Reproductive and competitive interactions among gametophytes of the allotetraploid fern Dryopteris corleyi and its two diploid parents.
OBJECTIVE
Several models predict that the establishment of polyploids within diploid populations is enhanced by non-random mating (i.e. selfing and assortative mating) of cytotypes and by a higher relative fitness of polyploids. This report assesses the role that antheridiogens (i.e. maleness-inducing pheromones) and intercytotype differences in growth rate have on polyploid performance.


METHODS
Three buckler-fern species were studied: the allotetraploid Dryopteris corleyi and its diploid parents, D. aemula and D. oreades. In one experiment, gametophytes of these species were cultured under rich growth conditions to compare the timing of gametangia production. The substrata on which these gametophytes had grown were used as antheridiogen sources in a second experiment. The three species were combined as source and target of antheridiogen (i.e. nine species pairs). Timing of antheridia production and gametophyte size were determined after those antheridiogen treatments.


RESULTS
Under rich growth conditions the allotetraploid produced archegonia earlier than those of diploid parents. Female gametophytes of the three species produced antheridiogens that inhibited growth and favoured maleness both within and among species. Gametophyte size was similar in the three species but antheridia formed earlier in the allotetraploid.


CONCLUSIONS
Unisexuality, promoted by non-specific antheridiogens, enhances random mating both within and among species. The resulting hybridization can favour the reproductive exclusion of the allopolyploid in sites where it is outnumbered by diploids. However, the earlier production of gametangia in the allotetraploid favours assortative mating and may thus counterbalance reproductive exclusion.
Departamento de Biología y Geología, ESCET, Universidad Rey Juan Carlos, 28933 Móstoles, Spain. ares.jimenez@urjc.es
Ares
A
Jiménez
Luis G
LG
Quintanilla
Santiago
S
Pajarón
Emilia
E
Pangua
D000704:Analysis of Variance; D004171:Diploidy; D032492:Dryopteris / Q000235:genetics / Q000254:growth & development* / Q000502:physiology*; D005854:Germ Cells / Q000254:growth & development* / Q000502:physiology; D006824:Hybridization, Genetic; D010675:Pheromones / Q000502:physiology; D011123:Polyploidy; D012098:Reproduction; D013170:Spores / Q000502:physiology
D010675:Pheromones