Ancestral ecological regime shapes reaction to food limitation in the Least Killifish, Heterandria formosa,Ecology and Evolution

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Ancestral ecological regime shapes reaction to food limitation in the Least Killifish, Heterandria formosa
Ecology and Evolution ( IF 2.3 ) Pub Date : 2021-04-06 , DOI: 10.1002/ece3.7490
Anja Felmy ₁ , Jeff Leips ₂ , Joseph Travis ₃

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Populations with different densities often show genetically based differences in life histories. The divergent life histories could be driven by several agents of selection, one of which is variation in per-capita food levels. Its relationship with population density is complex, as it depends on overall food availability, individual metabolic demand, and food-independent factors potentially affecting density, such as predation intensity. Here, we present a case study of two populations of a small live-bearing freshwater fish, one characterized by high density, low predation risk, low overall food availability, and presumably low per-capita food levels, and the other by low density, high predation risk, high overall food availability, and presumably high per-capita food levels. Using a laboratory experiment, we examined whether fish from these populations respond differently to food limitation, and whether size at birth, a key trait with respect to density variation in this species, is associated with any such differential responses. While at the lower food level growth was slower, body size smaller, maturation delayed, and survival reduced in both populations, these fitness costs were smaller in fish from the high-density population. At low food, only 15% of high-density fish died, compared to 75% of low-density fish. This difference was much smaller at high food (0% vs. 15% mortality). The increased survival of high-density fish may, at least partly, be due to their larger size at birth. Moreover, being larger at birth enabled fish to mature relatively early even at the lower food level. We demonstrate that sensitivities to food limitation differ between study populations, consistent with selection for a greater ability to tolerate low per-capita food availability in the high-density population. While we cannot preclude other agents of selection from operating in these populations simultaneously, our results suggest that variation in per-capita food levels is one of those agents.

中文翻译：

祖先的生态状况塑造了最小鳉鱼（Heterandria formosa）对食物限制的反应

不同密度的人群在生活史中常常表现出基于遗传的差异。不同的生活史可能是由多种选择因素驱动的，其中之一是人均食物水平的差异。它与人口密度的关系很复杂，因为它取决于总体食物供应量、个体代谢需求以及可能影响密度的与食物无关的因素，例如捕食强度。在这里，我们提出了一个小型活生淡水鱼的两个种群的案例研究，一个种群的特点是密度高、捕食风险低、总体食物供应量低、人均食物水平可能较低，另一个种群的特点是密度低、捕食风险高，总体粮食供应量高，并且人均粮食水平可能很高。通过实验室实验，我们检查了这些种群的鱼类对食物限制的反应是否不同，以及出生时的体型（该物种密度变化的一个关键特征）是否与任何此类差异反应相关。虽然在较低的食物水平下，两个种群的生长速度较慢，体型较小，成熟延迟，存活率降低，但高密度种群的鱼类的这些健康成本较小。在低食物量下，高密度鱼只有 15% 死亡，而低密度鱼则有 75% 死亡。高食物时这种差异要小得多（死亡率为 0% 与 15%）。高密度鱼类存活率的提高可能至少部分归因于它们出生时体型较大。此外，出生时体型较大，即使在食物水平较低的情况下，鱼类也能相对较早成熟。我们证明，研究人群之间对食物限制的敏感性有所不同，这与在高密度人群中选择具有更强的耐受人均食物供应量的能力是一致的。虽然我们不能排除其他选择因素同时在这些人群中发挥作用，但我们的结果表明，人均食物水平的变化是其中之一。

更新日期：2021-04-06

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