Nephrolepidaceae

Primary tabs

Nephrolepidaceae

Distribution

Neotropical: present Pacific:, Hawaiipresent Pantropical: present Polynesia: present Southeast Asia: present Southern America: tropical America: present
The genus as well as a small number of species are pantropical, but most species have a more limited distribution in either Southeast Asia or Tropical America. The phylogeny and biogeography were analyzed by Hennequin et al. (2010) who found that the Neotropical and Paleotropical species form two distinct clades, with the widespread species N. abrupta, N. biserrata, N. cordifolia and N. undulata nested in the Paleotropical clade. Brown & Brown (1931) state for all species of Nephrolepis that they can “reasonably be considered as aboriginally introduced” in Southeast Polynesia. If true, that would suggest a contact between the native population on Hawaii with Caribbean tribes to explain the occurrence of N. exaltata on Hawaii.

Morphology

The morphology of Nephrolepis has been studied extensively and in great detail (Heinricher 1907; Sen & Sen 1973; Nayar & Bajpai 1978).

Taxonomy

The genus Nephrolepis was established by Schott (1834) to accommodate a number of species until then included in Aspidium, Nephrodium and Polypodium, which he distinguished on the basis of the venation pattern and soral position. The genus was quickly adopted by Presl (1836), who further diagnosed it by the presence of articulate pinnae. Presl added a number of species (including a few now no longer included in Nephrolepis), and erected the genus Leptopleuria for N. abrupta, a taxon with an aberrant soral position. The articulated pinnae were accepted as characteristic for the genus by Smith (1841, 1842), who also recognized the correct affinity of N. abrupta. The modern circumscription of Nephrolepis was attained when Smith (1857, 1866, 1875) distinguished both Nephrolepis and Arthropteris in the modern sense, using the differences in articulation and the stoloniferous habit of Nephrolepis as generic characters. Hooker (1862), mistakenly included Arthropteris palisotii (with the misapplied name N. obliterata) as a species “peculiar in the genus”, and also introduced the erroneous notion that N. exaltata is a pantropical species, thus laying the groundwork for many misidentifications and the misconception that Nephrolepis is a particularly difficult genus, expressed by, e.g., Copeland (1947).

In the modern circumscription, Nephrolepis is accepted in most recent floristic and horticultural accounts, e.g., Nauman (1985, 1992), Proctor (1989), Hoshizaki & Moran (2001), Mickel & Smith (2004), Hovenkamp & Miyamoto (2005).

Cytology

Basic chromosome number is 41 for all species investigated so far, and most species appear to contain diploids only, with additional tetraploids reported in two species (Löve et al. 1977; Tindale & Roy 2002): in N. hirsutula in South India (probably this record refers to N. brownii) and in N. pectinata in Jamaica. Hybridization under natural circumstances occurs occasionally (Nauman 1979), but is probably far less common than sometimes supposed; the rampant hybridity suggested by some authors can probably for a large part be explained by an incomplete understanding of the natural species. In cultivation, most of the variation being offered on the market is due to the occurrence of vegetative ‘sports’ (Benedict 1916) and artificial hybridization plays a minor role, if any at all.

Notes

In considering this a monogeneric family we follow the treatment in the Families and Genera of Vacular Plants (Kramer 1990). In the past, Nephrolepis was considered to be variously allied with Davallia, Oleandra and/or Arthropteris in Nephrolepidaceae, Oleandraceaea or Davalliaceaea (see Pichi Sermolli 1974 for a concise review), but both molecular phylogenies and morphological data disagree with that position. Molecular phylogenies (Hasebe et al. 1995; Liu et al. 2007; Schuettpelz & Pryer 2008) indicate separate positions for all of these genera, while morphologically, Nephrolepis is a highly distinct genus, with the unique character of the very distinctive stolons and although recent studies suggest that it should be aligned with Lomariopsis and Cyclopeltis (Smith et al. 2006) we here maintain it for the time being in its own family.

Citation

K.U.Kramer - in K.U.Kramer & P.S.Green (eds.), Fam. Gen. Vasc. Pl. 1990: 188