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.
No comments:
Post a Comment