Outbreeding lethality between toxic Group I and nontoxic Group III Alexandrium tamarense spp. isolates: Predominance of heterotypic encystment and implications for mating interactions and biogeography.
Outbreeding lethality between toxic Group I and nontoxic Group III Alexandrium tamarense spp. isolates: Predominance of heterotypic encystment and implications for mating interactions and biogeography.
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DOI：
10.1016/j.dsr2.2009.09.005
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发表时间：
2010-02
影响因子：
3
通讯作者：
Anderson, Donald M.
中科院分区：
文献类型：
--
作者：
Brosnahan, Michael L.;Kulis, David M.;Solow, Andrew R.;Erdner, Deana L.;Percy, Linda;Lewis, Jane;Anderson, Donald M.
关键词：
我们报道了分布在不同地理位置的双鞭毛藻物种复合体tamarense Alexandrium的合子囊，特别是，有毒的I群和无毒的III群分离物成功交配。然而，在I/III组共培养中产生的催眠受精卵在发芽后完成不超过三个分裂。先前的报告提出了一种配偶识别机制，即共培养中产生的催眠合子可能来自同型（近交）或异型（远交）配子对。为了确定每个发生的程度，开发了巢式PCR测定来确定单个催眠受精卵的亲代。绝大多数来自I/III组共培养的催眠受精卵是近交的，因此无活力是杂交而不是近交的结果。这些发现支持了完整的物种形成是塔玛兰Alexandrium tamarense物种复合体系统发育结构的基础。此外，杂种和单核型催眠受精卵的核糖体DNA （rDNA）拷贝数比单倍体运动细胞显著减少。rDNA位点的破坏可能对遗传上遥远的接合子的成功交配至关重要，并且似乎是包囊过程中不可或缺的一部分。第一类/第三类杂交种的不能生存对公共卫生很重要，因为杂交种囊肿的存在可能表明无毒种群正在被有毒种群取代（反之亦然）。杂种不育也提示了一种控制华的策略，即通过引入无毒的III组细胞来减轻持续的、有毒的I组华。采用巢式PCR法对来自北爱尔兰贝尔法斯特湖的催眠受精卵进行了自然杂交的可能性研究，该地区是I群和III群共存的地区。在14次成功的分析中发现了两个杂交囊肿，表明I群和III群在该地区确实存在杂交。然而，对18年来收集的交配数据的分析表明，核糖体物种（包括类群I和类群III）之间的交配前屏障存在漏洞。观察到的选择性在自然界中是否抑制杂交取决于其机制。如果选择性的重点是诱导配子体发生，不同的核型可以自由杂交，在杂交是致命的情况下促进位移。相反，如果选择性发生在配子对的粘附过程中，它可以使tamarense物种稳定共存。在任何一种情况下，杂交不育都可能对范围扩展造成重大障碍。巢式PCR是研究种间杂交及其对这些重要生物的全球生物地理学影响的一种有价值的工具。
We report the zygotic encystment of geographically dispersed isolates in the dinoflagellate species complex Alexandrium tamarense, in particular, successful mating of toxic Group I and nontoxic Group III isolates. However, hypnozygotes produced in Group I/III co-cultures complete no more than three divisions after germinating. Previous reports have suggested a mate recognition mechanism whereby hypnozygotes produced in co-cultures could arise from either homotypic (inbred) or heterotypic (outbred) gamete pairs. To determine the extent to which each occurs, a nested PCR assay was developed to determine parentage of individual hypnozygotes. The vast majority of hypnozygotes from pairwise Group I/III co-cultures were outbred, so that inviability was a result of hybridization, not inbreeding. These findings support the assertion that complete speciation underlies the phylogenetic structure of the Alexandrium tamarense species complex. Additionally, the ribosomal DNA (rDNA) copy numbers of both hybrid and single ribotype hypnozygotes were reduced substantially from those of haploid motile cells. The destruction of rDNA loci may be crucial for the successful mating of genetically distant conjugants and appears integral to the process of encystment. The inviability of Group I/III hybrids is important for public health because the presence of hybrid cysts may indicate ongoing displacement of a nontoxic population by a toxic one (or vice versa). Hybrid inviability also suggests a bloom control strategy whereby persistent, toxic Group I blooms could be mitigated by introduction of nontoxic Group III cells. The potential for hybridization in nature was investigated by applying the nested PCR assay to hypnozygotes from Belfast Lough, Northern Ireland, a region where Group I and III populations co-occur. Two hybrid cysts were identified in 14 successful assays, demonstrating that Group I and III populations do interbreed in that region. However, an analysis of mating data collected over an 18-year period indicated a leaky pre-mating barrier between ribosomal species (including Groups I and III). Whether the observed selectivity inhibits hybridization in nature is dependent on its mechanism. If the point of selectivity is the induction of gametogenesis, dissimilar ribotypes could interbreed freely, promoting displacement in cases where hybridization is lethal. If instead, selectivity occurs during the adhesion of gamete pairs, it could enable stable coexistence of A. tamarense species. In either case, hybrid inviability may impose a significant obstacle to range expansion. The nested PCR assay developed here is a valuable tool for investigation of interspecies hybridization and its consequences for the global biogeography of these important organisms.
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影响因子：
2.1
作者：
Lilly, EL;Kulis, DM;Anderson, DM
通讯作者：
Anderson, DM
影响因子：
--
作者：
HECKMANN, K;KUHLMANN, HW
通讯作者：
KUHLMANN, HW
影响因子：
64.8
作者：
BINDER, BJ;ANDERSON, DM
通讯作者：
ANDERSON, DM
影响因子：
1.6
作者：
HALLEGRAEFF, GM
通讯作者：
HALLEGRAEFF, GM
影响因子：
2.8
作者：
GUILLARD, RR;RYTHER, JH
通讯作者：
RYTHER, JH