For an introduced species to expand its range, individuals must be able to adapt to novel stressors (biotic and abiotic) that they may encounter. Florida has a distinct temperature gradient and rapid climate zone transitions from warmer subtropical regions to cooler temperate regions. Mean minimum temperatures are thought to prohibit northward movement of introduced fish species in south Florida. As the introduced Belonesox belizanus (pike killifish) expands its introduced range northward, it may be gaining cold tolerance. This study sought to compare thermal tolerances and cessation of feeding between adult B. belizanus from southern (initial, introduced population) and northern (spreading, fringe edge population) populations from its introduced range. To compare thermal tolerances between locations, southern individuals and northern individuals were acclimated to three temperatures (20, 25, and 30 °C) and their upper and lower lethal temperatures and cessation of feeding temperatures were measured. Two-way ANOVAs revealed that lower lethal temperatures and cessation of feeding temperatures were significantly different between northern and southern populations, with northern individuals having a lower lethal temperature approximately 0.5 °C lower and a cessation of feeding temperature approximately 2 °C lower compared with southern individuals. Directional selection may be influencing this non-native species’ thermal tolerance and feeding ability benefitting their continued effort to disperse from subtropical to temperate environments within Florida. This study indicates that B. belizanus may be gaining cold tolerance as it continues to spread northward in its introduced range.

为了使引入的物种扩大其范围，个体必须能够适应他们可能遇到的新压力源（生物和非生物）。佛罗里达州有明显的温度梯度，气候带从温暖的亚热带地区快速过渡到凉爽的温带地区。平均最低温度被认为会阻止佛罗里达州南部引入的鱼类向北移动。随着引入的Belonesox belizanus（梭子鱼）向北扩展其引入范围，它可能会获得耐寒性。本研究旨在比较成年B.belizanus之间的耐热性和停止进食来自其引入范围的南部（初始，引入的种群）和北部（扩散，边缘种群）的种群。为了比较不同地点之间的耐热性，南方个体和北方个体适应了三种温度（20、25 和 30°C），并测量了它们的致死温度上限和下限以及停止摄食的温度。双向方差分析显示，北部和南部种群之间较低的致死温度和停止摄食温度存在显着差异，与南方相比，北方个体的致死温度低约 0.5°C，停止摄食温度约低 2°C个人。定向选择可能会影响这种非本地物种的耐热性和摄食能力，有利于它们继续努力从佛罗里达州的亚热带到温带环境分散。本研究表明B. belizanus可能正在获得耐寒性，因为它继续在其引入范围内向北传播。