THE GENETIC-BASIS OF LIFE-HISTORY CHARACTERS IN A POLYCHAETE EXHIBITING PLANKTOTROPHY AND LECITHOTROPHY
THE GENETIC-BASIS OF LIFE-HISTORY CHARACTERS IN A POLYCHAETE EXHIBITING PLANKTOTROPHY AND LECITHOTROPHY
复制标题
DOI：
10.1111/j.1558-5646.1991.tb04412.x
复制
发表时间：
1991-03-01
期刊：
影响因子：
3.3
通讯作者：
CREED, E
中科院分区：
文献类型：
--
作者：
LEVIN, LA;ZHU, J;CREED, E
多毛类 Streblospio benedicti 的不同寻常之处在于，几个野外种群由表现出浮游营养型或卵磷脂幼虫发育的个体组成。 该物种的浮游营养涉及产生许多小卵，这些卵发育成具有两到三周浮游期的摄食幼虫。 卵磷脂营养涉及产生更少、更大的卵子，这些卵子发育成不摄食的幼虫，孵化时间更长并且有短暂的浮游阶段。 进行相互交配以研究遗传变异成分以及与浮游营养型和卵磷脂营养型相关的生活史性状的相关结构。 我们的目标是更好地了解 Streblospio benedicti 以及一般海洋无脊椎动物中这种发育二分法的持续存在。 在第一次繁殖时，检测到以下性状存在显着的加性遗传变异（占总数的 75-98%）：雌性身长；第一个配子发生母猪和第一个育儿袋的位置；卵子直径；与繁殖力相关的三个性状（每个卵巢的卵子数、每个育儿袋的幼虫数和每个育儿的幼虫数）；幼虫浮游期中位数和幼虫游动刚毛的存在；但不适用于育儿袋总数；幼虫长度；幼虫进食；和幼虫的存活率。 根据该物种发育模式的不寻常地理分布，我们假设这些发育特征是在异域繁殖中进化出来的，并且最近才在北卡罗来纳州接触到。 由于（a）自然界中的非随机育种，以及（b）一次仅检查年龄结构群体的一个组成部分，许多性状对方差的高附加贡献可能会被夸大。 核相互作用方差和母体方差占幼虫存活率总变异的 84%。 这一观察结果支持了其他实证研究和理论预测，即方差的非加性成分将在与健康密切相关的个体特征中变得更加重要。 观察到了生活史性状相关性网络，该网络定义了不同的浮游营养型和卵磷脂性状复合体。 繁殖力与卵大小、繁殖力与第一个配子位置之间以及幼体存活率与中位浮游期之间存在负遗传相关性。 在繁殖力和雌性第一次繁殖时的体型之间以及浮游期和游动刚毛的存在之间检测到正向遗传相关性。 幼体长度和繁殖力、浮游期和卵大小、雌性大小和幼虫存活率、繁殖力和幼虫存活率的代际乘积矩相关性为负。 如果实验室观察到的遗传相关结构在野外持续存在，它可能会限制个体性状对方向选择的反应，并间接延续与浮游营养和卵磷脂营养相关的二分法。
The polychaete Streblospio benedicti is unusual in that several field populations consist of individuals that exhibit either planktotrophic or lecithotrophic larval development. Planktotrophy in this species involves production of many small ova that develop into feeding larvae with a two- to three-week planktonic period. Lecithotrophy involves production of fewer, larger ova that develop into nonfeeding larvae that are brooded longer and have a brief planktonic stage. Reciprocal matings were performed to investigate genetic variance components and the correlation structure of life-history traits associated with planktotrophy and lecithotrophy. Our objective was to better understand persistence of this developmental dichotomy in Streblospio benedicti, and among marine invertebrates in general. Substantial additive genetic variation (75-98% of total) was detected for the following characters at first reproduction: female length; position of the first gametogenic setiger and first brood pouch; ovum diameter; three traits related to fecundity (numbers of ova per ovary, larvae per brood pouch, and larvae per brood); median larval planktonic period and the presence of larval swimming setae; but not for total number of brood pouches; larval length; larval feeding; and larval survivorship. Based on the unusual geographic distribution of development modes in this species, we hypothesize that the developmental traits have evolved in allopatry and have only recently come into contact in North Carolina. The high additive contribution to variance observed for many traits may be inflated due to (a) nonrandom breeding in nature, and (b) examination of only one component of an age-structured population at one time. Nuclear interaction variance and maternal variance accounted for 84% of the total variation in larval survivorship. This observation supports other empirical studies and theoretical predictions that nonadditive components of variance will increase in importance in individual traits that are most closely tied to fitness. A network of life-history trait correlations was observed that defines distinct planktotrophic and lecithotrophic trait complexes. Negative genetic correlations were present between fecundity and egg size, between fecundity and position of the first gametes, and between larval survivorship and median planktonic period. Positive genetic correlations were detected between fecundity and female size at first reproduction and between planktonic period and the presence of swimming setae. Intergenerational product-moment correlations were negative for larval length and fecundity, planktonic period and egg size, female size and larval survivorship, and fecundity and larval survivorship. If the genetic correlation structure observed in the laboratory persists in the field, it may constrain responses of individual characters to directional selection, and indirectly perpetuate the dichotomies associated with planktotrophy and lecithotrophy.