Wobbegong snacking

Remarkable photo by Daniela Ceccarelli with the ARC Centre of Excellence for Coral Reef Studies, who caught this image of a tasselled wobbegong lunching on another shark.  Here's the story at New Scientist.

Evolving salamanders

Another nice study of evolution in action.  Steven Brady, a doctoral student in Yale's School of Forestry and Environmental Studies, examined spotted salamanders living in roadside ponds contaminated by various types of runoff.  He found that they had significantly higher mortality than their brethren living in more isolated woodland pools.  But, after being toughened in their caustic roadside environments, the road warriors seemed to be superior competitors.  Reciprocal transplant experiments showed that the roadside salamanders hatched significantly better than did woodland populations in roadside conditions, and did almost as well as the woodland groups did on their home turf. 

We probably need to see more studies like this, as we move toward a world in which we won't differentiate habitats as disturbed and pristine, but rather by levels of perturbation.

Founder effects and selection

Many people that have some minimal understanding of evolution think that all differences we find among populations must be attributed to the effect of natural selection.  That's not true at all.  While selection is certainly the driving force behind much of evolutionary change, it's not the only process at work.  A major factor, particularly in small populations, is a random process that we call genetic drift.  A special case of genetic drift known as the founder effect can take place when a new habitat, like an island, is colonized by a small subset of organisms from a larger population.  Many times, that small random sample of founders differs, sometimes dramatically, from the source population from which it was drawn.  This difference may have nothing whatsoever to do with selection.

In a fascinating new paper appearing in Science and discussed here at Science Daily, Jason Kolbe and his colleagues investigate the interaction of founder effects and natural selection on populations of brown anoles that they established on small islands in the Bahamas.  After the native populations of anoles were wiped out by a storm, the researchers replaced them with pairs of anoles collected from nearby Great Abaco.  The introduced anoles, adapted to the forests of their home island,  had longer legs than those typically found on lizards inhabiting the scrub habitats of the small islands.  However, as the result of random nature of the simulated founding event, the seed populations of the islands differed in limb length. 

After four years of monitoring, the biologists found that the (now well-established) anole populations on the small islands had indeed evolved toward shorter leg length.  However, the initial differences in populations were still in evidence, as the ranks of limb lengths of the founding populations had been retained.  In other words, the limb length of the island anole populations were a result of both the founder effect, and the subsequent effects of selection.

A challenge...

...for my students.  Some of you think you're pretty clever.  Actually,  some of you are.  But, take a look at this young lady's study session for her anthropology exam.  Since she posted it on YouTube, I assume she won't mind me linking it here.



OK, go forth and be creative.