A preliminary examination of genetic variation in a peripheral population of Blanding's turtle, Emydoidea blandingii

Random amplified polymorphic DNA (RAPD) was used to compare the Nova Scotia population of Blanding's turtle (Emydoidea blandingii) with several populations from the species' main range. The Nova Scotia population is believed to have been isolated from the main range for 4000-8000 years. Cluster analysis using a neighbour-joining algorithm produced a dendrogram showing the Nova Scotia population clustering separately from those populations in the main range. Analysis of molecular variance shows 34.28% of total variance to be accounted for between the Nova Scotia population and populations in the main range. While this study is preliminary, the results suggest that the Nova Scotia population of Blanding's turtle may be important to the maintenance of genetic diversity in the species.     

Site‐to‐site variation in the demography of a fire‐affected perennial. Acacia suaveolens,at Ku‐ring‐gai Chase National Park,New South Wales,Australia

Abstract Acacia suaveolens (Sm.) Willd is a perennial shrub that forms even‐aged stands, recruited from a soil seed‐bank following fire. It has previously been subject to demographic studies, which used a space‐for‐time substitution to investigate temporal patterns following fire. In the present study the potential for spatial variation across sites was investigated by sampling at several similarly aged populations in Ku‐ring‐gai Chase National Park, northern Sydney, Australia. Significant variation in mean size and fecundity of A. suaveolens individuals was observed among sites, over a 2‐4.6‐fold range in plant size, and a sevenfold range in mean fecundity. The observed variation at 3 years after fire encapsulated most of the variation previously observed among sites 0‐17 years since fire, emphasizing the importance of spatial variation in this species. For each site a two‐stage (seed, plant) matrix model was constructed, and projected from 3 to 25 years following fire. Population growth was measured as number of seeds per 3‐year‐old plant, and found to vary 1.4‐fold across models for different sites. This site‐to‐site variation, as well as that in size, fecundity and survival, was statistically significant. Variation in projected seeds per plant could mostly be attributed to differences in fecundity rather than plant survival. Sensitivity analyses emphasized the biological significance of the variation in fecundity. Whereas previous studies have focused on temporal variation, this work demonstrates the importance of extending our understanding of a species to include the spatial component of population dynamics.     

Comparisons of phylogenetic hypotheses among different data sets in dwarf dandelions (Krigia,Asteraceae): Additional information from internal transcribed spacer sequences of nuclear ribosomal DNA

The internal transcribed spacer (ITS) region of the 18 S–25 S nuclear ribosomal DNA repeat was sequenced from 19 populations of the tribeLactuceae, including all species of dwarf dandelion (Krigia) and five outgroup genera. The incidence of length changes and base substitutions was at least two times higher for ITS 1 than ITS 2. Interspecific sequence divergence withinKrigia averaged 9.62% (1.61%–15.19%) and 4.26% (0%–6.64%) in ITS 1 and ITS 2, respectively. Intergeneric sequence divergence ranged from 15.6% to 44.5% in ITS 1 and from 8.0% to 28.6% in ITS 2. High sequence divergence and homoplasy among genera of tribeLactuceae suggest that the phylogenetic utility of ITS sequence data is limited to interspecific studies or comparisons among closely related genera. Trees generated from ITS sequences are essentially identical to those from restriction site comparisons of the entire nuclear ribosomal (nr) DNA region. The degree of tree resolution differed depending on how gaps were treated in phylogenetic analyses. The ITS trees were congruent with the chloroplast DNA and morphological phylogenies in three major ways: 1) the sister group relationship betweenKrigia andPyrrhopappus; 2) the recognition of two monophyletic sections,Krigia andCymbia, in genusKrigia; and 3) the monophyly of theK. occidentalis-K. cespitosa clade in sect.Cymbia. However, the two nrDNA-based trees are not congruent with morphology/chloroplast DNA-based trees for the interspecific relationships in sect.Krigia. An average of 22.5% incongruence was observed among fourKrigia data sets. The relatively high degree of incongruence among data sets is due primarily to conflict between trees based on nrDNA and morphological/cpDNA data. The incongruence is probably due to the concerted evolution of nrDNA repeating units. The results fromKrigia and theLactuceae suggest that nrDNA data may have limited utility in phylogenetic studies of plants, especially in groups which exhibit high levels of sequence divergence. Our combined phylogenetic analysis as a total evidence shows the least conflict to each of the individual data sets.     

The effectiveness of ISSR profiling for studying genetic diversity of Aspergillus flavus from peanut-cropped soils in China

We used markers based on inter-simple sequence repeats (ISSR) to examine the genetic diversity of Aspergillus flavus from peanut-cropped soils in China. Of the 100 primers, 22 primers produced clear and reproducible ISSR bands, and the di-nucleotide accounted for 73% of those primers. The size of DNA fragments ranged from 100 to 2000 bp. The primer UBC 834 produced the largest number of polymorphic bands (10), followed by UBC 809, UBC 817, UBC 895, and UBC 899, which all amplified 7 polymorphic bands. Using the five primers, the tested strains were clearly separated based on genetic similarity coefficients (GSC). The range of GSC was from 0.59 to 0.90. In unweighted pair-group method with arithmetic averages (UPGMA) analysis, the A. flavus samples grouped in five clusters. The study showed that the ISSR technology is an effective molecular approach for studying diversity of A. flavus from peanut-cropped soils in China.