Identifying the mechanisms underlying biological invasions can inform the management of invasive species. The enemy release hypothesis (ERH) suggests that invasive species have a competitive advantage in their introduced range because they leave behind many of their predators and parasites from their native range, allowing them to shift resources from defences to growth, reproduction and dispersal. Many studies have demonstrated that invasive species have fewer parasites than their native counterparts, but few studies have tested whether the loss of these natural enemies appears to be a primary driver of the invasion process. To test the ERH, we conducted a mark–recapture study in which we used an anthelmintic drug to successfully reduce parasitic worms in invasive Cuban treefrogs Osteopilus septentrionalis and native treefrogs (Hyla spp.) at half of 12 wetlands, marking nearly 4,200 frogs. If the ERH is supported, we would expect that treating for parasitic worms would have a greater benefit to native than invasive hosts. Growth and survival rates of invasive and native treefrogs responded similarly to the anthelmintic treatment, suggesting that the Cuban treefrog's release from parasitic worms does not appear to significantly contribute to its invasiveness in established areas. Instead, it appears that the overall faster rates of growth and maturation, higher survival rates and larger body sizes of Cuban treefrogs that we observed may contribute to their expansion and proliferation. Synthesis and applications. Although Cuban treefrogs have a lower diversity of parasitic worms in their invasive than native range, this does not appear to significantly contribute to their invasion success in areas where they have been established for more than 20 years. This suggests that any manipulation of parasites in invasive or native hosts would not be an effective method of controlling Cuban treefrogs or reducing their impacts. Further research into other hypotheses is needed to explain the Cuban treefrog's success and help guide management actions to reduce their spread and negative impacts. Our study demonstrates that enemy release may not be a primary driver of invasiveness, highlighting the need for more experimental tests of the enemy release hypothesis to examine its generality.

For migratory landbird species, large expanses of open water or inhospitable areas provide unique challenges during migration. Research on the strategies that species use to navigate barriers can yield insights into the factors shaping the evolution of migration and facilitate the identification of critical staging areas prior to barrier crossing. One such barrier, the Caribbean Sea, has received little study but must be negotiated by ≈50 migratory landbirds as they fly from South America to North America in spring. Recent discoveries from the gray‐cheeked thrush Catharus minimus, which undertakes non‐stop flights >3000 km across the Caribbean Sea, raises the possibility that the breadth of potential strategies has been unappreciated thus far. We calculated fuel load and potential flight range in 9985 individuals of 16 species captured over 10 years at two stopover sites in northern Colombia to 1) evaluate the likely migratory strategy of these species as they depart northern Colombia in spring, and 2) evaluate the influence of family, diet, morphology and migratory distance on potential flight range. We found considerable variation in flight ranges and therefore strategies for crossing the Caribbean Sea/Gulf of Mexico barrier complex. In addition to gray‐cheeked thrush, non‐stop flights >2500 km were possible in yellow‐billed cuckoo Coccyzus americanus, yellow warbler Setophaga petechia and northern waterthrush Parkesia noveboracensis. The remaining species were either capable of over‐water flights to the Yucatan Peninsula/Cuba (>1800 km) or shorter flights to middle Central America (>1000 km) and likely required one or more stopovers to reach North America. Predicted flight ranges were influenced by morphology but not by distance, diet or taxonomic group, providing a novel insight into the evolution of migratory strategies. Our study confirms the vital role northern Colombia performs in providing energy for migratory birds and highlights the Caribbean as a key migratory barrier for many species.

Se evaluó un cultivo de hortensias de exportación en el municipio de La Ceja del Tambo (Antioquia, Colombia) a través de un Análisis de Ciclo de Vida (ACV). El alcance fue de la puerta a la puerta contemplando las etapas de siembra, cultivo y empacado. El inventario para el análisis fue obtenido a partir de observaciones de campo, relacionado con la base de datos Ecoinvent 3.3 y posteriormente procesado en el software Umberto NXT LCA 14. Las metodologías Recipe Midpoint y Endpoint se utilizaron para evaluar las cargas ambientales del sistema de producción sobre las diferentes categorías de impacto (ocupación del suelo, cambio climático, agotamiento de los recursos fósiles y agotamiento de los metales). Los resultados mostraron que la etapa de cultivo presentó el mayor impacto sobre el agotamiento de recursos fósiles con un valor de 1,08 kg petróleo Eq. Finalmente, mediante la toma de decisiones ambientales se realizaron las respectivas recomendaciones para la reducción de los impactos resultantes, principalmente en la etapa de cultivo. Se realizó una simulación con los cambios propuestos en el sistema productivo, logrando una reducción del 39% de los impactos ambientales totales del mismo.

1. Introduced hosts are capable of introducing parasite species and altering the abundance of parasites that are already present in native hosts, but few studies have compared the tolerances of native and invasive hosts to introduced parasites or identified the traits of introduced hosts that make them supershedders of nonnative parasites.2. Here, we compare the effects of a nematode Aplectana hamatospicula that is native to Cuba but appears to be introduced to Florida on the native Floridian treefrog, Hyla femoralis, and on the Cuban treefrog (CTF), Osteopilus septentrionalis. We were particularly interested in CTFs because their introduction to Florida has led to reported declines of native treefrogs.3. In the laboratory, infection with A. hamatospicula caused a greater loss in body mass of H. femoralis than CTFs despite H. femoralis shedding fewer total worms in their faeces than CTFs. Field collections of CTFs, H. femoralis, and another native Floridian treefrog, H. squirella (Squirrel treefrog) from Tampa, FL also showed that CTFs shed more larval worms in their faeces than both native frogs when controlling for body size. Hence, the non-native CTF is a supershedder of this non-native parasite that is spilling over to less tolerant native treefrogs. Any conservation intervention to reduce the effects of CTFs on native treefrogswould benefit from knowing the traits that contribute to the invasive host being a supershedder of this parasite. Hence, we conducted necropsies on 330 CTFs to determine how host sex and body size affect the abundance of A. hamatospicula, and two other common parasites in this species (acuariid nematodes and trematode metacercariae).5. There was a significant linear increase in A. hamatospicula and encysted acuariids with CTF body size, but there was no detectable relationship between host body size and the intensity of metacercariae. Female CTFs were bigger, lived longer and, on average, had more A. hamatospicula than male CTFs. 6. Synthesis and applications. These results of the study suggest that there is parasite spillover from the invasive Cuban treefrog (CTF) to native treefrogs in Florida.