Amaranthus palmeri , a second record for Africa and notes on A

Amaranthus L. (Amaranthaceae Juss.) is a genus of about 70 mostly annual, monoecious and dioecious species with worldwide distribution. Approximately 40 species are native to the Americas and the remaining species are native to the other continents (see e.g. Costea, Sanders & Waines 2001; Iamonico 2015a). Several American species are used as ornamentals, and others are cultivated for grains or as leafy vegetables. In many areas Amaranthus species have escaped cultivation and have become problematic for agricultural systems, causing economic loss and for biodiversity because the species compete with indigenous species for resources such as light and nutrients.


Introduction
Amaranthus L. (Amaranthaceae Juss.) is a genus of about 70 mostly annual, monoecious and dioecious species with worldwide distribution.Approximately 40 species are native to the Americas and the remaining species are native to the other continents (see e.g.Costea, Sanders & Waines 2001;Iamonico 2015a).Several American species are used as ornamentals, and others are cultivated for grains or as leafy vegetables.In many areas Amaranthus species have escaped cultivation and have become problematic for agricultural systems, causing economic loss and for biodiversity because the species compete with indigenous species for resources such as light and nutrients.
Amaranthus is a challenging genus from a taxonomic perspective because of its high phenotypic variability, which has led to nomenclatural disorder and misapplication of names (see e.g.Costea et al. 2001;Iamonico 2015a;Mosyakin & Robertson 1996;Nestor 2015).No comprehensive molecular study has been done yet, and the more recent infrageneric classification was proposed by Mosyakin and Robertson (1996) who recognised three subgenera: subgenus Acnida (L.) Aellen ex K.R. Robertson with three sections, subgenus Albersia (Kunth) Gren.& Godr.with four sections, and subgenus Amaranthus, with three sections and two subsections.
As part of an ongoing study on the genus Amaranthus (see e.g.Iamonico 2014aIamonico , 2014bIamonico , 2015aIamonico , 2015bIamonico , 2016aIamonico , 2016bIamonico , 2016c;;Iamonico & Das 2014) and the Tunisian Amaranthaceae (Sukhorukov et al. 2016), field surveys were carried out and resulted in the identification of a population of A. palmeri and this represents the first record of the species for Tunisia and only the second for Africa.Morphological notes, data on the habitat, as a nomenclatural study of the name Amaranthus palmeri var.glomeratus Uline & W.L. Bray (which appears still untypified) and notes on the name A. palmeri are presented here.

Material and methods
The work is based on field surveys (July 2014-October 2015), analysis of relevant literature and examination of specimens preserved in the following herbaria: GH, FI, HFLA, K, MICH, NEBC, NY, MO, P, RO, US (acronyms according to Thiers 2016+) and the Herbarium of Bizerta University (not listed in Index Herbariorum).
The articles cited through the text refer to the Melbourne Code, ICN (McNeill et al. 2012).

Results and discussion
Typification of Amaranthus palmeri var.glomeratus Uline and Bray (1894:272) described the var.glomeratus on the basis of specimens collected by E. Palmer in the Sonoran Desert in 1889, as reported in the protologue.According to the protologue, differential features are the habit (ascending), the plant height (shorter than the typical form) and the synflorescence structure [cymes aggregated in dense glomerules (3-5 cm in diameter) at the base of the plant].
Concerning the identity of the var.glomeratus, it cannot be associated with A. palmeri in our opinion.Unfortunately citations of this taxon are rare in the literature.No citation was found for Australia, Asia, Europe and Africa (see e.g.Bojian, Clemants & Borsch 2003;Iamonico 2015b;Palmer 2009;SANBI 2012).Even the Flora of North America (Mosyakin & Robertson 2003) does not report this taxon.Shreve and Wiggins (1964:457-458) and Abrams (1994:99) listed the var.glomeratus as heterotypic synonym of A. palmeri.However, only the description reported in the Vegetation and Flora of the Sonoran Desert (Shreve & Wiggins 1964) corresponds to the original concept by Uline and Bray (1894), while that by Abrams (1994) completely refers to the typical form.Furthermore, the taxon glomeratus appears to occur only in the Sonoran Desert, a unique area of the world which includes part of the United States (Arizona, California) and Mexico (Baja California, Sonora, Sinaloa), and which is characterised by high levels of species richness and endemism (see e.g.Shreve & Wiggins 1964).

Note of the typification of Amaranthus palmeri
Phenology: Flowering time July-August, fruiting time September-October.
Habitat: Ruderal on roadsides and public gardens.
Distribution: 18-20 individuals were found all referring to a single scattered population, which occupies an area of about 3-4 ha.
Alien status: Neophyte species native to North America and which is considered casual in Tunisia according to Pyšek et al. (2002).Despite this, monitoring is necessary to verify a possible naturalisation and spreading of A. palmeri in Tunisia and, if this is found to be the case, actions for eradication of the plants will be required.

Etymology:
The specific epithet refers to the Sonoran Desert.