Leskeaceae
Plants in mats or patches, green, golden green, brown-green, or blackish, rarely with orange or red tinge. Stems slender, creeping, irregularly branched, sometimes unbranched, rarely regularly pinnate, branches (secondary and tertiary) spreading to erect, sometimes clustered, branching monopodial, older portion of primary stem often becoming stoloniferous; paraphyllia present or absent, unbranched or sometimes branched; pseudoparaphyllia foliose to linear or peglike; rhizoids few, usually arising from base of leaves. Stem and branch leaves usually similar, rarely differentiated. Stem leaves appressed to erect when dry, erect to erect-spreading or rarely squarrose when moist, ovate, ovate-lanceolate, or oblong, symmetric or sometimes asymmetric, not to distinctly plicate on either side of costa; margins plane to recurved, entire to serrate distally, limbidium absent or rarely present; apex broadly rounded, acute, or acuminate; ecostate to costa percurrent, sometimes 2-fid, occasionally sinuate distally; alar cells shorter than laminal cells, isodiametric to transversely elongate, region usually distinct; laminal cells isodiametric to elongate-rhomboidal or linear-fusiform, often prosenchymatous, sometimes obscure or opaque, smooth, papillose over lumen, or prorulose distally, walls thin to usually firm or thick, rarely pitted. Branch leaves often smaller; apex sometimes less acute; costa weaker. Specialized asexual reproduction rarely present, of clustered flagelliform branchlets in axils of distal branch leaves. Sexual condition dioicous or autoicous; perigonia budlike, on primary stems; perichaetial leaves on primary stems or rarely secondary branches, differentiated, opaque to translucent, apex longer, more acuminate than stem and branch leaves, costa short to excurrent. Seta elongate, thin, straight or somewhat curved, often twisted. Capsule erect to horizontal, long-exserted, oblong to pyriform, symmetric to asymmetric-curved, smooth; stomata absent or present, phaneropore; annulus absent or present; operculum conic, short- to long-rostrate; peristome double, perfect to variously reduced; exostome teeth lanceolate or linear-lanceolate, lamellae present, sometimes faint or absent, striolate to densely papillose; endostome basal membrane low to high, free or sometimes adherent to exostome at base, segments broad and keeled to linear, sometimes absent, cilia well developed to rudimentary or absent. Calyptra usually cucullate, small, fugacious, usually smooth. Spores smooth to variously roughened.
Distribution
Nearly worldwide except Antarctica.
Discussion
Genera ca. 18, species ca. 80 (9 genera, 28 species in the flora).
Leskeaceae is a heterogeneous family, with genera exhibiting widely divergent morphologies, and with some taxa more closely related to Anomodontaceae, Pterigynandraceae, and Thuidiaceae (J. R. Spence 1996). Recent molecular studies confirm this phylogenetic heterogeneity (A. M. Gardiner et al. 2005; M. S. Ignatov et al. 2006; D. García-Avila et al. 2009), and suggest that there are at least three distinct groups of core genera, centered around Lescuraea, Leskea, and Pseudoleskeella, respectively. Although there is some merit in recognizing Pseudoleskeaceae, following W. P. Schimper, for Lescuraea, Pseudoleskea, Ptychodium, and Rigodiadelphus, this does not solve the problem of where to place Pseudoleskeella. Morphological and molecular evidence also suggests that Claopodium is near Anomodon, and Leptopterigynandrum near Heterocladium. On the other hand, core Leskeaceae, including Haplocladium, Leskea, and Lindbergia, are phylogenetically closer to Thuidiaceae than to the Pseudoleskeaceae group. A. Vanderpoorten et al. (2003b) have shown that Platylomella, currently in Amblystegiaceae, may be close to the Leskeaceae-Thuidiaceae clade, although its correct placement remains unresolved. The original concepts of Leskeaceae and Thuidiaceae, based on sporophyte characters (W. R. Buck and H. A. Crum 1990), are not supported by either gametophyte morphology or molecular data (Spence; Gardiner et al.).
Selected References
Lower Taxa
Illustrations
Key
| 1 | Stems with paraphyllia present or rarely absent | > 2 |
| 1 | Stems with paraphyllia absent | > 7 |
| 2 | Leaf hair-points or long-acuminate apices usually present; limbidium sometimes present; costae pellucid; medial laminal cells finely and obscurely 1- or multipapillose over lumen. | Claopodium |
| 2 | Leaf hair-points or long-acuminate apices absent; limbidium absent; costae opaque; medial laminal cells papillose over lumen, prorulose, or smooth | > 3 |
| 3 | Stem and branch leaves dimorphic; stems ± pinnate; paraphyllia cells papillose. | Haplocladium |
| 3 | Stem and branch leaves similar; stems irregularly branched or unbranched; paraphyllia cells smooth or prorulose | > 4 |
| 4 | Medial laminal cells prorulose or smooth | > 5 |
| 4 | Medial laminal cells distinctly papillose over lumen | > 6 |
| 5 | Medial laminal cells more than 4:1, walls thin; proximal cells more than 3:1; capsules erect, symmetric. | Lescuraea |
| 5 | Medial laminal cells 2-3:1, walls firm to thick; proximal cells usually 1-2:1; capsules inclined, asymmetric. | Pseudoleskea |
| 6 | Leaves oblong-ovate or ovate-lanceolate; apices acute, acuminate, or obtuse; apical cells ± quadrate except at very tip; paraphyllia few; sexual condition autoicous; capsules erect; peristome reduced; on bark of trees, occasionally rock, lower elevations. | Leskea |
| 6 | Leaves ovate-lanceolate; apices acuminate; apical cells elongate; paraphyllia usually many; sexual condition dioicous; capsules inclined; peristome well developed; on soil or rock, montane. | Pseudoleskea |
| 7 | Costae strong, single, more than 1/2 leaf length; leaves wide-spreading to squarrose when moist; medial laminal cells 1-papillose over lumen. | Lindbergia |
| 7 | Costae strong and single to weak, short, single or double; leaves erect-spreading when moist; medial laminal cells prorulose, smooth, or papillose | > 8 |
| 8 | Leaf hair -points present; proximal laminal cells 3-4:1, walls pitted. | Pseudoleskea |
| 8 | Leaf hair-points absent; proximal laminal cells 1-2:1, walls not or obscurely pitted | > 9 |
| 9 | Costae less than 1/2 leaf length, not obscure distally, sometimes double, rarely nearly ecostate | > 10 |
| 9 | Costae more than 1/2 leaf length to percurrent, often obscure distally, single | > 11 |
| 10 | Leaves strongly appressed; medial laminal cells papillose. | Leptopterigynandrum |
| 10 | Leaves catenulate; medial laminal cells smooth. | Pseudoleskeella |
| 11 | Leaves not to weakly plicate; branches erect, clustered; brood branchlets present; medial laminal cells mixed isodiametric, to 2:1; capsules erect to inclined, symmetric; peristome reduced. | Leskeella |
| 11 | Leaves plicate; branches not erect or clustered; brood branchlets absent; medial laminal cells usually elongate, (2-)3:1; capsules inclined, asymmetric; peristome well developed. | Pseudoleskeella |