∫1. Novarum Flora Lusitana Commentarii

In memoriam A.R. Pinto da Silva (1912 – 1992)

Sonchus parathalassius J.G. Costa ex R. Jardim & M. Seq., a new species from Porto Santo Island (Madeira Archipelago)

Roberto Jardim, Centro de Ciências da Vida, Universidade da Madeira, 9000 - 390 Funchal, Portugal; Escola Secundária de Francisco Franco, Rua João de Deus, 9, 9054-527 Funchal, Portugal, rjardim@netmadeira.com;

Miguel Menezes de Sequeira, Centro de Ciências da Vida, Universidade da Madeira, 9000 - 390 Funchal, Portugal, sequeira@uma.pt

The woody pachycaulous species of Sonchus L. (Asteraceae) are included in subgenus Dendrosonchus Sch. Bip. ex Boulos and are endemic to the macaronesian archipelagos of Canaries (14 species), Madeira (3 species) and Cape Verde (1 species), except for one species common to Canary Islands and western cost of Morocco (BOULOS, 1972, 1974; LEE et al., 2005). In Madeira Archipelago this subgenus was so far thought to be represented by 4 endemic taxa, Sonchus fruticosus L. f., S. pinnatus Aiton, S. ustulatus Lowe subsp. ustulatus and S. ustulatus subsp. maderensis Aldridge (PRESS, 1994; JARDIM & MENEZES DE SEQUEIRA, 2008).

COSTA (1946, 1948) listed species from 20 families (Ranunculaceae to Leguminosae) and described new taxa according to the plant list order, Fumaria muralis Sond. ex W.D.J. Koch var. lacostrum J.G. Costa in 1946 and Vicia sativa L. subsp. devia J.G. Costa and Vicia atlantica J.G. Costa (=V. costae A. Hansen) in 1948. The same year J.G. Costa left Madeira to Mozambique, which is probably the reason why the description of the perennial Sonchus of Porto Santo was never published.

J. G. Costa was the first author to refer a perennial Sonchus for Porto Santo Island. In fact, LOWE (1868) and MENEZES (1914) only cited for Porto Santo S. oleraceus L.

PICKERING (1962) published a check-list of the flowering plants and ferns of the Island of Porto Santo and referred that the name "Sonchus parathalassa" without description in Costa's list should be disregarded. Curiously, C.H. Pickering referred to the finding of an endemic Sonchus sp., from the Ilhéu das Cenouras, another Porto Santo islet, that "await determination". However, this supposed new species of Sonchus was, also, never published.

HANSEN (1969) cited for Porto Santo only Sonchus fruticosus (as S. squarrosus DC.), whereas BOULOS (1974) referred solely to Sonchus ustulatus, based on the specimens collected by C.H. Pickering in 1961, on Ilhéu das Cenouras, deposited at Kew. ERIKSSON et al. (1974) cited Sonchus ustulatus and S. fruticosus for Porto Santo Island. Latter ALDRIDGE (1976) included Porto Santo on the distribution of Sonchus ustulatus subsp. maderensis.

HANSEN & Sunding(1979, 1985, 1993) referred S. fruticosus and S. ustulatus subsp. maderensis for Porto Santo synonymizing "Sonchus parathalassicus Costa" as Sonchus ustulatus. VIEIRA (1992) cited the same taxa for Porto Santo but synonymized "Sonchus parathalassicus Costa" under S. ustulatus subsp. ustulatus (that he did not mention for Porto Santo). PRESS (1994) also assigned the same two taxa to Porto Santo, not referring the name proposed by J. G. Costa.

FONTINHA & JARDIM (1999) confirmed the observations by PICKERING (1962) about the occurrence of a perennial branched Sonchus on Ilhéu das Cenouras, different from those cited for Madeira Archipelago. JARDIM & MENEZES DE SEQUEIRA (2008) considered questionable the existence of S. fruticosus in Porto Santo.

Field observations in Porto Santo Island and islets, Madeira and Desertas and the examination of collected material as well as herbarium specimens (MADJ, MADM, MADS, K and BM) allowed the recognition of a new species of Sonchus subgen. Dendrosonchus endemic to Porto Santo distinct from S. ustulatus, S. fruticosus and S. pinnatus. The putative Sonchus ustulatus subsp. maderensis and S. fruticosus from Porto Santo correspond to this new species. The specimens collected by J.G. Costa on Ilhéu de Baixo and by C. Pickering on Ilhéu das Cenouras belong to the same new taxon. Since J.G. Costa was the first author to observe this new Dendrosonchus species and due to the fact that he named it, although without a description, the validation of the name and the description of this new species from Porto Santo is proposed here as:

Sonchus parathalassius J.G. Costa ex R. Jardim & M. Seq., sp. nov.

= Sonchus ustulatus sensu auct. fl. Portus Sancti.

Nanophanerophyto ad usque 90 cm alto a Soncho ustulato affinis sed differt caule lignoso robusto superne valde ramoso foliis ad apicem caule rosulato; inflorescentia erecta ad usque 60 cm alta ultima tertiam irregulater ramificans, capitulis plusquam sexaginta; foliis pennatipartitis anguste triangularis longe acuminatis lobis lateralibus 5-9, lobo terminali deltoidis longe acuminatis vel acuminati-caudatis30-82 mm longo.

Description: Suffruticose perennial to perennial shrubby plant (Figure 1A), up to 90cm. STEM thick, branched, woody, up to 4 cm diameter. LEAVES (Figure 1B) 28-35 x 8-14cm, fleshy, glabrous, sessile with a persistent sheathing base, disposed in rosettes at the tips of the stems, elliptic-lanceolate to oblong-lanceolate, pinnatipartite, attenuate to the base, midrib 5-8 mm attenuate to the apex; lobes 5-9 pairs, ± opposite to alternate, 3.5-5.1 x 2.1-3.5cm, narrowly triangular, long acuminate, entire to scarcely irregularly dentate; terminal lobe triangular, acuminate to acuminate-caudate, 3-8 cm, larger than the upper pair of lateral lobes; interlobular space round; caulinar leaves smaller and less divided. INFLORESCENCE (Figure 1C) a terminal, upright, branched corymbose cyme, main axis up to 60cm, branching usually at the terminal 1/3, 2-3 branched, last order branches with up to 2-4 pedunculate capitula; peduncles green becoming purplish and broader towards the obconic apex; inflorescence bracts triangular, long acuminate, small, 1.6-5.2 mm; CAPITULA (Figure 1D) numerous, 60-90; ovoid-conical, up to 18 x 15 mm; involucral bracts purplish to yellow-greenish with yellow-greenish apex; outer bracts ca. 9, 1.1-2.7 x 1.5-2.0 mm, small, triangular, base thick, adpressed, purplish with yellow-greenish margins, slightly scarious, apex ciliate; intermediate bracts ca. 6, 5.3-7.6 x 1.3-1.9 mm, oblong, apex yellow-greenish, ciliate, slightly retroflexed;  inner bracts ca. 20, 10.2-12.7 x 1.1-1.8 mm, linear-oblong, purplish-yellow to yellow, apex retroflexed and ciliate. FLORETS 12.6-15.3 mm; ligules 7.0-9.2 x 1.5-2.3 mm, narrow-oblong, yellow; corolla-tube 4.4-5.0 mm, white, pubescent. CYPSELA 2.8-2.9 x 0.8-1 mm, oblong-elliptical, compressed brown. PAPPUS white; bristles 7.7-8.5 mm, scabrid; flexuous hairs 5.0-5.3 mm, less scabrid, fasciculate.

Figure 1 – Sonchus parathalassius. A, Habit. Ilhéu da Cal, 14-IV-2004; B, Leaf rosette, Porto Santo, Pico Castelo, 20-V-2011; C, Inflorescence, Porto Santo, Pico Castelo, 10-VII-2011; D, Capitula, Porto Santo, Pico Castelo, 10-VII-2011; all photos R.Jardim

Figure 2 – Sonchus parathalassius J.G. Costa ex R.Jardim & M.Seq., holotype. MADM

Other specimens: PORTUGAL, MADEIRA, Porto Santo: Rocha das Cenouras, on steep volcanic rock facing south, 100 ft, 20-IV-1961, C. Pickering 324, K; Ilhéu das Cenouras, 9-V-1979, R. Santos, MADJ 5987; Ilhéu da Cal, vertente E no topo N, 14-IV-2004, R. Jardim, MADJ 11014; Miradouro no Pico Castelo. 6-XII-2008, M. Sequeira, 5701, UMad; Pico do Concelho, vertente N, alt.270m, 18-IV-2011, R. Jardim, 1091, UMad; Pico Castelo, vertente NW, alt. 240m, 10-VII-2011, R. Jardim 1215, MA 844022 (UMad); Pico Branco, Lombo dos Amarelos, vertente NE, alt. 150m, 13-VII-2011, R. Jardim 1241, UMad.

Etymology: The specific epithet "parathalassius" derives from the Greek Para near and Thalassa sea, presumably used by J.G. Costa as a reference to the habitat in sea cliffs. The name Sonchus parathalassius is given by J.G. Costa in the specimen here elected as holotype, although the name invalidly published (COSTA, 1946) as "S. parathalassia", does not agree with the gender of the genus.

Distribution: Sonchus parathalassius is endemic from Porto Santo, occurring on the main island, in Pico Castelo, Pico Branco, Pico Concelho and also on the surrounding islets, namely in Ilhéu da Cal (or Ilhéu de Baixo), Ilhéu das Cenouras, Ilhéu de Cima (or Ilhéu do Farol), Ilhéu de Fora and Ilhéu da Fonte da Areia.

Habitat: Chasmo-comophyte in rocky slopes, usually, on north exposed sea cliffs, in the islets up to 100m (Figure 3), inland in Porto Santo Island, up to 320m.

Figure 3 – Sonchus parathalassius, habitat. Ilhéu de Cima, 14-IV-2004, photo: R. Jardim

Phenology: Flowers from April to July.

Conservation status: This new species should be considered as Critically Endangered (CR, C2a(i)), due to the scarce number of populations, reduced occupancy and occurrence area as defined by IUCN (2001), and heavy grazing by rabbits.

Taxonomic remarks: Sonchus parathalassius closely resembles S. ustulatus s.s. but differs by the shrubby habit up to 90 cm, penatipartite leaves with almost entire lobes, long acuminated terminal lobe and inflorescence characters (insertion, branching, number of capitula). The shrubby habit mainly observed in the islets could be related with older plants less grazed by rabbits. Heavy grazing by goats in Porto Santo Island until recently (1995) added to rabbit herbivory, could explain the very late discovery of this species. Table 1 summarizes the diagnostic characters of Sonchus parathalassius and compares them with the other Madeiran Dendrosonchus.

Table 1 – Diagnostic and comparative characters os Sonchus parathalassius

Nomenclature: The revision of the herbarium specimens and of nomenclatural aspects of the Madeiran Dendrosonchus taxa, further led to propose the recognition of former Sonchus ustulatus var. latifolia Lowe at a specific rank and the recognition of Sonchus ustulatus var. imbricatus Lowe at a subspecific level. 

1. Sonchus latifolius (Lowe) R. Jardim & M. Seq., comb. nov.

≡ Sonchus ustulatus Lowe subsp. maderensis Aldridge in Bot. Macaronés., 2: 91 (1977) [1976 publ. 1977], pro parte.

2. Sonchus ustulatus Lowe subsp. imbricatus (Lowe) R. Jardim & M. Seq., comb. nov.

≡ Sonchus ustulatus Lowe var. imbricata Lowe, Man. Fl. Mad., 1(5): 548 (1868). [bas.]

= Sonchus ustulatus Lowe subsp. maderensis Aldridge in Bot. Macaronés., 2: 91 (1977) [1976 publ. 1977], pro parte.

Key to the Sonchus subgen. Dendrosonchus species in Madeira Archipelago:

1. Leaves petiolate ............... S. pinnatus

2. Caulirosulate shrub up to 4 m high; inflorescence with large leafy bracts and capitula up to 30 x 15 mm: ....S. fruticosus

- Suffruticose or caulirosulate shrub up to 90 cm high; inflorescence with very small bracts and capitula up to up to 18 x 15 mm ............................................3

3. Suffruticose to caulirosulate shrub up to 90 cm high; capitula numerous, more than 60, disposed in a terminal irregularly branched, inflorescence branching from the upper 1/3. ...................................S. parathalassius

- Suffruticose with short woody caudex up to 30 cm high; capitula fewer, up to 30, disposed in a regularly branched (usually dichotomous), inflorescence branching from the lower 1/3 - 1/2. .....4

4. Leaf-lobes linear-lanceolate, more than 2x as long as wide, toothed; bracts without appendices..............S. ustulatus

- Leaf-lobes ovate, rarely rhombic, not more than 2x as long as wide, subentire; bracts with conspicuous appendices. ......................... S. latifolius

Concluding remarks: LEE et al. (2005) molecular studies indicate that Madeiran Dendrosonchus species derive from a Tenerife ancestor. Moreover the coastal S. ustulatus and S. latifolia (as S. ustulatus subsp. maderensis) were the basal taxa from which a radiation process initiated to other ecologies. However, the recognition of S. parathalassius as Porto Santo endemic and the fact that this island is older than Madeira (14 My vs. 5.6 My) suggests a possible basal position of this endemism in the Madeiran Dendrosonchus taxa. Therefore, possibly Sonchus parathalassius derived from the Canarian ancestor, dispersed to Madeira Island and rapidly radiated in the other Madeiran Dendrosonchus species, in accordance with the proposed patterns by LEE et al. (2005). In fact, S. parathalassius has characters similar to S. ustulatus (e.g. leaves), S. pinnatus (e.g. inflorescence ramification) and to S. fruticosus (e.g. habit). Further studies, namely molecular, should contribute to clarify the phylogenetic position of Sonchus parathalassius in subgen. Dendrosonchus.

References

ALDRIDGE, A., 1976. Macaronesian Sonchus subgenus Dendrosonchus s.l. (Compositae-Lactuceae), including a reappraisal of the species concept and new combinations. Botanica Macaronesica 2: 81–93.         [ Links ]

BOULOS, L., 1972. Révision systématique du genre Sonchus L. s.l. I. Introduction et classification. Botaniska Notiser 125: 287–305.         [ Links ]

BOULOS, L., 1974. Révision systématique du genre Sonchus L. s.l. V. Sousgenre 2. Dendrosonchus. Botaniska Notiser 127: 7–37.         [ Links ]

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HANSEN, A., 1969. Checklist of the Vascular Plants of the Archipelago of Madeira. Boletim do Museu Municipal do Funchal 24: 1-62.         [ Links ]

HANSEN, A., SUNDING, P. IN ERIKSSON, O., HANSEN, A., SUNDING, P., 1979. Flora Macaronesia. Checklist of vascular plants. Part II: Synonym index. 2. Revised Edition. Oslo, ed. 2, 1: 92        [ Links ]

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IUCN, 2001. IUCN Red List categories and Criteria, version 3.1. IUCN Species Survival Commission. IUCN, Gland, Switzerland and Cambridge. United Kingdom.         [ Links ]

JARDIM, R. & MENEZES DE SEQUEIRA, M., 2008. The vascular plants (Pteridophyta and Spermatophyta) of the Madeira and Selvagens archipelagos. In: BORGES, P., ABREU, C., AGUIAR, A., CARVALHO, P., JARDIM, R., MELO, I., OLIVEIRA, P., SÉRGIO, C., SERRANO, A. & VIEIRA, P. (eds.). A list of the terrestrial fungi, flora and fauna of Madeira and Selvagens archipelagos. pp.157-207, Direcção Regional do Ambiente da Madeira and Universidade dos Açores, Funchal and Angra do Heroísmo.         [ Links ]

LEE, C., KIM, S-C., LUNDY, K., SANTOS-GUERRA, A., 2005. Chloroplast DNA phylogeny of the woody Sonchus alliance (Asteraceae: Sonchinae) in the Macaronesian Islands. American Journal of Botany 92(12): 2072–2085.         [ Links ]

LOWE, R.T., 1868. A Manual Flora of Madeira and the Adjacent Islands of Porto Santo and the Desertas. Vol. 1(5): 545-552. London, John van Voorst.         [ Links ]

MENEZES, C.A., 1914. Flora do Archipelago da Madeira (Phanerogamicas e Cryptogamicas Vasculares). Funchal. Typ. Bazar do Povo.         [ Links ]

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PRESS, J.R., 1994. Sonchus L. In: Press, J.R. & Short, M.J. (eds.) Flora of Madeira pp.184-189. HMSO. London.         [ Links ]

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Acknowledgments

The authors acknowledge J. Capelo for the Latin translation of the diagnosis and A. Pupo and Z. Ferreira for revising the English revision. The study of K and BM specimens (by M. Sequeira) was supported by SYNTHESIS GB-TAF-1053, we are also grateful to the herbarium curators of both herbaria and to the M. Carine (NHM).