Dynamics and population structure of native <i>Echinogammarus stammeri</i> (Karaman, 1931) (Crustacea: Amphipoda) and non-native <i>Gammarus roeselii</i> Gervais, 1835 (Crustacea: Amphipoda) occurring in sympatry in Northern Italy

Freshwater ecosystems rely on allochthonous resources. Integration of these subsidies depends on diversity of both terrestrial resources and aquatic shredder and decomposer communities, but the diversity effects on leaf litter breakdown and decomposition are less clear in aquatic than terrestrial ecosystems. We need a better understanding of this relationship because aquatic communities are rapidly changing with species invasions and anthropogenic impacts. Here, we experimentally disentangled the effects of leaf and shredder richness on leaf litter breakdown by macroinvertebrates in mesocosm experiments using three species of amphipods, a dominant guild of crustaceans in European freshwater ecosystems. Increased leaf richness led to lower‐than‐predicted leaf consumption by native shredders, with mixed evidence of resource‐switching or prioritization of preferred food items within a leaf mix. Higher shredder species richness never promoted leaf consumption rates compared to predictions from relevant single‐species experiments, and instead sometimes substantially decreased leaf consumption. We then conducted a meta‐analysis of leaf litter consumption rates by seven widely distributed amphipod species (the three used in the experiments and four additional species). As expected based on our own experiments, nonnative amphipod species generally had lower biomass‐adjusted leaf litter consumption rates, although their larger body size led to higher per‐individual leaf consumption rates. Contamination of the water by metals, pesticides, and other chemicals additionally significantly decreased leaf litter consumption by multiple native and nonnative species compared to unpolluted systems. While the meta‐analysis suggested that litter consumption, and thus breakdown, would decline if native shredders are replaced by nonnative heterospecifics, complete species replacement is not the only outcome following immigration in a meta‐community context. Our experiments suggest that breakdown rates could remain reasonably high where native species coexist with nonnative arrivals. Experiments that neglect the ecological realism of species coexistence will necessarily mischaracterize effects on ecosystem functioning.

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“…(); 13, Goedmakers (); 14, Paganelli et al. (); 15, Devin et al. (); 16, Pinkster (), 17, Pöckl et al.…”

Section: Methodsmentioning

confidence: 99%

Species turnover and invasion of dominant freshwater invertebrates alter biodiversity–ecosystem‐function relationship

Little

Altermatt

2018

Ecological Monographs

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“…This may have facilitated the invasion success of this gammarid crustacean across European waters (e.g., Hesselschwerdt et al, 2009; Paganelli et al, 2015). In fact, Piscart et al (2010) and Paganelli et al (2016) considered G. roeselii as a well‐naturalized species with a long invasion history in Eastern and Central Europe. At the same time, the host–parasite system of G. roeselii could not be considered as an established self‐regulated system and thus the population of this host can further succeed and occupy new geographic areas.…”

Section: Discussionmentioning

confidence: 99%

Symbiotic species diversity can explain invasion success and host–parasite system stability: The case of gammarid hosts

Sarabeev,

Balbuena,

Oros

et al. 2024

Ecosphere

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A major current challenge related to invasions is the absence of a comprehensive theoretical basis for preventing the introduction of alien species and controlling their populations. By using a macroecological framework, we aim to examine patterns of symbiotic species diversity across native and invasive hosts to understand the mechanisms underlying the host–parasite system stability. The symbiotic communities of seven gammarid species, two native and five invasive, were analyzed at 16 fresh and brackish water sites along the Baltic coast of Poland. We investigated the influence of four factors—locality, habitat, host species, and host origin—on diversity patterns and assessed their relative contribution to diversity variation. Our results indicate that all factors are crucial in determining the composition and abundance of symbiotic communities in gammarids. Among these factors, locality and host species apparently have a greater influence on symbiotic communities than habitat conditions and host origin. Comparative analysis of diversity indexes of symbiotic organisms from native and invasive hosts showed that the richer communities of native gammarids were paradoxically less diverse. We assume that these rich and uneven symbiotic communities keep the host–parasite system of native gammarids in equilibrium. Highly dominant symbiotic species with a high load per host individual may stabilize the growth of the host population. Symbiotic communities of the invasive host exhibited lower species richness but displayed a relatively even distribution of species with moderate loads per individual, resulting in a scarcity of heavily infected gammarids within the population. Thus, the survival rate of invasive gammarids is expected to be relatively high, facilitating their population growth and further spread. We conclude that complex communities of native gammarids constructed from many symbiotic species may prevent host populations from undergoing explosive growth, while such mechanisms may be completely or partially reduced in invasive hosts.

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“…Hesselschwerdt et al, 2009;Paganelli et al, 2015). In fact, Piscart et al (2010) and Paganelli et al (2016) considered G. roeselii as a well-naturalised species with a long invasion history in Eastern and Central Europe. At the same time, the host-parasite system of G. roeselii could not be considered as an established self-regulated system and thus the population of this host can further succeed and occupy new geographic areas.…”

Section: Hypotheses Evaluationmentioning

confidence: 99%

Symbiotic species diversity can explain invasion success and stability of the host-parasite system: the case of native and invasive gammarids (Crustacea, Amphipoda)

Sarabeev

Balbuena

Oros

et al. 2023

Preprint

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The major current challenge related to alien species is the absence of a comprehensive theoretical basis to explain the resistance from bioinvasions. One of the factors conferring resistance to invasion is the native species diversity of a recipient ecosystem. We aim to examine patterns of species diversity to understand the mechanisms underlying host-parasite relationships in alien species. The dataset represents 20 host-locality samples, including over 15,067,600 symbiotic organisms counted from 612 host individuals belonging to 7 gammarid species, two native and five invasive, sampled at 16 localities in the Baltic region of Poland. We asked whether diversity patterns depended on locality, habitat and host species, and which factors are deterministic in the variation of diversity. Our results suggest that both locality and host phylogeny are critical factors in determining the composition and abundance of symbiotic communities in gammarids. Out of these two factors, locality appears to be more determinant of the symbiotic community of gammarids than host species, whereas habitat condition was a stronger determinant of the symbiotic communities than geographic distance. The rich and uneven symbiotic communities of native gammarids keep the host-parasite system in equilibrium. Sharply dominated symbiotic species with a high load per host individual stabilize the host population. Simplified symbiotic communities of the invasive hosts showed a relatively even distribution of species with moderate loads per individual, with heavily infected gammarids being rare in the population. The survival rate of invasive gammarids is expected to be relatively high, facilitating their population growth and further spread. Complex communities of the native gammarids constructed from many symbiotic species may prevent host populations from undergoing explosive growth, while such mechanisms may be completely or partially reduced in invasive hosts.

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Dynamics and population structure of native Echinogammarus stammeri (Karaman, 1931) (Crustacea: Amphipoda) and non-native Gammarus roeselii Gervais, 1835 (Crustacea: Amphipoda) occurring in sympatry in Northern Italy

Cited by 5 publications

References 29 publications

Species turnover and invasion of dominant freshwater invertebrates alter biodiversity–ecosystem‐function relationship

Species turnover and invasion of dominant freshwater invertebrates alter biodiversity–ecosystem‐function relationship

Symbiotic species diversity can explain invasion success and host–parasite system stability: The case of gammarid hosts

Symbiotic species diversity can explain invasion success and stability of the host-parasite system: the case of native and invasive gammarids (Crustacea, Amphipoda)

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