Garmendia Alfonso, Merle Hugo, Ruiz Pablo, Ferriol Maria
Instituto Agroforestal Mediterráneo, Universitat Politècnica de València, Valencia, Spain.
Departamento de Ecosistemas Agroforestales, Universitat Politècnica de València, Valencia, Spain.
PeerJ. 2018 Jul 3;6:e5209. doi: 10.7717/peerj.5209. eCollection 2018.
Although polyploidy is considered a ubiquitous process in plants, the establishment of new polyploid species may be hindered by ecological competition with parental diploid taxa. In such cases, the adaptive processes that result in the ecological divergence of diploids and polyploids can lead to their co-existence. In contrast, non-adaptive processes can lead to the co-existence of diploids and polyploids or to differentiated distributions, particularly when the minority cytotype disadvantage effect comes into play. Although large-scale studies of cytotype distributions have been widely conducted, the segregation of sympatric cytotypes on fine scales has been poorly studied. We analysed the spatial distribution and ecological requirements of the tetraploid and the diploid in east Spain on a large scale, and also microspatially in contact zones where both species hybridise and give rise to sterile triploid hybrids. On the fine scale, the position of each individual was recorded along with soil parameters, accompanying species cover and plant richness. On the east Spanish coast, a slight latitudinal gradient was found. Tetraploid individuals were located northerly and diploid individuals southerly. Tetraploids were found only in the habitats with strong anthropogenic disturbance. In disturbed locations with well-developed semi-fixed or fixed dunes, diploids and tetraploids could co-exist and hybridise. However, on a fine scale, although taxa were spatially segregated in contact zones, they were not ecologically differentiated. This finding suggests the existence of non-adaptive processes that have led to their co-existence. Triploid hybrids were closer to diploid allogamous mothers () than to tetraploid autogamous fathers (). This may result in a better ability to compete for space in the tetraploid minor cytotype, which might facilitate its long-term persistence.
尽管多倍体在植物中被认为是一个普遍存在的过程，但新多倍体物种的形成可能会受到与亲本二倍体类群生态竞争的阻碍。在这种情况下，导致二倍体和多倍体生态分化的适应性过程可使其共存。相反，非适应性过程可导致二倍体和多倍体共存或分布分化，尤其是当少数细胞型劣势效应起作用时。尽管已广泛开展了细胞型分布的大规模研究，但对同域细胞型在精细尺度上的分离情况研究较少。我们在西班牙东部对四倍体和二倍体进行了大规模的空间分布和生态需求分析，同时在两种物种杂交并产生不育三倍体杂种的接触区进行了微观空间分析。在精细尺度上，记录了每个个体的位置以及土壤参数、伴生物种覆盖度和植物丰富度。在西班牙东部海岸，发现了轻微的纬度梯度。四倍体个体位于北部，二倍体个体位于南部。四倍体仅在受到强烈人为干扰的生境中出现。在半固定或固定沙丘发育良好的受干扰地点，二倍体和四倍体可以共存并杂交。然而，在精细尺度上，尽管类群在接触区在空间上是分离的，但它们在生态上并未分化。这一发现表明存在导致它们共存的非适应性过程。三倍体杂种更接近二倍体异花授粉母本（），而不是四倍体自花授粉父本（）。这可能导致四倍体少数细胞型在争夺空间方面具有更好的能力，这可能有助于其长期存续。
