The Colonization History of Juniperus brevifolia (Cupressaceae) in the Azores Islands

Abstract

BackgroundA central aim of island biogeography is to understand the colonization history of insular species using current distributions, fossil records and genetic diversity. Here, we analyze five plastid DNA regions of the endangered Juniperus brevifolia, which is endemic to the Azores archipelago.Methodology/Principal FindingsThe phylogeny of the section Juniperus and the phylogeographic analyses of J. brevifolia based on the coalescence theory of allele (plastid) diversity suggest that: (1) a single introduction event likely occurred from Europe; (2) genetic diversification and inter-island dispersal postdated the emergence of the oldest island (Santa Maria, 8.12 Ma); (3) the genetic differentiation found in populations on the islands with higher age and smaller distance to the continent is significantly higher than that on the younger, more remote ones; (4) the high number of haplotypes observed (16), and the widespread distribution of the most frequent and ancestral ones across the archipelago, are indicating early diversification, demographic expansion, and recurrent dispersal. In contrast, restriction of six of the seven derived haplotypes to single islands is construed as reflecting significant isolation time prior to colonization.Conclusions/SignificanceOur phylogeographic reconstruction points to the sequence of island emergence as the key factor to explain the distribution of plastid DNA variation. The reproductive traits of this juniper species (anemophily, ornithochory, multi-seeded cones), together with its broad ecological range, appear to be largely responsible for recurrent inter-island colonization of ancestral haplotypes. In contrast, certain delay in colonization of new haplotypes may reflect intraspecific habitat competition on islands where this juniper was already present.

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

“…In a recent study of Silva et al (2011) it was identified a high degree of differentiation and restricted gene flow between populations, which contradicts the accepted theories for the Azorean plant diversity with low number of radiations and low number of single-island endemics and also contradicts the life traits of this species that favours the long distance dispersal, colonization and gene flow exchange (Carine and Schaefer, 2010;Rumeu et al, 2011a;Schaefer et al, 2011).…”

“…The presence of J. brevifolia in the Azores implies one of the most remote juniper colonization known (Rumeu et al, 2011a), representing one of the best examples of endemic species displaying traits favourable for long-distance dispersal and colonization, i.e. dioecy, anemophily, zoochory, multi-seeded cone (Adams, 2011) and mesic habitats requirements (Elias, 2007).…”

Comparative phylogeography of oceanic archipelagos: Hotspots for inferences of evolutionary process

“…However, the islands are located over a complex microplate rather than a single hotspot. Nevertheless, there is some evidence for a directional mode of dispersal from older to younger islands [plants (80,81); arthropods (82,83)], although a simple progression rule is not common [yet Van Riel (84) presents intriguing evidence from gastropods]. Much of the current evidence consists of age estimates of haplotypes/alleles rather than robustly structured cladogenetic branching between islands.…”

Genetic diversity of Lithuanian populations of Juniperus communis L. in relation to abiotic and biotic factors

“…Genetic diversity of Juniperus species has been most extensively examined by RAPDs (Adams & Demeke, 1993;Adams et al, 2003;Adams, 2011;Dzialuk et al, 2011;Kasaian et al, 2011) in comparison to other molecular markers like microsatellites (Provan, 2008;Michalczyk et al, 2006;Douaihy et al, 2011;Sobierajska et al, 2016) or Amplified Fragment Length Polymorphism (Van der Merwe et al, 2000;Rumeu et al, 2011).…”