Genetic structure and diversity ofPolylepis australis(Rosaceae) tree populations from central Argentina: Implications for forest conservation

Abstract

Worldwide, large areas of forest are being transformed to other land cover types and the resulting fragmented populations may suffer from restricted gene flow leading to genetic pauperization and increased inbreeding. To assess the genetic constitution of fragmented Polylepis australis mountain forests of central Argentina, analyses of the structure and diversity of ISSR markers were carried out for 90 trees distributed throughout five river basins with differing degrees of fragmentation. Overall, average polymorphism (P) ranged between 87.2 and 94.9% (95% criterion) while marker diversity index (M) varied between 0.35 and 0.39; values which are comparable with other wind-pollinated tree species. Analysis of molecular variance (AMOVA) revealed that most genetic variation occurred within river basins (97.8%), with only a little occurring between river basins (2.2%; ΦST = 0.02). In addition, Mantel’s test indicated that P. australis does not follow the usual pattern of isolation by distance; instead the UPGMA method showed that trees from the two most degraded river basins formed a group while trees from the three better preserved basins formed another. As such, either effective pollen flow has maintained high levels of genetic diversity, or present day genetic variability is a remnant of a recently fragmented ancestral panmictic population. We conclude that, at present, genetic degradation in P. australis populations of central Argentina is not as important as ecological degradation – such as soil loss, intensive browsing by livestock or increased frequencies of wildfires, and that genetic variability is still fully available for forest restoration.

No effect of elevation and fragmentation on genetic diversity and structure in Polylepis australis trees from central Argentina

“…; Julio et al . ), and it is in accordance with several reviews which showed that wind‐pollinated tree species have a high proportion of genetic variability within populations and clearly lower diversity among populations (Hamrick ; Nybom ). The results confirm that extensive gene flow connects populations along the elevational gradient.…”

“…In addition, using ISSR and AFLP markers respectively Julio et al . () and Hensen et al . () reported very little genetic divergence of older trees between different P. australis populations.…”

Genetic diversity of AndeanPolylepis(Rosaceae) woodlands and inferences regarding their fragmentation history

“…§Estimated as the average of the marker diversity index (M) obtained per population. ¶Estimated using data from Renison et al (2006) and Julio et al (2011). the fact that the second most important component of the genetic variation was the among-regions component, which contained 9.5% of the genetic variation, despite the short distances between regions (c. 1.7 km). This differentiation might be caused by the mountain range and valley present between regions which divide the landscape.…”

Prediciendo la distribución de Polylepis: bosques Andinos vulnerables y cada vez más importantes

“…Además, la reforestación con especies no nativas de Polylepis puede conducir a la pérdida local de la diversidad genética de la hibridación, como otras especies relacionadas se sabe que se hibridan con facilidad . La buena noticia es que gran cantidad de flujo de genes entre ellas y dentro de muchas poblaciones de Polylepis existe y la variabilidad genética parece estar plenamente disponible para la restauración forestal en muchas áreas (Julio et al 2011). Una posible estrategia es la recolección de semillas de múltiples fragmentos grandes y de individuos separados por al menos 25 m dentro de los fragmentos para maximizar la diversidad genética para reforestación (Quinteros-Casaverde et al 2012).…”