Phylogenetics and Species Concepts: Amniote Relationships and Molecular Data

What is a synapomorphy?

A derived trait shared by a group of organisms.

What is a symplesiomorphy?

An ancestral trait shared by multiple groups.

How can a synapomorphy become a symplesiomorphy?

As new groups evolve that inherit that character from their ancestor.

What is the significance of the presence of a gizzard in birds and alligators?

It is a synapomorphy for birds and alligators but can be a symplesiomorphy for groups within those lineages.

What are the monophyletic groups listed in the tree?

BF, CD, BECD, EBFCD, AEBFCD.

Is the traditional classification of reptiles consistent with the phylogenetic tree?

No, it is not consistent because they are separated into different groups.

Would a modern phylogenetic systematist approve of a clade consisting of only alligators and lizards?

No, because alligators and birds share more common characters.

What is an example of convergent evolution in the tree?

The three-chambered heart, first present in mammals and later developed in birds and alligators.

Which fossil would you expect to find earlier in the geological record: a mammal or an alligator?

A fossil that could be classified as a mammal, because mammals developed first according to the tree.

Would the early mammal fossil resemble modern mammals?

No, because early fossils would have older characteristics than modern mammals.

Can snakes be considered tetrapods?

This requires explanation and justification based on their evolutionary history.

Are snakes tetrapods?

Yes, snakes are tetrapods because they descended from a four-limbed tetrapod ancestor.

What does it mean if phylogenetic analysis results in multiple equally parsimonious trees?

It indicates ambiguity or conflict in the data used to build the trees.

What is a strict consensus tree?

A tree that represents only those clades present in all equally parsimonious trees.

What is the consistency index (CI) in phylogenetics?

CI measures the relative amount of homoplasy in a tree, ranging from 0 to 1.

What does a CI of 1 indicate?

It means the tree has no homoplasy and all characters are homologies.

How is the consistency index calculated?

CI = Ʃ(n - 1) / character state changes on created tree.

What does a CI of 0.7 indicate?

It means that 70% of the data are good representations of the defined resolution.

What are sister groups in phylogenetics?

Sister groups are groups that separate at a node.

What is an example of a sister group for birds?

Alligators.

Why is understanding phylogenies important for medical researchers?

It helps researchers choose appropriate organisms for medical research and understand the evolution of traits or diseases.

Why is a phylogeny considered a hypothesis?

It is based on previous evidence but cannot be proven.

What tools do phylogeneticists use to determine relatedness?

They use DNA sequences, proteins, or whole genomes.

What is the morphological species concept?

It is based on the fact that the separation of species is due to differing morphological characteristics.

Why is it important to analyze morphological characteristics?

To identify and differentiate species based on their morphological features.

What morphological characteristics should be assessed to predict distinct species?

Body shape, number of antennas, spots vs. stripes, color variations, and number of abdominal sternites.

How will your group analyze and interpret the data collected?

Organisms with different morphological characteristics will be grouped into new species.

How many different species were identified in the analysis?

8 different species.

What is the relevance of analyzing DNA sequences in species identification?

DNA sequences can be compared to see how genetically similar specimens are; closely related specimens have similar DNA.

What does a higher number of DNA differences suggest about specimens?

It suggests that they belong to different species.

What materials are used in the molecular estimates of species investigation?

Mitochondrial DNA sequences of a particular group of organisms.

Why does mitochondrial DNA mutate at a faster rate than nuclear DNA?

Because mitochondria can multiply each time a cell divides.

What is the purpose of comparing mtDNA sequences?

To note differences between species or individuals of the same species.

What is the length of the mtDNA sequence studied?

78 base-pairs.

What is the significance of the outgroup specimen in the analysis?

It serves as a reference to identify genetic mutations in the other specimens.

What is one method to determine if specimens belong to the same species?

Analyzing DNA sequences for similarities and differences.

What is the role of qualitative and quantitative traits in species assessment?

They help in comparing morphological characteristics between specimens.

What is one characteristic that can vary among specimens?

The number of stripes or spots.

What is the importance of agreeing on criteria for species classification?

To ensure consistency in determining distinct species.

What type of data presentation is suggested for morphological comparison results?

A table may be the easiest way to present the data.

What is the expected outcome of the morphological analysis?

To identify the number of distinct species present.

What is one method for analyzing mtDNA data?

Percent similarity of mtDNA sequence base pairs

What is another method for analyzing mtDNA data?

Percent similarity of mtDNA sequence mutations

What method did the group choose for analysis?

Percent similarity of amino acids in the protein

Why did the group choose to analyze amino acids in the protein?

Specimens with similar protein makeup are likely to perform similar functions.

How many species were identified in the sample of 8 specimens?

5 species present

What can patterns in mtDNA sequences help determine?

How closely related each species is and their evolutionary history.

What type of diagram is used to represent evolutionary relationships?

Cladogram or phylogeny.

What is the Molecular Species Concept?

A species concept based on genetic makeup.

What is the Biological Species Concept?

A species concept based on the ability to interbreed and produce viable offspring.

What is a pro of the Morphological Species Concept?

Helps identify groups by morphological traits.

What is a con of the Morphological Species Concept?

Some species can have similar phenotypes but different genetic makeup.

What is a pro of the Molecular Species Concept?

Allows examination of genetic makeup and variance.

What is a con of the Molecular Species Concept?

Uncertainty about what percentage validates species classification.

What is a pro of the Biological Species Concept?

Allows for identification of species that can breed and produce viable offspring.

What is a con of the Biological Species Concept?

Does not account for geographically separated species.

What evidence is needed to apply the Biological Species Concept?

Data on viable, fertile offspring and evidence of reproductive isolation.

What might indicate that two species are closely related?

Overlap in ranges and similarity in mitochondrial DNA.

How could one test if two species are variants of the same species?

Compare more DNA and determine if the two groups interbreed.

How might conservation status be affected by species classification?

If they are the same species, populations may be considered together; if separate, the endangered population may need separate protection.

Should morphological data be rejected in favor of molecular data?

No, both types of data provide useful information for identifying species.

What can molecular data reveal that morphology may not?

Cryptic species that are not detected through morphology.

What is the importance of using both morphological and molecular data?

It provides stronger evidence when identifying species.