&lt;b&gt;Conservation status of Mascarene Amaranth &lt;I&gt;Aerva congesta&lt;/I&gt; Balf.F. Ex Baker (Eudicots: Caryophyllales: Amaranthaceae): a Critically Endangered endemic herb of the Mascarenes, Indian Ocean&lt;/b&gt;

Kersley Bruno Pynee,Poojanraj Khurun,David Harold Lorence

doi:10.11609/jott.2402.10.8.12056-12063

Abstract

Aerva congesta Balf.f. ex Baker (Amaranthaceae), an endemic of Mascarene Islands (Mauritius and Rodrigues) is assessed for its conservation status. Considering its local extinction in Rodrigues and very small population in Mauritius, in Round Island and at Gris Gris, south of Mauritius its area of occupancy (AOO) is estimated at 8km². Due to its small AOO and threats by increasing native vegetation and alien species, A. congesta is evaluated as Critically Endangered following the latest IUCN Red List criteria. The species needs an urgent well-defined restoration program and ecological studies to prevent its extinction.

Highlights

The genus Aerva Forssk. (Amaranthaceae) consists of 21 species (The Plant List 2013) distributed mostly in the arid or semi-arid regions of the world. Bojer (1837) noted three species of Aerva on Mauritius, A. lanata (L.) Juss., A. caudata Bojer, and A. chenopodifolia Bojer ( Nothosaerva brachiata (L.) Wight), which are considered as native
Through closer study and comparison with herbarium specimens and using the ‘Flore des Mascareignes’ at The Mauritius Herbarium (MAU), the sample collected was identified as Aerva congesta Balf.f. ex Baker
At Gris Gris, the species shows a similar ecology; it is found rooted in rock crevices of exposed cliffs in association with the native grasses and sedges, including (Zoysia matrella (L.) Menill, Stenotaphrum dimidiatum (L.) Brongn. and Fimbristylis cymosa R.Br.), as well as other native species

Summary

Introduction

The genus Aerva Forssk. (Amaranthaceae) consists of 21 species (The Plant List 2013) distributed mostly in the arid or semi-arid regions of the world. Bojer (1837) noted three species of Aerva on Mauritius, A. lanata (L.) Juss., A. caudata Bojer (nomen nudum), and A. chenopodifolia Bojer ( Nothosaerva brachiata (L.) Wight), which are considered as native. Baker (1877) described three species of Aerva on Mauritius, two perennials, A. lanata and A. congesta Balf. Townsend (1994) listed three species, the Mascarene endemic A. congesta, and two alien species formerly known only from cultivation, A. lanata and A. sanguinolenta (L.) Blume. Referring to Townsend (1994) and Sukhorukov (2013), Aerva congesta is one of the two known endemic species of the Amaranthaceae in the Mascarene Islands (South West Indian Ocean) (Image 1). It is known from both Mauritius (Image 2) and Rodrigues (Image 3), but is not recorded on Réunion Island. On Mauritius, Strahm (1989) quoted that there were recent collections from one locality on mainland Mauritius, but only samples from Round Island, an outer islet northern of Mauritius (Image 2), were accessed at The Mauritius Herbarium

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Conclusion