Boecklen William J
Department of Biology New Mexico State University Las Cruces NM USA.
Ecol Evol. 2017 Nov 1;7(24):10486-10491. doi: 10.1002/ece3.3507. eCollection 2017 Dec.
Syngameons are sets of species linked by interspecific hybridization. Common observations regarding the structure of syngameons are that hybridization propensity is not uniform across species and that patterns of hybridization are dominated by a few species. I use computer simulations to test these claims in naturally occurring syngameons selected from the literature and from personal observation. Natural syngameons, especially those involving plants, typically exhibit nonrandom structure: The first three order statistics for the number of hybrid partners and the variance in the number of hybrid partners are larger than chance alone would predict. The structure of two insect syngameons examined is not significantly different from random. To test a hypothesis that variation in hybridization propensity across species in natural syngameons is simply an artifact of hybridization opportunity, I examine the structure of four artificial syngameons (fertility relationships) produced by full diallel crosses. Three of four artificial syngameons exhibit nonrandom structure, as the observed variation in number of successful crosses is larger than chance alone would predict. In general, there are no significant results involving the order statistics. Finally, I discuss biogeographic, ecological, and phylogenetic hypotheses for variation in hybridization propensity across species in natural syngameons.
同配生殖系是通过种间杂交联系在一起的物种集合。关于同配生殖系结构的常见观察结果是，杂交倾向在物种间并不均匀，且杂交模式由少数物种主导。我使用计算机模拟来检验从文献和个人观察中选取的自然存在的同配生殖系中的这些说法。自然同配生殖系，尤其是那些涉及植物的同配生殖系，通常呈现非随机结构：杂交伙伴数量的前三个顺序统计量以及杂交伙伴数量的方差大于仅由随机因素所预测的结果。所研究的两个昆虫同配生殖系的结构与随机结构没有显著差异。为了检验一个假设，即自然同配生殖系中物种间杂交倾向的差异仅仅是杂交机会的一种假象，我研究了由完全双列杂交产生的四个人工同配生殖系（育性关系）的结构。四个人工同配生殖系中有三个呈现非随机结构，因为观察到的成功杂交数量的变化大于仅由随机因素所预测的结果。一般来说，涉及顺序统计量没有显著结果。最后，我讨论了关于自然同配生殖系中物种间杂交倾向差异的生物地理、生态和系统发育假设。
