Duke Norman C, Benzie John A H, Goodall John A, Ballment Elizabeth R
Australian Institute of Marine Science, PMB No. 3, Townsville MC, Queensland, 4810, Australia.
Botany Department, James Cook University of North Queensland, Townsville, Queensland, 4811, Australia.
Evolution. 1998 Dec;52(6):1612-1626. doi: 10.1111/j.1558-5646.1998.tb02242.x.
Allozyme variation in species of the mangrove genus Avicennia was screened in 25 populations collected from 22 locations in the Indo-West Pacific and eastern North America using 11 loci. Several fixed gene differences supported the specific status of Avicennia alba, A. integra, A. marina, and A. rumphiana from the Indo-West Pacific, and A. germinans from the Atlantic-East Pacific. The three varieties of A. marina, var. marina, var. eucalyptifolia, and van australasica, had higher genetic similarities (Nei's I) and no fixed gene differences, confirming their conspecific status. Strong genetic structuring was observed in A. marina, with sharp changes in gene frequencies at the geographical margins of varietal distributions. The occurrence of alleles found otherwise in only one variety, in only immediately adjacent populations of another variety, provided evidence of introgession between varieties. The varieties appear to have diverged recently in the Pleistocene and are apparently not of ancient Cretaceous origin, as suggested earlier. Despite evidence of high degrees of outcrossing, gene flow among populations was relatively low (N m < 1-2), except where populations were geographically continuous, questioning assumptions that these widespread mangrove species achieve high levels of long-distance dispersal.
利用11个基因座，对从印度 - 西太平洋和北美东部22个地点采集的25个种群的红树植物白骨壤属物种的等位酶变异进行了筛选。几个固定的基因差异支持了来自印度 - 西太平洋的白骨壤、全缘白骨壤、海榄雌和红茄苳，以及来自大西洋 - 东太平洋的拉关木的物种地位。海榄雌的三个变种，即海榄雌变种、桉叶海榄雌变种和澳洲海榄雌变种，具有较高的遗传相似性（内氏I）且没有固定的基因差异，证实了它们的同种地位。在海榄雌中观察到强烈的遗传结构，在变种分布的地理边缘基因频率有急剧变化。在仅一个变种中发现的等位基因，却出现在另一个变种的紧邻种群中，这为变种间的渐渗杂交提供了证据。这些变种似乎是在更新世最近才分化的，显然并非如早期所认为的那样起源于古老的白垩纪。尽管有高度异交的证据，但除了种群在地理上连续的情况外，种群间的基因流相对较低（Nm < 1 - 2），这对这些广泛分布的红树物种实现高水平远距离扩散的假设提出了质疑。
