Everything but extinct: invasion impacts on native diversity

There has been a persistent debate in the plant invasions literature about whether exotic plant invasions are a major threat to native plant persistence. While there are clear examples of animal invasions resulting in large scale extinction -e.g., the brown tree snake or Nile perch, evidence has been ambiguous for plants. Most ecologists are not so sanguine as to actually conclude that plant invasions are not a threat, and I think most believe that plant invader effects are an issue of temporal and spatial scale and that the worst is yet to come.

In a forthcoming paper from Heinke Jäger and colleagues in the Journal of Ecology, Cinchona pubescens invasions on the Galápagos Islands were monitored in long-term plots for more than seven years. What they found was that there was a four-fold increase in Cinchona density as the invasion progressed and that this increase had measurable effects on native species abundance. While they did not observe any native extirpations in their plots, native densities decreased by at least 50%. Of the greatest concern was that Island endemics appear to the most susceptible to this invasion.

What these results show is that, while there were not any observed extinctions, there were serious deleterious changes to native diversity. Further, the native species, and especially the endemics, are now more susceptible to other invasions or disturbances due to their lower abundances. The impact of exotic invaders may not be readily apparent but may be a major contributor to increased extinction risk.

Jäger, H., Kowarik, I., & Tye, A. (2009). Destruction without extinction: long-term impacts of an invasive tree species on Galápagos highland vegetation Journal of Ecology DOI: 10.1111/j.1365-2745.2009.01578.x

BES day two...

It was a day full of talks, and I really enjoyed being able to spend the whole day just absorbing the presentations. Here are some highlights from today's events:

• Ian Wright gave an interesting talk about the history of functional plant ecology. Basically, covering where trait ecology has been and where we are now. It is really amazing to see the truly large scale analysis and collaborations currently driving modern trait analysis.
• In another overview type talk, Gerlinde De Deyn, talked about carbon sequestration in soils. I'm sure to many ecosystem ecologists this maybe well known, but I found it fascinating. Did you know that tundra ecosystem have as much soil carbon as tropical rain forests? The reason is that tundra has very slow process rates (cold) while rain forests have fast production rates. In fertilization experiments, soil carbon is reduced, so in order to manipulate soil carbon stores one must understand the interaction between plant traits and soil organisms.
• Finally, Kyle Dexter, in a great field survey of Inga tree species in a region of Peru, showed that different functional diversity metrics show differing patterns of over- and under-dispersion. For example, phylogenetic diversity tends to be under-dispersed for Inga assemblages, while chemical and anti-herbivory traits are over dispersed and leaf size measures are under-dispersed.
  

Also, there was the annual general meeting, which was rather somber as three obituaries were read aloud. The three deceased, John Harper, Bob Jefferies and Simon Thirgood, were all superb ecologists who absences were obviously felt. Harper (my Master's advisor's advisor) and Jefferies (my colleague at Toronto) were both eminent ecologists with long and distinguished careers, while Thirgood (a fellow Senior Editor at the Journal of Applied Ecology) was in the prime of his very successful career.

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.

An ecological meeting, British style.

I'm in Hatfield, outside of London, for the British Ecological Society (BES) meeting, and I'll be blogging thoughts, happenings, etc. I posted several observations from the American equivalent (ESA) last month, and one thing is readily apparent, even though talks do not start until tomorrow. While the ESA meeting is a great chance to meet a lot of people and see a lot of talks, at a few thousand conference goers, it can be a bit overwhelming. At any given time the ESA meeting had up to 26 concurrent sessions, which makes for a lot of running around if there are talks you want to see in different sessions. At the BES there is a maximum of 7 concurrent session. The BES is definitely smaller than ESA and the meeting and venue feel compact and intimate. I'm looking forward to experiencing the BES meeting this week.

Check back for more.

Ecology and evolution jobs 2009

After a horrendous year of canceled job searches and a barren landscape lacking many opportunities for academic-track job seekers, the jobs posted this season seem to be a stark contrast. In a previous post, I blogged about the best ecology job wiki, and when you look through last year's job postings you notice that the 'updates' column contains a multitude that had their searches canceled. Most people assumed that there wouldn't be very many tier-one academic jobs this year, but looking at the list of jobs announced so far this year, things look pretty good! I've also caught wind of a few other positions at good institutions that have not yet advertised. Job seekers keep your eyes open, and definitely check the job wiki regularly. This could be your year!

I for one have been (overly) optimistic and really didn't buy the hype that the job market would crash this year and for the foreseeable future. I think that many institutions over-reacted to the recession. Of course some states, like California, are in absolute dire straights. But my feeling is that over the next couple of years many institutions will try to recover from their self-imposed professor deficits, meaning that many similar-sounding job searches will be active at the same time. The net result is that schools will be competing against one another for good researchers.

March of the polyploids!

Speciation by polyploidy (see here for a general description of polyploidy) is one of the mechanisms of speciation and evolutionary diversification. We all learn about it in Bio 101, right after allopatry and sympatry. It is thought to be an especially important driver of speciation in plants, and anecdotal evidence, such as the origination of the invasive polyploid, Spartina anglica in the UK in the 1800's, reinforced that view. But how important has been unanswered until now.

In a new publication in PNAS by Wood et al. -from the Loren Rieseberg lab (one of the best lab homepages BTW) this questions has been answered. The authors go through all available chromosome counts on the Missouri Botanical Garden's Index to Plant Chromosome Numbers, and assess the proportion of polyploid species. They find that about 15% of all angiosperm speciation events coincided with an increase in chromosome number (and about 30% of fern species). Further, about 35% of all genera contain polyploids. Looking across the phylogeny of major plant groups, they find that all major lineages, except Gymnosperms, have significant proportions of polyploids (again with ferns have the greatest proportion). Polyploidy is a ubiquitous feature of plant diversity and a major driver of plant speciation. And now we can quantify just how important.

Wood, T., Takebayashi, N., Barker, M., Mayrose, I., Greenspoon, P., & Rieseberg, L. (2009). The frequency of polyploid speciation in vascular plants Proceedings of the National Academy of Sciences, 106 (33), 13875-13879 DOI: 10.1073/pnas.0811575106