Coral reef fishes are an astonishingly diverse group of vertebrates. They are rich in number and extraordinarily varied in shape, size, and ecology. This project will investigate how coral reefs have shaped marine fish biodiversity by examining diversification patterns and processes in tetraodontiform fishes (a group including pufferfishes, porcupine fishes, and triggerfishes). The investigators will construct an evolutionary tree for this group by analyzing DNA sequences, key morphological features, and the fossil record. This tree will provide a framework for comparing rates of evolution of fins, body shape, and jaws between reef and non-reef species. The research team will test whether reef species have evolved changes in their feeding and swimming systems more quickly than non-reef species and whether major evolutionary changes correspond with key historical events, such as the closing of sea-ways or periods of rapid climate change.
This work will provide important new insights into how coral reefs, one of the planets most unique habitats, have shaped biodiversity in marine fishes. By revealing how paleoclimatic events have affected historical patterns of species richness, this study will improve the understanding of the impacts of human-caused global changes on reef fish biodiversity. Outreach efforts - including mentoring, seminars, and workshops - will provide training for new scientists from underrepresented groups and advance the use of newly developed analytical methods to the national research community.
The major focus of research under this proposal has been on generating new evolutionary trees for tetraodontiform fishes, a lineage of fishes which includes pufferfishes, porcupine fishes, boxfishes, triggerfishes, filefishes, and the enormous ocean sunfishes. We used these evolutionary trees to test the hypotheses that colonization of certain habitat types such as coral reefs and fresh water has lead to an increase in rates of speciation and morphological evolution. Tetraodontiforms are an especially appropriate group for our research question because they include species found in a diversity of habitats and because they show an enormous diversity of body shapes and sizes. Our research produced new molecular phylogenies for pufferfishes, triggerfishes, filefishes, and a new evolutionary tree showing how the ten families of tetraodontiform are related. We used 3-D laser scanning, 2-D imaging, and more traditional techniques to capture tetraodontiform shape diversity found that colonization of freshwater habitats has not lead to fast rates of diversification in pufferfishes as it has in other fishes, perhaps because these habitats were already occupied by a rich community of freshwater species. Many lineages of coral reef tetraodontiforms show evidence of fast speciation but morphological evolution is slower in some coral reef groups than in open water relatives. Triggerfishes and filefishes represent one of the most successful radiations of tetraodontiform fishes across the world’s oceans and are commonly found in coral reef and other shallow water habitats. Both families have enlarged dorsal and anal fins and swim in a distinctive manner through coordinated movement of these structures. However, filefishes have far more species (106) than triggerfishes (42) and also show a greater range of body sizes and shapes. We discovered that the greater diversity of filefishes is not due to faster rates of speciation or morphological evolution, Instead, we found that filefishes have been around for a considerable longer period of times than triggerfishes, allowing filefishes to evolve into a greater diversity of forms even though both families are diversifying at similar evolutionary rates. Our research led to the discovery of a new and powerful method for reconstructing evolutionary trees that can sample more than 100 times the number of genes that are typically used in evolutionary studies. This approach will have broad utility for future studies of fish evolutionary history. We also taught workshops on phylogenetics and evolutionary biology at the largest meeting of organismal biologists in North America, the Society for Integrative and Comparative Biology. We taught a research seminar on the evolution of coral reef fishes to UCLA students in the Minority Access to research Careers program. And we have trained postdoctoral scholars, graduate students and undergraduate students in the Alfaro lab in the areas of phylogenetics, comparative biology, PCR, UCE-based phylogenomics, informatics, evolutionary morphology, geometric morphometrics, and laser scanning.
