Mello-Leitão’s
(1918)
description of Litoporus iguassuensis
was based on a single female specimen and a juvenile male from Rio de
Janeiro,
Brazil. No figure accompanied the original description, and the species
did not
reappear in the literature until 2000 when I provided a brief
redescription
and figures of the female genitalia based on the female type specimen (Huber 2000). When males were finally
discovered and collected during the last years, this tiny and at first
sight inconspicuous species turned out to be surprisingly exceptional
among
pholcids in various ways. First, females and juveniles were found to
live in
camouflaged retreats (below, right photo), a behavior that has not been
documented in any other
pholcid spider. Second, males were found to live outside the retreats
in the
domed sheets (below, left photo), and this behavioral difference
probably explains the strong sexual
size and color dimorphism that is also rare in pholcids. Third, females
were
found to be color polymorphic, a phenomenon that is equally uncommon in
pholcids.
In addition to being thus
exceptional, Mello-Leitão’s species continues to defy easy
classification, both
at the levels of genus and species. Our current conclusion is that
Mello-Leitão’s original assignment to the genus Litoporus
is not only the best
hypothesis but it also
generates a number of exciting testable predictions. The first prediction
relates to the fact that females remain unknown in all three closest
relatives
of the type species L. aerius (i.e.
in L. dimona, L. saul, L.
secoya; all
described in Huber, 2000). We predict that, just as in L.
iguassuensis, their females are so different from the males that
they were separated from them when the material was initially sorted to
species. The second prediction
concerns the phylogenetic relationship between Litoporus
and Mesabolivar.
If the placement of L. iguassuensis in Litoporus
is correct, then this means
that Litoporus is nested within a
paraphyletic Mesabolivar, eventually
requiring splitting or synonymization of Mesabolivar. At the species level,
we initially assumed to be dealing with up to five species.
Morphological
differences weakly pointed in that direction (see figure below).
However, molecular markers failed
to provide congruent grouping information, so we decided that with the
current
evidence it is more parsimonious to argue for a single variable species
than
for two or more species.
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