When we speak of rare species, we should bear in mind the enormous dynamics of
the evolution processes. For natural reasons (e.g. change of environmental
conditions, competition by more vigorous or better adapted species in the same
ecological niche, and so on) there exist many declining species all over the world.
Such species become really extremely rare prior to their extinction. In many cases
such species are stenoendemics and relicts which are restricted to a certain small
habitat. For example, the Obwalden Hairsnail Trichia biconica (Eder 1917) at present
lives only on a few hectares of an alpine pasture in the center of Switzerland and
nowhere else in the world. Collectors, get off your hands from such species, but try
to give them a chance to survive for a few centuries!
    With kind regards to all true lovers of mollusks,
    Hans Turner
 
 
 
Ross Mayhew wrote:
 
>         The  speculation has been made several times on  the L that there may
> in fact be no rare species, but only spp whose "prime habitat" has
> simply not been sampled.  To a certain extent, this may be true, but in
> nature there is  actually much data to suport the notion that some,
> perhaps many species are indeed truly rare, either in the sense that
> they exist in very low population densities, even in what appears to be
> their breeding habitat, or in the sense that their preferred habitat
> itself, is extremely scarce.  This may be especially true for Turridae -
> there are several spp of Turrids in my region which are known from a
> very few specimens, even though there have been tens of thousands of
> samples taken around where the specimens have been found, using a
> variety of sampling methods.  It could be argued that these spp might
> just be very fast, but this is not convincing.
>         Many spp in all phyla have been known to exist and perpetuate
> themselves at very low densities - consider for example species or
> subspecies nearly extinct for one reason or the other: Siberian Tigers,
> many species of whales, some brachiopods, ...some driven to the edge of
> extinction by man, others just at the end of their time on the planet.
> Other species perhaps have extremely efficient methods of finding mates
> at the proper time (such as powerful phemerones, or visual clues visible
> for  signifigant distances), so they do not have to have high densities
> in order to survive.
>         So, i think it safe to say that yes, there are indeed rare species in
> fact, as well as in collections.
> -Ross M.
> --
> Ross Mayhew:    Schooner Specimen Shells:    Http://www.schnr-specimen-shells.com
> "We Specialize in the Unusual"
> Phone: (902) 876-2241     Snail Mail; P.O Box 20005, RPO Spryfield,
> Halifax, N.S., Canada, B3R 2K9.
> But try to find "something for Everyone"!!