The results indicate that geographical isolation has represented a major barrier to gene flow in Juniperus phoenicea. This work represents a first step towards a full genetic characterization of a conifer from the Mediterranean, a world biodiversity hotspot confronted with climate change, and thus contributes towards the planning of genetics-informed conservation strategies.

Many plant species combine sexual and clonal reproduction. Clonal propagation has ecological costs mainly related to inbreeding depression and pollen discounting; at the same time, species able to reproduce clonally have ecological and evolutionary advantages being able to persist when conditions are not favorable for sexual reproduction. The presence of clonality has profound consequences on the genetic structure of populations, especially when it represents the predominant reproductive strategy in a population. Theoretical studies suggest that high rate of clonal propagation should increase the effective number of alleles and heterozygosity in a population, while an opposite effect is expected on genetic differentiation among populations and on genotypic diversity. In this study, we ask how clonal propagation affects the genetic diversity of rare insular species, which are often characterized by low levels of genetic diversity, hence at risk of extinction. We used eight polymorphic microsatellite markers to study the genetic structure of the critically endangered insular endemic Ruta microcarpa. We found that clonality appears to positively affect the genetic diversity of R. microcarpa by increasing allelic diversity, polymorphism, and heterozygosity. Moreover, clonal propagation seems to be a more successful reproductive strategy in small, isolated population subjected to environmental stress. Our results suggest that clonal propagation may benefit rare species. However, the advantage of clonal growth may be only short-lived for prolonged clonal growth could ultimately lead to monoclonal populations. Some degree of sexual reproduction may be needed in a predominantly clonal species to ensure long-term viability.

Citing articles: 13 View citing articles Ital. J. Zool., 69-295-300 (2002) ABSTRACT An investigation of the genetic variability of Octopus vulgaris, an intensively harvested species, was carried out using a microsatellite locus as genetic marker. Samples from one eastern Atlantic and nine Mediterranean locations were analysed. In each population, the number of alleles at locus Ov06 varied from four to seven and was 21 overall. Observed and expected heterozygosity values ranged from 0.310 to 0.655 and 0.506 to 0.841, respectively. Permutation tests and the positive average value of F IS showed significant departures from the Hardy-Weinberg equilibrium, due to a deficit of heterozygotes. F ST showed high levels of genetic divergence among the populations. Genetic distance values ranged from 0.0004 to 7.1520. Isolation-by-distance was not evident either by the Mantel test or multidimensional scaling. Microsatellite results are consistent with a previous allozyme study, and suggest that the common octopus does not form a single panmictic unit in the Mediterranean. From a fishery perspective, this information leads to the conclusion that the management of O. vulgaris should be planned on a local level.

Despite the restricted range, C. horrida displays high levels of genetic diversity, structured in such a way that three management units could be deemed viable for its conservation. The protected status of the species will probably suffice to prevent the impoverishment of its genetic resources.