bio ex 3 species stuff

Defining and Identifying Species

• Biological Species Concept

• Morphological Species Concept

• Phylogenetic Species Concept

The Biological Species Concept ft. problems

• Species are “... groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups” - Ernst Mayr

• Problems:

  •  interpreting the past

  • Species without sexual reproduction

  • Hybridization (ie. the humble mule)

The Morphological Species (Morphospecies) Concept ft problems

• Species are determined based on morphological similarities

  • Geographic variation

  • Cryptic speciation: frogs with similar colors, but are diff species

The ecological species concept ft problems

• Species/individuals that share an ecological niche are the same species

  • Ecological constraints should breed, sumn sumn

  • Multiple species share same subset of niche

    • But have diff realized niches

Phylogenetic Species Concept

“According to the PSC, a species is the smallest aggregation of populations that can be diagnosed by a unique combination of character states in comparable individuals”

Disruptive Speciation

• Disruptive selection – selection that will disrupt and remove middle, resulting in favoring individuals of either extreme 

  • Median becomes disadvantageous, so creates species on either extreme with no overlap 

    • Ie. middle beak size gone, now just big beak and small beak

How do species form? sym vs allo

• Sympatric: speciation occurs where population overlaps with one another 

• Allopatric: different places in which they live

  • Separation due to dispersal/colonization

  • Separation due to geographic barriers

How do species remain separate entities — reproductive isolation: prezygotic

• Prevent gamete fusion

  • Ecological isolation – lions and tigers

  • Species cluster – hawaiian drosophila

  • Temporal isolation

    • Wild lettuce flowering:

    • Lactuca graminifolia vs. L. canadensis

  • Mechanical isolation: morphological traits that prevents two individuals from reproducing with one another

    •  snails where reproductive organs are on diff part of body

  • Behavioral isolation – birds with diff mating dances

How do species remain separate entities — reproductive isolation: postzygotic

• Number of mechanisms prevent the proper development or reproduction of the zygote after it forms 

  • Reduced hybrid viability

    • Offspring generated either die prior to or very quickly after hatching 

  • Reduced hybrid fertility

  • Hybrid breakdown

    • F1 generation: very fertile

      • Two F1 plants reproduce F2 plant, F2 is less fit than either parent or parents tht generated F1

        • Reduced fitness

      • Two F2s, F3 less fit or inviable

maybe jeffersonian