Wednesday, February 10, 2010
Research blogging awards; and thanks
Monday, February 8, 2010
Predator-human conflict: the emergence of a primordial fear?
Such is the case for three recent animal attacks in Canada. In late October, 2009 in Nova Scotia, a raising 19-year old folk singer was killed by a couple of coyotes while hiking. It is difficult to find meaning in such a horrendous death, but the narrative, told by reporters, was essentially to rest assured that one of the coyotes had been killed and the other was being tracked and would be destroyed. There were two cougar attacks in early January, 2010 in British Columbia, that basically ended with the same reassurance. In the first, a boy was attacked and his pet golden retriever courageously saved his life. A police officer arrived a shot the cougar which was mauling the dog -an obviously legitimate response, and the news story again reassures us that the animal was destroyed. And don't worry the hero dog survived. In the second cougar attack, another boy was attacked, and this time his mother saved his life. But again the story narrative ended by reassuring us that the guilty cougar, and another cat for good measure, were destroyed the next day.
After reading these stories, I asked myself two things. Why is our response to destroy predators that attack? And why do we need to be reassured that this has happened? In defence of the predators, they are just doing what their instincts tell them to do, and most often their only mistake is that they selected their prey poorly. But the reality is that there are only 2-4 cougar attacks per year and only 18 fatalities over the past 100 years. Why do we fear such a low probability event? In contrast, automobile accidents are the leading cause of death in children under 12 in North America. Thousands of people die, and millions injured in car accidents every year in North America. Recently, in Toronto, were I live, 10 pedestrians were killed in 10 days, yet my heart doesn't race when I cross a street. If our fears and responses to human injury and death reflected the actual major risks, we would invoke restrictive rules regarding automobile use.
We believe that we can live with nature in our backyard. But when that close contact results in an animal attack, human fear seems to dictate an irrational response. Do we really expect predators to obey our rules? Can we punish them enough to effectively tame them? We cannot, and I hope that our approaches to dealing with human-animal conflict can better deal with animal attacks, in a way that does not subjugate large predators to whims of our fears.
Wednesday, February 3, 2010
The evolution of a symbiont
In a recent paper, Marchetti and colleagues answer part of the question. They experimentally manipulate a pathogenic bacteria and observe it turning into a symbiont. They transferred a plasmid from the symbiotic nitrogen fixing Cupriavidus taiwanensis into Ralstonia solanacearum and infected Mimosa roots with it. Plasmid transfer among distinct bacteria species is common and referred to horizontal genetic transfer (as opposed to vertical, which is the transfer to daughter cells). The presence of the plasmid caused R. solanacearum to quickly evolve into a root-nodulating symbiont. Two regulatory genes lost function, and this caused R. solanacearum to form nodules and to impregnate Mimosa root cells.
This extremely novel experiment reveals how horizontal gene transfer can supply the impetus for rapid evolution from being a pathogen to a symbiont. More importantly it reveals that sometimes just a few steps are required for this transition and how distantly-related bacterial species can acquire symbiotic behaviors.
Marchetti, M., Capela, D., Glew, M., Cruveiller, S., Chane-Woon-Ming, B., Gris, C., Timmers, T., Poinsot, V., Gilbert, L., Heeb, P., Médigue, C., Batut, J., & Masson-Boivin, C. (2010). Experimental Evolution of a Plant Pathogen into a Legume Symbiont PLoS Biology, 8 (1) DOI: 10.1371/journal.pbio.1000280
Wednesday, January 27, 2010
To intervene or not to intervene: this is a real question
doi: 10.1890/090089
http://www.esajournals.org/doi/abs/10.1890/090089
Tuesday, January 19, 2010
Timing is everything: global warming and the timing of species interactions
In an 'Idea and Perspective' paper in Ecology Letters, Louie Yang and Volker Rudolf set out a new framework to examine the effects of phenological shifts on species interactions. They argue that one cannot understand or predict the fitness consequences of a phenology shift without knowing how interacting species' phenologies are also influenced by environmental changes. The consequences of phenological shifts are changes in fitness, and the question is: how would one go about assessing the fitness effects of phenological changes on interactions? This is where this paper really hits its stride. Yang and Rudolf set out a new conceptual framework for studying the fitness consequences of phenological shifts. They make the case that an experimental approach is required to test the three likely scenarios. The first is that there are no changes in phenology -that is, measuring the fitness levels of the two interacting species under stable conditions. Second, you induce an experimental shift in the timing of one of the species. For example, in a plant-herbivore interaction, germinate the plant earlier and when the herbivore normally has access to the plant, the plant will be older. What are the fitness changes associated with this shift? Finally, you can shift the timing of the other species relative to the first. In our example, the herbivore has access to younger plants and again are there fitness consequences?
Yang and Rudolf call the full combination of possible fitness effects, across a number of timing mismatches, 'the ontogeny-phenology landscape'. By mapping fitness changes across this ontogeny-phenology landscape, researchers can offer better predictions, on top of just changes in range size or habitat use, about the possible affects of climate change. The obvious question, and Yang and Rudolf acknowledge this, is how to extend two-species ontogeny-phenology to multi-species communities. Of course, extending two-species interactions to communities is a question that plagues most of community ecology, but I think the solution is that researchers who know their systems often have intuition about the major players, and thus those species where phenology shifts should have disproportionate effects on other species. Such species could be the place to start. Another strategy would be a food web type approach, where species are lumped into broader trophic groups and we ask how shifts in certain trophic groups affect other groups.
Regardless of how to extend this framework to multispecies assemblages, I see this paper as likely to be very influential. It gives researches a new focus and framework, where specific predictions about climate change can be made.
Yang, L., & Rudolf, V. (2010). Phenology, ontogeny and the effects of climate change on the timing of species interactions Ecology Letters, 13 (1), 1-10 DOI: 10.1111/j.1461-0248.2009.01402.x
Thursday, January 14, 2010
Plant genotypic diversity supports pollinator diversity
In a recent paper in PLoS ONE, Genung and colleagues test whether plant genotypic diversity affects pollinator visits. They use an experimental system set-up by Greg Crutsinger that combines multiple genotypes of the goldenrod, Solidago altissima, and record pollinator visits over two years. Experimental plots contained 1, 3, 6, or 12 genotypes of S. altissima. After accounting for differences in abundance, Genung et al. show that as genotypic diversity increases, both pollinator richness and number of visits to the plot significantly increase. This increase is greater than expectations of randomly simulated assemblages combining proportional pollinator visits from monocultures.
The previous research at the species-level has made a persuasive rationale to protect species diversity in order to maintain ecosystem functioning. Now, research like this is making a case that there are consequences for not explicitly considering genetic diversity in conservation planning and habitat restoration.
Genung, M., Lessard, J., Brown, C., Bunn, W., Cregger, M., Reynolds, W., Felker-Quinn, E., Stevenson, M., Hartley, A., Crutsinger, G., Schweitzer, J., & Bailey, J. (2010). Non-Additive Effects of Genotypic Diversity Increase Floral Abundance and Abundance of Floral Visitors PLoS ONE, 5 (1) DOI: 10.1371/journal.pone.0008711
Thursday, January 7, 2010
Double or nothing
Tuesday, January 5, 2010
Predicting invader success requires integrating ecological and land use patterns.
In the quest to understand species invasions, we often try to link the abundance and distribution of invaders to underlying ecological processes. For example, oft-studied are the links between exotic diversity and native richness or environmental heterogeneity. Seemingly independently, research into how specific land use or management activities affect invasion dynamics is also fairly common. While both research strategies are of fundamental importance, not often recognized, or at least explicitly studied, is that both ecological patterns and management activities simultaneously affect invasion success. Thus a truly integrative approach to understanding invader success must take into account variation in ecological communities and abiotic resource avalibility as well as land use patterns at multiple spatial scales. Such an approach is necessary if ecologists wish to predict potential invader abundance, spread and impact.
Diez et al. Examine how environmental and management heterogeneity interact to influence patterns of Hieracium pilosella (Asteraceae) inasions in the South Island of New Zealand. The spread of H. Pilosella in New Zealand is threatening native habitats (tussock fields) and the livestock grazing industry. Diez et al. Asked how environmental and management regimes affect H. Pilosella abundance and distribution across six large farms on the South Island. This is an interesting and important question, not just because they are examining how human-caused and ecological variation interact to affect H. Pilosella dynamics, but also because these sources are heterogeneity are realized at different spatial scales.
Diez et al. show that the abundance and distribution of H. Pilosella was significantly affected by the interaction of habitat type (i.e., short vs. tall tussocks) and farm management strategies (i.e., fertilization and grazing rates). At larger scales, H. Pilosella was more abundant in tall tussock habitats and was unaffected by fertilization, while in short tussocks, it was less abundant in fertilized patches. At small scales, H. Pilosella was less likely to be found in short tussocks with high exotic grass cover and high productivity (measured as site soil moisture and solar radiation). Conversely, in tall tussocks, H. Pilosella was more likely to be found on sites with high natural productivity. Diez et al. were able to tease these complex causal mechanism apart by using Bayesian multilevel linear models, for which they included example R code in an online appendix.
While it is a truism in ecology to say that heterogeneity affects ecological patterns, this paper deserves mention because they convincingly show that the spread of noxious exotic plants in a complex landscape, can potentially predicted by understanding the invader success in different habitat types and land management strategies. In their case they show how human activities, which were not designed to affect H. Pilosella, can strongly affect abundance in different habitat types. This type of approach to understanding invader dynamics can potentially arm managers with the ability to use existing land use strategies to predict how and where further invader targeting would be most useful.
Diez, J., Buckley, H., Case, B., Harsch, M., Sciligo, A., Wangen, S., & Duncan, R. (2009). Interacting effects of management and environmental variability at multiple scales on invasive species distributions Journal of Applied Ecology DOI: 10.1111/j.1365-2664.2009.01725.x
Wednesday, December 30, 2009
1st anniversary!
Thanks!
Wednesday, December 16, 2009
Parasite competition enhances host survival
This was the premise of a recent paper by Oliver Balmer and colleagues, studying trypanosome infection of mice hosts. They engineered two transgeneic strains of the protozoan parasite, Trypanosoma brucei (African sleeping sickness), to fluoresce different colors in order to assess infections. They infected mice with each strain separately and together and measured host survival and parasite density.
They found that when both strains were present, they competitively suppressed each other and that the level of suppression depended on the initial density of each strain. One of the strains was more virulent than the other, and infection by both strains reduced mortality by 15% compared to infection by the virulent strain only. This is due to the suppression of the virulent strain by the low virulent strain.
The authors argue that strain source and intraspecific genetic diversity can have an important effect on host mortality. I would also argue that understanding interspecific interactions and within-host niche differences, would also be critical.
What a cool use of molecular technology to test basic hypotheses about disease ecology.
Balmer, O., Stearns, S., Schötzau, A., & Brun, R. (2009). Intraspecific competition between co-infecting parasite strains enhances host survival in African trypanosomes Ecology, 90 (12), 3367-3378 DOI: 10.1890/08-2291.1