Agriculture Reference
In-Depth Information
The dendrograms demonstrated the existence of two groupings of species. The first group, with
O. frivaldszkyi
, has conspicuous dorsal pores and a somewhat
shorter (nine-segment) tubercula pubertatis and clitellum. The second group of species has incon-
spicuous dorsal pores and longer clitellar organs (10 to 11 segments).
,
O. compromissus
, and
O. exacystis
, with no
dorsal pores, has a separate position. Even though it is only a phenotypical tree, not a phylogenetical
one, the dendrograms suggest a truly divergent position of the four larger
Octodrilus aporus
Octodrilus
species,
namely,
O. frivaldszkyi, O. aporus, Octodrilus ophiomorphus
, and
Octodrilus permagnus,
and the
high probability that their discrimination is objective.
In describing new species or in delimiting the range of characters for already described species,
we adopted a rigorous statistical procedure. Thus, tables with statistically processed data are part
of the description. The type series, in the majority of taxa discussed here, had tens or even hundreds
of individuals. The type populations and the holotypes, as well as the neotype for
O. frivaldszkyi
,
were selected to match as nearly as possible the arithmetic mean value of the numeric characters
of the whole type series. Thus, the Ñnomenclatural typeÒ or the Ñname bearerÒ of newly described
or amended taxa corresponds to the ÑmorphologicalÒ or the ÑbiologicalÒ types. It is important to
notice that such a selection avoids hazardous designation of holotypes from marginal, overlapping
populations of taxa.
M
OLECULAR
T
AXONOMY
AND
P
HYLOGENY
OF
THE
O
CTODRILUS
S
PECIES
It is well known that some taxonomists do not accept, or look on without some reservation, species
described by numerical taxonomy. Therefore, we had some degree of uncertainty concerning the
validity of taxa we described as new in 1976 and 1989. Namely, are the four giant
Octodrilus
species from the Carpathians really distinct species, or assuming a higher variability of genital
characters, should they have been incorporated into the old
O. frivaldszkyi
? Or, was it correct to
distinguish
Octodrilus bihariensis
from
O. exacystis
or from
O. compromissus
based mainly on a
difference of only one segment in the position of the clitellar organs? A. Pop studied this species
by molecular taxonomy, which is expected to provide new and more precise ways of delimiting
genera as well as establishing phylogenetic distances among species.
New, fresh individuals of these few species were collected from the already known sites in
the type localities. The molecular research was done in the laboratories of the Institute of
Pharmacy and Molecular Biotechnology, Ruprecht Karls University in Heidelberg, Germany.
Structure of two components of DNA, namely, the 16S ribosomal DNA (rDNA) sequences and
cytochrome
c
oxidase (COI) genes, were established by standard or slightly modified methods
(A.A. Pop et al. 2003).
Six of the seven
Octodrilus
species occurring in the Apuseni Mountains were studied (
Table
the nominate subspecies were analyzed. Partial sequences for 16S rDNA of seven taxa (six species
and one subspecies) and subunit I for COI for the same seven taxa were obtained. The relative
nucleotide structure of analyzed genes is presented in Table 7.2, and the maximum parsimony trees
are shown in
Figure 7.5
and
Figure 7.6
.
Both cladograms are rooted with a snail species,
Biomphalaria tenagophila
(Mollusca, Gastropoda, Planorbidae).
R
ESULTS
16S rDNA Sequences
The parsimony analysis of molecular data (491 bp) resulted in a single optimal tree with length
314, consistency index 0.9427, homoplasy index 0.0573, and retention index 0.6087. Of the 491
nucleotide positions, 230 (46.84%) were constant, 229 (46.64%) were variable and parsimony
uninformative, and 32 (6.52%) were parsimony informative.
