On one hand there are spontaneous hybrids between Centaurea jacea
and Centaurea nigra subsp. nemoralis, as that from the region of Gladenbach
which I unfortunately had to photographe during rain, so details as e.g. the calyx scales
can hardly be seen.
On the other hand at points of contact between Centaurea jacea
and Centaurea nigra subsp. nemoralis, e.g. glades in the Mühltal valley
near Heidelberg which leads from the Rhine valley to the Odenwald,
there are transition populations. These are showing the stature and appearance
of Centaurea jacea, but in details, e.g. the calix scales, all transitions
between Centaurea jacea and Centaurea nigra subsp. nemoralis can be seen.
The edges of the calyx scales of Centaurea jacea are only short pinnate,
while those of Centaurea nigra subsp. nemoralis are very long pinnate.
The transition populations are capable of reproduction, and most probably came
into being by back-crossing of hybrids with Centaurea jacea.
|
