A conceptual framework to deal with outliers in ecology

Research on ecology commonly involves the need to face datasets that contain extreme or unusual observations. The presence of outliers during data analysis has been of concern for researchers generating a lot of discussion on different methods and strategies on how to deal with them and became a recurrent issue of interest in debate forums. Systematic elimination or data transformation could lead to ignore important ecological processes and draw wrong conclusions. The importance of coping with extreme observations during data analysis in ecology becomes clear in the context of relevant environmental aspects such as impact assessment, pest control, and biodiversity conservation. In those contexts, misinterpretation of results due to an incorrect processing of outliers may difficult decision making or even lead to failing to adopt the best management program. In this work, I summarized different approaches to deal with extreme observations such as outlier labeling, accommodation, and identification, using calculation and visualization methods, and provide a conceptual workflow as a general overview for data analysis.Jacinto Benhadi-Marín is grateful to the Portuguese Foundation of Science and Technology for financial support through the Ph.D. grant SFRH/BD/97248/2013 and has no conflict of interest to disclose.info:eu-repo/semantics/publishedVersio

Potential areas of spread of Trioza erytreae over mainland Portugal and Spain

Trioza erytreae is one natural psyllid vector of Candidatus liberibacter, the causal agent of the citrus greening disease (HLB). Since its introduction in 2014 into the Iberian Peninsula, T. erytreae was able to spread continuously toward southern coastal regions of Portugal and northern coastal regions of the Cantabric sea in Spain. Identifying key areas of potential colonization by the psyllid vector is crucial to anticipate derived problems of establishing the disease. This work aimed to find potential areas that could be colonized by T. erytreae throughout the Iberian Peninsula using 1 km spatial data resolution, a physical barrier, long-distance dispersal events (LDEs), and 30 years of simulation. The bioclimatic suitability of Citrus spp. was used as a surrogate of its spatial distribution and a measure of habitat invasibility. Two localities, one in Portugal and one in Spain, were considered as initial points of the spread of T. erytreae. Four spread scenarios were initially simulated, corresponding to very low, low, medium, and high spread. An altitude of 400 m was included in the model as a physical barrier, and cells up to 500 km apart were allowed to be colonized due to LDEs. In this work, three key risk areas were identified, the citrus-growing areas of Setúbal (Portugal) and Huelva (Spain), and the potential corridors that may connect Guipúzcoa, where T. erytreae is already present, with the Ebro valley (Spain). Future modeling and simulation studies should include biological constraints such as the effect of parasitoids on the population of T. erytreae (e.g., Tamarixia dryi) and other barriers or corridors.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal), for financial support through national funds FCT/MCTES to CIMO (UIDB/00690/2020) and to the project PRE-HLB-Preventing HLB epidemics for ensuring citrus survival in Europe (H2020-SFS-2018–2 Topic SFS-05–2018-2019–2020, proj. No. 817526).info:eu-repo/semantics/publishedVersio

A model to predict the expansion of trioza erytreae throughout the iberian peninsula using a pest risk analysis approach

Assessing the potential of spread of an introduced crop pest in a new country is crucial to anticipating its effects on crop production and deriving phytosanitary management toward reducing potential negative effects. Citrus production represents a key agricultural activity throughout the Mediterranean basin. The African citrus psyllid Trioza erytreae (del Guercio, 1918) (Hemiptera: Triozidae) is a natural vector of Candidatus liberibacter spp., the causal agent of the harmful disease huanglongbing (HLB) or “citrus greening disease”. In continental Europe, T. erytreae was detected for the first time in northwestern Spain in 2014. Pest risk analysis (PRA) approaches, such as modeling, consider both time and space components to predict the potential distribution of pests in a given region. In this work, we aim to parameterize a model able to predict the expected spread of T. erytreae in the Iberian Peninsula using three types of PRA models. The kernel model with two hypothetical entry points accurately predicted the distribution of T. erytreae with respect to latitude. This model should be further refined and validated to support decision-makers in the adoption of timely and successful management and regulatory measures against the spread of T. erytreae to other citrus-producing areas in Europe.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal), for financial support through national funds FCT/MCTES to CIMO (UIDB/00690/2020) and to the project PRE-HLB—Preventing HLB epidemics for ensuring citrus survival in Europe (H2020-SFS-2018-2 Topic SFS-05-2018-2019-2020, proj. No. 817526).info:eu-repo/semantics/publishedVersio

Web architecture affects the functional response of the space web-builder Kochiura aulica against Trioza erytreae in the laboratory

The “citrus greening disease” or huanglongbing (HLB) is caused by the Gram-negative bacteria Candidatus Liberibacter spp. One vector of HLB, the African citrus psyllid Trioza erytreae (del Guercio, 1918), was recorded for the first time in 2014, in mainland Spain, and since then, it has spread throughout the Iberian Peninsula. Spiders could be natural enemies of T. erytreae. In this work, we assessed the potential of a model spider species, selected according to the most abundant guild in the field, as a natural enemy of T. erytreae. Theridiidae was the most successful family, capturing adults of T. erytreae in the field. Kochiura aulica (Theridiidae) was selected as a model for functional response assays in the laboratory. The effect of web-building plasticity on the functional response of K. aulica was investigated using two types of arena. The spiders developed tubular-like or branch-like webs according to the spatial constraints. The web architecture significantly shifted the trapping efficiency of K. aulica. Functional responses for tubular and branch webs were both Type-II, but more psyllid prey were captured and killed in the tubular webs than in branch webs. In addition, significantly more psyllids survived in branch-like webs. Our results suggest that web architecture is a key factor driving the number of captured adults of the psyllid. Space web builders could be successful natural enemies of T. erytreae, although further research is needed to clarify the influence of web-building plasticity on the functional response and trapping efficiency of spiders.The authors are grateful to the European Union grant, programme H2020 entitled: PREHLB: Preventing HLB epidemics for ensuring citrus survival in Europe. H2020-SFS-2018–2 Topic SFS-05–2018-2019–2020—new and emerging risks to plant health (Project nº 817526)—as well as to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020) and Associated Laboratory SusTEC (LA/P/0007/2020).info:eu-repo/semantics/publishedVersio

Effects of kaolin particle films on the life span of an orb-weaver spider

Araniella cucurbitina (Araneae: Araneidae) is a widespread orb-weaver spider commonly found in agroecosystems. Mineral particle films such as kaolin, due to their protective or anti-feeding action, can represent an alternative to pesticides, especially in organic farming systems, but little is known about its effects on A. cucurbitina. Therefore, we tested the effect of kaolin sprays on the life span of A. cucurbitina under laboratory conditions. Four treatments were tested encompassing different exposure routes. Thus, kaolin sprays were applied on (i) the surface, (ii) the prey (fly), (iii) the spider and (iv) both spider & prey. A control group was tested with water in each treatment. Results showed that sprays of kaolin significantly affected the survival of A. curcubitina when applications were done on the surface and on both spider & prey registering a reduction of 48% and 56%, respectively. Spiders in control obtained higher probability of reaching alive at the end of the assay than those treated with kaolin. Differences observed can be explained by the feeding behavior of the species and may depend on the consumption of the web by the spider and the ratio spider/fly for body size.This study was financially supported by FEDER Funds throughout Programa Operacional Factores de Competitividade e COMPETE and National Funds throughout FCT e Fundação para a Ciência e Tecnologia, within the project EXCL/AGR-PRO/0591/2012: Olive crop protection in sustainable production under global climatic changes: linking ecological infrastructures to ecosystem functions (Grant number: 130390)

Functional response of Chrysoperla carnea (Neuroptera: Chrysopidae) Larvae on Saissetia oleae (Olivier) (Hemiptera: Coccidae): implications for biological control

Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) is a voracious predator of soft-bodied insects such as juveniles of scale insects and the black scale Saissetia oleae (Olivier) (Hemiptera: Coccidae) is an important pest of several crops, such as the olive tree. However, the predatory effciency of C. carnea on S. oleae has been unstudied yet. The present work aimed to study the functional response of larvae of C. carnea fed on S. oleae nymphs. In a controlled laboratory environment, increasing densities of S. oleae second and third nymph stages were offered to newly emerged specimens of the three larvae instars of C. carnea. After 24 h, the number of killed S. oleae was recorded and the functional response of C. carnea was assessed. The three larval stages of C. carnea displayed a type-II functional response, i.e., killed prey increased with higher S. oleae densities up to a maximum limited by the handling time. The attack rate did not significantly differ among the three instars while the maximum attack rate was significantly higher for the third instar. The handling time of the first larval instar of C. carnea was higher than that of the third instar. Our results demonstrated that S. oleae could act as a food resource for all larval stages of C. carnea. Furthermore, the third larval stage of the predator was the most effcient in reducing S. oleae densities. These results suggest that C. carnea larvae could contribute to S. oleae control in sustainable agriculture.This research was funded by Foundation for Science and Technology (FCT, Portugal), grant number UIDB/00690/2020. Abdelkader Meni Mahzoum was supported by Erasmus+ Programme, Mare Nostrum Project with reference 2016-1-PT01-KA107-022660. María Villa thanks FCT for the PostDoc grant SFRH/BPD/119487/2016info:eu-repo/semantics/publishedVersio

Host plant preference of Trioza erytreae on lemon and bitter orange plants

Trioza erytreae, the African citrus psyllid, is a vector of Candidatus Liberibacter spp., the causal agent of the citrus greening disease or Huanglongbing (HLB). The spread of the vector throughout the Iberian Peninsula has been continuous since its introduction in mainland Spain in 2014. The patterns of host preference and feeding behaviour largely depend on olfactory cues. Understanding these patterns is crucial to prevent further dispersion and develop management measures against the pest. In this work, a series of settlement, olfactometric, probing, and feeding experiments were conducted to assess the host preference of T. erytreae for lemon or bitter orange plants. The settlement experiment provided evidence on the preference of both sexes of T. erytreae for lemon plants, whereas males did not show any significant choice pattern in the case of the olfactometric assays. Forty EPG variables were analysed to describe and compare the probing and feeding behaviour of T. erytreae on lemon and bitter orange plants. The EPG variables indicated that T. erytreae has some difficulties in accepting the phloem of bitter orange plants. This suggests that lemon plants would be a better source for the acquisition of Candidatus Liberibacter asiaticus (CLas) by T. erytreae since the psyllid spends much longer periods feeding from the phloem on lemon than on bitter orange.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. The authors are grateful to the European Union grant, programme H2020 entitled: PRE-HLB: Preventing HLB epidemics for ensuring citrus survival in Europe. H2020- SFS-2018–2 Topic SFS-05–2018-2019–2020—new and emerging risks to plant health (Project nº 817526) as well as to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020).info:eu-repo/semantics/publishedVersio

Functional response of Chrysoperla carnea (Neuroptera: Chrysopidae) to Saissetia oleae (Olivier) (Hemiptera: Coccidae)

Lacewings are common biocontrol agents against a wide range of agricultural pests.These predators are highly voracious against soft-bodied preys such as juveniles of scale insects. In this context, the present work aims to study the use of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) as biological control agent against Saissetia oleae (Olivier) (Hemiptera: Coccidae). For that, we studied the functional response of the larval instars of C. carnea to nymphs of S. oleae. Increasing densities (3, 5, 10, 15, 25 and 40) of S. oleae nymphs were offered to the three larval stages of C. carnea in a controlled laboratory environment. After 24 hours, the number of S. oleae consumed by C. carnea larva was recorded and the functional response calculated. The three larval stages of C. carnea displayed a type II functional response behavior. Prey consumption by C. carnea larvae increased with high S. oleae densities. Moreover, younger larvae showed a lower predation rate in comparison with the older ones. The search rate and handling time of the third instar larvae were lower than those of the younger larval instars, and the simulated max. attack rate of the third instar larvae was higher than those of the first and second instar larvae. Our results suggest that all larval stages of C. carnea could be important in S. oleae biological control in olive orchards, although the third larval stage of the predator was more efficient in reducing S. oleae densities than first and second C. carnea larval instars.info:eu-repo/semantics/publishedVersio

Distribution of Bactrocera oleae (Rossi, 1790) throughout the Iberian Peninsula based on a maximum entropy modelling approach

The Iberian Peninsula (Portugal and Spain) is a great production area of olives. The fruit production can be severely affected by the olive fruit fly, Bactrocera oleae (Rossi, 1790) (Diptera). Detailed geographical distribution maps of key pests, such as B. oleae, are essential for their integrated management. Although different sources reporting the occurrence of B. oleae are available for sub-regions of Portugal and Spain, the data available are dispersed and centralisation of this information considering the Iberian Peninsula as a faunistic geographical unit is currently lacking. In this work, we built two distribution maps of B. oleae throughout the Iberian Peninsula, one based on occurrence sites and another based on its bioclimatic habitat suitability. After modelling the bioclimatic suitability of B. oleae using a maximum entropy model, three potential distribution areas beyond the previously known occurrence range of the olive fruit fly were identified corresponding to the autonomous community of Galicia (Spain), the Spanish and Portuguese sides of the International Douro Natural Park, and the autonomous community of Castilla y León (Spain). Interestingly, each region houses nowadays autochthonous olive cultivars. The drivers that most contributed to the model were the precipitation of the coldest quarter and the precipitation of driest month which agrees with the B. oleae bioecology. Although our approach is not fully-comprehensive in terms of occurrence sites, we show how a maxent modelling approach can be useful to identify potential risk areas of B. oleae occurrence throughout a target geographical extent such as the Iberian Peninsula.info:eu-repo/semantics/publishedVersio

Functional diversity of epigeal spiders in the olive grove agroecosystem in northeastern Portugal: a comparison between crop and surrounding semi‐natural habitats

The olive grove agroecosystem (Olea europaea L., Oleaceae) is very important in terms of economy and culture throughout the Mediterranean region. In Trás-os- Montes (Portugal), olive groves are commonly surrounded by semi-natural areas consisting of Mediterranean shrublands. Understanding the role of potential predators of olive pests is crucial to enhancing biological control in sustainable agriculture. This study aimed to investigate the community structure of ground-inhabiting spiders (Arachnida: Araneae) in the olive grove and their surrounding shrublands in Trás-os- Montes. We found that the community of spiders was dominated by ground hunters such as Lycosidae and Gnaphosidae. Lycosidae were more abundant in olive groves than in surrounding shrublands in 2015 only, whereas Gnaphosidae were more abundant in olive groves in both years of the study (2015 and 2016). Hence, the two habitats displayed a low complementarity of spider families. The Mediterranean shrubland areas could act as a reservoir and refuge for potential pest biocontrol agents. Conservation of surrounding semi-natural areas may contribute to the natural limitation of pests exerted by spiders in the olive grove agroecosystem. Nevertheless, further long-time and species-level studies are needed to provide insights into the role of spiders as natural enemies.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal), for financial support through national funds to the project ‘OLIVESIM –Managing ecosystem services in olive groves using advanced landscape agent-based models’ (PTDC/ASP-PLA/30003/2017) and for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020) and CIMO –LA SusTEC (LA/P/0007/2020).info:eu-repo/semantics/publishedVersio