PhD Arthur Decae 2010 - Ghent Ecology - Universiteit Gent

Abstract
Seven species of the trapdoor spider genus Nemesia (family Nemesiidae) have recently been
found in the Balearics, five on Majorca and two on Ibiza. Only one of these species N. brauni
(L. Koch 1882) had previously been named and described. Another species, N. bristowei sp.
n., had been reported from Majorca by Bristowe (1941, 1952), but it was never formally
described. The remaining five species are new. Here, supplementary notes and new figures
are given for N. brauni, and six new species are described and figured for the first time.
Additional information on the natural history, behavior and distribution of all seven species is
provided. The six new species are: N. bristowei, N. seldeni sp. n., N. randa sp. n. and N.
santeugenia sp. n., all from Majorca; N. ibiza sp. n. and N. santeulalia sp. n., from Ibiza. All
species are regarded as endemic to the Balearics.
The information on the individual species is preceded by a review of the morphology of
Nemesia at the generic level in order to discuss diagnostic characters for distinguishing
species.
Introduction
Among the Mygalomorphae, the genus
Nemesia is comparatively rich in species. A
survey of Platnick's (2003) catalogue shows
that Nemesia currently ranks fifth in a list of
303 mygalomorph genera (Table1). Large
genera usually have large areas of
distribution. The largest mygalomorph
genus, Idiops, occurs in Africa, Asia and
South America, and the second largest
genus, Aphonopelma, although concentrated
in North America, also has South American
representatives. According to Platnick's list,
Nemesia also has an almost cosmopolitan
distribution. The reality of this wide
occurrence, however, is biogeographically
difficult to explain, because of a curious
discontinuous distribution, with single
species recorded from China, Afghanistan, Mozambique and Cuba and approximately fifty
species reported from one relatively small geographical zone. In fact the distribution of
Nemesia is concentrated around the western, central, and parts of the eastern Mediterranean. It
is bordered by Alpine mountain ranges in the north, the Sahara desert in the south and the
Atlantic Ocean in the west (see Chapter 2, Fig. 5). In North Africa the genus is reported from
as Far East as Egypt, and in southern Europe as far east as Cyprus 13 . Nemesia is not known
from Anatolia, where it seems to be replaced by the related genus Brachythele Ausserer 1871.
The high species diversity of Nemesia in the restricted geographical zone around the western
and central Mediterranean might tentatively be explained by the combined effects of poor
powers of dispersal and strong allopatric speciation in an area that has been fragmented for
millions of years by tectonic activity and/or that has seen numerous relict populations formed
in an area that, in the not too distant past, has been affected by Pleistocene glaciations. The
reality of such speculation, however, remains to be investigated, but it could possibly explain
why so many, if not all, Nemesia species seem to be local endemics.
13 Not shown in Fig. 1.