Posted by David Gibbs on 03-08-2008 11:33
#23
Rui Andrade wrote:
The work's goal is to create a numerical classification of the diversity one can find on a given place (I was contacted to collect and to try to identify insects).
Perhaps something has been lost in translation but i do not understand this.
numerical classification of the diversity
sounds like a tautology to me, diversity is a numerical cassification.
It is, of course, utterly impossible to measure the absolute biodiversity of any site, thus any classification must be based on a sampled subset and only meanigful in comparison with other sites sampled in the same way. so the techniques used and the groups sampled are less important than is consisency of sampling between sites.
you say
The work's goal is to create a numerical classification of the diversity one can find on a given place
, but to what end?What are you going to want to do with this number once you have it? As mentioned in previous posts, diversity is not necesarily a measure of quality and without some baseline with which to compare will mean little.
when you say ?do a minimum of three field trip days? do you mean 3 days in each month, or 3 days during that 3 month period (1 day in each month)?
I mean minimum of three days in total, however the more the better. I say three days because in GB this equates to a species list of 250+ which is an adequate data set, I would always like more but few clients will pay for more.
Another thing, how do you use sweep netting in a study of this kind? Do you do a fixed number of sweeps in a given route, or do you actively capture the specimen of interest?
If you are doing a qualatative survey then your best approach is to use techniques which will produce the largeat species list in the most repeatable way.
Another thought, if mere diversity (rather than quality) is the index you want, then rather than target predators, parasitoides and specialists (most of which are low-density species), then saprophages, phytophages and the easily identified will give you max diversity for effort.