Agriculture Reference
In-Depth Information
If we admit that insular speciation may exist in these mountains, we must admit a similar
process of subspecies differentiation. Widespread species, inhabiting multiple kinds of biotopes,
show clear morphological differences in the framework of species diagnostic characters. Taxonomic
differences among subspecies concern mostly characters related to the size of the earthworms (i.e.,
the length, number of segments, and ending of the typhlosole). The location of the typhlosole
ending, which is a very constant character in local
species populations, is positively
related with the size and number of segments and has proved to be a convenient character for
subspecies discrimination according to the Ñ75% ruleÒ (Mayr et al. 1953).
The shape and length of the typhlosole may have an ecological significance as an adaptation
to the quality and quantity of food. The size of the earthworms, which is positively related with
the typhlosole ending, could also be regarded as an adaptation to soil conditions. In these mountains,
the smaller species generally dwell in more compact soils under grassland; the larger ones tend to
inhabit looser forest soils. Thus, statistically delimited groupings of local octodrilus populations
might be regarded as also having different ecological requirements and could therefore be consid-
ered as distinct subspecies.
Based on the above ordination of the diagnostic value of characters, we described, from a
relatively small area in the Apuseni Mountains, five new
Octodrilus
Octodrilus
species and seven new sub-
This number of newly described taxa suggested that the Apuseni Mountains should be considered
as an active speciation center of the genus
.
The validity of the species and subspecies delimitations was checked using a multiple character
analysis without previous subordination of the diagnostic value of the characters. Following Sims
Octodrilus
(1969), we used the simple ShealsÔ method (1964). The dendrograms, drawn according to Mount-
ford (1962), used in classifying taxa (Figure 7.4) resemble very much the key drawn for delimiting
taxa by the main diagnostic characters (
Figure 7.3
)
.
90-111
116-136
-37
29-
72-120
-39
125-158
88-118
125-152
-38
140-162
30-
-39
-40
Tubercula pubertatis
FIGURE 7.4
Classification of
Octodrilus
taxa from the Apuseni Mountains by multiple character analyses.
