3,490 research outputs found

    Aquatic macroinvertebrate responses to native and non-native predators

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    Non-native species can profoundly affect native ecosystems through trophic interactions with native species. Native prey may respond differently to non-native versus native predators since they lack prior experience. Here we investigate antipredator responses of two common freshwater macroinvertebrates, Gammarus pulex and Potamopyrgus jenkinsi, to olfactory cues from three predators; sympatric native fish (Gasterosteus aculeatus), sympatric native crayfish (Austropotamobius pallipes), and novel invasive crayfish (Pacifastacus leniusculus). G. pulex responded differently to fish and crayfish; showing enhanced locomotion in response to fish, but a preference for the dark over the light in response to the crayfish. P. jenkinsi showed increased vertical migration in response to all three predator cues relative to controls. These different responses to fish and crayfish are hypothesised to reflect the predators’ differing predation types; benthic for crayfish and pelagic for fish. However, we found no difference in response to native versus invasive crayfish, indicating that prey naivetĂ© is unlikely to drive the impacts of invasive crayfish. The Predator Recognition Continuum Hypothesis proposes that benefits of generalisable predator recognition outweigh costs when predators are diverse. Generalised responses of prey as observed here will be adaptive in the presence of an invader, and may reduce novel predators’ potential impacts

    Differences in the escape response of a grapsid crab in the field and in the laboratory

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    Escape behaviours of prey animals are frequently used to study the neural control of behaviour. Escape responses are robust, fast, and can be reliably evoked under both field and laboratory conditions. Many escape responses are not as simple as previously suggested, however, and are often modulated by a range of contextual factors. To date it has been unclear to what extent behaviours studied in controlled laboratory experiments are actually representative of the behaviours that occur under more natural conditions. Here we have used the model species, Neohelice granulata, a grapsid crab, to show that there are significant differences between the crabs' escape responses in the field compared to those previously documented in laboratory experiments. These differences are consistent with contextual adjustments such as the availability of a refuge and have clear consequences for understanding the crabs' neural control of behaviour. Furthermore, the methodology used in this study mirrors the methodology previously used in fiddler crab research, allowing us to show that the previously documented differences in escape responses between these grapsid species are real and substantial. Neohelice's responses are delayed and more controlled. Overall, the results highlight the adaptability and flexibility of escape behaviours and provide further evidence that the neural control of behaviour needs to be address in both the laboratory and field context.Fil: Hemmi, J. M.. University of Western Australia; AustraliaFil: Tomsic, Daniel. Consejo Nacional de Investigaciones CientĂ­ficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Ciudad Universitaria. Instituto de FisiologĂ­a, BiologĂ­a Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de FisiologĂ­a, BiologĂ­a Molecular y Neurociencias; Argentin

    The maintenance, evolution, and impacts of inducible morphological defenses in Mytilus edulis: Responses to multiple and invasive predators

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    The burgeoning field of phenotypic plasticity and inducible defenses has documented a wide variety of predator-induced defenses. I this dissertation I have explored induced defenses in the marine mussel Mytilus edulis as they are affected by (a) shared evolutionary history with invasive crab predators, (b) specificity of responses to multiple predators (singly and combined) with different foraging strategies, and (c) spatial and temporal variation in the expression of predator specific induced defenses in situ. Mytilus from southern New England expressed induced shell thickening when exposed to waterborne cues from the crab Hemigrapsus , but naive northern mussel populations do not respond. Yet, both populations thicken their shells in response to a long-established crab, Carcinus. These results are consistent with the rapid evolution of an induced response to the recent invader Hemigrapsus. Mytilus developed significantly heavier shells only in the presence of waterborne cues from Carcinus, thicker shells in response to Carcinus, the seastar Asterias, and the whelk Nucella, and heavier adductor muscles in response to cues from Nucella and Asterias. These induced defenses subsequently protected mussels from Carcinus, but only Asterias exposed mussel were defended from Asterias. However, mussels exposed to the combined cues from Asterias and Carcinus expressed neither inducible defense nor deterred foraging by the sea star or crab. Furthermore, Mytilus did not thicken shells in response to cues from the native crab Cancer irroratus or the combined cues from Carcinus and Cancer, yet mussels did increase adductor muscle in response to combined cues from Asterias and Cancer. Thus, multiple predator assemblages can disrupt predator specific induced defenses (resulting in risk enhancement for mussels), but these effects cannot be reliably predicted from the predator\u27s functional grouping. Finally, in field experiments, I found that mussels expressed predator specific responses to Carcinus in mid-intertidal cages (but not Asterias) and mussels in low intertidal cages increased adductor muscle only in response to Asterias, and only during a year with high tissue growth. Together these results suggest that inducible defenses can be influenced by shared evolutionary history with predators and the functional diversity of predator assemblages

    Calanoid copepods: an overlooked tool in the control of disease vector mosquitoes

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    Biological control can assist in the management of disease vector mosquitoes. However, we urgently require the identification of novel and effective agents to aid population management strategies. Quantifying interactions strengths between consumers and resources is central to our understanding of trophic stability, and is relevant within the biological control context. Previously, pPredatory biocontrol of disease vector mosquito species has previously focused extensively on cyclopoid copepods, but prey size refuge effects have been identified as a hindrance to their predatory efficacy. Calanoid copepods have yet to be comprehensively examined in the context of mosquito control, despite their high prevalence, diversity and distribution. Here, we apply functional responses (FRs; resource use as a function of resource density) to examine interaction strengthspredation efficiencies of a recently described ephemeral pond specialist species, the freshwater calanoid copepod Lovenula raynerae SuĂĄrez-Morales, Wasserman & Dalu 2015, using different size classes of larvae of the disease vector complex Culex pipiens as prey. Lovenula raynerae effectively consumed C. pipiens larvae across their ontogeny. A potentially population destabilising Type II FR was exhibited towards both early and late instar mosquitoes, indicative of a lack of prey refuge across ontogenetic stages. Attack rates were greatest and handling times lowest for early instar larvae compared to late instar larvae. These traits contrast to other copepods, commonly applied in biocontrol, which are only able to handle early instars, and in much smaller numbers. We thus advocate that calanoid copepods can exert particularly marked predatory impact on lower trophic groups, and that their use in disease vector mosquito control strategies should be further explored

    Size of predatory mites and refuge entrance determine success of biological control of the coconut mite

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    Published online: 06 July 2016Predators face the challenge of accessing prey that live in sheltered habitats. The coconut mite Aceriaguerreronis Keifer (Acari: Eriophyidae) lives hidden beneath the perianth, which is appressed to the coconut fruit surface, where they feed on the meristematic tissue. Its natural enemy, the predatory mite Neoseiuluspaspalivorus De Leon (Acari: Phytoseiidae), is larger than this pest and is believed to gain access to the refuge only after its opening has increased with coconut fruit age. In the field, experimentally enlarging the perianth-rim-fruit distance beyond the size of the predators resulted in earlier predator occurrence beneath the perianth and lower numbers of coconut mites. On non-manipulated coconut fruits, the predators gained access to the prey weeks later than on manipulated ones, resulting in higher pest densities of coconut mites. Successful biological control thus critically hinges on the size of the predator relative to the opening of the prey refuge

    When is general wariness favored in avoiding multiple predator types?

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    Free access to article and electronic appendices via DOI.Adaptive responses to predation are generally studied assuming only one predator type exists, but most prey species are depredated by multiple types. When multiple types occur, the optimal antipredator response level may be determined solely by the probability of attack by the relevant predator: "specific responsiveness." Conversely, an increase in the probability of attack by one predator type might increase responsiveness to an alternative predator type: "general wariness." We formulate a mathematical model in which a prey animal perceives a cue providing information on the probability of two predator types being present. It can perform one of two evasive behaviors that vary in their suitability as a response to the "wrong" predator type. We show that general wariness is optimal when incorrect behavioral decisions have differential fitness costs. Counterintuitively, difficulty in discriminating between predator types does not favor general wariness. We predict that where responses to predator types are mutually exclusive (e.g., referential alarm-calling), specific responsiveness will occur; we suggest that prey generalize their defensive responses based on cue similarity due to an assumption of response utility; and we predict, with relevance to conservation, that habituation to human disturbance should generalize only to predators that elicit the same antipredator response as humans

    A temporal refuge from predation can change the outcome of prey species competition

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    Funding Information: – AS was supported by The Maxwell Institute Graduate School in Analysis and its Applications, a Centre for Doctoral Training funded by the UK Engineering and Physical Sciences Research Council (grant EP/L016508/01), the Scottish Funding Council, Heriot‐Watt University and the University of Edinburgh. Publisher Copyright: © 2022 The Authors. Oikos published by John Wiley & Sons Ltd on behalf of Nordic Society Oikos.Peer reviewedPublisher PD

    Lindude pÔgenemiskÀitumine erineva kisklusriskiga olukordades: terviklikum kÀsitlus

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    VĂ€itekirja elektrooniline versioon ei sisalda publikatsiooneSuurema hirmutunde korral panustavad loomad enam aega valvsusele ja ohtu silmates pĂ”genevad varem. Inimene vĂ”ib oma tegevustega tahtmatult loomade hirmutunnet suurendada, pĂ”hjustades halbu kĂ€itumisotsuseid ja populatsiooni arvukuse langust. Loomade hirmutunde hindamiseks mÔÔdetakse enamasti kas nende valvsust vĂ”i pĂ”genemiskaugust. Doktoritöös uuriti, kas ĂŒheainsa kĂ€itumispĂ”hise indikaatori mÔÔtmisest siiski piisab, et lindude hirmutunnet ja pĂ”genemisega seotud kulutusi veenvalt hinnata. Lisaks selgitati, kas linnud jĂ€tkavad kiskja jĂ€lgimist veel ka pĂ”genemise ajal ja milliseid lisategureid tuleks pĂ”genemiskĂ€itumise uurimisel arvesse vĂ”tta. Doktoritöö raames uuriti standardiseeritud viisil kĂŒmnete linnuliikide pĂ”genemiskĂ€itumist mitmel pool ĂŒle Euroopa, et tuvastada ĂŒldisi trende lindude kĂ€itumismustrites. PĂ”genemiskĂ€itumise poolest olid linnalinnud mitmes mĂ”ttes julgemad kui maalinnud ning laiuskraadi kasvades muutusid linnud vĂ€hem ettevaatlikuks. Üllatuslikult olid linnalinnud valvsamad kui maalinnud ning vastupidiselt varem eeldatule viivitasid valvsamad linnud mĂ”lemas elupaigas pĂ”genemisega kauem. Need tulemused seavad valvsuse tavapĂ€rase kasutatavuse lindude hirmutunde kirjeldamiseks kahtluse alla. Tööst ilmnes veel, et lisaks enamasti uuritavale pĂ”genemiskaugusele tuleks mÔÔta ka pĂ”genemishetkele jĂ€rgnevaid kĂ€itumismustreid. Need tĂ€iendavad mÔÔtmised annavad terviklikuma ĂŒlevaate pĂ”genemisega seotud ajalistest ja energeetilistest kulutustest, mis omakorda aitab kaasa pĂ”genemisotsuste mĂ”istmisele. NĂ€iteks leiti, et pĂ”genemisele kulutatud aeg sĂ”ltub hirmutunde dĂŒnaamikast pĂ”genemise ajal. See on esimene eksperimentaalne tĂ”end, et linnud jĂ€tkavad kiskja jĂ€lgimist ka pĂ€rast pĂ”genemise alustamist. Doktoritöö tulemused toetasid ka varasemaid uuringuid, mis on leidnud, et pĂ”genemisotsuseid mĂ”jutavad ka nĂ€iteks liigiomane kehamass, peidupaiga lĂ€hedus ja seltsingu suurus. Doktoritööst saadud teadmised aitavad paremini ennustada, kuidas lindude hirmutunne vĂ”ib inimtekkeliste hĂ€iringutega seoses muutuda, mis omakorda aitab kaasa looduskaitseliste meetmete planeerimisele.Animals with higher levels of fearfulness will spend more time being vigilant and will escape earlier after having spotted a potential threat. Human-caused disturbances can involuntarily increase fearfulness in animals, which can result in inaccurate behavioural decisions that can lead to population declines. The most common measures of fearfulness in animals are vigilance and flight initiation distance. Present thesis examined whether the use of a single behavioural indicator is enough to assess fearfulness and costs related to escape. The thesis also investigated whether birds continue to monitor predators during escape, and which other factors should be considered when studying escape behaviour. Tens of bird species were studied across Europe in a standardized way to find general patterns in the behaviour of birds. Urban birds were characterized by a more relaxed escape behaviour than rural birds. In addition, birds took longer to become alert to threats as latitude increased. Surprisingly, urban birds were more vigilant than rural birds, and, contrary to the prevalent theory, vigilant birds delayed escape more. These results raise doubt whether vigilance should be used as an indicator of fearfulness in birds. The thesis also highlighted that in addition to measuring flight initiation distance, it is important to measure subsequent behavioural decisions. Doing so provides a more complete view of the energetic and opportunity costs of escape, which helps to understand escape-related decisions. For example, it was found that escape duration depends on how the perceived risk of predation changes while fleeing. That is the first experimental evidence that birds continue to monitor predators after initiating escape. Last, the evidence from the thesis complements previous research that, for example, has found body mass, distance to refuge, and group size to influence escape decisions in animals. The knowledge gained from the thesis improves predictions about the impact of human-caused disturbances on fearfulness in birds, which in turn benefits decision making in wildlife management.https://www.ester.ee/record=b529839
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