Electrophoretic Evidence of Reticulate Evolution in the Appalachian Asplenium Complex

Werth, Charles R.; Guttman, Sheldon I.; Eshbaugh, W. Hardy

doi:10.2307/2418344

Cited by 140 publications

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“…Analysis of gametophytic progeny demonstrates that these complex patterns are fixed and, therefore, have resulted from the allopolyploid amalgamation of the diploid genomes. Similarly, complex isozyme patterns have been found in other polyploid fern species (14,17).…”

Section: Resultssupporting

confidence: 54%

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Genetic evidence suggests that homosporous ferns with high chromosome numbers are diploid

Haufler

Soltis

1986

Proc. Natl. Acad. Sci. U.S.A.

136

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Homosporous ferns have usually been considered highly polyploid because they have high chromosome numbers (average n = 57.05). In angiosperms, species with chromosome numbers higher than n = 14 generally have more isozymes than those with lower numbers, consistent with their polyploidy. By extrapolation, homosporous ferns would be expected to have many isozymes. However, ongoing surveys indicate that within fern genera, species having the lowest chromosome numbers have the number of isozymes considered typical of diploid seed plants. Only species above these lowest numbers have additional isozymes. Therefore, homosporous ferns either have gone through repeated cycles of polyploidy and gene silencing or were initiated with relatively high chromosome numbers. The latter possibility represents a radical departure from currently advocated hypotheses of fern evolution and suggests that there may be fundamental differences between the genomes of homosporous ferns and those of higher plants. These hypotheses can be tested by genetic, karyological, and molecular techniques.

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Section: Resultssupporting

confidence: 54%

“…We found only a few instances of isozyme multiplicity. Phosphoglucomutase, for example, has a duplicated locus in Bommeria ehrenbergiana (14), Asplenium montanum (17), and Polypodium virginianum (16). Such occasional departures from diploid expression may be considered insignificant; they are also seen, for example, in diploid angiosperms.…”

Section: Resultsmentioning

confidence: 99%

Genetic evidence suggests that homosporous ferns with high chromosome numbers are diploid

Haufler

Soltis

1986

Proc. Natl. Acad. Sci. U.S.A.

136

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“…The other 9 included alleles present in only one of the two haploids, P. ellipticum or P. insigne, which therefore could be used as genetic markers to establish unequivocally the source of the alleles expressed by P. medium. When species are as well-differentiated as the haploid mosses considered here, their allopolyploid derivatives display fixed heterozygosity because of nonsegregation of nonhomologous chromosomes (18)(19)(20). Furthermore, when one or both of the progenitors is polymorphic, different fixed heterozygous genotypes of the allopolyploid may be produced.…”

Section: Resultsmentioning

confidence: 96%

Allopolyploidy in bryophytes: Multiple origins of Plagiomnium medium

Wyatt

Odrzykoski

Stoneburner

et al. 1988

Proc. Natl. Acad. Sci. U.S.A.

107

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Bryophytes are thought to be unique among land plants in lacking the important evolutionary process of allopolyploidy, which involves interspecific hybridization and chromosome doubling. Electrophoretic data show, however, that the polyploid moss Plagiomnium medium is an aflopolyploid derivative of Plagiomnium eUipticum and Plagiomnium insigne, that P. medium has originated more than once from these progenitors, and that cross-fertilization results in interlocus genetic recombination. Evidence from restriction fragment length polymorphisms in chloroplast DNA implicates P. insigne as the female parent in interspecific hybridizations with P. ellipticum. Contrary to prevailing views, it appears that those evolutionary processes responsible for genetic differentiation and speciation in other land plants occur in the bryophytes as well.It is estimated that 47% of all flowering plants and 95% of all pteridophytes are polyploids and that the majority of these are allopolyploids, which have arisen through doubling of chromosomes in interspecific hybrids (ref. 1, but see ref.2). Among the bryophytes 79% of mosses, 11% of liverworts, and 2% of hornworts are believed to be polyploids (3, 4). In contrast to other land plants, however, all of these have been assumed on the basis of morphology to be autopolyploids (5, 6). Furthermore, hybridization has been documented in only a few isolated cases involving sterile sporophytes from intergeneric crosses (3-6). The absence of hybrid speciation, an important mode of evolution in other land plants, has contributed to the characterization of bryophytes as a group with severely limited evolutionary potential (7,8).Within the moss genus Plagiomnium, section Rosulata includes one polyploid species (Plagiomnium medium; n = 12) and six haploid species (9). On the basis of morphology, Lowry (10) concluded that Plagiomnium ellipticum (n = 6) is the progenitor of autopolyploid P. medium. Koponen (9), however, stressed different characters and argued that Plagiomnium insigne (n = 6) is the only possible progenitor. Because the morphological evidence is ambiguous, we elected to use biochemical evidence to resolve the origin of P. medium. MATERIALS AND METHODSFour gametophytic populations each of P. medium and P. ellipticum were sampled in northern Michigan from many of the same localities sampled in Lowry's (9) original cytological study. Because Lowry's (9) chromosome counts were done on plants collected in Michigan [all vouchers verified by Wyatt (11)] and his and all other counts [reviewed by Koponen (12)] for these species are in agreement, we did not deem it necessary to examine our material cytologically. We also obtained population samples of P. insigne from northern California. From each population, we collected 36 moss clumps (approximately 5 x 5 cm). These were maintained in a growth chamber on a light/dark cycle of 16:8 hr at 15'C and 10'C, respectively. Single healthy shoots were subjected to horizontal starch gel electrophoresis after 1-2 months under these conditions. E...

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“…Following Hamrick & Godt (1990), we treated the loci polymorphic in at least one population as polymorphic at the species level. Genetic diversity of P. otomasui at the population and the species levels was compared with data compiled from studies examining allozyme diversity of diploid homosporous ferns (references cited in Soltis & Soltis, 1990a;Werth et al, 1985;Soltis & Soltis, 1987, Haufler et al, 1990Werth, 1991;Ranker, 1992aRanker, ,b, 1994Li & Haufler, 1994;Korpelainen & Kolkkala, 1996). At the species level, we compiled data from the studies examining two or more populations per species, and the population-level data also included those studies examining only one population per species.…”

Section: Discussionmentioning

confidence: 99%

High genetic variability revealed by allozymic loci in the narrow endemic fern Polystichum otomasui (Dryopteridaceae)

Maki

Asada

1998

Heredity

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Genetic variability was examined at 16 putative allozymic loci in the narrow endemic fern Polystichum otomasui. Although this species is distributed in only a few valleys within an approximately 10 km 6 km area on the Kyusyu Island of Japan, there are a relatively large number of individuals in this area. The percentage of polymorphic loci (P), the number of alleles per locus (A), the observed heterozygosity (H O ) and the expected heterozygosity (H E ) were 61.9, 1.93, 0.166 and 0.177, respectively, at the population level, and P, A and H E were 81.3, 2.69 and 0.199, respectively, at the species level, indicating that P. otomasui has extremely high allozymic variation for a fern species. The G ST value among the 10 populations examined within the range was 0.108, suggesting that the interpopulation gene flow is high enough to impede genetic structuring. The mating system estimates, Wright's fixation index and the intragametophytic selfing rate, indicate that the species is outcrossing. High genetic variability, in spite of narrowness of the distribution, may have resulted from a recent rapid decline in the population and/or the large effective population size resulting from the extensive gene flow among the populations.

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Electrophoretic Evidence of Reticulate Evolution in the Appalachian Asplenium Complex

Cited by 140 publications

References 0 publications

Genetic evidence suggests that homosporous ferns with high chromosome numbers are diploid

Genetic evidence suggests that homosporous ferns with high chromosome numbers are diploid

Allopolyploidy in bryophytes: Multiple origins of Plagiomnium medium

High genetic variability revealed by allozymic loci in the narrow endemic fern Polystichum otomasui (Dryopteridaceae)

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