Microsatellite analysis of the regeneration process of Magnolia obovata Thunb

Abstract

We analysed the regeneration process of Magnolia obovata using polymorphic microsatellite markers. Eighty-three adult trees standing in a watershed covering an area of 69 ha, and saplings collected from a smaller research plot (6 ha) located at the centre of the watershed were genotyped using microsatellite markers. Among 91 saplings analysed, 24 (26%) had both parents, 31 (34%) had one parent and 36 (40%) had no parent within the watershed. The proportion of genes in saplings inherited from the adults within the watershed was 43%, and therefore 57% were from outside the site, indicating active gene exchange across the watershed area. Average distance between parents and saplings (264.6 +/- 135.3 (SD) m) was significantly smaller than that of pairs randomly chosen between adults and saplings (436.7 +/- 203.0 (SD) m). The distance of pollen movement inferred from the distance between the two parents of each sapling ranged from 3.2 m to 540 m with an average of 131.1 m +/- 121.1 m (SD). Because 34% ( = 31/91) of saplings had only one parent within the watershed, the estimate of average pollen movement must be smaller than the actual one. Long-distance seed dispersal by birds, inbreeding depression and limitation in acceptance of pollen because of the difference of phenology in each individual flower were considered to be the probable causes of large gene exchange across the watershed.

Effect of gene flow on spatial genetic structure in the riparian canopy tree Cercidiphyllum japonicum revealed by microsatellite analysis

“…Recently, highly polymorphic microsatellite markers have become a popular genetic tool in ecological studies, and have been utilized for various analyses, such as parentage analysis to identify realized contemporary gene flow (Dow and Ashley, 1996;Isagi et al, 2000;Kameyama et al, 2001;Jones and Ardren, 2003), detection of fine-scale genetic structure (Streiff et al, 1998;Ueno et al, 2000;Kameyama et al, 2002), and the analysis of amongpopulation genetic structure (Kikuchi and Isagi, 2002;Heuertz et al, 2004). In this study, we used five nuclear microsatellites for genetic analyses at different spatial scales.…”

Determination of genetic relatedness of selected individual trees of Shorea leprosula Miq. and Dipterocarpus cornutus Dyer in forest seed production areas

“…This implies gene flow occurred in this species within the SPA. Isagi et al (2000) found that about 57% of the possible parents of Magnolia obovata saplings were from outside the study plot in Ogawa Forest Reserve revealed by eight SSR loci.…”

“…According to Isagi et al (2000), if a population is genetically structured and inbreeding or outbreeding depression occurs, as indicated by the genetic relatedness of adult trees, some kind of selection on pollen grains could have occurred. Dow and Ashley (1996) presumed the existence of a mechanism allowing female flowers of Quercus macrocarpa to preferentially select pollen from distant sources rather than pollen produced by neighbouring trees.…”

“…In the case of episodic flowering without synchronisation in a population, only some of the trees in a population can contribute to reproduction in a given year and this may have resulted from pollination between distant trees. Isagi et al (2000) reported that more than 70% of the pollination events in Magnolia obovata occurred between non-nearest neighbours.…”

“…This result suggests that these mother trees are probably their parents. Nevertheless, there are possibilities that these alleles detected in saplings may also come from S. leprosula mother trees outside the S. leprosula SPA Isagi et al (2000), more than 70% of the pollination events in M. obovata occurred between non-nearest neighbours. In fact, the average mating distance, 524 m, has been reported in N. heimii based on five reproductive trees in Pasoh Forest Reserve, a lowland tropical rainforest in Malaysia (Konuma et al 2000).…”