BACKGROUND AND AIMS: In ferns, apomixis is an important mode of asexual reproduction. Although the mechanisms of fern reproduction have been studied thoroughly, most previous work has focused on cases in which ferns reproduce either exclusively sexually or exclusively asexually. Reproduction of ferns with potentially mixed systems and inheritance of apomixis remains largely unknown. This study addresses reproduction of the pentaploid Dryopteris × critica, a hybrid of triploid apomictic D. borreri and tetraploid sexual D. filix-mas. METHODS: Spore size, abortion percentage and number of spores per sporangium were examined in pentaploid plants of D. × critica grown in an experimental garden. The sporangial content of leaf segments was cultivated on an agar medium, and DNA ploidy levels were estimated by DAPI flow cytometry in 259 gametophytes or sporophytes arising from the F2 generation of the pentaploid hybrid. KEY RESULTS: The hybrid is partly fertile (89-94% of aborted spores) and shows unstable sporogenesis with sexual and apomictic reproduction combined. The number of spores per sporangium varied from approx. 31 to 64. Within a single sporangium it was possible to detect formation of either only aborted spores or various mixtures of aborted and well-developed reduced spores and unreduced diplospores. The spores germinated in viable gametophytes with two ploidy levels: pentaploid (5x, from unreduced spores) and half of that (approx. 2·5x, from reduced spores). Moreover, 2-15% of gametophytes (both 2·5x and 5x) formed a viable sporophyte of the same ploidy level due to apogamy. CONCLUSIONS: This study documents the mixed reproductive mode of a hybrid between apomictic and sexual ferns. Both sexual reduced and apomictic unreduced spores can be produced by a single individual, and even within a single sporangium. Both types of spores give rise to viable F2 generation gametophytes and sporophytes.

Department of Botany Faculty of Science University of South Bohemia Branišovská 1760 CZ 370 05 České Budějovice Czech Republic

Zobrazit více v PubMed

Barrington DS, Haufler HC, Werth CR. 1989. Hybridization, reticulation, and species concepts in the ferns. American Fern Journal 79: 55–64.

Bär A, Eschelmüller A. 2010. Farnstudien: Einige pentaploide Bastarde von

Benaglia T, Chauveau D, Hunter DR, Young D. 2009. Mixtools: an R package for analyzing finite mixture models. Journal of Statistical Software 32: 1–29.

Braithwaite AF. 1964. A new type of apogamy in ferns. New Phytologist 63: 293–305.

Chao YS, Liu HY, Ching YC, Chiou WL. 2012. Polyploidy and speciation in

Doležel J, Sgorbati S, Lucretti S. 1992. Comparison of three DNA fluorochromes for flow cytometric estimation of nuclear DNA content in plants. Physiologia Plantarum 85: 625–631.

Doležel J, Greilhuber J, Suda J. 2007. Estimation of nuclear DNA content in plants using flow cytometry. Nature Protocols 2: 2233–2244. PubMed

Döpp W. 1939. Cytologische und genetische Untersuchungen innerhalb der Gattung

Döpp W. 1955. Experimentell erzeugte Bastarde zwischen

Dyer RJ, Savolainen V, Schneider H. 2012. Apomixis and reticulate evolution in the PubMed PMC

Dyer RJ, Pellicer J, Savolainen V, Leitch IJ, Schneider H. 2013. Genome size expansion and the relationship between nuclear DNA content and spore size in the PubMed PMC

Eschelmüller A. 1998. Keimversuche mit Sporen der triploiden Sippen von

Ekrt L, Trávníček P, Jarolímová V, Vít P, Urfus T. 2009. Genome size and morphology of the

Ekrt L, Holubová R, Trávníček P, Suda J. 2010. Species boundaries and frequency of hybridization in the PubMed

Fraser-Jenkins CR. 2007. The species and subspecies in the

Gabriel y Galán JM, Prada C. 2011. Pteridophyte spores viability. In: Fernandéz H, Kumar A, Revilla MA, eds. Working with ferns: issues and applications. London: Springer, 193–205.

Gastony GJ, Haufler CH. 1976. Chromosome numbers and apomixis in the fern genus

Gastony GJ, Windham MD. 1989. Species concepts in pteridophytes: the treatment and definition of agamosporous species. American Fern Journal 79: 65–77.

Grusz AL, Windham MD, Pryer KM. 2009. Deciphering the origins of apomictic polyploids in the PubMed

Hickok LG, Klekowski EJ. 1973. Abnormal reductional and nonreductional meiosis in

Huang YM, Hsu SY, Hsieh TH, Chou HM, Chiou WL. 2011. Three

Hunt HV, Ansell SW, Russell SJ, Schneider H, Vogel JC. 2011. Dynamics of polyploid formation and establishment in the allotetraploid rock fern PubMed PMC

Ishikawa H, Ito M, Watano Y, Kurita S. 2003. Electrophoretic evidence for homologous chromosome pairing in the apogamous fern species PubMed

Krahulcová A, Rotreklová O, Krahulec F. 2013. The detection, rate and manifestation of residual sexuality in apomictic population of

Lin SJ, Kato M, Iwatsuki K. 1992. Diploid and triploid offspring of triploid agamosporous fern

Liu HM, Dyer RJ, Guo ZY, Meng Z, Li JH, Schneider H. 2012. The evolutionary dynamics of apomixis in ferns: a case study from polystichoid ferns. Journal of Botany 2012: 1–11, doi:10.1155/2012/510478.

Lovis JD. 1977. Evolutionary patterns and processes in ferns. Advances in Botanical Research 4: 229–415.

Manton I. 1950. Problems of cytology and evolution in the Pteridophyta. Cambridge: Cambridge University Press.

Nakato N, Ootsuki R, Murakami N, Masuyama S. 2012. Two types of partial fertility in a diploid population of the fern PubMed

Ootsuki R, Sato H, Nakato N, Murakami N. 2012. Evidence of genetic segregation in the apogamous fern species PubMed

Ozias-Akins P. 2006. Apomixis: developmental characteristics and genetics. Critical Reviews in Plant Sciences 25: 199–214.

Park C, Kato M. 2003. Apomixis in the interspecific triploid hybrid fern PubMed

Pinter I. 1995. Progeny studies of the fern hybrid

Quintanilla LG, Escudero A. 2006. Spore fitness components do not differ between diploid and allotetraploid species of PubMed PMC

R Development Core Team

Rabe EW, Haufler CH. 1992. Incipient polyploid speciation in the maidenhair fern (

Regalado Gabancho L, Prada C, Gabriel y Galán JM. 2010. Sexuality and apogamy in the Cuban

Reichstein T. 1981. Hybrids in European Aspleniaceae (Pteridophyta). Botanica Helvetica 91: 89–139.

Schneller J. 1975. Untersuchungen an einheimischen Farnen, insbesondere der Dryopteris

Schneller J, Krattinger K. 2010. Genetic composition of Swiss and Austrian members of the apogamous

Stanier RY, Kuniswawa R, Mandel R. 1971. Purification and properties of unicellular blue-green algae (Order Chroococcales). Bacteriological Review 35: 171–205. PubMed PMC

Vida G, Reichstein T. 1975. Taxonomic problems in the fern genus

Wagner WH, Chen KL. 1965. Abortion of spores and sporangia as a tool in the detection of

Walker TG. 1962. Cytology and evolution in the fern genus

Walker TG. 1979. The cytogenetics of ferns. In: Dyer AF, ed. The experimental biology of ferns. London: Academic Press, 87–132.

Walker TG. 1984. Chromosomes and evolution in pteridophytes. In: Sharma AK, Sharma A, eds. Chromosomes in evolution of eukaryotic groups, vol. 2 Boca Raton, FL: CRC Press, 103–141.

Windham MD, Yatskievych G. 2003. Chromosome studies of cheilanthoid ferns (Pteridaceae: Cheilanthoideae) from the western United States and Mexico. American Journal of Botany 90: 1788–1800. PubMed

Yatabe Y, Yamamota K, Tsutsumi C, Shinohara W, Murakami N, Kato M. 2011. Fertility and precocity of PubMed

Zhang R, Liu T, Wu W, et al. 2013. Molecular evidence for natural hybridization in the mangrove fern genus PubMed PMC

Interploidy gene flow via a 'pentaploid bridge' and ploidy reduction in Cystopteris fragilis fern complex (Cystopteridaceae: Polypodiales)

An experimental assessment of competitive interactions between sexual and apomictic fern gametophytes using Easy Leaf Area

Insights into the evolutionary history and widespread occurrence of antheridiogen systems in ferns

Widespread co-occurrence of multiple ploidy levels in fragile ferns (Cystopteris fragilis complex; Cystopteridaceae) probably stems from similar ecology of cytotypes, their efficient dispersal and inter-ploidy hybridization