Evolution revealed by resurrecting historical resting eggs

Recently published in the January issue of Evolutionary Ecology!

Derry, A.M., S.E. Arnott, and P.T. Boag. 2010. Evolutionary shifts in copepod acid tolerance in an acid-recovering lake indicated by resurrected resting eggs. Evolutionary Ecology 24: 133-145.
http://www.springerlink.com/content/668651t1247q3v18/fulltext.pdf

Long-lived resting eggs of zooplankton are an ecological and evolutionary reservoir that can impact population and community responses to environmental change in lake ecosystems.
I investigated if adaptive shifts in copepod acid tolerance had arisen over a century of environmental change in an acid-recovering lake by resurrecting resting eggs dating from the late 1800s to present. My results suggest that copepods underwent shifts in acid tolerance following both anthropogenic acidification and pH recovery. Further, I found evidence to suggest that maternal effects (the effects of female body condition on the fitness of their offspring) can have an important role for the fitness of older zooplankton genotypes, irrespective of egg age, when historic resting eggs are given an opportunity to hatch into contemporary communities. Adaptive responses through time are important to consider because of their potential to influence community-level interactions in ecosystems recovering from anthropogenic disturbance.

Ben and I are planning to do some individual-based modelling to learn further about the effects of stochastic hatching from historical resting egg banks on contemporary evolution to environmental change.

How does evolution work?

I'd like to kick this blog off with a very broad question: how does evolution work?  The photo above was taken at Antelope Canyon, in Arizona.  The sandstone walls of the canyon have been carved by erosion over many millenia: uncountable grains of sand, myriad molecules of water, all rubbing against the rock on their journey downstream, gradually shaping the canyon into what it is today.  And what the canyon looks like depends very much on when you visit it; the floor of the canyon, which is just sand left behind by the last flash flood, rises and falls by many feet over short periods of time, or so I am told.  Formations that are hidden by sand one month may be many feet above your head the next month.  Regardless of when you visit it, however, the canyon is stunningly beautiful.

Antelope Canyon is an example of the marriage of the deterministic and the contingent.  On the one hand, the shapes carved in the canyon walls are not predetermined by any mathematical formula.  No computer could predict the particular form that the canyon has today.  A soft spot here and a hard spot there, an eddy here and a fast-flowing current there, have made it the way it is now; but slightly different conditions might have led to completely different contours.  In any case the canyon is not a static entity; if you could visit it a few thousand years from now, it might look quite different.  On the other hand, its shape is not completely random; there are many shapes that will never be formed by its particular dynamics.  Wait as long as you like, but you will never find a tiny replica of the Empire State building cut into the rock.  Sandstone and erosion have their own particular laws, which they always obey.

The question I am interested in, and the one that attracted me to work in the Hendry lab, is: how are the products of evolution — fish and frogs, birds and beavers, you and I — like or unlike Antelope Canyon?  To what extent are the products of evolution predictable and deterministic, a repeatable outcome given environmental conditions?  To what extent are they unique, the irreproducible results of a grand experiment that can never be replicated?  What are the laws that evolution obeys?  What sorts of products will it tend to create over and over, and what sorts of products, like the Empire State Building, are forever beyond its reach?  How quickly can its products change — how long does it take for a new species to form, or for a new trait to evolve?  And — a question that particularly interests me, but that seems completely unapproachable — why are the products of systems at the interface between determinism and contingency, like living organisms or Antelope Canyon, so incredibly beautiful?

Really answering such questions is far beyond the reach of a PhD thesis, or even an entire career; but they are the kinds of questions that inspire me.  All this could be framed in much more academic, jargon-laden ways: gene flow and selection gradients and additive genetic variance.  But it's important, I think, to keep in mind the ultimate reasons we have embarked on this journey: our curiosity about nature, and our joy upon beholding its beauty.  Let's keep the destination in mind, but enjoy the journey, too.