PubMed · 13323402
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G M SANTOS, A J ESTRADA. 1956. [Subcutaneous paronychia].. https://pubmed.ncbi.nlm.nih.gov/13323402/
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This is the first report of a study devoted to the population genetics of speciation in the endemic Hawaiian plant genus Schiedea (Caryophyllaceae). Here, we report the estimates of DNA sequence diversity and divergence in a newly isolated nuclear gene from Maui and Oahu Schiedea globosa populations. Overall, the species-wide average heterozygosity per silent site is pi = 0.3%. The silent DNA diversity on the older island of Oahu (pi = 0.24%) is almost twice as high as on the younger Maui (pi = 0.14%). Consistent with this, the haplotype phylogeny suggests a more recent origin of the Maui populations. There is no significant isolation between the two Maui populations (F(st)=0.027), while isolation between the two islands is high (F(st)=0.57, P<0.0001). Pairwise mismatch distributions suggest population growth approximately 660 and 310 thousand generations ago for the Oahu and the Maui populations, respectively, which may be the minimal age for these populations. This is consistent with a fairly neutral frequency spectrum (Tajima's D is 0.34 and -0.94 for the Oahu and the Maui populations, respectively), suggesting that both populations are sufficiently old to have recovered from any initial founder effects. Relatively high nuclear DNA diversity in the S. globosa populations illustrates the usefulness of a DNA sequence-based approach to the population genetics of island plant populations.
Five new triterpenoid monodesmosides (sinocrassulosides I-V, 1-5) and six bisdesmosides (sinocrassulosides VI-XI, 6-11), in which 2-11 possess different acyl groups in the glycosidic moieties, were isolated from the roots of Sinocrassula asclepiadea FRANCH. Sinocrassulosides VI (4) and V (5) also contained a novel A-seco aglycone in their structures. All of the structures were determined on the basis of spectroscopic and physicochemical evidence.
BACKGROUND AND AIMS: The formation of zonal communities may be attributed to differences in germination across the community and to timing of germination of seeds present in the seed bank. Our goals were two-fold: (1) to assess the annual germination pattern of Spergularia marina; and (2) to determine whether germination of S. marina differed across zonal communities. METHODS: Fresh seeds were buried in an experimental garden in polyester bags. Bags were harvested monthly for 1 year and exposed to differing 12 h/12 h temperature regimes (5/15 degrees C, 5/25 degrees C, 15/25 degrees C and 20/35 degrees C) with a 12 h dark/12 h light photoperiod. Replicate seeds were exposed to 24 h dark. Seeds were also placed in different zonal communities to assess germinability in the field. KEY RESULTS: Spergularia marina has a primary physiological dormancy. Conditional dormancy occurs from December to May and non-dormancy from June to November. Field germination initiates in the spring when temperatures are cool and salinity is low due to flooding, and ceases in the summer when temperatures exceed germination requirements. Spergularia marina has a light requirement for germination. CONCLUSIONS: If seeds become buried in the field or are light inhibited by Phragmites australis, they will remain dormant until they receive an adequate amount of light for germination. Since S. marina can germinate across all zones in a salt-marsh community, the formation of zonal communities is not determined at the germination stage, but at some later stage of development.