Restricted gene flow in fragmented populations of a wind-pollinated tree

Abstract

Fragmentation of natural populations can have negative effects at the genetic level, thus threatening their evolutionary potential. Many of the negative genetic impacts of population fragmentation can be ameliorated by gene flow and it has been suggested that in wind-pollinated tree species, high or even increased levels of gene flow are a feature of fragmented populations, although several studies have disputed this. We have used a combination of nuclear microsatellites and allele-specific PCR (AS-PCR) analysis of chloroplast single nucleotide polymorphisms (SNPs) to examine the levels and patterns of genetic diversity and population differentiation in fragmented populations of juniper (Juniperus communis) in Ireland and inform conservation programs for the species. Significant population differentiation was found for both chloroplast and nuclear markers, indicating restricted gene flow, particularly over larger geographic scales. For conservation purposes, the existence of genetically distinct clusters and geographically localised chloroplast haplotypes suggests that the concept of provenance should be taken into account when formulating augmentation or reintroduction strategies. Furthermore, the potential lack of seed dispersal and seedling establishment means that ex-situ approaches to seed and seedling management may have to be considered.Peer reviewe

Sex allocation, pollen limitation and masting in whitebark pine

“…Bark beetles are epidemic on several conifer species in western North America (Meddens, Hicke & Ferguson 2012), and globally high plant mortality is linked to biotic attack and climate stressors (McDowell et al 2011). High tree mortality reduces stand density and isolates populations, while fragmented populations experience increased pollination limitation (O 'Connell, Mosseler & Rajora 2006) and reduced gene flow (Jump & Penuelas 2006;Provan et al 2008). Masting is a common plant reproductive strategy, especially among wind-pollinated trees (Herrera et al 1998).…”

Genetic Variability and Differentiation Among Populations of the Azorean Endemic Gymnosperm Juniperus brevifolia: Baseline Information for a Conservation and Restoration Perspective

“…In Crytocarya aschersoniana Mez (Lauraceae), F ST values ranged between 0.279 and 0.395 (Moraes and Derbyshire 2003). For J. communis, a species closely related to J. brevifolia, Provan et al (2008) reported an average value of 0.103 in fragmented populations. Additionally, for J. phoenicea, a G ST value of 0.12 was observed (Meloni et al 2006).…”

“…Fragmentation may increase isolation due to the decrease in population numbers and loss of connectivity. This in turn will lead to losses in genetic diversity due to inbreeding and restricted gene flow (Provan et al 2008). São Miguel and São Jorge populations may be experiencing a bottleneck effect caused by human interference in the last 500 years, with subsequent loss of genetic diversity.…”

Unique genetic variation at a species' rear edge is under threat from global climate change

“…AS-PCR primers were designed as described by Provan et al [34] and are given in table S2 in the electronic supplementary material. The AS-PCR protocol was as follows: initial denaturation at 948C for 3 min followed by 11 touchdown cycles of denaturation at 948C for 1 min, annealing at 658C for 1 min (20.78C per cycle), extension at 728C for 1 min followed by 24 cycles of denaturation at 948C for 1 min, annealing at 588C for 1 min, extension at 728C for 1 min and a final extension at 728C for 5 min.…”