1. Organisms have evolved diverse strategies to manage parasite infections. Broadly, hosts may avoid infection by altering behaviour, resist infection by targeting parasites, or tolerate infection by repairing associated damage. Effectiveness of a strategy depends on interactions between, e.g., resource availability, parasite traits (virulence, life-history) and the host itself (nutritional status, immunopathology). 2. To understand how these factors shape host parasite-mitigation strategies, we developed a mathematical model of within-host, parasite-immune dynamics in the context of helminth infections. The model incorporated host nutrition and resource allocation to different mechanisms of immune response: larval parasite prevention; adult parasite clearance; damage repair (tolerance). We also considered a non-immune strategy: avoidance via anorexia, reducing intake of infective stages. Resources not allocated to immune processes promoted host condition, whereas harm due to parasites and immunopathology diminished it. Maximising condition (a proxy for fitness), we determined optimal host investment for each parasite-mitigation strategy, singly and combined, across different environmental resource levels and parasite trait values. 3. Which strategy was optimal varied with scenario. Tolerance generally performed well, especially with high resources. Success of the different resistance strategies (larval prevention or adult clearance) tracked relative virulence of larval and adult parasites: slowly maturing, highly damaging larvae favoured prevention; rapidly maturing, less harmful larvae favoured clearance. Anorexia was viable only in the short-term, due to reduced host nutrition. Combined strategies always outperformed any lone strategy: these were dominated by tolerance, with some investment in resistance. 4. Choice of parasite mitigation strategy has profound consequences for hosts, impacting their condition, survival and reproductive success. We show the efficacy of different strategies is highly dependent on timescale, parasite traits and resource availability. Models that integrate such factors can inform the collection and interpretation of empirical data, to understand how those drivers interact to shape host immune responses in natural systems.

Moorlands dominated by Calluna vulgaris (hereafter Calluna) are globally rare and under increasing threat of wildfires due to climate change. The soil seed bank is important for community resilience, but research on its contribution to regenerating vegetation after moorland fires has to date focused on prescribed fire or on the short-term (≤ 2 year) impacts of wildfire. To address the role of the seed bank in long-term vegetation regeneration, we studied a chronosequence of six wildfire sites within a Scottish moorland catchment, ranging from 2 to 64 years since burning. We recorded vegetation composition and sampled the seed bank. Calluna and Erica spp. comprised 66 % and 27 % of germinated seeds, respectively, and the majority of vegetation species were not represented in the seed bank. Canonical Correspondence Analysis (CCA) revealed that time since fire was a strong predictor of vegetation species composition, but it had no effect on seed bank composition, suggesting that the same species dominate the seed bank regardless of burning. Whilst total seed density was marginally reduced after wildfire and slightly increased with time, the non-Calluna seed bank was more notably affected. The proportion of non-Calluna species decreased with time in both vegetation and seed bank as Calluna cover was re-established and the seed bank of other species became gradually depleted. Whilst relative non-Calluna cover in the vegetation was at a maximum at the start of the chronosequence and then declined, the proportion of non-Calluna in the seed bank followed a unimodal pattern after fire and reached a peak after around 35 years. Our results contribute to the knowledge of how moorland ecosystems regenerate after severe disturbances, which are likely to become more common as the climate changes.