Biological Invasions

Cooke, Sophia C.; Anchundia, David; Caton, Emma; Haskell, Lucy E.; Jäger, Heinke; Kalki, Yatindra; Mollá, Óscar; Rodríguez, Jacqueline; Schramer, Tristan D.; Walentowitz, Anna; Fessl, Birgit

doi: 10.1007/s10530-020-02251-3pmid: N/A

The introduced smooth-billed ani Crotophaga ani has become widespread across the Galápagos archipelago in the past half-century. It is known to predate upon a range of native and endemic species, and is a potential vector for the spread of invasive plants and parasites. Here we report previously undocumented examples of smooth-billed ani predation in Galápagos, including that of an endemic racer snake and a scorpion. We highlight the possibility of smooth-billed anis having a serious impact on the endemic Galápagos carpenter bee, a major pollinator, as well as native and endemic Lepidopterans and other invertebrates. In addition, we report smooth-billed ani predation of other introduced species and note the importance of further research on the wide-scale impacts of smooth-billed anis in Galápagos and their role within the archipelago’s ecological networks.

Teschke, K.; Karez, R.; Schubert, P. R.; Beermann, J.

doi: 10.1007/s10530-020-02246-0pmid: N/A

The Pacific oyster, Magallana gigas, is an extremely successful invader with established populations in marine and estuarine habitats almost all over the world. Ecological implications of the introduction of this species to indigenous communities are well documented. However, the processes by which this species successfully establishes in a recipient community is still insufficiently understood. The early detection of the oyster at the island of Helgoland (North Sea) provided the ideal opportunity to investigate whether physical mechanisms, such as wave-exposure, influence their successful colonisation. We hypothesized that oyster colonisation benefits from wave-protected conditions. For this purpose, we evaluated colonisation success of M. gigas among wave-protected sites and wave-exposed sites along the island's pier system. The densities of M. gigas were significantly higher at wave-protected sites than at wave-exposed sites, and the frequency distributions of oyster lengths indicated better growth and higher survival rates in the harbours. This higher colonisation success at wave-protected sites may be explained by the relative retention time of water masses in the harbours, probably resulting in both reduced larval drift and lower energy demands for secretion formation (i.e. firmer binding to the substrate). The fact that the density of M. gigas can vary greatly on small spatial scales depending on exposure corroborates a multiple exposure sampling approach to monitor oyster populations in order to avoid potential overestimations of population sizes in given areas.

Hume, John B.; Luhring, Thomas M.; Wagner, C. Michael

doi: 10.1007/s10530-020-02242-4pmid: N/A

Widespread interest in the development of environmentally safe management actions has prompted research into the use of sensory cues to manipulate the movements of invasive species. The push–pull approach, for which attractive and repellent semiochemicals operate synergistically to guide individuals toward traps, has proven successful in insect pest management applications. We examined the effectiveness of a natural repellent (an alarm cue) and a natural attractant (a partial sex pheromone) in push-only (repel), pull-only (attract), and push–pull configurations, to guide invasive sea lamprey (Petromyzon marinus) toward and into a target trap during spawning migration into rivers. Using PIT telemetry to monitor sea lamprey movement within the river, we found that the alarm cue was capable of strongly altering sea lamprey distribution, “pushing” them toward target areas and generating rates of encounter with trap entrances sufficient to achieve trapping-for-control targets. Encounter rate with trap entrances was not improved, but performed more consistently, with the addition of the attractant in the push–pull configuration. There was evidence this could stem from a transition in internal state of motivation, from migration to reproduction. Use of the attractant alone was ineffective. No odor combination improved trap captures. We conclude that push–pull strategies will prove effective in guiding sea lamprey movements and recommend two improvements for subsequent testing in management scenarios: (1) use of a superior attractant (e.g. a sea lamprey migratory cue derived from conspecific larvae), and (2) its subsequent application to a capture methodology based on the entrainment of individuals near trap entrances.

May, Chelsea; Burness, Gary; Morrison, Brian; Fox, Michael G.

doi: 10.1007/s10530-020-02243-3pmid: N/A

Since its introduction to North America in the 1990s, the round goby has spread throughout the Great Lakes and inland movement into small tributaries, a new environment for this species in both its native and invaded ranges, is becoming more prevalent. We assessed spatial and temporal occupation of round gobies in four small streams in two systems in south-central Ontario, Canada to determine which habitat variables are the best predictors of round goby density. Two streams are tributaries of Lake Ontario and two are tributaries of the Otonabee River; all of these streams have barriers preventing upstream migration. Occupation and density patterns differed between the systems. In the Lake Ontario system, density was highest near the longitudinal centre of the stream between the mouth and first barrier, and round goby appeared to occupy these streams mainly from spring to fall. In the Otonabee River system, round goby occupied the streams year-round, and the most important factor determining adult density was distance from a barrier to upstream movement, with density highest next to the barriers. Adult density in Lake Ontario tributaries was highest in sites with a high percentage of cobble/boulder and a low percentage of gravel substrate, while substrate was less important in Otonabee River tributaries. Date was the strongest predictor of juvenile density, with density increasing through the sampling period in both systems. Occupation and density patterns may differ due to contrasting environmental conditions in the source environments and distance to the first barrier preventing upstream movement. This study shows diversity in invasion strategies, and provides insight into the ability of invasive species to change their occupation strategies based on the different environments they encounter.

Gervais, Jennifer A.; Kovach, Ryan; Sepulveda, Adam; Al-Chokhachy, Robert; Joseph Giersch, J.; Muhlfeld, Clint C.

doi: 10.1007/s10530-020-02244-2pmid: N/A

Climate change may facilitate the expansion of non-native invasive species (NIS) in aquatic and terrestrial systems. However, empirical evidence remains scarce and poorly synthesized at scales necessary for effective management. We conducted a literature synthesis to assess the state of research on the observed and predicted effects of climate change on a suite of 398 aquatic and terrestrial NIS now present in or a major threat to aquatic and terrestrial ecosystems of the Pacific Northwest (PNW), USA and British Columbia. Surprisingly, very few studies (n = 15) have investigated the observed effects of climate change on the distribution, abundance, spread, or impact of the focal NIS, with only five studies focusing on terrestrial (n = 2) or aquatic (n = 3) species within the PNW. Only 93 studies predicted the future dynamics of the focal NIS somewhere in their non-native range using climate model projections, yielding 117 species-specific predictions. However, only 30 of those studies generated predictions that overlapped with the PNW, and only six focused specifically on the expansion or abundance of NIS (n = 11 species) entirely within the region. Although our understanding of how climate change may interact with biological invasions is notably lacking, some evidence suggests that climate-induced NIS expansions are already underway in the PNW, particularly in aquatic ecosystems, and will be exacerbated by future changes in temperature and precipitation regimes. Better information is urgently needed for managers to implement strategic prevention, early detection, and proactive actions that ameliorate ecologically and economically devastating impacts of NIS.

Erickson, Kelley D.; Pratt, Paul D.; Rayamajhi, Min B.; Horvitz, Carol C.

doi: 10.1007/s10530-020-02249-xpmid: N/A

Multiple introductions are hypothesized to facilitate the success of invasive plant species, because they can result in novel genotypes through intraspecific hybridization potentially increasing the ability to adapt to the novel environment. In this study, we address the question of how the demography of an invader with multiple introductions and intraspecific hybridization varies across sites. This was done by modeling the population dynamics of Brazilian pepper, Schinus terebinthifolia Raddi (Anacardiaceae), a shrub native to Brazil, Paraguay and Argentina that has invaded the global subtropics and was introduced to Florida on two separate occasions. This species exhibits variability in growth form such that vertical and lateral growth are not strongly associated. Our demographic field work took place at six sites spanning the introduced range in Florida and differing in introduction history. For each site we constructed integral projection models where the probabilities of survival, growth and reproduction were modeled as functions of two different metrics of size, the continuous variables diameter and height, metrics of vertical and lateral growth, respectively. We performed a Life Table Response Experiment analysis to decompose the effects of variation among sites in vital rates on the population dynamics of S. terebinthifolia. We found that spatial variation in population dynamics was driven primarily by site-level differences in the maturation of seedlings into reproductive adults. The survival and growth of the largest individuals had the highest elasticity, suggesting that management actions capable of decreasing these vital rates would have the greatest effect on reducing the population growth rate.

Wondafrash, Mesfin; Slippers, Bernard; Nambazimana, Alphonsine; Kayumba, Isaac; Nibouche, Samuel; van der Lingen, Simon; Asfaw, Birhane A.; Jenya, Herbert; Mutitu, Eston K.; Makowe, Idea A.; Chungu, Donald; Kiwuso, Peter; Kulimushi, Emmanuel; Razafindrakotomamonjy, Andrianantenaina;

Luger, A. M.; South, J.; Alexander, M. E.; Ellender, B. R.; Weyl, O. L. F.; Nagelkerke, L. A. J.

doi: 10.1007/s10530-020-02252-2pmid: N/A

Predicting and understanding the impact of biological invaders is a global ecological imperative. Progress has been made through the application of phenomenological analysis via comparative functional response analysis. However, little is known about the mechanisms which drive high-magnitude functional responses of invasive species, especially when compared to trophically analogous natives. Largemouth bass Micropterus salmoides is a freshwater invasive species evaluated as a more efficient predator, with a higher-magnitude functional response, compared to a native analogue, the Cape kurper Sandelia capensis. In order to determine what traits drive this difference we quantified handling time behaviours (detection time, catch time, processing time) of both predator species and prey/predator size ratio, and employ an ecomorphological approach to determine whether largemouth bass is a more specialised predator than Cape kurper. There was no difference in detection time between the species, but largemouth bass were significantly and on average five times faster at catching prey than Cape kurper. Both species’ processing time was positively related to prey size, but Cape kurper was on average 4.5 times faster than largemouth bass. Ecomorphological data indicate that largemouth bass was the more specialised pursuit hunter for fish, whereas Cape kurper was better at ambush hunting. This suggests that the ecological impact of largemouth bass may be exacerbated in areas where there is habitat simplification which can lead to the extirpation of local small-bodied fish. In addition, there may be non-consumptive detrimental effects on trophically analogous natives through competitive exclusion.

Tierney, Paula A.; Caffrey, Joe M.; Vogel, Sebastian; Matthews, Sharon M.; Costantini, Emy; Holland, Celia V.

doi: 10.1007/s10530-020-02253-1pmid: N/A

Invasive species tend to acquire native parasites from their invaded range over time. In these cases, native host-parasite dynamics may be altered as a result of differences in parasite population biology and host competency between invasive and native hosts. Competent invasive hosts are likely to increase transmission to native hosts while incompetent invasive hosts may dilute infection in natives. In this study, we used a freshwater fish system and a survey approach to compare the host competency and population biology of a dominant helminth parasite, Pomphorhynchus tereticollis, between native brown trout (Salmo trutta) hosts and invasive dace (Leuciscus leuciscus) hosts over 2 years at the core and edge of dace’s invasive range in Ireland. Our results show that, although dace acquired P. tereticollis, dace had prevalent and high intensity infections of immature extra-intestinal worms while prevalence of adult worms was consistently higher in brown trout. The majority of parasite individuals infecting dace were immature extra-intestinal forms and, in contrast to brown trout, parasites in dace did not attain sexual maturity. In addition, brown trout from the invasion core where dace have been established the longest had a lower abundance of P. tereticollis, indicating that by taking up but not transmitting infective stages of the parasite, invasive dace may dilute P. tereticollis infection in the native host.Graphic abstract[graphic not available: see fulltext]

Kass, Jamie M.; Tingley, Morgan W.; Tetsuya, Tatsuyuki; Koike, Fumito

doi: 10.1007/s10530-020-02254-0pmid: N/A

Understanding species interactions and their effects on distributions is crucial for assessing the impacts of global change, particularly for invasive species. Co-occurrence models can help investigate these effects when interactions are likely given shared traits. For such an assemblage of invasive and native carnivorans, we examined how patterns of co-occurrence change across space and environmental gradients using a static multispecies occupancy model that accounts for imperfect detectability and models co-occurrence as a function of environmental variables, and also extended it to be temporally dynamic. We focused on invasive raccoons, which pose threats to humans and wildlife globally. In Japan, raccoons prey on many native taxa, but little is known about interactions with sympatric carnivorans. We searched for signals of competitive exclusion of native raccoon dogs (tanuki) and invasive masked palm civets by applying the model to detection data from a broad-scale trapping effort over 6 years. Forest cover was the strongest predictor of occupancy for individual species and raccoon co-occurrences, and raccoon occupancy probability increased with forest cover conditionally depending on the co-occurring carnivoran: only tanuki absence or civet presence had positive responses. However, tanuki occupancy probability increased with forest cover despite any co-occurrence. Thus, we found no evidence of competitive exclusion by raccoons, contrary to our expectations. As parts of the world with invasive raccoons can also have invasive tanuki, our findings may have broad management implications. The model we present should be useful for inferring signals of biotic interactions between species with low detectability over multi-year time frames.