs, 1937 (Nematoda, Aphelenchida) with some conclusions on the host-parasite and vector-parasite evolution.

INTRODUCTION AND GOALS: Genus Bursaphelenchus includes several pests of the world importance for the rural economy, the most dangerous are the Bursaphelenchus xylophilus (the pinewood nematode caused decline of the pine trees in south Asia and in one spot area in Europe, Portugal, Peninsula de Setubal) and the Bursaphelenchus cocophilus, causing the decline of coco-palm plantations in Carribean and Latin American regions. The peculiarity of the host-parasite association of the genus that the nematode life cycle includes three trophic components: plant (mostly a tree), insect vector and a fungus. Goals of the presentation is to list all species of the world fauna and all efficient diagnostic characters, then create the identification tool and analyze the similarity of species and possible ways and causes of the host-parasite evolution of the group. RESULTS: Complete list of species with synonymy and a catalogue of all efficient diagnostic characters with their states, selected from papers of the most experienced taxonomists of the genus, are given for the genus Bursaphelenchus. List of known records of Bursaphelenchus species with names of natural vectors and plants and their families is given (for world pests the most important groups of trees and insects are listed). The tabular, traditional and computer-aided keys are presented. Dendrograms of species relationships (UPGMA, standard distance: mean character difference) based on all efficient taxonomic characters and separately on the spicule characters only, are given. Discussion whether the species groups are natural or purely diagnostic ones is based on the relationships dendrograms and the vector and associated plant ranges of Bursaphelenchus species; the xylophilus species group (B. xylophilus, B. abruptus, B. baujardi, B. conicaudatus, B. eroshenkii, B. fraudulentus, B. kolymensis, B. luxuriosae; B. mucronatus), the hunti group (B. hunti, B. seani, B. kevini and B. fungivorus) are probably the natural ones. CONCLUSIONS: The parasitic nematode association includes three trophic components: plant, insect vector and fungus. The initial insect-plant complex Scolytidae-Pinaceae is changeable and only in rare occasions the change of the preferred vector to Cerambycidae (the xylophilus group), Hymenoptera (the hunti group) led to formation of the natural species-groups. From the analysis it is clear that although the vector range is changeable it is comparatively more important for the evolution of the genus Bursaphelenchus than associations with plants at the family level. Data on the fungi species (3rd component in natural Bursaphelenchus associations) are insufficient for the detailed comparative analysis

Habitat, world geographic range, and embryonic development of hosts explain the prevalence of avian hematozoa at small spatial and phylogenetic scales

The factors explaining interspecific differences in prevalences of blood parasites in birds are poorly known. We simultaneously assessed 20 social, ecological, life history, and sampling-related variables that could influence hemoparasite prevalences among diurnal birds of prey in Spain. Our results show that multiple factors are responsible for the studied host-parasite association. We confirmed for the first time that prevalence is inversely correlated to the embryonic development period, and thus probably to immune performance, even among closely related birds. Macrohabitat features related to vector availability are also important, prevalences being higher in species breeding in forested habitats. Finally, prevalence is positively correlated with the host's world geographic range. We hypothesize that larger geographic ranges offered more opportunities for host-vector-hemoparasite associations to become established. The results from our multivariate analyses differ from those obtained through univariate ones, showing that all potential factors should be assessed jointly when testing any ecological or evolutionary hypothesis dealing with parasites.Peer Reviewe

Feather-busting bacteria

Journal ArticleI ONCE HAD A COLLEAGUE who delighted in the aphorism, which he proudly coined himself, "If it's too small to see with the naked eye, it ain't there." Sadly, this view may as well be true for ornithologists who study birds only through unaided eyes, binoculars, or spotting scopes. But birds can also be studied through conventional and electron microscopes

Modelling evolution of host defence in seasonal environments.

Infectious disease is rife throughout the world, with species at risk of infection at every level, from bacteria to humans. These diseases can have devastating effects on populations, which has led to a rich biological and mathematical literature on this topic. There are many factors that can affect the spread and impact of an infectious disease, including environmental heterogeneity and host-parasite evolution. The combination of infection dynamics, heterogeneous environments and evolution could provide powerful insights into real-world systems; however, this has yet to be explored in much detail with regards to temporally heterogeneous environments. In this thesis I use mathematical models and experimental techniques to investigate the effect of temporally fluctuating environments on host-parasite evolution. Throughout the mathematical analysis, I use the adaptive dynamics framework to study evolution, and implement temporal heterogeneity through a periodic host birth rate. First, I consider host-only evolution through avoidance, and consider how increasingly variable environments affects the end-point of evolution. Second, I investigate the potential for host diversity through three different defence mechanisms in a seasonal environment, with a particular focus on evolution through mortality tolerance. I then conduct an experimental evolution study using the bacteria P. fluorescens SBW25 and its parasitic bacteriophage SBW25Φ2, where environmental heterogeneity is implemented through oscillating nutrient concentrations. The results from the experiment are reinforced by a coevolutionary model, which incorporates seasonality through evidence-based assumptions on the bacterial growth. The work in this thesis is part of a growing field of research investigating temporal environments and evolution in host-parasite systems. It contributes some important results to the field, and demonstrates the power of developing experimental and theoretical work together, which can result in a more cohesive understanding of host-parasite evolution

Epigenetic and phenotypic variability in populaitons of Schistosoma mansoni - a possible kick-off for adaptative host/parasite evolution

International audienceEpigenetics, the science of heritable but modifiable information, is now a well-accepted component of many research fields. Nevertheless, epigenetics has not yet found broad appreciation in one of the most exciting fields of biology: the comprehension of evolution. This is surprising, since the reason for the existence of this alternative information-transmitting system lies certainly in the evolutionary advantage it provides. Theoretical considerations support a model in which epigenetic mechanisms allow for increasing phenotypic variability and permit populations to explore the adaptive landscape without modifications of the genotype. The data presented here support the view that modulating the epigenotype of the human bloodfluke Schistosoma mansoni by treatment of larvae with histone deacetylase inhibitor leads indeed to an increase of phenotypic variability. It is therefore conceivable that environmentally induced changes in the epigenotype release new phenotypes on which selection can act and that this process is the first step in adaptive evolution

Host-parasite evolution in male-haploid hosts : an individual based network model

Host-parasite co-evolution is a key component of the Red Queen Hypothesis (RQH). The RQH currently being one of the main hypotheses describing the evolution of sex and recombination. However, most analyses in this area have either ignored parasite transmission or included it either with mean field or simple frequency based models. Moreover models have rarely addressed the issue of male haploid species. We here use agent based models to qualify the interactions between host- and parasite-based transmission parameters and virulence comparing diploid with male-haploid species. We found diploid hosts to have a higher fitness under the inverse matching allele mode compared to male haplodiploid hosts which in turn have a higher fitness under the matching allele model . Selection for recombination was rare but whenever selection for recombination was evident (\6.6 %), the resulting recombination rates were both consistently higher and more frequent in male haploids.Funding for the research was provided by the Deutsche Forschungsgemeinschaft within the priority program SPP 1399 and by yDiv, the Synthesis Centre for Biodiversity Sciences—a unit of the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, also funded by the Deutsche Forschunggemeinschaft (FZT 118).http://link.springer.com/journal/106822016-01-30hb201

How do fluctuating ecological dynamics impact the evolution of hosts and parasites?

Theoretical models of the evolution of parasites and their hosts have shaped our understanding of infectious disease dynamics for over 40 years. Many theoretical models assume that the underlying ecological dynamics are at equilibrium or constant, yet we know that in a great many systems there are fluctuations in the ecological dynamics owing to a variety of intrinsic or extrinsic factors. Here, we discuss the challenges presented when modelling evolution in systems with fluctuating ecological dynamics and summarize the main approaches that have been developed to study host–parasite evolution in such systems. We provide an in-depth guide to one of the methods by applying it to two worked examples of host evolution that have not previously been studied in the literature: when cycles occur owing to seasonal forcing in competition, and when the presence of a free-living parasite causes cycles, with accompanying interactive Python code provided. We review the findings of studies that have explored host–parasite evolution when ecological dynamics fluctuate, and point to areas of future research. Throughout we stress the importance of feedbacks between the ecological and evolutionary dynamics in driving the outcomes of infectious disease systems

Climate change effects on Antarctic penguins

La península antártica es uno de los lugares del planeta donde más y más rápidamente están aumentando las temperaturas y por tanto donde se están produciendo notables cambios ambientales debidos al cambio climático. Ejemplos de estos cambios son la disminución del hielo marino, el descenso de la presencia de algas en este hielo y una reducción de la abundancia de krill. Como consecuencia, las poblaciones de pingüinos, en particular el pingüino de adelia y el pingüino barbijo están sufriendo un acusado descenso. En el presente artículo se profundiza en las consecuencias del cambio climático en la Antártida en los pingüinos con especial atención a los resultados obtenidos dentro del proyecto PINGUCLIM que trata de determinar dichos efectos en la fisiología de estas especies a través de la interacción parásito-hospedador.The Antarctic Peninsula is one of the places in the planet where more and faster the temperatures are increasing producing environmental changes due to the climate change. Some examples of these changes are the decresase in the sea-ice extent, the reduction of algae production, and then the reduction of the abundance of krill. As a consequence of these changes, penguin populations have suffered a decline, specially chinstrap and adelie species. The present paper address the consequences of the climate change in the Antarctic penguins emphasizing the results obtained within the PINGUCLIM project which studies such effects in the penguin physiology though host-parasite interaction.Los resultados mostrados en el presente artículo han sido obtenidos en los proyectos REN2001-5004, CGL2004-01348, POL205-05175 y CGL2007-60369 financiados por el Ministerio de Ciencia e Innovación

Eurasian Blackbirds (<i>Turdus merula</i>) and their gastrointestinal parasites : A role for parasites in life-history decisions?

Parasites are increasingly being recognized as potent agents of selection. Gastrointestinal parasites, however, have largely been ignored. The aim of the present thesis was to contribute to the still scarce knowledge about gastrointestinal parasites in ecological, evolutionary and behavioural studies and to critically elucidate methodological aspects of indirect parasitic assays. Fecal samples were collected from an urban, individually marked population of Eurasian Blackbirds (Turdus merula L.,1758) and were examined for eggs and oocysts of gastrointestinal parasites. Four parasitic taxa commonly occurred in the population: protozoans of the genus Isospora, nematodes of the genus Capillaria, cestodes and acanthocephalans. Isospora spp. and Capillaria spp. were the most frequent parasites, infecting 53 % and 56 % of birds, respectively. These results markedly differed from a similar study conducted 35 years ago (Binder 1971) and explicitly demonstrate, that the parasite communities and prevalences assessed from single populations can not be taken as representative for the whole species, as has repeatedly been done in the past. It was investigated whether these parasites impose fitness costs on their hosts. It is a central assumption of life-history theory that the availability of energy or resources is limited. Thus, the investment in one costly trait can only occur at the expense of another costly trait (Stearns 1992). In adult male blackbirds I found a cost of parasitism. Males that had invested more heavily in the feeding of nestlings, were also more likely to be infected with gastrointestinal parasites. Female infection prevalence was very high (95%) and significantly higher than in males. Since females are alone responsible for nest building, egg laying and incubating they probably incur high reproductive costs already prior to the nestling feeding stage. In nestlings no direct cost of parasitism on aspects of somatic growth could be found. Quite on the contrary, nestling size, measured as tarsus length and wing length were positively associated with prevalence of coccidian infection. I conclude that infections with Isospora spp. do not impose the predicted trade-off on blackbird nestlings. Rather, infections with Isopora spp. seem to be a function of feeding rate. Thus, an alternative trade-off, namely between energy intake and risk of infection seems to become of primary importance for blackbird nestlings. It is a still commonly practised method to assess a bird’s infection status by the examination of a single sample, although it is known that the failure to find parasitic stages does not reliably indicate the absence of an infection. Several properties of the host and of the parasites potentially influence the probability to detect parasitic stages in samples. One such property is the temporal fluctuation of oocyst or egg shedding by parasites. In fecal samples of adult and nestling blackbirds I found oocysts of Isospora spp. to be shedded more frequently and at higher intensities in the afternoon. This periodic phenomenon, the diurnal shedding of isosporan oocysts in the feces, is in congruence with results on Isospora oocyst shedding in other bird species. In order to give future investigators a tool to estimate the quality of their indirect method, I developed a model in which the calculation of the parameter pinf determines the probabilty to falsely denote an infected individual as “not infected” if no parasites can be found in n samples collected from this individual. The model showed that in the blackbird population it was not possible to reliably (with a probability of 95%) denote an individual as not infected after the evaluation of a single fecal sample. These results suggest that great consciousness and caution have to be used in the methodological planning of studies involving indirect parasitic assays