Impact of an introduced Crustacean on the trophic webs of Mediterranean wetlands

Abstract

Based on a review and our own data, we present an overview of the ecological impacts on the trophic web of Mediterranean wetlands by an introduced Decapod Crustacean, the red swamp crayfish (Procambarus clarkii). P. clarkii lacks efficient dispersal mechanisms but is very well adapted to the ecological conditions of Mediterranean wetlands (fluctuating hydroperiods with regular intervals of drought). As an opportunistic, omnivorous species, which adapts its ecology and life history characteristics, such as timing and size at reproduction to changing environmental conditions, it became readily established in most of the Mediterranean wetland environments. High reproductive output, short development time and a flexible feeding strategy are responsible for its success as an invader. Like most crayfish, it occupies a keystone position in the trophic web of the invaded system and interacts strongly with various trophic levels. It efficiently grazes on macrophytes and is one of the main factors, besides the impact of flamingos, cattle and introduced fish, of the change of many water bodies from a macrophyte dominated, clear water equilibrium to a phytoplankton driven turbid water balance. Juveniles feed on protein rich animal food with the corresponding impact on the macroinvertebrate community in competition with other crayfish or fish species. At the same time, it serves as a prey for mammals, birds and fish. Due to its predatory and grazing activity, it efficiently canalises energy pathways reducing food web complexity and structure. Feeding also on detritus it opens, especially in marshlands, the detritic food chain to higher trophic levels which results in an increase of crayfish predators. As a vector of diseases, it has a severe impact on the preservation and reintroduction of native crayfish. P. clarkii accumulates heavy metals and other pollutants in its organs and body tissues and transmits them to higher trophic levels. Due to the long history of its presence, the complex interactions it established within the invaded ecosystems and the socio-economic benefits it provides to humans, prevention and control seem the most promising management measures to reduce the negative impact of this crayfish species. Biological Invasions (2005) 7: 49-73 Ó Springer 2005 ) High fecundity ++ Short generation and juvenile development times ++ Fast adaptation to environmental stress +++ High tolerance to environmental heterogeneity +++ Desirability to and association with humans (edibility, game species) +++ Additional features Omnivory +++ Brood care +++

Home-field advantage: native signal crayfish (Pacifastacus leniusculus) out consume newly introduced crayfishes for invasive Chinese mystery snail (Bellamya chinensis)

“…The highly aggressive behavior, potential for rapid population increase, and omnivorous feeding habits of P. clarkii have resulted in numerous ecological impacts manifested across entire lake food webs (e.g., Geiger et al 2005;Gherardi 2006; Gherardi and Acquistapace 2007). P. clarkii was first recorded in Washington in the summer of 2000 (Mueller 2001).…”

“…Crayfish are important polytrophic consumers in temperate freshwater environments and play a central ecological role by providing a direct link from primary production and detrital-based food webs to fish and terrestrial predators (Nyström et al 1996). Small-scale experiments and field studies have demonstrated significant ecological impacts of P. clarkii and O. virilis on detritus, macrophytes, benthic insects, snails, crayfishes and fish in lotic and lentic waters (e.g., Chambers et al 1990;Geiger et al 2005;Gherardi 2006;Gherardi and Acquistapace 2007). These species have only recently been documented in Washington (Mueller 2001;Larson and Olden 2008) and are invading a freshwater landscape occupied by a single native crayfish species-the signal crayfish (Pacifastacus leniusculus) (Fig.…”

Invasive predatory crayfish do not trigger inducible defences in tadpoles

“…This generalization of detection capability to novel predator species, however, gets dampened with increasing phylogenetic distance among predator species [28], and no indigenous crayfish species have been known in the Doñ ana area. The red swamp crayfish was introduced in the surroundings of Doñ ana National Park in 1974, and it has since unevenly expanded across marshy areas and into ponds throughout the park [29], although it has not reached the southernmost part of the park. Rana perezi is widely extended throughout the park, including a number of isolated ponds to the south that remain free of invasive crayfish.…”

The importance of allochthonous litter input on the biomass of an alien crayfish in farm ponds

“…This type of indirect interaction is also similar to ''hyperpredation'' when the shared predator is an exotic species (Smith and Quin 1996). Hyperpredation is a notorious mechanism causing severe declines and even extinctions of native species (Norbury 2001;Roemer et al 2002;Courchamp et al 2003;White et al 2006), and this mechanism may explain why exotic red swamp crayfish have large impacts on native ecosystems (Maezono and Miyashita 2004;Geiger et al 2005;Gherardi and Acquistapace 2007).…”

“…Here, we focused on the red swamp crayfish which is a notorious invasive species introduced worldwide, reducing the abundance of aquatic macrophytes and insects (Holdich et al 1988;Maezono and Miyashita 2004;Geiger et al 2005;Gherardi and Acquistapace 2007). In Japan, the red swamp crayfish was introduced approximately 80 years ago and is now established widely in freshwater ecosystems (Ban 1980).…”