14. Speciation And Geographic Differentiation

The soilborne pathogen Plasmodiophora brassicae causes clubroot on Brassica crops, a common disease in many oilseed rape growing regions. Here, we investigate genetic diversity and geographic differentiation of P. brassicae populations from different regions in Germany. We compared three regions that differ in oilseed rape cropping history, oilseed rape acreage, and incidence of clubroot. These regions were either spatially separated or separated by the former inner German border. Plasmodiophora isolates were collected from 59 fields (29, 17, and 13 fields per region, respectively) and 174 amplified fragment length polymorphism (AFLP) markers were analyzed. Every field isolate showed a unique genotype pattern; that is, no genotype was shared among the regions and different fields. The mean gene diversity was 0.27, suggesting that P. brassicae is a genetically diverse species. The comparison of indexes (gene diversity, genotypic diversity, and linkage disequilibrium) between the regions does not support our hypotheses that cropping history, oilseed rape acreage, and incidence of clubroot affect these estimates. Principal component analysis (PCA), fixation index (FST), and generalized linear model (GLM) were suitable to specify regional differences. PCA revealed two clusters of isolates based on the geographic origin of the isolates and FST showed that these clusters were highly differentiated. Hypotheses about association of genotypes with different spatial scales were tested with GLM: the region, reflecting the cropping history, and the individual field had a significant effect on the AFLP pattern. We propose that individual field isolates represent a discrete population and that geographic differentiation results from low levels of gene flow due to the limited dispersal of this soilborne pathogen and from localized selection pressure as unifying force on the genotypes.

Download Full-text

Seed Morphometrics and Adaptive Geographic Differentiation

Evolution ◽

10.2307/2411072 ◽

1998 ◽

Vol 52 (2) ◽

pp. 344 ◽

Cited By ~ 10

Author(s):

D. Lawrence Venable ◽

Eric Dyreson ◽

Daniel Pinero ◽

Judith X. Becerra

Keyword(s):

Geographic Differentiation

Download Full-text

South American anoles: the geographic differentiation and evolution of the Anolis chrysolepis species group (Sauria, Iguanidae)

Arquivos de Zoologia ◽

10.11606/issn.2176-7793.v19i1-2p1-176 ◽

1970 ◽

Vol 19 (1-2) ◽

pp. 1 ◽

Cited By ~ 144

Author(s):

P. E. Vanzolini ◽

Ernest E. Williams

Keyword(s):

Species Group ◽

South American ◽

Geographic Differentiation

Download Full-text

The Orthoptera fauna of the Stelvio National Park

Bollettino della Società Entomologica Italiana ◽

10.4081/bollettinosei.2018.3 ◽

2018 ◽

pp. 3-20

Author(s):

Daniele Baroni ◽

Marco Bonifacino ◽

Luca Cristiano ◽

Roberta Rossi ◽

Luca Pedrotti ◽

...

Keyword(s):

Habitat Loss ◽

Species Distribution ◽

Protected Area ◽

National Park ◽

Conservation Value ◽

Geographic Differentiation ◽

Biodiversity Monitoring ◽

Check List ◽

Alpine Environment ◽

High Conservation

Within the Project “Animal Biodiversity Monitoring in the Alpine Environment” the Orthoptera fauna has been studied in a three-year period (2013-2015). The first check-list of the protected area, with ecological and biogeographical notes, is presented. We found 40 species (16 Ensifera, 24 Caelifera), corresponding to 11% of the Italian Orthoptera fauna. A geographic differentiation in species distribution among the three areas (Alto Adige - BZ, Trentino - TN and Lombardy - BS and SO) has been detected. The genus Barbitistes is represented by B. serricauda in Alto Adige and B. alpinus in Trentino and Lombardy. Kisella irena is restricted to Peio and Rabbi Valleys only, in connection with this species distribution in Trentino. Within the Park, Euthystira brachyptera is distributed only in Lombardy, despite its habitat is apparently extensively available also in Trentino and Alto Adige. We found Omocestus haemorrhoidalis and Chorthippus vagans only in Val Venosta (BZ). Only two species, previously reported for the study area, has not been detected during our surveys: Celes variabilis and Ruspolia nitidula. The first site of presence of Tettigonia caudata, rare in Italy, within the Park boundaries has been discovered near Martello (BZ). Two endangered taxa of high conservation value, Epacromius tergestinus ponticus and Crysochraon dispar, reported in the last Century just outside the Park boundaries, are probably extinct today due to habitat loss.

Download Full-text