Studies in Natural Hybridization in the Genus Weisia

Khanna, K. R.

doi:10.1639/0007-2745(1960)63[1:sinhit]2.0.co;2

Cited by 19 publications

(8 citation statements)

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“…We have demonstrated that allopolyploidy occurs in bryophytes. This important mode of speciation in other land plants has only rarely been mentioned (25,26) and never documented with evidence in mosses or liverworts (3)(4)(5) (18)(19)(20). This implies that gene flow from progenitor species into derivative allopolyploid gene pools is possible over long time spans.…”

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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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confidence: 99%

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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“…A study by Khanna (1960) demonstrated the hybrid nature of a species of Weissia in India. The parents were the cleistocarpus Weissia (Astomum) crispa (Hedw.)…”

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A Natural Hybrid between Weissia and Astomum and Notes on the Nomenclature of the North American Species of Astomum

Reese¹,

Lemmon²

1965

The Bryologist

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“…1Jiridul4 shows n = 13, W. crispa also bas n, = 13 ·but some members of :the rpopulation showed n•=.14 (13 + m), W. exsert.a i·s diploid and shows rn.·= 26. These are descriobed in detail else!Where (KHANNA, 1960a).…”

Section: Gymno8tomum Recurvirostrwm Hedwmentioning

confidence: 99%