ORIGINAL RESEARCH article
Front. Ecol. Evol.
Sec. Behavioral and Evolutionary Ecology
Continental divergence in male reproductive plasticity to thermal and resource stress in a widespread dung fly
Provisionally accepted
- National University of Singapore, Singapore, Singapore
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Phenotypic plasticity in critical life-history traits may buffer populations against environmental changes, but its extent and direction can vary across geographic lineages. Here, we investigate how two major developmental stressors: rising temperatures and food limitation, affect life-history traits (juvenile survival, development time, adult body size, and male reproductive investment (testes size and sperm length)) in Sepsis punctum (Fabricius, 1794), a widespread dung fly with differing mating strategies and contrasting sexual size dimorphism (SSD) between North America (females larger) and Europe (males larger). Elevated temperatures significantly reduced larval survival and accelerated development, producing smaller adults particularly in European populations, while food limitation had little effect on survival but reduced adult size and differentially impacted SSD trends between continents: North American populations maintain female-biased SSD while male-biased SSD in European populations do not persist under resource stress. Male reproductive investment showed partial resilience: while absolute trait sizes declined under both stressors, size-independent investment was largely stable though we observe continental divergence in reproductive scaling under stress. Testes size, but not sperm length, declined with increasing temperatures, suggesting potential canalization of sperm quality and strategic resource allocation, trading off quantity under stress. We reveal continental divergence in phenotypic plasticity, highlighting the importance of geographic lineage and stressor type in shaping life-history trajectories. These findings Formatted: Font: Not Italic emphasize that climate-driven stressors like temperature may have stronger evolutionary consequences than resource limitation, with implications for population resilience under global change.
Keywords: Condition dependence, Environmental stress resilience, Geographic divergence, Postcopulatory traits, Reproductive plasticity, Diptera
Received: 23 Sep 2025; Accepted: 20 Nov 2025.
Copyright: © 2025 Lee, Tan, Wang, Tan and Puniamoorthy. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Nalini Puniamoorthy, nalini@nus.edu.sg
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