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Dalmatian and yellow toadflax, Linaria dalmatica and L. vulgaris, are exotic weeds in North America, and their classical biological control has been improved by the establishment of seed-feeding (Rhinusa antirrhini) and stem-mining (Mecinus janthinus and Mecinus janthiniformis) weevils. Here, we evaluated the complex of hymenopteran parasitoids attacking these weevils in Colorado. Ten species were identified of the genera Neocatolaccus, Eurytoma, Pteromalus, Brasema, Telenomus and Bracon. Neocatolaccus tylodermae was the most abundant parasitoid of M. janthinus, M. janthiniformis and R. antirrhini. This is the first report of N. tylodermae attacking the weevil genera Mecinus and Rhinusa feeding on the genus Linaria. [ABSTRACT FROM AUTHOR]

Abstract: What drives the evolution of increased growth and fecundity in plants introduced to a novel range is not well understood. We investigate between‐range differences in performance for Verbascum thapsus, a weedy invader known to grow larger in its introduced than native range. Specifically, we question whether adaptation to herbivory or climate best explains increased performance of introduced populations. We grew 14 native and 22 introduced populations of V. thapsus in two common garden locations: near Prague, Czech Republic (native range) and in Colorado, USA (introduced range). By removing herbivores from half of the plants within each garden we tested the prediction of the evolution of increased competitive ability (EICA) hypothesis: increased performance is driven by an evolutionary shift of resources away from defence against herbivory towards growth and reproduction. We then investigated whether genetically based clines in performance are expressed along climate gradients within both the native and introduced ranges. On average, seeds produce larger rosettes when collected from the introduced vs. native range. While this evolution of increased growth in introduced populations in part matches the prediction of EICA, climate, not herbivory, best explains this between‐range difference. Specifically, seeds collected from the native range produce smaller rosettes as the climate of origin becomes cooler and drier, while there is no cline in performance in rosettes grown from seed collected from the introduced range, which are large regardless of climate of origin. Thus, a climate‐based cline within the native range best explains lower average performance of native compared to introduced populations. Synthesis. The breakdown in a potentially adaptive cline emphasizes the need to more closely investigate the evolutionary processes that shape geographic structuring (or its absence) within the introduced range. In addition, EICA is not universally applicable to all invasion scenarios, and our findings underscore the importance of testing the underlying assumptions alongside the predictions of this hypothesis. [ABSTRACT FROM AUTHOR]

Brachypterolus pulicarius (L.) (Coleoptera: Kateridae) is an inadvertently introduced biological control agent that can reduce seed set in two North American invasive species, yellow ( Linaria vulgaris P. Mill.) (Scrophulariaceae) and Dalmatian toadflax ( Linaria genistifolia (L.) P. Mill. ssp. dalmatica). The beetles are more common on yellow toadflax than on Dalmatian toadflax. To understand their distribution on the two host plants, we investigated whether they prefer one host to the other and whether individuals aggregate toward conspecifics. In field and laboratory experiments where beetles were presented with a choice of both toadflax species, B. pulicarius sampled from both host plants preferred yellow toadflax. However, in the laboratory experiment, beetles collected from Dalmatian toadflax showed a weaker preference for yellow toadflax than beetles collected from yellow toadflax. In the field experiment, all beetle populations sampled showed similar preferences. When given a choice between yellow toadflax plants with and without trapped adult B. pulicarius, beetles preferred plants with conspecifics, suggesting aggregation toward beetle pheromones or host-plant volatiles induced by beetle activity. These results do not support the current practice of redistributing North American B. pulicarius onto Dalmatian toadflax because of their preference for yellow toadflax. [ABSTRACT FROM AUTHOR]