Determinants of variation in host-parasite interactions

Principal researcher: Francisco Valera Hernández:

Period: 2015-2018

Disease occurs non-randomly in space and factors such as climate, physical habitat characteristics, community context, host species identity and parasite species identity may account for such variation. Yet, our understanding on how biotic and abiotic factors determine host-parasite interactions is still limited and we ignore much about the general rules and mechanisms explaining the above-mentioned relationships. Another important gap in our knowledge about emerging infectious diseases is that, while the host specificity between specific hosts and parasites has been frequently revealed, the specificity between parasites and their vectors remains largely neglected even for major host-vector-parasite systems. This shortcoming has been suggested as the major obstacle to dealing with the current emerging infectious diseases crisis.

The main goal of this project is to disentangle the context dependency of local host-parasite interactions and the relative importance of the processes influencing parasitism intensity by following a community ecology-oriented approach encompasing various study systems and spatio-temporal scales. We also aim at uncovering some mechanisms underlying the links between habitat and disease, both between hosts and parasites and between hosts, vectors and haematozoan parasites. The general hypothesis of the project is that environmental conditions strongly influence, either directly and/or indirectly, the occurrence of epidemics and host-parasite interactions. Specifically the project focuses on:

- the effect of spatial and temporal variation in climatic conditions on the ecto and endoparasitic community of several study systems,

- the effect of physical features of the habitat on the ectoparasitic community of an avian guild and on parasite dispersal via its influence on local host density and host community structure,

- the evaluation of the variability and context dependency of local host-parasite interactions,

- the identification of the host-vector-parasite associations in our study systems.

The strength of this project relies on its broad framework that jointly considers the interactions among biotic drivers (e.g. host density), and abiotic/physical drivers of epidemics. This approach is necessary for a complete understanding of disease ecology once the study of hostparasite interactions in isolation has proved insufficient. Moreover, by studying patterns of variation of parasitisation across a range of scales, we can gain insight into the relative importance of different processes involved in the dynamics of diseases. This project will improve the understanding of links between climate, microclimate, habitat structure, species interactions, and parasitism. Highlighting these links and the underlying mechanisms is necessary to predict accurately the likelihood of epidemics in particular locations, what is of major interest fin the current scenario of climate warming. Finally, if the vectorial role of some of our study species is confirmed, this project will have a norteworthy impact because vector and host ecology are studied simultaneously and comprehensively to reveal their effects on the spread of avian haemoparasites

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The role of phenotypic signals and genetic quality in male-male competition in birds

Principal researcher: Magdalena Zagalska-Neubauer

Period: 2014-2017

One of the most important manifestations of animals life is their ability to communicate effectively with each other. Morphological, behavioural or physiological characteristics are signals sent by the sender toward the recipient via different, often complementary, communication channels: chemical, tactile, visual and acoustic. Regardless of which channel is used in a communication process, the essential intention of a sender is to modify behaviour of the signal’s recipient in a manner beneficial to himself, while the recipient is trying to evaluate the received information and achieve maximum benefit from the interaction. In many animal species, particularly birds, visual and acoustic signals play a crucial role in both mate choice and interactions between individuals of the same sex. Through visual and acoustic signals, territorial males inform neighbours and intruders about their quality, motivation to defend the territory, and/or social status. Sexually selected traits often signal quality or motivation and form specific ‘status badges’. Such signals underlie intra- and intersexual communication and are central to the signalling theory. The signalling theory, to which the project refers, proposes that plumage traits or song characteristics have evolved to signal individual quality and the ability of individuals to win agonistic encounters. It is also possible that some of these signals indicate genetic potential of individuals. In general, signalling dominance brings benefits to the signaller and the receiver, as intrasexual competition over limited resources like territory, food and mates is often intense. Thus, mechanisms that settle conflicts without physical aggression are expected to be favoured by selection. Costs, benefits, and resultant fitness trade-offs are thought to maintain reliable status badges as evolutionarily stable signals. The main goal of our project is to evaluate phenotypic signals and to assess their relationship with evolutionarily important genes in male-male competition in the chaffinch (Fringilla coelebs). This small passerine has plumage with conspicuous white wing epaulettes, which potentially serve as quality indicators. It has been shown that larger epaulettes correlate with more aggressive behaviour and it is possible that honestly indicate male quality. Quality assessment based on the size of male epaulettes is possible only when individuals are well visible and in sight. For medium and long distance communication males use also the acoustic communication channel. The repertoire of chaffinch songs ranges only from 1 to 6 types of songs (usually 2-3 types). Each song consists of a trill and an ending song flourish. It has been shown that males react more aggressively to a song containing a more complex trill, which may suggest that trill complexity indicates male quality. Therefore, we can expect that signalling of male quality in the chaffinch acts in two dimensions - acoustic and visual, and the information transmitted by these two channels of communication could be correlated with each other. We hypothesise that epaulettes and song in the chaffinch are reliable signals of quality in male-male interactions during thebreeding territory defence. It is believed that it is only multiple ornaments that reflect different aspects of individual quality and allow a more accurate assessment of quality. To determine the relationship between aggressive behaviour and quality in social signalling in male chaffinches, we will measure phenotypic characters, assess MHC (Major Histocompatibility Complex) genes polymorphism and parasite load. We expect that males with larger epaulettes and more complex song would be less infected with malaria-like parasites and show a higher MHC polymorphism

The signalling of good genes, good skills and personality: bird coloration and song as models

Principal researcher: Juan Carlos Senar

Period: 2009-2013

Although the evolution of sexual signalling has recently attracted a great deal of interest in evolutionary biology, several key points remain unresolved. The first one relates to how signal reliability is maintained. Although several mechanisms have been suggested, the topic is highly controversial. One of the main aims of the project is to investigate experimentally, mechanisms to maintain the honesty of sexual and social signals. A second key unresolved topic relates to understanding what kind of benefits signal receivers may acquire and which is the information encoded in signals, especially from a genetic point of view. Our aim is to relate the major histocompatibility gene complex (MHC) to plumage coloration and bird song, which can have inferences for the good-genes hypothesis. A third key unresolved topic relates to the evolution of multiple signals of male quality. If signals can encode different information and these are uncorrelated, it is reasonable to predict that different units of information can be signalled by different ornaments/armaments. Our aim is to provide experimental data on how different patches of plumage colours within an individual or even different qualities of the same patch (i.e. hue and chroma) can provide different units of information. Because individual differences in social behaviour (i.e. personality) may have consequences for mate and group companion choice and sexual/social signalling, we predict that partners should develop preferences for personalities that maximize reproductive output and individual fitness. Hence, our final aim is to relate variation in plumage coloration and song, within the framework of multiple signals, to avian personalities and hence, to the evolution of strategies and signalling.

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