Centro de Investigación en Ciencias Biológicas, Universidad Autónoma de Tlaxcala, Tlaxcala, Mexico.
Departamento de Biología Evolutiva, Instituto de Ecología, A.C. (INECOL), Veracruz, Mexico.
Plant Biol (Stuttg). 2021 Jul;23(4):603-611. doi: 10.1111/plb.13266. Epub 2021 May 7.
Host trees are immediate environments for multi-host mistletoes, so parasitizing different hosts implies exposure to varying environmental conditions between mistletoe generations. Therefore, to maximize reproductive fitness in heterogeneous environments (host species) mistletoes should adjust its reproductive responses in relation to circumstances. Here, we ask how reproductive traits of Psittacanthus calyculatus mistletoes vary on two host tree species (Crataegus mexicana, Prunus serotina) at three different localities. We followed individual mistletoes on each host species and at three localities through the flowering season to quantify traits related to reproductive effort and success, e.g. total number of buds, flowers and fruits produced. In buds about to open, we measured two anthers and quantified the number of pollen grains and their viability. Individual flowers were marked to obtain flower longevity data and were followed until fruit formation. At which time we measured and weighed the fruits and the seeds. Mistletoes from one locality produced more buds, flowers and fruits, and the flowers lasted longer, had larger anthers and produced more pollen as compared to the other two localities. However, mistletoes on Prunus serotina produced fewer floral buds, but their fruits were heaviest, longest and widest and ripened fastest across localities. The probability of fruit formation, percentage of fruits formed, and pollen viability were similar among the mistletoes, regardless of host species or locality. We propose that the observed differences in reproductive effort and success associated with host species or locality are plastic or adaptive in this mistletoe in response to varying conditions.
寄主树是多宿主槲寄生的直接环境，因此寄生不同的寄主意味着槲寄生在不同的世代中暴露于不同的环境条件下。因此，为了在异质环境（寄主物种）中最大限度地提高生殖适应性，槲寄生应该根据环境条件调整其生殖反应。在这里，我们询问在三个不同地点的两种寄主树上（山楂、欧洲甜樱桃），Psittacanthus calyculatus 槲寄生的繁殖特征如何变化。我们在每个寄主物种和三个地点的开花季节中跟踪个体槲寄生，以量化与生殖努力和成功相关的特征，例如产生的总芽、花和果实数量。在即将开放的芽中，我们测量了两个花药并量化了花粉粒的数量及其活力。对个体花朵进行标记以获得花朵寿命数据，并一直跟踪到果实形成。此时，我们测量并称重果实和种子。与其他两个地点相比，一个地点的槲寄生产生了更多的芽、花和果实，花朵持续时间更长，花药更大，产生的花粉更多。然而，Prunus serotina 上的槲寄生产生的花芽较少，但它们的果实最重、最长、最宽，在不同地点成熟最快。果实形成的概率、形成果实的百分比和花粉活力在槲寄生之间相似，无论寄主物种或地点如何。我们提出，与寄主物种或地点相关的生殖努力和成功的差异是这种槲寄生对不同条件的可塑性或适应性的表现。
