Species-volume relationships in tropical rainforests

Island biogeography theory relates species richness to habitat area. This paper suggests that using two-dimensional area measurements in three-dimensionally complex ecosystems does not give reliable estimates of species richness or diversity, and that volume measurements should be used, especially when studying organisms that have fine-grained niche requirements such as arthropods. This paper examines three-dimensional spatial patterns of Coleoptera in primary rainforest in Sulawesi (Indonesia) and demonstrates how adding extra levels in a sampling area (i.e. volume) significantly increases the measure of species richness. A linear relationship exists that shows a 50% increase in species richness for every 10 m added to a vertical transect. A review of the literature is made in light of these observations. Implications regarding the measurement of species richness in complex ecosystems are discussed and possible repercussions on the estimation of species extinction following habitat disturbance.