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What is speciation?`

‘Evolution of reproductive isolation within an ancestral species, resulting in two or more descendant species. (Futuyma 2005)


What is anagenesis?

The evolution of a new species along a single lineage due to significant morphological changes


What is cladogenesis?

The evolution of more than one new species from the same common ancestor. It occurs in a branching pattern


3 reasons why speciation is important

1. Speciation generates biodiversity
2. Speciation events is the distant evolutionary past generates high level branching
3.The study of speciation reveals the role of genetic processes and natural selection in evolution


What 3 methods have been used to demonstrate that species exist

Common sense
Statistical methods


What is the common sense argument for the existences of species

Species are real because we recognise organisms to be distinctly different , not in a continuum


Who was a significant advocate of the common sense species argument and what did he say

Dobzhansky 1937 noticed that there were discrete groups everywhere, in both animals and plants, and that this grouping must be a fundamental characteristic of organic diversity


Flaw of the common sense argument

Does not provide hard evidence for the existence of sp.


What does the folk argument for species involve

Involves surveying regions indigenous peoples and compare lists of animal and plant types with Linnaean species.


What are the 2 outcomes of a Folk vs Linnaean survey that provide evidence for the existence of species

1. a one to one correspondence or
2. the folk species are under-differentiated ie 2 or more Linnean species per folk species as untrained observers may not be able to tell cryptic species apart


What are the is the one outcome of a Folk vs Linnaean survey that provides evidence against the existence of species

If the folk species are over-differentiated


Does the Folk vs Linnean sruveys actually show

Remarkable concordance between folk and Linnean species ie folk species either matched or were undifferentiated Majnep & Bulmer 1977


What goals should a species concept fufill

Help with systematic classification
Corresponds with the distinct entities we see in nature
Help us understand how species arise
Represent evolutionary history of organisms
Apply to as many organisms as possible


What are the 4 most common species concept

Biological Species Concept
Morphological species concept
Genotypic Cluster


Pros for the morphological species concept

It is wildly applicable, including asexual and fossilised organisms


Cons for the morphological species concept

Can be arbitrary and subjective, how big a difference does there need to be to call it a new species.
Cant distinguish morphologically similar species who are phenogentically very different with different evolutionary histories


Name a cryptic species which shows how the morphological species concept fails

The pipistrelle bat was thought to be one species but differences in mitochondrial DNA showed that it was actually 2; the common pipistrelle and the soprano pipistrelle


Define the morphological species concept

A lineage thought to be evolutionary independent on the basis of size, shape of another morphological features


Define biological species concept

Groups of actual/potential interbreeding populations that are reproductively isolated from other such groups


Pros of the biological species concept

Stresses the importance of a total lack of gene flow/ being genetically isolated
Can be tested, can 2 chosen populations successfully interbreed
It is widely adopted and in the USA it is a legal definition


Cons to the biological species concept

Cannot be applied to fossils or asexual organisms
Testing the ability to interbreed is a time consuming process
Lots of currently defined species can hybridise and form fertile offspring


What is the phylogenetic species concept

a species is defined as the smallest monophyletic group of common ancestry


3 pros to the phylogenetic species concept

Applies to asexuals and fossils
Utilises ever increasing phylogenetic data
Separateness in the phylogeny reflects genetic isolation


3 cons to the phylogenetic species concept

It doesn't create a stable system as the increasing data will encourage phylogenies to change
Difficult to form robust phylogenies, especially molecular phylogenies
Not clear which elements should be used to construct the phylogenetic tree


Example of the phylogenetic species concept in use

After comparing 4 nuclear genes, Roca et al. 2001
Forest v. Savannah Elephants show 58% of difference shown between African and Asian Elephants and distinguished the african forest elephant as it's own species


Define Genotypic Cluster Species Concept

Species are groups that remain distinct in sympatry due to the morphological and genotypic gaps between them


3 Pros to Genotypic Cluster Species Concept

Combines elements of both the phylogenetic SC and the Biological SP
It's pragmatic, doesn't require speciation to occur in allopatry
aims to separate definition of species from hypotheses about how speciation occurs


2 cons to the Genotypic Cluster Species Concept

It still has elements of subjectivitiy such as the morphological SC e.g
Not widely used, used for butterflies and now occasionally in fish


Example of a species following the Genotypic Cluster Species Concept

Heliconius cydno and Heliconius melpomene hybribise in nature and in labs to form Heliconius heurippa. This butterfly has a hybrid genome and shows reproductive isolation as it doesn not mate with it's parent species.


Give an example where the different species concepts don't agree

Under MSC, Red Wolf is a species
Under BSC, it is not a species as it hybridises with the Coyote
Phylogenetic SC - suggests red wolves result from hybrids between the Gray Wolf and the Coyote as no part of its DNA is unique