Intensive Farming: Evolutionary Implications for Parasites and Pathogens

An increasing number of scientists have recently raised concerns about the threat posed by human intervention on the evolution of parasites and disease agents. New parasites (including pathogens) keep emerging and parasites which previously were considered to be ‘under control’ are re-emerging, sometimes in highly virulent forms. This re-emergence may be parasite evolution, driven by human activity, including ecological changes related to modern agricultural practices. Intensive farming creates conditions for parasite growth and transmission drastically different from what parasites experience in wild host populations and may therefore alter selection on various traits, such as life-history traits and virulence. Although recent epidemic outbreaks highlight the risks associated with intensive farming practices, most work has focused on reducing the short-term economic losses imposed by parasites, such as application of chemotherapy. Most of the research on parasite evolution has been conducted using laboratory model systems, often unrelated to economically important systems. Here, we review the possible evolutionary consequences of intensive farming by relating current knowledge of the evolution of parasite life-history and virulence with specific conditions experienced by parasites on farms. We show that intensive farming practices are likely to select for fast-growing, early-transmitted, and hence probably more virulent parasites. As an illustration, we consider the case of the fish farming industry, a branch of intensive farming which has dramatically expanded recently and present evidence that supports the idea that intensive farming conditions increase parasite virulence. We suggest that more studies should focus on the impact of intensive farming on parasite evolution in order to build currently lacking, but necessary bridges between academia and decision-makers

Local Individual Preferences for Nest Materials in a Passerine Bird

Variation in the behavioural repertoire of animals is acquired by learning in a range of animal species. In nest-building birds, the assemblage of nest materials in an appropriate structure is often typical of a bird genus or species. Yet plasticity in the selection of nest materials may be beneficial because the nature and abundance of nest materials vary across habitats. Such plasticity can be learned, either individually or socially. In Corsican populations of blue tits Cyanistes caeruleus, females regularly add in their nests fragments of several species of aromatic plants during the whole breeding period. The selected plants represent a small fraction of the species present in the environment and have positive effects on nestlings.We investigated spatiotemporal variations of this behaviour to test whether the aromatic plant species composition in nests depends on 1) plant availability in territories, 2) female experience or 3) female identity. Our results indicate that territory plays a very marginal role in the aromatic plant species composition of nests. Female experience is not related to a change in nest plant composition. Actually, this composition clearly depends on female identity, i.e. results from individual preferences which, furthermore, are repeatable both within and across years. A puzzling fact is the strong difference in plant species composition of nests across distinct study plots.This study demonstrates that plant species composition of nests results from individual preferences that are homogeneous within study plots. We propose several hypotheses to interpret this pattern of spatial variation before discussing them in the light of preliminary results. As a conclusion, we cannot exclude the possibility of social transmission of individual preferences for aromatic plants. This is an exciting perspective for further work in birds, where nest construction behaviour has classically been considered as a stereotypic behaviour

Extra-pair paternity explains cooperation in a bird species

In many social animals, females mate with multiple males, but the adaptive value of female extra-pair mating is not fully understood. Here, we tested whether male pied flycatchers (Ficedula hypoleuca) engaging in extra-pair copulations with neighboring females were more likely to assist their neighbors in antipredator defense. We found that extra-pair sires joined predator-mobbing more often, approached predators more closely, and attacked predators more aggressively than males without extra-pair offspring in the neighboring nest. Extra-pair mating may incentivize males to assist in nest defense because of the benefits that this cooperative behavior has on their total offspring production. For females, this mating strategy may help recruit more males to join in antipredator defense, offering better protection and ultimately improving reproductive success. Our results suggest a simple mechanism by which extra-pair mating can improve reproductive success in breeding birds. In summary, males siring extra-pair offspring in neighboring nests assist neighbors in antipredator defense more often than males without extra-pair offspring.</p

The response of interacting species to biotic seasonal cues

A recommendation – based on reviews by Anne Duplouy and one anonymous reviewer – of the article: Tougeron K., Brodeur J., van Baaren J., Renault D. and Le Lann C. (2019). Sex makes them sleepy: host reproductive status induces diapause in a parasitoid population experiencing harsh winters. bioRxiv 371385, ver. 6 peer-reviewed and recommended by PCI Ecology. doi: 10.1101/37138

Data: Methods for tagging an ectoparasite, the salmon louse Lepeophtheirus salmonis

&lt;p&gt;Monitoring individuals within populations is a cornerstone in evolutionary ecology, yet&lt;span&gt; &lt;/span&gt;individual tracking of invertebrates and particularly parasitic organisms remains rare. To address this gap, we describe here a method for attaching radio frequency identification&lt;span&gt; &lt;/span&gt;(RFID) tags to individual adult females of a marine ectoparasite, the salmon louse&lt;span&gt; &lt;/span&gt;&lt;em&gt;&lt;span&gt;Lepeophtheirus salmonis&lt;/span&gt;&lt;/em&gt;. Comparing two alternative types of glue, we found that one of them&lt;span&gt; &lt;/span&gt;(2-octyl cyanoacrylate, &lt;em&gt;&lt;span&gt;2oc&lt;/span&gt;&lt;/em&gt;) gave a significantly higher tag retention rate than the other (ethyl&lt;span&gt; &lt;/span&gt;2-cyanoacrylate, &lt;em&gt;&lt;span&gt;e2c&lt;/span&gt;&lt;/em&gt;). This glue comparison test also resulted in a higher loss rate of adult ectoparasites from the population where tagging was done using &lt;em&gt;&lt;span&gt;2oc&lt;/span&gt;&lt;/em&gt;, but this included males&lt;span&gt; &lt;/span&gt;not tagged and thus could also suggest a mere tank effect. Corroborating this, a more extensive analysis using data collected over two years showed no significant difference in&lt;span&gt; &lt;/span&gt;mortality after repeated exposure to the &lt;em&gt;&lt;span&gt;2oc &lt;/span&gt;&lt;/em&gt;glue, nor did it show any significant effect of the&lt;span&gt; &lt;/span&gt;tagging procedure on the reproduction of female salmon lice. The proportion of RFID-tagged&lt;span&gt; &lt;/span&gt;individuals followed a negative exponential decline, with tag retention among the living&lt;span&gt; &lt;/span&gt;female population generally high. The projected retention was found to be about 88% after&lt;span&gt; &lt;/span&gt;30 days or 80% after 60 days, although one of the four batches of glue used, purchased from&lt;span&gt; &lt;/span&gt;a different supplier, appeared to give significantly lower tag retention and with greater initial&lt;span&gt; &lt;/span&gt;loss (74% and 60% respectively). Overall, we find that RFID tagging is a simple and effective technology that enables documenting individual life histories for invertebrates of a suitable size, including marine and parasitic species, and that it can be used over long periods of study.&lt;/p&gt

Evidence of epistasis provides further support to the Red Queen theory of host-parasite coevolution

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all brood data (text file)

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Data for repeated females (present EPP vs past failure)

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