EPOW - Ecology Picture of the Week

Explanation:  What's for dinner?  Well, it's not these tidy rows of beetles, taken from pitfall traps in an old-growth conifer forest in the high Cascade Mountains of southern Washington.  

You're looking at the first stage in identification of a large number of captures of invertebrates -- insects, spiders, and allies -- in a study of remnant patches of old-growth forest.  Terrestrial invertebrates are initially captured in the field by many means, including using pitfall traps, Malaise traps, beating low branches onto a canvas sheet, sweeping shrubs with a capture net, and excising soil samples to run through Berlese funnels.  Canopy invertebrates are obtained by other means, including branch-clipping and fogging.

Once the samples are obtained comes the next stage in the study back at the lab.  This entails sorting them into ever-finer groups until the individual organisms can be identified to species or, if that is not possible, to lowest taxonomic level (LTL). 

The first step in the sorting process is to group organisms into sets of morphospecies -- which are groups of organisms that belong to at least the same taxonomic class and order, and that look very similar, and that came from the same kind of sample (underground soil, forest floor, etc.).  View a photo series here on the methods.  (Also see a sampling scheme for aquatic benthic invertebrates here.)

The organisms are sorted in ethylene glycol (antifreeze) in a large lasagna pan (yum), and then put into labeled well-plates and petri dishes.  The result is sets of invertebrates catalogued by morphospecies categories such as micro-spiders, carabid beetles, small black ants, caterpillars, small snails, centipedes, and many other groups.  

The next steps entail further separating each morphospecies group several more times until individual species (or LTLs) can be identified by entomologists.  However, the effort and expertise needed to identify organisms to this fine level can be enormous and in limited supply.  

So the question becomes, can we make reasonable judgments on ecological conditions -- presence and abundance of functional groups, relative biomass of trophic levels, and diversity of taxa and body sizes -- based only morphospecies?  My ongoing study will test this question.  Other studies (Derraik et al. 2002, Oliver and Beattie 1996, Barratt et al. 2003) found that spiders, beetles, and butterflies separated into morphospecies fairly accurately compared to taxonomic identification of the same samples, although with diverse groups such as beetles some caution is in order. 

There is no one set way to group insects or invertebrates into morphospecies.  For example, ants can be grouped according to body color, type, and presence of stripes. 

Information:
     Barratt, B. I. P., J. G. B. Derraik, C. G. Rufaut, A. J. Goodman, and K. J. M. Dickinson. 2003. Morphospecies as a substitute for Coleoptera species identification, and the value of experience in improving accuracy. Journal of the Royal Society of New Zealand 33(2):583-590.
     Derraik, J. G. B., G. P. Closs, K. J. M. Dickinson, P. Sirvid, B. I. P. Barratt, and B. H. Patrick. 2002. Arthropod morphospecies versus taxonomic species: a case study with Araneae, Coleoptera, and Lepidoptera. Conservation Biology 16(4):1015-1023. 
     Oliver, I., and A. J. Beattie. 1996. Invertebrate morphospecies as surrogates for species: a case study. Cons. Biol. 10(1):99-109.