Habitat Availability and Heterogeneity and the Indo-Pacific Warm Pool as Predictors of Marine Species Richness in the Tropical Indo-Pacific

Jonnell C Sanciangco,Peter J Etnoyer,Fabio Moretzsohn,Kent E Carpenter,Diego Fontaneto

doi:10.1371/journal.pone.0056245

Abstract

Range overlap patterns were observed in a dataset of 10,446 expert-derived marine species distribution maps, including 8,295 coastal fishes, 1,212 invertebrates (crustaceans and molluscs), 820 reef-building corals, 50 seagrasses, and 69 mangroves. Distributions of tropical Indo-Pacific shore fishes revealed a concentration of species richness in the northern apex and central region of the Coral Triangle epicenter of marine biodiversity. This pattern was supported by distributions of invertebrates and habitat-forming primary producers. Habitat availability, heterogeneity, and sea surface temperatures were highly correlated with species richness across spatial grains ranging from 23,000 to 5,100,000 km2 with and without correction for autocorrelation. The consistent retention of habitat variables in our predictive models supports the area of refuge hypothesis which posits reduced extinction rates in the Coral Triangle. This does not preclude support for a center of origin hypothesis that suggests increased speciation in the region may contribute to species richness. In addition, consistent retention of sea surface temperatures in models suggests that available kinetic energy may also be an important factor in shaping patterns of marine species richness. Kinetic energy may hasten rates of both extinction and speciation. The position of the Indo-Pacific Warm Pool to the east of the Coral Triangle in central Oceania and a pattern of increasing species richness from this region into the central and northern parts of the Coral Triangle suggests peripheral speciation with enhanced survival in the cooler parts of the Coral Triangle that also have highly concentrated available habitat. These results indicate that conservation of habitat availability and heterogeneity is important to reduce extinction of marine species and that changes in sea surface temperatures may influence the evolutionary potential of the region.

Highlights

Persistent questions remain regarding the origins of the uneven distribution of marine species richness across the tropical IndoPacific [1], despite numerous relevant ecological and biogeographical studies and an urgent need to improve conservation effort [2]
The highest 30% of species richness radiated from this epicenter north to southern Japan, south to south-central Indonesia and the northeast tip of Australia, west to southern Sumatra and east to the easternmost Solomon Islands and species richness continued to diminish with distance from this epicenter (Figure 1A, 1B)
The highest concentration of species richness within the Coral Triangle, i.e., in the Philippines and eastern Indonesia, was similar to what has been proposed by Veron et al (2009) [3] based on corals

Summary

Introduction

Persistent questions remain regarding the origins of the uneven distribution of marine species richness across the tropical IndoPacific [1], despite numerous relevant ecological and biogeographical studies and an urgent need to improve conservation effort [2]. Explanations for the Coral Triangle epicenter of marine biodiversity [3] have received more attention in the literature than any other topic in marine biogeography [4]. This area encompasses much of Indonesia, Malaysia, the Philippines, Papua New Guinea, the Solomon Islands, Timor L’Este, and Brunei. It is referred to as the East Indies Triangle [5,6,7], the Indo-Malay-Philippine Archipelago [8,9], and a variety of other names [1]. The term Indo-Australian Archipelago (e.g. [10,11]) is used frequently, though the Coral Triangle does not include Australia [3] and does include geological elements beyond Indonesia [12].

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Conclusion