Digenean trematodes are often characterized as being more specific with their gastropod first intermediate hosts than with the other hosts in their complex life cycles. Trematodes can be host specialists or generalists, sometimes exhibiting greater specialization at specific life stages. Digenean trematodes are valuable study organisms for exploring how biodiversity influences disease. In this study, we investigated the relationship between snail richness and trematode infection prevalence using data from a four-year study (2019-2022) of eight wetland sites in Alberta, Canada. Trematode species were classified as specialists or generalists at the first-intermediate host level, and generalized linear mixed-effects models were employed to assess the relationship between snail richness and overall, generalist, and specialist infection prevalence. The findings indicate that as snail richness increased, there was a significant increase in the overall and generalist infection prevalence. This trend was also noted for host specialists, but was not significant in the model. A decline in infection prevalence for all three categories was observed in the final sampling year compared to the first year, suggesting an impact of subtractive sampling on the trematode community over time. This highlights the potential influence of long-term sampling strategies on parasite community dynamics. Trematode and snail-trematode interaction sample completeness and rarefaction analyses indicated that high sample coverage was obtained, but further trematode species remain to be cataloged. Additionally, we uncovered potential host-switching events that could have important implications for disease monitoring and management strategies that rely on snail hosts, emphasizing the need for continued surveillance of host-parasite relationships.

Description of the data and file structure

As part of a larger study, snails were collected during four summers (June to September 2019-2022) from eight reclaimed wetlands approximately 25 kilometers northeast of Edmonton, Alberta, Canada. Snails were collected by hand or dip net and transported to the laboratory, where they were shed for trematode cercariae. Trematode infections were identified using DNA sequencing and assigned as specialist or generalist based on their observed interactions with snail hosts in this study.

Files and variables

Archive.zip

Description:

Includes the R scripts and associated data files for models and plots presented in the manuscript.

Bipartite_diagrams_script.R

Effect_of_snail_richness_on_trematode_richness.R

expanded_data.csv

iNEXT_interactions.csv

iNEXT_trematodes.csv

interaction_data_matrix_binary.csv

interaction_data_matrix_quant.csv

Proportion_of_snails_infected_plots.R

Sample_completeness_and_rarefaction_script.R

Snail_richness_modelling_script.R

Trematode_and_snail_diversity.csv

The files below contain the data to reproduce the analyses.

expanded_data.csv: All snail-trematode collection data, expanded for a data line for each snail collected.

* site: the sites at which the samples were collected. All sites are located in Strathcona County, Alberta. After setting up this sheet, site names were edited to all fit the same format for consistency.

* year: Year in which the sample was collected.

* snail_richness: The number of snail species collected from the indicated site during the indicated year.

* infection_status:

generalist = The snail was infected with a generalist trematode species.

specialist = The snail was infected with a specialist trematode species.

infected_noID = The snail was infected, but high-quality DNA sequences were not obtained, and no trematode ID was determined.

uninfected = Based on cercarial shedding, the snail was not infected.

* infected_generalist: A "1" if that snail was infected with a generalist trematode, a "0" if not.

* infected_specialist: A "1" if that snail was infected with a specialist trematode, a "0" if not.

* infected: A "1" if that snail was infected with a trematode (regardless of whether the trematode was identified using DNA or not), a "0" if not.

iNEXT_interactions.csv: Count data on observed snail-trematode interactions, i.e., those trematode infections identified using DNA.

* Interaction: snail and trematode interactions, denoted as "'snail species'.'trematode species'".

* Count: The number of times that the indicated trematode was observed to be infecting the indicated snail species.

iNEXT_trematodes.csv: Count data on observed trematode species.

* Species: List of trematode species observed.

* Count: Number of times each trematode species was observed from 2019-2022.

interaction_data_matrix_binary.csv: Data used to create the binary bipartite matrix.

* Rows: Snail species

* Columns: Trematode species

A "1" indicates that the indicated trematode had been identified to be infecting the indicated snail species at least once. A "0" indicates that the interaction had not been observed.

interaction_data_matrix_quant.csv: Data used to create the quantitative bipartite matrix.

* Rows: Snail species

* Columns: Trematode species

Values > 0 indicate the number of times the indicated trematode species had been identified as infecting the indicated snail species.

Trematode_and_snail_diversity.csv: Contains information on snails collected at each site in each collection year, along with the snail and trematode richness (species counts) observed at each site/year.

* site: the sites at which the samples were collected. All sites are located in Strathcona County, Alberta.

* year: Year in which the sample was collected.

* snail_richness: The number of snail species collected from the indicated site during the indicated year.

* trem_richness: The number of trematode species emerging from snail species collected at the indicated site during the indicated year. Based on identifications using DNA sequencing. Trematode infections that were not able to be identified using DNA were not included.

scripts

The files below contain all the necessary scripts to reproduce the analyses. Below, we provide a brief description of what each script does.

Bipartite_diagrams_script.R: This script generates both the binary and quantitative network matrices and calculates the metrics used to determine if a trematode species was binned as specialist or generalist based on the collections undertaken as part of this research.

Effect_of_snail_richness_on_trematode_richness.R: This script explores the relationship between snail richness and trematode richness.

Proportion_of_snails_infected_plots.R: This script generates the plots visualizing the proportion of snails infected at each snail richness level, for overall, generalist, and specialist infections.

Sample_completeness_and_rarefaction_script.R: This script generates the sample completeness and rarefaction curves for trematode species and snail-trematode interactions observed.

Snail_richness_modelling_script.R: This script explores the relationship between snail richness and trematode infections for overall, generalist, and specialist infections.

Code/software

All analyses were completed using R (version 4.3.1 (2023-06-16) -- "Beagle Scouts").

Data from: Trematode infection prevalence increases with snail richness: Observations from a 4-year study of snail-trematode interactions

Data files

Abstract

Description of the data and file structure

Files and variables

Data from: Trematode infection prevalence increases with snail richness: Observations from a 4-year study of snail-trematode interactions

Data files

Abstract

README: Data from: Trematode infection prevalence increases with snail richness: Observations from a 4-year study of snail-trematode interactions

Description of the data and file structure

Files and variables