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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 experimental tests and molecular markers

Author: Carine Brouat

Journal: The Netherlands Entomological Society

SongZhao

Department of Entomology, SCAU


科 族 属 亚属 种 亚种

Carabidae

Who are Carabus?

Carabini

Carabus

Chrysocarabus

auronitens

punctatoauratus

splendens


Carabus (coptolabrus) ignimetallus 亚属 种 亚种Bates,1888


Carabus 亚属 种 亚种(Zasiocoptolabrus)sunwukongImura,1993


Carabus 亚属 种 亚种(Apotomopterus)toulgoeti Deuve,1989


Carabus 亚属 种 亚种(Isiocarabus)miaorum Lassalle et Peunies,1993


Carabus 亚属 种 亚种 (coptolabrus) lafossei Feisthame,1845


Carabus 亚属 种 亚种 (coptolabrus) lafossei Feisthame,1845


Carabus (Apotomopterus 亚属 种 亚种) davidis Deyrolle et Fairmaire, 1878


Carabus chrysocarabus punctatoauratus germar
Carabus (Chrysocarabus) punctatoauratus 亚属 种 亚种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 亚属 种 亚种 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


What is Haldane’s rule? 亚属 种 亚种

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

1922


Evolution, Species, Problem 亚属 种 亚种

  • 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?


Why they are choiced? 亚属 种 亚种

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

  • They are in sympatry

  • ?


What questions we try to answer? 亚属 种 亚种

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

  • Is there a preferential hybridization direction?

  • Are hybrid individuals viable and fertile?


Sampling and Conditions 亚属 种 亚种

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

  • Experimental conditions:

    pairs: boxes (12×12×6.5 cm) with 2 cm soil .slugs and apple.

    eggs: boxes(2×2×2×2cm) 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 ℃)


Obtaining virgin parents 亚属 种 亚种

C. punctatoauratus×C. punctatoauratus

C. punctatoauratus×C. splendens

8 mating pairs

20 mating pairs

PP

ps

C. splendens×C. splendens

C. splendens×C. punctatoauratus

10 mating pairs

10 mating pairs

ss

sp


How to assess the paternity of progeny? 亚属 种 亚种

  • 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)


Mating of inter- and intraspecific crosses 亚属 种 亚种

F1(PP×SS, 10 pairs; SS×PP, 10 pairs)

F2(SP×SP, 8 pairs PS×PS, 8 pairs)

ppss

sspp

spsp

psps

Backcrosses(F1 hybrids to the parent species)

(PP×PS, 8 pairs; SS×SP, 9 pairs; PS×SS, 10 pairs; SP×PP, 6 pairs)

ppps

sssp

psss

sppp

Pure C. Splendens (SS×SS, 8 pairs)

Pure C. Punctatoauratus (SS×SS,8pairs)

ssss

?


Mating of inter- and intraspecific crosses 亚属 种 亚种

X=42

ppss

sspp

spsp

psps

pssp

sssp

psss

pppp?

sppp

ssss

ppps

ppsp

pspp

ssps

spss

spps


Result 亚属 种 亚种

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.


Extra-pair fertilization for the first cross-experiment 亚属 种 亚种

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)


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.


Why only offspring than SP crossesC. 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


Why only offspring than SP crossesC. 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


Second cross-experiments offspring than SP crosses

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


Development time offspring than SP crosses

  • Fertility estimates for the different types of crosses

  • Wald X2 tests or Tukey test, P<0.05


Discussion offspring than SP crosses

  • 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).


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.


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


Why number of F1 hybrids is so low in natural populations conditions?

  • 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


Why number of F1 hybrids is so low in natural populations conditions?

  • Dissection of genitalia showed no sclerotized segment

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


Why number of F1 hybrids is so low in natural populations conditions?

  • 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


Why number of F1 hybrids is so low in natural populations conditions?

  • Specific attraction mechanisms exist: highly specific mate choice(second 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


Conclusion conditions

  • 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



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