Changes in species dominance may drive regime shifts because dominant biotic feedbacks reflect functional traits of a community. Changes in species dominance has been documented by a 25-year fish community dataset encompassing six reaches of the Upper Mississippi and Illinois Rivers. Specifically, common carp (Cyprinus carpio) abundance has declined across all reaches, whereas silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis) have increased in abundance in the southern three reaches. To test whether signals in the data were consistent with regime transitions, changes in body-size patterns and trends in functional biomass and variance of functional biomass of the fish community were assessed. I further explored biomass thresholds relative to transitions. Shifts in body-size aggregations and trends in functional biomass support hypotheses that transitions from common carp dominance to a more functional diverse community represent alternate regimes. Results indicate such transitions occurred in the early 2000s for the two most northern reaches, and that the third most northern reach is nearing this transition. In the southern reaches, results indicate that transitions from common carp dominance to silver and bighead carp dominance also represent alternate regimes. Regime transitions support biomass thresholds between 8000 and 10,000 g per unit of day electrofishing effort of common carp and between 20 and 2000 g per unit effort in silver and bighead carp. Consistencies across reaches with similar dominance patterns provide support that reinforcing feedbacks, unique to the functional attributes of the dominant species, occur at similar biomass levels. Building knowledge of such feedback mechanisms is imperative to effectively manage for desired regimes.

物种优势的变化可能会导致政权转移，因为主要的生物反馈反映了社区的功能特征。25年鱼类群落数据集记录了物种优势的变化，该数据集涵盖密西西比河上游和伊利诺伊河的六个河段。具体来说，鲤鱼（Cyprinus carpio）的丰度在所有范围内都下降了，而silver鱼（Hypophthalmichthys molitrix）和big鱼（Hypophthalmichthys nobilis））南部三个河段的丰度有所增加。为了测试数据中的信号是否与政权转换一致，评估了鱼类群落的体型模式变化和功能性生物量的趋势以及功能性生物量的变化。我进一步探讨了相对于转变的生物量阈值。体型聚集的变化和功能性生物量的趋势支持以下假设，即从普通鲤鱼优势向功能更多样化的社区过渡代表了不同的制度。结果表明，这种过渡在2000年代初发生在最北端的两个河段，而最北端的第三个河段正在接近这一过渡。在南部河段，结果表明从普通鲤鱼优势向白银优势和transition鱼优势的过渡也代表了其他制度。过渡制度支持的生物量阈值是，鲤鱼每天进行电捕鱼的单位能力为8000至10,000 g，白silver和big鱼的单位生物活性阈值为20至2000 g。具有相似优势模式的跨区一致性为支持反馈提供了支持，这些反馈是优势物种的功能属性所独有的，发生在相似的生物量水平上。必须掌握此类反馈机制的知识，才能有效管理所需的制度。发生在相似的生物量水平。必须掌握此类反馈机制的知识，才能有效管理所需的制度。发生在相似的生物量水平。必须掌握此类反馈机制的知识，才能有效管理所需的制度。