Spatial analysis of morphological variation in African honeybees (Apis mellifera L.) on a continental scale

Apidologie, Jul 2018

José A.F. Diniz-Filho, H. Randall Hepburn, Sarah Radloff, Stefan Fuchs

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Spatial analysis of morphological variation in African honeybees (Apis mellifera L.) on a continental scale

Apidologie Spatial analysis of morphological variation in African honeybees (Apis mellifera L.) on a continental scale José A.F. DINIZ-FILHO 3 H. Randall HEPBURN 1 Sarah RADLOFF 2 Stefan FUCHS 0 0 Institut für Bienenkunde (Polytechnische Gesellschaft), Fachbereich Biologie der J-W. Goethe Universität Frankfurt am Main , Karl-von-Frisch Weg 2, D-61440 Oberursel , Germany 1 Department of Zoology and Entomology, Rhodes University , P.O. Box 94, 6140 Grahamstown , South Africa 2 Department of Statistics, Rhodes University , P.O. Box 94, 6140 Grahamstown , South Africa 3 Departmento de Biologia Geral, ICB, Universidade Federal de Goiás , C.P. 131, 74.001-970 Goiânia, GO , Brazil - Population differentiation of African honeybees has been analysed in a spatial context encompassing the continent's wide geographical range and environmental heterogeneity, based on 10 morphological characters measured from 268 local populations. While autocorrelation indicates a continuous large-scale decrease in similarity in general, clustering of single character correlograms suggests four distinct groups of profiles. This pattern, further supported by mapping factor scores, canonical trend surface analysis axes scores, suggests a variety of microevolutionary mechanisms acting at distinct scales in time and space in different groups of characters. Association with largescale differences in vegetation, climate and traditional subspecific classification has been analysed by analysis of variance (ANOVA). The most important aspect is that the results support the hypothesis that traditional subspecies, at least as defined by these characters, seem to represent integrated evolutionary units well adapted to their local conditions. 1. INTRODUCTION During the last 30 years, different multivariate statistical methods have been used to analyse honeybee populations worldwide [ 20 ]. In a generic sense, these methods have been used to visualise the relative position of observations (usually colony means) in a dimensional reduced space, defined by linear combinations of original morphometric characters. In most situations, the purpose is to test differences among a priori defined groups, especially subspecies [ 12, 20 ]. In recent years, it has been recognised that morphological and genetic variation among honeybee populations should also be investigated in a spatial context. There are many advantages to this approach. Firstly, since the microevolutionary processes related to population differentiation such as selection, migration and drift occur in a spatial context, it would be easier to infer these processes by analysing morphometric variation in geographic space. Secondly, since these processes usually produce at least partially continuous variation, the traditional approach of using discriminant analysis to test differences among subspecies is usually biased by the spatially structured differences within these groups [ 5, 12, 18 ]. Two different approaches have been used to evaluate spatial variation in honeybees. The easier of these is to extend the traditional multivariate approaches, but showing their results in a geographic context by mapping and generating interpolated functions from scores derived from factor, principal component (PCA) or discriminant analyses [2]. In this case, samples are also taken in a spatial design, usually transects [ 13 ]. On the other hand, direct spatial analyses can also be performed, by pairing geographic coordinates (latitude and longitude) with mean vectors of local populations. Trend surface and spatial autocorrelation analyses have been used in these cases to assess population structure and attempt to make inferences about microevolutionary processes involved in population differentiation [3, 4, 6, 7]. Investigations about the population dif ferentiation of African honeybees have been traditionally carried out by partitioning populations into different subspecies, since the findings of Kerr and Portugal-Araújo [ 15 ]. After the introduction of multivariate analyses into honeybee systematics, several different typologies have been proposed [ 12, 20 ]. Because of the wide geographical range and environmental heterogeneity throughout the continent, differentiation among African honeybees can provide insight into the microevolutionary processes involved in population differentiation, both in terms of stochastic processes such as drift and migration, but especially in terms of morphological, behavioural and physiological adaptations to different local conditions. The African bees are smaller than the European subspecies, and form a more homogeneous cluster in multivariate space according to PCA [ 20 ]. Recently, Hepburn and Radloff [ 12 ] discussed the morphological variation in a different context, by analysing in detail patterns of spatial variation and admixture among spatially contiguous populations on a regional basis. In this paper, the main objective is to expand this (...truncated)


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José A.F. Diniz-Filho, H. Randall Hepburn, Sarah Radloff, Stefan Fuchs. Spatial analysis of morphological variation in African honeybees (Apis mellifera L.) on a continental scale, Apidologie, pp. 191-204, Volume 31, Issue 2, DOI: doi:10.1051/apido:2000116