DNA variation in a conifer, Cryptomeria japonica (Cupressaceae sensu lato). (1/5)

We investigated the nucleotide variation of a conifer, Cryptomeria japonica, and the divergence between this species and its closest relative, Taxodium distichum, at seven nuclear loci (Acl5, Chi1, Ferr, GapC, HemA, Lcyb, and Pat). Samples of C. japonica were collected from three areas, Kantou-Toukai, Hokuriku, and Iwate. No apparent geographic differentiation was found among these samples. However, the frequency spectrum of the nucleotide polymorphism revealed excesses of intermediate-frequency variants, which suggests that the population was not panmictic and a constant size in the past. The average nucleotide diversity, pi, for silent sites was 0.00383. However, values of pi for silent sites vary among loci. Comparisons of polymorphism to divergence among loci (the HKA test) showed that the polymorphism at the Acl5 locus was significantly lower. We also observed a nearly significant excess of replacement polymorphisms at the Lcyb locus. These results suggested possibilities of natural selection acting at some of the loci. Intragenic recombination was detected only once at the Chi1 locus and was not detected at the other loci. The low level of population recombination rate, 4Nr, seemed to be due to both low level of recombination, r, and small population size, N.  (+info)

Mid- to late-Holocene El Nino-Southern Oscillation dynamics reflected in the subtropical terrestrial realm. (2/5)

High resolution pollen analysis of mid- to late-Holocene peat deposits from southwest Florida reveals a stepwise increase in wetland vegetation that points to an increased precipitation-driven fresh water flow during the past 5,000 years. The tight coupling between winter precipitation patterns in Florida and the strength of the El Nino-Southern Oscillation (ENSO) strongly suggests that the paleo-hydrology record reflects changes in ENSO intensity. A terrestrial subtropical record outside the Indo Pacific Warm Pool both documents ecosystem response to the known onset of modern-day ENSO periodicities, between approximately 7,000 and 5,000 years B.P., and subsequent ENSO intensification after 3,500 years B.P. The observed increases in "wetness" are sustained by a gradual rise in relative sea level that prevents a return to drier vegetation through natural succession.  (+info)

Contrasting patterns of DNA variation in natural populations of two related conifers, Cryptomeria japonica and Taxodium distichum (Cupressaceae sensu lato). (3/5)

We investigated DNA variation within and between two closely related conifers, Cryptomeria japonica and Taxodium distichum, at nuclear loci encoding ferredoxin, glutamyl-tRNA reductase, lycopene beta cyclase, and phosphoribosylanthranilate transferase. Average nucleotide diversity at silent sites was estimated to be 0.0035 (SE 0.0012) in C. japonica and 0.0058 (SE 0.0006) in T. distichum. One population in C. japonica was differentiated from the others but generally there was not much differentiation among populations or varieties within the two species. However, the two species seemed to differ in frequency spectra of DNA polymorphisms. Excesses of intermediate-frequency variants were found in C. japonica, whereas excesses of both rare and high-frequency variants were found in T. distichum, which suggested different histories of population structures in the two species. Deviations from the standard neutral expectations in DNA polymorphisms were found by applications of neutrality tests. The results show that actions of selection to respective loci seem to differ between the two species, indicating differences of interaction among evolutionary factors.  (+info)

Soil warming alters seed-bank responses across the geographic range of freshwater Taxodium distichum (Cupressaceae) swamps. (4/5)

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Characterization of the genome of bald cypress. (5/5)

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