Conditions for Overcollecting

[Niklas Wahlberg]

Hi,
   Here is some practical experience on "collecting" endangered species.
I studied Melitaea diamina (a checkerspot butterfly highly endangered in
Finland) a few years ago. One task was to estimate population sizes and
movements in a small metapopulation consisting of 14 local populations
in an area of about 2 km by 2 km. I used mark-recapture methods, ie my
aim was to capture every single individual at least once... I sampled
every day all day (actually there were two of us) for the whole flight
period (about one month). I captured 842 individuals (of which 285 were
females, the more important sex for reproduction :-) ). From the data I
collected I estimated that a total of about 2000 individuals inhabited
the network. So I was able to "collect" 40-50% of the population in 30
days of intensive sampling. So, my conclusion is that generally
collecting will not harm a species with a healthy metapopulation (a
collection of local populations that are in contact with each other
through dispersing individuals). Some local populations may be extremely
small, but these tend to go extinct anyway (our research group has
recorded hundreds of extinctions in a large metapopulation of Melitaea
cinxia in Finland). The bottom line is that preserve enough habitat so
that there are many (>20) local populations within a given area (size
depending on the species requirements)and the insect species should do
OK.
   By the way, my study on M. diamina had all the required permits and I
did not kill any individuals.

Cheers,
Niklas

________________________________________________________________________

   Niklas Wahlberg                          
   Department of Ecology and Systematics    
   Division of Population Biology           
   PO Box 17 (Arkadiankatu 7)               
   00014 University of Helsinki
   Finland                                                         
   p. +358-9-191 7378, fax +358-9-191 7301  
 Check out our web-site:                    
  http://www.helsinki.fi/science/metapop/