Dynamic evolution of sex ratio in lampreys: Investigating population and ecosystem stability based on a game-theoretic framework

The environmental plasticity of sex evolution in lampreys is a pivotal regulatory factor for their population stability, yet existing research lacks cross-scale quantitative analysis.This study constructs a three-tier progressive framework consisting of microscopic individual growth, intra-population game dynamics, and interspecific ecological interactions.Based on a modified Lotka-Volterra population game model, we systematically investigate the dynamic evolution of sex ratios in lampreys and its ecological effects.First, quadratic polynomial fitting is employed to quantify growth trajectories and establish an endogenous sex transition function governed by growth rate. Second, the Lotka-Volterra model is refined by incorporating male-female competitive game dynamics to analyze the equilibrium of sex ratios under resource constraints. Finally, modules of sockeye salmon and parasites are integrated to construct a multi-trophic level model, using standardized regression coefficients (SRC) and payoff functions to analyze sensitive parameters and ecosystem stability. Experimental results indicate that under harsh environmental conditions, sex transition can increase the intrinsic growth rate of lampreys by 114%, effectively preventing population collapse. With moderate resource availability, the male-to-female ratio ranges from 0.6 to 0.7 (female dominance); under abundant resources, intra-population competition remains mild, the proportion of females increases, and the payoff is maximized; whereas under resource scarcity, male dominance becomes pronounced, leading to the poorest population performance and lowest payoff. The introduction of sockeye salmon enhances female transition rates by approximately 10% through nutritional supply, increasing the total lamprey population by 20% In contrast, the inclusion of parasites intensifies population competition among lampreys, increases the proportion of males, and reduces the total population by 15.2%. SRC analysis reveals that the resource environment carrying capacity (KR) is the core parameter affecting the sex ratio. A system stability index of 0.004314, a Shannon-Wiener diversity index of 1.523, and a resilience index of 0.966 jointly verify the synergy between population stability and ecosystem stability. Furthermore, simulation experiments indicate that moderate anthropogenic harvesting of lampreys in this area can maintain the balance between populations and the ecosystem, exerting a positive impact on the fishery industry.This model establishes a quantitative linkage between the micro-level sex-allocation strategies of a population with variable sex ratios and macro-level ecological stability, providing a theoretical foundation for sustainable ecological management practices.