Vegetation status on Nishi-jima Island (Ogasawara) before eradication of alien herbivore mammals: rapid expansion of an invasive alien tree,Casuarina equisetifolia(Casuarinaceae)

Abstract

Insular ecosystems can be dramatically affected by alien species, and records of pre-eradication status are essential to evaluate the effects of eradicating alien species. Nishi-jima Island is a small island of the Ogasawara group on which the first program of complete eradication of alien herbivorous mammals (black rats and feral goats) will be conducted. After eradication, the government plans to conduct ecosystem restoration on the island. This paper reports the angiosperm flora and vegetation of Nishi-jima Island before eradication of the rats and goats, with the objective of aiding ecosystem management after the eradication. Our surveys indicate that vegetation cover by the alien tree, Casuarina equisetifolia has expanded compared with its distribution in a 1974 aerial photograph of the island. The predominant vegetation in 2006 was C. equisetifolia forests and Zoysia tenuifolia grasslands, with fragmented native tree vegetation. The flora of the island comprised 69 angiosperm species (50 indigenous species) of which 30% were endemic, far less than for the Ogasawara Islands as a whole (45%). However, several populations of endangered plants remain. To restore the native ecosystem on Nishi-jima, eradication of C. equisetifolia is important in addition to eradication of alien herbivorous mammals.

Genetic variation of pantropical Terminalia catappa plants with sea‐drifted seeds in the Bonin Islands: suggestions for transplantation guidelines

“…At this time, a considerable amount of the coastal area is inhabited by alien C. equisetifolia (Abe et al . ). T. catappa is one of the most important candidate tree species for the revegetation of coastal areas after the eradication of C. equisetifolia .…”

“…It prefers flat sandy or rocky seashores to coastal cliff and thus the distribution is discontinuous within islands. At this time, a considerable amount of the coastal area is inhabited by alien C. equisetifolia (Abe et al 2011). T. catappa is one of the most important candidate tree species for the revegetation of coastal areas after the eradication of C. equisetifolia.…”

Vegetational changes in the coral-gravelly barrier spit appearing after the 2004 Indian Ocean Tsunami at Pakarang Cape, southwestern Thailand, related to topographical changes

“…These characteristics might be related to the predominant occurrence of C. equisetifolia on the present barrier spit. The rapid development of alien C. equisetifolia and its suppression of other indigenous plants have been reported for many tropical areas (e.g., Abe et al 2011).…”

Peer Review #1 of "Outstanding performance of an invasive alien tree Bischofia javanica relative to native tree species and implications for management of insular primary forests (v0.1)"

“…Additional studies of invasive tree species are needed to understand details of the invasion dynamics and rate of invasion (Martin et al 2009;Richardson and Rejmánek 2011;Richardson et al 2014). The Ogasawara Islands host insular ecosystems with high endemic biodiversity, but several invasive tree species are causing drastic changes to the vegetation (Hata et al 2006;Fukasawa et al 2009;Abe et al 2011). Bischofia javanica (Phyllanthaceae) is naturally distributed from Taiwan to Southeast Asia in the nearby area (e.g., Lin et al, 2017) but is an invasive alien tree species in the Ogasawara islands (Yamashita et al 2000;Shimizu 2003).…”