Innovations subperichaetial

Vouchers for scoring of characters for taxa in grade R and in the hypnodendroid pleurocarp clade are provided in Table 3.1. Taxa in the Hypnidae were assumed to be pleurocarpous with distally produced perichaetial modules and to lack subperichaetial innovations, and taxa outside of the clade that includes grade R and the higher pleurocarps were assumed not to be pleurocarpous. Perichaetial module position and presence/absence of subperichaetial innovations were considered applicable to pleurocarpous taxa only (see discussion). 

FIGURE 3.4 Optimization of presence/absence of subperichaetial innovations on pleurocarpous perichaetial modules onto tree C. (A) Under accelerated transformation (ACCTRAN). Continued. 

An alternative coding strategy would be to treat one or more of the various forms of pleurocarpy found in grade R as separate states of a single character in which acrocarpy and conventional pleurocarpy were also states. This would inappropriately link characters that appear to vary independently, however, such as pleurocarpy sensu stricto and production of subperichaetial innovations. The result would be a highly artificial character with a large number of states, in which transformational independence would be compromised (Lee and Bryant, 1999). 

FIGURE 14.5 Architecture of pleurocarpous mosses characters 11 to 12 (perichaetial module origin and sub-perichaetial innovations). (A) Perichaetial modnles formed distaUy on primary modnles and on secondary modules, subperichaetial innovations absent (Pireella) (B) perichaetial modnles basal on primary modules, subperichaetial innovations present, fertile only (Pyrrhobryum) (C) perichaetial modules formed distaUy on primary module, subperichaetial innovations present, fertile only (Cryphaea) (D) perichaetial modnles formed nonspecificaUy on primary module, subperichaetial innovations present, both fertile and vegetative (Amblystegium). 

In Rhizogonium and Pyrrhobryum Section Pyrrhobryum, innovations on the perichaetial modules form new perichaetial modules (Figure 14.5B), but not vegetative primary modules (discussed further in Chapter 3). The placement of these taxa in the pleurocarpous mosses, in a basal grade containing several acrocarpous taxa (BeU and Newton, 2005, see also Chapter 3), could indicate that the presence of subperichaetial innovations in these taxa is a retained plesiomorphic condition, whereas in taxa such as Amblystegium this condition is an independently derived reversal. 

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