Data from: Invasion of novel habitats uncouples haplo-diplontic life cycles.

Baker's Law predicts uniparental reproduction will facilitate colonization success in novel habitats. While evidence supports this prediction among colonizing plants and animals, few studies have investigated shifts in reproductive mode in haplo-diplontic species in which both prolonged haploid and diploid stages separate meiosis and fertilization in time and space. Due to this separation, asexual reproduction can yield the dominance of one of the ploidy stages in colonizing populations. We tested for shifts in ploidy and reproductive mode across native and introduced populations of the red seaweed Gracilaria vermiculophylla. Native populations in the northwest Pacific Ocean were nearly always attached by holdfasts to hard substrata and, as is characteristic of the genus, haploid-diploid ratios were slightly diploid-biased. In contrast, along North American and European coastlines, introduced populations nearly always floated atop soft-sediment mudflats and were overwhelmingly dominated by diploid thalli without holdfasts. Introduced populations exhibited population genetic signals consistent with extensive vegetative fragmentation, while native populations did not. Thus, the ecological shift from attached to unattached thalli, ostensibly necessitated by the invasion of soft-sediment habitats, correlated with shifts from sexual to asexual reproduction and slight to strong diploid bias. We extend Baker's Law by predicting other colonizing haplo-diplontic species will show similar increases in asexuality that correlate with the dominance of one ploidy stage. Labile mating systems likely facilitate colonization success and subsequent range expansion, but for haplo-diplontic species, the long-term eco-evolutionary impacts will depend on which ploidy stage is lost and the degree to which asexual reproduction is canalized.贝克法则（Baker's Law）预测，单亲繁殖将提升物种在新生境中的定殖成功率。尽管在殖民性动植物中已有证据支持这一预测，但鲜有研究针对单倍-二倍体型（haplo-diplontic）物种的繁殖模式转变展开调查——这类物种的长时程单倍体与二倍体阶段会使减数分裂与受精过程在时间与空间上相互分隔。由于这种时空分隔，无性繁殖可使定殖种群中某一倍数性阶段占据主导地位。我们针对红藻细基江蓠（Gracilaria vermiculophylla）的原生与引入种群，检验了其倍性与繁殖模式的变化。西北太平洋的原生种群几乎始终以固着器附着于硬质基质，且正如该属物种的典型特征，其单倍体-二倍体比例略微偏向二倍体。与之形成对比的是，在北美与欧洲海岸的引入种群中，个体几乎均漂浮于软沉积潮滩之上，且绝大多数为无固着器的二倍体叶状体。引入种群呈现出与广泛营养繁殖断裂相符的群体遗传信号，而原生种群则未出现这一特征。由此可见，从附着型叶状体向无附着型叶状体的生态转变（这一转变看似是入侵软沉积生境所必需），与有性繁殖向无性繁殖的转变、以及倍性偏向从微弱偏向二倍体转变为强烈偏向二倍体存在关联。我们拓展了贝克法则的适用范围，预测其他殖民性单倍-二倍体型物种也会出现类似的无性繁殖占比提升现象，且该变化与某一倍数性阶段的主导地位存在相关性。易变的交配系统或许有助于提升定殖成功率及后续的分布范围扩张，但对于单倍-二倍体型物种而言，其长期生态进化影响将取决于哪一倍数性阶段发生丢失，以及无性繁殖被定向化的程度。