Localized hybridization betweenSaxifraga aizoides andS. mutata (Saxifragaceae): Reproductive ecology ofS. ×hausmannii and implications for conservation

The roles of hybridization and of introgression as potential threats to small native populations are current topics of interest both for evolutionary and conservation biologists. Two factors are mainly involved in the threat to natural populations through hybridization: demographic swamping and genetic assimilation. At prealpine locations, twoSaxifraga species with very different growth habits,S. aizoides andS. mutata, form a hybrid,S. ×hausmannii. Investigation of meiosis and crossing experiments revealed regular pairing of the 26 chromosomes and development of viable seeds in the hybrid. Analysis of hybrid indices, GPI allozymes, germination experiments and seed sizes showed an intermediate position ofS. ×hausmannii between its parental species.Saxifraga aizoides andS. mutata were separated by only weak hybridization barriers. Introgression occurred mostly in direction ofS. aizoides, although to a small amount. There is no actual threat to small, prealpine populations ofS. aizoides andS. mutata through interspecific gene flow because hybridization is localized, resulting from different flowering phenologies of the parental species and from the narrow habitat requirements ofS. ×hausmannii, which are similar to those ofS. aizoides. The major threat to local, prealpine populations ofS. aizoides andS. mutata is the loss of landscape dynamics. Both species need open erosion slopes for successful recruitment.     

Electrophoretic evidence for the origins of tetraploids and hybrids ofSphenomeris chinensis sensu lato (Lindsaeaceae) in Japan

Hypotheses for the origins of tetraploids and hybrids ofSphenomeris chinensis sensu lato in Japan were tested using electrophoretic analysis of isozymes. Comparison of banding patterns supported the hypothesis that plants having abortive spores had resulted following hybridization between diploidS. chinensis var.chinensis andS. biflora and between diploid var.chinensis andS. gracilis. Results from isozymic analyses also revealed thatS. intermedia probably originated through allotetraploid speciation following hybridization between var.chinensis andS. biflora. There were two electrophoretic variants among tetraploids ofS. chinensis. One variant, restricted to the southern Ryukyu Islands, is probably an allotetraploid of hybrid origin between diploidS. chinensis andS. gracilis. It has been described as a new species,S. yaeyamensis Lin, Kato & K. Iwatsuki. The other variant, morphologically corresponding to var.chinensis, is distributed at least throughout southern Japan and also in northern Thailand. Its origin is uncertain, but one of the parents is probably diploidS. chinensis. Sphenomeris intermedia andS. yaeyamensis occur inland, whereas the parentalS. biflora andS. gracilis are halophilous and rheophllous, respectively.     

Seed weight increases with altitude in the Swiss Alps between related species but not among populations of individual species

Seed weight is a crucial plant life history trait, determining establishment success and dispersal ability. Especially in stressful environments, larger seeds may be selected at the expense of seed number, because larger seeds have a better chance of giving rise to an established offspring. We tested the hypotheses that between related species-pairs and among populations of single species a similar trend for increasing seed weight with increasing altitude should be present. Firstly, we measured seed weights from 29 species-pairs, with one species occurring in lowland areas and a congeneric species from high altitudes. Seeds of the alpine species were 28±8% larger than seeds from lowland species (P<0.01). Compared to the related lowland species, 55% of the alpine species had heavier seeds, 3% (one species) had lighter, and 41% had seeds of approximately equal weight. Secondly, we compared seed weights among populations of four species from different habitats and with different life histories. Seeds from between 11 and 34 populations per species were sampled along altitudinal gradients of 800–1,500 m (ca. 800 m in Scabiosa lucida, ca. 1,000 m in Saxifraga oppositifolia, ca. 1,000 m in Epilobium fleischeri, and ca. 1,500 m in Carex flacca). In all the four species, we found no indication for heavier seeds at higher altitudes. Our results indicate a selection pressure for species with heavier seeds at higher altitude, but the trend does not seem to operate across all cases. Phylogenetic constraints may limit the correlation among altitude and seed weight, operating particularly against selection for larger seed size, the closer populations and species are related to each other.     

Crossing and selfing experiments in theOrnithogalum umbellatum/augustifolium complex

The fertility relationships ofOrnithogalum umbellatum, O. angustifolium and 9 related taxa were studied.O. umbellatum andO. angustifolium, which are not interfertile, are both recognized as a comparium. Pollination of five species belonging to theO. umbellatum/angustifolium polyploid complex, i.e.O. umbellatum, O. angustifolium, O. baeticum, O. monticolum andO. algeriense, resulted in a moderate seed set. However, the seeds obtained after these interspecific crosses did not germinate. Six related species, i.e.O. exscapum, O. nivale, O. comosum, O. collinum, O. gussonei andO. woronowii showed a very low seed set after being crossed. One exception occurs:O. nivale ×O. exscapum. The seed set was also low after the complex species had been crossed with some related species, but there was one exception: both reciprocal crosses betweenO. monticolum andO. woronowii yielded some viable seeds. No other interspecific crosses gave rise to viable seeds. Bulbil-producing species have a lower seed set after self-pollination than species which do not produce bulbils.Biosystematic Studies on theOrnithogalum umbellatum/angustifolium Complex IV.—Previous contributions: (I–III):Raamsdonk (1982, 1985a, 1985b).     

Giemsa karyotypes and their evolutionary significance inScilla bifolia,S. drunensis,andS. vindobonensis (Liliaceae)

Quantitatively evaluated C-banded and conventional karyograms are presented for the related speciesScilla bifolia subsp.danubialis Speta,S. drunensis (Speta)Speta, andS. vindobonensis Speta. On the basis of banding patterns and karyotype structureS. bifolia subsp.danubialis (2n = 18, 2×) andS. drunensis (2n = 36, 4×) are quite similar, whileS. vindobonensis (2n = 18, 2×) is entirely different. There is a moderate degree of karyotypic variation withinS. bifolia subsp.danubialis andS. drunensis. However, inS. vindobonensis karyotypes and banding patterns are almost completely stable over a geographical range of about 500 km. The present results confirm the recent taxonomic separation ofS. vindobonensis fromS. bifolia, and suggest a considerable phylogenetic distance between these two diploid species. The results are discussed with reference to the morphological characters of the species and their geographical distribution.Evolution ofScilla and Related Genera, II.Dedicated to Univ.-Prof. Dr.Elisabeth Tschermak-Woess on the occasion of her 60th birthday.     

Seed dispersal by the Florida box turtle (<Emphasis Type="Italic">Terrapene carolina bauri</Emphasis>) in pine rockland forests of the lower Florida Keys,United States

Seed dispersal by animals is one of the most important plant-animal mutualisms, but saurochory, the dispersal of seeds by reptiles, has received little attention. We investigated the role of the Florida box turtle (Terrapene carolina bauri) as a seed dispersal agent in pine rockland forests of the lower Florida Keys and examined the effect of turtle digestion on seed germination. We obtained seeds of 11 species with fleshy fruits and 2 species with non-fleshy fruits (a grass and legume) from the feces of 145 box turtles collected on Key Deer National Wildlife Refuge from 1999 to 2000. We planted the seeds of nine species and germination percentage (percentage of seeds that germinated during the experiment) varied from 10% to 80%. Comparative germination experiments were conducted with Thrinax morrissii, Serenoa repens, and Byrsonima lucida. We compared the germination percentage and germination rate (number of days from planting to seedling emergence) of seeds from three treatments (seeds recovered from feces, control seeds with pulp, and control seeds without pulp) and continued these experiments for up to 2 years. Passage through the box turtle digestive tract greatly enhanced the germination percentage and germination rate of S. repens, but decreased the germination percentage of B. lucida and T. morrissii, and decreased germination rate for T. morrissii. Subsequent destructive seed viability tests revealed that many ungerminated T. morrissii seeds remained viable, suggesting long-term seed dormancy may occur, even after passage through the turtle digestive system. In addition, the proportion of ungerminated seeds which remained viable was greater for seeds recovered from turtle feces than from control seeds with pulp. Furthermore, removal of fleshy pulp either manually or by the turtle digestive system may allow T. morrissii to escape insect predation.     

Evolutionary relationships of membrers of the generaTaphrina, Protomyces, Schizosaccharomyces, and related taxa within the archiascomycetes: Integrated analysis of genotypic and phenotypic characters

To study the phylogeny and evolution of archiascomycetes, we determined the full sequence of the nuclear 18S rRNA gene from 14Taphrina species and 2Protomyces species, and the partial sequence ofSchizosaccharomyces japonicus var.japonicus. The sequences were phylogenetically analyzed by the neighbor-joining, maximum parsimony, and maximum-likelihood methods. We also looked at their principal phenotypic characters and genotypic character. Relationships within the Ascomycota are concordant with the previously published phylogenies inferred from 18S rDNA sequence divergence and divide the archi-, hemi-and euascomycetes into distinct major lineages. All the trees show that, within the archiascomycete lineage, 11 of the 14Taphrina species and the 2Protomyces species are monophyletic. A core groups ofTaphrina andProtomyces is always monophyletic. The evidence from molecular and phenotypic characters such as cell wall sugar composition, ubiquinone, cell wall ultrastructure, and mode of conidium ontogeny, strongly suggests that ‘T’. californica CBS 374.39, ‘T’. maculans CBS 427.69 and ‘T’. farlowii CBS 376.39 should be excluded from the archiascomycete lineage. ‘Taphrina’ farlowii CBS 376.39 groups withCandida albicans in the Saccharomycetales, whereas ‘T’. californica CBS 374.39 and ‘T’. maculans CBS 427.69 have a basidiomycete affinity and group with Tremellalean members in the hymenomycete lineage.Schizosaccharomyces is monophyletic. The strictly anamorphic yeastSaitoella complicata groups with the apothecial ascomyceteNeolecta vitellina rather than theTaphrina/Protomyces branch.     

Morphological variation among members of theStellaria longipes complex:S. longipes,S. longifolia,andS. porsildii (Caryophyllaceae)

Morphological relationships were investigated among diploidStellaria porsildii, polyploidS. longipes, and diploidS. longifolia. Canonical discriminant analysis, based on a priori assumptions to maximize differences among groups, showed thatS. longipes clusters equally distant between the two diploid species along an axis connecting the diploids' centroids, but it differs along an axis perpendicular to this axis. The intermediacy along the former axis is evidence thatS. longipes is an amphiploid derived fromS. longifolia andS. porsildii. The divergence along the latter axis may be attributable to adaptively valuable heterotic traits which were retained following amphidiploidization. The only morphological discontinuity occurred between the two diploids, whereas the morphological range ofS. longipes overlapped the range of both diploids forming a continuum. The lack of discrete clusters is likely due to hybridization and introgression withS. longifolia on one hand, and convergence of traits betweenS. longipes var.monantha andS. porsildii on the other. High a posteriori assignments in classificatory discriminant analysis supports the separation ofS. longipes var.monantha from otherS. longipes specimens. AlthoughS. longipes var.monantha grouped close toS. porsildii, the two groups separate based on leaf shape traits. Overall results support, firstly, the hypothesis thatS. porsildii is a diploid parent species which by hybridizing withS. longifolia gave rise to polyploidS. longipes. Secondly, results suggest thatS. longipes var.monantha converged morphologically towardsS. porsildii relatively recently due to ecological specialization, and merits distinction at least as a variety ofS. longipes.     

Survivorship and growth of seedlings of four dipterocarp species in a tropical rainforest of Sarawak,East Malaysia

Survivorship and growth of seedlings of four dipterocarp species (Dipterocarpus actangulus, D. globosus, Dryobalanops aromatica, Dryobalanops lanceolata) were studied for 2.5 years in a mixed dipterocarp forest in Sarawak, East Malaysia. Predispersal seed predation rates were larger forD. globosus (75%) thanD. lanceolata (27–34%) andD. aromatica (18–26%). Less than 20% of the twoDryobalanops seeds were damaged by vertebrates after seed dispersal. During the period from seed dispersal to the time when the seedlings had shed cotyledons, more dispersed seeds died in the twoDipterocarpus (ca 90%) than the twoDryobalanops (ca 60–70%). The major mortality factors during this period were uprooted and seed/seedling predation by insects or vertebrates. After the seedlings shed cotyledons, all species showed constant mortality rates of 34, 15–16, 17 and 6%/year forD. actangulus, D. lanceolata, D. aromatica andD. globosus, respectively, in the forest understorey. Mortality was lower in less shaded conditions than in more shaded ones forD. aromatica andD. actangulus, but not significantly different forD. lanceolata andD. globosus. A majority of dead seedlings were killed by fallen branches or were found standing with wilted leaves, probably due to water stress. No significant correlation was found between seed/seedling mortality and distance from mother trees or the initial density of seeds/seedings for all species. The mean leaf production was positively correlated with the estimated diffuse light factor of their habitats for each species.     

Sedum surculosum andS. jaccardianum (Crassulaceae) share a unique 70 bp deletion in the chloroplast DNA trnL (UAA)-trnF (GAA) intergenic spacer

TrnL (UAA)-trnF (GAA) chloroplast DNA spacer sequences of three species ofMonanthes, Sedum surculosum (=Monanthes atlanticum) andS. jaccardianum were compared.S. surculosum, the systematic position of which has been disputed ever since its discovery, shares a phylogenetically highly significant 70 bp deletion withS. jaccardianum. In addition to this large deletion the two Moroccan species ofS. ser.Monanthoidea differ in three more indels as well as in four nucleotide substitutions from the species ofMonanthes. These data render strong support for the monophyly ofS. ser.Monanthoidea andMonanthes. Spacer length in seven species and one subspecies ofMonanthes is relatively uniform.     

The role of seed dispersal and seedling traits in colonization and coexistence ofSalix species in a seasonally flooded habitat

Regeneration traits of six co-occurringSalix species were studied on a floodplain of the Sorachi River, central Hokkaido, Japan, and their colonization success and coexistence in a local habitat were discussed. MixedSalix communities contained sixSalix species; dominant:S. sachalinensis; four subordinates:S. rorida, S. pet-susu, S. miyabeana andS. subfragilis; rare species:S. jessoensis. Their phenology, falling velocity and longevity of seeds, and the effects of microtopography and soil texture on seedling establishment were studied. The sixSalix species had overlapped seed dispersal periods that coincided with the decrease of water level after a predictable spring flood. This coincidence was crucial for the colonization success because the seedlings were established on wet soils left by the decreasing water level. They showed two types of regeneration trait, specialization and generalization.S. rorida andS. subfragilis showed contrasting regeneration traits; early vs. late seed dispersal, large vs. small seeds, seedling distribution on coarse vs. fine soils, respectively. These two species rarely co-occurred. On the other hand, the dominantS. sachalinensis had an intermediate seed size and dispersal timing, and a wide range of seedling distribution from coarse to fine soils. These results revealed that flooding seasonality influenced the colonization success together with the regeneration traits ofSalix species, and that coexistence of theSalix species was facilitated primarily by regeneration niche separation related to flooding seasonality and soil heterogeneity.     

Phylogenetic relationships inSecale (Poaceae): An isozymatic study

The genetic frequencies of 9 isozyme loci have been estimated in 23 samples of 4 species ofSecale by means of starch gel electrophoresis. The populations ofS. silvestre andS. vavilovii were monomorphic and uniform within each species, those ofS. montanum andS. cereale were polymorphic for most of the isozyme loci. On the basis of isozyme patterns as well as allelic and genotypic frequencies of isozyme loci,S. silvestre can be distinguished fromS. vavilovii, and both fromS. cereale andS. montanum; but there is no clear differentiation between the two latter species. Clusters constructed from genetic distances separateS. silvestre andS. vavilovii, whereasS. cereale andS. montanum were grouped together. The isozymatic data presented here, along with cytogenetic and life habit data, agree with the generally admitted existence of 4 species inSecale, and support the relationships suggested byKhush & Stebbins (1961).     

Crossing experiments of lettuce cultivars and species (Lactuca sect.Lactuca,Compositae)

The degree of relationships withinLactuca sativa and three wild relativesL. serriola, L. saligna, andL. virosa was studied by observing the performance, vigour and fertility of the F 1 hybrids obtained from crosses made in and between the four species. The crosses ofL. saligna ×L. virosa and the reciprocal crosses produced no hybrids.L. saligna andL. virosa are the least related of the four species.L. sativa ×L. serriola and the reciprocal crosses were successful and produced fertile hybrids These two species are genetically very closely related.L. saligna is known to produce, as a female parent, hybrids withL. sativa andL. serriola. Now the reciprocal cross was successful for the first time, so the unability to obtain hybrids in the past was based on the choice of accessions and not caused by unilateral incompatibility.L. virosa ×L. sativa and the reciprocal combination produced hybrids. The combinationL. serriola ×L. virosa produced hybrids with very limited fertility. In contrast to earlier reports (sterile hybrids) one combination of the reciprocal cross too produced hybrids with very limited fertility.—Some of theL. saligna ×L. sativa (and reciprocal) hybrids were found to look strikingly likeL. serriola. This adds evidence for the descent ofL. serriola andL. sativa:L. saligna also made part of the ancestral complex of the cultivated lettuce.     

莫莫格扁秆藨草恢复湿地土壤种子库对长芒稗入侵的响应

湿地恢复过程中,时常有外来种或本地杂草入侵。土壤种子库作为未来植被的潜在种源,对湿地恢复效果具有重要的指示意义。在莫莫格国家级自然保护区,以恢复白鹤栖息地(扁秆藨草(Scirpus planiculmis)沼泽)为目的,进行了退化湿地的水文恢复;但退化湿地恢复2a后,一年生杂草长芒稗(Echinochloa caudata)在大部分区域成为建群种。以长芒稗入侵湿地和扁秆藨草自然湿地为研究对象,对比分析了长芒稗和扁秆藨草的土壤种子库及生长结实特征。结果表明,在自然湿地扁秆藨草种子库规模是长芒稗的18.42倍,而在恢复湿地长芒稗种子库大小是扁秆藨草的5.04倍。与自然湿地相比,扁秆藨草种子库密度在入侵湿地明显减少,但仍保留了一定量具有活力的种子(664.32±105.98)粒/m~2,这与研究区扁秆藨草较高的种子生产力(9210.4±1513.4)粒/m~2及种子较强的浮力(FP50=39.7d)有关,说明扁秆藨草具备通过种子库或水传播恢复的潜力。长芒稗土壤种子库密度在入侵湿地高达(3345.9±520.3)粒/m~2,明显高于自然湿地种子库规模(P0.01),说明恢复湿地受长芒稗入侵影响严重,这与长芒稗较高的种子生产力(7621.4±376.25)粒/m~2及较弱的种子浮力(FP0=5d)有关,同时也表明长芒稗通过水传播扩散的能力较弱。另外,研究区长芒稗平均高度超过1m,且盖度较大,不仅阻碍扁秆藨草种子的水播,也降低了到达地表的光照水平,从而抑制扁秆藨草更新。因此,在莫莫格受长芒稗入侵湿地,于开花结实前收获长芒稗地上植物体及凋落物应是限制长芒稗扩展、同时促进扁秆藨草恢复的有效措施。     

Importance of fragmentation-tolerant species as seed dispersers in disturbed landscapes

Forest fragmentation can negatively affect plants if animal seed-dispersers become locally extinct in fragments. We conducted a 2-year experiment to evaluate the importance of tree squirrels (Sciurus) as seed dispersers for Quercus, Carya, and Juglans, and to assess dispersal consequences in patches where fragmentation-sensitive eastern gray squirrels (Sciurus carolinensis) are absent. We accounted for fates of ∼15,700 seeds from five tree species in four exclosure treatments at 18 fragments during a high (2003–2004) and low seed (2004–2005) year. Two treatments excluded Sciurus to mimic disperser loss. We sampled nut-tree seedling density at 259 sites across eight watersheds, half of which were too fragmented to support S. carolinensis, but supported fragmentation-tolerant fox squirrels (Sciurus niger). Autumn-to-spring seed survival was low (∼1%) for all species during low seed production. During high seed production, survival was higher for Juglans nigra (20%) and Carya ovata (16%) than for three Quercus species (∼4% for Quercus palustris and Quercus rubra in two exclosure types; ∼1% for Quercus alba in all treatments). Survival of J. nigra, C. ovata, and Q. rubra was ≥2.1–7.7 times higher for seeds in exclosures that Sciurus could access. Seed displacement distance was higher in the low seed than the seed-rich year, but the proportion of seeds surviving to greater distances was higher in seed-rich years for all seed types except Q. rubra. This affirms the importance of masting to seed survival and dispersal, but also suggests an advantage to trees of producing seed in non-mast years. Seedling densities were comparable in watersheds with and without S. carolinensis. These results demonstrate the importance of tree squirrels as dispersers of nut-bearing trees, but suggest that fragmentation may not disrupt dispersal of certain species if losing S. carolinensis from disturbed landscapes is compensated for by fragmentation-tolerant fox squirrels (S. niger).     

Distance effect of co-occurring tree species on pine wilt disease incidence inPinus densiflora seedlings inoculated withBursaphelenchus xylophilus

Field-grownPinus densiflora seedlings were inoculated withBursaphelenchus xylophilus and the incidence of pine wilt disease was analyzed with respect to the spatial relationships between pine seedlings and adjacent seedlings of other tree species in a pure pine stand and three stands mixed withAlnus sieboldiana, Sarothamus scoparius or naturally associated species. The disease incidence was 60.9% in a 0–40 cm distance class from the nearestA. sieboldiana seedlings and then decreased with increasing minimum distance. The mean minimum distance between pine seedlings andA. sieboldiana was significantly shorter in diseased seedlings than in healthy ones. The highest disease incidence (53.9%) was found in a 0–40 cm distance class from the nearestS. scoparius, although the relationship with minimum distance was blurred by a high incidence in the 80-cm distance class. The mean minimum distance between pine seedlings was significantly short in diseased seedlings in a pure stand, whereas it was not so short between pine seedlings and other tree species in the two stands mixed withS. scoparius and the naturally associated species. The distance effect on disease incidence was noticeable inA. sieboldiana andP. densiflora at high density. This was not so clear inS. scoparius and was not found in the naturally associated species.     

Phylogenetic relationships in theSideritis leucantha group (Lamiaceae)

Six closely related taxa of the sect.Eusideritis of the genusSideritis (S. leucantha, S. pusilla, S. flavovirens, S. granatensis, S. biflora andS. osteoxylla) are analysed to elucidate their phylogenetic relationships and position within the sect.Eusideritis. Meiotic behaviour, karyotype features, size and fertility of pollen grains, DNA amounts and seed protein profiles are reviewed. A polyploid origin of the group (from x = 7) and the further diversification through dysploidy and chromosome repatterning is postulated.S. osteoxylla is apparently of hybrid origin.     

Gene variation and gene flow inOrchis morio (Orchidaceae) from Italy

Data are presented on genetic variation at 27 enzyme loci of the Green-Winged orchid,Orchis morio, in 18 population samples from Italy. The existence in Italy of two subspecies, i.e. subspp.morio andpicta, is not supported by allozyme data. No genetic heterogeneity was found betweenmorio-like andpicta-like samples and specimens. Moreover, morphological transition between the two forms was observed in different Italian populations. The parameters of genetic variability estimated forO. morio populations are consistent with those found among monocotyledon plants, and among those outcrossing, animal-pollinated and with wind-dispersed seeds. Genetic diversity of ItalianO. morio is mostly within populations. Correspondingly, low values of interpopulational genetic distance were found. This appears to be due to high levels of gene flow, which were estimated with different methods. The lack ofO. longicornu from Italian samples, as well as of any hybrid withO. morio (F₁, backcrossed or recombinant individuals) is demonstrated on the basis of genetic data. It is concluded that recurrent reports ofO. longicornu from Italy are due to confusion withO. morio or with otherOrchis species.     

Analysis of the clinal variation pattern inSilene latifolia (Caryophyllaceae) pollen morphology

Reticulate and microechinate pollen forms withinSilene latifolia (S. alba, S. pratensis) were first described from N. America, where the species is an introduced weed. A previous study showed that the two forms also exist in Europe and intergrade along a zone roughly congruent with intergradation zones in seed morphology and flavone glycosylation genotypes. The present survey of pollen from herbarium specimens is more extensive and covers localities from nearly the whole of the species' native Eurasian and North African range. The first axis of a detrended correspondence analysis (DCA) of qualitative characterstate data for 11 pollen morphological characters shows a gradient between the two extreme exine types, reticulate and microechinate. When mapped, the co-ordinates of pollen samples on this axis indicate a broad zone of intergradation which coincides approximately with the somewhat sharper transition between low- and high-tubercle seeds in C. and N. Europe, but becomes diffuse in Italy and the Mediterranean region and diverges from the seed transition zone in SW. Asia and the Middle East. The biological significance of the pollen morphs is unknown; the variation pattern in pollen morphology, unlike that in seeds, is not consistently correlated with macroclimate.     

The 5S DNA units of bread wheat (Triticum aestivum)

A collection of 44 cloned 5S DNA units fromTriticum aestivum cv. Chinese Spring were grouped into 12 sequence-types based on sequence similarity and the respective consensus sequences were then produced. The relationship between these 12 consensus sequences (T. aestivum S 1-S 8 andT. aestivum L 1-L 4), together with two clones sequenced byGerlach andDyer, and the 5S DNA consensus sequences from diploidTriticum spp. were then determined by numerical methods. Both phenetic and cladistic analyses were carried out. The following wheat 5S DNA sequences were found to group with respective sequences from diploidTriticum spp.:T. aestivum S 4, S 6 withT. tauschii S;T. aestivum S 3 withT. monococcum S andT. monococcum S-Rus 7;T. aestivum L 1 andT. aestivum L-G&D withT. speltoides L;T. aestivum L 2, L 3 withT. tauschii L;T. aestivum L 4 withT. monococcum L andT. monococcum L-Rus 12. The analyses suggested that 5 out of the 65S Dna loci present in wheat were identified at the sequence level. The locus that could not be identified in this analysis was the5S Dna-B 1 locus. A group ofT. aestivum sequences (T. aestivum S 1, S 7, S 8, S-G&D) were found to be distinct from the other 5S DNA sequences in the data base. The existence of the distinct group of 5S DNA sequences suggests that there is a gap in our current understanding of wheat evolution with respect to the5S Dna loci.