The honey bees of Ethiopia represent a new subspecies of Apis mellifera–Apis mellifera simensis n. ssp. Marina Meixner, Messele Leta, Nikolaus Koeniger, Stefan Fuchs

To cite this version: Marina Meixner, Messele Leta, Nikolaus Koeniger, Stefan Fuchs. The honey bees of Ethiopia represent a new subspecies of Apis mellifera–Apis mellifera simensis n. ssp.. Apidologie, Springer Verlag, 2011, 42 (3), pp.425-437. .

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Original article

Apidologie (2011) 42:425–437 * INRA, DIB-AGIB and Springer Science+Business Media B.V., 2011 DOI: 10.1007/s13592-011-0007-y

The honey bees of Ethiopia represent a new subspecies of Apis mellifera—Apis mellifera simensis n. ssp. 1

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Marina D. MEIXNER , Messele Abebe LETA , Nikolaus KOENIGER , Stefan FUCHS

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LLH Bieneninstitut Kirchhain, Erlenstr. 9, 35274 Kirchhain, Germany Institut für Bienenkunde (Polytechnische Gesellschaft), Johann-Wolfgang-Goethe-Universität Frankfurt, FB Biowissenschaften, Karl-von-Frisch-Weg 2, 61440 Oberursel, Germany Received 28 May 2010 – Revised 28 July 2010 – Accepted 2 August 2010

Abstract – Honey bees endemic to the volcanic dome system of Ethiopia are described as a new subspecies, Apis mellifera simensis, on the basis of morphometrical analyses. Principal component and discriminant analyses show that the Ethiopian bees are clearly distinct and statistically separable from honey bees belonging to neighboring subspecies in eastern Africa. Considerable variation of morphological characters in relation to altitude is present in the samples under analysis, but there are no statistically separable subgroups within this population. There is no indication for the presence of more than one subspecies of honey bee in Ethiopia. Ethiopia / Apis mellifera simensis / subspecies / morphometrics / Africa

1. INTRODUCTION In the biogeographic context of the African continent, the Ethiopian mountain system is an unusual region, geologically dominated by its vast volcanic dome that occupies most of the country's area and reaches elevations of more than 4,000 m, harboring a distinctive flora and fauna. Its isolation and unique climate support a high rate of endemism of animals and plants (Kingdon 1989; Yalden and Largen 1992; Sillero-Zubiri and Gotelli 1994) brought about by the geographical isolation and the unique

Messele Abebe Leta—deceased Electronic supplementary material The online version of this article (doi:10.1007/s13592-011-0007-y) contains supplementary material, which is available to authorized users. Corresponding author: M.D. Meixner, [email protected] Manuscript editor: Klaus Hartfelder

climate of the Ethiopian massifs, as results of the last Ice Age (Kingdon 1989). Likewise, the honey bee fauna of Ethiopia has long been recognized as particular within the African context, and has been subjected to several studies leading to controversial interpretations. Based on early reports (Mammo 1976) and the comparatively few samples available at that time, Ruttner (1976, 1988, 1992) assumed the bees of Ethiopia to be disjunctive populations of Apis mellifera monticola Smith 1961, the subspecies described from the mountains of Kenya and Tanzania, mainly because of their similarity in pigmentation and pilosity. In later analyses, however, Radloff and Hepburn (1997a) suggested to divide the bees of Ethiopia among three different subspecies: Apis mellifera jemenitica Ruttner 1976 in the North, Apis mellifera scutellata Lepeletier, 1836 in the South, and “Apis mellifera bandasii” Mogga 1988 in the central mountains. In a later publication, however, five different subspecies were identified in this region (Amssalu et al. 2004).

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The results of recent research have moved the honey bees of Ethiopia into the focus of attention, suggesting that they may have a unique status and play a distinctive role in general honey bee phylogeography. Based on morphometric data, Ruttner (1988) had first described the geographic structure of the species as consisting of the four different evolutionary branches “A” (Africa), “M” (northern and western Europe), “C” (south-eastern Europe), and “O” (Near East and western Asia). Later, this hypothesis was largely supported by several studies investigating variation of molecular markers (Garnery et al. 1992; Arias and Sheppard 1996; Whitfield et al. 2006); however, in an analysis of mitochondrial DNA, honey bees from Ethiopia deviated substantially from the known lineages and were grouped in a separate molecular lineage termed Y (Franck et al. 2001). The appearance of a new lineage in this region is of particular interest as new analyses based on genetic data strongly indicate that the species started its radiation in Africa (Whitfield et al. 2006), probably about 1 Ma ago (Ruttner 1988; Cornuet and Garnery 1991; Arias and Sheppard 1996), contradicting the previous hypothesis of Ruttner et al. (1978) and Ruttner (1988) who assumed the geographic origin of Apis mellifera somewhere between north-eastern Africa and western Asia. In this paper, we aim to resolve the controversial question of Ethiopian honey bee microtaxonomy and present a comprehensive morphometric analysis based on samples from throughout Ethiopia within the context of neighboring bee populations in eastern Africa.

2. MATERIALS AND METHODS 2.1. Collection of bee samples and morphometric analysis Honey bee samples were collected from a total of 33 locations throughout Ethiopia (Figure 1 and Table in the Electronic supplementary material); either from natural nests or from traditional hives. Most sampling locations were situated inside the volcanic dome

system of Ethiopia, but several of the peripheral sites were located on the rim or on the walls of the East African rift valley. The altitude of sampling localities ranged from 325 to 3,000 m above sea level. Each location is represented by five samples, with each sample containing about 30 worker bees from one colony. Bees were killed and stored in 70% ethanol prior to analysis. Fifteen worker bees of each sample were dissected and 38 morphometric characters were measured according to methods described in Ruttner (1988). Measurements of size and wing venation were performed using a stereo microscope and a computer-aided measuring system based on a video system and measuring program (Meixner 1994). For measurements of pilosity and color scaling a stereo microscope was used.

2.2. Statistical analysis of the data Colony sample means, standard deviation, and standard error were computed for each character of each sample and subsequently used as representative estimates for the colony. Reference samples of the following subspecies from the morphometric data base in Oberursel were included: A. mellifera scutellata (50), A. mellifera monticola (27), A. mellifera jemenitica (48), and Apis mellifera litorea Smith 1961 (9). The data were submitted to factor analysis and sample scores were plotted on principal component coordinates for visualization. Discriminant analysis was used to perform reallocation of samples to their respective groups, based on the results of the factor analysis. To detect variation between the samples and to identify morphologically homogeneous groups, k-means clustering procedures were performed with increasing numbers of clusters, starting with two groups. To determine the number of clusters within Ethiopia that best reflected the structure of the morphological variation, a goodness-of-fit statistics was calculated for each number of clusters. To further analyze variation within Ethiopia, a discriminant analysis was performed using the k-means membership of the samples as group identifiers. Calculations were performed using the SPSS (2003) for Windows 12.0 and Systat 9.0 (2000) statistical packages.

A. mellifera simensis, a new honey bee subspecies in Ethiopia

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Figure 1. Sampling locations in Ethiopia. The map was redrawn and modified after Kingdon (1989). Each symbol represents one colony. The figure shows a plot of the geographical sample distribution allocated to four k-means clusters. Samples assigned to cluster one (circles) are concentrated at high elevations in the centre of the Ethiopian dome, with samples of clusters two (triangles), three (squares) and four (diamonds) forming concentric circles of distribution towards lower elevations in the periphery. The geographic coordinates of each location are given in the Table in the Electronic supplementary material.

3. RESULTS 3.1. The bees of Ethiopia in relation to the surrounding subspecies In an initial factor analysis including reference samples from the adjacent subspecies A. mellifera monticola, A. mellifera scutellata, A. mellifera litorea, and A. mellifera jemenitica, the samples from all five groups fell into overlapping, yet discernible groups. The bees from Ethiopia only partially overlapped with samples from reference groups, but were concentrated in a different plot area (see Figure in the Electronic supplementary material).

The distinctiveness of the Ethiopian bees was confirmed by a discriminant analysis where all samples from the study area were reassigned to their group of origin, and where the Ethiopian bees were entered as group of their own. In this analysis (Figure 2), the bees from Ethiopia form a distinct and very tight cluster that does not overlap with any of the reference groups. All samples from Ethiopia were allocated to this group with probabilities of 0.99