#2 Systematics

Systematists

The study of the evolutionary relationships among organisms and their classification into a hierarchical scheme

What does systematists classify organisms by?

Evolutionary relationships

What do taxonomists do?

Identify, describe & name organisms

What does theoretical systematics do?

Understand & clarify evolutionary history

What does applied systematics do?

Identify distinct taxa (ESUs) for conservation

• also→ Determines degree of hybridization

How many species of birds were there during the Mesozoic?

100,000

How many species of birds are there today?

~10,500

What leads to variation in the number of species over time?

• Extinction

• Phyletic evolution?

• Speciation

What is one pathway that leads to variation?

Speciation → geographic isolation→ pressure to adapt/continental drift → genetic variance

Allopatric speciation

Populations diverge in isolation

Sympatric speciation

Divergence of populations with overlapping ranges

• Started being the same species and then diverged into another

How are Darwin’s Finches an example of allopatric speciation?

• Speciation from repeated dispersal events

  • Sequential colonization of islands

  • Successive isolation & evolution/Adaptation

  • Recolonization of islands

  • = Speciation

What are the 2 Species Concepts?

• Biological Species Concept

• Phylogenetic Species Concept

What are the 2 Species Concepts for?

To help scientists categorize life by different criteria, leading to a deeper understanding of evolutionary relationships and the formation of new species

What is Biological Species Concept based on?

Reproductive isolation

• Can they breed and produce fertile offspring?

  • if yes = same species

  • if no, then different species

What is one problem with the Biological Species Concept?

• Hybridization

  • Doesn’t account for all the hybridization that happens

What is Phylogenetic Species Concept based on?

shared derived characters

What is one problem with the Phylogenetic Species Concept?

• Choosing characters

  • Harder to apply

  • Pick how much weight to give characters to define a particular species from another one

What must phylogenies be based on?

The presence/absence of characters in each species

Broad phylogenies

Examines the evolutionary relationships among a wide and diverse range of organisms

What are some broad phylogenies?

• Bill shape

• Bone structure

• Organs that have new functions

  • Adaptations to eat plants

Fine phylogenies

A detailed and highly resolved reconstruction of evolutionary relationships

What are some fine phylogenies?

• Coloration

• Behavior 

• Vocalization

What are Apomorphies?

Derived characters that have evolved in a lineage and distinguish it from its ancestral state

What are Synapomorphies?

shared derived characteristics that evolved in a common ancestor and are present in all its descendants

What units taxa together?

Synapomorphies

What are Homoplasies?

traits that are similar between different organisms but evolved independently

In the case of a homoplasy, is there a clear common ancestor that has the trait?

No

• Probably derived multiple times 

• Doesn’t mean they are closely related

• Most likely something that evolved two separate times

What is taxonomy based on?

• in the past

  • morphology

  • behavior

• now

  • molecular methods

What are some examples of Taxonomy characters→ Morphology?

• Skeletal – palate, keeled sternum

• Musculature – syrinx, hind limbs

• Scales – of the foot

• Sperm – structure

What are some examples of Taxonomy characters→ Behavioral?

• Courtship – Avocet pre-copulatory displays, lovebird nesting

• Song – ability to sing, dialects

What are some examples of Taxonomy characters→ molecular?

• Karyotype

• Allozymes

• DNA-DNA hybridization

• nuDNA, mtDNA

Can’t get a taxonomic change taken into consideration without what?

molecular work

• needs to support it

How do we use karyotypes in taxonomy?

Look at shape and size of chromosomes and use it as a shared characteristic

• Very old method, don’t really do this

Why don’t we use Karyotypes in taxonomy?

Doesn’t give us any info about what those chromosomes are for/what their function is

• Not very useful in distinguishing species

• <5% of species have been karyotyped

What new type of Molecular Taxonomy replaced the karyotype method?

Electrophoresis

What does Electrophoresis do?

It separates and analyzes bigger molecules like DNA and proteins, based on their size and electrical charge

• Better way to look at shared characteristics between species

Phenotypic variation

Variation in mass, charge of proteins (=enzymes)

• directly determined by a protein's amino acid sequence

  • which will show an observable differences in physical, behavioral, and physiological traits among individuals of the same species within a population

What is Phenotypic variation used in?

Electrophoresis

Why was DNA Hybridization so important/significant?

Rewrote the evolutionary tree for birds

What did DNA Hybridization look at?

Phylogenetic similarity indexed by dissociation temperature

How does DNA Hybridization work?

• Take two spp and you heat up their DNA to split into separate strands, then mix them

  • 80-90% already similar b/c they are two birds

  • Anywhere they are similar they will bond back together

  • Take this new hybrid DNA and slowly heat up (look for when/what temp does it break)

How can you determine if two species are similar using DNA Hybridization?

• More similar = more heat it will take to break apart 

• The number of temp = how similar the two DNA strands are

What are some examples in which DNA Hybridization helped taxonomy?

• Ratites group together

• Owls with goatsuckers

• Large number of taxa in Ciconiiformes… Nearctic/Neotropical vultures grouped with storks...then with raptors.

• Passeriformes restructured

What does nuDNA and mtDNA look for?

Tracing maternal lineages and recent evolutionary events

• Examines sequences of base pairs and individual genes

What was the most recent major rewrite of birds based on nuDNA and mtDNA?

• All birds can be grouped into three major groups

  • Galloanserae

  • Palaeognathae

  • Neoaves

What does Galloanserae include?

galliformes and anseriformes

What does Palaeognathae include?

• Ratites 

  • kiwis

  • ostriches and emus

What does Neoaves include?

• Everything else

  • Caprimulgiformes

  • Columbaves

  • Gruiformes

What are some types of Ecto-Parasites?

• Lice

• mites

• ticks

• flies

What is interesting about the Ecto-Parasite lice?

Almost every bird species have their own lice species that evolved with them

What is Lumping, in terms of taxonomy?

The taxonomic practice of combining two or more previously recognized species or other taxonomic ranks into a single, broader one