水筆仔(Kandelia candel (L.) Druce)，屬紅樹科(Rhizophoraceae)，係紅樹科中單種屬(monotypic species)的胎生植物。水筆仔因族群內的基因流傳未受限制，致未產生遺傳上的分化。本研究的目的即在探討水筆仔族群內的基因流傳模式，以已知個體的同功酵素表現型為基礎，設計授粉實驗，以確切了解其配對系統(mating system)，同時並檢查已知個體在自然狀況下的結實率和果實基因型，以確認其遺傳模式。
本實驗在淡水竹圍的紅樹林內進行。傳粉生物學的實驗結果顯示，水筆仔的結實率偏低(12.6%)，其自交比例(inbreedingrate)也很低(套袋結實率=2.2%)。以具有多型性的基因座(TPI-2，PGM-1，PGM-2)來計算其異配比例(outcrossing rate)亦證實水筆仔的配對系統偏向異交(outcrossing)。另外，使用同功酵素TPI標幟檢查水筆仔前後代遺傳變異的結果証明，TPI-2的配比符合孟德爾遺傳律，可以作為遺傳變異的指標。

Kandelia candel (L.) Druce, is a monotypic-genus species of Rhizophoraceae. Because gene flow of K. candel within population is not restricted, the level of genetic differentiation among subpopulations is low. The purposes of this study is to research the gene flow model within population of K. candel, desigh pollination experiment to understand the specie's mating system based on isozyme phenotypes of individuals, and check fruiting rate and fruit's genotype of individuals under nature conditions in order to prove their genetic model.
The experiments are hold in the mangrove of Chuwei, along the Tannsui River. The experiment results of pollination biology show that the fruiting rate of K. candel is low (12.6%) and it's inbreeding rate is low (netted fruiting rate = 2.2%), too. Using the polymorphic alleles (TPI-2, PGM-1, PGM-2) to caculate the outcrossing rate also proves that the mating system of K. candel is dominantly outcrossing. Additional, using TPI as a genetic marker to compare the genetic variation between paternal and progeny generations prove that the distribution of TPI-2 is in accord with Model's principles, and can be used as a marker of genetic variation.