0.4 What is biodiversity? a comparison of spider communities  (Page 2/3)

Assign each species a working name, preferably something descriptive. For example, you might call a particularspecies "spotted abdomen, very hairy" or "short legs, spiky abdomen" Just remember that the more useful names will bethose that signify to you something unique about the species. Construct a table listing each species, itsdistinguishing characteristics, the name you have applied to it, and the number of occurrences of the species in thecollection ( ).

Last, ask whether this collection adequately represents the true diversity of spiders in the forest patch at the time ofcollection. Were most of the species present sampled or were many likely missed? This is always an important question toask to ensure that the sample was adequate and hence can be legitimately contrasted among sites to, for example, assignareas as low versus high diversity sites.

To do this you will perform a simple but informative analysis that is standard practice for conservationbiologists who do biodiversity surveys. This analysis involves constructing a so-called collector's curve ( Colwell and Coddington 1994 ). These plot the cumulative number of species observed (y-axis) against the cumulative number ofindividuals classified (x-axis). The collector's curve is an increasing function with a slope that will decrease as moreindividuals are classified and as fewer species remain to be identified ( ). If sampling stops while the collector's curve is still rapidly increasing,sampling is incomplete and many species likely remain undetected. Alternatively, if the slope of the collector'scurve reaches zero (flattens out), sampling is likely morethan adequate as few to no new species remain undetected.

To construct the collector's curve for this spider collection, choose a specimen within the collection atrandom. This will be your first data point, such that $X=1$ and $Y=1$ because after examining the first individual you have also identified one new species! Next move consistentlyin any direction to a new specimen and record whether it is a member of a new species. In this next step, $X=2$ , but $Y$ may remain as 1 if the next individual is not of a new species or it maychange to 2 if the individual represents a new species different from individual 1. Repeat this process until youhave proceeded through all 50 specimens and construct the collector's curve from the data obtained (just plot $Y$ versus $X$ ). Does the curve flatten out? If so, after how many individual spiders have beencollected? If not, is the curve still increasing? What can you conclude from the shape of your collector's curve as towhether the sample of spiders is an adequate characterization of spider diversity at the site?

Level 2: contrasting spider diversity among sites to provide a basis for prioritizing conservation efforts

In this part of the exercise you are provided with spider collections from 4 other forest patches. The forest patcheshave resulted from fragmentation of a once much larger, continuous forest. You will use the spider diversityinformation to prioritize efforts for the five different forest patches (including the data from the first patchwhich you have already classified). Here are the additional spider collections: (See , , , and )