Spatial genetic structure in the Laperrine's olive (Olea europaea subsp. laperrinei), a long-living tree from the central Saharan mountains

Abstract

The Laperrine's olive (Olea europaea subsp. laperrinei) is an emblematic species of the Sahelo-Saharan Mountains. Populations of this tree are locally threatened by extinction due to climatic vicissitudes and human activities, particularly in Niger and Algeria. In order to study the spatial genetic structure and the dynamics of O. e. laperrinei populations, we sampled trees in four isolated mountain ranges (Tassili n'Ajjer and Hoggar (Algeria), Tamgak and Bagzane (Niger)). A total of 237 genets were identified using nuclear microsatellites. Phylogenetic reconstruction based on plastid DNA data supported a maternal origin of O. e. laperrinei populations in South Algeria, where a higher allelic richness was observed. Based on nuclear microsatellite data, two levels of structure were revealed: first, individuals from Niger and Algeria were separated in two distinct groups; second, four less differentiated clusters corresponded to the four studied mountain ranges. These results give support to the fact that desert barriers have greatly limited long distance gene flow. Within populations, pairwise kinship coefficients were significantly correlated to geographical distance for Niger populations but not for Algerian mountains. Historical factors and habitat heterogeneity may explain the differences observed. We conclude that the Hoggar acts as an important genetic reservoir that has to be taken into account in future conservation programmes. Moreover, very isolated endangered populations (for example, Bagzane) displaying evident genetic particularities have to be urgently considered for their endemism.

Are ferns in arid environments underestimated? Contribution from the Saharan Mountains

“…However, a number of isolated plant communities with a large range of water requirements have been described recently from the highest peaks of the Aïr (Anthelme et al, 2008a), suggesting that other ferns might also be able to colonize these habitats. Their conservation value may be particularly high, especially because isolation from their main range of distribution following climatic vicissitudes (Maley, 1980) may have led to genetic adaptations, as shown for other taxa in this region (Besnard et al, 2007).…”

Elevation and local refuges ensure persistence of mountain specific vegetation in the Nigerien Sahara

“…As an example, one of the few molecular studies led in the area on Olea europaea subsp. laperrinei, an endemic, endangered species of the Saharo-Sahelian mountains (Supplementary Materials 1 and 2), showed high genetic divergence among populations of the Saharan mountains (Besnard et al, 2007) and within the Aïr region specifically (Anthelme et al, 2008). This was attributed to the isolating effects of the inselberg structure of the Aïr mountains (see also Burke, 2003) as well as the positive effects of local abiotic refuges on plant survival.…”

Recent developments in olive (Olea europaea L.) genetics and genomics: applications in taxonomy, varietal identification, traceability and breeding

“…Several pseudogenic ribosomal regions were then identified in the Olive complex (Besnard et al 2007b). The first ITS (ITS1) of a pseudogene type was successfully isolated by Hess et al (2000) and Besnard et al (2007a), and used to investigate phylogenetic relationships between Macaronesian olives or to identify subspecies (and hybrids) in the invasive range (Australia and Hawaii). A phylogenetic study of the whole olive complex based on this pseudogene was also proposed by Besnard et al (2007b).…”