The long journey of Orthotrichum shevockii (Orthotrichaceae, Bryopsida): From California to Macaronesia

Biogeography, systematics and taxonomy are complementary scientific disciplines. To understand a species' origin, migration routes, distribution and evolutionary history, it is first necessary to establish its taxonomic boundaries. Here, we use an integrative approach that takes advantage of complementary disciplines to resolve an intriguing scientific question. Populations of an unknown moss found in the Canary Islands (Tenerife Island) resembled two different Californian endemic species: Orthotrichum shevockii and O. kellmanii. To determine whether this moss belongs to either of these species and, if so, to explain its presence on this distant oceanic island, we combined the evaluation of morphological qualitative characters, statistical morphometric analyses of quantitative traits, and molecular phylogenetic inferences. Our results suggest that the two Californian mosses are conspecific, and that the Canarian populations belong to this putative species, with only one taxon thus involved. Orthotrichum shevockii (the priority name) is therefore recognized as a morphologically variable species that exhibits a transcontinental disjunction between western North America and the Canary Islands. Within its distribution range, the area of occupancy is limited, a notable feature among bryophytes at the intraspecific level. To explain this disjunction, divergence time and ancestral area estimation analyses are carried out and further support the hypothesis of a long-distance dispersal event from California to Tenerife Island.This research was funded by the Spanish Ministry of Education and Science (CGL2007-61389/BOS) to F.L., the Spanish Ministry of Science and Innovation (CGL2011-28857/BOS) to V.M., the Spanish Ministry of Economy and Competitiveness (CGL2013-43246-P) to R.G., and the Spanish Ministry of Economy, Industry and Competitiveness (CGL2016-80772-P) to I.D. and the Spanish Ministry of Economy and Competitiveness (grants IJCI-2014-19691 and RYC‐2016‐20506) to J.P. J.P. also received the H2020 Marie Skłodowska-Curie Actions grant 747238. J.M.G-M and A.L-L. are grateful for funding from Parque Nacional del Teide. B.V. benefited from the support of the Ministry of Economy and Competitiveness through grant BES-2012-051976 of the Formación de Personal Investigador (FPI) programme.Peer Reviewe