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
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.