Inhibition between invasives: a newly introduced predator moderates the impacts of a previously established invasive predator

Abstract

Summary 1.With continued globalization, species are being transported and introduced into novel habitats at an accelerating rate. Interactions between invasive species may provide important mechanisms that moderate their impacts on native species. 2. The European green crab Carcinus maenas is an aggressive predator that was introduced to the east coast of North America in the mid-1800s and is capable of rapid consumption of bivalve prey. A newer invasive predator, the Asian shore crab Hemigrapsus sanguineus , was first discovered on the Atlantic coast in the 1980s, and now inhabits many of the same regions as C. maenas within the Gulf of Maine. Using a series of field and laboratory investigations, we examined the consequences of interactions between these predators. 3. Density patterns of these two species at different spatial scales are consistent with negative interactions. As a result of these interactions, C. maenas alters its diet to consume fewer mussels, its preferred prey, in the presence of H. sanguineus . Decreased mussel consumption in turn leads to lower growth rates for C. maenas , with potential detrimental effects on C. maenas populations. 4. Rather than an invasional meltdown, this study demonstrates that, within the Gulf of Maine, this new invasive predator can moderate the impacts of the older invasive predator.

Mutualisms: Key Drivers of Invasions … Key Casualties of Invasions

“…The most dramatic changes have been documented in island ecosystems such as those on Hawaii (Waring et al 1993 ) and New Zealand dependence are the most robust against disturbances promoting extinctions (Ollerton et al 2003 ), such results suggest that the invasive species and its mutualists might be more resistant to disturbances, which would increase the probability of permanence and survival of such invasive in the network. This, added to a preferential interaction among invasive species, might lead to invasional meltdown, precipitating an even higher impact of the invasion on the native community, similar to those reported for other systems and interactions (see, for example, Grosholz 2005 ;Griffen et al 2008 ;Belote & Jones 2009 ).…”

Fitness-associated consequences of an omnivorous diet for the mangrove tree crab Aratus pisonii

“…For instance, blue crabs Callinectes sapidus in a contaminated estuary had reduced success capturing active prey items and consumed more algae, sediment, and detritus than those from an uncontaminated reference site (Reichmuth et al 2009). Additionally, the presence of the invasive Asian shore crab Hemigrapsus sanguineus forced the European green crab Carcinus maenas, a previously established invader, to decrease its mussel consumption and increase its consumption of red algae, a less preferable food source (Griffen et al 2008). This foraging shift to an algal-dominated diet is concurrent with reduced fecundity in C. maenas, and is likely a contributing factor to the regional replacement of C. maenas by H. sanguineus (Griffen et al 2011).…”

PopulationDynamics of Green Crabs (Carcinus maenas) -- A Review

“…In the presence of H. sanguineus, C. maenas not only occupies a less-desirable habitat but also alters its diet from bivalves, its preferred prey, to consume more algae [211]. In laboratory experiments green crabs were superior competitors to both blue crabs and Asian shore crabs [234], but that does not seem to be the case in the wild.…”

“…Hemigrapsus sanguineus [211]. The wide variety of prey items that C. maenas consumes indicates that they are resilient, and can survive on whatever food is available [29].…”