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Dog-strangling vine (Vincetoxicum rossicum) is an exotic plant originating from Central and Eastern Europe that is becoming increasingly invasive in southern Ontario, Canada. Once established, it successfully displaces local native plant species but mechanisms behind this plant’s high competitive ability are not fully understood. It is unknown whether cooler temperatures will limit the range expansion of V. rossicum, which has demonstrated high tolerance for other environmental variables such as light and soil moisture. Furthermore, if V. rossicum can establish outside its current climatic limit it is unknown whether competition with native species can significantly contribute to reduce fitness and slow down invasion. We conducted an experiment to test the potential of V. rossicum to spread into northern areas of Ontario using a set of growth chambers to simulate southern and northern Ontario climatic temperature regimes. We also tested plant-plant competition by growing V. rossicum in pots with a highly abundant native species, Solidago canadensis, and comparing growth responses to plants grown alone. We found that the fitness of V. rossicum was not affected by the cooler climate despite a delay in reproductive phenology. Growing V. rossicum with S. canadensis caused a significant reduction in seedpod biomass of V. rossicum. However, we did not detect a temperature x competition interaction in spite of evidence for adaptation of S. canadensis to cooler temperature conditions. We conclude that the spread of V. rossicum north within the tested range is unlikely to be limited by climatic temperature but competition with an abundant native species may contribute to slow it down.
Based on morphological and molecular data we investigated the species boundaries in the genus Ochraethes Chevrolat, 1860. The species delimitation with cytochrome c oxidase subunit 1 (COI) data supports some synonymies and highlights the existence of a high phenotypic plasticity in some species. The following species are considered as new junior synonyms: O. virescens (Chevrolat, 1860) syn. nov. of O. brevicornis (Chevrolat, 1860), O. octomaculata Chemsak & Noguera 2001 syn. nov. of Ochraethes cinereolus (Bates, 1892) comb. nov., O. zebratus Bates, 1885 syn. nov. of O. obliquus (Chevrolat, 1860), Trichoxys giesberti Botero, Santos-Silva & Wappes, 2019 syn. nov. of O. sommeri (Chevrolat, 1835), O. clerinus (Bates, 1892) of O. viridiventris (Chevrolat, 1860), O. cristoforii (Chevrolat, 1860) syn. nov. and O. litura Bates, 1885 syn. nov. of O. z-littera (Chevrolat, 1860). Two new species are described from Mexico: Ochraethes confusus sp. nov., and Ochraethes nigroapicalis sp. nov.