Data from: Wide variation in ploidy level and genome size in a New Zealand freshwater snail with coexisting sexual and asexual lineages

Natural animal populations are rarely screened for ploidy-level variation at a scale that allows detection of potentially important aberrations of common ploidy patterns. This type of screening can be especially important for the many mixed sexual/asexual systems where sexuals are presumed to be dioecious diploids and asexuals are assumed to be triploid and all-female. For example, elevation of ploidy level above triploidy can be a source of genetic variation and raises the possibility of gene flow among ploidy levels and to asexual lineages. We used flow cytometry and mtDNA sequencing to characterize ploidy level and genome size in Potamopyrgus antipodarum, a New Zealand freshwater snail where obligate sexual (presumed diploid and dioecious) and obligate apomictic asexual (presumed triploid and nearly all female) individuals frequently coexist. We documented the widespread occurrence and multiple origins of polyploid males and individuals with >3x ploidy, and find that both are likely to be descended from asexual females. Our survey also revealed extensive variation in genome size. The discovery of widespread variation in ploidy level and genome size in such a well-studied system highlights the importance of broad, extensive, and ecologically representative sampling in uncovering ploidy level and genome size variation in natural populations.

自然动物种群中，鲜有以能够检出常见倍性模式潜在重要异常的尺度开展倍性水平变异筛查的研究。这类筛查对于众多性与无性共存的繁殖系统尤为关键——此类系统中，有性繁殖个体通常被认为是雌雄异体的二倍体，而无性繁殖个体则被假定为三倍体且全为雌性。例如，倍性水平升至三倍体以上可作为遗传变异的来源之一，同时也增加了不同倍性水平之间以及向无性繁殖谱系发生基因流的可能性。本研究采用流式细胞术（flow cytometry）与线粒体DNA测序（mtDNA sequencing），对新西兰淡水螺（Potamopyrgus antipodarum）的倍性水平与基因组大小进行了表征；该物种中专性有性繁殖个体（假定为二倍体、雌雄异体）与专性无融合生殖型无性个体（假定为三倍体且几乎全为雌性）常共存。本研究记录了多倍体雄性与倍性高于三倍体（>3x）个体的广泛分布及其多重起源，并发现这两类个体均可能起源于无性雌性。本次调查还揭示了基因组大小存在广泛变异。在这一已被充分研究的物种系统中发现倍性水平与基因组大小的广泛变异，凸显了采用大范围、多尺度且具备生态代表性的采样方案，对于揭示自然种群中倍性水平与基因组大小变异的重要性。