Ignatov, M.S., U.N. Spirina, E.A. Ignatova, M. Krug & D. Quandt. On
the systematic position of the moss genus Catoscopium,
with a new approach to the peristome reduction study
Arctoa (2015) 24: 389-415
doi: 10.15298/arctoa.24.32
The
early stages of the peristome development in the monospecific moss genus Catoscopium
were studied. The peristomial formula 4:2:3 is the most common, although there
are deviations, increasing in number at later stages of development. Additional
cell divisions were observed in all peristomial layers, as well as an
“under-performance” of unequal cell divisions, resulting in the formula
4:2:4-opposite. The most commonly observed 4:2:3 pattern does not contradict
the placement of Catoscopium among haplolepideous mosses, but at the
same time it does not necessarily confirm this placement, because the 4:2:3
pattern appears to be present in basal arthrodontous mosses, and is not so rare
in diplolepideous alternate mosses at the early stages. The latter was found in
Podperaea, a hypnalean moss with only slightly reduced “perfect”
peristome, involved in the present study for comparison for trait comparisons
with Catoscopium. Likewise, the formula 4:2:4-opposite appears in
unrelated phylogenetic lineages, being in many cases associated with various
patterns of morphological reduction. Phylogenetic analysis based on four
mithochondrial (cobi420, nad2 with nad2i156, nad5 with
nad5i753, nad5-nad4 IGS) and three plastid (rbcL, rps4, trnL
G1) markers is performed, indicating the position of Catoscopium in
relation to groups with 4:2:3 and 4:2:4-opposite and 4:2:4-alternate
peristomial formulae. A method of total peristome structure visualization by
the RGB-coded schemes of the total capsule circumference is introduced.