Institute for Ocean Conservation Science & School of Marine and Atmospheric Science, Stony Brook University, Stony Brook, NY 11794, USA.
J Hered. 2011 Nov-Dec;102(6):643-52. doi: 10.1093/jhered/esr098. Epub 2011 Sep 15.
Sawfish (family Pristidae) are among the most critically endangered marine fish in the world, yet very little is known about how genetic bottlenecks, genetic drift, and inbreeding depression may be affecting these elasmobranchs. In the US Atlantic, the smalltooth sawfish (Pristis pectinata) has declined to 1-5% of its abundance in the 1900s, and its core distribution has contracted to southwest Florida. We used 8 polymorphic microsatellite markers to show that this remnant population still exhibits high genetic diversity in terms of average allelic richness (18.23), average alleles per locus (18.75, standard deviation [SD] 6.6) and observed heterozygosity (0.43-0.98). Inbreeding is rare (mean individual internal relatedness = -0.02, SD 0.14; F(IS) = -0.011, 95% confidence interval [CI] = -0.039 to 0.011), even though the estimated effective population size (N(e)) is modest (250-350, 95% CI = 142-955). Simulations suggest that the remnant smalltooth sawfish population will probably retain >90% of its current genetic diversity over the next century even at the lower estimate of N(e). There is no evidence of a genetic bottleneck accompanying last century's demographic bottleneck, and we discuss hypotheses that could explain this. We also discuss features of elasmobranch life history and population biology that could make them less vulnerable than other large marine vertebrates to genetic change associated with reduced population size.
锯鳐（Pristidae 科）是世界上最濒危的海洋鱼类之一，但人们对遗传瓶颈、遗传漂变和近交衰退如何影响这些软骨鱼类知之甚少。在美国大西洋，小齿锯鳐（Pristis pectinata）的数量在 20 世纪下降到了原来的 1-5%，其核心分布范围已缩小到佛罗里达州西南部。我们使用 8 个多态性微卫星标记来表明，这个残余种群在平均等位基因丰富度（18.23）、每个位点的平均等位基因（18.75，标准差 6.6）和观察到的杂合度（0.43-0.98）方面仍然表现出很高的遗传多样性。近亲繁殖很少见（平均个体内部相关性=-0.02，标准差 0.14；F(IS)=-0.011，95%置信区间[CI]为-0.039 至 0.011），尽管估计的有效种群大小（N(e)）适中（250-350，95%置信区间[CI]为 142-955）。模拟表明，即使在 N(e)的较低估计值下，残余的小齿锯鳐种群在未来一个世纪可能会保留其当前遗传多样性的>90%。没有证据表明遗传瓶颈伴随着上世纪的种群瓶颈，我们讨论了可以解释这一现象的假设。我们还讨论了软骨鱼类生活史和种群生物学的特征，这些特征可能使它们比其他大型海洋脊椎动物更不容易受到与种群规模减少相关的遗传变化的影响。
