ENTM100 Lecture 15 Systematics

Biological species concept

Main criterion: Interbreeding (natural populations)

Also: reproductively isolated from other groups

Species

• Morphological species concept

• Biological species concept

• Evolutionary species concept

• Phylogenetic species concept

• Cohesion species concept

Systematics

study of biodiversity and the relationships among groups of organsims (taxa)

Systematics

1. Taxonomy

2. Phylogenetics

Both contribute to: Species delimitation

Taxonomy

Science of recognizing, describing, and naming taxa and classifying organsims into groups

Phylogenetics

Study of evolutionary history and relatedness

Species delimitation (systematics)

Study of species boundaries

What criterias can you use to evaluate multiple character traits to help diagnose species

1. DNA

2. Morphology

3. Reproduction

4. ecology

5. Geography

6. DNA

Characters

1. Morphological characters

2. Physiological characters

3. Ecological characters

4. Ethological characters

5. Geographical characters

6. Molecular characters

1. Morphological characters (characters)

Think: What does insect look like?

Consider:

• body type

• wings

• leg types

• mouthparts

• antennal types

• Reproductive organs

2. Physiological characters

• What does it look like

• How does the inside of the insect work?

  • Metabolsim

  • Muscles

  • Chemistry

  • Secretions

• Physiological character: Cuticular hydrocarbon

Cuticular hydrocarbon (physiological characters / char)

• Prevents dessication

• Mating cues

• (think about how cuticular is around membrane in plants and plants need water so yeah)

Coptotermes formosanus and coptotermes gastroi

• Both species can be found in Taiwan and southern China

• Both species can be found in Hawaii

3. Ecological characters (characters)

How does the insect live in its environment?

• Habitat, food, parasites, what eats it.

4. Ethological characters (behavior)

Territories, aggression, mate recognition, courtship

(Behavioral information)

5. Geographical characters

Where in the world is it found?

6. Molecular characters

How does its DNA compare to that of other organisms?

Phylogenetics

1. Enables us to uncover the origin, diversification, evolution, and biogeography (distributions both past and present) of taxa

2. Provide us with a better understanding of evolution and genomics

3. Phylogenetic trees

Phylogenetic trees (phylogenetics)

• not restricted to only showing divergencies between taxa

• Can be used to investigate gene evolution

Taxa (phylogenetic trees)

tips of trees

Monophyletic group

ancestor and all descendents

Cladistics

one approach to phyloegenetics

Goal: infer phylogenies using patterns of similarity, based on shared, evolutionarily novel features

Synapomorphies

• Shared evolutionary novel features.

• Evidence that taxa are closely related

(shared derived trait)

Plesiomorphies

Evolutionary features are not shared… not closely related

Ancestral traits

Ancestral trait that is not shared among all descendents

Characters

• used to help us classify taxa

• characters are unique features that are useful for recognizing taxa

Grouping taxa

Group based on homologous character

Homologous characters

• share an origin in a common ancestor

• serve as synapomorphies that define evolutionary groups

(Synapomorphies are homologous characters)

3 tests to tell whether a character/trait is homologous

1. Similarity

2. Congruence

3. Conjunction

Similarity (test)

Does the character being compared across taxa occur in the same location on the insect and develop the same way

• Homologous characters do both

• Same location on insect and develop in same way?

Congruence (test)

• Does the character of interest serve as a synapomorphy

• Does the synapomorphy define a grouping that is supported by other character data?

• Homologous characters do.

Common synapomorphies in other character data?

Conjunction

Does character exhibit two states on the same individual

• Homologous characters DO NOT.

Character exhibit two different states in the same individual

Conjecture

interpretation of character states

(rather than well0defined taxa, etc.)