[Taxacom] How frequent should you collect for a good representation of insect fauna?

[Derek Sikes]

Here's one paper that deals with this issue of different trapping  
methods and I know there's lots out there on pitfall trap methodology:

Longino, J. T., and R. K. Colwell. 1998. Biodiversity assessment  
using structured inventory:
capturing the ant fauna of a lowland tropical rainforest. Ecological  
Applications 7:
1263–1277.

-Derek

On Oct 22, 2007, at 8:45 AM, Doug Yanega wrote:

> Soowon Cho wrote:
>
>> I have collected insects
>> in my university for a year: with four different collecting  
>> methods at four
>> sites in every other week, and the data tells me that on average  
>> only about
>> 30% of the insect species collected at a collecting are collected  
>> again at
>> the next collecting.
>
> You say the results surprised you, but I would only be surprised at
> this if malaise or berlese trap samples gave that result; for nearly
> every other collecting method I'm familiar with, the proportion of
> taxa sampled relative to the number present is generally so low that
> you will commonly fail to collect many taxa that *could* have been
> caught - because so much of what is present occurs in such low
> numbers that they're unlikely to be sampled except by a very robust
> sampling protocol. When a large proportion of the fauna is "rare",
> the result is a lot of "false negatives" in each collecting event,
> inflating the apparent differences between successive samples not
> because of genuine differences in species composition, but because
> the odds of sampling the same *rare* taxa in successive intervals is
> extremely low.
>
> Comparisons between different collecting techniques will further
> inflate the differences (I work with pan traps frequently, and it's
> been found that you can place yellow, blue, and white traps right
> next to one another and still have about 30% of the taxa trapped by
> each color not replicated by the other colors). While a technique
> like malaise trapping can give a fair overlap from sample to sample,
> other collecting techniques performed alongside malaise trapping can
> still give very different results (pan traps, for example, collect
> MANY more bee species than malaise traps), so combining results will
> give very different patterns from just using malaise traps alone.
>
> The funny thing is that I don't really know how often folks publish
> discussions specifically referring to the nature of sampling
> protocols and analysis; most of what I'm familiar with is from
> first-hand experience and discussions with other collectors, and I'd
> have a hard time giving actual citations. That does remind me, though
> - this is something to bring up at this year's meeting of the
> Entomological Collections Network, to see about putting together a
> website listing references discussing sampling techniques, if no one
> else already has a similar website in place somewhere.
>
> Peace,
> -- 
>
> Doug Yanega        Dept. of Entomology         Entomology Research  
> Museum
> Univ. of California, Riverside, CA 92521-0314        skype: dyanega
> phone: (951) 827-4315 (standard disclaimer: opinions are mine, not  
> UCR's)
>               http://cache.ucr.edu/~heraty/yanega.html
>    "There are some enterprises in which a careful disorderliness
>          is the true method" - Herman Melville, Moby Dick, Chap. 82
>
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++++++++++++++++++++++++++++++++++++++++++++++
Derek S. Sikes, Curator of Insects
Assistant Professor of Entomology
University of Alaska Museum
907 Yukon Drive
Fairbanks, AK   99775-6960

dsikes at alaska.edu
http://homepages.ucalgary.ca/~dsikes/sikes_lab.htm

phone: 907-474-6278
FAX: 907-474-5469


"Remember that Truth alone is the matter you are in Search after; and  
if you have been mistaken, let no Vanity reduce you to persist in  
your mistake." Henry Baker, London, 1785

University of Alaska Museum of the North -
http://www.uaf.edu/museum/
++++++++++++++++++++++++++++++++++++++++++++++