Ecological Species, Multispecies, and Oaks

Valen, Leigh Van

doi:10.2307/1219444

Cited by 682 publications

(376 citation statements)

References 30 publications

Supporting

Mentioning

353

Contrasting

Unclassified

Order By: Relevance

“…The extensive occurrence of hybrids within the genus is now well documented; Hardin (1975) Burger (1975), to question the traditional species concept within Quercus and for some to suggest alternatives, such as the multispecies (Van Valen, 1976), a concept very like that of the syngameon (Grant, 1971 …”

Section: Resultsmentioning

confidence: 99%

Natural hybridization within the genus Quercus L

1993

View full text Add to dashboard Cite

Section: Resultsmentioning

confidence: 99%

Natural hybridization within the genus Quercus L

1993

View full text Add to dashboard Cite

“…In an attempt to bring order to the inconsistent and unstable Dactylorhiza taxonomy, Pedersen (1998) proposed a taxonomic ranking where species should correspond to the biological species concept in a botanically focused way (Mayr 1940;Jonsell 1984), subspecies to the ecological species concept (Van Valen 1976) and varieties to the phenetic species concept (Sneath 1976). All units should have some evolutionary relevance.…”

Section: Taxonomic Inferencesmentioning

confidence: 99%

Systematics and phylogeography of the Dactylorhiza maculata complex (Orchidaceae) in Scandinavia: insights from cytological, morphological and molecular data

Ståhlberg

Hedrén

2008

Plant Syst Evol

View full text Add to dashboard Cite

Flow cytometry, morphometry and molecular markers [plastid DNA and internal transcribed spacers (ITS) of nuclear ribosomal DNA] were used to determine taxonomic and phylogeographic patterns in Dactylorhiza maculata s.l. from Scandinavia. A total of 238 individuals from 27 populations from throughout all of Scandinavia, including the adjacent Kola Peninsula of Russia, were analyzed. Diploid D. maculata ssp. fuchsii and autotetraploid D. maculata ssp. maculata are morphologically differentiated. Fragment size variants from 10 plastid DNA loci (seven microsatellite loci and three loci with indel variation) were combined to give 43 haplotypes. Three major groups of haplotypes were found. Group I haplotypes were prevalent in the north and the northeast, whereas Group II haplotypes were prevalent in the south and the southwest. Group III was represented by only a single haplotype and appeared to be the result of introgression from D. incarnata s.l. Group I and Group II haplotypes did not correspond with cytologically and morphologically defined D. maculata ssp. fuchsii or D. maculata ssp. maculata. Past introgressive gene flow rather than recent hybridization is envisaged. Intermediate Group I haplotypes between Group II and the rest of Group I were detected in a zone of contact in central Sweden, which may suggest plastid DNA recombination. The six ITS alleles scored showed strong positive correlation with taxonomy. All data sets obtained for ssp. maculata were significantly correlated with geography. Three different autotetraploid lineages are hypothesized. One lineage may represent postglacial immigration from the south and the other two lineages may represent eastern immigration routes. Morphology and ITS data suggested that subarctic populations of ssp. maculata should be recognized as var. kolae¨nsis.

show abstract

“…New approaches based on whole genome comparisons such as Average Nucleotide Identity (ANI) have emerged and combined with eco-physiological concepts (for example, ecotype concept (Van Valen, 1976)) could lead to a more holistic bacterial species definition (Rosselló -Mora and Amann, 2001; Konstantinidis et al, 2006;Cohan and Kopac, 2011;Caro-Quintero and Konstantinidis, 2012). Escherichia coli exemplifies the complexities of the current species definition issue.…”

Section: Introductionmentioning

confidence: 99%

Gene expression analysis of E. coli strains provides insights into the role of gene regulation in diversification

et al. 2014

View full text Add to dashboard Cite

Escherichia coli spans a genetic continuum from enteric strains to several phylogenetically distinct, atypical lineages that are rare in humans, but more common in extra-intestinal environments. To investigate the link between gene regulation, phylogeny and diversification in this species, we analyzed global gene expression profiles of four strains representing distinct evolutionary lineages, including a well-studied laboratory strain, a typical commensal (enteric) strain and two environmental strains. RNA-Seq was employed to compare the whole transcriptomes of strains grown under batch, chemostat and starvation conditions. Highly differentially expressed genes showed a significantly lower nucleotide sequence identity compared with other genes, indicating that gene regulation and coding sequence conservation are directly connected. Overall, distances between the strains based on gene expression profiles were largely dependent on the culture condition and did not reflect phylogenetic relatedness. Expression differences of commonly shared genes (all four strains) and E. coli core genes were consistently smaller between strains characterized by more similar primary habitats. For instance, environmental strains exhibited increased expression of stress defense genes under carbon-limited growth and entered a more pronounced survival-like phenotype during starvation compared with other strains, which stayed more alert for substrate scavenging and catabolism during no-growth conditions. Since those environmental strains show similar genetic distance to each other and to the other two strains, these findings cannot be simply attributed to genetic relatedness but suggest physiological adaptations. Our study provides new insights into ecologically relevant gene-expression and underscores the role of (differential) gene regulation for the diversification of the model bacterial species.

show abstract

Ecological Species, Multispecies, and Oaks

Cited by 682 publications

References 30 publications

Natural hybridization within the genus Quercus L

Natural hybridization within the genus Quercus L

Systematics and phylogeography of the Dactylorhiza maculata complex (Orchidaceae) in Scandinavia: insights from cytological, morphological and molecular data

Gene expression analysis of E. coli strains provides insights into the role of gene regulation in diversification

Contact Info

Product

Resources

About