Tectaria (Schuettpelz & Pryer, 2007)

Wang, Fa-Guo, Barratt, Sam, Falcón, Wilfredo, Fay, Michael F., Lehtonen, Samuli, Tuomisto, Hanna, Xing, Fu-Wu & Christenhusz, Maarten J. M., 2014, On the monophyly of subfamily Tectarioideae (Polypodiaceae) and the phylogenetic placement of some associated fern genera, Phytotaxa 164 (1), pp. 1-16 : 11

Relationships within Tectaria : the undivided leaves unraveled

Our phylogenetic tree shows that the Tectaria clade is composed of three clades all with strong support and each with a different geographical distribution: one is Palaeotropical ( Tectaria I), one is Neotropical ( Tectaria II ) and one is South-East Asian ( Tectaria III ). Tectaria clade III includes the peculiar genus Cionidium , an endemic to New Caledonia, which was segregated because of its extramarginal (stalked) sori and lanceolate, non-clathrate scales. Even though Bower (1928) placed Cionidium moorei in Deparia Hook. & Grev. , it resembles Tectaria in most other characters, except the sori. Copeland (1947) therefore considered it most closely related to T. seemannii (E.Fourn.) Copeland (1929: 359) , another New Caledonian species. Our phylogenetic analyses places Cionidium with reasonable support in a clade comprised of the South-East Asian species T. impressa (Fée) Holttum (1988: 483) and T. simonsii (Baker) Ching (1931: 32) and the more widespread T. devexa (Kunze) Copeland (1907: 415) , which extends into Polynesia.

The Neotropical clade Tectaria I includes T. trifoliata (L.) Cavanilles (1802: 249), which is the type species of the genus. We also included two samples of T. incisa and one of its synonyms, T. martinicensis (Spreng.) Copeland (1907: 410) . This taxon is variable and taxonomically complex and probably includes more than one species. Indeed, the three specimens were not resolved together, indicating that this species is not monophyletic. A more detailed study of the T. incisa complex using morphological and molecular characters will be needed to tease this species complex apart and allow its biogeography to be discussed. Taxonomic study of this species complex is important because of its weedy and invasive nature and possibility of hybridisation with other taxa ( Wagner et al. 1978, Gordon & Thomas 1997).

Fadyenia prolifera Hooker (in Hooker & Bauer 1840: t53-B) is a Caribbean species that was originally separated from Tectaria because of its simple proliferous leaves and peculiar lunate indusia ( Hooker & Bauer 1840). Later it was placed in Tectaria because of its anastomosing veins forming elongate areoles ( Tryon & Tryon 1981), a placement which was corroborated by molecular studies ( Schuettpelz & Pryer 2007). In our analyses, T. prolifera (Hook.) Tryon & Tryon (1981: 136) was found to be sister to T. panamensis , the type species of the segregate genus Dictyoxiphium . Since Dracoglossum has been excluded from Tectaria , T. panamensis and T. prolifera are the only Neotropical species in the genus with simple leaves. However, separating them from other Tectaria spp. at a generic level is not justified according to our results, because their lineage is deeply embedded in the Neotropical clade of Tectaria . Tectaria panamensis is also known to hybridize with T. incisa , resulting in sterile plants with intermediate leaf division ( Wagner et al. 1978). Because most juvenile sporophyte leaves are simple, it has been suggested that entire leaves in adults belonging to lineages with generally divided leaves are a form of paedomorphy or neoteny, simple leaves having evolved through reduction, as is also seen in Marattiaceae ( Stidd 1974, Christenhusz et al. 2008, Christenhusz 2010a) and Marsileaceae ( Pryer & Hearn 2009) .

In Tectaria clade I, about four lineages can be recognized, although some with weak support only. The genus Ctenitopsis (here represented by Tectaria fuscipes (Wall. ex Bedd.) Christensen 1931: 290 , T. kusukusensis (Hayata) Lellinger 1968: 157 , T. sagenioides (Mett.) Christenhusz 2010b: 58 and T. subsageniacea (Christ) Christenhusz 2010b: 59 ), has been segregated from Tectaria on the basis of partially anastomosing veins and absence of included veinlets ( Tardieu-Blot & Christensen 1938). However, in our analyses it forms a well supported clade that is deeply embedded in Tectaria . A second set of species with simple leaves showing paedomorphy is found in Tectaria clade I: Tectaria singaporiana (Wall. ex Hook. & Grev.) Copeland (1917: 368) , the type species of former segregate genus Podopeltis , is sister to T. harlandii (Hook.) Kuo (2002: 173) , the latter species previously known as Hemigramma decurrens (Hook.) Copeland (1928: 404 ; see Xing et al. 2013). Both species have simple leaves (although they are deeply lobed in T. harlandii ) and sporangia with confluent sori along the veinlets. This is different from typical Tectaria spp. , which have sporangia in distinct round sori.

Another segregate genus with simple leaves is Quercifilix . This genus has dimorphic leaves with the fertile leaves having laminae that are much contracted and with sporangia placed densely along veinlets. However, Quercifilix ( T. zeilanica (Houtt.) Sledge 1972: 422 ), Podopeltis ( T. singaporiana ) and Hemigramma ( T. harlandii ) all have the more or less anastomosing veins that form copious areoles typical of many Tectaria . Holttum (1988) did not recognize Hemigramma as a natural group, but showed that its species are similar to Tectaria . The condition of leaf dimorphism has arisen many times in ferns, in Tectaria alone at least eight times according to the results of our phylogenetic analysis. Tectaria also contains species with partial leaf dimorphism: the fertile leaves are otherwise similar to sterile ones, but are more contracted and/or have longer petioles. The segregate genera Fadyenia , Hemigramma, Podolepis and Quercifilix were all based on leaf dimorphism but are now included in Tectaria ( Kramer et al. 1990, Smith 1995, Schuettpelz & Pryer 2007, Christenhusz et al. 2011), and it is more likely that they are derived through reduction and paedomorphy as has been suggested for other fern families (e.g. Asama 1960, Stidd 1974, Pryer & Hearn 2009, Christenhusz 2010a).