The Horseshoe whip snake (Hemorrhois hippocrepis) on Ibiza: predator release in an invasive population

Abstract The key to fighting a biological invasion may lie in understanding every variable that can explain its success. The Enemy Release Hypothesis (ERH) states that when an invader arrives to a new environment, the absence of its common enemies (predators, parasites and competitors) facilitates the invasion success. The Horseshoe whip snake (Hemorrhois hippocrepis) has been recently introduced from the Iberian Peninsula to the island of Ibiza, and it is currently threatening the only endemic vertebrate, the Ibiza wall lizard (Podarcis pityusensis). We hypothesized that the snake invasion success is caused by the absence of natural predators, and we checked the ERH by relating the tail breakage rate to predation pressure. The invasive population showed a much lower incidence of tail breakage than the source population, which is in agreement with the almost absence of snake predators among the Ibizan reduced and naïve native vertebrate community. These results confirm the ERH, and support the prolongation of invasive snake trapping campaigns.

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Is invasion success explained by the enemy release hypothesis?

Ecology Letters ◽

10.1111/j.1461-0248.2004.00616.x ◽

2004 ◽

Vol 7 (8) ◽

pp. 721-733 ◽

Cited By ~ 745

Author(s):

Robert I. Colautti ◽

Anthony Ricciardi ◽

Igor A. Grigorovich ◽

Hugh J. MacIsaac

Keyword(s):

Enemy Release Hypothesis ◽

Invasion Success ◽

Enemy Release

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Increased immune marker variance in a population of invasive birds

Scientific Reports ◽

10.1038/s41598-020-78427-7 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Hanna Prüter ◽

Mathias Franz ◽

Sönke Twietmeyer ◽

Niklas Böhm ◽

Gudrun Middendorff ◽

...

Keyword(s):

Invasive Species ◽

Parasite Burden ◽

Parasite Prevalence ◽

Invasion Success ◽

Enemy Release ◽

Invasive Population ◽

Physiological Cost ◽

Mean And Variance ◽

Eosinophil Granulocytes ◽

Invasive Birds

AbstractImmunity and parasites have been linked to the success of invasive species. Especially lower parasite burden in invasive populations has been suggested to enable a general downregulation of immune investment (Enemy Release and Evolution of Increased Competitive Ability Hypotheses). Simultaneously, keeping high immune competence towards potentially newly acquired parasites in the invasive range is essential to allow population growth. To investigate the variation of immune effectors of invasive species, we compared the mean and variance of multiple immune effectors in the context of parasite prevalence in an invasive and a native Egyptian goose (Alopochen aegyptiacus) population. Three of ten immune effectors measured showed higher variance in the invasive population. Mean levels were higher in the invasive population for three effectors but lower for eosinophil granulocytes. Parasite prevalence depended on the parasite taxa investigated. We suggest that variation of specific immune effectors, which may be important for invasion success, may lead to higher variance and enable invasive species to reduce the overall physiological cost of immunity while maintaining the ability to efficiently defend against novel parasites encountered.

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Parasites and invasions: changes in gastrointestinal helminth assemblages in invasive and native rodents in senegal

10.1101/053082 ◽

2016 ◽

Author(s):

Christophe Diagne ◽

Alexis Ribas ◽

Nathalie Charbonnel ◽

Ambroise Dalecky ◽

Caroline Tatard ◽

...

Keyword(s):

Rattus Rattus ◽

Enemy Release Hypothesis ◽

Hymenolepis Diminuta ◽

Invasion Success ◽

Transmission Risk ◽

Enemy Release ◽

Individual Species ◽

Mus Musculus Domesticus ◽

Gastrointestinal Helminth ◽

Invasion Fronts

AbstractUnderstanding why some exotic species become widespread and abundant in their colonized range is a fundamental issue that still needs to be addressed. Among many hypotheses, newly established host populations may benefit from a parasite loss (“enemy release” hypothesis) through impoverishment of their original parasite communities or reduced infection levels. Moreover, the fitness of competing native hosts may be affected by the acquisition of exotic taxa from invaders (“parasite spillover”) and/or by an increased transmission risk of native parasites due to their amplification by invaders (“parasite spillback”). We focused on gastrointestinal helminth communities to determine whether these predictions could explain the ongoing invasion success of the commensal house mouse (Mus musculus domesticus) and black rat (Rattus rattus), as well as the associated drop of native Mastomys species, in Senegal. For both invasive species, our results were consistent with the predictions of the enemy release hypothesis. A decrease of helminth overall prevalence and individual species richness was observed along the invasion gradients as well as lower specific prevalence/abundance (Aspiculuris tetraptera in M. m. domesticus, Hymenolepis diminuta in R. rattus) on the invasion fronts. Conversely, we did not find strong evidence of helminth spill-over or spill-back in invasion fronts, where native and invasive rodents co-occurred. Further experimental research is needed to determine whether and how the loss of helminths and reduced infection levels along invasion routes may result in any advantageous effects on invader fitness and competitive advantage.

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Release from Above- and Belowground Insect Herbivory Mediates Invasion Dynamics and Impact of an Exotic Plant

Plants ◽

10.3390/plants8120544 ◽

2019 ◽

Vol 8 (12) ◽

pp. 544

Author(s):

Lotte Korell ◽

Martin Schädler ◽

Roland Brandl ◽

Susanne Schreiter ◽

Harald Auge

Keyword(s):

Population Dynamics ◽

Plant Species ◽

Plant Community ◽

Enemy Release Hypothesis ◽

Invasion Success ◽

Enemy Release ◽

Native Plant ◽

Invasion Dynamics ◽

Long Term Studies

The enemy-release hypothesis is one of the most popular but also most discussed hypotheses to explain invasion success. However, there is a lack of explicit, experimental tests of predictions of the enemy-release hypothesis (ERH), particularly regarding the effects of above- and belowground herbivory. Long-term studies investigating the relative effect of herbivores on invasive vs. native plant species within a community are still lacking. Here, we report on a long-term field experiment in an old-field community, invaded by Solidago canadensis s. l., with exclusion of above- and belowground insect herbivores. We monitored population dynamics of the invader and changes in the diversity and functioning of the plant community across eight years. Above- and belowground insects favoured the establishment of the invasive plant species and thereby increased biomass and decreased diversity of the plant community. Effects of invertebrate herbivores on population dynamics of S. canadensis appeared after six years and increased over time, suggesting that long-term studies are needed to understand invasion dynamics and consequences for plant community structure. We suggest that the release from co-evolved trophic linkages is of importance not only for the effect of invasive species on ecosystems, but also for the functioning of novel species assemblages arising from climate change.

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Testing the enemy release hypothesis: trematode parasites in the non-indigenous Manila clam Ruditapes philippinarum

Hydrobiologia ◽

10.1007/s10750-009-9786-9 ◽

2009 ◽

Vol 630 (1) ◽

pp. 139-148 ◽

Cited By ~ 18

Author(s):

C. Dang ◽

X. de Montaudouin ◽

J. Bald ◽

F. Jude ◽

N. Raymond ◽

...

Keyword(s):

Ruditapes Philippinarum ◽

Enemy Release Hypothesis ◽

Manila Clam ◽

Enemy Release ◽

Trematode Parasites

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Testing the enemy release hypothesis in a native insect species with an expanding range

PeerJ ◽

10.7717/peerj.1415 ◽

2015 ◽

Vol 3 ◽

pp. e1415 ◽

Cited By ~ 3

Author(s):

Julia J. Mlynarek

Keyword(s):

Related Species ◽

Enemy Release Hypothesis ◽

Enemy Release ◽

Infection Prevalence ◽

Water Mite ◽

Closely Related Species ◽

Study Region ◽

Ecological Release ◽

Non Invasive ◽

Enallagma Boreale

The enemy release hypothesis (ERH) predicts that the spread of (invasive) species will be facilitated by release from their enemies as they occupy new areas. However, the ERH is rarely tested on native (non-invasive, long established) species with expanding or shifting ranges. I tested the ERH for a native damselfly (Enallagma clausum) whose range has recently expanded in western Canada, with respect to its water mite and gregarine parasites. Parasitism levels (prevalence and intensity) were also compared betweenE. clausumand a closely related species,Enallagma boreale, which has long been established in the study region and whose range is not shifting. A total of 1,150 damselflies were collected at three ‘old’ sites forE. clausumin Saskatchewan, and three ‘new’ sites in Alberta. A little more than a quarter of the damselflies collected were parasitized with, on average, 18 water mite individuals, and 20% were parasitized by, on average, 10 gregarine individuals. I assessed whether the differences between levels of infection (prevalence and intensity) were due to site type or host species. The ERH was not supported:Enallagma clausumhas higher or the same levels of parasitism in new sites than old sites. However,E. borealeseems to be benefitting from the recent range expansion of a native, closely related species through ecological release from its parasites because the parasites may be choosing to infest the novel, potentially naïve, host instead of the well-established host.

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Time-since-invasion increases native mesoherbivore feeding rates on the invasive alga, Sargassum muticum (Yendo) Fensholt

Journal of the Marine Biological Association of the United Kingdom ◽

10.1017/s0025315417001539 ◽

2017 ◽

Vol 98 (8) ◽

pp. 1935-1944 ◽

Cited By ~ 2

Author(s):

Martyn Kurr ◽

Andrew J. Davies

Keyword(s):

Invasive Plants ◽

Enemy Release Hypothesis ◽

Sargassum Muticum ◽

Enemy Release ◽

Feeding Rates ◽

Herbivore Species ◽

Feeding Trials ◽

Negative Impacts ◽

Abundance And Diversity ◽

Invasive Alga

Invasive algae can have substantial negative impacts in their invaded ranges. One widely cited mechanism that attempts to explain how invasive plants and algae are often able to spread quickly, and even become dominant in their invaded ranges, is the Enemy Release Hypothesis. This study assessed the feeding behaviours of two species of gastropod herbivore from populations exposed to the invasive alga Sargassum muticum for different lengths of time. Feeding trials, consisting of both choice and no-choice, showed that the herbivores from older stands (35–40 years established) of S. muticum were more likely to feed upon it than those taken from younger (10–19 years established) stands. These findings provide evidence in support of the ERH, by showing that herbivores consumed less S. muticum if they were not experienced with it. These findings are in accordance with the results of other feeding-trials with S. muticum, but in contrast to research that utilizes observations of herbivore abundance and diversity to assess top-down pressure. The former tend to validate the ERH, and the latter typically reject it. The potential causes of this disparity are discussed, as are the importance of palatability, herbivore species and time-since-invasion when considering research into the ERH. This study takes an important, yet neglected, approach to the study of invasive ecology.

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Invasive toads adopt marked capital breeding when introduced to a cooler, more seasonal environment

Biological Journal of the Linnean Society ◽

10.1093/biolinnean/blz119 ◽

2019 ◽

Vol 128 (3) ◽

pp. 657-671 ◽

Cited By ~ 6

Author(s):

Giovanni Vimercati ◽

Sarah J Davies ◽

John Measey

Keyword(s):

Resource Allocation ◽

Breeding Season ◽

Breeding Strategy ◽

Source Population ◽

Invasive Population ◽

Starvation Resistance ◽

Fat Percentage ◽

Capital Breeding ◽

Seasonal Environment ◽

Structural Mass

Abstract Amphibians from cold and seasonal environments show marked capital breeding and sustained resource allocation to growth when compared with conspecifics from warmer, less seasonal environments. Capital breeding fuels reproduction by using only stored energy, and larger sizes and masses confer higher fecundity, starvation resistance and heat and water retention. Invasive populations act as experiments to explore how resources are allocated in novel environments. We investigated resource allocation of the southern African toad Sclerophrys gutturalis in a native source population (Durban) and in an invasive population recently (< 20 years) established in a cooler, more seasonal climate (Cape Town). After dissection, lean structural mass (bones and muscles), gonadal mass, liver mass and body fat percentage were measured in 161 native and invasive animals sampled at the beginning and the end of the breeding season. As expected, female gonadal mass decreased throughout the breeding season only in the invaded range. Thus, invasive female toads adopt a more marked capital breeding strategy than native conspecifics. Conversely, males from both populations appear to be income breeders. Also, male and female toads from the invaded range allocate more resources to growth than their native counterparts. Such a novel allocation strategy might be a response to the low temperatures, reduced rainfall and heightened seasonality encountered by the invasive population.

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