Diagnostics, taxonomy, nomenclature and distribution of perennial Sesuvium (Aizoaceae) in Africa

Alexander P Sukhorukov; Maya V Nilova; Andrey S Erst; Maria Kushunina; Cláudia Baider; Filip Verloove; Marcos Salas-Pascual; Irina V Belyaeva; Anastasiya A Krinitsina; Peter V Bruyns; Cornelia Klak

doi:10.3897/phytokeys.92.22205

Diagnostics, taxonomy, nomenclature and distribution of perennial Sesuvium (Aizoaceae) in Africa

PhytoKeys. 2018 Jan 15:(92):45-88. doi: 10.3897/phytokeys.92.22205. eCollection 2018.

Authors

Affiliations

¹ Department of Higher Plants, Biological Faculty, Lomonosov Moscow State University, Leninskie gory 1/12, Moscow 119234, Russia.
² Central Siberian Botanical Garden SB RAS, Zolotodolinskaya st. 101, Novosibirsk 630090, Russia.
³ Tomsk State University, Laboratory of Phylogeny and Systematics, Lenin st. 36, Tomsk 634050, Russia.
⁴ Department of Plant Physiology, Biological Faculty, Lomonosov Moscow State University, Leninskie gory 1/12, Moscow 119234, Russia.
⁵ The Mauritius Herbarium, RE Vaughan Building, Agricultural Services, Ministry of Agro-Industry and Food Security, Réduit, 80835, Mauritius.
⁶ Botanic Garden of Meise, Nieuwelaan 38, B-1860 Meise, Belgium.
⁷ Institute for Environmental Studies and Natural Resources (i-UNAT), University of Las Palmas de Gran Canaria (ULPGC), Las Palmas de Gran Canaria, Gran Canaria, Canary Islands, Spain.
⁸ Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AE, UK.
⁹ Bolus Herbarium, Department of Biological Sciences, University of Cape Town, Rhodes Gift, 7707 South Africa.

Abstract

The taxonomy of perennial Sesuvium species in Africa has been poorly investigated until now. Previously five perennial species of Sesuvium were recognised in Africa (S. congense, S. crithmoides, S. mesembryanthemoides, S. portulacastrum, and S. sesuvioides). Based on the differing number of stamens, S. ayresii is accepted here as being distinct from S. portulacastrum. Field observations in Angola also led the authors to conclude that S. crystallinum and S. mesembryanthemoides are conspecific with S. crithmoides. A new subspecies, Sesuvium portulacastrum subsp. persoonii, is described from West Africa (Cape Verde, Gambia, Guinea-Bissau, Mauritania, Senegal). The molecular phylogeny indicates the position of S. portulacastrum subsp. persoonii within the "American lineage" as a part of the Sesuvium portulacastrum complex which needs further studies. A diagnostic key and taxonomic notes are provided for the six perennial species of Sesuvium found in Africa and recognised by the authors (S. ayresii, S. congense, S. crithmoides, S. portulacastrum subsp. portulacastrum, S. portulacastrum subsp. persoonii, S. verrucosum and the facultatively short-lived S. sesuvioides). The distribution of S. crithmoides, previously considered to be endemic to Angola, is now confirmed for the seashores of Republic of Congo and DR Congo. The American species S. verrucosum is reported for the first time for Africa (the Macaronesian islands: Cape Verde and the Canaries). It is locally naturalised in Gran Canaria, being a potentially invasive species. These findings as well as new records of S. verrucosum from Asia and the Pacific Islands confirm its proneness to transcontinental introduction. Lectotypes of S. brevifolium, S. crithmoides, S. crystallinum and S. mesembryanthemoides are selected. The seed micromorphology and anatomy of the perennial African species is studied. Compared to the seeds of some annual African Sesuvium investigated earlier, those of perennial species are smooth or slightly alveolate. The aril is one-layered and parenchymatous in all species and usually tightly covers the seed. The aril detachments from the seed coat that form a white stripe near the cotyledon area easily distinguish S. verrucosum from other species under study.

Keywords: Africa; Aizoaceae; Sesuvieae; Sesuvioideae; Sesuvium; molecular phylogeny; new subspecies; taxonomy.

Grants and funding

Russian Science Foundation, project 14-50-00029 Scientific programs АААА-А16-116021660045-2 and АААА-А16-116021660105-3 of the Department of Higher Plants, Lomonosov Moscow State University Tomsk State University competitiveness program (8.1.19.2017) COST Action TD 1209 NRF incentive grant (grant no. 103697)