Highlights d Growth at 25 C increases sexual attractiveness of C. elegans hermaphrodites d Increased attractiveness transmits transgenerationally via HRDE-1 and small RNAs d Attractiveness is associated with sperm defects and small RNAs targeting sperm genes d Stress-induced transient epigenetic inheritance enhances mating and can affect evolution

Paternal care, particularly in cases of uncertain paternity, carries significant costs. Extensive research, both theoretical and experimental, has explored the conditions in which paternal care behaviour would be favoured. Common explanations include an adjustment of care with uncertainty in paternity and limited accuracy in parentage assessment. Here, we propose a new explanation that microbes may play a role in the evolution of paternal care among their hosts. Using computational models, we demonstrate that microbes associated with increased paternal care could be favoured by natural selection. We find that microbe-induced paternal care could evolve under wider conditions than suggested by genetic models. Moreover, we show that microbe-induced paternal care is more likely to evolve when considering paternal care interactions that increase microbial transmission, such as feeding and grooming. Our results imply that factors affecting the composition of host microbiome may also alter paternal behaviour. This article is part of the theme issue ‘The role of the microbiome in host evolution’.

Social and behavioral non-pharmaceutical interventions (NPIs), such as mask-wearing, social distancing, and travel restrictions, as well as diagnostic tests, have been broadly implemented in response to the COVID-19 pandemic. Epidemiological models and data analysis affirm that wide adoption of NPIs helps to control the pandemic. However, SARS-CoV-2 has extensively demonstrated its ability to evolve. Therefore, it is crucial to examine how NPIs may affect the evolution of the virus. Such evolution could have important effects on the spread and impact of the pandemic. We used evo-epidemiological models to examine the effect of non-pharmaceutical interventions and testing on two evolutionary trajectories for SARS-CoV-2: attenuation and test evasion. Our results show that when stronger measures are taken, selection may act to reduce virulence. Additionally, the timely application of NPIs could significantly affect the competition between viral strains, favoring reduced virulence. Furthermore, a higher testing rate can select for a test-evasive viral strain, even if that strain is less infectious than the detectable competing strain. Importantly, if a less detectable strain evolves, epidemiological metrics such as confirmed daily cases may distort our assessment of the pandemic. Our results highlight the important implications NPIs can have on the evolution of SARS-CoV-2.

10Paternal care is an evolutionary mystery. Despite extensive research, both theoretical and 11 experimental, the reasons for its ubiquity remain unclear. Common explanations include kin 12 selection and limited accuracy in parentage assessment. However, these explanations do not 13 cover the breadth of circumstances in which paternal care has been observed, particularly in 14 cases of uncertain paternity. Here we propose that microbes may play a key role in the 15 evolution of paternal care among their hosts. Using computational models, we demonstrate 16 that microbes associated with increased paternal care could be favoured by natural selection. 17 We find that microbe-induced paternal care could evolve under wider conditions than 18 suggested by genetic models. Moreover, we show that microbe-induced paternal care is more 19 likely to evolve when considering paternal care interactions that increase microbial 20 transmission, such as feeding and grooming. Our results imply that factors affecting the 21 composition of host microbiome may also alter paternal behaviour. 22 Keywords 23 Microbiome, paternal care, mathematical model, extra-pair mating, sexual conflict, 24 nongenetic inheritance 25 26When would a father benefit more from caring for its offspring, rather than looking for 27 additional mating opportunities? This question has been broadly addressed both theoretically 28 and experimentally. Paternal care was frequently observed among avian species 1 (~85%), and 29 was also found in mammalian species 2 (~5%), amphibians 3 , and many species of fish 4 . 30Paternal care is most commonly observed alongside maternal care, while exclusive paternal 31 care is rare 4,5 . A male may demonstrate care for its offspring with several types of 32 interactions 4,5 , such as feeding, grooming, or guarding against predators. It can also provide 33 spousal care for the female while she cares for the young 6,7 . 34A commonly proposed explanation for the prevalence of paternal care is kin selection 8,9 . This 35 explanation suggests that paternal care would be favoured whenever the paternal contribution 36 to offspring survival increases paternal fitness more than pursuing additional mating 37 opportunities 10,11 . In some settings, such as caring for unrelated young, this explanation is 38 insufficient, and alternative explanations are suggested 12,13 . Interestingly, studies relating 39 paternal effort to certainty of paternity obtained mixed results 14-20 , and paternal care has been 40 observed even in cases of very high probability of extra-pair paternity (e.g. in avian species 21 41where extra-pair parenthood can range up to 95% in fairywrens 22 ). 42Here we consider the potential role of the microbes in host paternal care. The microbiome is a 43 significant agent affecting host health and behaviour [23][24][25][26][27] , through pathways such as the 'gut-44 brain axis' 28 . Numerous studies have demonstrated a possible association between microbes 45 and social behaviour [29][30][31][32][33][34] , and certain species o...

Social and behavioral non-pharmaceutical interventions (NPIs), such as mask-wearing, social distancing, and travel restrictions, as well as diagnostic tests, have been broadly implemented in response to the COVID-19 pandemic. Epidemiological models and data analysis affirm that wide adoption of NPIs helps to control the pandemic. However, SARS-CoV-2 has extensively demonstrated its ability to evolve. Therefore, it is crucial to examine how NPIs may affect the evolution of the virus. Such evolution could have important effects on the spread and impact of the pandemic. We used evo-epidemiological models to examine the effect of non-pharmaceutical interventions and testing on two evolutionary trajectories for SARS-CoV-2: attenuation and test evasion. Our results show that when stronger measures are taken, selection may act to reduce disease severity. Additionally, the timely application of NPIs could significantly affect the competition between viral strains, favoring the milder strain. Furthermore, a higher testing rate can select for a test-evasive viral strain, even if that strain is less infectious than the detectable competing strain. Importantly, if a less detectable strain evolves, epidemiological metrics such as confirmed daily cases may distort our assessment of the pandemic. Our results highlight the important implications NPIs can have on the evolution of SARS-CoV-2. LAY SUMMARY We used evo-epidemiological models to examine the effect of non-pharmaceutical interventions and testing on two evolutionary trajectories for SARS-CoV-2: attenuation and test evasion. Our results show that when stronger measures are taken, selection may act to reduce disease severity.