Absence of a prezygotic behavioural barrier to gene flow between the two sympatric morphs of the squat lobster Munida gregaria (Fabricius, 1793) (Decapoda: Anomura: Galatheidae)

PÉREZ-BARROS, PATRICIA; CALCAGNO, JA; LOVRICH, GA

HELGOLAND MARINE RESEARCH

SPRINGER

Año: 2011 vol. 64 p. 513 - 523

1438-387X

Munida gregaria and M. subrugosa have beenconsidered two different species for more than a century;however, after a recent molecular phylogenetic study, theyare considered a single polymorphic species. Yet, the useof markers to diagnose species may be misleading whendivergence between species is recent, since a speciationevent may be obscured by the retention and stochasticsorting of ancestral polymorphisms. The morphs gregariaand subrugosa of Munida gregaria constitute an interestingcase for the study of behavioural isolation since they aresympatric, breed at the same time of the year, and mighthave experienced a recent speciation. Mating behaviourobservations and mate choice mating trials were conductedin order to investigate the potential existence of a behaviouralprezygotic barrier to gene flow between these twomorphs. Since factors involved in mate choice in galatheidsare unknown, the four possible combinations of the twodifferent morphs in trios were used to test for the existenceof mate choice. Video recordings of all the possible triocombinations revealed that there was cross-attractionbetween males and females of different morphs. Femalesbearing partial broods participated in encounters as well asnon-ovigerous females. The frequency and duration ofhomo- and heterotypic encounters were registered, and areproductive isolation index was calculated for each variablefor each trio. The isolation indexes calculated were notdifferent from zero indicating random mating, and were notaffected by the composition of the trio or the partial ovigerouscondition of females. These results provided evidence of theabsence of behavioural prezygotic barriers to gene flowbetween the morphs gregaria and subrugosa of M. gregaria.