Does differential predation permit invasive and native mosquito larvae to coexist in Florida?

Abstract.  1. The hypothesis that selective predation on larvae of the invasive Aedes albopictus (Skuse) could account for its stable coexistence with the native mosquito species and inferior competitor Ochlerotatus triseriatus (Say) in Florida treeholes and container systems was tested experimentally.
2. Functional responses of the two dipteran predators Toxorhynchites rutilus (Coquillett) and Corethrella appendiculata (Grabham) were evaluated separately for A. albopictus and O. triseriatus prey. Both predators exhibited type II functional responses and consistently consumed more of the invasive species. Handling time of T. rutilus feeding upon O. triseriatus was significantly longer than when preying upon the invasive species.
3. When either predator species was offered varying ratios of the two prey species, A. albopictus was consumed preferentially. The absence of a prey ratio effect on preference indicated that switching probably does not occur.
4. The higher maximum feeding rate upon, and preference for, A. albopictus suggests that differential predation may foster coexistence of the invasive and native mosquito prey species in Florida.     

Transient dynamics limit the effectiveness of keystone predation in bringing about coexistence

We analyze the transient dynamics of simple models of keystone predation, in which a predator preferentially consumes the dominant of two (or more) competing prey species. We show that coexistence is unlikely in many systems characterized both by successful invasion of either prey species into the food web that lacks it and by a stable equilibrium with high densities of all species. Invasion of the predator-resistant consumer species often causes the resident, more vulnerable prey to crash to such low densities that extinction would occur for many realistic population sizes. Subsequent transient cycles may entail very low densities of the predator or of the initially successful invader, which may also preclude coexistence of finite populations. Factors causing particularly low minimum densities during the transient cycles include biotic limiting resources for the prey, limited resource partitioning between the prey, a highly efficient predator with relatively slow dynamics, and a vulnerable prey whose population dynamics are rapid relative to the less vulnerable prey. Under these conditions, coexistence of competing prey via keystone predation often requires that the prey's competitive or antipredator characteristics fall within very narrow ranges. Similar transient crashes are likely to occur in other food webs and food web models.     

High reproductive rates result in high predation risks: a mechanism promoting the coexistence of competing prey in spatially structured populations

I tested the hypothesis that spatial structure provides a trade-off between reproduction and predation risk and thereby facilitates predator-mediated coexistence of competing prey species. I compared a cellular automata model to a mean-field model of two prey species and their common predator. In the mean-field model, the prey species with the higher reproductive rate (the superior competitor) always outcompeted the other species (the inferior competitor), both in the presence of and the absence of the predator. In the cellular automata model, both prey species, which differed only in their reproductive rates, coexisted for a long time in the presence of their common predator at intermediate levels of predation. At low predation rates, the superior competitor dominated, while high predation rates favored the inferior competitor. This discrepancy in the results of the different models was due to a trade-off that spontaneously emerged in spatially structured populations; that is, the more clustered distribution of the superior competitor made it more susceptible to predation. In addition, coexistence of competing prey species declined with increasing dispersal ranges of either prey or predator, which suggests that the trade-off that results from spatial structure becomes less important as either prey or predator disperse over a broader range.     

Stage-dependent predation on competitors: consequences for the outcome of a mosquito invasion

1. Predator-mediated coexistence occurs when predation allows competitors to coexist, due to preferential consumption of a superior competitor relative to an inferior competitor. Differences between the native treehole mosquito ( Aedes triseriatus ) and the co-occurring Asian tiger mosquito ( Aedes albopictus ) in anti-predatory larval behaviours account, in part, for the greater vulnerability of this invasive species to native predatory midge ( Corethrella appendiculata ). We test the hypothesis that stage-dependent differences in the sizes of A. albopictus and A. triseriatus larvae, relative to the size-limited C. appendiculata , contribute to differential consumption and the likelihood of predator-mediated coexistence of these competitors.
2. In all instars, larvae of A. triseriatus were larger than A. albopictus of the same stage. Third and fourth instar C. appendiculata selectively consumed late-stage A. albopictus in preference to same-stage A. triseriatus . Small, early-stage prey larvae did not differ in vulnerability to predation, but large, late-stage larvae differed significantly in vulnerability to predation, probably owing to size-limited predation by fourth instar C. appendiculata. This effect was less pronounced for third instar C. appendiculata .
3. Prey size, in conjunction with anti-predatory behavioural responses, alters the probability of predator-mediated coexistence. A stage-structured predation model showed that equally vulnerable early stages reduce the range of environmental conditions (productivities) in which predator-mediated coexistence is possible, increasing the likelihood of both competitive exclusion of the resident species or failure of the invasive to establish. These results underscore the importance of stage-dependent interspecific differences in predator–prey interactions for determining how predators may affect community composition.     

Behavioural responses of larval container mosquitoes to a size-selective predator

Abstract.  1. The hypothesis that size-selective predation and species-specific prey behaviours facilitate the coexistence between larvae of invasive Aedes albopictus (Skuse) and U.S.A.-native Ochlerotatus triseriatus (Say) was tested experimentally with the predator Corethrella appendiculata (Grabham).
2. Larval behaviours associated with a higher risk of predation were identified, and prey behavioural responses were tested in either the physical presence of predators or in water containing predation cues. Larvae that thrashed on container bottoms had a higher risk of being captured by fourth instar C. appendiculata than did larvae resting on the water surface. Ochlerotatus triseriatus , but not A. albopictus , adopted low-risk behaviours in response to water-borne cues to predation. Both prey species reduced risky behaviours in the physical presence of the predator, but O. triseriatus showed a stronger response.
3. The vulnerability of 2nd and 3rd instar prey to predation was compared, and behavioural responses were correlated with prey vulnerability. Second instars of both species were more vulnerable to predation by C. appendiculata than were 3rd instars, and the 3rd instar A. albopictus was more vulnerable than O. triseriatus of the same stage. All instars of O. triseriatus showed a similar reduction of risky behaviours in response to the presence of C. appendiculata despite 4th instar prey being relatively invulnerable to size-selective predation.
4. Weaker predator avoidance, coupled with superior competitive ability, of invasive A. albopictus is likely to contribute to its coexistence with O. triseriatus in containers of the south-eastern U.S.A., where C. appendiculata can be abundant.     

The significance of ratios of detritus types and micro-organism productivity to competitive interactions between aquatic insect detritivores

Investigations of competitive interactions emphasize non-detrital resources, even though detritus is a major component of most food webs. Studies of competing species focus usually on single resource types, although consumers in nature are likely to encounter mixtures of resource types that may affect whether competition results in exclusion or coexistence. The invasive mosquito Aedes albopictus is capable of excluding the native mosquito Ochlerotatus triseriatus in competition for single detritus types in laboratory and field microcosms. In this study, we used nine ratios of two detritus types (animal and leaf) common in natural containers to test whether detritus ratios affect the outcome of competition. Under intraspecific and interspecific competition, A. albopictus attained higher survival and estimated population growth rate than did O. triseriatus. Unlike past studies, both species had positive growth and high adult survival, with little evidence of competitive effects, under one resource ratio (10:1 ratio of leaf : animal detritus) regardless of mosquito densities, suggesting potential coexistence. Path analysis showed that densities of larvae had negative effects on population growth for O. triseriatus but not for A. albopictus, indicating competitive superiority of A. albopictus. Population growth of both species was affected strongly by the direct paths from animal (positive) and leaf (negative) detritus, and the indirect effect of leaf detritus via bacterial production (positive). Field sampling established that detritus entered real tree holes in ratios similar to those in our experiment, suggesting that natural variation in detritus ratios may influence local coexistence of these species. Seasonal variation in ratios of plant and animal detritus indicated that temporal as well as spatial variation in inputs may be important for potential coexistence.     

Interactive effects of productivity and predation on zooplankton diversity

Recent studies suggest the necessity of understanding the interactive effects of predation and productivity on species coexistence and prey diversity. Models predict that coexistence of prey species with different competitive abilities can be achieved if inferior resource competitors are less susceptible to predation and if productivity and/or predation pressure are at intermediate levels. Hence, predator effects on prey diversity are predicted to be highly context dependent: enhancing diversity from low to intermediate levels of productivity or predation and reducing diversity of prey at high levels of productivity or predation. While several studies have examined the interactive effects of herbivory and productivity on primary producer diversity, experimental studies of such effects in predator‐prey systems are rare. We tested these predictions using an aquatic field mesocosm experiment in which initial density of the zooplankton predator Notonecta undulata and productivity were manipulated to test their interactive effects on diversity of seven zooplankton, cladoceran species that were common in surrounding ponds. Two productivity levels were imposed via phosphorus enrichment at levels comparable to low and intermediate levels found within neighboring natural ponds. We used open systems to allow for natural dispersal and behaviorally‐mediated numerical responses by the flight‐capable predator. Effects of predators on zooplankton diversity depended on productivity level. At low and high productivity, prey species richness declined while at high productivity it showed a unimodal relationship with increasing the predator density. Effects of treatments were weaker when using Pielou's evenness index or the inverse Simpson index as measures of prey diversity. Our findings are generally consistent with model predictions in which predators can facilitate prey coexistence and diversity at intermediate levels of productivity and predation intensity. Our work also shows that the functional form of the relationship between prey diversity and predation intensity can be complex and highly dependent on environmental context.     

Better to Be in Bad Company than to Be Alone? Aedes Vectors Respond Differently to Breeding Site Quality in the Presence of Others

This study focuses on two competing species, Aedes aegypti and Aedes albopictus (Diptera: Culicidae), both invasive mosquitoes of the New World. Context-specific competition between immature forms inside containers seems to be an important determinant of the coexistence or displacement of each species in different regions of the world. Here, competition experiments developed at low density (one, two or three larvae) and receiving four different resource food concentration, were designed to test whether Ae. albopictus and Ae. aegypti respond differently to competition, and whether competition can be attributed to a simple division of resources. Three phenotypic traits - larval development, adult survival under starvation and wing length - were used as indicators of performance. Larvae of neither species were limited by resource concentration when they were alone, unlike when they developed with competitors. The presence of conspecifics affected Ae. aegypti and Ae. albopictus, inducing slower development, reduced survival and wing length. The response to resource limitation was different when developing with heterospecifics: Ae. aegypti developing with one heterospecific showed faster development, producing smaller adults with shorter lives, while in the presence of two competitors, development increased and adults lived longer. Aedes albopictus demonstrated a better performance when developing with heterospecifics, with no loss in their development period and improved adult survival. Overall, our results suggest that response to competition can not simply be attributed to the division of resources, and that larvae of both species presented large phenotypic plasticity in their response to the presence or absence of heterospecifics and conspecifics.     

Environmental variation and the predator-specific responses of tropical stream insects: effects of temperature and predation on survival and development of Australian Chironomidae (Diptera)

The threat posed by predation varies among predator species and with environmental context, and prey species often adjust their responses accordingly. We investigated such effects within an insect assemblage from a tropical Australian stream. These systems are frequently subjected to catastrophic floods, often suggested to reduce the importance of predation in streams, and invertebrate faunas are characterised by relatively broad environmental tolerances. Impacts of the hunting predator Australopelopia prionoptera (Diptera: Chironomidae) and an undescribed ambush predator from the Polycentropodidae (Trichoptera) on survival and development of two species of tubicolous Chironomidae, Echinocladius martini (Orthocladiinae) and Polypedilum australotropicus (Chironominae), were assessed in laboratory microcosms. A further experiment investigated how impacts of Australopelopia varied over a broad range of temperatures, exceeding that experienced annually by the studied populations. Neither predator impacted survivorship for E. martini, but the presence of the polycentropodid caused E. martini to spend longer as larvae and reduced adult longevity, and adult females were smaller-sized and had smaller oocytes. In contrast, both predators reduced survivorship of P. australotropicus, but only Australopelopia affected its development, causing reductions in pupal duration and oocyte size. The observed non-lethal impacts of predation reflect the threat each predator is known to pose to each prey species in situ. Impacts of predation varied little with temperature, reflecting the broad thermal tolerances of all study species. The predator-specific responses of the prey species imply that predation is a significant selective force in tropical Australian streams, although fluctuation in intensity of predation associated with flooding may limit its importance for community structure and prey diversity at larger scales. Our results indicate a more limited scope for environmental modification of predator–prey relationships in faunas characterised by broad physiological tolerances.     

High food quality of prey lowers its risk of extinction

The mineral and biochemical food quality of prey may limit predator production. This well‐studied direct bottom–up effect is especially prominent for herbivore–plant interactions. Low‐quality prey species, particularly when defended, are generally considered to be less prone to predator‐driven extinction. Undefended high‐quality prey species sustain high predator production thereby potentially increasing their own extinction risk. The food quality of primary producers is highly species‐specific. In communities of competing prey species, predators thus may supplement their diets of low‐quality prey with high‐quality prey, leading to indirect horizontal interactions between prey species of different food quality. We explore how these predator‐mediated indirect interactions affect species coexistence in a general predator–prey model that is parametrized for an experimental algae– rotifer system. To cover a broad range of three essential functional traits that shape many plant–herbivore interactions we consider differences in 1) the food quality of the prey species, 2) their competitive ability for nutrient uptake and 3) their defence against predation. As expected, low food quality of prey can, similarly to defence, provide protection against extinction by predation. Counterintuitively, our simulations demonstrate that being of high food quality also prevents extinction of that prey species and additionally promotes coexistence with a competing, low‐quality prey. The persistence of the high‐quality prey enables a high conversion efficiency and control of the low‐quality prey by the predator and allows for re‐allocation of nutrients to the high‐quality competitor. Our results show that high food quality is not necessarily detrimental for a prey species but instead can protect against extinction and promote species richness and functional biodiversity.     

Not attackable or not crackable—How pre‐ and post‐attack defenses with different competition costs affect prey coexistence and population dynamics

It is well‐known that prey species often face trade‐offs between defense against predation and competitiveness, enabling predator‐mediated coexistence. However, we lack an understanding of how the large variety of different defense traits with different competition costs affects coexistence and population dynamics. Our study focusses on two general defense mechanisms, that is, pre‐attack (e.g., camouflage) and post‐attack defenses (e.g., weaponry) that act at different phases of the predator—prey interaction. We consider a food web model with one predator, two prey types and one resource. One prey type is undefended, while the other one is pre‐ or post‐attack defended paying costs either by a higher half‐saturation constant for resource uptake or a lower maximum growth rate. We show that post‐attack defenses promote prey coexistence and stabilize the population dynamics more strongly than pre‐attack defenses by interfering with the predator's functional response: Because the predator spends time handling “noncrackable” prey, the undefended prey is indirectly facilitated. A high half‐saturation constant as defense costs promotes coexistence more and stabilizes the dynamics less than a low maximum growth rate. The former imposes high costs at low resource concentrations but allows for temporally high growth rates at predator‐induced resource peaks preventing the extinction of the defended prey. We evaluate the effects of the different defense mechanisms and costs on coexistence under different enrichment levels in order to vary the importance of bottom‐up and top‐down control of the prey community.     

Evolutionary Consequences of Predation for Pathogens in Prey

This article investigates the impact of predation on the coexistence and competitive exclusion of pathogen strains in the prey. Two types of predator are considered—a generalist and a specialist. For each type of predator, we assume that the predator can discriminate among susceptible and infected with each strain prey. The two strains will competitively exclude each other in the absence of predation with the strain with the larger reproduction number persisting. If a generalist predator preys discriminantly and the disease is fatal, then depending on the predation level, a switch in the dominant pathogen may occur. Thus, for some predation levels, the first strain may persist while for other predation levels the second strain may persist. Furthermore, a specialist predator preying discriminantly may mediate the coexistence of the two strains. Although in most cases increasing predation reduces the disease load in the prey, when predation leads to coexistence, it may also lead to increase in the disease load.     

The dynamics of predation and competition in patchy environments

The model of N. D. Atkinson and B. Shorrocks (J. Anim. Ecol. 50, 461–471 (1981)) as two competing species distributing their progeny amongst patches according to independent negative binomial distributions. The resulting separation of the species increases the likelihood of coexistence. We have assumed a much simpler distribution of the competitors which has enabled us to explore analytically the dynamics of interactions with two competing species and a shared natural enemy in a patchy environment. Two types of natural enemy have been considered: a generalist predator whose dynamics are uncoupled from those of the two prey species, and a specialist (e.g., a parasitoid) whose dynamics are entirely coupled to those of its two prey. The following conclusions emerge. Non-aggregating generalist predators causing random predation across patches are generally destabilizing (although asymmetrical predation may in some case enhance coexistence as a result of preferential predation on the superior competitor). Predator aggregation in patches of high prey density, however, produces a switching effect which tends to promote stability. Coexistence is now even possible with high degrees of correlation in the distribution of the two prey and in situations of extreme competition where the competition coefficients exceed one. The main difference in the models with a specialist parasitoid as the natural enemy is a reduction in stability compared with the equivalent generalist-prey interaction. But stable coexistence can still readily occur if the natural enemies aggregate markedly in patches of high prey density.     

Predation rate, prey preference and predator switching: experiments on voles and weasels

We studied the predation rate and prey selection of the least weasel ( Mustela nivalis nivalis ) on its two most common prey species in boreal environments, the bank vole ( Clethrionomys glareolus ) and the field vole ( Microtus agrestis ), in large outdoor enclosures. We also studied the response of weasels to odours of the two species in the laboratory. The enclosure experiment was conducted using constant vole densities (16 voles/ha) but with varying relative abundance of the two species. Weasels showed higher predation rates on bank voles, and males had higher predation rate than females. Females killed disproportionately more of the more abundant prey species, but they preferred bank voles to field voles when both were equally available. Overall, the predation rate also increased with increasing abundance of bank voles. Therefore our results are in agreement with earlier laboratory results showing preference for bank voles, even if no intrinsic preference for odours of either species was observed in our laboratory study. We suggest that the least weasel hunts according to prey availability, prey aggregation and suitability of hunting habitat, and that this causes the observed dependence of least weasels on field voles and emphasises the role of the field vole in the vole-weasel interaction in cyclic vole populations. Furthermore, our results suggest that predation by weasels may facilitate the coexistence of the two vole species via predator switching, and that it may cause the observed synchrony in dynamics between vole species.     

The effects of seafloor habitat complexity on survival of juvenile fishes: Species-specific interactions with structural refuge

Marine fishes are often associated with structurally complex microhabitats that are believed to provide a refuge from predation. However, the effects of habitat complexity on predator foraging success can be strongly modified by predator and prey behaviors. We conducted a series of laboratory experiments to evaluate the effects of sea floor habitat complexity on juvenile fish survivorship using multiple predator (striped searobin and summer flounder) and prey (winter flounder, scup, and black sea bass) species to identify potentially important species-habitat interactions. Three habitats of varying complexity (bare sand, shell, and sponge) common to coastal marine environments were simulated in large aquaria (2.4 m diameter, 2400 L volume). Prey survivorship increased significantly with greater habitat complexity for each species combination tested. However, examination of multiple prey and predator species across habitats revealed important effects of predator × habitat and prey × habitat interactions on prey survival, which appeared to be related to species-specific predator and prey behavior in complex habitats. Significant species × habitat interactions imply that the impact of reduced seafloor habitat complexity may be more severe for some species than others. Our results indicate that the general effects of seafloor habitat complexity on juvenile fish survivorship may be broadly applicable, but that the interaction of particular habitats with search tactics of predators as well as habitat affinities and avoidance responses of prey can produce differences among species that contribute to variable mortality.     

Is arthropod predation exclusively satiation‐driven?

Functional response models differ in which factors limit predation (e.g. searching efficiency, prey handling time, digestion) and whether predation behaviour is governed by an internal physiological state (e.g. satiation). There is now much evidence that satiation is a key factor in understanding changes in foraging behaviour, and that many predators are effectively digestion limited. Here, we ask if predation in a predatory arthropod can be explained from satiation-driven behaviour alone, or if behaviour is also influenced by the density of prey other than via the effect of prey ingestion on satiation. To address this question a satiation-based predation model is formulated, for which parameters are estimated on the basis of observations on digestion rate, satiation-related prey searching rate and prey capture behaviour, basically under high prey density conditions. The model predictions are subsequently tested against longer term predation experiments carried out at high and low prey densities. Since satiation can easily be linked with egg production, these tests are carried out both for predation and oviposition.
The predator–prey systems under study consist of females of two predatory mite species ( Neoseiulus barkeri and N. cucumeris ) and the larvae of two thrips species ( Thrips tabaci and Frankliniella occidentalis ) as their prey. For N. barkeri foraging on T. tabaci , the model gives good predictions at both high (4 larvae cm⁻¹) and low (0.1–1 larvae cm⁻²) prey densities. For N. cucumeris foraging on F. occidentalis , the predictions hold at the high prey density, but are too low at low prey densities. Thus our analysis indicates that we cannot fully explain density-dependent predation rates from satiation-driven behaviour alone. Different mechanisms are suggested on how prey density may affect foraging efficiency other than via satiation.     

Positive indirect effect of aquatic insects on terrestrial prey is not offset by increased predator density

1. Changes in one prey species' density can indirectly affect the abundance of another prey species if a shared predator eats both species. Sometimes, indirect effects occur when prey straddle habitats, including when riparian predator populations grow in response to emergent aquatic insects and increase predation on terrestrial prey. However, predators may largely switch to aquatic insects or become satiated, reducing predation on terrestrial prey. 2. To determine the net indirect effect of aquatic insects on terrestrial arthropods via generalist spider predators, a field experiment was conducted mimicking midge influx and a wolf spider numerical response inside enclosures near an Icelandic lake. Lab mesocosms were also used to assess per capita rates of spider predation u nder differing levels of midge abundance. 3. Midges always decreased sentinel prey predation, but this effect increased with predator density. When midges were absent, predation increased 30% at a high spider density, but predation was equal between spider treatments when midges were present. In situ arthropods showed no effect of midge or spider treatments, although non‐significant abundance patterns were observed congruent with sentinel prey results. 4. In lab mesocosms, prey survivorship increased ≥50% where midges were present and rapidly saturated; the addition of 5, 20, 50, and 100 midges equivalently reduced spider predation, supporting predator distraction rather than satiation as the root cause. 5. The present results demonstrate a strong positive indirect effect of midges and broadly support the concept that predator responses to alternative prey are a major influence on the magnitude and direction of predator‐mediated indirect effects.     

The influence of vigilance on intraguild predation

Theoretical work on intraguild predation suggests that if a top predator and an intermediate predator share prey, the system will be stable only if the intermediate predator is better at exploiting the prey, and the top predator gains significantly from consuming the intermediate predator. In mammalian carnivore systems, however, there are examples of top predator species that attack intermediate predator species, but rarely or never consume the intermediate predator. We suggest that top predators attacking intermediate predators without consuming them may not only reduce competition with the intermediate predators, but may also increase the vigilance of the intermediate predators or alter the vigilance of their shared prey, and that this behavioral response may help to maintain the stability of the system. We examine two models of intraguild predation, one that incorporates prey vigilance, and a second that incorporates intermediate predator vigilance. We find that stable coexistence can occur when the top predator has a very low consumption rate on the intermediate predator, as long as the attack rate on the intermediate predator is relatively large. However, the system is stable when the top predator never consumes the intermediate predator only if the two predators share more than one prey species. If the predators do share two prey species, and those prey are vigilant, increasing top predator attack rates on the intermediate predator reduces competition with the intermediate predator and reduces vigilance by the prey, thereby leading to higher top predator densities. These results suggest that predator and prey behavior may play an important dynamical role in systems with intraguild predation.     

Suspended sediment alters predator–prey interactions between two coral reef fishes

Sediment derived from agriculture and development increases water turbidity and threatens the health of inshore coral reefs. In this study, we examined whether suspended sediment could change predation patterns through a reduction in visual cues. We measured survivorship of newly settled Chromis atripectoralis exposed to Pseudochromis fuscus, a common predator of juvenile damselfishes, in aquaria with one of four turbidity levels. Increased turbidity led to a nonlinear response in predation patterns. Predator-induced mortality was ~50 % in the control and low turbidity level, but exhibited a substantial increase in the medium level. In the highest turbidity level, predation rates declined to the level seen in the control. These results suggest an imbalance in how the predator and prey cope with turbidity. A turbidity-induced change to the outcome of predator–prey interactions represents a major change to the fundamental processes that regulate fish assemblages.     

Complex dynamics of a predator–prey–parasite system: An interplay among infection rate,predator's reproductive gain and preference

Parasites are considered as an important factor in regulating their host populations through trait-mediated effects. On the other hand, predation becomes particularly interesting in host–parasite systems because predation can significantly alter the abundance of parasites and their host population. The combined effects of parasites and predator on host population and community structure therefore may have larger effect. Different field experiments confirm that predators consume disproportionately large number of infected prey in comparison to their susceptible counterpart. There are also substantial evidences that predator has the ability to distinguish prey that have been infected by a parasite and avoid such prey to reduce fitness cost. In this paper we study the predator–prey dynamics, where the prey species is infected by some parasites and predators consume both the susceptible and infected prey with some preference. We demonstrate that complexity in such systems largely depends on the predator's selectivity, force of infection and predator's reproductive gain. If the force of infection and predator's reproductive gain are low, parasites and predators both go to extinction whatever be the predator's preference. The story may be totally different in the opposite case. Survival of species in stable, oscillatory or chaotic states, and their extinction largely depend on the predator's preference. The system may also show two coexistence equilibrium points for some parameter values. The equilibrium with lower susceptible prey density is always stable and the equilibrium with higher susceptible prey density is always unstable. These results suggest that understanding the consequences of predator's selectivity or preference may be crucial for community structure involving parasites.