Phylogeography of the invasive weed Hypochaeris radicata (Asteraceae): from Moroccan origin to worldwide introduced populations.

In an attempt to delineate the area of origin and migratory expansion of the highly successful invasive weedy species Hypochaeris radicata, we analysed amplified fragment length polymorphisms from samples taken from 44 populations. Population sampling focused on the central and western Mediterranean area, but also included sites from Northern Spain, Western and Central Europe, Southeast Asia and South America. The six primer combinations applied to 213 individuals generated a total of 517 fragments of which 513 (99.2%) were polymorphic. The neighbour-joining tree presented five clusters and these divisions were supported by the results of Bayesian analyses: plants in the Moroccan, Betic Sierras (Southern Spain), and central Mediterranean clusters are all heterocarpic. The north and central Spanish, southwestern Sierra Morena, and Central European, Asian and South American cluster contain both heterocarpic (southwestern Sierra Morena) and homocarpic populations (all other populations). The Doñana cluster includes two homocarpic populations. Analyses of fragment parameters indicate that the oldest populations of H. radicata are located in Morocco and that the species expanded from this area in the Late Quaternary via at least three migratory routes, the earliest of which seems to have been to the southwestern Iberian Peninsula, with subsequent colonizations to the central Mediterranean area and the Betic Sierras. Homocarpic populations originated in the southwestern Iberian Peninsula and subsequently spread across north and central Spain, Central Europe and worldwide, where they became a highly successful weed.

Population structure of Hypochaeris salzmanniana DC. (Asteraceae), an endemic species to the Atlantic coast on both sides of the Strait of Gibraltar, in relation to Quaternary sea level changes.

To detect potential Pleistocene refugia and colonization routes along the Atlantic coast, we analysed amplified fragment length polymorphisms (AFLPs) in 140 individuals from 14 populations of Hypochaeris salzmanniana (Asteraceae), an annual species endemic to the southwestern European and northwestern African coastal areas. Samples covered the total distributional range of the species, with eight populations in southwestern Spain and six populations in northwestern Morocco. Using nine primer combinations, we obtained 546 fragments in H. salzmanniana and its sister species H. arachnoidea of which 487 (89.2%) were polymorphic. The neighbour-joining tree shows that the populations south of the Loukos river in Morocco are clearly differentiated, having more polymorphic, private, and rare fragments, and higher genetic diversity, than all the other populations. The southernmost populations in Morocco, south of the river Sebou, form a large panmictic population. They are probably the oldest populations that have been relatively unaffected by stochastic processes resulting from Pleistocene glaciations. Northward migration of populations during this period may have resulted in loss of genetic diversity in specific regions, perhaps due to bottlenecks caused by rise in sea level during interglacial periods, and, in some cases, by changes in the breeding system.

Pleistocene refugia and recolonization routes in the southern Andes: insights from Hypochaeris palustris (Asteraceae, Lactuceae).

Hypochaeris palustris (Phil.) De Wild. is a species growing in the southern Andean chain. To elucidate potential Pleistocene refugia and recolonization routes in the southern Andes, we analysed amplified fragment length polymorphisms (AFLPs) in 206 individuals in 21 populations of H. palustris from the coastal Cordillera, the central, northern, and eastern ranges of the southern Andes, and Patagonia. Populations from the coastal Cordillera harboured more private AFLP fragments, and exhibited a higher frequency of polymorphic fragments as well as higher Shannon diversity than all other areas investigated. The comparison among pooled AFLP profiles of each region revealed that the central Andean ranges shared most fragments with populations from the margins of the distributional area in the Andes, in the N, E, and S (Patagonia). Phenetic analysis indicated close relationships among populations of the central ranges. Populations of the coastal Cordillera were shown to be highly differentiated from the Andean populations. It is very likely therefore that (1) H. palustris recolonized the central ranges of the southern Andes from nearby refugia, possibly unglaciated areas N, E, and/or S of its present distributional area; (2) the postglacial spread of H. palustris in the central ranges of the southern Andes occurred rapidly; and (3) the coastal Cordillera served as a refugium for H. palustris, but these populations did not contribute to the recolonization of the central Andean ranges.

Genetics of colonization in Hypochaeris tenuifolia (Asteraceae, Lactuceae) on Volcán Lonquimay, Chile.

Understanding the genetics of colonizing populations has been, and continues to remain, an important focus in evolutionary biology. Different theoretical models predict varying levels of genetic variation in colonizing populations depending upon strength of founder effect, gene flow and rate of population growth and immigration following colonization. We analyse overall genetic variation using amplified fragment length polymorphism markers in colonizing populations of Hypochaeris tenuifolia (Asteraceae) in the southern Andes. Volcán Lonquimay newly erupted on 25 December 1988, producing a side cone, La Navidad, and sent lava and ash into surrounding areas. Many domesticated animals (estimated at 10 000) and many natural plant populations were destroyed. Into this new open habitat have come immigrant populations of several angiosperm species, most conspicuously H. tenuifolia that forms leaf rosettes with flowering scapes to 15 cm and orange-yellow heads 1-2 cm in diameter. Genetic diversity in five founder populations in the eruption zone is compared with that from five nearby survivor populations, as well as with eight isolated northern and four southern populations from throughout the entire range of the species in Chile. Results from 477 individuals representing 447 different multilocus phenotypes, yielded 170 DNA fragments of which 144 (85%) were polymorphic. Genetic diversity within founder populations is neither lower than in survivor populations nor in isolated populations throughout the range of the species, but it is lower among founder populations than among other populations immediately and distantly outside the zone of disturbance. Closest genetic similarity occurs between founders and nearby survivor populations as well as those in adjacent southern regions.