Department of Geological and Environmental Sciences, Stanford University, 385 Serra Mall, Stanford, CA 94305, USA.
Am J Bot. 2013 Jun;100(6):1221-6. doi: 10.3732/ajb.1300018. Epub 2013 Jun 3.
Invasive plant species threaten native plants in multiple ways, one of which is genetic assimilation through hybridization. However, information regarding hybridization between related alien and native plant species is generally lacking. In Hawaii, the invasive Central American species Bidens pilosa and Bidens alba have colonized natural areas and often grow alongside the native Hawaiian Bidens species, a clade representing an adaptive radiation of 27 endemic taxa, many of which are threatened or endangered. •
To assess the risk of hybridization between introduced and native Hawaiian Bidens (which will readily hybridize with one another), we undertook crosses in cultivation between the invasive species and nine native Bidens taxa. •
The majority of the crosses formed no viable seed. Although seed did mature in several of the crosses, morphological screening of the resulting seedlings indicated that they were the result of self-pollination. •
This result suggests that B. alba and B. pilosa are incapable of hybridizing with these Hawaiian Bidens taxa. Further, we found that B. alba in Hawaii was self-compatible, despite self-incompatibility throughout its native range, and that the tetraploid species B. alba and the hexaploid species B. pilosa were cross-compatible, although pollen fertility was low.
入侵植物物种通过杂交等多种方式威胁本地植物，其中之一是遗传同化。然而，关于相关外来和本地植物物种之间杂交的信息通常是缺乏的。在夏威夷，入侵的中美洲物种三叶鬼针草和白花鬼针草已经在自然区域中定植，并且经常与本地夏威夷三叶鬼针草物种生长在一起，后者代表了 27 个特有分类群的适应性辐射，其中许多都受到威胁或濒危。
为了评估引入的和本地夏威夷三叶鬼针草（它们之间很容易杂交）之间杂交的风险，我们在栽培中进行了入侵物种与 9 个本地三叶鬼针草分类群之间的杂交。
大多数杂交没有形成有活力的种子。尽管在一些杂交中确实成熟了种子，但对产生的幼苗进行形态学筛选表明，它们是自花授粉的结果。
这一结果表明，白花鬼针草和三叶鬼针草不能与这些夏威夷三叶鬼针草分类群杂交。此外，我们发现夏威夷的白花鬼针草是自交亲和的，尽管在其原生范围内自交不亲和，并且四倍体物种白花鬼针草和六倍体物种三叶鬼针草是可杂交的，尽管花粉活力较低。
