Species complexes in the sea: model systems for studying the biodiversity and evolutionary history of the Indo-West Pacific reef biota

University Of Florida, Gainesville FL

Investigators

Abstract

Coral reefs are arguably the most diverse and vulnerable coastal ecosystems and are currently undergoing unprecedented decline. Both their diversity and vulnerability are influenced by genetic structuring, the spatio-temporal scale and pattern of geographic differentiation within and among species. By documenting such structuring, we gain a better understanding of the origin and distribution of reef biodiversity. Furthermore, data on the level and scale of genetic interconnections are crucial for predicting reef response in the face of stressors and for the design of appropriate conservation strategies. On the basis of morphological species ranges, previous workers have generally characterized reef organisms as widespread, especially in the Indo-West Pacific (IWP), the largest and most diverse marine region. Wide species ranges in the IWP imply dispersal across numerous, vast, open ocean barriers, supporting the belief that reef organisms have tremendous dispersal abilities. Past molecular studies found IWP populations to be typically interconnected over basinal to sub-basinal scales. However recent studies on stomatopods in Indonesia and supratidal crustaceans in the Americas encountered finer levels of genetic differentiation. These studies raise the question: is fine-scale genetic structuring common among reef organisms? Preliminary data show fine-scale genetic differentiation in several widespread, reef- associated gastropods. Each species is composed of numerous, divergent populations with ranges limited to archipelagoes or islands. Their life history attributes are typical of many reef organisms, and initial data show considerable structuring in co-occurring taxa with different life history strategies. The goals of this project are to document the extent of geographic, genetic structuring in selected reef-associated gastropods in the IWP, and to use these patterns to address questions about large-scale, spatio-temporal processes in the marine biosphere. Evolutionarily significant units (ESUs), the relevant conservation and evolutionary units, will be identified throughout the region. Hypotheses about the source and dynamics of ESUs, and thus patterns of distribution and diversification, will be tested using sequence data. The significance of the proposed work lies in the nature of fine scale genetic structuring encountered in these taxa, which makes them model systems for studies of marine speciation and biogeography, and has major implications for reef management and conservation of biodiversity. Fine-scale, but deeply divergent genetic structuring has rarely been encountered in marine taxa and only in continental settings; its occurrence on islands is unprecedented and contrary to expectations. How can organisms capable of dispersing far into Oceania differentiate on an archipelagic scale? This conundrum implies that rare dispersal events may be highly important in the spread as well as differentiation of marine populations. Exploring the phylogenetic nature of genetic structuring in independent gene trees will shed light on a variety of hypotheses about the origin of marine biodiversity and distribution of reef organisms. High levels of genetic differentiation also imply that conservation and resource management strategies on reefs need to be appropriately scaled. Understanding the size and distribution of genetically interconnected units is crucial for designing appropriate management units, such as marine protected areas. Congruent genetic structuring delineates intrinsic breaks in the distribution of reef biota and thus identifies natural management units. This project will lead to better management strategies for reef-associated marine resources, and will also have direct educational impact at several levels. The project team will be interacting with resource managers regularly. The species studied are important food organisms, and provide an excellent venue to introduce implications for resource management and thus influence reef management strategies on numerous Pacific islands. The results of this work will be disseminated regionally as well as in the scientific literature.