AOBPreview originally published online on July 15, 2006
Annals of Botany 2006 98(3):609-618; doi:10.1093/aob/mcl137
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Spore Fitness Components Do Not Differ Between Diploid and Allotetraploid Species of Dryopteris (Dryopteridaceae)
Department of Natural Sciences and Applied Physics, University Rey Juan Carlos, Tulipán s/n, Móstoles, E-28933, Spain
* For correspondence. E-mail luis.quintanilla{at}urjc.es
Received: 21 November 2005 Returned for revision: 13 April 2006 Accepted: 20 May 2006 Published electronically: 15 July 2006
• Background and Aims Although allopolyploidy is a prevalent speciation mechanism in plants, its adaptive consequences are poorly understood. In addition, the effects of allopolyploidy per se (i.e. hybridization and chromosome doubling) can be confounded with those of subsequent evolutionary divergence between allopolyploids and related diploids. This report assesses whether fern species with the same ploidy level or the same altitudinal distribution have similar germination responses to temperature. The effects of polyploidy on spore abortion and spore size are also investigated, since both traits may have adaptive consequences.
• Methods Three allotetraploid (Dryopteris corleyi, D. filix-mas and D. guanchica) and three related diploid taxa (D. aemula, D. affinis ssp. affinis and D. oreades) were studied. Spores were collected from 24 populations in northern Spain. Four spore traits were determined: abortion percentage, size, germination time and germination percentage. Six incubation temperatures were tested: 8, 15, 20, 25 and 32 °C, and alternating 8/15 °C.
• Key Results Allotetraploids had bigger spores than diploid progenitors, whereas spore abortion percentages were generally similar. Germination times decreased with increasing temperatures in a wide range of temperatures (8–25 °C), although final germination percentages were similar among species irrespective of their ploidy level. Only at low temperature (8 °C) did two allotetraploid species reach higher germination percentages than diploid parents. Allotetraploids showed faster germination rates, which would probably give them a competitive advantage over diploid parents. Germination behaviour was not correlated with altitudinal distribution of species.
• Conclusions The results of this study suggest that (i) relative fitness of allopolyploids at sporogenesis does not differ from that of diploid parents and (ii) neither does allopolyploidization involve a change in the success of spore germination.
Key words: Allopolyploidy, Dryopteris, fitness component, northern Spain, spore abortion, spore germination, temperature
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  A. Jimenez, L. G. Quintanilla, S. Pajaron, and E. Pangua Reproductive and Competitive Interactions Among Gametophytes of the Allotetraploid Fern Dryopteris corleyi and its Two Diploid Parents Ann. Bot., September 1, 2008; 102(3): 353 - 359. [Abstract] [Full Text] [PDF]
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