Mutual dilution of infection by an introduced parasite in native and invasive stream fishes across Hawaii

SUMMARYThe presence of introduced hosts can increase or decrease infections of co-introduced parasites in native species of conservation concern. In this study, we compared parasite abundance, intensity, and prevalence between nativeAwaous stamineusand introduced poeciliid fishes by a co-introduced nematode parasite (Camallanus cotti) in 42 watersheds across the Hawaiian Islands. We found that parasite abundance, intensity and prevalence were greater in native than introduced hosts. Parasite abundance, intensity and prevalence withinA. stamineusvaried between years, which largely reflected a transient spike in infection in three remote watersheds on Molokai. At each site we measured host factors (length, density of native host, density of introduced host) and environmental factors (per cent agricultural and urban land use, water chemistry, watershed area and precipitation) hypothesized to influenceC. cottiabundance, intensity and prevalence. Factors associated with parasitism differed between native and introduced hosts. Notably, parasitism of native hosts was higher in streams with lower water quality, whereas parasitism of introduced hosts was lower in streams with lower water quality. We also found that parasite burdens were lower in both native and introduced hosts when coincident. Evidence of a mutual dilution effect indicates that introduced hosts can ameliorate parasitism of native fishes by co-introduced parasites, which raises questions about the value of remediation actions, such as the removal of introduced hosts, in stemming the rise of infectious disease in species of conservation concern.

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Intrinsic Prey Preference and Selection of the Giant Gartersnake: A Threatened Predator in a Nonnative Prey-Dominated Community

Journal of Fish and Wildlife Management ◽

10.3996/062019-jfwm-051 ◽

2020 ◽

Vol 11 (1) ◽

pp. 164-173

Author(s):

Julia S.M. Ersan ◽

Brian J. Halstead ◽

Erica L. Wildy ◽

Michael L. Casazza ◽

Glenn D. Wylie

Keyword(s):

Exotic Species ◽

Native Species ◽

Prey Selection ◽

Central Valley ◽

Prey Preference ◽

Live Prey ◽

Species Of Conservation Concern ◽

Conservation Concern ◽

Behavioral Trials ◽

Selection Of

Abstract The introduction of exotic species into an environment can introduce great change in the trophic dynamics of native species. This is of even greater concern if the native species is of conservation concern. The giant gartersnake, Thamnophis gigas, an endemic predator of the Central Valley of California and a species of conservation concern at the state and federal levels, has declined as a result of conversion of its once vast wetland habitat to agriculture. Another anthropogenic factor contributing to this snake's changing ecology is the introduction of nonnative prey into the species' habitats. These introductions have resulted in a prey community that is almost completely composed of exotic species and have potential for considerable effects. In order to assess prey preference and selection we performed three sets of behavioral trials on naïve neonates. We examined 1) neonate prey preference in response to olfactory cues of prepared prey extracts, 2) neonate consumption of different live prey items presented simultaneously; and 3) terrestrial feeding behavior and/or latency to successful attack. Results from the olfactory study suggest that native Sierran treefrogs, Pseudacris sierra, are preferred by neonates. Results from consumption trials suggest that neonates are more likely to select frog species than fish species. This is the first study that we are aware of that examines prey selection of this threatened species and serves to inform its conservation and management.

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The dilution effect in a freshwater mutualism: impacts of introduced host species on native symbionts

10.22541/au.163277469.97557253/v1 ◽

2021 ◽

Author(s):

Robert Creed ◽

Gretchen L. Bailey ◽

James Skelton ◽

Bryan L. Brown

Keyword(s):

Host Species ◽

Host Density ◽

Dilution Effect ◽

Negative Effects ◽

Parasite Abundance ◽

Host Diversity ◽

Negative Effect ◽

Dilution Effects ◽

Native Crayfish ◽

Native Host

The dilution effect was originally proposed to describe the negative effect of increased host diversity on parasite abundance; with greater host diversity, parasite levels per host are predicted to be lower due to a higher probability of dispersing parasites encountering non-competent hosts. Dilution effects could also occur in many mutualisms if dispersing symbionts encounter hosts that vary in their competency. The introduction of non-native hosts can change community competency of a local group of host species. Crayfish introductions are occurring world-wide and these introductions are likely disrupting native crayfish-symbiont systems. Branchiobdellidan symbionts declined on native Cambarus crayfish occurring in the presence and absence of non-native Faxonius crayfish in the New River, USA. We performed an experiment investigating the effect of host density (1 vs 2 native hosts) and host diversity (1 native host and 1 introduced host) on branchiobdellidan abundance. The introduced F. cristavarius is a non-competent host for these worms. Six C. ingens were stocked on a C. chasmodactylus in each treatment and worm numbers were followed over 34 days. Worm numbers decreased over time on C. chasmodactylus alone and in the treatment in which a C. chasmodactylus was paired with an F. cristavarius. Worm numbers remained highest in the 2 C. chasmodactylus treatment . There was no significant effect of host diversity on worm reproduction. Crayfish invasions may have negative effects on mutualistic symbionts depending on the competence of introduced hosts. Loss of native symbionts is one of the potential hidden, negative effects of invasions on native freshwater diversity.

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Reducing the primary exposure risk of Henderson crakes (Zapornia atra) during aerial broadcast eradication by selecting appropriate bait colour

Wildlife Research ◽

10.1071/wr15198 ◽

2016 ◽

Vol 43 (4) ◽

pp. 298 ◽

Cited By ~ 4

Author(s):

Steffen Oppel ◽

Jennifer L. Lavers ◽

Alexander L. Bond ◽

Gavin Harrison

Keyword(s):

Mixed Models ◽

Native Species ◽

Exposure Risk ◽

Island Endemic ◽

Invasive Predators ◽

Species Of Conservation Concern ◽

In Captivity ◽

Specific Variation ◽

Conservation Concern ◽

Native Invasive

Context Operations to eradicate non-native invasive predators from islands frequently put native species at risk of consuming harmful substances, such as poison bait. The incorporation of certain colours in poison-bait pellets may reduce the risk of bait consumption and, therefore, non-target mortality. Previous work indicated that birds generally avoid blue or green colours; however, there is substantial inter-specific variation in this preference, and more experimental work on species of conservation concern is needed. Aims We tested whether a globally threatened island endemic, the Henderson crake (Zapornia atra), which suffered substantial mortality during a rat-eradication attempt on Henderson Island in 2011, would consume fewer blue than green pellets, which were used during the previous eradication attempt. Methods We held 22 Henderson crakes in captivity and provided them with either blue or green non-toxic pellets for 5 days in June and July 2015. We measured consumption and used linear mixed models to evaluate whether bait colour influenced consumption. Key results Henderson crakes did not consume any dry pellets, and all trials were conducted with wet bait pellets. We found slightly lower consumption of blue pellets than green pellets, and substantial variation among individuals. Females (n = 17) consumed 24% less blue than green bait, whereas males (n = 5) consumed 77% less blue than green bait. Conclusion Henderson crakes are unlikely to consume dry pellets, and will likely consume fewer blue than green bait pellets. Implications We recommend that any future rat eradication on Henderson Island considers using blue rather than green baits and targets dry weather to reduce the risk of Henderson crakes consuming toxic rodenticide bait pellets.

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Biodiversity inhibits parasites: Broad evidence for the dilution effect

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1506279112 ◽

2015 ◽

Vol 112 (28) ◽

pp. 8667-8671 ◽

Cited By ~ 258

Author(s):

David J. Civitello ◽

Jeremy Cohen ◽

Hiba Fatima ◽

Neal T. Halstead ◽

Josue Liriano ◽

...

Keyword(s):

Disease Risk ◽

Meta Analysis ◽

Host Density ◽

Dilution Effect ◽

Wildlife Diseases ◽

Parasite Abundance ◽

Effect Hypothesis ◽

Zoonotic Parasites ◽

Dilution Effects ◽

Plant Herbivore

Infectious diseases of humans, wildlife, and domesticated species are increasing worldwide, driving the need to understand the mechanisms that shape outbreaks. Simultaneously, human activities are drastically reducing biodiversity. These concurrent patterns have prompted repeated suggestions that biodiversity and disease are linked. For example, the dilution effect hypothesis posits that these patterns are causally related; diverse host communities inhibit the spread of parasites via several mechanisms, such as by regulating populations of susceptible hosts or interfering with parasite transmission. However, the generality of the dilution effect hypothesis remains controversial, especially for zoonotic diseases of humans. Here we provide broad evidence that host diversity inhibits parasite abundance using a meta-analysis of 202 effect sizes on 61 parasite species. The magnitude of these effects was independent of host density, study design, and type and specialization of parasites, indicating that dilution was robust across all ecological contexts examined. However, the magnitude of dilution was more closely related to the frequency, rather than density, of focal host species. Importantly, observational studies overwhelmingly documented dilution effects, and there was also significant evidence for dilution effects of zoonotic parasites of humans. Thus, dilution effects occur commonly in nature, and they may modulate human disease risk. A second analysis identified similar effects of diversity in plant–herbivore systems. Thus, although there can be exceptions, our results indicate that biodiversity generally decreases parasitism and herbivory. Consequently, anthropogenic declines in biodiversity could increase human and wildlife diseases and decrease crop and forest production.

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Experimental removal of introduced slider turtles offers new insight into competition with a native, threatened turtle

PeerJ ◽

10.7717/peerj.7444 ◽

2019 ◽

Vol 7 ◽

pp. e7444 ◽

Cited By ~ 2

Author(s):

Max R. Lambert ◽

Jennifer M. McKenzie ◽

Robyn M. Screen ◽

Adam G. Clause ◽

Benjamin B. Johnson ◽

...

Keyword(s):

Native Species ◽

Field Experiments ◽

Slider Turtle ◽

Species Of Conservation Concern ◽

Ecological Resources ◽

Mesocosm Experiments ◽

In The Wild ◽

Western Pond Turtle ◽

Negative Impacts ◽

Conservation Concern

The red-eared slider turtle (Trachemys scripta elegans; RES) is often considered one of the world’s most invasive species. Results from laboratory and mesocosm experiments suggest that introduced RES outcompete native turtles for key ecological resources, but such experiments can overestimate the strength of competition. We report on the first field experiment with a wild turtle community, involving introduced RES and a declining native species of conservation concern, the western pond turtle (Emys marmorata; WPT). Using a before/after experimental design, we show that after removing most of an introduced RES population, the remaining RES dramatically shifted their spatial basking distribution in a manner consistent with strong intraspecific competition. WPT also altered their spatial basking distribution after the RES removal, but in ways inconsistent with strong interspecific competition. However, we documented reduced levels of WPT basking post-removal, which may reflect a behavioral shift attributable to the lower density of the turtle community. WPT body condition also increased after we removed RES, consistent with either indirect or direct competition between WPT and RES and providing the first evidence that RES can compete with a native turtle in the wild. We conclude that the negative impacts on WPT basking by RES in natural contexts are more limited than suggested by experiments with captive turtles, although wild WPT do appear to compete for food with introduced RES. Our results highlight the importance of manipulative field experiments when studying biological invasions, and the potential value of RES removal as a management strategy for WPT.

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Parasite abundance decreases with host density: evidence of the encounter-dilution effect for a parasite with a complex life cycle

Hydrobiologia ◽

10.1007/s10750-016-2874-8 ◽

2016 ◽

Vol 784 (1) ◽

pp. 201-210 ◽

Cited By ~ 12

Author(s):

Julia C. Buck ◽

William I. Lutterschmidt

Keyword(s):

Life Cycle ◽

Host Density ◽

Dilution Effect ◽

Complex Life Cycle ◽

Parasite Abundance

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Relation of urban land-use and dry-weather, storm, and snowmelt flow characteristics to stream-water quality, Shunganunga Creek basin, Topeka, Kansas

10.3133/wsp2283 ◽

1987 ◽

Keyword(s):

Water Quality ◽

Land Use ◽

Stream Water ◽

Flow Characteristics ◽

Urban Land ◽

Urban Land Use ◽

Stream Water Quality

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Advancing improvement in riverine water quality caused a non-native fish species invasion and native fish fauna recovery

Scientific Reports ◽

10.1038/s41598-021-93751-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Łukasz Głowacki ◽

Andrzej Kruk ◽

Tadeusz Penczak

Keyword(s):

Water Quality ◽

Fish Species ◽

Native Species ◽

Interference Competition ◽

Fish Fauna ◽

Species Traits ◽

Native Fish ◽

Biological Degradation ◽

Species Invasion ◽

Prussian Carp

AbstractThe knowledge of biotic and abiotic drivers that put non-native invasive fishes at a disadvantage to native ones is necessary for suppressing invasions, but the knowledge is scarce, particularly when abiotic changes are fast. In this study, we increased this knowledge by an analysis of the biomass of most harmful Prussian carp Carassius gibelio in a river reviving from biological degradation. The species' invasion followed by the invasion's reversal occurred over only two decades and were documented by frequent monitoring of fish biomass and water quality. An initial moderate improvement in water quality was an environmental filter that enabled Prussian carp’s invasion but prevented the expansion of other species. A later substantial improvement stimulated native species’ colonization of the river, and made one rheophil, ide Leuciscus idus, a significant Prussian carp’s replacer. The redundancy analysis (RDA) of the dependence of changes in the biomass of fish species on water quality factors indicated that Prussian carp and ide responded in a significantly opposite way to changes in water quality in the river over the study period. However, the dependence of Prussian carp biomass on ide biomass, as indicated by regression analysis and analysis of species traits, suggests that the ecomorphological similarity of both species might have produced interference competition that contributed to Prussian carp’s decline.

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