Eric F. Karlin

One haploid parent contributes 100% of the gene pool for a widespread species in northwest North America.

The monoicous peatmoss Sphagnum subnitens has a tripartite distribution that includes disjunct population systems in Europe (including the Azores), northwestern North America and New Zealand. Regional genetic diversity was highest in European S. subnitens but in northwestern North America, a single microsatellite‐based multilocus haploid genotype was detected across 16 sites ranging from Coos County, Oregon, to Kavalga Island in the Western Aleutians (a distance of some 4115 km). Two multilocus haploid genotypes were detected across 14 sites on South Island, New Zealand. The microsatellite‐based regional genetic diversity detected in New Zealand and North American S. subnitens is the lowest reported for any Sphagnum. The low genetic diversity detected in both of these regions most likely resulted from a founder event associated with vegetative propagation and complete selfing, with one founding haploid plant in northwest North America and two in New Zealand. Thus, one plant appears to have contributed 100% of the gene pool for the population systems of S. subnitens occurring in northwest North America, and this is arguably the most genetically uniform group of plants having a widespread distribution yet detected. Although having a distribution spanning 12.5° of latitude and 56° of longitude, there was no evidence of any genetic diversification in S. subnitens in northwest North America. No genetic structure was detected among the three regions, and it appears that European plants of S. subnitens provided the source for New Zealand and northwest North American populations.

Cytotype variation and allopolyploidy in North American species of the Sphagnum subsecundum complex (Sphagnaceae)

Allopolyploid speciation is likely the predominant mode of sympatric speciation in plants. The Sphagnum subsecundum complex includes six species in North America. Three have haploid gametophytes, and three are thought to have diploid gametophytes. Microsatellite analyses indicated that some plants of S. inundatum and S. lescurii are heterozygous at most loci, but others have only one allele at each locus. Flow cytometry and Feulgen staining showed that heterozygous plants have twice the genome size as plants with one allele per locus; thus, microsatellite patterns can be used to survey the distribution and abundance of haploid and diploid gametophytes. Microsatellite analyses also revealed that S. carolinianum is consistently diploid, but S. lescurii and S. inundatum include both haploid and diploid populations. The frequency of diploid plants in S. lescurii increases with latitude. In an analysis of one population of S. lescurii, both cytotypes co-occurred but were genetically differentiated with no evidence of interbreeding. The degree of genetic differentiation showed that the diploids were not derived from simple genome duplication of the local haploids. Heterozygosity appears to be fixed or nearly so in diploids, strongly suggesting that although morphologically indistinguishable from the haploids, they are derived by allopolyploidy.

Three‐genome mosses: complex double allopolyploid origins for triploid gametophytes in Sphagnum

This paper documents the occurrence of allotriploidy (having three differentiated genomes) in gametophytes of two Southern Hemisphere Sphagnum species (S. australe, S. falcatulum). The pattern of microsatellite alleles indicates that both species are composed of a complex of allodiploid and allotriploid gametophytes, with the latter resulting from two allopolyploidization events. No haploid (n = x) gametophytes were found for either species. The ploidal levels suggested by the pattern of microsatellite alleles were confirmed by flow cytometry and Feulgen DNA image densitometry. For both S. australe and S. falcatulum, the respective allodiploid plants (or their ancestors) are one of the parent species of the allotriploid plants. This is the first report of triploidy in Sphagnum gametophytes occurring in nature and also the first report of the presence of three differentiated genomes in any bryophyte. It is also the first report of intersectional allopolyploidy in Sphagnum, with S. australe appearing to have parental species from Sphagnum sections Rigida and Sphagnum, and S. falcatulum having parental species from Sphagnum sections Cuspidata and Subsecunda. In both species, the allotriploid cytotypes were the most prevalent cytotype on the South Island of New Zealand. The pattern of microsatellite alleles shows the presence of two genetically distinct populations of allodiploid S. australe, possibly indicating multiple origins of polyploidy for that allodiploid cytotype. Morphological evidence is also highly indicative of recurrent polyploidy in the allotriploid cytotype of S. falcatulum. Allopolyploidy has clearly played a major evolutionary role in these two Southern Hemisphere taxa. This study, in conjunction with other recent research, indicates that allopolyploidy is a common, if not the predominant, form of polyploidy in Sphagnum.

High genetic diversity in a remote island population system: sans sex

It has been proposed that long-distance dispersal of mosses to the Hawaiian Islands rarely occurs and that the Hawaiian population of the allopolyploid peat moss Sphagnum palustre probably resulted from a single dispersal event. Here, we used microsatellites to investigate whether the Hawaiian population of the dioicous S. palustre had a single founder and to compare its genetic diversity to that found in populations of S. palustre in other regions. The genetic diversity of the Hawaiian population is comparable to that of larger population systems. Several lines of evidence, including a lack of sporophytes and an apparently restricted natural distribution, suggest that sexual reproduction is absent in the Hawaiian plants. In addition, all samples of Hawaiian S. palustre share a genetic trait rare in other populations. Time to most recent ancestor (TMRCA) analysis indicates that the Hawaiian population was probably founded 49-51 kyr ago. It appears that all Hawaiian plants of S. palustre descend from a single founder via vegetative propagation. The long-term viability of this clonal population coupled with the development of significant genetic diversity suggests that vegetative propagation in a moss does not necessarily preclude evolutionary success in the long term.

Systematics of Sphagnum section Sphagnum in New Zealand: A microsatellite‐based analysis

Abstract The systematics of Sphagnum section Sphagnum in New Zealand has been controversial. Two species are currently recognised in the New Zealand flora, S. cristatum and S. perichaetiale, but the presence of the widespread S. magellanicum has been debated. An analysis of 16 microsatellite loci shows that the gametophytes of Sphagnum perichaetiale appear to have one monoploid set of chromosomes (i.e., are haploid). Fixed heterozygosity at 10 loci indicates that S. cristatum is an alloploid. A red morphotype of S. cristatum, similar in macroappearance to S. magellanicum, is not genetically differentiated from the more common brown‐green morphotypes of S. cristatum. Although analysis of the microsatellite data for S. cristatum showed most of the genetic variation to be within populations, significant variation did occur among populations within regions and also between regions.

Microsatellite analysis of Sphagnum centrale, S. henryense, and S. palustre (Sphagnaceae)

Abstract This study provides the first report that Sphagnum centrale and S. henryense are allopolyploids. Microsatellites show S. henryense and S. palustre to be conspecific. In contrast, they show S. centrale to be genetically distinct from S. palustre s.l. In addition to differences in alleles and allele frequencies, the patterns of observed heterozygosity across 17 microsatellite markers also differed between S. centrale and S. palustre s.l. This represents a dimension of genetic differentiation that is not detected or addressed by statistical approaches such as AMOVA or Principal Coordinates Analysis. The patterns of microsatellites further provide preliminary evidence suggesting that S. centrale and S. palustre have one parental taxon in common and differ in the second.

The Peat Moss Sphagnum cuspidatum in Australia: Microsatellites Provide a Global Perspective

Abstract The distribution of Sphagnum cuspidatum has been subject to controversy. Although historically reported from all continents except Antarctica recent authors consider S. cuspidatum to be endemic to Europe and eastern North America. Microsatellites from Australian plants morphologically identified as S. cuspidatum were compared to microsatellites of plants morphologically identified as S. cuspidatum collected from other regions. The species was found to occur in Australia as well as on every continent except Antarctica. The sample most closely related to the Australian plants was collected in the Philippines, and samples from Australia, the Philippines, Colombia, and Equatorial Guinea formed a subclade within S. cuspidatum. Microsatellites further show that S. cuspidatum is one of the parental species of the double allopolyploid S. falcatulum, a Holantarctic species which is reported from Tasmania, New Zealand, and Chile.

The double allopolyploid Sphagnum ×falcatulum (Sphagnaceae) in Tierra del Fuego, a Holantarctic perspective

Abstract A Holantarctic species, the inter-subgeneric allopolyploid Sphagnum ×falcatulum s.l. is a cryptic species complex composed of allodiploid and allotriploid cytotypes. The allotriploid plants are double allopolyploids (one of just two reported for bryophytes), with the allodiploid cytotype being one parent. Using a combination of microsatellites, nucleotide sequences, and morphological characters, allotriploid S. ×falcatulum is shown to be the most widespread Sphagnum species in the Holantarctic, with genetically documented populations in South America (Tierra del Fuego), New Zealand (South Island), and Australia (Macquarie Island, Tasmania). It is further concluded that six Sphagnum species described from the Tierra del Fuego Archipelago (TDF) of South America and a seventh described from South Island, New Zealand are synonymous with the allotriploid cytotype of S. ×falcatulum. The synonymized species include five named by Heikki Roivainen in 1937, S. ×ehyalinum, and S. subditivum. Allotriploid S. ×falcatulum is the predominant, perhaps the only, subgenus Cuspidata species present in TDF and immediate vicinity. The combination of low genetic diversity and an apparent absence of sexual reproduction indicate that the TDF population of the dioicous allotriploid S. ×falcatulum was likely founded by one or a limited number of individuals. The same is apparently the case for Macquarie I. and Tasmanian populations of allotriploid S. ×falcatulum. Several lines of evidence, including high genetic diversity, frequent sporophyte production, and the occurrence of the allodiploid parent, suggest that allotriploid S. ×falcatulum likely evolved in New Zealand.

Allopolyploidy in Sphagnum mendocinum and S. papillosum (Sphagnaceae)

Abstract This study provides the first report that Sphagnum mendocinum (Sphagnum section Cuspidata) and S. papillosum (Sphagnum section Sphagnum) are allopolyploids. Sphagnum mendocinum is an intersectional allopolyploid, with parental species from Sphagnum sections Cuspidata and Subsecunda. It is the third intersectional alloploid species reported for Sphagnum. The gametophytically allodiploid cytotype of S. papillosum was detected in Europe, North America, and Japan. It appears to be the predominant, if not the only, cytotype for this species. Our results may warrant re-examination of the report of a haploid (n  =  x) cytotype for S. papillosum.

The vegetation of the low-shrub bogs of northern New Jersey and adjacent New York ecosystems at their southern limit

LYNN, L. M. AND E. F. KARLIN (Div. Nat. Sci. and Math., Bergen Comm. Coll., Paramus, N.J. 07652 and Sch. of Theor. and Applied Science, Ramapo Coll. of NJ., Mahwah, N.J. 07430). The Vegetation of the northern low-shrub bogs of NewJersey and southeastern New York: Ecosystems at their southern limit. Bull. Torrey Bot. Club 112:436-444. 1985.-The vegetation of six lowshrub bogs located near the glacial boundary was quantified using phytosociological methods. Based on pH and Ca ion concentrations, these peatlands were all weakly minerotrophic to ombrotrophic systems. The dominant vascular species were Chamaedaphne calyculata, Decodon verticillatus, Kalmia angustifolia and Vaccinium corymbosum. A number of plant species which are characteristic of northern peatlands and which reach their southern distributional limit in the study region were absent from the low-shrub bogs studied, although Andromeda glaucophylla and Kalmia polifolia were present. Several species were also present in all of the study sites which are not usually found in low-shrub bogs located further north.