Assessment of host-associated genetic differentiation among phenotypically divergent populations of a coral-eating gastropod across the Caribbean.

Margaret W. Miller,Ludovic Orlando,Iliana B. Baums,Lyza Johnston

doi:10.1371/journal.pone.0047630

Abstract

Host-associated adaptation is emerging as a potential driver of population differentiation and speciation for marine organisms with major implications for ecosystem structure and function. Coralliophila abbreviata are corallivorous gastropods that live and feed on most of the reef-building corals in the tropical western Atlantic and Caribbean. Populations of C. abbreviata associated with the threatened acroporid corals, Acropora palmata and A. cervicornis, display different behavioral, morphological, demographic, and life-history characteristics than those that inhabit other coral host taxa, indicating that host-specific selective forces may be acting on C. abbreviata. Here, we used newly developed polymorphic microsatellite loci and mitochondrial cytochrome b sequence data to assess the population genetic structure, connectivity, and demographic history of C. abbreviata populations from three coral host taxa (A. palmata, Montastraea spp., Mycetophyllia spp.) and six geographic locations across the Caribbean. Analysis of molecular variance provided some evidence of weak and possibly geographically variable host-associated differentiation but no evidence of differentiation among sampling locations or major oceanographic regions, suggesting high gene flow across the Caribbean. Phylogenetic network and Bayesian clustering analyses supported a hypothesis of a single panmictic population as individuals failed to cluster by host or sampling location. Demographic analyses consistently supported a scenario of population expansion during the Pleistocene, a time of major carbonate reef development in the region. Although further study is needed to fully elucidate the interactive effects of host-associated selection and high gene flow in this system, our results have implications for local and regional community interactions and impact of predation on declining coral populations.

Highlights

Coral reefs are among the most biologically diverse ecosystems on the planet, the magnitude of this diversity and the mechanisms that drive and maintain it are still poorly understood [1]–[3]
pelagic larval duration (PLD) has been decoupled from dispersal distance and gene flow in several Caribbean reef fishes [33], [54] and invertebrates [55], long distance dispersal and FL Acropora palmata (ACR) FL Montastraea spp. (MON) BAH ACR NAV ACR NAV MON SVG ACR SVG MON CUR ACR CUR MON PAN Mycetophylia spp. (MYC)
We used five highly polymorphic microsatellite loci and 366 bp of the mitochondrial cytochrome b gene to assess the population genetic structure, connectivity, and demographic history of Coralliophila abbreviata sampled from different host coral species and geographic localities

Summary

Introduction

Coral reefs are among the most biologically diverse ecosystems on the planet, the magnitude of this diversity and the mechanisms that drive and maintain it are still poorly understood [1]–[3]. In diverse terrestrial ecosystems, it is estimated that 20%–40% of all animal species are specialist phytophagous insects [4]. Ecological niche partitioning has emerged as a prevalent mode of diversification for these insect herbivores and parasites [5],[6]. This process appears to be a dynamic continuum beginning when a subpopulation occupies a new host or habitat, often in response to some ecological trade-off such as reduced intraspecific competition or enemy free space [7]. Host-associated selection must be strong enough to overcome the potentially homogenizing effect of dispersal and gene flow from the original population [11], [12]

Methods

Results

Discussion

Conclusion