厦门文昌鱼(Branchiostoma belcheri Gray)种群杂合性研究

HETEROZYGOSITY OF FOUR POPULATINONS OF BRANCHIOSTOMA BELCHERI GRAY IN XIAMEN

应用聚丙烯凝胶电泳技术,研究了厦门海域四个野生文昌鱼种群的杂合度缺乏和过量情况。在测定的7个酶系统中,共有14个等位酶基因位点,分别为Aat-1、Amy-1、Amy-2、Amy-3、Amy-4、Me-1、Me-2、Mdh-1、Mdh-2、Sod-1、Sod-2、Est-1、Est-2、Per-1。多态位点有8个,分别为Sod-1、Aat-1、Me-1、Me-2、Mdh-1、Mdh-2、Est-2、Amy-2。结果表明,在大嶝岛种群、南线至十八线东端种群、南线至十八线西端种群及黄厝种群中,多态位点Sod-1、Mdh-2、Me-2、Aat-1显著偏离H-W平衡标准(P<0.05),而位点Me-1、Mdh-1、Est-2符合H-W平衡标准(P>0.05)。多态位点Amy-2除南线至十八线东端种群显著偏离H-W平衡标准(P<0.05)外,其它三个种群的多态位点Amy-2均符合H-W平衡标准(P>0.05)。在所有的8个多态位点中,只有大嶝岛和黄厝两个种群的Amy-2位点表现为杂合子缺失(F>0),其它种群的多态位点均表现为杂合子过量(F<0)。造成杂合体缺失的主要原因可能是自然选择、近交、哑等位基因等。杂合体的缺失会导致某些基因从该物种的基因库中消失,从而降低了物种的遗传多样性,同时也使物种对环境的适应能力降低。

Heterozygosity of Branchiostoma belcheri Gray in Xiamen was investigated using vertical slab polyacrylamide gel electrophoresis. Seven enzymes presumably encoded by 14 allozyme loci in B. belcheri. They are Aat-1, Amy-l, Amy-2, Amy-3, Amy-4, Me-l, Me-2, Mdh-1, Mdh-2, Sod-l, Sod-2, Est-1, Est-2, and Per-l, of which 8 loci are polymorphic, they are Sod-l, Aat-1, Me-l, Me-2, Mdh-1, Mdh-2, Est-2, Amy-2. The genotypic distribution observed at Me-l, Mdh-1 and Est-2 in all populations and Amy-2 in East of Southern line to 18 population was in agreement with those expected by the Hardy-Weinberg equilibrium （HWE） （P〉0.05）; but Sod-l, Mdh-2, Me-2 and Aat-1 loci in all populations and Amy-2 in other three populations were significant departed from those expected from HWE （P〈0.05）. Heterozygote deficiency in Amy-2 locus in East of Southern line to 18 and Huangcuo populations （F〉0） and heterozygote excess in other polymorphic loci （F〈0） were also revealed among populations. The heterozygote deficiency resulting from natural selection, inbreeding effects, presence of null allele and so on would cause disappearance of allele, lower genetic diversity and lower environmental adaptation ability.