Belongs within: Polypodiales.
The Davalliaceae are a family of mostly epiphytic ferns found in tropical and warm-temperate parts of the Old World. Fronds bear elongate sori in terminal positions on veinlets.
From tree moss to tree ferns
Published 24 May 2011
Epiphytes seem to be the way to go here lately: after having covered a family of epiphytic mosses last week, I’m going to move on to a family of epiphytic ferns. The Davalliaceae are found in tropical and warm-temperate parts of the Old World. A few species are terrestrial but the majority are good old tree-huggers, either climbing up a suitable tree from roots attached to the ground or living entirely free of the tyranny of soil.
As a group, Davalliaceae are characterised by their elongate sori (spore-pouches) in marginal positions on the fronds at the junction of branching veins. The sori are covered by an indusium prior to maturity. Like other epiphytic ferns, the Davalliaceae also have creeping rhizomes covered by closely appressed scales. The most recent generic revision of the family recognises five genera (Kato & Tsutsumi 2008) but this aspect of Davalliaceae has always been unsettled. Phylogenetically, the Davalliaceae seem to belong in a clade that also includes the families Polypodiaceae and Grammitidaceae (Tsutsumi & Kato 2006). As these families are also primarily epiphytic, it seems likely that this lifestyle was ancestral for this clade. This would make the polypodioid-davallioid clade the largest assemblage of epiphytes among the ferns. It is also worth noting that these families probably diverged from each other some time in the early Tertiary (Schneider et al. 2004). Something that really does not get enough appreciation is that, despite the linear presentation of plant evolution that plagues most textbooks (bryophytes being replaced by ferns, which are shoved aside by conifers, that bow down before the all-conquering flowering plants), a significant percentage of the major fern lineages around today are actually much younger than the major flowering plant lineages.
One final detail that’s of patriotic interest to me: fossil Davalliaceae are known from the Miocene of New Zealand (Conran et al. 2010). These days Davalliaceae hang on in New Zealand by the skin of their rhizomes, with only a single species represented in the northernmost part of the country by asexually-reproducing individuals only (many fern species are able to survive by reproducing asexually in habitats where conditions do not permit sexual reproduction). This means that, along with coconuts, cone shells and crocodiles, Davalliaceae were part of a diverse biota that inhabited New Zealand during the balmy Miocene, only to decline and disappear as conditions became cooler.
Systematics of Davalliaceae
Characters (from Kramer 1990): Epiphytic, less often epilithic or terrestrial ferns with short- to long-creeping, fleshy stem; cortex little sclerotic; stele a peculiar type of strongly dorsiventral dictyostele, only some perforations associated with leaf traces. Stem densely and permanently clothed in scales with often cordate or peltate base, the scales often toothed, sometimes clathrate; surface and/or margin of scales bearing hairs, these glandular or not; rarely hairs on stem beside scales. Roots mostly ventral. Leaves inserted in two alternate rows on dorsal side of stem, on short phyllopodia, with a functional articulation at base of petiole. Petiole more or less sclerotic, with two lateral, almost continuous pneumatophores, with two large adaxial and a varying number of smaller abaxial bundles (in some species only one or none), all together forming a U or a semi-circle; petiole usually long, stramineous to brown, adaxially flattened or more often with a groove, this continuous with grooves on axes of higher order, middle of groove usually raised, ridge-like. Lamina mostly simply pinnate to several times pinnate + pinnatifid, rarely simple, occasionally weakly to strongly dimorphic; axes adaxially grooved, grooves with raised centre; edges of laminal parts continuous with ridges (wings) bordering axis groove; costae and costules adaxially convex. Lamina often firm in texture, usually triangular, less often narrowed at base, when mature mostly without macroscopical epidermal appendages; dissection pattern anadromous or occasionally catadromous or isodromous. Ultimate free divisions dentate to pinnatifid, less often entire. Veins pinnately branched, free, ending behind margin, rarely reaching it; costae adaxially not grooved; “false veins” occasionally present between true veins. Stomata polocytic. Sori terminal on anterior fork of a vein, or situated in the fork (but one of the branches may be reduced), near the margin, nearly always uninerval, isodiametric or longer than wide; indusium attached at base, often also at sides or part of them, rarely reniform, with a short point of attachment, or absent; outer edge free, equalling margin or not; segments not rarely protracted into small projections flanking sori. Soral trichomes present or not. Receptacle not elevated; sporangia long-stalked, stalk proximally 1- or 2-seriate, distally 3-seriate. Annulus vertical, indurated part not reaching stalk or stomium. Spores monolete.
<==Davalliaceae
| i. s.: Gymnogrammitis dareiformis (Hooker) Ching ex Tard. & Christensen in Lecomte 1939 (see below for synonymy)I88
| PachypleuriaI88
|--+--DavallodesSP09
| | |--D. borneenseSP09
| | `--D. membranulosum (Wallich) Copel. 1927 (see below for synonymy)I88
| `--AraiostegiaSP09
| |--A. beddomei (Hope) Ching 1959 [=Davallia beddomei Hope 1899]I88
| |--A. delavayi (Bedd.) Ching 1959 [=Davallia pulchra var. delavayi Bedd. ex Clarke & Baker 1888]I88
| |--A. hookeri (Moore) Ching 1959 (see below for synonymy)I88
| |--A. hymenophylloidesSP09
| |--A. multidentata (Hooker & Baker) Copel. 1927 (see below for synonymy)I88
| |--A. pseudocystopteris (Kunze) Copel. (see below for synonymy)I88
| `--A. pulchra (Don) Copel. 1927 [=Davallia pulchra Don 1825, Leucostegia pulchra (Don) Smith 1842]I88
`--Davallia Smith 1793SP09, A61
|--D. angustataT=W89
|--D. australisT86
|--D. bullataT-W89
|--D. canariensisC06 [=Trichomanes canarienseV97]
|--D. clarkei Baker in Hooker & Baker 1874SS04, I88 [=Araiostegia clarkei (Baker) Copel. 1927I88]
|--D. contiguaT-W89
|--D. denticulataSS04
|--D. divaricataT-W89
|--D. dubia [=Dicksonia dubia; incl. Balantium brownianum]B78
|--D. elegansBS-V28
|--D. emersoni [=Prosaptia emersoni]T-W89
|--D. epiphyllaT-W89
|--D. falcataV97
|--D. forsteriC06 [incl. Adiantum clavatumC06, D. clavataBS-V28]
|--D. gibberosaBS-V28
|--D. griffithiana Hooker 1846 [=Humata griffithiana (Hooker) Christensen 1931]I88
|--D. heterophylla [=Humata heterophylla]T-W89
|--D. hymenophylloidesT-W89
|--D. moluccanaT-W89
|--D. pedataB78
|--D. pinnata [=Microlepia pinnata]T-W89
|--D. pyxidataW95
|--D. remotaBS-V28
|--D. solidaB78
|--D. tasmanii Field 1890 [=D. tasmani Cheeseman 1891]A61
|--D. trichomanoides Blume 1828 [incl. D. bullata Wallich ex Hooker 1846]I88
`--D. tripinnataB78
Araiostegia hookeri (Moore) Ching 1959 [=Acrophorus hookeri Moore ex Bedd. 1865, Leucostegia hookeri (Moore) Bedd. 1883]I88
Araiostegia multidentata (Hooker & Baker) Copel. 1927 [=Davallia multidentata Hooker & Baker 1867, Leucostegia multidentata (Hooker & Baker) Bedd. 1876]I88
Araiostegia pseudocystopteris (Kunze) Copel. [=Davallia pseudocystopteris Kunze 1850, D. pulchra var. pseudocystopteris (Kunze) Clarke 1880, Leucostegia pseudocystopteris (Kunze) Bedd. 1876]I88
Davallodes membranulosum (Wallich) Copel. 1927 [=Davallia membranulosa Wallich ex Hooker 1846, Araiostegia membranulosa (Hooker) Holtt. ex Sen, Sen & Holtt. 1972, Leucostegia membranulosa (Wallich) Smith 1875]I88
Gymnogrammitis dareiformis (Hooker) Ching ex Tard. & Christensen in Lecomte 1939 [=Polypodium dareiforme Hooker 1860, Araiostegia dareiformis (Hooker) Copel. 1931, Davallia dareiformis (Hooker) Levinge ex Clarke 1880]I88
*Type species of generic name indicated
References
[A61] Allan, H. H. 1961. Flora of New Zealand vol. 1. Indigenous Tracheophyta: Psilopsida, Lycopsida, Filicopsida, Gymnospermae, Dicotyledones. R. E. Owen, Government Printer: Wellington (New Zealand).
[B78] Bentham, G. 1878. Flora Australiensis: A description of the plants of the Australian Territory vol. 7. Roxburghiaceae to Filices. L. Reeve & Co.: London.
[BS-V28] Bory de Saint-Vincent, J. B. 1828. Voyage Autour du Monde, Exécuté par Ordre du Roi, Sur la Corvette de Sa Majesté, La Coquille, pendant les années 1822, 1823, 1824 et 1825. Botanique. Cryptogamie. Arthus Bertrand: Paris.
[C06] Cheeseman, T. F. 1906. Manual of the New Zealand Flora. John Mackay, Government Printer: Wellington.
Conran, J. G., U. Kaulfuss, J. M. Bannister, D. C. Mildenhall & D. E. Lee. 2010. Davallia (Polypodiales: Davalliaceae) macrofossils from Early Miocene Otago (New Zealand) with in situ spores. Review of Palaeobotany and Palynology 162 (1): 84–94.
[I88] Iwatsuki, K. 1988. An enumeration of the pteridophytes of Nepal. In: Ohba, H., & S. B. Malla (eds) The Himalayan Plants vol. 1. The University Museum, University of Tokyo, Bulletin 31: 231–339.
Kato, M., & C. Tsutsumi. 2008. Generic classification of Davalliaceae. Acta Phytotaxonomica et Geobotanica 59 (1): 1–19.
Kramer, K. U. 1990. Davalliaceae. In: Kramer, K. U., & P. S. Green (eds) The Families and Genera of Vascular Plants vol. 1. Pteridophytes and Gymnosperms pp. 74–81. Springer.
[SS04] Schneider, H., E. Schuettpelz, K. M. Pryer, R. Cranfill, S. Magallón & R. Lupia. 2004. Ferns diversified in the shadow of angiosperms. Nature 428: 553–557.
[SP09] Schuettpelz, E., & K. M. Pryer. 2009. Evidence for a Cenozoic radiation of ferns in an angiosperm-dominated canopy. Proceedings of the National Academy of Sciences of the USA 106 (27): 11200–11205.
[T-W89] Tenison-Woods, J. E. 1889. On the vegetation of Malaysia. Proceedings of the Linnean Society of New South Wales, series 2, 4 (1): 9–106, pls 1–9.
[T86] Trebeck, P. N. 1886. Mount Wilson and its ferns. Proceedings of the Linnean Society of New South Wales, series 2, 1 (2): 491–496.
Tsutsumi, C., & M. Kato. 2006. Evolution of epiphytes in Davalliaceae and related ferns. Botanical Journal of the Linnean Society 151 (4): 495–510.
[V97] Ventenat, C. 1797. Extrait d’un mémoire sur les fougeres, de M. Smith. Bulletin des Sciences, par la Societé Philomathique de Paris 1 (9): 71–72.
[W95] Walter, D. E. 1995. Dancing on the head of a pin: mites in the rainforest canopy. Records of the Western Australian Museum Supplement 52: 49–53.