Unexpected Ecological Effects of Distributing the Exotic Weevil, <i>Larinus planus</i> (F.), for the Biological Control of Canada Thistle
Why this work is in the frame
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Bibliographic record
Abstract
Rhinocyllus conicus, a weevil introduced for biological control of exotic weeds, has had major nontarget ecological effects on native thistles. Some practitioners have argued that this is an isolated case. We report, however, that another Eurasian weevil (Larinus planus), currently being distributed in North America for the control of Canada thistle (Cirsium arvense), is significantly reducing seed production by a native thistle (Tracy’s thistle, Cirsium undulatum var. tracyi) in Colorado. In 1999 we discovered L. planus feeding in flower heads of Tracy’s thistle near a 1992–1993 biocontrol release site. Of the heads collected, 74% had evidence of L. planus, and these heads produced only 1.1 viable seeds on average, compared with 45.9 in heads without this weevil. In 2000 we investigated whether L. planus feeding persisted on Tracy’s thistle and whether this feeding affected seed production significantly. Feeding by L. planus occurred on 80% of the plants and in 76% of all the main heads of Tracy’s thistle. Flower heads with L. planus averaged 1.4 viable seeds, compared with 44.5 in uninfested heads. Feeding by L. planus decreased the average number of viable seeds produced per plant by over 51%. In contrast, L. planus had less effect on its targeted exotic host, Canada thistle than it did on Tracy’s thistle. The high-frequency and high-level feeding of L. planus on the native species, coupled with the lack of evidence of its effectively limiting the seed production or density of Canada thistle suggest that the deliberate distribution of this weevil entails a high risk-to-benefit ratio and should be discontinued. Our findings challenge the general assumption that biological control with exotic insects is consistent with conservation goals of weed management in natural areas. Effective, a priori quantitative evaluation of the potential effects on both target and nontarget species and better regulatory oversight are required. Resumen: Efectos Ecológicos Inesperados de la Distribución del Gorgojo Exótico, Larinus planus (F.), para el Control Biológico del Cardo de Canadá: Rhinocyllus conicus, un gorgojo introducido para el control de hierbas exóticas, ha tenido importantes efectos ecológicos en cardos nativos. Sin embargo, algunos profesionales han argumentado que este es un caso aislado. Reportamos que otro gorgojo eurasiático (Larinus planus), que actualmente está siendo distribuido en Norte América para el control del Cardo de Canadá (Cirsium arvense), esta reduciendo significativamente la producción de semillas de un cardo nativo (Cirsium undulatum var. tracyi) en Colorado. En 1999 descubrimos a L. planus alimentándose de flores de C. undulatum cerca de un sitio de liberación de biocontrol en 1992–1993. De las flores recolectadas, el 74 % tenía evidencia de L. planus y estas flores produjeron solo 1.1 semillas viables en promedio, en comparcaión con 45.9 en flores sin este gorgojo. En 2000 investigamos si persistía la alimentación de L. planus en el cardo nativo y si esto afectaba la producción de semillas significativamente. El forrajeo de L. planus ocurrió en el 80% de las plantas y en el 76% de las flores del cardo nativo. Las flores con L. planus promediaron 1.4 semillas viables, comparadas con 44.5 en flores no infestadas. El forrajeo de L. planus disminuyó el número promedio de semillas viables producidas por planta en más del 51%. En contraste, L. planus tuvo menor efecto en su hospedero exótico, C. arvense, que en el cardo nativo. La alta frecuencia y nivel de L. planus alimentándose de la especie nativa, aunado a la falta de evidencia de algún efecto sobre la producción de semillas o la densidad de C. arvense, sugieren que la distribución deliberada de este cardo conlleva una alta proporción de riesgo a beneficio y debe descontinuarse. Nuestros resultados desafían la suposición general de que el control biológico con insectos exóticos es consistente con las metas de conservación del manejo de arbustos en áreas naturales. Se requieren evaluaciones cuantitativas efectivas, a priori, de los efectos potenciales tanto en especies blanco como no blanco, así como mayor vigilancia.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.009 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.002 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it