Hanson D, Barrett R D H, Hendry A P
Redpath Museum and Department of Biology, McGill University, Montreal, QC, Canada.
J Evol Biol. 2016 Jan;29(1):47-57. doi: 10.1111/jeb.12761. Epub 2015 Oct 14.
The evolution of reproductive isolation (RI) is a critical step shaping progress towards speciation. In the context of ecological speciation, a critical question is the extent to which specific reproductive barriers important to RI evolve rapidly and predictably in response to environmental differences. Only reproductive barriers with these properties (importance, rapidity, predictability) will drive the diversification of species that are cohesively structured by environment type. One candidate barrier that might exhibit such properties is allochrony, whereby populations breed at different times. We studied six independent lake-stream population pairs of threespine stickleback (Gasterosteus aculeatus Linnaeus, 1758) that are known from genetic studies to show RI. However, the specific reproductive barriers driving this RI have proven elusive, leading to a 'conundrum of missing reproductive isolation'. We here show that breeding times differ among some of the populations, but not in a consistent manner between lakes and streams. Moreover, the timing differences between lake and stream populations within each pair could account for only a small proportion of total RI measured with neutral genetic markers. Allochrony cannot solve the conundrum of missing reproductive isolation in lake-stream stickleback.
生殖隔离（RI）的演化是物种形成进程中的关键一步。在生态物种形成的背景下，一个关键问题是，对于RI而言重要的特定生殖屏障在多大程度上会随着环境差异而快速且可预测地演化。只有具备这些特性（重要性、快速性、可预测性）的生殖屏障，才会推动由环境类型紧密构建的物种多样化。一个可能展现出此类特性的候选屏障是异时性，即种群在不同时间进行繁殖。我们研究了六对三刺鱼（Gasterosteus aculeatus Linnaeus, 1758）的独立湖 - 河种群，从遗传学研究中已知它们表现出RI。然而，导致这种RI的具体生殖屏障一直难以捉摸，从而产生了一个“缺失生殖隔离之谜”。我们在此表明，部分种群之间的繁殖时间存在差异，但湖泊和溪流之间的差异并不一致。此外，每对中湖栖种群和河栖种群之间的时间差异，仅占用中性遗传标记测得的总RI的一小部分。异时性无法解决湖 - 河三刺鱼中缺失生殖隔离的谜题。
