I’m a bit behind in posts about the Discovering Insect Species course, because so much has happened so quickly. Last week we examined our catch from the local field trip and learned how to prepare specimens, and we learned the state of the art in Trepanedoris systematics. On the weekend we went on our second field trip (this time for two full days), and then this week we are extracting DNA and amplifying DNA from two genes. Although I am tempted to jump in with the excitement of the field trip, I think it best to start with last week.
We warmed up to Trepanedoris by leaning how to mount them on points. This began by sorting beetles the students collected in Corvallis last week, and gluing them to little triangles of paper attached to insect pins.
This exercise not only taught them the basic preparation and labeling methods, but also allowed them to interact with specimens and look at them more closely. And it gave them a sense of satisfaction of a job well done.
On Thursday we mounted specimens from a locality in California (Arroyo Seco), from which John and I had collected many specimens last summer. There appeared to be two common Trepanedoris species at this site; a shiny one that tended to be on the open mud near the shore, and a duller one that tended to be up in the reeds.
Identifying and sorting Trepanedoris
The students then took some of the specimens they had mounted, and used the keys from Lindroth’s 1963 work to see if they could identify them. For a group who had never seen a Bembidion before a few weeks ago, who had rarely if ever used a key to identify insects, and who had miserable lighting on their microscopes, they did very well. Several of the students identified the shiny species at Arroyo Seco as Bembidion ampliceps, and others as B. connivens. This fits my tentative naming of the two forms.
After giving the class an overview of previously published research on Trepanedoris, I then introduced them to the 43 specimens that my lab has previously sequenced for several genes. I showed them the vouchers, pointed and labeled, and gave them cards showing various pictures of the specimens (habitus, head, pronotum, male genitalia). As in our first class, they then tried to sort them into species based upon the pictures.
I then presented them with the gene trees from the four genes, and talked about my current views about Trepanedoris species, based upon the gene trees, combined with morphological and geographic data. I’ll give an overview of my current views in the next post.
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