Three-leafed chaff flower  (Alternanthera filifolia)

Classified as Least Concern (LC) on the IUCN Red List (1). Subspecies: Alternanthera filifolia filifolia is listed as Least Concern (LC) and A. f. glauca, A. f. glaucescens, A. f. microcephala, A. f. nudicaulis A. f. pintensis and A. f. rabidensis are all listed as Vulnerable (VU) on the IUCN Red List (1).

In common with many other Galapagos endemics, Alternanthera filifolia is a highly variable species, with up to seven recognised subspecies, most of which are unique to one island. It is a small shrub with slender stems, linear to oblong-shaped leaves, and white to greenish-white flowers borne in spikes (2) (3). The subspecies differ mainly in the shape of the flowers, the shape and fleshiness of the leaves, and extent to which the stems and leaves are glaucous (3) (4).

Although Alternanthera filifolia occurs over a large part of the Galapagos archipelago, with the exception of A. f. filifolia, which occurs on at least nine separate islands, most of the subspecies are restricted to one or two islands (2) (3).

Found in the arid lowlands, a dry zone not far from the coast, mainly occupied by cacti and a variable mix of low trees and shrubs (3).

There is very little information on the biology of Alternanthera filifolia, but some hybridisation is likely to take place between subspecies, while birds probably play an important role in seed dispersal, and perhaps even in pollination (4).

Owing to their highly restricted range, it is no surprise that all the subspecies of Alternanthera filifolia, with the exception of the uniquely widespread subspecies A. f. filifolia, are classified as Vulnerable on the IUCN Red List (1). Like much of the Galapagos flora, these plants are threatened by a combination of habitat loss, competition with invasive alien plants, and over-browsing by introduced herbivores such as feral goats and donkeys (5).

There are no known conservation measures in place for Alternanthera filifolia, but botanical research carried out by the Charles Darwin Research Station is focused on the conservation of the Galapagos’ native and endemic flora (5). As introduced species probably pose the greatest risk to the archipelago’s terrestrial biodiversity, actions are already being taken to eradicate the most invasive and destructive animals and plants (5) (6).

For further information on the conservation of the endemic flora of the Galapagos see:

• The Charles Darwin Foundation:
  www.darwinfoundation.org
• Galapagos Conservation Trust:
  www.gct.org