Department of Biology, University of Louisiana at Lafayette, Box 42451, Lafayette, LA 70504-2451, USA.
Ecotoxicology. 2011 May;20(3):535-42. doi: 10.1007/s10646-011-0624-2. Epub 2011 Mar 4.
Climate change is expected to result in an increased occurrence of heat stress. The long-term population-level impact of this stress would be lessened in populations able to genetically adapt to higher temperatures. Adaptation requires the presence of genetically-based variation. At-risk populations may undergo strong declines in population size that lower the amount of genetic variation. The objectives of this study were to quantify the heritability of heat tolerance in populations of the least killifish, Heterandria formosa, and to determine if heritabilities were reduced following a population bottleneck. Heritabilities of heat tolerance were determined for two lines of each of two source populations; two bottlenecked lines (established with one pair of fish) and two regular lines. Heat tolerance was quantified as temperature-at-death (TAD), when fish acclimated at 28 °C were subjected to an increase in water temperature of 2 °C/day. Mid-parent/mean offspring regressions and full-sib analyses were used to estimate the heritability of TAD. Heritability estimates from parent/offspring regressions ranged from 0.185 to 0.462, while those from sib analyses ranged from 0 to 0.324, with an overall estimate of 0.203 (0.230 for the regular lines, 0.168 for bottlenecked ones). Fish from the bottlenecked line from one source population (but not the other) had a lower heritability than did those from the regular line. These results show that the populations tested had some potential for adaptation to elevated water temperatures, and that this potential may be reduced following a population bottleneck. This should not be construed as evidence that natural populations will not suffer negative consequences from global warming; this study only showed that these specific populations have some potential to adapt under a very specific set of conditions.
预计气候变化将导致热应激的发生频率增加。在能够通过遗传适应更高温度的人群中，这种压力对人口的长期影响将会减轻。适应需要存在基于遗传的变异。处于危险中的人群可能会经历人口规模的急剧下降，从而降低遗传变异的数量。本研究的目的是量化最微小的食蚊鱼 Heterandria formosa 种群对耐热性的遗传力，并确定种群瓶颈后遗传力是否降低。对两个来源种群的每个种群的两个品系（建立时各有一对鱼）和两个常规品系进行了耐热性的遗传力测定。耐热性通过致死温度（TAD）来量化，当在 28°C 下驯化的鱼受到每天 2°C 的水温升高时。使用中亲/平均后代回归和全同胞分析来估计 TAD 的遗传力。亲本/后代回归的遗传力估计值范围从 0.185 到 0.462，而来自同胞分析的遗传力估计值范围从 0 到 0.324，总体估计值为 0.203（常规线为 0.230，瓶颈线为 0.168）。来自一个来源种群的瓶颈线鱼（而不是另一个）的遗传力低于常规线鱼。这些结果表明，所测试的种群具有适应升高水温的潜力，而这种潜力在种群瓶颈后可能会降低。这不应被解释为自然种群不会受到全球变暖负面影响的证据；本研究仅表明这些特定种群在非常具体的条件下具有适应的潜力。
