High Connectivity of Animal Populations in Deep-Sea Hydrothermal Vent Fields in the Central Indian Ridge Relevant to Its Geological Setting

Girish Beedessee,Tomomi Ogura,Satoshi Nakagawa,Daniel E P Marie,Takuya Yahagi,Ken Takai,Hiromi Watanabe,Suguru Nemoto,Meera Koonjul,Kentaro Nakamura,John F Valentine

doi:10.1371/journal.pone.0081570

Abstract

Dispersal ability plays a key role in the maintenance of species in spatially and temporally discrete niches of deep-sea hydrothermal vent environments. On the basis of population genetic analyses in the eastern Pacific vent fields, dispersal of animals in the mid-oceanic ridge systems generally appears to be constrained by geographical barriers such as trenches, transform faults, and microplates. Four hydrothermal vent fields (the Kairei and Edmond fields near the Rodriguez Triple Junction, and the Dodo and Solitaire fields in the Central Indian Ridge) have been discovered in the mid-oceanic ridge system of the Indian Ocean. In the present study, we monitored the dispersal of four representative animals, Austinograea rodriguezensis, Rimicaris kairei, Alviniconcha and the scaly-foot gastropods, among these vent fields by using indirect methods, i.e., phylogenetic and population genetic analyses. For all four investigated species, we estimated potentially high connectivity, i.e., no genetic difference among the populations present in vent fields located several thousands of kilometers apart; however, the direction of migration appeared to differ among the species, probably because of different dispersal strategies. Comparison of the intermediate-spreading Central Indian Ridge with the fast-spreading East Pacific Rise and slow-spreading Mid-Atlantic Ridge revealed the presence of relatively high connectivity in the intermediate- and slow-spreading ridge systems. We propose that geological background, such as spreading rate which determines distance among vent fields, is related to the larval dispersal and population establishment of vent-endemic animal species, and may play an important role in controlling connectivity among populations within a biogeographical province.

Highlights

More than 30 years have passed since the discovery of the first hydrothermal vents on the Galapagos Rift in the eastern Pacific Ocean [1]
The results of our present study indicate for the first time to examine population differentiation in the four representative species (A. rodriguezensis, R. kairei, Alviniconcha sp. type 3 and scalyfoot gastropod) in the four hydrothermal vent communities (Dodo, Solitaire, Edmond, and Kairei) along the Central Indian Ridge (CIR)
The different number of cohort of the Solitaire population may reflect the difference in the colonization process in the Solitaire field, for example, those resulted from different reproductive period or growth rate

Summary

Introduction

More than 30 years have passed since the discovery of the first hydrothermal vents on the Galapagos Rift in the eastern Pacific Ocean [1]. The vents are usually associated with dense assemblages of organisms, which are patchily distributed on the deep-sea floor [3,4]. These communities are typically separated by tens to hundreds of kilometers along an actively spreading ridge, and by even greater distances between ridge segments. The existence of such communities highlights the significant contribution to geologically produced energy sources to chemosynthetic biomass production, and the remarkable adaptability of life in deep-sea hydrothermal vent ecosystems [5]. Dispersal may allow them to explore new favorable habitat [19]

Objectives

Methods

Results

Conclusion