Biodiversity and Species Concepts
This area examines what a species is, how new species are described, and how systematics measures and documents the diversity of life.
Definition
Species concepts are the differing criteria by which biologists define species; biodiversity documentation is the systematic effort to discover, describe, and inventory the variety of living organisms.
Scope
This area covers the long-running debate over species concepts, the practice of describing and naming new species (alpha taxonomy), and the documentation of biodiversity, including the shortfalls and the taxonomic impediment that limit our knowledge of how many species exist. It links systematic theory to the practical task of cataloguing life.
Sub-topics
Core questions
- What is a species, and why do definitions differ?
- How are new species discovered, described, and named?
- How much of Earth's biodiversity remains undocumented?
- What limits our knowledge of biodiversity?
Key theories
- Unified species concept
- de Queiroz argued that most species concepts share the idea of separately evolving lineages and differ only in which secondary criteria they emphasize for recognizing such lineages.
- Biological species concept
- Mayr defined species as groups of actually or potentially interbreeding populations reproductively isolated from other such groups, a foundational and influential criterion.
- Shortfalls in biodiversity knowledge
- Large gaps in taxonomic, distributional, and other knowledge, summarized as a set of named shortfalls, constrain our understanding of global biodiversity.
Clinical relevance
How species are defined and how completely biodiversity is documented affect conservation policy, the discovery of natural products, and the recognition of species relevant to disease, agriculture, and ecosystem services.
History
The species problem runs from pre-Darwinian essentialism through Mayr's mid-twentieth-century biological species concept to a proliferation of concepts and de Queiroz's later unification; in parallel, awareness grew of how little of Earth's biodiversity has been described and of the workforce shortage known as the taxonomic impediment.
Debates
- Pluralism versus unification of species concepts
- Some hold that different concepts capture genuinely different biological realities and should coexist, while others argue they are facets of one underlying lineage concept, as in de Queiroz's synthesis.
Key figures
- Ernst Mayr
- Kevin de Queiroz
Related topics
Seminal works
- dequeiroz2007
- mayr1942
- hortal2015
- winston1999
Frequently asked questions
- Why do biologists disagree about what a species is?
- Different concepts emphasize different evidence, such as interbreeding, distinct lineage history, or diagnosable differences, so they can disagree on borderline cases even while agreeing on clear ones.
- How many species have been described?
- Roughly two million species have been formally described, but estimates of the true total run much higher, so a large fraction of biodiversity remains undocumented.