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Phylogeny and evolution of developmental mode in temnopleurid echinoids
Charlotte H Jeffery1, Richard B Emlet, D T J Littlewood
1Oregon Institute of Marine Biology, University of Oregon, P.O. Box 5389, Charleston, OR 97420, USA. chj@liv.ac.uk
Molecular Phylogenetics and Evolution
|June 13, 2003
Summary
Phylogenetic analysis of temnopleurid echinoids reveals evolutionary relationships and developmental shifts. Planktotrophy is ancestral, with a single transition to lecithotrophy occurring millions of years ago.
Area of Science:
- Marine Biology
- Echinoderm Phylogenetics
- Evolutionary Developmental Biology
Background:
- Temnopleurid echinoids represent a diverse group with complex evolutionary histories.
- Previous studies relied heavily on morphological data, leading to unresolved phylogenetic questions.
- Understanding their evolutionary trajectory is crucial for interpreting patterns in marine invertebrate development.
Purpose of the Study:
- To establish robust phylogenetic relationships among 24 nominal species of temnopleurid echinoids.
- To investigate the evolution of developmental patterns, specifically the transition from planktotrophy to lecithotrophy.
- To test hypotheses regarding genus monophyly and subgeneric classifications within the Temnopleuridae.
Main Methods:
- Combined molecular data (mitochondrial 16S rRNA, cytochrome c oxidase subunit I; nuclear 18S rRNA) with morphological traits (coronal, lantern, spine, pedicellarial).
- Utilized data congruence tests (Templeton's, incongruence length difference) to assess data set compatibility.
- Performed a total evidence phylogenetic analysis to integrate all data sets.
Main Results:
- The analysis resolved phylogenetic relationships, indicating that Microcyphus, Amblypneustes, and Holopneustes are not monophyletic.
- Temnopleurus (Temnopleurus) and Temnopleurus (Toreumatica) are distantly related and should not be considered subgenera.
- Mespilia shows closer affinities to Temnotrema and Toreumatica than previously suggested, challenging existing classifications.
- Planktotrophy is the ancestral condition; a single evolutionary transition to lecithotrophy occurred 4.4-7.4 million years ago, with no reversals.
Conclusions:
- The study provides a well-resolved phylogeny for temnopleurid echinoids, refining taxonomic classifications.
- A single, unidirectional evolutionary shift to lecithotrophy explains its prevalence in certain genera.
- Phylogenetic insights inform our understanding of developmental evolution in marine invertebrates and biogeographic patterns.