Research Article |
Corresponding author: Giacomo Santoiemma ( giacomosanto@gmail.com ) Corresponding author: Davide Rassati ( davide.rassati@unipd.it ) Academic editor: Jianghua Sun
© 2024 Giacomo Santoiemma, Andrea Battisti, Claudine Courtin, Gianfranco Curletti, Massimo Faccoli, Nina Feddern, Joseph A. Francese, Emily K. L. Franzen, Filippo Giannone, Martin M. Gossner, Chantelle Kostanowicz, Matteo Marchioro, Davide Nardi, Ann M. Ray, Alain Roques, Jon Sweeney, Kate Van Rooyen, Vincent Webster, Davide Rassati.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Santoiemma G, Battisti A, Courtin C, Curletti G, Faccoli M, Feddern N, Francese JA, Franzen EKL, Giannone F, Gossner MM, Kostanowicz C, Marchioro M, Nardi D, Ray AM, Roques A, Sweeney J, Van Rooyen K, Webster V, Rassati D (2024) Testing a trapping protocol for generic surveillance of wood-boring beetles in heterogeneous landscapes. NeoBiota 95: 77-95. https://doi.org/10.3897/neobiota.95.129483
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Baited traps are a basic component of both specific and generic surveillance programs targeting wood-boring beetles at risk of introduction to new habitats because of global trade. Among the numerous protocols developed over the years for generic surveillance of longhorn beetles, jewel beetles, and bark and ambrosia beetles is the simultaneous use of black multi-funnel traps set up in the understory and green multi-funnel traps set up in the canopy of forested areas surrounding ports and other entry points. These traps are commonly baited with multi-lure blends of pheromones and host volatiles. In this study, we tested this trapping protocol in areas surrounding eight entry points located in Europe and North America to determine: i) the relative performance of black-understory traps and green-canopy traps among the targeted taxa; and ii) whether the dissimilarity among communities of beetles collected by the understory vs. canopy traps was affected by taxon and amount of forest cover in the traps’ surroundings. A total of 96,963 individuals belonging to 358 species of wood-boring beetles were collected, including 21 non-native species. Black-understory multi-funnel traps were generally more efficient than green-canopy multi-funnel traps for detecting longhorn beetles and bark and ambrosia beetles, whereas the opposite trend was observed for jewel beetles. Differences between beetle communities caught in black-understory and green-canopy traps were mainly attributed to differences in species richness in jewel beetles, while both differences in species richness and species turnover contributed to the dissimilarity between communities of longhorn beetles and bark and ambrosia beetle. The difference in the number of jewel beetle species caught by the two trapping methodologies decreased with increasing forest cover, whereas species turnover increased when moving from an urban-dominated to a forest-dominated landscape. Overall, these results suggest that the simultaneous use of both black-understory and green-canopy multi-funnel traps can be considered a very efficient approach for generic surveillance of longhorn beetles, jewel beetles and bark and ambrosia beetles in both urban-dominated and forest-dominated areas surrounding entry points.
Buprestidae, Cerambycidae, early-detection, exotic species, monitoring, Scolytinae
The continuous increase in global trade in recent decades, combined with deliberate plant introductions in the past, has resulted in increasing number of non-native insects moved outside their native ranges (
Among the numerous tools developed for surveillance of wood-boring beetles (
In addition to testing overall efficacy, there is an urgent need to better understand whether the simultaneous use of baited black multi-funnel traps placed in the understory and baited green multi-funnel traps placed in the canopy is always necessary, irrespective of the characteristics of the landscape. Previous studies showed that the efficacy of a trapping methodology can be context-dependent (e.g.,
In this study, we conducted a trapping experiment in areas surrounding eight entry points located in Europe and North America using black multi-funnel traps set up in the understory and green multi-funnel traps set up in the canopy, all baited with the same multi-component blend of longhorn beetle pheromones complemented with plant volatiles. We first compared the relative efficacy of black-understory traps and green-canopy traps for detecting different target taxa, i.e., longhorn beetles, jewel beetles and bark and ambrosia beetles. Second, we calculated dissimilarity indices to compare the communities of longhorn beetles, jewel beetles and bark and ambrosia beetles collected by black-understory vs. green-canopy traps, and then we tested the effect of the amount of forest cover in the trap surroundings on the dissimilarity indices. These analyses allowed us to investigate whether the simultaneous use of black-understory traps and green-canopy traps is required irrespective of the taxon and the landscape in which this protocol is used, or whether a simpler protocol (e.g., using only black-understory traps) may detect as many species of a particular taxon, depending on the surrounding landscape.
The study was conducted at eight sites in five different countries in the temperate zone of Europe and North America: France, Italy, Switzerland, Canada (Nova Scotia) and USA (Ohio) (Suppl. material
At each site we used sixteen black and sixteen green multi-funnel traps (Suppl. material
Traps were set up using a 2 km × 2 km grid as reference (Suppl. material
All traps were baited with a lure containing a blend of eight cerambycid pheromones attractive to a wide range of longhorn beetle species (
To investigate differences in the communities of wood-boring beetles collected in black-understory multi-funnel traps and green-canopy multi-funnel traps, we used the β-diversity approach outlined in
Given “a” = number of species exclusive to the first community, “b” = number of species exclusive to the second community, and “c” = number of species common to both communities, the β-diversity is given by the Jaccard dissimilarity index:
βcc = (a + b)/(a +b +c)
with values ranging from 0 (perfect similarity) to 1 (total dissimilarity). The species richness difference component is given by:
βrich = |a + b|/(a +b +c)
with values ranging from 0 (no richness difference) to 1 (maximum richness difference). The species replacement component is given by:
β-3 = 2 min (a, b)/(a +b +c)
with values ranging from 0 (no replacement) to 1 (maximum replacement). To calculate these indices, data collected across the entire sampling season from black-understory and green-canopy traps (i.e., total catch per trap over the entire trapping season) of each grid cell at each site were paired, creating n × m presence/absence matrices for each taxon, whereby n = 2 (one row for each trapping method) and m = number of species. Then, for each matrix, the three indices were computed using the “vegan” package (
Forest patches around each trap were manually digitized by visual inspection of high-resolution satellite images in Google Earth Pro (
We used generalized linear mixed models for all the analyses. Data collected from all sites were analyzed together to increase both the statistical power of the models and the gradient of forest cover around the traps.
First, we tested the effect of the taxon and the trapping methodology on species richness and abundance. Species richness (i.e., total number of species) and abundance (i.e., total number of individuals) for each trap and pooled over the sampling rounds were considered as response variables. The taxon (categorical variable: longhorn beetles, jewel beetles, and bark and ambrosia beetles), the trapping methodology (categorical variable: black-understory and green-canopy multi-funnel traps) and their interaction were considered as explanatory variables. The site identity, the identity of each grid cell within each site and the identity of each trap within each grid cell were included in the models as nested random factors.
Second, we tested the effect of the taxon and the forest cover on beta-diversity indices. The three beta-diversity indices βcc, βrich and β-3 calculated for each pair of traps (within a cell) were considered as response variables. The taxon (categorical variable: longhorn beetles, jewel beetles, and bark and ambrosia beetles), the forest cover (continuous variable: mean % of forest cover in the buffers of 250 m radius around the pair of traps present in the same cell) and their interaction were considered as explanatory variables. The site identity and the identity of each cell of the grid within each site were included in the models as nested random factors.
Models were fitted with a Poisson distribution (log link function) for species richness, negative binomial distribution (log link function) for abundance, and Gaussian distribution for the beta-diversity indices. Pairwise comparisons between each taxon and between the two trapping methodologies within each taxon were run using Tukey correction of p-values. All the analyses were carried out in R software (
A total of 96,963 individuals belonging to 358 species of wood-boring beetles were collected (Suppl. material
World map describing the communities of longhorn beetles, jewel beetles, and bark and ambrosia beetles collected at each experimental site. Circle size indicates the number of trapped species ranging from 55 (smallest circle) to 100 (biggest circle). The different colors within each circle indicate the relative percentage of species attributed to each taxon: red = longhorn beetles; green = jewel beetles; blue = bark and ambrosia beetles. Numbers in yellow circles represent the different study sites according to Suppl. material
Species richness was significantly affected by taxon and by the interaction between taxon and trapping methodology (Table
Mean (± standard error) species richness and abundance of longhorn beetles (A, D), jewel beetles (B, E), and bark and ambrosia beetles (C, F) for each trapping methodology. Asterisks within the plots indicate the statistical significance level from pairwise comparisons between the two trapping methodologies within each taxon from the generalized linear mixed models. Asterisks under the plots indicate the statistical significance level from pairwise comparisons among the three taxa from the generalized linear mixed models. P-values: * = 0.01 - 0.05; ** = 0.001 - 0.01; *** = < 0.001; ns = not significant (> 0.05). P-values were adjusted by Tukey correction. Model details are provided in Table
Analysis of deviance table from the generalized linear mixed models testing the effects of taxon (longhorn beetles, jewel beetles, and bark and ambrosia beetles), trapping methodology (black-understory multi-funnel traps and green-canopy multi-funnel traps) and their interaction on species richness (Poisson distribution; log link function) and abundance (negative binomial distribution; log link function). Nested random structure used for both models: ~1|Site/Cell/Trap. Type II Wald chi-square tests (χ2), degrees of freedom (df), p-values, and lognormal marginal (mR2) and conditional (cR2) pseudo R-squared are provided for both models.
χ2 | df | p-value | |
---|---|---|---|
Species richness | |||
Taxon | 659.517 | 2 | < 0.001 |
Methodology | 0.455 | 1 | 0.500 |
Taxon × Methodology | 161.154 | 2 | < 0.001 |
mR2 = 0.73, cR2 = 0.87 | |||
Abundance | |||
Taxon | 1040.747 | 2 | < 0.001 |
Methodology | 20.737 | 1 | < 0.001 |
Taxon × Methodology | 274.916 | 2 | < 0.001 |
mR2 = 0.73, cR2 = 0.86 |
Abundance was significantly affected by all tested variables (Table
βcc and βrich were significantly affected by taxon and forest cover but not by their interaction, while β-3 was significantly affected by taxon and by the interaction between taxon and forest cover (Table
Effect of forest cover in a buffer of 250 m radius around the traps on the dissimilarity among wood-boring beetle communities found in black understory multi-funnel traps and green canopy multi-funnel traps, considering the total beta-diversity βcc (A–C) and its components species richness difference βrich (D–F) and species replacement β-3 (G–I). Plots include model estimate (colored line) and 95% confidence intervals (colored shading). Model details are provided in Table
Analysis of deviance table from the generalized linear mixed models testing the effects of taxon (longhorn beetles, jewel beetles, and bark and ambrosia beetles), forest cover (mean % in buffers of 250 m radius around the pair of traps) and their interaction on β-diversity (βcc), species richness difference (βrich) and species replacement (β-3) indices (Gaussian distribution used for all models). Nested random structure used for all models: ~1|Site/Cell. Type II Wald chi-square tests (χ2), degrees of freedom (df), p-values, and delta marginal (mR2) and conditional (cR2) pseudo R-squared are provided for all models. Pairwise comparisons among taxa are provided in Suppl. material
χ2 | df | p-value | |
---|---|---|---|
βcc | |||
Taxon | 391.167 | 2 | < 0.001 |
Forest | 4.282 | 1 | 0.039 |
Taxon × Forest | 0.899 | 2 | 0.638 |
mR2 = 0.53, cR2 = 0.58 | |||
βrich | |||
Taxon | 262.048 | 2 | < 0.001 |
Forest | 4.617 | 1 | 0.032 |
Taxon × Forest | 5.073 | 2 | 0.079 |
mR2 = 0.45, cR2 = 0.47 | |||
β-3 | |||
Taxon | 17.470 | 2 | < 0.001 |
Forest | 0.426 | 1 | 0.514 |
Taxon × Forest | 7.250 | 2 | 0.027 |
mR2 = 0.07, cR2 = 0.10 |
Our study confirmed that the use of baited traps around high-risk sites represents an efficient approach for generic surveillance of wood-boring beetles (
Comparing the efficacy of the two trapping methodologies, we found that black multi-funnel traps baited with the multi-lure blend and set up in the understory caught significantly more bark and ambrosia beetle species and individuals than green multi-funnel traps baited with the same blend and set up in the canopy, but significantly less jewel beetle species and individuals. For longhorn beetles, a difference between the two trapping methodologies was found in the total number of individuals (more in black-understory traps), but not in the number of species. The trends observed in our study are likely explained by the combined effect of trap height and trap color (
Analyzing dissimilarity indices, we also found that differences between beetle communities caught in black-understory traps and green-canopy traps were more evident for jewel beetles than for both longhorn beetles and bark and ambrosia beetles. For jewel beetles, these differences were mainly attributed to differences in species richness, while both differences in species richness and species turnover contributed to explain the dissimilarity of communities of longhorn beetles and bark and ambrosia beetles between trapping methodologies. These results are especially useful when planning surveillance activities targeting only one of the three taxa. For longhorn beetles and bark and ambrosia beetles, the simultaneous use of black-understory and green-canopy multi-funnel traps is always recommended, as different species with different flight patterns can be caught by these two trapping methodologies. Previous studies testing different trap types, environmental gradients, and/or lures (
Baited traps are an essential component of both specific and generic surveillance programs around the world, making the development of efficient trapping protocols a research priority. Here we showed that the simultaneous use of black-understory and green-canopy multi-funnel traps baited with a multi-lure blend of longhorn beetle pheromones and host volatiles can be considered a very efficient approach for generic surveillance of longhorn beetles, jewel beetles and bark and ambrosia beetles in both urban-dominated and forest-dominated areas surrounding entry points. The only case in which this protocol can be simplified using only green-canopy multi-funnel traps is when targeting jewel beetles in urban-dominated landscapes. Despite the general efficiency of the trapping protocol we tested, it is very likely that not all longhorn beetle, bark and ambrosia beetle and jewel beetle fauna present in the sampled area was represented by trap catches.
We thank Enrico Ruzzier, Giacomo Cavaletto, Caterina de Sandre, Gianluigi Berardi, Ryan Lawson, Abigail Morton, Ifidion Ohiomah, Erika Ratcliff, and Ryan Rugg for helping in both lab and field activities. We are indebted to the managers of the Parc du Sausset at Aulnay/Bois (France) for authorizing the settlement of the traps in their urban park. This material was made possible, in part, by a Cooperative Agreement from the United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS). It may not necessarily express APHIS’ views.
The authors have declared that no competing interests exist.
No ethical statement was reported.
This work was supported by the HOMED project (HOlistic Management of Emerging Forest Pests and Diseases) funded by the European Union’s Horizon 2020 research and innovation program under grant agreement No. 771271 (https://homed-projecteu/). AMR received funding from the US Department of Agriculture Cooperative Agreement #AP18PPQS&T00C169 and #AP19PPQS&T00C082, and from the Xavier University Undergraduate Research Fund.
GS: data curation, formal analysis, writing – original draft, writing – review & editing; AB: funding acquisition, writing – review & editing; CC: lure preparation, methodology; GC: beetle identification; MF: beetle identification, writing – review & editing; NF: investigation; JAF: funding acquisition, investigation, writing – review & editing; EKLF: beetle identification, investigation; FG: beetle identification; MMG: funding acquisition, investigation, writing – review & editing; CK: beetle identification, investigation; MM: conceptualization, investigation; DN: conceptualization, data curation, formal analysis; AMR: funding acquisition, investigation, writing – review & editing; AR: investigation, beetle identification, funding acquisition, writing – review & editing; JS: funding acquisition, investigation, writing – review & editing; KVR: beetle identification, investigation; VW: beetle identification, investigation; DR: conceptualization, data curation, project administration, validation, visualization, writing – original draft, writing – review & editing. All authors approved the text.
Giacomo Santoiemma https://orcid.org/0000-0002-3226-9253
Andrea Battisti https://orcid.org/0000-0002-2497-3064
Massimo Faccoli https://orcid.org/0000-0002-9355-0516
Martin M. Gossner https://orcid.org/0000-0003-1516-6364
Matteo Marchioro https://orcid.org/0000-0003-2301-1047
Alain Roques https://orcid.org/0000-0002-3734-3918
Jon Sweeney https://orcid.org/0000-0003-3391-2375
Davide Rassati https://orcid.org/0000-0001-7778-0349
All of the data that support the findings of this study are available in the main text or Supplementary Information.
Testing a trapping protocol for generic surveillance of wood-boring beetles in heterogeneous landscapes
Data type: docx