Tuesday, August 25, 2009

March of the polyploids!

ResearchBlogging.orgSpeciation 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

Tuesday, August 18, 2009

Unifying invader success and impact

ResearchBlogging.orgSomething that has continuously bothered me about our collective narrative concerning invasions has been the conflicting processes determining invader success and impact. Numerous studies (including some of my own) show that invaders are successful often because they are different from residents. That is, they are thought to occupy some unique niche. However, occupying a unique niche means that competition is minimized and these successful invaders should have relatively low impact on residents. Conversely, species that have large impacts are thought to be superior competitors, but why are they able to be so successful?

In a new paper in the Journal of Ecology, Andrew MacDougall, Benjamin Gilbert and Jonathan Levin use Peter Chesson's framework where ability for two species to coexistence (or conversely the strength of competitive exclusion) is a process relative to two factors -the magnitude of fitness differences and the degree of resource use overlap. Here competitive exclusion is rapid if species have a large fitness difference and high resource overlap, and slow if fitness differences are low. Species that are successful because of reduced resource overlap likely have little impact unless there are large fitness inequalities.

If we then view the invasions process on a continuum (see figure), then by determining basic fitness and resource use, we can predict success and impact. This is an exciting development and I hope it inspires a new generation of experiments.

MacDougall, A., Gilbert, B., & Levine, J. (2009). Plant invasions and the niche Journal of Ecology, 97 (4), 609-615 DOI: 10.1111/j.1365-2745.2009.01514.x

Thursday, August 6, 2009

Macroecology is dead, long live macroecology!

I went to a session on a macroecology yesterday, which featured some wonderful speakers, and came away with an unsure feeling about this field. The Session started off with a fantastic talk by Rob Dunn on how macroecologists differ on what the main mechanisms are for explaining diversity patterns. He argued that perhaps the complexity of natural and human-altered systems make simple generalizations not very fulfilling. Next Lauren Buckley showed how species turnover had complex relationships with broad environmental changes and that species turnover patterns are better correlated with other species turnover then with the environmental variables we think drive the patterns. Next Brian McGill tried to make the case for a truly unified theory. He walked through several general models of random species packing, showing that some models fit observed data very well. I was impressed by the data/model fits but am skeptical of a general theory which lacks biological mechanisms. My view of a scientific theory is that it ought to contain basic mechanisms and that a unified theory should explain patterns and processes at multiple scales. That said, I also think McGill has done more to forward the field than almost any other younger ecologist. In Allen Hurlbert's talk, he nicely showed how independently accounting for energy and area can provide a better basis to constructing and understanding species-area relationships. The basic reason is that area and energy availability differentially affect the number of individuals.

Back to my real life tomorrow!

Wednesday, August 5, 2009

Pleasant invasions surprise

Normally I run around ESA looking for talks that have the best potential to inform or entertain me. This time around I decided to go to a session on invasions and communities and settle in for the long haul. Am I glad I did. I was afraid the session would be dominated by similar sounding talks, but instead each talk was wildly interesting and different. Talks included looking at the genetic variability of the dominant native resident as a proxy for niche preemption. Another good one looked at the role of propagule pressure for an understory invasion into tropical dry forests -I seldomly hear about invasions into these ecosystems. Next was a look at how invaders behave over long term successional trajectories and they by and large appear to follow native trends. Next was a great modeling talk where individual-based models and riverine networks were used to assess the role of distrubance and trait differences in invasion dynamics. The final one I saw was on how to potentially restore Californian serpetine plant communities using little more that gravel and a few chemicals, with the goal of reintroducing extirpated butterflies, which have not been able to cope with the shift to exotic-dominated grasslands.

I am looking forward to more great talks!

Tuesday, August 4, 2009

Species interactions & evolution

Hi from ESA Albuquerque!

I've been in the organized session on species interactions and evolution all morning and there were some great talks (e.g., Silvertown, Ackerly, Cavender-Bares, etc.). But I think what really got me excited were some of the questions after each talk. Following Jonathan Silvertown's talk, Steve Hubbell asked some questions that get to the heart of addressing what phylogenies mean for community assembly. Silvertown showed that within plots, species of a large South African family of plants in the Fynbos seemed to spatially segragate according to hydrological niches and that within these plots there was a lack of phylogenetic signal in this niche. Hubbell then asked two critical questions: How many other species (in other families) co-occur in these niches and if related species have similar niches at a larger scale. To me this is at the core of uderstanding how phylogenies inform our understanding of community assembly. Basically, what haven't we measured? If we include all sister species into a phylogeny, do we change our understanding of the processes structuring communities?

More later!

Monday, July 27, 2009

Incommunicado Apologies & ESA next week

Dear readers of EEB and flow,

Sorry for the lack of postings as of late. I've just started a professorship, which involved a move from my postdoc in California to my new position in Toronto, Canada, and I guess I failed to completely appreciate how much of a time sink all this would be.

Anyway, I've resurfaced and will be blogging from the ESA annual meeting in Albuquerque next week. I'll be speaking in a workshop on Sunday that deals with whether exotics are different from native species, and there are some great ecologists that will be speaking (like Dov Sax, John Maron, Dave Richardson, Peter Kotanen and John D. Parker). Also, I'm talking in an organized oral session on species interactions and relatedness with a stellar group (e.g., Jeannine Cavender-Bares, Jonathan Silvertown, David Ackerly, Steve Kembel, Jonathan Davies and Andras Prinzing), which is a little daunting. Looking at the schedule, there are way too many interesting talks and my schedule is already double-booked with talks I want to attend. Rock, Paper, Scissors. Should be great time!

Hope to see you in Albuquerque,
Marc

Thursday, June 11, 2009

The sushi of tomorrow… Jellyfish rolls?

With the world’s fisheries teetering on the edge of collapse, familiar items at your local sushi bar might disappear in the near future. One candidate for replacing the Hamachi, Ikura, Maguru, Tai, and Toro on the menu is the jellyfish, which seems to be doing well – too well, actually – in today’s environment.

In recent years, jellyfish outbreaks have become more frequent and more severe. These outbreaks can have lasting ecological and economic consequences. They can wreak havoc on the tourist industry by closing beaches and harming swimmers, cause power outages by blocking cooling intakes at coastal power plants, reduce commercial fish abundance via competition and predation, spread fish parasites, burst fishing nets, and contaminate catches.

A review by Anthony Richardson and his collaborators suggests that human activities such as overfishing, eutrophication, climate change, translocation, and habitat modification have dramatically increased jellyfish numbers. Their research, which was published this week in Trends in Ecology and Evolution, highlights that the structure of pelagic ecosystems can abruptly transition from one that is dominated by fish to one that is dominated by jellyfish.

Richardson and his collaborators present a potential mechanism to explain how local jellyfish aggregations can spread, displace fish, and form an alternative stable state to fish-dominated ecosystems. Jellyfish are like the opportunistic weed of the sea, giving them an edge in environments stressed by climate change, eutrophication, and overfishing. In these disturbed environments, the abundance of jellyfish relative to filter-feeding fish increases until a tipping point is reached. Under normal conditions, filter-feeding fish keep jellyfish populations in check via competition for planktonic food and (perhaps) predation on an early life-stage of the jellyfish. At the tipping point, jellyfish numbers are such that they begin to overwhelm any control of their vulnerable life-cycle stages by fish predators. At the same time, jellyfish progressively eliminate competitors and predators via their predation on fish eggs and larvae. As jellyfish abundance increases, sexual reproduction becomes more efficient, allowing them to infest new habitats where fish might have formally controlled jellyfish numbers.

Richardson and his collaborators suggest that one way to hit the brakes on what they call the “the never-ending jellyfish joyride” is to harvest more jellyfish for human consumption. Jellyfish have been eaten for more than 1000 years in China, where they are often added to salads. In Japan they are served as sushi and in Thailand they are turned into a crunchy noodle concoction. Although the taste and texture of jellyfish might not be appealing to some westerners, I for one have yet to meet a sushi that I didn’t like. Of course, jellyfish harvesting is unlikely to return systems to their fish-dominated state if the stresses that caused the ecosystem shift remain.

Richardson, A. J., A. Bakun, G. C. Hays, and M. J. Gibbons. 2009. The jellyfish joyride: Causes, consequences and management responses to a more gelatinous future. Trends in Ecology and Evolution, 24 (6), 312-322 DOI: 10.1016/j.tree.2009.01.010

Thursday, May 28, 2009

How long does it take for an ecosystem to recover?

ResearchBlogging.orgNumerous human activities, such as logging, fishing, pollution and the introduction of exotic species negatively impact ecosystems around the world. These negative impacts mean ecosystems lose species diversity, biomass production, carbon storage, and nutrient uptake. An important question is, how long does it take for ecosystems to recover from perturbations. The answer to this question can inform conservation policy and strategies and could help focus management resources.

In a recent PLoS ONE paper, Jones and Schmitz attempt to answer this question by reviewing 240 published studies that examine post-disturbance ecosystem diversity and function. While they report that many ecosystems recover on the order of decades and that this is likely more rapid than previously thought, there are some important caveats. First, is that only about half of the 240 studies report a recovered state and either they were not carried out long enough or there are certain types of disturbances or systems where recovery takes much longer. Second is that there are important differences among habitat types. For example benthic algal recovery to hurricanes or oil spills may take 2-10 years, while the recovery of tree diversity to logging may take 20 to 100 years (or more). Thirdly, different measures of ecosystems general resulted in differing recovery times. For example, bird populations may recover quite quickly to logging (likely because they are migratory), whereas soil microbial communities and processes may take many decades due to changes in the soil environment. Finally, the nature of the disturbance can be an important determinant of time to recovery. Logging and agriculture require the greatest recovery time, while large storms and oil spills appear to require relative little time.

While these results may give us a general picture of ecosystem recovery, the data they use highlight the importance of knowing how disturbance type affect recovery and how different ecosystem measures can alter recovery time estimates.

Jones, H., & Schmitz, O. (2009). Rapid Recovery of Damaged Ecosystems PLoS ONE, 4 (5) DOI: 10.1371/journal.pone.0005653

Wednesday, May 20, 2009

Fire and the changing world

ResearchBlogging.orgThis is probably the most appropriate blog I have ever written. My family and I were evacuated two weeks ago because of the Jesusita fire in Santa Barbara, and several homes in our neighborhood were lost. Here in Santa Barbara we have experienced multiple years of extremely large fires, with this last one occurring much earlier than previous fires.

Wildfires have been a part of the Earth’s biota likely since organisms first died and dried on land. Ecosystems have been shaped by fire, numerous organisms have evolved strategies to cope with fire and human cultural development has close tied to fire. In a recent review paper in Science by David Bowman, Jennifer Balch and colleagues, they asked the question: how have fires changed and what does the future look like? Human activities are changing fire patterns and climate change may be entering a feedback with fire. Global warming has been linked to increases in extreme fire weather, making large, destructive fires more probable. However, these large fires feedback into this loop because they release compounds that have strong greenhouse effects. Further, smoke plumes inhibit cloud formation, reinforcing the dry conditions that lead to the fires in the first place.

They argue that fire needs to be incorporating into models of climate change and especially those that link ecosystem properties climate change. Fire may change the distribution of specific habitat types beyond that predicting by responses to climate change alone.

Bowman, D., Balch, J., Artaxo, P., Bond, W., Carlson, J., Cochrane, M., D'Antonio, C., DeFries, R., Doyle, J., Harrison, S., Johnston, F., Keeley, J., Krawchuk, M., Kull, C., Marston, J., Moritz, M., Prentice, I., Roos, C., Scott, A., Swetnam, T., van der Werf, G., & Pyne, S. (2009). Fire in the Earth System Science, 324 (5926), 481-484 DOI: 10.1126/science.1163886

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