1. ¹Laboratory of Forest Ecology and Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
2. ²Ecological Genetic Laboratory, Department of Forest Genetics, Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, Japan
3. ³Kitakyushu Museum of Natural History and Human History, Kitakyushu, Japan
4. ⁴Nagoya University, Nagoya, Japan

Correspondence: Professor N Tomaru, Laboratory of Forest Ecology and Physiology, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan. E-mail: tomaru@agr.nagoya-u.ac.jp

Received 23 March 2008; Revised 5 August 2008; Accepted 25 August 2008; Published online 24 September 2008.

Abstract

We evaluated the effects of seed- and pollen-mediated gene dispersal on genetic structure among Quercus salicina saplings. Parentage analysis using 10 microsatellite markers indicated that the 111 adult trees located within a 11.56 ha plot in the Tatera Forest Reserve, Japan, included only one parent of 44.2% and both parents of 40.7% of the 226 saplings located in a 1-ha core plot at its center. Coancestry (F_ij) estimates indicated that there was strong genetic structure among the saplings. The numbers of pairs of full- and half-siblings were high among neighboring saplings, suggesting that there was strong maternal half-sibling family structure among the saplings around their seed parents, probably generated by the spatially limited seed dispersal and the small extent of overlapping seed shadows owing to the low density of adults. The frequencies also suggest that the maternal half-sibling families are interspersed with full-siblings, produced by correlated mating, probably because pollination frequency depends on the distance between parents. The frequencies of pairs of half-siblings decreased as the distance between saplings increased, but did not fall to zero even at distances up to the 90–95 m class, suggesting that paternal half-siblings originating from correlated paternity were widely distributed owing to extensive pollen flow. We separately examined the genetic structure for maternal and paternal alleles in the saplings. Unsurprisingly, very strong genetic structure was detected for maternal alleles. However, weak (but significant) genetic structure was also detected for paternal alleles. Therefore, pollen dispersal may affect the extent of genetic structure as well as seed dispersal.