ESA 2013, day 3: Like a kid in a candy store.

Sometimes there are moments in my career where feel truly fortunate. Today I was fortunate enough to be a speaker in a session on evolution, biodiversity and ecosystem function. The other talks in this session were outstanding, full of amazing insights into how historical evolutionary dynamics affect modern-day ecological patterns. The presentations were followed by a fantastic panel discussion stimulated by thoughtful questions from the audience. The talks covered a range of topics from including species interactions in models of evolutionary change to using traits to understand coexistence to trying to find patterns when close relatives do not coexist.

The first talk from Luke Harmon on finding phylogenetic signatures on species interactions was incredible. He is an entertaining speaker and included references to his kids finding leaf cutter ants.  He show us how one could fit phylogenetic models that include coevolution. The negative effects of coevolution should affect trait evolution and one should see this signature in variance-covariance matrices. Random evolutionary change generates covariance between species. Stabilizing selection will remove this covariance, while with competition there should be negative covariances apparent. From models we see an interesting signature where older species are able to diverge and fill niche space (thus diverging rapidly) while later species are constrained in their evolution (thus remaining similar). Older species can contribute more to ecosystem function because of historical competitive effects.

Next was Nathan Kraft talking about how traits can potential shed light on fitness and niche differences in coexisting species. In a plant experiment with focal species grown alone and at different densities with competitors, he showed that very few pairs met the conditions for coexistence. For those that do appear to be able to coexist, no traits were associated with fitness difference, but several traits appeared to be associated with fitness differences. Multivariate analyses  showed that an assortment of five traits collectively appeared to be associated with niche differences. Some of these traits appeared to also explain fitness differences, revealing the complexity in assigning traits to specific ecological effects.

In Jeannine Cavender-Bares’ talk, she examined how evolutionary transitions in seed dormancy helped explain modern day ecological patterns in the Fabaceae family (the pea and bean family). The Fabaceae includes species that have dormant and non-dormant  seeds. Dormancy should be favored in certain environments (e.g., less predictable and poor environments). Large seeds are much less likely to be dormant, as well as those occurring at lower latitudes. Historical transitions in dormancy seemed to be correlated with changes in temperature lineages experienced.

Finally, Sharon Strauss critically examine dhow to separate history form ecology. We need to be cognizant of scale effects, where larger scale observations will include more close relatives than we usually see at local scales. Communities contain ‘ghosts’ of past competition and assembly. If species originate allopatrically (in separate places), then we expect that close relatives should not coexist, which can skew our inference about how ecological differences have evolved. Within habitats we seldom see closely related species coexisting . She gave a number of great Californian examples of species appearing to co-occur at large scales but not locally. For example, Limnanthes plants occur in the same region but species never co-occur in the same vernal pool.

These talks represent the collective excitement about the fact that we are entering a new synthesis in ecology. Evolution is required to understand ecological patters and ecological interactions are need for understanding evolutionary change. These talks exhibited where the forefront of this synthesis is, and it was a great afternoon of talks.

ESA Day 2: The problem with statistics...

These are just my favourite quotes from talks on day two of ESA:

(All from great, but anonymous, speakers)

After showing the results of a spatial statistics test: "...But still I was worried because that would be using statistics to prove something and that feels wrong."

On being asked how the speaker quantified earthworm abundance: "I used a non-invasive electroshock technique".
(I'm sure this is normal procedure, it just sounds hilarious to the uninformed).

ESA day 2: The shampoo salesman and new questions.

Day two started off on a high note with Bernhard Schmid's talk on evolution in biodiversity-ecosystem function (BEF) experiments. He is one of the originators of the Jena biodiveristy experiment, for years they have been maintaining plant species in monocultures and in polycultures to assess how much more ecosystem function is produced by multi-species assemblages over single species monocultures. However, it occurred to Schmid that species in these two contexts face different pressures, which may have resulted in evolutionary changes. In monocultures, species face high intraspecific densities and thus competition is severe, as is negative indirect effects like pathogen sharing and herbivory rates. Within polycultures, intrraspecific interactions may involve niche differences, with opportunities for character divergence to further stabilize coexistence. He reported on an experiment that took seeds and cuttings from monoculture and polyculture populations and grew then in monoculture or polyculture. He showed that individuals originating from monoculture did better in monoculture and species originating from polyculture did better in polyculture. The implications are fascinating. If the rate of evolutionary change in performance are equivalent between monocultures and polycultures, the BEF relationships should remain constant. However, if the rates of change are greater for polyculture populations the BEF relationship should get stronger over time. Conversely, BEF relationships should became weaker if higher evolutionary change in monoculture. 

It was hard to top this talk, but there were several other impressive talks as well. Jacob Vander Laan used a country-wide dataset on aquatic insect diversity across the USA and showed that at larger scales, beta-diversity decreases with connectivity, but is seemingly unaffected by environmental heterogeneity.

Restoration is community assembly with management goals and Emily Grman gave an interesting talk on assessing the success of prairie restoration by accounting for management activities, landscape, historical and local abiotic factors. She showed that management activities were the most important, with species-rich sowings result in rich communities, even though many of the species are not those in the sown mixture. Sowing a high diversity of grasses did not increase diversity, but high diversity of forbes did. Other factors like landscape influences and local factors were not important.

Will Pearse examined plant diversity patterns and homogenization across six large urban centres. He showed that there has been little taxonomic homogenization, but substantial phylogenetic and moderate functional trait homogenization. Beyond the interesting questions about how urban centres may cause biotic homogenization is the new tools that Pearse created for these analyses, and that are available online. As a self described 'shampoo salesman', he created a general tool called Phylogenerator that creates a pipeline that makes estimating trees form sequence data more efficient -definitely a tool that ecologists should be using. He further created a way to quantify complex leaf shapes and has a tool available for that, called Stalkless.

All in all , this was a good day, one that has stimulated new questions and approaches. These talks got me thinking about some of my data and experiments and how I can extend them to new questions. 

ESA 2013 Day 1: Temporal variation, roller derby, and topics in between

With day 1 over, ESA 2013 was off to an excellent start. Minneapolis seems like a very friendly place, and I enjoyed perhaps the most chatty bus ride I've ever experienced. As always, I failed to determine the best point on the trade off plot between cherry-picking certain talks based on topic, speaker and friends, and staying put in a session with an interesting topic. Nonetheless I managed to see some really good talks.

Among them, I saw Lauren Shoemaker in the Theoretical Ecology section, who illustrated how to model the four metacommunity paradigms (I.e. species sorting, mass effects, neutral, and patch dynamics) with the Chessonian framework of equalizing and stabilizing forces. She illustrated how both deterministic and stochastic models could replicate dynamics from the four paradigms. This suggests that rather than the usual description of the neutral paradigm as stochastic and the mass effect and species sorting paradigms as niche-based and therefore deterministic, the terms niche and deterministic and neutral and stochastic should not be synonymous. Rather, in the Chessonian framework, fitness differences drive neutral-type dynamics and spatial niches structure the species sorting and mass effects paradigms. More importantly, the results show how the paradigms are just a few sets of points on the much broader set of parameter values that could describe metacommunity dynamics.

It must be funny for Peter Chesson to follow up a talk in which his name is used as an adjective. After the talk on the Chessonian framework, he spoke about the fact that environment is fluid and non-stationary, yet models of communities have almost always treated it as being at equilibrium. Since it is not, ideally models of community dynamics would begin to incorporate environmental variation, and ask questions more relevant to non-equilibrium systems. For example: when is long-term persistence expected, given this non-stationarity and can communities in a non-stationary system still be stable? He showed that including environmental fluidity into models doesn't mean that communities are necessarily unstable, for example, when spatial and temporal trends of environmental variation match, communities may be stationary.

In another of many good talks about temporal variation (seemingly a popular topic of late), Colin Kremer showed that altering the basic characteristics of abiotic temporal variation (amplitude, means, periodicity) changed the amount of diversity present as communities evolved over time. Temporal variation isn't a simple concept anymore than spatial variability is - it has different characteristics with different effects on ecological dynamics and needs to be considered in greater depth.

My biggest disappointment was that I had a time conflict and couldn't attend a talk titled "Significant changes in the skin microbiome mediated by the sport of roller derby".  No doubt I would have learned a lot.

EEB & Flow on summer vacation

We will be back in time to blog from the Ecological Society of America's annual meeting in Minneapolis (Aug 4-9)!

Carnival of Evolution is up!

The latest Carnival of Evolution (#61 if you are keeping track) is up and running at Teaching Biology. It is the Crustie Lovin' Edition.