Reduced genetic structure of the Iberian peninsula revealed by Y-chromosome analysis: implications for population demography

Abstract

Europe has been influenced by both intra-and intercontinental migrations. Since the Iberian peninsula was a refuge during the Last Glacial Maximum, demographic factors associated with contraction, isolation, subsequent expansion and gene flow episodes have contributed complexity to its population history. In this work, we analysed 26 Y-chromosome biallelic markers in 568 chromosomes from 11 different Iberian population groups and compared them to published data on the Basques and Catalans to gain insight into the paternal gene pool of these populations and find out to what extent major demographic processes account for their genetic structure. Our results reveal a reduced, although geographically correlated, Y-chromosomal interpopulation variance (1.2%), which points to a limited heterogeneity in the region. Coincidentally, spatial analysis of genetic distances points to a focal distribution of Y-chromosome haplogroups in this area. These results indicate that neither old or recent Levantine expansions nor North African contacts have influenced the current Iberian Y-chromosome diversity so that geographical patterns can be identified.

Using mitochondrial DNA to test the hypothesis of a European post-glacial human recolonization from the Franco-Cantabrian refuge

“…These results are also in accordance with the different patterns found for the Y-chromosome haplogroup distribution in continental Europe compared with the Mediterranean peninsulas, with smooth clines and gradients apparent in continental areas (Rosser et al, 2000;Semino et al, 2000) contrasting to the focal expansions detected in Iberia (Flores et al, 2004), Italy and Greece (Di Giacomo et al, 2003).…”

“…The Y-chromosome I-M253 subclade has been proposed as another lineage signalling a northward expansion from the Iberian Peninsula-Southern France refuge after the LGM (Rootsi et al, 2004). However, Y-chromosome analysis of Iberia pointed to the I-M26 subclade as the most prevalent there (Flores et al, 2004;Alonso et al, 2005;Lopez-Parra et al, 2009). It has been suggested that a region of Iberia-Southern France could be the origin of this subclade (Rootsi et al, 2004).…”

The relationship between surname frequency and Y chromosome variation in Spain

“…The controls we used in this study showed haplogroup frequencies similar to previous Y chromosome studies in Spain, [19][20][21] and most of the frequent and very frequent surnames showed haplogroup distributions similar to this control set (Table 1). For other less frequent surnames, in many cases, haplogroup composition was biased towards one or two haplogroups, indicating that sampling men with the same surname is far from random.…”

A CXCL2 tandem repeat promoter polymorphism is associated with susceptibility to severe sepsis in the Spanish population

“…However, it has been shown that both continental and Island populations have suffered from North African influences at different levels. [17][18][19][20][21] The Canary Islanders, the populations from Castilla and the southern Spanish populations from Andalusia have been reported to have the highest percentage of North African influences in Spain. 19,20 In order to meet power requirements (see Materials and methods) while preserving the homogeneity of the population, we included 179 unrelated patients, which met severe sepsis criteria, 22 from different Spanish localities with as similar as possible genetic backgrounds: Tenerife, one of the major islands of the Canarian Archipelago (a total of 64 patients) and different localities from Castilla (a total of 115 patients).…”

“…[17][18][19][20][21] The Canary Islanders, the populations from Castilla and the southern Spanish populations from Andalusia have been reported to have the highest percentage of North African influences in Spain. 19,20 In order to meet power requirements (see Materials and methods) while preserving the homogeneity of the population, we included 179 unrelated patients, which met severe sepsis criteria, 22 from different Spanish localities with as similar as possible genetic backgrounds: Tenerife, one of the major islands of the Canarian Archipelago (a total of 64 patients) and different localities from Castilla (a total of 115 patients). Baseline demographic data including age, gender, risk factors to the development of infections/ sepsis (previous surgery and previous hospitalization for more than 24 h), previous morbidity (diabetes, hypertension, ischemic cardiopathy and smoking), main diagnosis (including the source of infection and pathogens) and Acute Physiology and Chronic Health Evaluation score (APACHE II) on admission were recorded (Table 1 and Supplementary Tables A-D).…”