A geological perspective of the upland biota of Laysan atoll (Hawaiian Islands)

Abstract

Laysan Island, a low atoll in the Leeward Hawaiian Islands, exhibits a biota that contains nine genera of upland and montane lineages of animals and plants usually of restricted range and occurrence and adapted t o high island habitats. The geological history of Laysan Island, interpreted in terms of plate tectonic theory and recent ideas on the formation of linear island chains, shows that Laysan existed as an active high volcanic island approximately 15 million years ago. Since that time subaerial erosion and tectonic subsidence have combined to reduce the height of the island. During the past 2 5 0 , 0 0 0 years glacio-eustatic sea level changes have resulted in Laysan Island fluctuating, geomorphologically, between a high limestone island and an atoll status. Laysan is viewed as a refugium for upland and montane lineages able to keep pace, via great adaptive flexibility, with drastic habitat changes. The thesis that plants of Laysan are recent arrivals is considered unlikely, as regards the upland contingent, in view of the geological history of the island.

Atolls of the World: Revisiting the Original Checklist

“…In Hawaii, Laysan (327) is elevated 12 m due to glacioeustatic sea level changes (Schlanger and Gillett, 1976); it is now a hypersaline lagoon (Table B. 1;Caspers 1981;Athens et al 2007). Lisiansky lacks a lagoon.…”

Introduction and Summary of Results from DSDP Leg 55, the Hawaiian-Emperor Hot-Spot Experiment

“…The drilling into shallow-water carbonate debris was also expected to provide information on the vertical motion of the Pacific plate (Ladd et al, 1970). Previous experience in atoll drilling established without doubt that atolls in the open sea serve as measuring rods for both local and regional changes in the height of sea level relative to seamounts (Ladd et al, 1970;Schlanger and Gillett, 1976). Darwinian subsidence has been qualitatively proven by atoll drilling, although the morphological development of subsiding reefs appears more complex than originally envisioned (Purdy, 1974).…”

Biogeography and ecology of atoll plants

“…Recent research and theoretical developments may call this generalization into question, however. In a study of Laysan, Schlanger and Gillett (1976) found nine genera of upland or montane forms. They point out that Laysan has in the past been both a high island and a low atoll as processes of subaerial erosion and tectonic subsidence reduced the elevation.…”