Fine-scale spatial genetic structure associated with Vaccinium angustifolium Aiton (Ericaceae)

Lowbush blueberry fields in Maine are comprised of long-lived individuals, termed clones, which are wild in origin. Fields are naturally formed. It is assumed that colonization occurs by animal dispersed seed over long periods of time. Pollination is by bees that are documented as having localized short distance within and between plant flight patterns. This study tested, at the within field scale, if a positive fine-scale spatial genetic structure (SGS) could be detected. Using a ‘contiguous’ design (all touching clones within 0.35 ha of one field) and a ‘neighborhood’ design (a few focal clones in two fields surrounded by their touching neighbors) we found, using EST-PCR (Expressed-Sequence-Tag-Polymerase Chain Reaction) markers, through non-parametric, distance based methods, significant, positive spatial autocorrelation (SA) within the first distance class of 7.5 meters (r = 0.067 + 0.022; p > 0.001). Two-dimensional local spatial autocorrelation also revealed in both designs significant, positive SA in clusters of clones within 15m apart. Particularly, in the ‘contiguous’ design, 32 of the 94 clones were found within the proportion genetic similarity range of 0.53 – 0.72 (the range expected with dominant markers for half to full-sib relationships (0.65 – 0.80)). These related clusters displayed a ‘patchy’ architecture across the study area interspersed with the balance of 62 clones following a random distribution. In the ‘neighborhood’ design, AMOVA revealed significant between field (Frt = 1.6%) and within field (Fpr = 3.7%) genetic differentiation. Two possible ecological and evolutionary hypotheses are discussed that render insight into the dynamics of how these fields developed and how the high levels of genetic diversity are maintained.