Species concept

Question 1

how can species mirror each other?

Answer 1

via convergent evolution

Question 2

adaptive radiation

- what is it?

Answer 2

organisms diversify rapidly from an ancestral species into a multitude of new forms

Question 3

adaptive radiation

-example

Answer 3

fish in Lake Malawi + Lake Victoria both have different species occupying different niches
e.g. snail crusher, bottom feeder etc

Question 4

People have struggled w/ defining species for many yr

-> but which is the most common?

Answer 4

biological species concept

Question 5

Mayr’s biological species concept

Answer 5

groups of interbreeding populations which reproductively isolated from other such groups

Question 6

Barriers to recombination

Answer 6

Adaptive barriers
= selection against hybrid genotypes

Mechanistic barriers
= factors promoting DNA specificity
(chromosomal incompatibility)

Ecological barriers
= consequence of physical separation of populations

Question 7

Mechanistic barriers

- example

Answer 7

Horse + donkey = mule
- sterile hybrid

= pre-zygotic barrier

Question 8

Ecological barriers

- example

Answer 8

Ring species
- 2 gull populations which don’t interbreed are living in the same region and connected by a geographic ring of populations that can interbreed

Question 9

Fuzzy species

• Paper by?
• suggests?

Answer 9

Hanage et al (2005)

Bacteria don’t have discrete species clusters

Question 10

MLST

- what is it?

Answer 10

Multilocus sequence typing
- characterises isolates of microbe species
using DNA sequences of internal fragments of multiple housekeeping genes

Question 11

MLST

- of Campylobacter

Answer 11

sequenced 7 genes to understands variation in different strains

• revealed interspecies hybrids

-> some strains had genes attributable to C. jejuni + C.coli
= HGT

Question 12

introgression

Answer 12

transfer of genetic information from 1 species to another

as a result of hybridisation between them + repeated backcrossing

Question 13

de-speciation

Answer 13

if gene flow between 2 species maintained at a high rate

-> 2 species may come together

Question 14

hybridisation has implications for…?

Answer 14

species concepts

adaptive radiation

Question 15

hybridisation has implications for adaptive radiation

- example

Answer 15

Darwin’s finches on Galapagos
- adaptive radiation to fill the niches (food source)

if ecology changed

• > great increases in the no. of intermediate birds
• > enviro would then favour them instead

Question 16

introgression in Campylobacter

- associated with?

Answer 16

agriculture

• consistent with scenario where expansion into a shared agricultural niche promotes de-speciation

Question 17

Agricultural C.coli have hybrid ancestry

Answer 17

use a pair-wise comparison between genes of different speciess:

some genes may never have diversified
= conserved

may be periods of independent evolution where 2 species diversified
-> then HGT imported genes back into these hybrid strains from other species

Question 18

Introgression occurs across a great genetic distance

- amnio acid differences per gene

Answer 18

C. jejuni to C. coli
= 38

Within C.jejuni = 5.5

Human to chimp = 2.9

Question 19

Introgression might aid adaptation to novel enviros BUT might be disruptive

Answer 19

Sex beneficial

• generates genetic diversity
• > natural selection for the well adapted

Sex is a barrier

• recombination breaks gene networks
• > less well adapted

Question 20

Introgression might aid adaptation to novel enviros

- example

Answer 20

Rieseberg et al (2003)

Sunflower hybrid (intermediate species)
- did very well
shuffling of genomes created rapid innovation
–> successful at colonising new niche (novel habitat)

Question 21

chromosome painting

- what is it?

Answer 21

describes the direct visualisation using in situ hybridisation of specific chromosomes in metaphase + interphase nuclei

Question 22

chromosome painting

- purpose

Answer 22

quantities gene flow

identifies regions of different ancestry in the genome

Question 23

identifying donor clonal complexes

• how?
• example

Answer 23

look at ancestors of a hybrid + see which base can from which ancestor

donor: C. jejuni
recipient: C. coli
most introgression came from chicken associated Campylobacter

Question 24

epistasis

co-adaptation

Answer 24

interaction of genes where the phenotype of one depends on the other

Question 25

modelling co-adaptation

Answer 25

epistatic sites change more frequently than avg

mutations that are fixed just occur on 1 branch
BUT epistatic sites are found together on multiple branches