Data from: Sensitivity to phosphorus limitation increases with ploidy level in a New Zealand snail

Evolutionary and ecological factors that explain natural variation in ploidy level remain poorly understood. One intriguing possibility is that nutrient costs associated with higher per-cell nucleic acid content could differentially influence the fitness of different ploidy levels. Here, we test this hypothesis by determining whether access to phosphorus (P), a main component of nucleic acids, differentially affects growth rate in asexual freshwater snails (Potamopyrgus antipodarum) that differ in ploidy. As expected if larger genomes generate higher dietary P requirements, tetraploid P. antipodarum experienced a more than two-fold greater reduction in growth rate in low- vs. high-P conditions relative to triploids. Mirroring these results, tetraploid P. antipodarum also had a significant reduction in body P content under low P relative to high P, while triploid body P content was unaffected. Taken together, these results set the stage for the possibility that P availability could influence the distribution and relative frequency of P. antipodarum of different ploidy levels. These findings could be applicable to many other animal taxa featuring ploidy-level variation, which includes most mixed sexual/asexual taxa.

解释倍性水平（ploidy level）自然变异的进化与生态因子，目前仍未得到充分阐释。一种颇具研究价值的假说认为，与更高每细胞核酸含量相关的营养成本，可能会对不同倍性水平的个体适合度（fitness）产生差异化影响。本研究通过探究磷（phosphorus，P，核酸的主要组成成分）的可获得性是否会对不同倍性的无性（asexual）淡水螺——异口拟沼螺（Potamopyrgus antipodarum）——的生长速率产生差异化影响，以此检验上述假说。若基因组更大会导致更高的膳食磷需求，则预期结果应是：相较于三倍体（triploid），四倍体（tetraploid）P. antipodarum在低磷与高磷条件下的生长速率降幅超过两倍。与上述结果一致，四倍体P. antipodarum在低磷条件下的体内磷含量相较于高磷条件下出现显著下降，而三倍体的体内磷含量则未受影响。综合来看，本研究结果为"磷的可获得性可能会影响不同倍性P. antipodarum的分布与相对频率"这一可能性奠定了研究基础。本研究发现或可推广至诸多存在倍性水平变异的动物类群（taxa），其中涵盖绝大多数兼具有性与无性繁殖的类群。