Genetic diversity and population structure of the endemic Azorean juniper, Juniperus brevifolia (Seub.) Antoine, inferred from SSRs and ISSR markers

• Both marker systems results were strongly correlated with each other.
• Both marker systems results were not dependent on population sample size.
• Was observed moderate to high genetic diversity, low to moderate genetic differentiation.
• Was observed that the genetic diversity was mostly within populations.
• Was observed positive fixation indexes and high gene flow.

Juniperus brevifolia is an important woody species endemic of the Azores archipelago (Portugal), found from coastal to mountain environments. Due to colonization and grazing pressure this species has suffered fragmentation, leading to extinction in one island and being threatened in others. The genetic diversity and population structure of J. brevifolia populations was studied to provide guidelines for restoration and conservation programmes. Nuclear Single Sequence Repeats (nSSR) from Juniperus communis and Juniperus przewalskii and Inter Simple Sequence Repeats (ISSR) were tested and results compared to test the transferability of the microsatellites to J. brevifolia. Samples from ten populations over three islands, divided as coastal, mid-altitude and mountain were analysed. Both marker systems revealed results statistically and strongly correlated with each other, and not dependent on population sample size. We observed positive fixation indexes, moderate to high levels of genetic diversity (h = 0.415 for nSSR and h = 0.245 for ISSR), low to moderate φpt genetic differentiation (0.070 for nSSR and 0.129 for ISSR) and high gene flow (Nm > 2.432). Regarding Nei's genetic distance the coastal communities clustered together reflecting the phenotypic plasticity, but no specific clustering was observed regarding φpt values. Therefore no populations with substantial genetic differentiation were identified, once the diversity is mostly observed within populations. However it is advised the continuous monitoring of J. brevifolia.