BG25

Question 1

where in the world can mimicry be seen

Answer 1

africa
asia
south america

Question 2

Contempories who discovered mimcry

Answer 2

Henry Bates - credited with dicovery mimcry in amazon

Alfred wallace - found P. polytes female mimics in indonesia, noted differnet forms: cyrus, stickus, romulus

Question 3

Papilo dardanus

Answer 3

roland trimen SA
- ‘the most interesting butterfly int he world’
highly polymorphic, diff patterns in males and females
- has atleast 13 forms mimicking different toxic butterflies in different regions
- difference between morphs also controlled by a super gene but not dsx
- suggests mimicry evolved independently in genus atleast twice.

Question 4

evolution of distastefulness and colouration in butterflies

Answer 4

• plants evovle distasteful chemicals (alkaloid, cyanogenic glycosides) to prevent being eaten, some caterpillars store the compounds which are maintained in butterfly
• butterflies have evovled bright colour to warn birds they are distasetful
  = aposematic colouration
• birds have learnt not to prey on certain morphs: mimicry provides protection.

Question 5

two kinds of mimcry

Answer 5

Batesian: non-toxic mimis toxic = free rider
mullarian: toxic mimics toxic - establishes toxic morph - helps both species.

Question 6

heliconus speciation and species

Answer 6

complex mimicry

• 40 spp northern South america, but each species has up to40 diff geographic forms
• • speciation occured rapidly 10mya probs due to shift in techtonic plate

Question 7

heliconus adaptations

Answer 7

1. long lvied, low fecundity, coop breeding.
2. large eyes and stilt legs - allow egg laying in host passion flower plants
3. long wings = powerful flight
4. highly intelligent - avoid scientists nets
5. larval resistance to alkaloids, cyanogenic glycosides from hsot plant which they store
6. spectacular colouration
7. series of geographical races mimicking butterflies belonging to genus melinea

Question 8

heliconus mimcry ring

Answer 8

predicted that butterflies would converge on one same colour
but heliconus butterflies are diverse and form mimcy rings within geographical areas
- adaptive pressure to be similar to local morph to avoid predation

Question 9

evolution of wing colour in heliconus

• genetic study

Answer 9

clearly complex genetic basis as many distinct features involved
- but can do simple mendalian genetics via crosses

*studied genetics of H. numata, H. melpomene and H. erato
= morphs differ within degree red pigment, black background and white spots.

Question 10

genetics of H. melpomene colouration

Answer 10

• N-yb-sb supergene: controls white element
• B locus: controls red
• Ac locus: controls yellow patch on forewing

Question 11

genetics of H. erato colouration

Answer 11

Cr locus: controls white element

D locus: controls red element

Question 12

genetics of H. numata colouration

Answer 12

Locus P supergene: controls everything, 9 known alelles.

Question 13

basis for homology of colouration in heliconus

Answer 13

Can show different chromosomes in different species are homologous in particular regions by finding markers in diff species.
and show loci map to comparable position in different species

Question 14

homology for colouration of different species of heliconus

Answer 14

N-YB-SB locus is homologous to P locus and Cr locus

all homologous to carbonaria locus

Question 15

White element P locus

H. numata

Answer 15

cloned with aid of SNP markers

• found groups with high association
• area = an inversion, so has low recombination within area.
• 8 genes located in 400kb but as no recombination hard to know what is controlling the white element.

Question 16

D locus H. erato

Answer 16

crossing different morphs of h. erato using snps shows D locus maps to a particular region
indep of white locu
- found one gene optix a homeobox TF homologous to D locus

Question 17

Optix of H. erato

Answer 17

• is sequence in different morph - sequence is identical
• optix expression in imaginal disc differs and is correlated with extent of red pigmentation
• causal mutation is a cis acting reg element

Question 18

optix ancestral function

Answer 18

in V. cardui unrelated butterfly optix appears to be expressed in association with scales
- potentially this is the ancestral function and it has been co-opted for red pigmentation

Question 19

where do mimics get coloru

Answer 19

independent evo of introgression from hybridisation

- distinguish between two possibilites can use ABBA, BABA test.

Question 20

ABBA BABA assumptions

Answer 20

refers to distribution of SNP aleles in pigmentationa rea

• 4 closely related species, 3 closely related and 1 otugroup
• aleles are polymorphic in related species but outgroup is fixed in one state (A)

Question 21

Assumption for independent evolution ABBA BABA

Answer 21

• if alelle B arose indep we should sometimes get ABBA, or BABA pattern
• if this is true we should expect that the freq of SNPs that show ABBA pattern = the frequency of SNPs that show the BABA pattern - as evolved independently.

Question 22

assumption for introgression ABBA BABA

Answer 22

more SNPS with either the ABBA or BABA pattern it tells us the morphs share a chunk of DNA more closely related to each other than rest of genome.

Question 23

results from abba baba on heliconus

Answer 23

most the genome shows ABBA- BABA type polymorphism which demonstrates indep evo (no introgression)

• however around the bd locu ABBA /=/ BABA.
• strong inequality around C18 = introgression event
• • mirrored in phylogenies, regions flanking bd show species phylogeny, bd phylogeny shows differnet species more closely related.

Question 24

Wallaces mimcry

Answer 24

only female morphs mimic local unrelated butterflies across asia

Question 25

polytes mimics

Answer 25

*batesian mimicry

o P. polytes polytes morph mimics Pachlipota aristolochiae
o P. polytes theseus morph mimics P. aristolochiae (the black form).
o P. polytes romulus morph mimic P. aristlochiae (red form).
o P. polytes cyrus morph in non-mimetic, females resemble males.

Question 26

Female mimcry morph locus of polytes

Answer 26

• fine mapping using SNPs showed female mimicry morph locus is one gene.
• could be predicted as mimcry would only be affective when all morphological aspects are linked

Question 27

female morph mimicry gene homolog

Answer 27

homologous to double sex gene in drosophila
which is alternatively spliced
males: 1,2,3,5,6 exons
females: 1,2,3,4 exons

• results in functionally different proteins.
• dsx = zinc finger tf and can control a whole range of downstream differences between sexes.

Question 28

differences between dsx and butterlfy homolog

Answer 28

butterfly is more complicated and comes in several different isoforms - not just two seen in drosophila
- some isoforms are only expressed in mimic females tells us dsx has been co-opted for mimcry gene with the evo of new isoforms

Question 29

mutations responsible for variation among polytes morphs

Answer 29

sequence dsx in various morths
- two of the exons especially exon 1 are rich in NS subs fixed between mimetic and non-mimetic butterflies
= differences in coding seqs cause differences in morphs

Question 30

dsx structure

Answer 30

held together by an inversion so there is little recombination within the gen
= super gene
therefore different substiutions that occur in any given seq can control a whole variety of downstream aspects of morphology being dissociated

Question 31

Scenario for evo of dsx in P. polytes

Answer 31

1. isoform of ancestral sex determination gene evolves that is only expressed in females and controls subtle differences in pigmentation
2. mutation in coding region causs females to mimic locals
3. additioanl mutations in same chromosomes further increase freq and refine
4. inversion arises preventing dissociation - linkage, preventing recombination between distinct morph
5. mimics other species that get different dsx mutations in diff locations