Counting Species As we mentioned, quantifying species richness is challenging. T
ID: 213979 • Letter: C
Question
Counting Species As we mentioned, quantifying species richness is challenging. This is true whether discussing global species simply counting the number of species living in a particular location, which is known site. For example, suppose you want to know how many species of sessile wall just offshore of a Caribbean island. Subt sea cucumbers, and sea squirts. How should you go about counting them? richness or opitlauna invertebrates are living on a rock idal invertebrate communities are diverse and include a variety of corals In an ideal world, you would identify the species of each individual on the wall. Iln the real world, this is expensive if not downright impossible. The alternative is to estimate alpha diversity through sampling. While there are both destructive and nondestructive sampling techniques you might use, nondestructive approaches are preferable when results are comparable. One nondestructive technique is to photograph a known area-say a 0.25 m2 plot-and identify all the species in the photograph (known as a photo quadrat). Q1.1. Make a prediction: how many photo quadrats should you take in order to estimate the alpha diversity (number of species) on an underwater rock wall? Take photo quadrats that sample the whole area of the rock 0 Take photo quadrats until the first photo showing no new species. (A new" species here is one that was not in a Divers surveying the invertebrate community attached to a subtidal rock wall approximabely 10 m below the surface previous quadrat.) Take photo quadrats until several photos in a row show very few new species. Image courtesy Ron Ener Take only a few photo quadrats. Then multiply the number of species rock. found in that smalil area by the full area of teExplanation / Answer
To avoid Bias it is necessary that we do sampling at random, that means taking a few photos and then multiplying the number of species found in that small area by the full area of the rock. Any other means would yield futile results. If you sample the entire are no efficiency would be there. Search for a new species in quadrats would bias the sampling.
Although there are several other guidelines in place which decide the size and shape of the quadrats such as if 5 percent of samples have none of the species of interest we must increase the quadrat size. It also depends on the distribution of species- homogenous or otherwise.