Stotler, R. E. and B. Crandall-Stotler. (2017). A Synopsis of the liverwort flora of North America north of Mexico. Annals of the Missouri Botanical Garden. 102(4): 574-709, 136.
"Molecular data have also documented the occurrence of cryptic species where diversity is not reflected in morphology. A study of Porella platyphylla (L.) Pfeiff. and P. platyphylloidea (Schwein.) Lindb. by Therrien et al. (1998) supported three genetic groups without any consistent morphological differences. The elater distinctions between these two species discussed in Schuster (1980a: 696, 703) were shown to be erroneous because all morphologies were documented within a single capsule of the type specimen of P. platyphylloidea (Therrien et al., 1998: 12, fig. 12). Because morphological evaluation revealed no diagnostic features, they were regarded as a single species. Similarly, the P. platyphylla accessions incorporated in the study by Hentschel et al. (2007a) resolved a European and North American clade with one North American sample nested in the European clade. They likewise considered both clades as P. platyphylla. Our reliance on morphological discrimination has clearly resulted in merging genetically distinct lineages. Recently, Kadereit et al. (2012) argued that cryptic taxa should be formally named. We, like most taxonomists, are reluctant to do so since populations presently could not be named reliably without molecular data, and in the case of P. platyphylla, not even on a geographical basis. Even though Kreier et al. (2010) included two accessions of “Ptilidium sp. nov.” from Nepal in their phylogenetic study of Ptilidium Nees, they did not formally name this shared haplotype of P. ciliare (L.) Hampe. While phylogenists desire to name every clade, taxonomists require that taxa be visually separated. At least for the present, names are tied to nomenclatural types (see Principle II and Art. 8, McNeill et al., 2012), which are either specimens or illustrations, and it is the morphology of the type that defines the taxon. The taxonomic decisions we present in this synopsis have evolved through an integration of morphological and molecular data and are, of course, subject to change as new knowledge in both areas develops."
I have consulted:
Glime, J. M. (1993). The elfin world of mosses and liverworts of Michigan's Upper Peninsula and Isle Royale. Houghton, Michigan, Isle Royale Natural History Association.
Pope, R. (2016). Mosses, liverworts, and hornworts : a field guide to common bryophytes of the Northeast. Ithaca, Comstock Publishing Associates, a division of Cornell University Press.
Pope notes that ONLY Porella platyphylloidea (Schwein.) Lindb. is found in North America.
So either only P. platyphylloidea is native to North America and there is no Porella platyphylla in North America (Pope) or the taxa should be combined under Porella platyphylla (L.) Pfeiff. based off of:
Stotler, R. E. and B. Crandall-Stotler. (2017). A Synopsis of the liverwort flora of North America north of Mexico. Annals of the Missouri Botanical Garden. 102(4): 574-709, 136.
I have observed this/these taxa and I can not discern different species vs. plasticity myself.
Unintended disagreements occur when a parent (B) is
thinned by swapping a child (E) to another part of the
taxonomic tree, resulting in existing IDs of the parent being interpreted
as disagreements with existing IDs of the swapped child.
Identification
ID 2 of taxon E will be an unintended disagreement with ID 1 of taxon B after the taxon swap
If thinning a parent results in more than 10 unintended disagreements, you
should split the parent after swapping the child to replace existing IDs
of the parent (B) with IDs that don't disagree.
From:
Stotler, R. E. and B. Crandall-Stotler. (2017). A Synopsis of the liverwort flora of North America north of Mexico. Annals of the Missouri Botanical Garden. 102(4): 574-709, 136.
"Molecular data have also documented the occurrence of cryptic species where diversity is not reflected in morphology. A study of Porella platyphylla (L.) Pfeiff. and P. platyphylloidea (Schwein.) Lindb. by Therrien et al. (1998) supported three genetic groups without any consistent morphological differences. The elater distinctions between these two species discussed in Schuster (1980a: 696, 703) were shown to be erroneous because all morphologies were documented within a single capsule of the type specimen of P. platyphylloidea (Therrien et al., 1998: 12, fig. 12). Because morphological evaluation revealed no diagnostic features, they were regarded as a single species. Similarly, the P. platyphylla accessions incorporated in the study by Hentschel et al. (2007a) resolved a European and North American clade with one North American sample nested in the European clade. They likewise considered both clades as P. platyphylla. Our reliance on morphological discrimination has clearly resulted in merging genetically distinct lineages. Recently, Kadereit et al. (2012) argued that cryptic taxa should be formally named. We, like most taxonomists, are reluctant to do so since populations presently could not be named reliably without molecular data, and in the case of P. platyphylla, not even on a geographical basis. Even though Kreier et al. (2010) included two accessions of “Ptilidium sp. nov.” from Nepal in their phylogenetic study of Ptilidium Nees, they did not formally name this shared haplotype of P. ciliare (L.) Hampe. While phylogenists desire to name every clade, taxonomists require that taxa be visually separated. At least for the present, names are tied to nomenclatural types (see Principle II and Art. 8, McNeill et al., 2012), which are either specimens or illustrations, and it is the morphology of the type that defines the taxon. The taxonomic decisions we present in this synopsis have evolved through an integration of morphological and molecular data and are, of course, subject to change as new knowledge in both areas develops."
I have consulted:
Glime, J. M. (1993). The elfin world of mosses and liverworts of Michigan's Upper Peninsula and Isle Royale. Houghton, Michigan, Isle Royale Natural History Association.
Pope, R. (2016). Mosses, liverworts, and hornworts : a field guide to common bryophytes of the Northeast. Ithaca, Comstock Publishing Associates, a division of Cornell University Press.
Pope notes that ONLY Porella platyphylloidea (Schwein.) Lindb. is found in North America.
So either only P. platyphylloidea is native to North America and there is no Porella platyphylla in North America (Pope) or the taxa should be combined under Porella platyphylla (L.) Pfeiff. based off of:
Stotler, R. E. and B. Crandall-Stotler. (2017). A Synopsis of the liverwort flora of North America north of Mexico. Annals of the Missouri Botanical Garden. 102(4): 574-709, 136.
I have observed this/these taxa and I can not discern different species vs. plasticity myself.