Patterns of lineage diversification in rabbitfishes

Area of Science:

• Ichthyology
• Evolutionary Biology
• Molecular Phylogenetics

Background:

• The Siganidae family, comprising 28 species of tropical Indo-Pacific fishes, is known for distinct body proportions and color patterns.
• Previous classifications, including sub-genera like Lo and Siganus, lacked clear phylogenetic support.
• Understanding the evolutionary relationships within Siganidae is crucial for comprehending their diversification and adaptation.

Purpose of the Study:

• To infer the evolutionary history of 20 Siganidae species using mitochondrial DNA.
• To investigate the phylogenetic rationale behind current sub-generic divisions.
• To correlate phylogenetic clades with ecological diversification within the family.

Main Methods:

• Mitochondrial DNA sequencing from 20 Siganidae species.
• Phylogenetic tree construction to analyze evolutionary relationships.
• Comparison of molecular data with morphological and ecological characteristics.

Main Results:

• Three distinct major clades were identified, corresponding to fusiform, deep-bodied, and mangrove/estuarine ecological types.
• The sub-generic partition of Lo and Siganus was found to have no phylogenetic basis.
• Evidence suggests recent ecological specialization, such as the acquisition of tubular snouts within the deep-bodied clade.
• Specific sister-species relationships were clarified, with some unexpected groupings and indications of hybridization (e.g., S. randalli).

Conclusions:

• The study establishes a robust mitochondrial phylogeny for Siganidae, revealing three primary evolutionary lineages linked to distinct ecological niches.
• Existing sub-generic classifications are unsupported by phylogenetic data, necessitating revision.
• Morphological and ecological traits, like tubular snouts, represent recent evolutionary acquisitions within specific clades.