16Lysogeny is prevalent in the microbial-dense mammalian gut. This contrasts the classi-17 cal view of lysogeny as a refuge used by phages under poor host growth conditions. Here 18 we hypothesize that as carrying capacity increases, lysogens escape phage top-down control 19 through superinfection exclusion, overcoming the canonical trade-off between competition and 20 resistance. This hypothesis was tested by developing an ecological model that combined lytic 21 and lysogenic communities and a diversification model that estimated the accumulation of 22 prophages in bacterial genomes. The ecological model sampled phage-bacteria traits stochas-23 tically for communities ranging from 1 to 1000 phage-bacteria pairs, and it included a fraction 24 of escaping lysogens proportional to the increase in carrying capacity. The diversification 25 model introduced new prophages at each diversification step and estimated the distribution 26 of prophages per bacteria using combinatorics. The ecological model recovered the range of 27 abundances and sublinear relationship between phage and bacteria observed across eleven 28 ecosystems. The diversification model predicted an increase in the number of prophages per 29 genome as bacterial abundances increased, in agreement with the distribution of prophages 30 on 833 genomes from marine and human-associated bacteria. The study of lysogeny pre-31 sented here offers a framework to interpret viral and microbial abundances and reconciles the 32 Kill-the-Winner and Piggyback-the-Winner paradigms in viral ecology.33The human gut contains one of the highest concentrations of bacteria and phages-viruses that 35 infect bacteria-across ecosystems (Knowles et al. 2016; Wigington et al. 2016; Parikka et al. 2017). 36 This high concentration of microbes is sustained by the daily supply of nutrient-rich compounds 37 received from food intake and microbial metabolism (Blaut 2011; Cotillard et al. 2013; Mirzaei 38 and Maurice 2017). In other ecosystems-mostly aquatic environments-an increase of resources 39 has been linked to bacterial growth and phage lytic life cycle. This phage strategy produces new 40 phage particles upon infection and subsequently bursts the bacterial host (lysis). Combined with 41 the bacterial growth, the lytic life cycle ensures a rapid turnover of nutrients charateristic of the 42 kill-the-winner (KtW) dynamics (Maurice et al. 2011; Brum et al. 2016; Thingstad and Lignell 43 1997). In the nutrient-rich and microbial dense gut ecosystem, thus, one would expect a similar 44 phage lytic strategy. 45 Yet the lysogenic life cycle seems to be prevalent in the gut, where upon infection the phage 46 genome integrates in the bacterial host as a prophage, forming a phage-bacteria symbiont called 47 lysogen. Markers of lysogeny have been observed in viral genomic and metagenomic data from 48 healthy adults (Furuse et al. 1983; Letarov and Kulikov 2009; Reyes et al. 2010; Minot et al.