The phytogeographical affinities of the Pitcairn Islands – a model for south‐eastern Polynesia?

Abstract

Aim To identify how the Pitcairn group relates biogeographically to the south‐eastern Polynesian region and if, as a subset of the regions flora, it can then be used as a model for biogeographical analyses. Location The Pitcairn group (25°4′ S, 130°06′ W) comprises four islands: Pitcairn, a relatively young, high volcanic Island; Henderson, an uplifted atoll, the uplift caused by the eruption of Pitcairn; and two atolls, Ducie and Oeno. The remote location, young age and range of island types found in the Pitcairn Island group makes the group ideal for the study of island biogeography and evolution. Methods A detailed literature survey was carried out and several data sets were compiled. Dispersal method, propagule number and range data were collected for each of the 114 species that occurs in the Pitcairn group, and environmental data was also gathered for islands in Polynesia. Analyses were carried out using non‐metric multidimensional scaling and clustering techniques. Results The flora of the Pitcairn Islands is derived from the flora of other island groups in the south‐eastern Polynesian region, notably those of the Austral, Society and Cook Islands. Species with a Pacific‐wide distribution dominate the overall Pitcairn group flora. However, each of the islands show different patterns; Pitcairn is dominated by species with Pacific, Polynesian and endemic distributions, with anemochory as the dominant dispersal method (39.5%); Henderson is also dominated by species with Pacific, Polynesian and endemic distributions, but zoochory is the dominant dispersal method (59.4); Oeno and Ducie are dominated by Pantropic species with hydrochory as the most common dispersal method (52.9% and 100%, respectively). Main conclusions • Habitat availability is the most significant factor determining the composition and size of the flora. • South‐east Polynesia is a valid biogeographical unit, and should include the Cook, Austral, Society, Marquesas, Gambier, Tuamotu and Pitcairn Islands with Rapa, but should exclude Easter Island, Tonga and Samoa. • Regionalization schemes should take island type into consideration. • The Pitcairn Island group can serve as a useful model for Pacific biogeographical analyses.

Grasses (Poaceae) of Easter Island — Native and Introduced Species Diversity

“…The floristic affinity between these islands was compared by cluster analysis of presence-absence data for 349 species, using Jaccard coefficient as the similarity measure, UPGMA algorithm and the statistical software Infostat [23]. Species composition was taken from the literature [24][25][26][27][28]. Species accumulation curve and estimated richness was calculated using the software Estimates 8.0 [29].…”

The world's biogeographical regions: cluster analyses based on bat distributions

“…Conran, 1995); however, Bray–Curtis dissimilarity (in its presence/absence form identical with Sørensen, also used in e.g. Kingston et al. , 2003), while differing in actual dissimilarity values, results in the same clusters, and allows for species numbers to be further used untransformed.…”

“…Williams et al. , 1999; Qian, 2001; Kingston et al. , 2003), especially following the realization that biogeographical units are hierarchically arranged (McLaughlin, 1992).…”

What biogeography is: a place for process

“…So, to understand Hawaiian biogeography, we need to look at the processes that resulted in the accumulation of biotas on these islands over several millions of years as the various contributors to Wagner & Funk's (1995) book do, so elegantly (and see McDowall, 2003). Much the same seems to be true of the Pitcairn group of islands (Kingston et al. , 2003), which also comprises a series of relatively young islands that are not considered ever to have had any land connections.…”