The Evolution of Life-History and Development in Echinoids: A Test for the Role of Environmental Factors and Macroevolutionary Correlates

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9706579 Emlet Life-history and development of marine invertebrates are closely linked - species that make many small eggs produce feeding larvae and those that make few(er), large(r) eggs produce either pelagic, nonfeeding or brooded offspring. These traits are thought to reflect ecological and environmental factors. Though life-history/developmental patterns are will described for many extant taxa and to some degree correspond to latitudinal and thus climatological conditions, the reasons for (or consequences of ) these patterns are poorly understood. For instance, several studies on fossil gastropod mollusks have reported correlations between life-history/development and speciation rates and geographical range, but reasons for shift in development remain obscure. The present proposal will investigate a clade (Class: Echinoidea, Phylum: Echinodermata) with a good fossil record which has evolved non-planktotrophy (=nonfeeding larvae or brooding) in many independent lineages. The study will examine where, when and under what environmental conditions different life-history/developmental patterns occurred in the Tertiary (last 65 Ma). The objectives of this proposal are to: 1) Construct morphological and molecular phylogenies for temnopleuroid echinoids in order to resolve the numbers of times that nonfeeding development has evolved in this order. 2) Examine whether life-history/developmental mode affects speciation rate or geographic range of sea urchins. 3) Explore the environmental conditions under which life-history/developmental modes shift to few large eggs and non-planktotrophic development. A morphological character set consisting of some 60+ characters will be collected from some 30-40 living and fossil genera or subgenera. Visits to major museums collections in Australia, Europe and India will be undertaken to study fossil and Recent types and to collect the character set. The phylogenetic analysis of the temnopleuroids will use standard numerical cladistics, e.g. the s oftware program PAUP will be used to construct maximally parsimonious trees that will be subsequently explored for phylogenetic structure and robustness. For the molecular phylogeny, partial sequences of 28S rRNA and mitochondrial cytochrome oxidase I (COI) genes will be collected from ~ 15 genera and subgenera of temnopleurid and integrated with a molecular database already constructed for echinoids. DNA will be extracted and amplified with PCR, and gene fragments will be sequenced in an automated sequencer. Following sequence alignment, phylogenetic trees will be constructed using both parsimony (PAUP) and maximum-likelihood (PHYLIP). Using a total evidence approach, morphological and molecular data will be combined in order to estimate the best phylogenetic tree for the group using the methodologies outlined above. Developmental data for fossil and Recent taxa will be mapped onto the tree(s) to determine the number of times and locations where non-planktotrophy evolved. The patterns of development among temnopleuroids and other fossil taxa with known phylogenies will be explored to determine whether or not life-history/developmental mode affects speciation rate or geographic range of sea urchins as has been shown for some gastropod molluscs. Finally the environmental conditions under which life-history/developmental modes shift will also be examined quantitatively and statistically. The proposed research will be the first detailed study of the evolution of life history (and developmental mode) for a group with a good fossil record specifically set within a truly rigorous phylogenetic framework. Consequently, this study will provide a temporal and spatial evolutionary history of developmental patterns that have remained largely speculative because they are based on patterns of Recent taxa or on theory. This study should also improve understanding of how global change can drive significant alterations in the developmental patterns of echinoids (and marine invertebrates in genera l). The work will also result in a secure phylogeny for a major group of echinoids, which can subsequently be used to explore further patterns of evolution through time.