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Fireweed (Senecio madagascariensis) is a noxious and invasive weed affecting pastures in Hawaii, Australia, and South America. Fireweed contains compounds called pyrrolizidine alkaloids that are toxic to most grazing mammals. Toxic effects to cattle include irreversible damage to liver cells, hardening of the liver, and loss of liver function, which may lead to jaundice, swelling, and the accumulation of fluids in the stomach and other physiological malfunctions. External effects include rough appearance, diarrhea, low energy and dullness, photosensitization, and abnormal behavior, many of which can lead to death. Fireweed also can reduce pasture productivity by as much as 30-40%, particularly in Hawaii. As a result of these adverse effects on cattle and pasture production, people are seeking ways to manage fireweed and cattle. Condensed tannins, which are common in many forage legumes, bind with other molecules such as protein and alkaloids. Complementarities among secondary compounds such as condensed tannins and alkaloids can allow animals to consume more of plant material they would otherwise avoid due to toxicity; however, there is very little information on whether tannins actually protect animals from the toxic effect of alkaloids like the ones found in fireweed. The effects of condensed tannins on the toxicity of fireweed to cattle were examined in two stages of a research project that included studies in the lab (in vitro) and in live animals (in vivo). The in vitro studies showed that tannins bound pyrrolizidine alkaloids in cattle rumen fluid and binding was highest when mixed with tannins at 8%, with some effect at 12% as well, by weight of fireweed. The in vivo studies were inconclusive as animals from both the Fireweed and Fireweed-Tannin group demonstrated ill-effects brought on by the fireweed. The data gathered in the form of blood tests and liver tests did not identify a clear protective effect provided by having tannin in the diet, but the results likely were affected by the way we conducted the research, which involved dosing animals daily with large amounts of plant material. The findings also illustrate how strongly cattle avoid eating fireweed while grazing on pasture. In summary, management to reduce fireweed effects on cattle should focus on improving pasture diversity and resiliency, on multi-species grazing to take advantage of the innate resistance of sheep and goats to fireweed’s toxicity, and on ways to enable cattle to utilize fireweed.

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The co-occurrence of polyploidy and clonal reproduction among plant species has long been recognized, but the evolutionary mechanisms underlying the association are unknown. Here, I investigate whether polyploidy increases the magnitude of clonality, either directly or indirectly, by comparing the extent and spatial structure of clones between diploid and tetraploid Chamerion angustifolium in a greenhouse environment and natural populations. In the greenhouse, tetraploid plants allocated 90.4% more dry mass to root buds, the primary mechanism of clonal reproduction, than diploids. Per unit root mass, tetraploids produced 44% fewer root buds and the average position of the root buds along the root was 47% closer to the stem than in diploids. In natural populations, the magnitude of clonality in tetraploid C. angustifolium was similar or less than in diploids. However, clones were spatially aggregated in all diploid populations but only in two of five tetraploid populations. Average clone patch diameter, however, was not significantly different between diploids (3.9 m) and tetraploids (2.5 m). These data do not support the hypothesis that clonality increases as a result of genome duplication. Rather, it is possible that clonality is linked to genome duplication because clonal diploids are predisposed for polyploid formation and establishment. / National Science and Engineering Research Council, Canada Research Chair Program, Canadian Foundation for Innovation