Pellia appalachiana R.M. Schust. ex L. Söderstr., A. Hagborg & von Konrat
Family: Pelliaceae
Synonyms
None. In naming the species Schuster (1991, 1992) presented the name as Pellia X appalachiana indicating a hybrid origin. His failure to follow new rules of nomenclature (must indicate the herbarium for the type) resulted in the additional authors of the name (see Söderström et al. 2013).
NatureServe Conservation Status
G4
Distribution
Endemic to southeastern U.S.A. Alabama, Georgia, Kentucky, North Carolina, South Carolina, Tennessee. Pellia appalachiana occurs broadly in the southeastern U.S., without affinity to physiographic provinces. Schuster (1992, p. 472) mentioned “possibly similar plants have been seen once, in eastern Minnesota (Schuster 1991a)" [Unfortunately this work was never published.]. Given an increase in critical collecting, it may well be that Pellia appalachiana will prove to be widely distributed in the Midwestern and Northeastern U.S. [The species was not named until 1991 and since then almost all records on the bryophyte portal throughout the known range are those of a single collector, P.G. Davison.]
Habitat
“There is nothing distinctive about the ecology of this plant as compared with the common Pellia epiphylla” (Schuster 1992, p. 473). The three species of Pellia known to occur in the southeastern U.S. (P. appalachiana, P. epiphylla, and P. neesiana) are ecologically similar in their habitat requirements. Each species is intolerant of desiccation and seems to thrive in microhabitats prone to periodic disturbance. This includes stream banks under the influence of episodic scouring events and muddy/rocky shelves associated with waterfalls. When growing on vertical surfaces along streams or at the base of rock shelters, mature mats may eventually slough off making way for early successional colonization from locally dispersed spores. The muddy/rocky floor of wet, sandstone rockhouses is a frequent habitat of the species in parts of northern Alabama. All three species are known to occur sympatrically in at least two locations (Dry Falls, Macon Co., N.C., and Hemlock Bluff, Wake Co., N.C., see Schuster 1992). Except for the occurrence at Dry Falls, elev. ca. 3300 ft,, all other known occurrences are below 2500 ft in elevation.
Almost always occurring in close association with the far more freqeunt P. epiphylla, but apparently unable to colonize "weedy" habitats such as suitably moist and shaded road cut banks and ditches where P. epiphylla often prospers as an aggressive colonizer.
Brief Description and Tips for Identification
Similar to P. epiphylla and P. neesiana. Plants are thalloid, ribbon shaped, up to 1 cm wide and several cm long, furcately branched, occasionally rosette forming, more frequently forming broad mats, thalli overlapping, green, with red pigment when sun exposed. In published descriptions the thallus of Pellia is described as having a costa (midrib); however, the costa is not sharply demarcated and is "rather ill-defined" (Schuster 1992, p. 436). In Pellia the costa refers to the thickened region that runs down the middle of the elongate thallus. Laterally, the costa thins merging with the thallus wings.
Dioicous. Archegonia (and subsequent, developing sporophyte) located on the dorsal surface of the thallus, protected by a posterior flap (a.k.a. involucre, perichaetium, pseudoperianth). Antheridia sunken in dorsal pustules scattered or clustered along the thallus midline.
Features to find for confident identification of Pellia appalachiana are: 1) absence of male structures on plants bearing female structures, and 2) the female involucre extends from a posterior-only position behind the archegonial cluster, AND 3) the female involucre is lobulate-incised, the short lobes often flaring and standing nearly erect. The first character is shared with P. neesiana and male plants of the two species are indistinguishable (Schütz et al. 2016). The second character is shared with the monoicous P. epiphylla. The third character, in combination with the first, is most critical. New growth in the spring typically lacks reproductive structures, thus older thalli possibly buried within the mat collected should be studied.
Differing from both P. epiphylla and P. neesiana in the apparent absence of thickened bands associated with the cell walls within the costa (thickened midregion) of the thallus. The bands are illustrated below for Pellia epiphylla. The presence of thickened bands in any species may depend of the robustness of the midthallus region. This character deserves further study. If reliably found in thin forms of P. epiphylla and male plants of P. neesiana, the absence of thickened bands may be used to reliably distinguish male plants of P. appalachiana. Paton (1999) described both P. neesiana and P. epiphylla in the British Isles as having thickened bands or their thickened bands may be scarce or absent.
There may be distinctions in cell size between our southeastern species of Pellia, but the potential for size overlap and atypical dimensions when growing under particularly wet conditions, makes cell size less than an ideal marker. In plants found growing together, the cells of P. appalachiana are clearly larger than those of P. epiphylla.
While Schuster (1992) emphasized P. appalachiana was likely a hybrid between P. epiphylla and P. neesiana, there is evidence that this is not so (see Natcheva, & Cronberg 2004).
Salient Features
- Dioicous
- Female involucre a posterior flap
- Mouth of the female involucre lobulate-incised, often flaring, ascending
- Cells along the midline of the thallus 55-71 microns wide, larger than those of P. epiphylla (36-50 microns wide) (“median cell” measurements from Schuster 1992).
References
Natcheva, R., & Cronberg, N. 2004. What do we know about hybridization among bryophytes in nature?. Canadian Journal of Botany, 82(12), 1687-1704
Paton, J.A. 1999. The Liverwort Flora of the British Isles. Harley Books, Martins, England
Schuster, R. M. 1991. Diagnoses on new taxa of Hepaticae-1-Jungermanniidae. Journal of the Hattori Botanical Laboratory, (70), p143-150
Schuster, R.M. 1992. The Hepaticae and Anthocerotae of North America East of the Hundreth Meridian Volume V. Field Museum of Natural History, Chicago
Schütz, N., Quandt, D., & Nebel, M. 2016. The position of the genus Apopellia stat. nov. within the Pelliales (Marchantiophytina: Jungermanniopsida). Taxon, 65(2), 221-234
Söderström, L., Hagborg, A., & Von Konrat, M. 2013. Notes on Early Land Plants Today. 19. Validation of two names in Pellia (Pelliaceae, Marchantiophyta). Phytotaxa, 76(3), 39-40
Habitat
Pellia appalachiana
Disturbed soil of an undercut creek bank
Pellia appalachiana
On the vertical face of a creekside rock and on rocky soil on the edge of the creek bank
Pellia appalachiana
Occurring on the floor of this wet, sandstone rockhouse in Alabama, inevitably with P. epiphylla
Habitat
Pellia appalachiana
Newly exposed substrate provides for healthy growth
Pellia appalachiana
Rocky soil along the edge of creek where submerging and scouring inevitably occurs, but infrequently.
Pellia appalachiana
On soil over the base of a vertical rock wall on the bank of a stream. This population with very small embryonic sporophytes in late August, 2018.
Habit
Pellia appalachiana
Occurring with Pallavicinia lyellii (notice the narrow central strand running through the thallus costa), Pellia epiphylla somewhat duller with slightly smaller cells, and the leafy liverwort Nardia lescurii.
Pellia appalachiana
Female plants
Pellia appalachiana
The yellow arrows indicate female involucres; the rosette growth on bare soil suggests this mat originated from very few spores.
Habit
Pellia appalachiana
Shown next to P. epiphylla and P. neesiana for comparison of female involucres.
Pellia appalachiana
Young male pustules above are light in color while older pustules along the thallus midline are darker.
Pellia appalachiana
The antheridial pustules are clustered in a narrow band over the thallus costa.
Morphology
Pellia appalachiana
Wet mount of dissected female involucre.
Pellia appalachiana
A very young female involucre at the thallus growing apex.
Pellia appalachiana
An even younger female involucre with neck of an archegonium protruding.
Morphology
Pellia appalachiana
Yellow arrows indicate elevated female involucres tending to stand erect.
Pellia appalachiana
Arrows indicate female involucres, lobulate-incised.
Pellia appalachiana
At right arrow, a broad, older female involucre at the point of branch origins.
Morphology
Pellia appalachiana
Stalked slime papillae on the ventral thallus near the notch of the growing apex; arrows indicate the crosswall between the stalk and the terminal cell. The images above capture the difficulty you may have in demonstrating this character. The two-celled slime papillae are useful to rule out thalli of Aneura where slime papillae are one celled and sessile.
Pellia appalachiana
Comparison of cell size of the dorsal dermal cells found along the thallus midline of P. appalachiana and P. epiphylla found growing together. Image orientation is such that the thallus margins are to the left and right.
Pellia appalachiana
This comparison with P. epiphylla shows the larger cell size and more ornate mouth of the female involucre in P. appalachiana.
Similar Taxa
Pallavicinia lyellii
The costa of the thallus is more sharply demarcated than in Pellia and a narrow central strand within the costa is easily seen with transmitted light (central strand just visible at the two most left arrows).
Aneura
Aneura does occur admixed with Pellia in wet, seepy habitats and sterile thalli of the two genera can be troubling. While tedious to demonstrate, the apical notch of Aneura is protected ventrally by single-celled, sessile slime papillae while slime papillae of regional Pellia are two celled (the papilla cell subtended by a stalk cell). Pellia prefers mineral substrates and would not be found on non-silt covered logs, a common substrate for Aneura as shown above. Red arrows on the inset indicate the lateral position of archegonial clusters.
Dumortiera
This large, common liverwort of wet habitats is only vaguely similar to Pellia. The margins of vegetative thalli are distinguished from Pellia by the shortly projecting, numerous stiff hairs (modified rhizoids), unless they have been worn away.
Similar Taxa
Pellia neesiana
In distinguishing this dioicous species from the dioicous P. appalachiana care must be taken to demonstrate that the involucre does indeed also arise in front of the archegonial cluster, i.e. anteriorly and forming a complete ring that extends posteriorly.
Pellia neesiana
The mouth of the female involucre is lobulate-incised (at least when young) and similar in this regard to P. appalachiana.
Pellia epiphylla
In most collections, P. epiphylla is quickly identified by the presence of antheridial pustules posterior to the female involucre.
Similar Taxa
Pellia epiphylla
Longitudional section thorough the costal region demonstrating the presence of thickened bands on the cell walls. In thallus cross section these bands would appear to encircle all or part of the cell. The bands may be more easily demonstrated in longitudional sections.
Pellia epiphylla
Antheridial pustules are rather subtle in this mat found growing in a shaded, protected rock shelter.
Pellia epiphylla
As far as known, each of our regional species of Pellia produces mature capsules in early spring, at which time critical characters for species identification requires study of older thalli often overtopped by new growth.
Similar Taxa
Blasia pusilla
Superficially similar to small forms of Pellia, B. pusilla lacks oil bodies [ca. 15-35 oil bodies in cells of Pellia], is more regularly lobate along the thallus margins, produces dorsal, stellate gemmae, and a number of other distinctions making Blasia a very different plant.