Creative Commons License 2021 Volume 8 Issue 4

Tomicus species (Coleoptera: Curculionidae: Scolytinae) as Invasive Forest Pest to Mexico with Ecological Niche Modeling


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Abstract

Scolitine bark beetles of the genus Tomicus (Coleoptera: Curculionidae: Scolytinae) include some forestry pests of major importance worldwide, with the capacity for invading new habitats and threatening native forest populations and are considered as exotic species for America. However, Tomicus piniperda L. the common pine shoot beetle has invaded North America recently and specimens of T. minor Hart have been intercepted in the United States. The possibility for an invasion of Mexico grows day by day. A preventive strategy to evaluate the invasion by exotic species is ecological niche modeling. Using bioclimatic variables, distributional data, entropy algorithm, and modeling software, the ecological niche of three Tomicus species was calculated and projected to Mexico. Results of this analysis showed potential environmental suitability in Mexico for T. destruens (small and dispersed areas in the Altiplano Norte biogeographic province and an isolated area in the Tamaulipeca biogeographic province) and T. minor (high suitability in the biogeographical provinces of Baja California, California, Sonorense, Altiplano Norte and Altiplano Sur, Tamaulipeca and small areas in eastern Eje Volcánico.). For T. piniperda, no environmental suitability was projected in Mexico. Additional ecological requirements, host preferences, and local fauna competition, as factors influencing the potential invasion of T. minor in Mexico, are discussed. Our work has an important impact because Mexico is one of the most important countries with high pine diversity in the world and shows an important impact on pine´s hot spots.


How to cite this article
Vancouver
López-Martínez V, Pérez-De la O NB, Aguirre-Cadena JF, Brindis-Santos AI, Osorio-Espinoza H. Tomicus species (Coleoptera: Curculionidae: Scolytinae) as Invasive Forest Pest to Mexico with Ecological Niche Modeling. Entomol Appl Sci Lett. 2021;8(4):33-42. https://doi.org/10.51847/dSKxbALGsz
APA
López-Martínez, V., Pérez-De la O, N. B., Aguirre-Cadena, J. F., Brindis-Santos, A. I., & Osorio-Espinoza, H. (2021). Tomicus species (Coleoptera: Curculionidae: Scolytinae) as Invasive Forest Pest to Mexico with Ecological Niche Modeling. Entomology and Applied Science Letters, 8(4), 33-42. https://doi.org/10.51847/dSKxbALGsz

Tomicus species (Coleoptera: Curculionidae: Scolytinae) as Invasive Forest Pest to Mexico with Ecological Niche Modeling

 

Víctor López-Martínez1, Nidia Bélgica Pérez-De la O2*, Juan Francisco Aguirre-Cadena3, Alfredo Isaac Brindis-Santos3, Humberto Osorio-Espinoza3

 

1Faculty of Agricultural Sciences, Autonomous University of the State of Morelos, Cuernavaca, Mexico.

2Phitosanity-Entomology and Acarology Postgraduate Program, College of Postgraduate, Montecillo, Mexico.

3Faculty of Agricultural Sciences, Chiapas Autonomous University, Huehuetan, Mexico.


ABSTRACT

Scolitine bark beetles of the genus Tomicus (Coleoptera: Curculionidae: Scolytinae) include some forestry pests of major importance worldwide, with the capacity for invading new habitats and threatening native forest populations and are considered as exotic species for America. However, Tomicus piniperda L. the common pine shoot beetle has invaded North America recently and specimens of T. minor Hart have been intercepted in the United States. The possibility for an invasion of Mexico grows day by day. A preventive strategy to evaluate the invasion by exotic species is ecological niche modeling. Using bioclimatic variables, distributional data, entropy algorithm, and modeling software, the ecological niche of three Tomicus species was calculated and projected to Mexico. Results of this analysis showed potential environmental suitability in Mexico for T. destruens (small and dispersed areas in the Altiplano Norte biogeographic province and an isolated area in the Tamaulipeca biogeographic province) and T. minor (high suitability in the biogeographical provinces of Baja California, California, Sonorense, Altiplano Norte and Altiplano Sur, Tamaulipeca and small areas in eastern Eje Volcánico.). For T. piniperda, no environmental suitability was projected in Mexico. Additional ecological requirements, host preferences, and local fauna competition, as factors influencing the potential invasion of T. minor in Mexico, are discussed. Our work has an important impact because Mexico is one of the most important countries with high pine diversity in the world and shows an important impact on pine´s hot spots.

Keywords: Invasive species, Ecological niche, Pine shoot beetles, Mexican biogeographic provinces.


INTRODUCTION

 

Mexico is considered a megadiverse country [1] its plant composition, abundance, and distribution are favored by the combination of neotropical/Nearctic elements [2]. Furthermore, the time and formation of the mountainous systems, help to disperse forests across the country [3].

Pinaceae found in Mexico space, geographic complexity, and weather for evolution, i.e., is a Pinus diversity and radiation center [4], with at least 23 endemic species [5, 6]. 49 species of the genus are recorded for the country, distributed in its entire surface, except tropical lowlands of Tabasco and Yucatan [5]. However, forest cover in Mexico is reduced annually by economic (poverty), social (population growth, migration), political (governmental programs), and climatic factors (drought, climatic changes) [7, 8]. As consequence, populations of 21 species are under threat or special protection [5, 9].

In the case of coniferous forests, to this set of adverse factors, an additional threat is invasive species, mainly by insect pests [10]. Of this group of arthropods, some species of the genus Tomicus (Coleoptera: Curculionidae: Scolytinae) have gained prominence for invading new habitats and for threatening native forest populations by direct and/or indirect damages. Tomicus species live in Pinaceae (mainly Pinus) [11] and are classified into eight species [T. armandii Li & Zhang, T. brevipilosus Eggers, T. destruens Woll., T. minor Hart., T. piniperda L., T. puellus Reitter, T. pilifer Spessivtsev and T. yunnanensis (Kirkendall & Faccoli)], considered as pests in several regions of the world [11]. Tomicus armandii, T. brevipilosus, T. pilifer, T. puellus, and T. yunnanensis are distributed in central, southwestern, and eastern China [11] but T. destruens, T. minor, and T. piniperda have a wider distribution, with major forestry importance [11].

Tomicus piniperda, the common pine shoot beetle, is considered a major scolytinae pest, with a widely Euroasian distribution, and established in North America [12], infesting Christmas tree plantations [13]. Tomicus piniperda is showing an incredible adaptation and wider distribution in Canada and the United States [14]. In its natural range, T. piniperda frequently is associated with the lesser pine shoot beetle, T. minor, combined attack of both species breaks natural tree resistance [15]. Interception records for T. minor for the USA from countries outside their original distribution pattern have been reported [16]. For some authors is considered as a secondary pest, but T. minor threats Pinus species in China [17]. Tomicus destruens occurs only in Mediterranean Basin and Macaronesian Islands [17, 18] and has been considered as an injurious pest for Mediterranean pine forests [19]. In general, Tomicus species infest Pinus trunk and branches, inducing foliage malformations and reducing their commercial value, trees can be destroyed by massive infestation or favoring secondary infestations killing the host by stress

Mexico is an importer of Christmas pines from the USA and Canada, 25,859 metric tons were imported in 2014 [20] movement of plant material favors the entry of harmful fauna to native flora and could threaten the local wood market. Locally, Pinus contributes 75.1 % of annual wood production [21].

With this perspective, in this manuscript, we used ecological niche modeling, as a strategy to calculate as far as possible, the climate compatibility for three Tomicus (Coleoptera: Curculionidae: Scolytinae) species considered invasives in other regions of the world. The finality is to provide data that Mexican phytosanitary agencies could use to make better management choices [22], or for the establishment of areas for sampling/monitoring or implementing preventive management tactics.

MATERIALS AND METHODS

Distribution record of Tomicus spp. and Pinus spp

Distribution data of three Tomicus especies (T. destruens, T. minor and T. piniperda) were compilated from scientific literature and the database Global Biodiversity Information Facility (GBIF) [14, 15, 17, 19, 23-27].

 

Model calibration

Good practices for working with distributional data were used, duplicated points were removed, and for reducing spatial correlation, points with a minor distance of 10 km between them were erased with the package ‘spThin’ in Rstudio® ver. 3.3. The original database for T. minor was integrated by 3,825 points, after depuration, the final compilation consisted of 747 points, 561 used for training model (75 %), and 186 for model evaluation (25 %). For T. piniperda, from 5,504 initial points, the final database was integrated with 1,357 points, 1,018 used for training (75%), and 339 for model evaluation. In the case of T. destruens, the initial data was integrated by 237 points (25 %), and after the good practices were applied, the final database was integrated by 145 points, 109 (75%) used for training, and 36 (25 %) for model evaluation.

The accessible area for each species (M), defined as the origin areas according to its dispersion capacity [28], according to the BAM diagram (M= Species accessibility, B = Biotic variables, A= Abiotic variables) [28]. Areas were delimited with the world biogeographic ecoregions [29] in Qgis ver. 3.16.11®. 19 bioclimatic variables were downloaded from www.worldclim.org with a spatial resolution of 2.5 minutes, but bioclimatic variables 8, 9, 18, and 19 were discarded due to problems with some pixel values (Table 1) [18].

 

Table 1. Bioclimatic variables were used for the ecological niche model calculation of three Tomicus species (Coleoptera: Curculionidae: Scolytinae).

Bioblimatic variable

BIO1 = Annual Mean Temperature

BIO2 = Mean Diurnal Range (Mean of monthly (max temp - min temp))

BIO3 = Isothermality (BIO2/BIO7) (×100)

BIO4 = Temperature Seasonality (standard deviation ×100)

BIO5 = Max Temperature of Warmest Month

BIO6 = Min Temperature of Coldest Month

BIO7 = Temperature Annual Range (BIO5-BIO6)

BIO10 = Mean Temperature of Warmest Quarter

BIO11 = Mean Temperature of Coldest Quarter

BIO12 = Annual Precipitation

BIO13 = Precipitation of Wettest Month

BIO14 = Precipitation of Driest Month

BIO15 = Precipitation Seasonality (Coefficient of Variation)

BIO16 = Precipitation of Wettest Quarter

BIO17 = Precipitation of Driest Quarter

 

A Spearman correlation with the environmental data was performed NicheToolBox (http://shiny.conabio.gob.mx:3838/nichetoolb2/), a tool for exploratory data analysis in ecological niche modeling (ENM) for the elimination of correlated variables (MNE) [30]. Variables without correlation were used to build two sets of variables. Model candidates were designed with Rstudio® ver. 3.3 and the package kuenm, this is a tool to perform detailed development of ecological niche models using Maxent [31]. 310 candidate models were created with the function kuenm_cal of the ‘kuenm’ package, this function creates candidate models with multiple regularization multiplicator combinations, entity classes, and sets of environmental predictors. For each combination, Maxent builds a model with the occurrences set points and another model with the training occurrence data [32]. The combination of features classes was linear (L), quadratic (Q), product (P), threshold (T), hinge (H), and for multiplicators, regularization were 0.5, 1, 2, 3, and 4. Each model quantifies the environmental suitability for the species of interest, as a function of the variables studied.

 

Evaluation of ecological niche models

Candidate models were evaluated with the function kuenm_ceval of the ‘Kuenm’ package in Rstudio® ver. 3.3, this evaluation selects one or two best models, categorized by their prediction capacity and complexity, selecting those models with statistical significance [33]. Partial roc was used to choose models that are significantly better than randomly null expectative [33]. Then, the omission rate criterion was applied to these models. In the end, those significative, low omission rates, and delta AICc with lower values of 2, were selected [32].

RESULTS AND DISCUSSION

Models’ quality

Ecological niche modeling for invasive species studies “use occurrence records of the species in one region to calibrate models, and to then project those models into other regions, where the species may or may not be invasive at present” [28]. For supporting the hypothesis of environmental suitability, we selected models with statistical robustness (Table 2), with omission rates ≤ 5%, and delta AICc values ≤ 2 [28, 32].

 

 

Table 2. Tomicus (Coleoptera: Curculionidae: Scolytinae) species best models evaluated statistically and used for modeling their ecological niche.

Species

Model

Partial

ROC

Omission

the rate at 5%

AICc

Delta

AICc

W_AICc

Number of parameters

T. minor

M_4_F_pt_Set_02

0.02

0.049

17450.033

0

0.99996812

16

T. piniperda

M_1_F_lqpt_Set_01

0

0.024

32079.290

0

0.38921386

96

T. destruens

M_1_F_lq_Set_01

0

0.029

2787.7524

0

0.99934317

10

 

 

Bioclimatic variables for modeling ecological niches

Models for the species studied here were determined by a particular set of bioclimatic variables (Table 3), reflecting different environmental requirements, related to their natural geographic distribution. In terms of world biogeographic regions [34], T. destruens has an Oriental region distribution, expanding to the Palearctic and until the Saharo-Arabian transition zone, their southernmost distribution habitat [11]. Both T. piniperda and T. minor follow a similar distribution pattern, from the Chinese transition zone, along with to the Oriental region for a natural wide expansion through the Palearctic region [11]. However, T. piniperda needs a wider set of bioclimatic variables in comparison to T. minor.

Ecological models were defined mainly by three-four bioclimatic variables, contributing with 71.9, 97.1, 78.3 % for T. destruens, T. minor, and T. piniperda, respectively (Table 3). For T. destruens, variables related to precipitation and temperature seem to define their ecological niche: bio14 (Precipitation of the driest month, indicates the month with the lowest cumulative precipitation total in their origin site), bio15 (precipitation seasonality), and bio2 (annual mean diurnal range). By another hand, T. minor showed more precipitation variables for defining their ecological niche, with bio1 (annual mean temperature), bio 7 (Annual temperature range), and bio 16 (Precipitation of wettest quarter) as the main bioclimatic variables. Tomicus piniperda was defined by bio1 (annual mean temperature), bio5 (max temperature of the warmest month), and bio 4 (temperature seasonality, a measure of temperature changes annually).

 

 

Table 3. Bioclimatic variables were used in the final modeling of the ecological niche of three Tomicus species (Coleoptera: Curculionidae: Scolytinae) species.

T. destruens

T. minor

T. piniperda

Bioclimatic variable

Percent contribution

Bioclimatic variable

Percent contribution

Bioclimatic variable

Percent contribution

Bio 14

30.9

Bio 1

49.4

Bio 1

19.8

Bio 15

22.0

Bio 7

33.9

Bio 5

28.6

Bio 2

19.0

Bio 16

13.8

Bio 4

14.6

Bio 4

15.0

Bio 15

2.9

Bio 2

15.3

Bio 1

5.2

 

 

Bio 3

9.8

Bio 5

3.5

 

 

Bio 12

7.0

Bio 12

3.4

 

 

Bio 15

4.8

Bio 3

1.0

 

 

 

 

 

 

Environmental suitability

The environmental availability calculated varied among the three species studied and varied as an effect of the software configuration. Maxent has three distinct options for extrapolation: free extrapolation, no extrapolation, and extrapolation with clamping. Here we did not use the free extrapolation option because “it can project an unlimited extrapolation into the study area”. Under the no extrapolation setting, the response is set to zero if the environments in transfer areas are extremer than those in areas across which the models were calibrated” [32]. In this sense, only T. destruens and T. minor found environmental availability in Mexico, while for T. piniperda it was not possible to extrapolate environmental information. This does not necessarily mean that Mexico did not have environmental suitability for this species, probably the increase of geographical data in the future could improve the model resolution.

With the extrapolation and clamping setting, the response in areas with environments distinct from those in the calibration area is clamped to levels presented at the periphery of the calibration region in environmental space [32]. Under this premise, all the three species found in Mexico's environmental conditions would allow them a probable temporary permanence.

According to the no extrapolation setting in Maxent, T. destruens model shows an optime environmental suitability in a limited area in northeastern Mexico, in small and dispersed areas in the Altiplano Norte biogeographic province, and an isolated area in the Tamaulipeca biogeographic province (Figure 1a). Medium to lower environmental suitability was projected in the biogeographic provinces lasted mentioned, but mainly in the Tamaulipeca (Figure 1a).

 

a)

b)

c)

Figure 1. Ecological niche model of three Tomicus species (Coleoptera: Curculionidae: Scolytinae) projected on the Mexican biogeographic provinces [35], using Maxent no Extrapolation setting. a) Tomicus destruens, b) T. minor and c) T. piniperda. 1. Baja California, 2. California, 3. Sonorense, 4. Sierra Madre Occidental, 5. Altiplano Norte, 6. Tamaulipeca, 7. Golfo de México, 8. Sierra Madre Oriental, 9. Altiplano Sur, 10. Costa del Pacífico, 11. Eje Volcánico, 12. Depresión del Balsas, 13. Sierra Madre del Sur, 14. Soconusco, 15. Los Altos de Chiapas, 16. Peten, 17. Yucatán, 18. Del Cabo, 19. Oaxaca.

 

Tomicus minor showed the most surface in Mexico with environmental suitability in the present study (Figure 1b), with areas projected along with the biogeographic province Baja California, all the biogeographic province of California, northwestern of Sonorense, central areas of Altiplano Norte and Altiplano Sur, northwestern of Tamaulipeca and small areas in eastern Eje Volcánico. Minor suitability was calculated in the biogeographical provinces of Sierra Madre Occidental, Altiplano Norte and Altiplano Sur, Eje Volcánico, Sierra Madre Oriental, Sierra Madre del Sur, Sonorense and northern Golfo de México.

For T. piniperda it was not possible to calculate environmental suitability for the country (Figure 1c).

By expanding the model exploration options with the extropolation-clamping setting, the environmental availability of T. destruens expands enormously in the central region of the country (Figure 2a). Environmetal suitability was projected now into the biogeographic provinces of Baja California, Los Cabos, southern Sonorense, along Costa del Pacífico, southern Sierra Madre Occidental, most of the Eje Volcánico, Altiplano Sur, Depresión del Balsas, Sierra Madre del Sur, eastern Altiplano Norte, isolated areas in the Tamaulipeca and Golfo de México, most of the Yucatán and Peten, Soconusco and Altos de Chiapas.

The projection for T. minor was quite similar in both model configuration designs (Figures 1b and 2b), but with the following changes: expanded their suitability into full covering the Baja California biogeographic province. By another hand, a contraction in the surface projected in the Altiplano Norte, Altiplano Sur, and Tamaulipeca biogeographic provinces. Areas with environmental suitability were calculated in northern Golfo de México and conserved areas in the Eje Volcánico. In the Sonerense biogeographic province, the regions calculated were reshaped, contracting, and stretching at the eastern of the province, and increasing in the limits with the California biogeographic province (Figures 2a and 2b).

 

a)

b)

c)

Figure 2. Ecological niche model of three Tomicus species (Coleoptera: Curculionidae: Scolytinae) projected on the Mexican biogeographic provinces [35], using Maxent Extrapolation-Clamping setting. a) Tomicus destruens, b) T. minor and c) T. piniperda. 1. Baja California, 2. California, 3. Sonorense, 4. Sierra Madre Occidental, 5. Altiplano Norte, 6. Tamaulipeca, 7. Golfo de México, 8. Sierra Madre Oriental, 9. Altiplano Sur, 10. Costa del Pacífico, 11. Eje Volcánico, 12. Depresión del Balsas, 13. Sierra Madre del Sur, 14. Soconusco, 15. Los Altos de Chiapas, 16. Peten, 17. Yucatán, 18. Del Cabo, 19. Oaxaca.

 

Environmental suitability for T. piniperda with Extrapolation plus Clamping setting changes drastically its projection into Mexico: from zero (Figure 1c) to cover biogeographic provinces northern the country and some central and southern biogeographic provinces (Figure 2c). Most of the Altiplano Norte, Baja California, California, and Los Cabos; and Sonorense are now with environmental suitability. Other areas were calculated western Tamaulipeca, disperse spots in Sierra Madre Occidental, northern Altiplano Sur, Sierra Madre Oriental, Eje Volcánico, Sierra Madre del Sur, Oaxaca, with projection in Soconusco and Altos de Chiapas biogeographic provinces (Figure 2c).

The great variation showed with the Extrapolation plus Clamping setting, increasing drastically from zero to calculate wider areas for T. piniperda; and expanding the environmental suitability several times for T. destruens indicated to us be careful with interpretation derived from those models. As to be noted before, extrapolation and clamping settings take into account the environmental conditions in the calibration area periphery, and if two geographical areas are so contrasting environmental conditions so distant to the calibration area are given [28, 32]. For this reason, we considered the results obtained from the No extrapolation as more adequate and this will be used in the rest of the manuscript.

 

Ecological niche and Pinus distribution in Mexico

Although T. destruens is projected punctually in northeastern Mexico, this is probably no concern for the Mexican Pinus diversity (Figure 3a). Tamaulipeca biogeographic province did not show abundant Pinus records. Pinus diversity and abundance increase gradually in the Altiplano Norte-Tamaulipeca limits, where scarce environmental suitability is calculated. Tomicus destruens is a univoltine species and choices Pinus from the Mediterranean ecosystem, as P. brutia Ten., P. canariensis C. Sm., P. halepensis Miller, P. nigra J.F. Arnold, P. pinaster Aiton, P. pinea L., and P. radiata D.Don [11, 20]. The number and amount of monoterpenes have been cited as the main factor in the host selection for this scolytine in its natural distribution range [19]. This opens an opportunity to explore the composition, concentration, and distribution of monoterpenes in Pinus from Mexico, as a preventive strategy to known potential or susceptible host species.

 

a)