A review of mammal eradications on Mediterranean islands

1. Impacts of alien invasive species on island communities and ecosystems may be even more detrimental than on the mainland. Therefore, since the 1950s, hundreds of restoration projects have been implemented worldwide, with the aim of controlling or eradicating alien species from islands. To date, no review has been focused on eradication on Mediterranean islands. To fill the gap, I reviewed the available information concerning mammal eradications so far carried out on Mediterranean islands, examining the details of several aspects of project implementation and monitoring.
2. I obtained data for 139 attempted eradications on 107 Mediterranean islands in eight countries, with Greece, Italy, and Spain accounting for the highest number. Eradication projects targeted 13 mammal species. The black rat Rattus rattus was the target of over 75% of the known attempted eradications in the Mediterranean Basin; other species targeted were feral goat Capra hircus, house mouse Mus musculus, European rabbit Oryctolagus cuniculus, and domestic cat Felis catus. The most widely adopted technique was poisoning (77% of all eradications), followed by trapping (15%) and hunting (4%). However, techniques were largely target-specific.
3. The average failure rate was about 11%. However, this percentage varied according to the specific mammalian order, and eradications of Carnivora failed more often than those of other mammals. Among rodents, house mouse eradication attained a very high failure rate (75%). Reinvasion occurred after 15% of successful eradications.
4. A better understanding of the motivations of animal rights activists may improve the chance of success when eradicating charismatic or domesticated species. Furthermore, it is crucial to collect data and case studies about reinvasions, in order to strengthen biosecurity programmes following eradication. As in other parts of the world, the next frontier in alien mammal management on Mediterranean islands concerns the eradication of invasive species from inhabited islands.

     

Predation and avoidance behaviour in aphid‐ladybird interactions of native and invasive ladybirds in Europe

1. While detrimental effects of invasive predators on native species are well documented, we often lack a mechanistic understanding of the invasion success. Lack of prey avoidance behaviour can lead to higher consumption rates by invasive predators compared to native predators. This competitive advantage is expected to contribute to the invasion success of non‐native predators.
2. We compared aphid consumption and cue avoidance behaviour of aphids between four native ladybird species (Coccinella septempunctata, Adalia bipunctata, Propylea quatuordecimpunctata, and Hippodamia variegata) and the invasive Asian ladybird Harmonia axyridis.
3. The invasive H. axyridis and the native C. septempunctata consumed more aphids than the three smaller native ladybird species. In line with our expectations, aphids avoided leaves bearing cues of most native ladybird species but not of the invasive H. axyridis.
4. Our results indicate that body size rather than ladybird origin determined aphid predation rates. The lack of aphid avoidance behaviour towards cues of H. axyridis indicates that they were not able to recognise the chemical cues of the invasive predator.
5. Relatively large body size and the absence of cue avoidance in aphids might benefit the invasive H. axyridis, particularly in comparison to smaller native ladybird species. The absence of avoidance behaviour in aphids might lead to even higher predation rates of H. axyridis under more natural conditions.

     

Small mammals on Massachusetts islands: the use of probability functions in clarifying biogeographic relationships

Summary Thirty-three insular small mammal communities along the coast of Massachusetts (USA) were surveyed to investigate the biogeographic relationships of the insular communities and to examine the distribution patterns of individual species. Nine species of terrestrial small mammals were observed in the total insular fauna, whereas thirteen occurred on the mainland. The species-area relation yielded a z value of 0.06, which is the lowest value yet reported for insular mammal communities.Multiple logistic regression was used to calculate probability functions for each species in order to identify variables potentially important in determining a species' occurrence on islands and to estimate probabilities of occurrence on islands. Statistically significant and ecologically interpretable functions were obtained for all but one species. Occurrence on islands was positively related to increasing island size in four species and to decreasing island isolation in four species. The extremely low z value, negative correlations of species number with isolation variables, and the inclusion of an isolation variable in the logistic functions of four species indicated that immigration was an important determinant of small mammal occurrence on these islands. There was a positive relationship between population density and number of islands occupied.Logistic regression has several advantages over linear discriminant function analysis, and we suggest that it may be useful in other ecological studies and in the preservation of endangered species.     

The role of exotic mammals in the diet of native carnivores from South America

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Overcoming urban stream syndrome: Trophic flexibility confers resilience in a Hawaiian stream fish

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The threat of invasive species to bats: a review

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Introduced cats Felis catus eating a continental fauna: inventory and traits of Australian mammal species killed

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Comparative isotopic natural history of two native passerines (Troglodytes cobbi and Cinclodes antarcticus) and the invasive rats (Rattus norvegicus) that extirpate them

While several studies have shown that invasive rats can have negative effects on island birds through predation (both direct predation and nest predation), other mechanisms for the effects of invasives on island biota have been given less attention. Here, we explore another potential mechanism by which invasive rats can affect native island birds: the competitive use of common resources. We used stable isotope analyses to estimate the fraction of marine and terrestrial sources incorporated into the tissues of two species of passerines (Troglodytes cobbi, Troglodytidae; and Cinclodes antarcticus, Furnariidae) and Norway rats (Rattus norvegicus, Muridae) in the Falkland Islands. These two passerines are absent on islands where rats are present. We found significant incorporation of marine resources in the three species, with the highest incorporation in tissues of T. cobbi. This species appears to be one of the passerines most reliant on marine sources and the most marine member of the family Troglodytidae. We also used the results of these isotopic analyses to estimate the isotopic niche breadth of each of these species and the isotopic niche overlap among them. Rattus norvegicus had a large isotopic niche that overlapped broadly with those of the two passerine species. We propose that different ways of both depicting and estimating isotopic niche widths are complementary rather than alternative. Our results are consistent with the notion that invasive rats might have an impact on these two species of Falkland Island passerines by using common resources but do not rule out the possibility that part of their effect is through direct predation.     

Cypriniform fish in running waters reduce hyporheic oxygen depletion in a eutrophic river

1. The hyporheic zone is an important habitat for benthic invertebrates and early-developmental stages of gravel spawning fish. However, the eutrophication of running waters and, in turn, the excessive periphyton biomass leads to its biological clogging. The result of these processes is oxygen depletion and a reduction in the habitat quality of the hyporheic zone.
2. This study assessed whether top-down effects of two important European river fish species, the large herbivorous cypriniform common nase (Chondrostoma nasus, L.) and the large omnivorous cypriniform European chub (Squalius cephalus, L.), can reduce eutrophication effects in the hyporheic zone. A 4-week mesocosm-based field experiment in a eutrophic river was conducted using cage enclosures stocked or not with either nase or chub.
3. The top-down control of periphyton was expected to reduce biological clogging and thereby increase oxygen availability in the hyporheic zone. Accordingly, we hypothesised that in enclosures stocked with either fish the concentrations of dissolved oxygen in the hyporheic zone would be higher and the periphyton biomass would be lower than in enclosures without fish stocking.
4. Hyporheic oxygen concentrations were significantly higher in enclosures stocked with either nase or chub than in enclosures without fish stocking. However, periphyton ash-free dry mass was significantly reduced only in enclosures stocked with nase, not in those stocked with chub. Thus, the positive effects of nase and chub on hyporheic oxygen availability were caused by different mechanisms.
5. Our results demonstrate that nase and chub can reduce eutrophication effects in the hyporheic zone of running waters. Hence, protecting and enhancing stocks of herbivorous and omnivorous fish will contribute to restoring the hyporheic zone in efforts to preserve biodiversity in eutrophic rivers.

     

Predicting the ecological impacts of a new freshwater invader: functional responses and prey selectivity of the ‘killer shrimp’, Dikerogammarus villosus,compared to the native Gammarus pulex

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Invasiveness of plants is predicted by size and fecundity in the native range

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Factors determining mammal species richness on habitat islands and isolates: habitat diversity, disturbance, species interactions and guild assembly rules

• 1 For over three decades the equilibrium theory of island biogeography has galvanized studies in ecological biogeography. Studies of oceanic islands and of natural habitat islands share some similarities to continental studies, particularly in developed regions where habitat fragmentation results from many land uses. Increasingly, remnant habitat is in the form of isolates created by the clearing and destruction of natural areas. Future evolution of a theory to predict patterns of species abundance may well come from the application of island biogeography to habitat fragments or isolates.
• 2 In this paper we consider four factors other than area and isolation that influence the number and type of mammal species coexisting in one place: habitat diversity, habitat disturbance, species interactions and guild assembly rules. In all examples our data derive from mainland habitat, fragmented to differing degrees, with different levels of isolation.
• 3 Habitat diversity is seen to be a good predictor of species richness. Increased levels of disturbance produce a relatively greater decrease in species richness on smaller than on larger isolates. Species interactions in the recolonization of highly disturbed sites, such as regenerating mined sites, is analogous to island colonization. Species replacement sequences in secondary successions indicate not just how many, but which species are included. Lastly, the complement of species established on islands, or in insular habitats, may be governed by guild assembly rules. These contributions may assist in taking a renewed theory into the new millennium.

     

Characterization of eight polymorphic microsatellites in the shrew Crocidura suaveolens and its application to the study of insular populations of the French Atlantic coast

We developed eight polymorphic microsatellite loci to study the natural populations of Crocidura suaveolens, the lesser white‐toothed shrew. These loci are used in the study of insular populations of the French Atlantic coast where these shrews exhibit gigantism features that suggest an insular syndrome. These populations were threatened by the invasion of the rat Rattus norvegicus and the eradication of this alien pest in some islands was followed by a demographic expansion of the shrew populations. These first genetic results suggest that the shrew populations in the three studied islands are very differentiated.     

An invasive species may be better than none: invasive signal and native noble crayfish have similar community effects

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Temporal and palaeoclimatic context of the evolution of insular woodiness in the Canary Islands

Insular woodiness (IW), referring to the evolutionary transition from herbaceousness toward woodiness on islands, has arisen more than 30 times on the Canary Islands (Atlantic Ocean). One of the IW hypotheses suggests that drought has been a major driver of wood formation, but we do not know in which palaeoclimatic conditions the insular woody lineages originated. Therefore, we provided an updated review on the presence of IW on the Canaries, reviewed the palaeoclimate, and estimated the timing of origin of woodiness of 24 insular woody lineages that represent a large majority of the insular woody species diversity on the Canaries. Our single, broad‐scale dating analysis shows that woodiness in 60%–65% of the insular woody lineages studied originated within the last 3.2 Myr, during which Mediterranean seasonality (yearly summer droughts) became established on the Canaries. Consequently, our results are consistent with palaeoclimatic aridification as a potential driver of woodiness in a considerable proportion of the insular woody Canary Island lineages. However, the observed pattern between insular woodiness and palaeodrought during the last couple of million years could potentially have emerged as a result of the typically young age of the native insular flora, characterized by a high turnover.     

Not all predators are equal: a continent‐scale analysis of the effects of predator control on Australian mammals

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Evolutionary history predicts high‐impact invasions by herbivorous insects

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Design features of constructed floodplain ponds influence waterbird and fish communities in northern New Zealand

1. Ponds can provide important refuges for aquatic biota on developed floodplains and are increasingly being constructed in an effort to enhance native biodiversity and ecosystem services in degraded landscapes. This study examined 34 constructed ponds to investigate the influence of design features on community composition, native biodiversity, and the biomass or abundance of common fish and waterbirds on the lower Waikato River floodplain, northern New Zealand.
2. Inundation frequency appeared to be a key factor affecting biomass of the native shortfin eel Anguilla australis and three invasive fish species (common carp [Cyprinus carpio], brown bullhead [Ameiurus nebulosus], and goldfish [Carassius auratus]), suggesting that colonisation occurred during flooding by adjacent waterbodies. Linear models indicated that shortfin eel abundance and total eel biomass were positively associated with the biomass of potential fish prey, the area occupied by islands and cover by trees in the riparian zone.
3. Native waterbird species richness was strongly related to water area, edge length (including islands) and area:perimeter ratio, with little increase in richness for ponds >1 ha in area, perimeters longer than 800 m, and ratios over 20. The protected grey teal (Anas gracilis), and the recreationally hunted species phenotypically assigned as mallard (Anas platyrhynchos + hybrids) and grey duck (Anas superciliosa + hybrids) appeared most strongly influenced, respectively, by perimeter length, water depth, and biomass of potential macroinvertebrate food supplies, suggesting variable effects of pond design attributes among waterfowl species.
4. Overall, these results indicate that constructed ponds can be designed to promote native waterbird diversity, enhance eel fishery and waterfowl gamebird services, and also limit the proliferation of some non-native invasive fish species in degraded floodplain landscapes. A hierarchy of constructed pond design attributes was identified, involving landscape position and connectivity, pond morphology and complexity, and riparian maturity and buffering, which were associated with direct (habitat) and indirect (food supply, physicochemistry) effects on biodiversity and provisioning services.

     

Between‐lake variation in the trophic ecology of an invasive crayfish

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