Ultrastructure as a Control for Protistan Molecular Phylogeny.

Area of Science:

• Evolutionary Biology
• Molecular Phylogenetics
• Protistology

Background:

• Phylogenetic reconstruction of early eukaryotic evolution relies on molecular sequences and treeing methods.
• Resolving the origins of higher eukaryotic taxa necessitates robust and biologically coherent phylogenetic trees.

Purpose of the Study:

• To evaluate the reliability of different phylogenetic approaches in reconstructing early protistan evolution.
• To investigate the coherence between molecular data and morphological/ultrastructural evidence in phylogenetic analysis.
• To address the uncertainty surrounding the root of the eukaryote tree.

Main Methods:

• Comparative analysis of molecular sequences (ribosomal DNA, mitochondrial DNA, other genes).
• Integration of morphological and ultrastructural data with molecular phylogenies.
• Assessment of tree robustness and coherence with diverse datasets.

Main Results:

• Ribosomal DNA trees generally align with major eukaryotic lineages, supported by ultrastructural data.
• Mitochondrial crista type is consistent with mitochondrial DNA sequences.
• Some amitochondrial groups exhibit positional volatility in phylogenies based on different genes, questioning their basal position.

Conclusions:

• Morphological and ultrastructural data are essential for validating molecular phylogenies and resolving phylogenetic ambiguities.
• The root of the eukaryote tree remains uncertain, partly due to potential mimicry of primitiveness by parasitic organisms.
• Conflicting molecular phylogenies require integration with non-molecular data for accurate reconstruction of early eukaryotic evolution.