[NHCOLL-L:1118] Re: Rare or Threatened?

[Dr Brendan Moyle]

At 08:03 AM 7/24/01 +1000, Vr. Richard Bejsak-Colloredo-Mansfeld wrote:

>I would like to know how to categorize abundance of the insect.
>What is beetle like Rosalia alpina? Rare or Endangered?
>Is there any link between category like:
>Very common - Common - Very abundant - Abundant - Rare - Very rare -
>Sporadic
>and category like:
>Common - Vulnerable  - Threatened - Endangered - Critically Endangered???

I'd be astonished.  In my experience, applying categories basically
developed for vertebrates doesn't work all that well for invertebrates.
Assessing invertebrate abundance is a challenge because generally, there is
a lack of time-series data on trends, abundance shows large temporal
variance, many taxa simply remain undescribed (e.g. the checklist for an
island that simply recorded 'pseudoscorpion'- at least they got the 'order'
right) and what we know is dominated by search-effort.  Last year I was
given 4 new specimens of a Tyrannochthoniid that hadn't been seen since the
early 60s (even then only two records existed).    I'd hesitate to claim
that this indicates the species is threatened in any way.  

>Is there any paper, publication dealing with this issues?

Dury (Drury?) published something quite a few years ago on how rarity was
not a good proxy for endangered status.

Also Ferson S. and Burgman, M. (eds) text Quantitative Methods for
Conservation Biology has a chapter on using scientific collections to infer
threats.  (I've suggested that morphological data can be used to identify
correlates of extinction risk in chapter 3 of the book).  

Kind regards

Brendan
Dr Brendan Moyle
Bioeconomist
Massey University (Albany), NEW ZEALAND
http://www.massey.ac.nz/~bjmoyle/

"What has always made the state a hell on earth has been precisely that man
has tried to make it his heaven."- F. Hoelderlin