The principal eigenvalue for partially degenerate and periodic reaction-diffusion systems with time delay

In this paper, we first establish the theory of principal eigenvalues for a large class of partially degenerate, linear and periodic parabolic cooperative systems with time delay. Then we apply these theoretical results to study the global dynamics of a blacklegged tick Ixodes scapularis population model. To present a thresholdtype result in terms of basic reproduction ratio R0 for such a model, we also extend the earlier theory of R0 to abstract functional differential equations with time-delayed internal transition.& COPY; 2023 Elsevier Inc. All rights reserved.