Nothotsuga longibracteata, a relic and endangered conifer species endemic to subtropical China, was studied for examining the spatial-temporal population genetic variation and structure to understand the historical biogeographical processes underlying the present geographical distribution. Ten populations were sampled over the entire natural range of the species for spatial analysis, while thre...

BACKGROUND AND AIMS Intraspecific genome size variability of Festuca pallens occurring on relict rocky steppes in Central Europe was studied on two ploidy levels and three geographical scales: (1) local scale of 24 populations, (2) landscape scale of three transects in river canyons or hill systems, and (3) global scale of 160 samples covering the whole distribution area. METHODS DAPI flow cy...

BACKGROUND Triatoma dimidiata is one of the most significant vectors of Chagas disease in Central America and Colombia, and, as in most species, its pattern of genetic variation within and among populations is strongly affected by its phylogeographic history. A putative origin from Central America has been proposed for Colombian populations, and high genetic differentiation among three biograph...

The bristle-spined porcupine, Chaetomys subspinosus, an endemic rodent from Atlantic Forest, was considered to be abundant in the recent past, but population reductions due to habitat loss and expansion of human activities caused this species to be included in the "vulnerable" category of the World Conservation Union Red List. We performed the first genetic assessment in natural populations of ...

It has long been argued that populations living on the edges of the species geographical range should exhibit stronger environmentally imposed variations in abundances than populations living near the centre of this range. This so-called ‘Species Range Hypothesis’ is tested here for the recruitment of 62 marine fish populations of the northeast Atlantic, belonging to 17 species. The pattern of ...

Analyzing genetic population structure is useful in gaining insight about the evolutionary history of human populations. It gives us an understanding of the genetic similarities and differences between different populations and helps study their isolation, migration and inter-mixing. With modern genotype sequencing methods, new data sets about human population are becoming available. The Human ...

fifteen yarrow populations from different species achillea millefolium l., a. biebersteinii l. and a. nobilis, from different geographical areas of iran were studied using 24 morphological traits and peroxidase profiles. comparison of mean values of different phenotypic traits show a. millefolium and a. biebersteinii l. had higher plant height and crown diameter; however, a. nobilis had higher ...

The research enterprise increasingly involves multidisciplinary collaboration, sometimes over geographic distance. Technological advances have made these collaborations possible, and the history of past innovations suggests these collaborations are desirable. Yet multidisciplinary projects can carry high coordination costs. This study investigated how collaborations address disciplinary differe...

Citizenship in the United States: The Roles of Immigrant Characteristics and Country of Origin This study develops and estimates a model of the naturalization process in the US. The model is based on both the characteristics of immigrants and features of their countries of origin. The empirical analysis is based on the 2000 US Census. Both the characteristics of immigrants and the origin-countr...

Helicobacter pylori, a chronic gastric pathogen of human beings, can be divided into seven populations and subpopulations with distinct geographical distributions. These modern populations derive their gene pools from ancestral populations that arose in Africa, Central Asia, and East Asia. Subsequent spread can be attributed to human migratory fluxes such as the prehistoric colonization of Poly...