Abstract
This study investigates morpho-geometric variations in wing conformations among honeybee (Apis mellifera L.) populations in Algeria, focusing on Apis mellifera intermissa in the northern zone. It addresses the threats posed by human beekeeping practices and hybridization. The analysis involves collecting and digitizing 445 honeybee specimens from nine localities in northern Algeria: Batna, Blida, Constantine, Cheffa, Jijel, Mila, Setif, Skikda, and Tipaza. Statistical assessments reveal significant wing anatomy variations across these zones. Principal Component Analysis identifies distinct shapes within populations, with notable differences in specific regions. Discriminant Analysis classifies samples into three groups, showcasing the model’s effectiveness. The Mahalanobis D distances provides insights into population similarities and differences, emphasizing the potential of morpho-geometric analysis in differentiating bee populations. The study concludes by highlighting the significance of size-independent data, offering recommendations for capturing honeybee diversity in different climatic zones of northern Algeria. This research advances our understanding of honeybee morphology in relation to environmental dynamics, providing valuable insights for preserving indigenous bee races and exploring biodiversity.
Keywords:
Apis mellifera; characterization; geometric morphometrics; landmarks; shape; wing; conservation; diversity 1. Introduction
Different subspecies of honeybee are present in Algeria [1], with Apis mellifera intermissa [2] residing in the north. However, this natural heritage faces an escalating threat due to human beekeeping practices spreading at an alarming pace [3]. The pursuit of high economic performance in bee colonies, coupled with desirable behavioral characteristics, have induced significant changes that jeopardize regional races and ecotypes through hybridization [4,5]. Currently beekeepers and biologists are engaged in a dual effort to sustainably preserve the two indigenous subspecies and explore biodiversity thoroughly. This characterization involves the utilization of powerful morphometry and molecular genetics methods. Wing venation may exhibit subtler patterns of variation oppositely to traditional observation methods. Geometric morphometrics proves promising in quantifying variation in complex morphological traits, particularly in wings due to their high heritability of shape [6,7]. Our objective is to assess the level of similarity among structures deduced from the forewings of domestic honeybee specimens (particularly those of females) in different parts of the country. This assessment is based on a well-established theory of shape [8] and adheres to the protocol outlined by Barour in 2012 [9,10,11]. This methodology employs the coordinates of 19 points, called landmarks, which are superimposed by translation, scaling, and rotation. After superposition, the landmark configurations differ only in shape and can be analyzed by multivariate statistical methods [11]. This approach has successfully discriminated patterns of insect wing venation among various species and even within species. Geometric morphometrics holds the potential to assess the extent of phenotypic divergence among discrete insect populations by quantifying variation in this highly conserved trait. Our aim with this paper is to provide recommendations and detailed descriptions of the geometric morphometric method for a more coherent capture of the diversity of honeybees in different climatic zones of northern Algeria.
2. Materials and Methods
Geo-Morphometry Approach
The investigation involved the random sampling of worker honeybees (30 per colony, totaling 445) during expeditions to nine distinct locations in northern Algeria, each characterized by different altitudes (Table 1), conducted between March and May 2021. The collected samples are preserved in 50 mL vials with 90° absolute ethanol at a very low temperature (−20 °C) until laboratory processing [12]. Subsequently, the right forewing of each specimen is dissected and digitized using a binocular microscope (10- to 100-fold magnification) equipped with a camera and Image Focus 4.0 image analyzer software.
Table 1.
The geographical and climatic situation of sample collection sites.
To discern conformational differences in shape parameters, including size, we aligned a set of 19 homologous wing venation landmarks of type I [9] based on the definitions of Bookstein in 1991 [10,11,12,13]. This alignment process utilizes TPS software: TpsUtil32 version 1.76 and TpsDig232 version 1.31 [14], alongside dedicated software tools R version 4.1.0 (i386) [15] and Morpho J version 1.06 [16], exclusively designed for the modeling and visualization of honeybee wing structures.
3. Results
Global Trends in Wing Shape
Principal Component Analysis (PCA) identified significant variations in wing anatomy across geographic zones. Wings from Jijel, Sétif, Skikda, Tipaza, and Mila showed a complex structure with variability in the upper wing veins. Batna, Bejaia, Blida, and Constantine had wings with branched veins in the central part and contractions in the upper sections. Cheffa wings were elongated with slender veins and less developed anatomy (Figure 1).
Figure 1.
Distribution of wing deformations along the two axes of PCA.
Examining deformations with variations in inertia values, the first PCA component (PC1) controls contractions and relaxations in the upper wing veins. The second component (PC2) governs the central wing veins and the wing’s concavity or convexity. The third component (PC3) is influenced by itinerary points, binding points between veins, and histological boundaries. The conditioning table (Figure 2) visualizes deformations as variations unfold within the inertia values indicated by PCA.
Figure 2.
Conditioning and wing deformation according to the two axes of PCA.
The Discriminant Analysis revealed that the first two dimensions (Axis 1 and Axis 2) accounted for 59.45% of the inertia, identifying three distinct groups. Group 1 included samples from Sétif, Mila, Tipaza, and Skikda. Group 2 comprised specimens from Bejaia, Constantine, Cheffa, and Blida, while Group 3 exclusively featured specimens from Batna (Figure 3).
Figure 3.
Classification of bee groups according to the LDA model.
To gain further insight into the similarity and dissimilarity rates between population samples, Mahalanobis D distances [17] were computed. Overall, populations did not exhibit significant differences in geometric shapes, except for specific points. The most notable statistical dissimilarity was between the Batna and Jijel regions, with a distance score of 4.28. Conversely, the closest populations were Mila and Skikda, with a score of 1.77 (Table 2).
Table 2.
Results for Mahalanobis distances between groups.
4. Discussion
The morpho-geometric analysis of wing conformations emerges as a dependable tool for discriminating among bee subspecies, potentially surpassing classical morphometry. In 2011, Kandemir et al. highlighted the utility of morpho-geometric analysis in studying the biodiversity of honeybees through wing venation patterns [18], while Rattanawannee et al. already proposed wing morpho-geometry as a preliminary analysis step, reserving molecular analysis for cases of uncertainty in 2010 [19]. The significance of employing size-independent data to characterize biogeographic races of Apis mellifera is emphasized by the insights from the research of Ruttner and Barour [20,21]. Our study incorporated a range of univariate and multivariate analyses, with Principal Component Analysis aimed at identifying distinct shapes within the population. Specifically, the regions of Jijel, Sétif, Skikda, Tipaza, and Mila exhibited a more intricate wing anatomy compared to other regions, with notable variability in the upper wing veins, inclining upwards on lateral sides. Remarkably, the Cheffa zone showcased a distinctively elongated wing shape, while bees from Batna, Bejaia, Blida, and Constantine exhibited branched veins in the central part. The classification model indicated the greatest statistical dissimilarity between the Mila and Skikda regions (score: 1.77), whereas the closest populations were Batna and Jijel (distance score: 4.28). Overall, the populations did not exhibit significant differences in geometric shapes. The morpho-geometric results signify the potential for distinguishing regional bee populations based on the wing venation conformations of worker bees, an observation not previously reported [9].
This study conclusively delved into the realm of morpho-geometric analysis as a powerful tool for discerning intricate variations in wing conformations among regional populations of Apis mellifera. Supported by appropriate statistical analyses, the investigation illuminated significant variations in the shape and size of the parameters under scrutiny. These variations bear relevance to a multitude of biological, ecological, and social factors, including the local vegetation and climate, the diverse ages of bees, genetic heterogeneity, and the tolerance of foreign bees to accessing different hives. Integrating these findings enhances our understanding of the intricate relationships between honeybee morphology and environmental dynamics. The observed variations underscore the complex interplay that shapes bee populations and highlights the dynamic factors contributing to morphological diversity. This study not only advances the methodology of morpho-geometric analysis but also enriches our broader comprehension of the nuanced interdependencies governing honeybee populations. As we navigate the intricate landscape of bee biodiversity, the insights gained from this research pave the way for more nuanced and context-specific approaches to studying Algerian bee subspecies in their natural biotope.
Author Contributions
The author R.K. contributed to data collection and drafted the first version of the article. R.M.M. carried out the statistical analyses. S.B.S.G. contributed to the critical revision of the manuscript. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
The data presented in this study are available upon request from the corresponding author.
Conflicts of Interest
The authors declare no conflict of interest.
References
- Linnæus, C. Systema Naturae per Regna Tria Naturae, Secundum Classes, Ordines, Genera, Species, cum Characteribus, Differentiis, Synonymis, Locis; Laurentius Salvius: Stockholm, Sweden, 1758; Volume I-II, pp. 1–824. [Google Scholar]
- Buttel-Reepen, H.V. Apistica Beitrage zur Systematik, Biologie, sowie zurgeschichtlichen und geographischen Verbreitung der Honigbiene (Apis mellifera L.), ihrer Varietaten und der ilbrigen Apis-Arten. Mitteilungen aus dem Zoologischen Museum im Berlin 1906, 3, 121–196. [Google Scholar]
- Meixner, M.D.; Pinto, M.A.; Bouga, M.; Kryger, P.; Ivanova, E.; Fuchs, S. Standard methods for characterising subspecies and ecotypes of Apis mellifera. J. Apic. Res. 2013, 52, 1–28. [Google Scholar] [CrossRef]
- De La Rúa, P.; Jaffé, R.; Dall’olio, R.; Muñoz, I.; Serrano, J. Biodiversity, conservation and current threats to European honeybees. Apidologie 2009, 40, 263–284. [Google Scholar] [CrossRef]
- Meixner, M.D.; Costa, C.; Kryger, P.; Hatjina, F.; Bouga, M.; Ivanova, E.; Büchler, R. Conserving diversity and vitality for honey bee breeding. J. Apic. Res. 2010, 49, 85–92. [Google Scholar] [CrossRef]
- Mitteroecker, P.; Gunz, P. Advances in geometric Morphometrics. Evol. Biol. 2009, 36, 235–247. [Google Scholar] [CrossRef]
- Rohlf, J.F.; Marcus, L.F. A revolution morphometrics. Trends Ecol. Evol. 1993, 8, 129–132. [Google Scholar] [CrossRef] [PubMed]
- Kendall, D.G.; Barden, D.; Carne, T.K.; Le, H. Shape and Shape Theory; John Wiley & Sons: Chichester, UK, 1999. [Google Scholar]
- Barour, C. Analyse de la Biodiversité des Populations d′Abeilles Mellifères Apis mellifera intermissa (Buttel-Reepen, 1906) (Hymenoptera: Apidea) dans le Nord Algérien: Morphométrie Moderne Basée sur la Configuration des Points-Repères (Landmarks); Université Badji Moktar de Annaba (UBMA): Annaba, Algeria, 2012. [Google Scholar]
- Bookstein, F.L. Morphometric Tools for Land-Mark Data: Geometry and Biology; Cambridge University Press: Cambridge, UK, 1991. [Google Scholar]
- Zelditch, M.L.; Swiderski, D.L.; Sheets, H.D.; Fink, W.L. Geometric Morphometrics for Biologists: Aprimer; Elsevier Academic Presss: London, UK, 2004. [Google Scholar]
- Adjlane, N.; Doumandji, S.E.; Haddad, N. Situation de l’apiculture en Algérie: Facteurs menaçant la survie des colonies d’abeilles locales Apis mellifera intermissa. Cah. Agric. 2012, 21, 235–241. [Google Scholar] [CrossRef]
- Barour, C.; Tahar, A.; Baylac, M. Forewing shape variation in Algerian honey bee populations of Apis mellifera intermissa (Buttel-Reepen, 1906) (Hymenoptera: Apidae): A landmark-based geometric morphometrics analysis. Afr. Entomol. 2011, 19, 11–22. [Google Scholar] [CrossRef]
- Rohlf, F.J. TpsDig Version 2.12 (Tps_Digitize); Stony Brook; State University of New York: New York, NY, USA, 2008. [Google Scholar]
- Ihaka, R.; Gentleman, R. A language for data analysis graphics. Comput. Graph. Stat. 1996, 5, 299–314. [Google Scholar] [CrossRef]
- Klingenberg, C.P. MorphoJ: An integrated software package for geometric morphometrics. Mol. Ecol. Resour. 2011, 11, 353–357. [Google Scholar] [CrossRef] [PubMed]
- Mardia, K.V.; Kent, J.T.; Bibby, J.M. Multivariate Analysis; Academic Press: London, UK, 1979. [Google Scholar]
- Kandemir, İ.; Özkan, A.; Fuchs, S. Reevaluation of honeybee (Apismellifera) microtaxonomy: A geometric morphometric approach. Apidologie 2011, 42, 618–627. [Google Scholar] [CrossRef]
- Rattanawannee, A.; Chanchao, C.; Wongsiri, S. Gender and Species Identification of Four Native Honey Bees (Apidae: Apis) in Thailand Based on Wing Morphometic Analysis. Ann. Entomol. Soc. Am. 2010, 103, 965–970. [Google Scholar] [CrossRef]
- Ruttner, F.; Tassencourt, L.; Louveaux, J. Biometrical statistical analysis of the geographic variability of Apis mellifera L. LI Material and methods. Apidologie 1978, 9, 363–381. [Google Scholar] [CrossRef]
- Barour, C.; Tahar, A.; Radloff, S.; Hepburn, H. Multivariate analysis of honey bees, Apis mellifera Linnaeus (Hymenoptera: Apidae) of the northeastern and southern regions of Algeria. Afr. Entomol. 2005, 13, 17–23. [Google Scholar]
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |
© 2024 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).