Species concept Flashcards

1
Q

how can species mirror each other?

A

via convergent evolution

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2
Q

adaptive radiation

- what is it?

A

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

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3
Q

adaptive radiation

-example

A

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

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4
Q

People have struggled w/ defining species for many yr

-> but which is the most common?

A

biological species concept

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5
Q

Mayr’s biological species concept

A

groups of interbreeding populations which reproductively isolated from other such groups

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6
Q

Barriers to recombination

A

Adaptive barriers
= selection against hybrid genotypes

Mechanistic barriers
= factors promoting DNA specificity
(chromosomal incompatibility)

Ecological barriers
= consequence of physical separation of populations

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7
Q

Mechanistic barriers

- example

A

Horse + donkey = mule
- sterile hybrid

= pre-zygotic barrier

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8
Q

Ecological barriers

- example

A

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

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9
Q

Fuzzy species

  • Paper by?
  • suggests?
A

Hanage et al (2005)

Bacteria don’t have discrete species clusters

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10
Q

MLST

- what is it?

A

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

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11
Q

MLST

- of Campylobacter

A

sequenced 7 genes to understands variation in different strains

  • revealed interspecies hybrids

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

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12
Q

introgression

A

transfer of genetic information from 1 species to another

as a result of hybridisation between them + repeated backcrossing

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13
Q

de-speciation

A

if gene flow between 2 species maintained at a high rate

-> 2 species may come together

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14
Q

hybridisation has implications for…?

A

species concepts

adaptive radiation

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15
Q

hybridisation has implications for adaptive radiation

- example

A

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
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16
Q

introgression in Campylobacter

- associated with?

A

agriculture

  • consistent with scenario where expansion into a shared agricultural niche promotes de-speciation
17
Q

Agricultural C.coli have hybrid ancestry

A

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

18
Q

Introgression occurs across a great genetic distance

- amnio acid differences per gene

A

C. jejuni to C. coli
= 38

Within C.jejuni = 5.5

Human to chimp = 2.9

19
Q

Introgression might aid adaptation to novel enviros BUT might be disruptive

A

Sex beneficial

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

Sex is a barrier

  • recombination breaks gene networks
  • > less well adapted
20
Q

Introgression might aid adaptation to novel enviros

- example

A

Rieseberg et al (2003)

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

21
Q

chromosome painting

- what is it?

A

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

22
Q

chromosome painting

- purpose

A

quantities gene flow

identifies regions of different ancestry in the genome

23
Q

identifying donor clonal complexes

  • how?
  • example
A

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

24
Q

epistasis

co-adaptation

A

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

25
Q

modelling co-adaptation

A

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