Anthurium Schott species with palmately divided leaves (as included in Madison 1978) represent a very distinct morphological group within the genus (Fig. 1). In these species, leaf segments (i.e. leaflets) are free to the base, in palmatisect leaves, or leaf segments (i.e. lobes) are united at the base, in palmatifid leaves (Fig. 2). The current sectional classification of Anthurium (Croat and Sheffer 1983) separates these species into two groups, section Dactylophyllium (Schott) Engler (Engler 1879), comprising species with three or more segments (leaflets) free to the base (Fig. 2A–B), and section Schizoplacium (Schott) Engler (Engler 1879), including species with five or more segments (lobes) united at the base (Fig. 2C). A recent molecular phylogeny (Carlsen 2011, Carlsen and Croat in press) has shown that most of the species of Anthurium with palmately divided leaves belong to a single highly supported clade (Fig. 3, Clade 3), therefore suggesting that previous divisions of the group are unnecessary. Indeed, the newly circumscribed Clade 3 merits sectional rank. Moreover, although all members of Clade 3 share palmately divided leaves, this leaf form has evolved independently at least two more times within Anthurium, in Clades 14 and 16 (Fig. 3). The goal of this study is to reevaluate the limits of sections Dactylophyllium and Schizoplacium in the light of the new molecular evidence and provide an updated description of this redefined group of Anthurium species with palmately divided leaves (Fig. 1).

In the first comprehensive revision of the genus, Schott (1860) classified Anthurium species with lobed or divided leaves in three groups (Table 1): grex Semaeophyllium, comprising species with “hastate-trilobed” blades with segments united at the base; grex Schizoplacium, including species with “pedately-partite” blades with five or more leaf segments united at the base (i.e. palmatifid leaves, according to our definition) (Fig. 2C); and grex Dactylophyllium, containing species with “digitisect” leaf blades with three or more segments divided completely (i.e. free) to the base (i.e. palmatisect leaves, in our definition) (Fig. 2A–B).

Carlsen and Croat (2007) recently revised the 23 species included in Anthurium section Semaeophyllium (Schott) Engler (Engler 1879). The section comprises species with trilobed leaf blades, where leaf lobes are always united at the base, and the lobes can be directed forward (i.e. falcate) or to the sides (i.e. spreading) but never toward the back. On the basis of molecular evidence (Carlsen 2011, Carlsen and Croat in press), section Semaeophyllium appears not to be monophyletic. However, species with trilobed leaves are more closely related to other Anthurium species with cordate leaves than to the species with palmately divided leaf morphology clustered in Clade 3 (Carlsen 2011, Carlsen and Croat in press). Therefore, this paper will only deal with the Anthurium species with palmately divided leaves (Fig. 1), those included in sections Dactylophyllium and Schizoplacium.

Schott (1860) included 27 names in his grex # 28 (Table 1), Dactylophyllium, but according to the most updated species synonymy for the genus (Govaerts et al. 2012), only seven species are currently recognized: Anthurium clavigerum Poepp., Anthurium digitatum (Jacq.) Schott, Anthurium eminens Schott, Anthurium kunthii Poepp., Anthurium pentaphyllum (Aubl.) G.Don, Anthurium sinuatum Benth, and Anthurium triphyllum (Willd. ex Schult.) Brongn. ex Schott. On the other hand, Schott (1860) included seven names in his grex # 27 (Table 1), Schizoplacium, but only four species are now recognized, Anthurium palmatum (L.) Schott, Anthurium pedatoradiatum Schott, Anthurium pedatum (Kunth) Schott, and Anthurium podophyllum (Schltdl. & Cham.) Kunth. Engler (1879) gave formal sectional ranking to these, and others, of Schott’s greges, maintaining the species circumscriptions in both groups.

However, Engler (1905) made major modifications in the classification of Schott. He described his newly circumscribed section Semaeophyllium as comprising species with “hastate-trilobed or pedatisect or digitisect” leaf blades, and very long and relatively thin (i.e. myosuroideous) spadices. Engler (1905) included in his new version of section Semaeophyllium, along with more typical species with trilobed leaves, a pair of species from Schott’s grex Dactylophyllium (namely Anthurium sinuatum and Anthurium clavigerum) and also Anthurium palmatum, previously placed by Schott in grex Schizoplacium. Alternatively, Engler’s amended section Schizoplacium (Engler 1905) included the remaining species of both Schott’s greges Dactylophyllium and Schizoplacium, along with a few more recently described species, for a total of 17 species, of which only eight are currently accepted (Table 1). Engler’s (1905) new delimitation of section Schizoplacium included species with “pedately-partite” leaf blades, with segments either united at the base or completely separated, and thick, conic spadices. He further divided this section into two informal groups, § 1. Euschizoplacium Engler, with short stems and internodes, but long peduncles, and § 2. Dactylophyllium (Schott) Engler, with scandent stems, elongated internodes, but peduncles often short (Engler 1905). Engler placed most of the species from Schott’s grex Schizoplacium in the Euschizoplacium group and the remaining species from Schott’s grex Dactylophyllium in the Dactylophyllium group (Table 1).

The last taxonomic revision of Anthurium species with palmately divided leaves (Madison 1978) recognized 27 species and three varieties divided into seven “natural” groupings based on the author’s understanding of the taxonomy, morphology and growth habit of the species (Table 1). Groups 1–3 included species with trilobed leaves with falcate lobes united at the base now placed in section Semaeophyllium (Carlsen and Croat 2007). The remaining groups in Madison’s (1978) revision included typical examples of species in sections Dactylophyllium and Schizoplacium (Table 1; following Croat and Sheffer 1983). Group 4 contained two terrestrial Mexican species with short stems, elongated peduncles and “pedately divided” (i.e. palmatifid) leaf blades (Anthurium pedatoradiatum and Anthurium podophyllum). Group 5 consisted only of the Colombian species Anthurium pedatum, with deeply dissected leaf blades with 11–15 lobes, and a pendent inflorescence borne on an erect peduncle. Group 6 included climbers with palmately divided leaves with the lobes united at the base (i.e. palmatifid leaves) (Fig. 2C), and elongated spadices, which range from northern Colombia to the West Indies (Anthurium angustisectum Engl., Anthurium expansum Gleason, Anthurium longissimum Pittier and Anthurium palmatum). The species in Madison’s groups 4, 5 and 6 were placed in section Schizoplacium by Croat and Sheffer (1983). His group 7 is a predominantly Amazonian group of species with “digitisect” (i.e. palmatisect) leaf blades, where the leaf segments are free to the base and have a basal pulvinus (Fig. 2A–B), and spadices are purple to gray. Madison called this group section Schizoplacium, apparently following Engler’s (1905) circumscription of that section, but it indeed includes species placed in section Dactylophyllium by both Schott (1860) and Croat and Sheffer (1983) (Table 1).

Croat and Sheffer (1983) provided the previously accepted treatment of the sections of Anthurium with palmately divided leaf blades. Following Schott’s (1860) original classification system, they separated the species of Anthurium with lobed or divided leaf blades into three sections, Semaeophyllium, Schizoplacium and Dactylophyllium (Table 1). They provided a key to the sections, descriptions, and illustrative examples of species belonging to each group.

The current molecular phylogeny of the genus Anthurium, based on chloroplast (trnG intron, trnH–psbA and trnC–ycf6 intergenic spacers) and nuclear (first intron of CHS and partial flanking coding regions) DNA sequences (Carlsen 2011, Carlsen and Croat in press) shows that the palmately divided leaf morphology is homoplasious within the genus, having evolved at least three times independently, in Clades 3, 14 and 16 (Fig. 3).

Based on this molecular phylogeny (Carlsen 2011, Carlsen and Croat in press) (Fig. 3), some of the Anthurium species with palmately divided leaves previously recognized as section Schizoplacium (Schott 1860, Engler 1879, Engler 1905, Croat and Sheffer 1983), do not form a monophyletic group and are not even closely related to other palmately divided species. For example, Anthurium pedatum, a high elevation Colombian species with a highly divided palmatifid leaf blade, consistently clustered in the moderately supported Clade 14 (Fig. 3), along with Anthurium furcatum Sodiro, with trilobed leaves, and Anthurium tremulum Sodiro and Anthurium macleanii Schott, both with cordate leaves. Clade 14 is not easily characterized morphologically, although most of its species have hooded spathes and pendent spadices (Carlsen and Croat in press). Madison (1978) had pointed out the possible segregation of Anthurium pedatum from all other palmately divided Anthurium species by placing it alone in Group 5 of his revised classification. Molecular data now suggests that indeed Anthurium pedatum is not closely related to other palmately divided Anthurium species and therefore does not belong to section Dactylophyllium as currently defined here.

Anthurium pedatoradiatum, a Mexican species with palmatifid leaves and a member of section Schizoplacium (fide Schott 1860, Engler 1879, Engler 1905, Croat and Sheffer 1983), should also be removed from this group. Results of molecular analyses (Carlsen 2011, Carlsen and Croat in press) strongly suggest that it is more closely related to other northern Central American species (Clade 16) than to the clade of Anthurium species with palmately divided leaves (Clade 3) (Fig. 3). The strongly supported Clade 16, although quite variable in terms of leaf morphology, presents very uniform reproductive features, including only species that possess bright orange berries with a mealy mesocarp, characteristics also found in Anthurium pedatoradiatum. Madison (1978) previously separated Anthurium pedatoradiatum from the rest of palmately divided Anthurium species, and grouped it along with the other Mexican species with palmatifid leaves, Anthurium podophyllum, in his Group 4. The latter species have not been sampled for the current molecular phylogeny of Anthurium (Carlsen 2011, Carlsen and Croat in press). However, geographical affinities and similarities in fruit characteristics with other species of Clade 16 (Fig. 3) have made us consider that Anthurium podophyllum is also a member of this clade, and as such, it should be excluded from section Dactylophyllium as delimited here.

There are only four currently recognized species names included in the original description of Schott’s grex Schizoplacium (Schott 1860), all of which match well the protologue of the section. However, according to molecular studies (Carlsen 2011, Carlsen and Croat in press) (Fig. 3), Anthurium pedatum, Anthurium pedatoradiatum, and very likely Anthurium podophyllum, do not belong to the same clade and are not closely related to other palmately divided Anthurium species. Therefore, these three species are also excluded from section Dactylophyllium according to the circumscription presented here. Thus, of the initial group, only Anthurium palmatum remains. This climbing plant with elongated internodes and palmatifid leaves (Fig. 2C), restricted to the Lesser Antilles, is therefore here selected as the lectotype species for section Schizoplacium. Two other Anthurium species with palmatifid leaves (Anthurium expansum and Anthurium longissimum) (Fig. 1B) also belong to this section under its traditional circumscription (Table 1). Anthurium palmatum was not sampled in the current molecular phylogeny of the genus (Carlsen 2011, Carlsen and Croat in press) (Fig. 3), but the closely related Anthurium longissimum, with which it shares climbing habit, palmatifid leaf morphology, peduncle shorter than the petiole, green spathe, grayish purple spadix and reddish-purple berries, was used as a representative of this group of palmatifid species.

The molecular phylogeny of Anthurium (Carlsen 2011, Carlsen and Croat in press) clearly shows that most of the palmately divided species sampled in the study (except for Anthurium pedatum and Anthurium pedatoradiatum), belong in a single clade, Clade 3 (Fig. 3). These species were previously included in either section Schizoplacium (e.g. Anthurium longissimum, a representative of the group with palmatifid leaves) or section Dactylophyllium by Croat and Sheffer (1983). The findings of molecular analyses indicate that the group of species with palmatifid leaf morphology (i.e. Anthurium longissimum, Anthurium palmatum and Anthurium expansum) (Figs 1B, 2C), all sharing similar vegetative and reproductive characters, is not distinct from other species with palmately divided leaves. Thus, these two sections are here combined, and the morphological limits of this emended, more inclusive, group are redefined.

In terms of nomenclatural choice, since both names, Schizoplacium and Dactylophyllium, were published, albeit without a formal rank (i.e. as grex names), at the same time in Schott’s (1860) revision of the genus Anthurium, and were later simultaneously formalized as sections by Engler (1879), none of them has priority over the other. Therefore, in this study, section Schizoplacium, the smaller (probably containing only three currently accepted species names) and geographically more isolated group (mainly occurring in the Lesser Antilles and Cordillera de la Costa in Venezuela) has been placed into synonymy with the larger (probably including a total of 21 species, some undescribed) and more widespread group, section Dactylophyllium.

Anthurium kunthii (Fig. 2A) is here chosen as the lectotype for this emended section Dactylophyllium for several reasons. Anthurium kunthii was among the original species included in Schott’s (1860) first delimitation of the group and represents very well the morphological characters described in the protologue. Also, this species was sampled in the current molecular phylogeny of the genus (Carlsen 2011, Carlsen and Croat in press) (Fig. 3), and it clearly belongs to the group of species with palmately divided leaves in Clade 3. Additionally, Anthurium kunthii is among the oldest species described within the group (in 1845) (Table 1), but unlike Anthurium digitatum (the oldest described species, from 1829), its taxonomic status as a species has not been previously questioned.

The following section provides an updated description of Anthurium section Dactylophyllium (Schott) Engler, emend. Croat & Carlsen, and lists all currently recognized species now comprising this group and their known geographic distribution.