Quaternary evolutionary history of Austrocedrus chilensis, a cypress native to the Andean–Patagonian forest

Abstract

Aim The Quaternary life history of a species determines its current range and the degree and distribution of its present genetic variation. Past climates, ecological relationships and disturbances in connection to evolutionary factors have determined the genetic and geographical distribution patterns of the current vegetation, and consequently, evolutionary processes can be inferred from those patterns. The aim of the present study is to find a plausible evolutionary explanation for the current natural range and genetic variation patterns of Austrocedrus chilensis (D. Don) Florin et Boutelje in Argentina.Location The studied species ranges naturally over a narrow strip not wider than 50 km that runs parallel to the Cordillera de los Andes from 32°39¢ S in Chile to 43°44¢ S in Argentina. The studied populations are located in the Argentine range, especially in its central part.Methods Information on palynological data, current geographical distribution and on amount and distribution of genetic variation of the species in Argentina was the basis for an integrating analysis and discussion.Results Palynological evidence of the past reported the presence of A. chilensis before and immediately after last glaciation on the east side of the Andes. The most conspicuous present populations of A. chilensis are located in areas that were covered by ice during the Last Glacial Maximum. The allelic multiplicity and diversity as well as the population differentiation of the species in Argentina were shown to be small, while the levels of heterozygosity were moderate. A latitudinal gradient trend was recognized as a pattern of distribution of variation in Argentina, the northerly populations being more variable. Extreme marginal populations located in the steppe, out of the glaciated area, show the greatest levels of variation.Main conclusions Evidence was shown supporting that the major factor responsible for the variation pattern found in A. chilensis were the glacial processes. In the Argentine side of the Cordillera de los Andes the species could survive only in a narrow strip between the coldness of the ice sheet and the dryness of the steppe. That implies a generalized genetic drift process. Multiple small refuges in the eastern side of the Cordillera are hypothesized where this cypress would have survived to glaciation. Those refuges are postulated to have been chiefly localized slightly eastward to the present distribution area and most probably in a northern location, at least from 42°S of latitude to the north.

Seasonal Variation and Resin Composition in the Andean Tree Austrocedrus chilensis

“…Principal Component Analysis was carried out to explain the relation of the p = 12 original compounds (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12) in r < p components. It allows an optimal representation in a smaller dimensional space (r) of the multivariate problem (p).…”

“…The distribution range of A. chilensis covers two wide parallel areas in the Cordillera de los Andes, in both sides of the mountain range in Chile and Argentina. It includes the west Andean populations in the Mediterranean region of Chile, east Andean populations ranging from humid rain forest to the steppe ecotone and coastal mountain populations from Mediterranean Chile [1][2][3]. This species is more common in the eastern Andes (Argentina), where the wide precipitation gradient ranges from 2500 to 4000 mm per year [3].…”

Robles in Lagunas de Epulauquen, Argentina: previous and recent evidence of their distinctive character

“…Genetic studies in N. obliqua forests (Azpilicueta et al 2009) and other South American temperate tree species (e.g. Marchelli et al 1998;Premoli et al 2000;Bekessy et al 2002;Pastorino and Gallo 2002;Allnut et al 2003;Azpilicueta et al 2009;Marchelli et al 2010) give support to this multiple refugia hypothesis.…”

Heterogeneous genetic structure in a natural population of Raulí (Nothofagus nervosa)

“…Although this assumption may be reasonable for many species, it may not be valid for long-lived temperate forest trees whose ranges have changed considerably due to the last glacial cycle (Yacine and Lumaret, 1989;Leonardi and Menozzi, 1995;Villagrán, 1991;Aldrich et al, 2005). The current distribution range for N. nervosa on the Chilean side is considered a plant refugia in the last glacial period (Villagran, 1991;Carrasco and Eaton, 2002;Pastorino and Gallo, 2002;Premoli et al, 2002). Long-living tree species in the southern temperate forests in Chile show a genetic fragmentation that could be a consequence of their geographic fragmentation during that ice period (Torres-Diaz et al, 2007) and the re-colonization process after the glacial periods (Marchelli and Gallo, 2004).…”