Leture 31 - GMOs, Species, and Speciation

What are two kinds of transgenic crops?

1. Engineered insect resistance from bacterial genes (Bacillus thuringiencsis)

2. ENgineered herbicide resistant

What are reasons for transgenic plant controversies?

1. Human health concerns

2. Harm comes to beneficial insects and aquatic invertebrates

3. Genes from insecticide resistance might spread to weedy plants and cause them to be more common

4. Promotion of monoculture and the reliance of GMOs may reduce diverse crops

5. Diversity will not be promoted and will therefore minimize the effect of future plant diseases

How are insects affected by insecticides?

Constant exposure to the toxin creates evolutionary pressure for pests to become resistant to that toxin and mutations can spread quickly

How is insect resistance being counteracted?

The creation of non-BT crop reguge allows non-resistant insects to survive and maintain a susceptible population. BUT it assumes that resistant mutations are recessive

Phenetic species concept and problems

1. characterizes species based on phenotypes

2. Difficult to distinguish

3. Arbitrary selection of traits result in different groupings

4. Used for fossil species characterization

Biological species concept

INterbreeding, natural populations that are reproductively isolated from other groups

Why does the biological species concept not work?

1. Does not account for asexually reproducing single-celled organisms or multi-celled organisms

2. Does not account for when two morphologically similar groups of organisms are potentially capable of interbreeding

Are are bacterial species defined?

Species are usually expected to share at least 70% binding of standardized DNA/DNA hybridization and/or over 97% gene-sequence identity for 16S ribosomal RNA

Ring species

Members of adjacent populations interbreed successfully BUT members of widely separated populations do NOT

What are 5 prezygotic mechanisms of isolation between species?

1. Ecological isolation

2. Temporal isolation

3. Mechanical isolation

4. Gametic isolation

5. Behavioral isolation

Ecological isolation

Different habitats in the same region

Temporal isolation

Mating in different seasons or times of day

Mechanical isolation

physical constraints to mating

Gametic isolation

Gametes do not attract and are fusion inviable

Behavioral isolation

When mating signals are not read by the female

What are 3 postzygotic mechanisms of isolation?

1. Hybrid inviability

2. Hybrid sterility

3. Outbreeding depression