Question

Which of the following scenarios would result in a different species designation for two populations under the phylogenetic and biological species concepts?

1) There is no gene flow; all hybrids are sterile
2) Each population forms a monophyletic group; populations mate during different seasons
3) There is no gene flow; fertile hybrids are produced when bred in the lab
4) Each population is paraphyletic; fertile hybrids are produced when bred in the lab

Answer 1

Scenario 2, where each population forms a monophyletic group and populations mate during different seasons, causing reproductive isolation, is the scenario that would produce different species designations under both the phylogenetic and biological species concepts.

Step-by-step explanation:

The question involves determining which scenario would lead to a different species designation for two populations under the phylogenetic and biological species concepts. The phylogenetic species concept classifies species based on evolutionary lineage and requires a species to form a monophyletic group, meaning the populations must have a common ancestor and all of its descendants. In contrast, the biological species concept defines species based on the ability to reproduce and generate fertile offspring in nature, which involves reproductive isolation.

Let's examine the scenarios:

1. 
   
3. There is no gene flow; all hybrids are sterile - Both concepts would result in a different species designation as there is no gene flow and hybrids are sterile.
4. 
   
6. Each population forms a monophyletic group; populations mate during different seasons - The phylogenetic concept might still consider them the same species, but the biological concept would likely consider them different due to temporal reproductive isolation.
7. 
   
9. There is no gene flow; fertile hybrids are produced when bred in the lab - They'd likely be considered the same species under the phylogenetic concept since fertile offspring are produced, but different under the biological concept since lab conditions aren't natural.
10. 
    
12. Each population is paraphyletic; fertile hybrids are produced when bred in the lab - Since they do not form a monophyletic group, under the phylogenetic concept they would be considered different species; the biological concept might still view them as the same since fertile hybrids are possible.

Scenario 2 is the one that would result in different species designations under both concepts as it involves a monophyletic group and a prezygotic barrier with mating during different seasons, preventing gene flow in natural settings.