Showing posts with label herbivory. Show all posts
Showing posts with label herbivory. Show all posts

Tuesday, January 19, 2010

Timing is everything: global warming and the timing of species interactions

ResearchBlogging.orgWhile an obvious affect of climate change will be changes in the distributions or range sizes of species, more insidious and likely more consequential will be how species interactions are affected by changes in the timing of growth and reproduction. These changes in an organism's life cycle, or phenology, can create mismatches between an organism's need and resource availability or the readiness of coevolved partners -such as plants and pollinators.

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

Wednesday, September 9, 2009

Exploring ecology through GMOs

This year's Tansley Lecture at the BES meeting was a superb presentation given by Ian Baldwin from the Max Planck Institute for Chemical Ecology. He was enjoyable to watch as his folksy, mid-western American style disarmed the listener and leaving them unprepared for his ascorbic wit and, at times, controversial message. Prof. Baldwin* is a chemical ecologist who studies plant biochemical and physiological processes and their interaction with herbivores. Through his use of molecular tools and superb natural history, he has gained new insights into how and why plants respond to herbivory. He has discovered the pathways allowing wild tobacco, Nicotiana attenuata, to detect chemicals in tobacco hornworm spit and the resulting chemical defense response. More than this though, part of his talk was about the use of transformed plants to study this plant defense response. Using genetic tools, his group was able to knockout certain segments of these biochemical pathways in order to determine how various chemicals affected hornworms. He showed chemical responses involved signaling hornworm predators whereas other responses directly targeted wornworm's ability to digest plant material.

I think that ecologists are often wary of GMOs and his talk was a convincing case for their use in basic research, and he advocated for a more reasoned approach to their use.

*Note: He has run into trouble with German authorities over using the title 'Dr.' -see here.

Monday, May 18, 2009

It's not me, It's you: self recognition and plant responses to herbivory

Many multicellular organisms have the ability to distinguish self and non-self. This is clear in animals, but is not so well documented in plants. A recent experiment published in Ecology Letters by Karban and Shiojiri clearly demonstrate that self recognition in plants can affect their response against herbivores. This very elegant experiment compared herbivory rates of plants growing near clipped clones of the same plants (themselves), and clipped individuals of non-self plants. Clipping is a standard way to mimic herbivory; plants grew in pots so they couldn’t communicate via roots and they did not touch each other. They found that plants that grew by a clipped clone had 42% less herbivory than plants growing by a non-clone. This is strong evidence that plants growing near clones (themselves) responded more effectively to volatiles cues compared to plants growing near a genetically different individuals. This study sheds light on the effects of communication among plants, which is clearly a topic that needs to be more explored, and that could be crucial to understand some ecological and evolutionary processes.

Karban, R., & Shiojiri, K. (2009). Self-recognition affects plant communication and defense Ecology Letters, 12 (6), 502-506 DOI: 10.1111/j.1461-0248.2009.01313.x