Agradecimentos: This work was financed by an ERC (European Research Council) consolidator grant COMPCON, GA 725419 attributed to SM and by FCT (Fundação para Ciência e Tecnologia) with the Junior researcher contract (CEECIND/02616/2018) attributed to IF. RC-P is supported by grant #2020/11953-2 São Paulo Research Foundation (FAPESP) and grant R-2011-37572 Instituto Serrapilheira. OG acknowledges financial support provided by the Spanish Ministry of Economy and Competitiveness (MINECO) and by the European Social Fund through the Ramón y Cajal Program (RYC-2017-23666). AM was funded by National Science Centre, Poland (grant no. 2018/28/T/NZ8/00060) and Excellence Initiative – Research University programme (support for the internationalisation of the Adam Mickiewicz University PhD students, no. 003/13/UAM/0018). The authors acknowledge stimulating discussion with all members of the Mite Squad, in particular Flore Zélé and Diogo Godinho, which have significantly improved the experimental design and interpretation of the results, and Marta Artal for invaluable infrastructure at meetings in Sevilla Ver menos

Abstract: Historical contingency, such as the order of species arrival, can modify competitive outcomes via niche modification or pre-emption. However, how these mechanisms ultimately modify stabilising niche and average fitness differences remains largely unknown. By experimentally assembling two congeneric spider mite species feeding on tomato plants during two generations, we show that order of arrival affects species' competitive ability and changes the outcome of competition. Contrary to expectations, order of arrival did not cause positive frequency dependent priority effects. Instead, coexistence was predicted when the inferior competitor (Tetranychus urticae) arrived first. In that case, T. urticae colonised the preferred feeding stratum (leaves) of T. evansi leading to spatial niche pre-emption, which equalised fitness and reduced niche differences, driving community assembly to a close-to-neutrality scenario. Our study demonstrates how the order of species arrival and the spatial context of competitive interactions may jointly determine whether species can coexist Ver menos