roadmap 7&8

What is the Biological Species Concept (BSC)?

Species are groups of actually or potentially interbreeding natural populations that are reproductively isolated from others.

What is the main strength of the BSC?

It focuses on reproductive isolation, the key to preventing gene flow.

What are limitations of the BSC?

Cannot apply to asexual organisms, fossils, or cases involving hybridization.

What is the Morphological (Morphospecies) Concept?

Species are distinguished by physical/morphological differences.

What is a limitation of the Morphological Species Concept?

Cryptic species may look the same, and variation within species can be misleading.

What is the Phylogenetic Species Concept (PSC)?

The smallest diagnosable cluster sharing a common ancestor (monophyletic).

What is a strength of the PSC?

Works with DNA and fossils.

What is a limitation of the PSC?

May over-split groups into many small species; depends on sampling quality.

What is the Unified/Integrative Species Concept?

Uses multiple lines of evidence (genetic, morphological, ecological, reproductive).

What do grizzly and polar bears illustrate about species concepts?

They are morphologically distinct but hybridize; considered separate species under some concepts but not others.

What is reinforcement in hybrid zones?

Selection strengthens reproductive barriers because hybrids are unfit, leading to greater separation of species.

What is a stable hybrid zone?

A geographic area where hybrids form regularly, but parental taxa remain distinct.

What is fusion (speciation reversal)?

Extensive hybridization erases differences between lineages and merges them back into one species.

What is hybrid speciation?

A new lineage forms when hybrids themselves become reproductively isolated (rare but documented).

What is an example of fusion/speciation reversal?

Previously distinct raven lineages fused when they re-met in some areas.

What is an example of fertile hybrids?

Many ducks, some cetaceans, bears, wolves/coyotes can produce fertile hybrids.