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Haldane’s rule in Carabus : interspecific mating between Carabus punctatoauratus and Carabus splendens using expe PowerPoint PPT Presentation


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Haldane’s rule in Carabus : interspecific mating between Carabus punctatoauratus and Carabus splendens using experimental tests and molecular markers. Author: Carine Brouat. Journal: The Netherlands Entomological Society. SongZhao. Department of Entomology, SCAU.

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Haldane’s rule in Carabus : interspecific mating between Carabus punctatoauratus and Carabus splendens using expe

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Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Haldanes rule in Carabus: interspecific mating between Carabus punctatoauratus and Carabus splendens using experimental tests and molecular markers

Author: Carine Brouat

Journal: The Netherlands Entomological Society

SongZhao

Department of Entomology, SCAU


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Carabidae

Who are Carabus?

Carabini

Carabus

Chrysocarabus

auronitens

punctatoauratus

splendens


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Carabus (coptolabrus) ignimetallus Bates,1888


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Carabus (ZasiocoptolabrussunwukongImura,1993


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Carabus (Apotomopterustoulgoeti Deuve,1989


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Carabus (Isiocarabusmiaorum Lassalle et Peunies,1993


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Carabus (coptolabrus) lafossei Feisthame,1845


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Carabus (coptolabrus) lafossei Feisthame,1845


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Carabus (Apotomopterus davidis Deyrolle et Fairmaire, 1878


Carabus chrysocarabus punctatoauratus germar

Carabus (Chrysocarabus) punctatoauratus Germar

Elytral primary rows is sharp

Which are endemic to the Pyrenean

spring-breeders

predators of slugs and earthworms

they overwinter as adults


Carabus chrysocarabus splendens olivier 1790

Carabus (Chrysocarabus) splendens Olivier,1790

Elytral primary rows is absolescent; shape and colour of palpi and antennae

Which are endemic to the Pyrenean

spring-breeders

predators of slugs and earthworms

they overwinter as adults


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

What is Haldanes rule?

Haldane: the heterogametic sex (the male for carabids) is less fertile or has a reduced viability.

1922


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Evolution, Species, Problem

  • Natural hybridization can change the genetic diversity, population dynamics, and interactions between species

  • lead to adaptive evolution and evolutionary diversification

  • Species;

  • Reproductive barriers:microspatial or microtemporal allopatry

  • BUT what will happen about sympatric insect species when we relaxing some under controlled conditions?


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Why they are choiced?

  • The two species cluster in the same mitochondrial DNA clade showing that they are phylogenetically closely related.

  • They are in sympatry

  • ?


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

What questions we try to answer?

  • Does interspecific mating occur between C.splendens and C. punctatoauratus?

  • Is there a preferential hybridization direction?

  • Are hybrid individuals viable and fertile?


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Sampling and Conditions

  • Sampling: April 2001, the males and females were kept in separate boxes at 5

  • Experimental conditions:

    pairs: boxes (12126.5 cm) with 2 cm soil .slugs and apple.

    eggs: boxes(2222cm) with sterilized soil.

    larvae: cups (8.5 cm diameter and 11.5 cm high) with 7 cm soil, crushed slugs and apple

    adults: were reared individually for 21 days and then kept under winter conditions(5 )


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Obtaining virgin parents

C. punctatoauratusC. punctatoauratus

C. punctatoauratusC. splendens

8 mating pairs

20 mating pairs

PP

ps

C. splendensC. splendens

C. splendensC. punctatoauratus

10 mating pairs

10 mating pairs

ss

sp


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

How to assess the paternity of progeny?

  • Using four microsatellite loci :Cs2/10, Csol9/170, Cp4/63, and Cs1/134(how? beg)

  • The loci were sufficiently polymorphic to easily establish the paternity of any resulting offspring by simple exclusion

  • The extra-pair offspring were discarded (generalized linear models with Poisson,SAS)


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Mating of inter- and intraspecific crosses

F1(PPSS, 10 pairs; SSPP, 10 pairs)

F2(SPSP, 8 pairs PSPS, 8 pairs)

ppss

sspp

spsp

psps

Backcrosses(F1 hybrids to the parent species)

(PPPS, 8 pairs; SSSP, 9 pairs; PSSS, 10 pairs; SPPP, 6 pairs)

ppps

sssp

psss

sppp

Pure C. Splendens (SSSS, 8 pairs)

Pure C. Punctatoauratus (SSSS,8pairs)

ssss

?


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Mating of inter- and intraspecific crosses

X=42

ppss

sspp

spsp

psps

pssp

sssp

psss

pppp?

sppp

ssss

ppps

ppsp

pspp

ssps

spss

spps


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Result

All F1 and backcross hybrids from our experiments had the C. punctatoauratus pattern of sharp elytral primary rows. Thus, the morphological trait used to distinguish the two species displays dominance and using only this trait to detect hybrids in natural populations is therefore inappropriate.


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Extra-pair fertilization for the first cross-experiment

Three of these females

had a mixture of extra-pair offspring and offspring

from the male used in the laboratory

280 individuals (no

consider aboout

Extra-pair offspring)


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Why PP crosses had significantly fewer incompatible offspring than SP crosses

C. punctatoauratus females can preferentially choose the sperm they use to fertilize their eggs, favouring conspecific sperm.


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Why only C. punctatoauratus females produced progeny that did not originate from their experimental partner

  • some C. punctatoauratus females had been fertilized in the field before sampling, being able to store the sperm of their sexual partner for some weeks.

  • onset of the reproductive period may be later for C. splendens than for C. punctatoauratus


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Why only C. punctatoauratus females produced progeny that did not originate from their experimental partner

  • C. splendens females are unable to store sperm

  • Interspecific mating may exist but could be inefficient in the case of multiple mating due to sperm precedence favouring conspecific sperm


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Second cross-experiments

Mean number of eggs,larvae, and adult individuals produced per pair in each type of cross

  • proportion of fertile pairs

  • mean number of eggs per female

  • percentage of fertile eggs per female

  • mean number of larvae/adults

  • percentage of emerged adult per hatching larva


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Development time

  • Fertility estimates for the different types of crosses

  • Wald X2 tests or Tukey test, P<0.05


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Discussion

  • We produced 114 and 168 hybrid individuals in the first and second laboratory experiments,

  • The hybrids were viable but only females were fertile third question.

  • Introgression in nature between the two Carabus species can only proceed through females (first question).


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Why easy in controlled conditions but difficult in natural conditions

  • Counter-selection of hybrids under natural environmental conditions

  • hybrid male sterility was the only trait associated with post-zygotic counter selection of hybrids.


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Why easy in controlled conditions but difficult in natural conditions

  • But This alone cannot explain the low proportion of F1 individuals under natural conditions

  • Hybrid male sterility is an incomplete barrier because gene introgression between species can still occur through females by repeated backcrosses


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Why number of F1 hybrids is so low in natural populations

  • Copulation may be impossible if the male and female genitalia of the two species do not fit together well

  • Unsuccessful mating attempts would damage female genitalia


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Why number of F1 hybrids is so low in natural populations

  • Dissection of genitalia showed no sclerotized segment

  • No physical incompatibility in size or shape of the male and female genitalia between the two species.


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Why number of F1 hybrids is so low in natural populations

  • If copulation does occur, it is possible that heterospecific sperm may not be adequately transferred, implying a limited viability of stored sperm, or an increase in gametic mortality

  • no significant differences in the number of descendants between SSSS cross-types and certain interspecific crosses


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Why number of F1 hybrids is so low in natural populations

  • Specific attraction mechanisms exist: highly specific mate choicesecond question

  • C. punctatoauratus and C. splendens indicate highly specific mate choice in both species

  • differences in the seasonal or daily rhythms of the two species may prevent physical encounter and thus hybridization


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Conclusion

  • pre-zygotic barriers may be sufficiently high to prevent complete homogenization of genomes of C. splendens and C. punctatoauratus, despite the fact that hybrids can be easily obtained under controlled laboratory conditions


Haldane s rule in carabus interspecific mating between carabus punctatoauratus and carabus splendens using experimental tests and molecular markers

Thanks for your attention!


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