Guest Essay Global hosts and global pathogens: a perspective

Plant species are assailed by a remarkable diversity of pathogens, and these and other pests pose a serious direct risk to collections in botanic gardens as well as a potential source of pathogen escape. The high diversity of species in gardens combined with low population numbers minimises the likelihood of disease spread of specialist pathogens, but importation of novel pathogens is a constant concern. In parallel with natural systems, there is little data on pathogen loads in botanic gardens, on what accession policies minimise these and if such loads are likely to differ by country of origin or plant life form. Nevertheless, commonsense measures such as prohibiting the importation of plants in soil, shifting to seed and in vitro propagation, and inspection and quarantine on receiving and transferring plants should be implemented.This edition of Sibbaldia explores a variety of directions for improving our ability to develop strategies for dealing not just with pathogen threats, but with a more rational approach to pests and to microbial interactions that are a natural part of a plant’s heritage

Sexual Transmission of Disease and Host Mating Systems: Within-Season Reproductive Success

While there is an extensive literature on the evolution of mating systems in animals, little consideration has been given to the possible evolutionary interactions between sexually transmitted pathogens and the mating systems of their hosts. We use individual-based models that incorporate measurable per-contact probabilities of infection and fertilization to show that not only can the presence of sexually transmitted (and sterilizing) pathogen have significant effects on optimal within-season mating strategies for both males and females. We show that, contrary to expectations, monogamy is not always predicted to be the optimal strategy. The optimal strategy may also often differ between the two sexes, and the optimal strategy will not always be the one that minimizes disease transmission. Similarly, we show that the optimal level of virulence for a sexually transmitted pathogen is a function of the degree of promiscuity of its host. Overall, these results suggest that sexually transmitted diseases can impact host mating behavior, often in nonintuitive directions

EXPERIMENTAL ECOLOGICAL GENETICS IN PLANTAGO. III. GENETIC VARIATION AND DEMOGRAPHY IN RELATION TO SURVIVAL OF PLANTAGO CORDATA, A RARE SPECIES

ABSTRACT Plantago cordata, the heart-leaved plantain, is a species of woodland streams that was Jbrmerly widespread in the easter

A translation of the Linnaean dissertation The Invisible World

This study presents the first translation from Latin to English of the Linnaean dissertation Mundus invisibilis or The Invisible World, submitted by Johannes Roos in 1769. The dissertation highlights Linnaeus's conviction that infectious diseases could be transmitted by living organisms, too small to be seen. Biographies of Linnaeus often fail to mention that Linnaeus was correct in ascribing the cause of diseases such as measles, smallpox and syphilis to living organisms. The dissertation itself reviews the work of many microscopists, especially on zoophytes and insects, marvelling at the many unexpected discoveries. It then discusses and quotes at length the observations of Münchhausen suggesting that spores from fungi causing plant diseases germinate to produce animalcules, an observation that Linnaeus claimed to have confirmed. The dissertation then draws parallels between these findings and the contagiousness of many human diseases, and urges further studies of this 'invisible world' since, as Roos avers, microscopic organisms may cause more destruction than occurs in all wars.https://www.cambridge.org/core/journals/british-journal-for-the-history-of-scienceAncient Language

Antihelmintic treatment alters the parasite community in a wild mouse host

Individuals are often co-infected with several parasite species, yet the consequences of drug treatment on the dynamics of parasite communities in wild populations have rarely been measured. Here, we experimentally reduced nematode infection in a wild mouse population and measured the effects on other non-target parasites. A single oral dose of the anthelmintic, ivermectin, significantly reduced nematode infection, but resulted in a reciprocal increase in other gastrointestinal parasites, specifically coccidial protozoans and cestodes. These results highlight the possibility that drug therapy may have unintended consequences for non-target parasites and that host–parasite dynamics cannot always be fully understood in the framework of single host–parasite interactions

Population Dynamics and Genetics of Plant Disease: A Case Study of Anther-Smut Disease

This is the publisher's version, also available electronically from http://www.jstor.org/stable/info/2265569A model by Levin and Udovic (1977) emphasizes the need for integration of studies of the numerical abundances and genetic composition of host and pathogen species. We use their conceptual framework to summarize our collaborative research on the ecological genetics of the anther-smut disease of Silene alba caused by the fungus Ustilago violacea. Our theoretical investigations have revealed the importance of the rate and mode of disease transmission on the likelihood of coexistence between host and pathogen. Our empirical studies have quantified patterns of disease spread on local and regional spatial scales and have shown that host genotypes differ greatly in resistance. Comparable genetic variation in pathogen virulence has not yet been demonstrated. The genetic composition of host populations alters numerical dynamics in experimental populations: disease declines in resistant populations, while host and pathogen appear to coexist in susceptible populations. Ecological outcomes also may be affected by the negative relationship between disease incidence and host flowering time, which may constitute a "cost" to resistance. We are currently expanding our work on the ecology and genetics of metapopulation dynamics of host and pathogen