Höltken Aki M, Gregorius Hans-Rolf
Institut für Forstgenetik und Forstpflanzenzüchtung, Büsgenweg 2, 37077 Göttingen, Germany.
BMC Ecol. 2006 Oct 4;6:13. doi: 10.1186/1472-6785-6-13.
P. avium, a pioneer tree species that colonizes early forest successional stages, is assumed to require an effective strategy allowing stably repeatable rounds of local establishment, dispersal and local extinction. Consequently, the early replacement of cherry by climax tree species makes the establishment of several local generations very unlikely, especially in central European continuous cover forests. This has to be seen in connection with the mixed reproduction system involving asexual reproduction as a complementary adaptational strategy. Tests of the local establishment of wild cherry must therefore consider the possibility of first generation establishment via seedling recruitment potentially followed by an asexual generation (root suckering). Successful establishment can therefore be determined only among adult individuals with the option of detecting vegetative reproduction at these stages. To test the implied suggestion about local establishment strategies of wild cherry, nuclear microsatellites were used to analyse patterns of asexual propagation among adult stages that have been subjected to one of two major types of forest management. These management types, the historical "coppice with standards system" (CWS) and the "high forest system" (HFS), can be reasonably assumed to have affected the reproduction system of P. avium.
Clear differences were found in the reproduction pattern between two stands representing the two forest management types: 1) Clonal propagation is observed in both management systems, but with a distinctly higher frequency in the CWS. Hence, sexual recruitment as a first local generation is followed by a second asexual generation in both, whereas in the CWS there is evidence for an additional clonal generation. 2) The estimation of amounts of clonal reproduction critically depends on the assumptions about multilocus gene associations. This is revealed by the application of newly developed methods of quantifying gene associations. 3) Haplotype diversities are higher in the CWS and found to be associated with a large degree of heterozygosity for the second largest clonal group. 4) Seed set was sparse over the last eight years of observation in the CWS stand.
This study provides useful guidelines for more comprehensive investigations, particularly on the interrelationships between degrees of cloning and capacity of sexual reproduction, amounts of multilocus gene associations, effects of heterozygosity on cloning success, and sustainability of different forest management types.
欧洲甜樱桃是一种先锋树种，在森林演替早期阶段定居，被认为需要一种有效的策略，以实现稳定可重复的局部定居、扩散和局部灭绝循环。因此，樱桃被顶极树种早期取代，使得建立多个本地世代的可能性极小，尤其是在中欧的连续覆盖森林中。这必须与涉及无性繁殖作为补充适应策略的混合繁殖系统联系起来看待。因此，对野生樱桃局部定居的测试必须考虑通过幼苗招募建立第一代，随后可能是无性世代（根蘖）的可能性。因此，只有在成年个体中，并能够在这些阶段检测到营养繁殖时，才能确定成功定居。为了测试关于野生樱桃局部定居策略的隐含建议，利用核微卫星分析了成年阶段无性繁殖的模式，这些成年个体来自两种主要森林管理类型之一。这两种管理类型，历史上的“有标准木的矮林作业系统”（CWS）和“乔林作业系统”（HFS），可以合理地假设已经影响了欧洲甜樱桃的繁殖系统。
在代表两种森林管理类型的两个林分中，繁殖模式存在明显差异：1）在两种管理系统中均观察到克隆繁殖，但在CWS中频率明显更高。因此，在两种系统中，作为第一代的有性繁殖之后都有第二代无性繁殖，而在CWS中有证据表明存在额外的克隆世代。2）克隆繁殖数量的估计严重依赖于关于多位点基因关联的假设。这通过应用新开发的量化基因关联的方法得以揭示。3）CWS中的单倍型多样性更高，并且发现与第二大克隆群体的高度杂合性相关。4）在CWS林分过去八年的观察中，结实率很低。
本研究为更全面的调查提供了有用的指导方针，特别是关于克隆程度与有性繁殖能力之间的相互关系、多位点基因关联的数量、杂合性对克隆成功的影响以及不同森林管理类型的可持续性。
