doi:10.3389/fcimb.2017.00234engEstrada-Peña, A.de la Fuente, J.Cabezas-Cruz, A.Functional redundancy and ecological innovation shape the circulation of tick-transmitted pathogensART-2017-101725Ticks are vectors of pathogens affecting human and animal health worldwide. Nevertheless, the ecological and evolutionary interactions between ticks, hosts, and pathogens are largely unknown. Here, we integrated a framework to evaluate the associations of the tick Ixodes ricinus with its hosts and environmental niches that impact pathogen circulation. The analysis of tick-hosts association suggested that mammals and lizards were the ancestral hosts of this tick species, and that a leap to Aves occurred around 120 M years ago. The signature of the environmental variables over the host''s phylogeny revealed the existence of two clades of vertebrates diverging along a temperature and vegetation split. This is a robust proof that the tick probably experienced a colonization of new niches by adapting to a large set of new hosts, Aves. Interestingly, the colonization of Aves as hosts did not increase significantly the ecological niche of I. ricinus, but remarkably Aves are super-spreaders of pathogens. The disparate contribution of Aves to the tick-host-pathogen networks revealed that I. ricinus evolved to maximize habitat overlap with some hosts that are super-spreaders of pathogens. These results supported the hypothesis that large host networks are not a requirement of tick survival but pathogen circulation. The biological cost of tick adaptation to non-optimal environmental conditions might be balanced by molecular mechanisms triggered by the pathogens that we have only begun to understand.2017http://zaguan.unizar.es/record/6303910.3389/fcimb.2017.00234http://zaguan.unizar.es/record/63039oai:zaguan.unizar.es:63039info:eu-repo/grantAgreement/EC/FP7/278976/EU/ANTIcipating the Global Onset of Novel Epidemics/ANTIGONEinfo:eu-repo/grantAgreement/EUR/COST/TD1303Frontiers in cellular and infection microbiology 7, MAY (2017), 234 [11 pp]byhttp://creativecommons.org/licenses/by/3.0/es/info:eu-repo/semantics/openAccess