Sunday, September 20, 2015

New semester; snorkeling; insect identification; and statistics!

A new semester; new students; and an 85 F temperature forecast for lab.  It seemed like a perfect opportunity to really experience Lake Champlain.  I bought out all of the remaining masks and snorkels from a certain local store and we were ready to go.

My customary first lab in Community Ecology has been to test the species area relationship.  It seems like a simple enough concept: bigger area - more species, but the concept underlies important conservation biology topics such as reserve design.  The lab also provides an ideal entry point to community ecology.  Bigger areas do tend to have more species, but also a mathematical inconvenience: there are also more individual organisms.  Imagine any community with some finite number of species.  We sample 1 individual and we automatically have sampled 1 species.  As we sample more individuals we also sample more species.  Therein lies the mathematical problem: do larger areas have more species for some biological reason.....or is it just because we sampled more individuals?

On cool September days we typically wade into Lake Champlain in chest waders.  But the warm weather this year was perfect for snorkeling.  So in we went!  Snorkeling or wading, the procedure is simple enough: Find submerged rocks of diverse sizes, net them, measure them, and identify all of the attached invertebrates.

The lab has all of the ingredients necessary for an excellent learning experience: field work; sampling real communities; insect identification; data generation; analysis; writing; and the opportunity to get wet in Lake Champlain on the second day of a new semester was icing on the cake.  This year yielded a bumper crop of very tiny zebra mussels along with 24 other invertebrate species.  

By now there are 22 students writing lab reports based on the data set.  They have learned how to deal with the mathematical sampling issue using rarefaction, how and why to log transform their data set, and how to use linear regression to measure the strength of the relationship between rock area and the number of species sampled.

I'm looking forward to reading the lab reports and moving on to another successful semester in Community Ecology!

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