Isozyme variation and recent biogeographical history of the long‐lived conifer Fitzroya cupressoides

Abstract

Aim Palaeoenvironmental records of Pleistocene glaciation and associated vegetation changes in Patagonia have led to the hypothesis that during the last glacial maximum (LGM) tree species survived locally in favourable habitats. If present populations originated from spread from only one refugium, such as an ice‐free area of coastal Chile (Single Refugium hypothesis), we would expect that eastern populations would be genetically depauperate and highly similar to western populations. In contrast, if the ice cap was not complete and tree species persisted in forest patches on both slopes of the Andes (Multiple Refugia hypothesis), we would expect a greater degree of genetic divergence between populations either on opposite sides of the Cordillera (Cordillera Effect scenario) or towards its present‐day southern distributional limit where the ice sheet reached its maximum coverage (Extent‐of‐the‐Ice scenario). Location We tested this refugia hypothesis using patterns of isozyme variation in populations sampled over the entire modern range of the endemic conifer Fitzroya cupressoides (Mol.) Johnst. (Cupressaceae) in temperate South America. Methods Fresh foliage was collected from twenty‐four populations and analysed by horizontal electrophoresis on starch gels. Results Twenty‐one putative loci were reliably scored and 52% were polymorphic in at least one population. Populations from the eastern slope of the Andes were genetically more variable than those from the western slope; the former had a greater mean number of alleles per locus, a larger total number of alleles and rare alleles, and higher polymorphism. Genetic identities within western populations were greater than within eastern populations. Discriminant analyses using allelic frequencies of different grouping schedules of populations were non significant when testing for the Single Refugium hypothesis whereas significant results were obtained for the Multiple Refugia hypothesis. Main conclusions Our results indicate that present Fitzroya populations are the result of spreading from at least two, but possibly more, glacial refugia located in Coastal Chile and on the southern flanks of the Andes in Argentina.

Phylogeographic Structure and Cryptic Speciation in the Trans-Antarctic Moss Pyrrhobryum Mnioides

“…Although our sampling is insufficient to address this issue, a similar pattern has been found in other plants. Premoli et al (2000) report evidence for refugia on both sides of the Patagonian Andes for the endemic conifer Fitzroya, a result consistent with other work on Nothofagus (Premoli 1997;Marchelli et al 1998). Premoli et al (2000) conclude that this range fragmentation was produced by Pleistocene glaciation of the southern Andes.…”

“…Premoli et al (2000) report evidence for refugia on both sides of the Patagonian Andes for the endemic conifer Fitzroya, a result consistent with other work on Nothofagus (Premoli 1997;Marchelli et al 1998). Premoli et al (2000) conclude that this range fragmentation was produced by Pleistocene glaciation of the southern Andes. However, assuming a mid-Miocene vicariance separating Patagonia from the neotropics, as we have for other calibrations, we estimate that the Patagonia-Magellanes split in P. mnioides may have occurred 10-11 million years ago, well before the Pleistocene date suggested for Fitzroya by Premoli et al (2000).…”

“…Premoli et al (2000) conclude that this range fragmentation was produced by Pleistocene glaciation of the southern Andes. However, assuming a mid-Miocene vicariance separating Patagonia from the neotropics, as we have for other calibrations, we estimate that the Patagonia-Magellanes split in P. mnioides may have occurred 10-11 million years ago, well before the Pleistocene date suggested for Fitzroya by Premoli et al (2000). Samples from the eastern side of the Andes are needed to address whether Argentine populations of P. mnioides are sister to Magellanic populations and to fully explore the antiquity of the disjunction between east and west Andean populations.…”

Variación genética en Nothofagus (subgénero Nothofagus).

“…Además, presentaron variantes genéticas únicas las que habrían tendido a perderse por efecto fundador durante la dispersión a distancia. Estos resultados, juntamente con evidencia genética en la conífe-ra tolerante al frío alerce (Fitzroya cupressoides (Molina) Johnston), llevó a plantear por primera vez la hipótesis de refugios múltiples sensu Premoli (1998) (Premoli et al 2000). Estudios detallados a lo largo de la latitud en N. pumilio postularon que las diferencias en la historia glaciaria en el norte y el sur de la distribución de la especie afectaron diferencialmente la estructura genética poblacional.…”

Restricted gene flow across fragmented populations of Legrandia concinna, a threatened Myrtaceae endemic to south-central Chile

“…Additionally, glaciations during the Pleistocene have isolated populations both in the Andes and the Coastal range, with the result that many endemic species and genera have disjunct or localized distributions (Donoso 1993, Villagrán andLe-Quesne 1996). The effect of glaciations has been the focus of biogeographical studies and genetic evidence suggests that tree species from southern Chile and Argentina were able to survive in multiple refugia (Premoli et al 2000, Bekessy et al 2002, Torres-Díaz et al 2007). However, limited information exists on woody species inhabiting northern latitudes of central Chile.…”