The invasive American bullfrog (Lithobates catesbeianus) in the Republic of Korea: history and recommendations for population control

Abstract

Ballast water is a leading vector for the introduction of aquatic invasive species worldwide and, once a novel species is established, regional ballast water exchange between ports can accelerate secondary spread. The importance of shipping induced invasions in the Laurentian Great Lakes has resulted in policies that require more stringent ballast water treatment standards for transoceanic shipping than is required of ships operating regionally within the Great Lakes. As a result, ballast water discharges within the Great Lakes are not well regulated, primarily because of the challenge of treating the high volumes of water carried by vessels that are confined to the waters of the Great Lakes. We used a discrete-time Markov chain model on a network with annual time-steps to simulate ballast water management scenarios at high-priority ports in the Great Lakes shipping network for two potential invaders, golden mussel (Limnoperna fortunei) and monkey goby (Neogobius fluviatilis). We chose high-priority ports by using graph-theoretic network analysis techniques to calculate six network centrality metrics for 151 ports in the network. Ports scoring high in network centrality scores have more ties with other ports or are positioned within the network such that they potentially have greater influence over the secondary spread of aquatic invasive species than other ports. We simulated secondary spread scenarios where hypothetical ballast water treatment was implemented at the top twenty ranked ports in each network centrality metric, as well as the top twenty busiest ports by ship arrivals. The results of each scenario were compared to a scenario where no management action was taken. Simulated secondary spread for both golden mussel and monkey goby resulted in significantly reduced infestation probabilities (p < 0.001) under all management scenarios when compared to unmanaged spread scenarios. Management at ports with inwardly directed ties to other ports reduced infestations by the greatest amount compared to other management scenarios; 65.4% for golden mussel and 74.6% for monkey goby. The indegree centrality of ports in the Great Lakes was found to be an important factor in governing secondary spread. Here we show that prioritized management, like high volume shore based treatment systems based on network centrality, is a potentially effective strategy for impeding the secondary spread of new or localized invasive species in the Great Lakes.

Disentangling the Impacts of Speciation, Sympatry and the Island Effect on the Morphology of Seven Hynobius sp. Salamanders

“…Moreover, climate change may be expected to result in a northern shift of species range to follow adequate ecological requirements [ 89 ], however, and despite the unlikeliness of such dispersal to happen, the current range borders for all three species prevent such shift. Finally the species are under threat because of invasive species such as Lithobates catesbeianus [ 90 ] emerging diseases such as Batrachochytrids [ 91 , 92 , 93 ], and the synergy of both type of invasive and pathogens being increasingly released in the environment [ 94 ].…”

Recommendations for IUCN Red List Conservation Status of the “Dryophytes immaculatus Group” in North East Asia

“…I determined the EOO and calculated the AOO of the species the same way as for D. suweonensis. Historically, both EOO and AOO were much larger as some subpopulations are known to have been extirpated within the last decades (Figure 3 and [33]), likely due to the synergy of several pressures, which included the presence of the invasive Lithobates catesbeianus [46,98].…”

Preliminary Recommendations for National IUCN Red Listing Conservation Status of the “<em>Dryophytes immaculatus</em> group” in North East Asia

“…Historically, both EOO and AOO would have been much larger as some sub-populations are known to have been extirpated within the last decades ( Fig. 2 and [32]), likely due to the synergy of several pressures, among which the presence of the invasive Lithobates catesbeianus [55,93].…”