Department of Biological Sciences, University of Alabama, 300 Hackberry Lane, Box 870344, Tuscaloosa, AL 35487, USA
Department of Biological Sciences, University of Alabama, 300 Hackberry Lane, Box 870344, Tuscaloosa, AL 35487, USA.
J Exp Biol. 2020 Mar 11;223(Pt 5):jeb219196. doi: 10.1242/jeb.219196.
In heterogeneous environments, mobile species should occupy habitats in which their fitness is maximized. Mangrove rivulus fish inhabit mangrove ecosystems where salinities range from 0 to 65 ppt, but are most often collected from areas with salinities of ∼25 ppt. We examined the salinity preference of mangrove rivulus in a lateral salinity gradient, in the absence of predators and competitors. Fish could swim freely for 8 h throughout the gradient with chambers containing salinities ranging from 5 to 45 ppt (or 25 ppt throughout in the control). We defined preference as the salinity in which the fish spent most of their time, and also measured preference strength, latency to begin exploring the arena, and number of transitions between chambers. To determine whether these traits were repeatable, each fish experienced three trials. Mangrove rivulus spent a greater proportion of time in salinities lower (5-15 ppt) than they occupy in the wild. Significant among-individual variation in the (multivariate) behavioral phenotype emerged when animals experienced the gradient, indicating strong potential for selection to drive behavioral evolution in areas with diverse salinity microhabitats. We also showed that mangrove rivulus had a significantly greater probability of laying eggs in low salinities compared with control or high salinities. Eggs laid in lower salinities also had higher hatching success compared with those laid in higher salinities. Thus, although mangrove rivulus can tolerate a wide range of salinities, they prefer low salinities. These results raise questions about factors that prevent mangrove rivulus from occupying lower salinities in the wild, whether higher salinities impose energetic costs, and whether fitness changes as a function of salinity.
在异质环境中，移动物种应该占据其适应性最大化的栖息地。红树林鲷鱼栖息在盐度范围为 0 至 65 ppt 的红树林生态系统中，但通常最常从盐度约为 25 ppt 的区域采集。我们在没有捕食者和竞争者的情况下，在侧向盐度梯度中研究了红树林鲷鱼的盐度偏好。鱼可以在整个梯度中自由游动 8 小时，其中包含盐度为 5 至 45 ppt 的腔室（或在对照中始终为 25 ppt）。我们将偏好定义为鱼花费大部分时间的盐度，还测量了偏好强度、开始探索竞技场的潜伏期以及在腔室之间的转换次数。为了确定这些特征是否可重复，每条鱼经历了三次试验。与它们在野外的栖息地相比，红树林鲷鱼在较低的盐度（5-15 ppt）中花费了更多的时间。当动物经历梯度时，出现了个体间（多变量）行为表型的显著个体间差异，这表明在具有不同盐度微生境的区域中，选择具有强烈潜力来驱动行为进化。我们还表明，与对照或高盐度相比，红树林鲷鱼在低盐度下产卵的可能性显著更高。与在较高盐度下产卵相比，在较低盐度下产卵的卵孵化成功率也更高。因此，尽管红树林鲷鱼可以耐受广泛的盐度，但它们更喜欢低盐度。这些结果提出了一些问题，即是什么因素阻止了红树林鲷鱼在野外占据较低的盐度，较高的盐度是否会带来能量成本，以及盐度是否会影响适应性。
