Re: BRYONET: Local endemic bryophytes

BRYONET

Dear Jairo and other Bryonetters,

The question of local endemism in the strict sense among bryophytes -
except for some obvious cases - will remain critical for long time. Some
species considered to be such, became known from several more places
quite far from the type localities, like Renauldia lycopodioides
(Tanzania, Kenya), Diphscium pocsii(Tanzania, Honduras)or Xylolejeunea
grolleana (Madagascar, Mascarenes), while others, like Pocsiella
hydrogonioides (Mt. Kilimanjaro), Cladolejeunea aberrans (Usambara Mts.)
or Drepanolejeunea helenae (Reunion Island) remained restricted to a
small area. I would like to call your attention to the experiments made
by B.O. van Zanten (J. Hattori Bot. Lab. 44: 455-482), who found that
those species, which have spores very resistant to environmental
conditions, even if they were known only from their type locality,
sooner or later become known from a larger area, while those, which are
not resistant against desiccation, extreme temperature changes and UV
irradiation, are restricted usually to a small area. Of course, plate
tectonics, geographical and ecological isolation, life strategies and
other factors also play a role in the narrow or wide distribution. No
doubt, many tropical specimes were described from one poor specimen and
when their variability became known, fell in synonymy and also, our
knowledge on the distribution of tropical taxa still very incomplete. I
agree with Rod Seppelt, who wrote that only molecular investigation will
say the final word in these cases, but anyway, a collection of data on
narrow endemics definitely will be useful.

Tamas Pocs, colura@chello.hu
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