Empirical and philosophical problems with the subspecies rank

Area of Science:

• Integrative Taxonomy
• Evolutionary Biology
• Philosophy of Science

Background:

• Species-level taxonomy relies on diverse species concepts and empirical data to identify evolutionary lineages.
• Current species concepts often fail to integrate epistemological methods with ontological understanding of species.
• The subspecies rank persists as a problematic placeholder for lineages undergoing divergence or merging.

Purpose of the Study:

• To critically evaluate the philosophical and empirical justifications for the subspecies rank.
• To demonstrate the incoherence of using subspecies and reproductive isolation as primary taxonomic criteria.
• To propose a framework for species recognition that bridges theoretical and operational species concepts.

Main Methods:

• Philosophical analysis of species concepts and taxonomic ontology.
• Empirical review of methods assessing lineage independence and reproductive isolation.
• Critique of the Biological Species Concept's limitations regarding genealogy and evolutionary ontology.

Main Results:

• The subspecies rank is ontologically either identical to species or undefined for evolutionary lineages.
• Reliance on reproductive isolation is often indirect and fails to capture complex gene flow dynamics.
• The use of subspecies can conflict with ethical considerations in species conservation.

Conclusions:

• The subspecies rank is indefensible and should be abandoned in species-level taxonomy.
• A unified approach linking theoretical and operational species concepts is necessary for robust taxonomy.
• This framework aims to improve species recognition and naming, irrespective of reproductive isolation levels.