Species and Speciation Flashcards

Alleles and Substitution Rates

• When examining alleles known to be neutral, such as those arising from synonymous mutations:
  • The rate of substitution equals the rate of mutation.

Non-Neutral Alleles

• If new mutant alleles are not neutral, they are either selected for or against.
  • If selected for: the rate of substitution will be higher than their rate of mutation.
  • If selected against: the rate of substitution will be lower than their rate of mutation.

Evolutionary Rates

• Evolutionary rates vary across different genomic regions.
  • Rates are generally lower in coding regions due to stronger selection against changes that alter protein function.
    *Rate increases in psuedogenes, Introns and intergenic regions.

Population Size and Selection

• Population size (N_e) significantly affects the efficacy of selection.
  • Alleles with a small selective advantage (e.g., 0.01) can evolve by drift, especially in small populations.

Species and Speciation

• What defines a species?
• How do new species form?

Species Concepts

• What are species and how do we define them?
• Are species "real" biological entities, and why does it matter?
• Distinction between the definition (concept) of a species and the criteria used to identify them.

The Nature of Species

• The view that species are defined by fixed characteristics is a Platonic perspective, which is inaccurate in modern biology.

Individuals vs. Classes

• Classes Exist in our heads (artificial).
• Individuals Exist without our heads (natural).

Characteristics of Classes

• Exist in our heads and are therefore artificial constructs.
• Have sharp, well-defined boundaries.
• Are timeless, existing outside of temporal constraints.
• Are spaceless, existing outside of spatial constraints.
• Cannot undergo natural processes like evolution.

Characteristics of Individuals

• Exist independently of human perception and are natural entities.
• Have fuzzy, less defined boundaries.
• Exist in time, with a beginning and an end.
• Exist in space, occupying a specific location.
• Can undergo natural processes, such as evolution and adaptation.

Examples of Classes vs. Individuals

• Elements vs. atoms

Terms Related to Speciation

• Sympatric: Occurring within the same geographic area.
• Allopatric: Occurring in separate, non-overlapping geographic areas.
• Parapatric: Occurring in adjacent geographic areas with some overlap.

Biological Species Concept (BSC)

• Groups of actually or potentially interbreeding populations, which are reproductively isolated from other such groups.
• Reproductive isolation (Repro Iso) not always 100% necessary or clear-cut.
• The concept can be arbitrary and difficult to apply, especially to allopatric populations.

Limitations of BSC

• Asexual species: BSC is not applicable to species that reproduce asexually.
• Hybridization: complicates species definitions.
• Difficulties in parapatric populations: Determining reproductive isolation can be challenging even in adjacent populations.

Introgression

• Introgression, the transfer of genetic material from one species into another through hybridization, does occur in nature.

Practical Application of BSC

• Rarely used directly. Instead, morphology and/or genetic differences are relied upon to delineate species.