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Taxonomy of the southern African Zosterops
Abstract
The four major groupings into which the Zosterops forms of southern African can be arranged have for long been treated by conservative systematists as constituting four discrete species (Z. capensis, Z. pallidus, Z. virens and Z. senegalensis).
In a major study, published in 1957, Moreau arrived at the tentative conclusion that in zoo-geographical South Africa Z. cupensis and Z. wirens are clearly conspecific, Z. pallidus is a doubtful monotypic species, and Z. senegalais is a polytypic species of wide continental range, specifically segregated from the foregoing on the basis of a wingltail ratio character, and of juxtaposition without evidence of interbreeding.
A new study of the complex problem of Zosterops relationships in South Africa based on a critical study of over 900 specimens examined in the Durban Museum, suggests that only two species (Z. pallidus and Z. senegahsis), very closely related and part of the same superspecies, are actually involved.
... As a consequence, the taxonomy of the southern African Zosteropidae has varied considerably over the past 70 years (Table 1). The aim of this paper is to provide a hypothesis for the number of defensible terminal taxa of Zosterops within southern Africa through the quantitative analyses of morphological information that previous authors used to identify putative taxa and clinal variation (Gill, 1936; Roberts, 1942; Moreau, 1957; Clancey, 1967; Skead, 1967). We specifically aim to diagnose taxonomic units or historical entities as opposed to clinal or eco-geographic variants with respect to the environmental heterogeneity represented by the diverse biomes of southern Africa. ...
... Discontent with subspecies as a concept (Wilson & Brown, 1953; Zink, 2004 ) apparently often results from the inappropriate use in the past (Patten & Unitt, 2002; Remsen, 2010; Winker, 2010), with several authors suggesting (Rising, 2007; Remsen, 2010; Winker, 2010) the need for the use of a least one diagnosable morphometric trait, for the justifiable use of the subspecies. Classifications of southern African Zosterops taxa (Gill, 1936; Roberts, 1942; Moreau, 1957; Clancey, 1967; Skead, 1967; Hockey et al., 2005; Van Balen, 2008) have varied considerably in the number of taxa described (Table 1), with underpart plumage variation being the primary line of evidence in delimiting the number of Zosterops taxa. However , no consensus has yet been reached. ...
... Parsimony (Fig. 4) and MDS analyses (Fig. 2) of the morphometric data also indicate a lack of taxonomic partitioning among southern African Zosterops taxa. Underpart plumage coloration of African Zosterops taxa is viewed as the primary means by which to distinguish among taxa (Gill, 1936; Roberts, 1942; Moreau, 1957; Clancey 1967; Skead, 1967). Our results support this view. ...
The recognition of objectively diagnosable and evolutionarily significant terminal taxa, that is, evolutionarily significant units (ESU), is essential for the generation of defensible taxic hypotheses necessary for all forms of evolutionary and comparative biology and for effective guiding of biodiversity conservation. However, there has been a long and on-going, sometimes heated debate, on the merits of the subspecies category in this endeavour. To determine possible ESU present in southern African white-eyes, Zosterops spp., we used uni-and multi-variate statistical approches to re-investigate the morphological characteristics (morphometric and plumage coloration) used in past taxonomic studies to propose nine putative southern African Zosterops ESU, described at the time as subspecies. Four ESU emerged from these analyses. Geographical, discriminatory, multifaceted analyses suggest that these four taxa, Z. senegalensis, Z. virens, Z. capensis and Z. pallidus warrant species status.
... There have been several attempts to classify and describe the white-eyes found in southern Africa (see Gill, 1936;Roberts, 1942;Moreau, 1957;Clancey, 1967;Skead, 1967;Hockey et al., 2005;van Balen, 2008;Oatley et al., 2011). The two primary contributors to Zosterops taxonomy in southern Africa had contrasting ideas. ...
... v. capensis and Z. v. atmorii), and one green bellied form (Z. v. virens). Clancey (1967), on the other hand, recognized Z. senegalensis, but lumped Z. pallidus and Z. virens (including the grey-and green-bellied subspecies) as a single species, giving subspecies status to three color forms: Z. pallidus pallidus (cinnamon flanks), Z. p. capensis (grey-bellied) and Z. p. virens (green-bellied). Because there is little size difference between Z. pallidus, Z. capensis and Z. virens, this underpart coloration has in the past, and remains, the main character used to define the taxonomy of southern African Zosterops . ...
... The intermediate environmental conditions, and in particular temperature and rainfall of localities (Aliwal North, Nova Vita, Taba Nchu) of overlap between Z. pallidus and Z. capensis are likely to have facilitated secondary contact, and subsequent interbreeding, between these taxa. Hybridization is not expected to be restricted to these two taxa as morphological intergradation has also been documented between Z. pallidus and Z. virens (Moreau, 1957;Clancey, 1967;Oatley et al., 2011). No evidence of molecular hybridization between these two taxa was found in this study. ...
... Four distinct forms of white eyes (Oatley, Bowie & Crowe, 2011) are found in south- ern Africa and have been the subject of rich taxonomic debate (e.g. Moreau, 1957;Clancey, 1967). Recent mitochondrial and nuclear DNA sequencing evidence suggests that the Orange River white eye Zosterops pallidus and the Cape white eye Zosterops virens are not conspecific or possibly even sister-species (Oatley et al., 2012, Cox et al., 2014). ...
... Based on their underpart plumage coloration, two subspecies of Z. virens are recognized: the green-bellied Zosterops virens virens and the grey bellied Zosterops virens capensis. Interbreeding between the green-bel- lied Z. v. virens and the cinnamon-flanked Z. pallidus has been responsible for the lumping of the two taxa as a single species (Clancey, 1967). In some early field guides, phenotypic intermediates were described as a distinct taxon (e.g. ...
The interbreeding of two species after a period of separation (secondary contact) most often results in stable areas of hybridization or tension zones characterized by selection against hybrid individuals. Three plumage forms of Zosterops meet and interbreed in central South Africa. Here we examine how phenotypic measures (biometric and plumage) and genotypic markers (mitochondrial and nuclear DNA) change through a putative hybrid zone located in the area where the ranges of the Orange River White-eye Zosterops pallidus and a subspecies of the Cape White-eye, Z. virens capensis, meet. Four of the five sequenced loci (ATP6, MUSK, GADPH and TGF-β2) showed strong divergence and differentiation between allopatric parental populations, whereas the sex-linked CHD1Z locus exhibited high homogeneity. Microsatellite data also distinguished between pure Z. pallidus and Z. v. capensis populations. Together, the nuclear data (introns and microsatellites) identified at least 12 hybrid individuals as later generation hybrids (i.e. F2 or backcrosses), and no F1-hybrids were detected. As genetic incompatibility does not appear to play a role in restricting this stable hybrid zone, it is likely that environmental conditions including biome type and edge effect are constraining hybrid zone movement.
... Despite various previous analyses (Moreau 1957;Clancey 1967;Hall and Moreau 1970;Sibley and Monroe 1990;Oatley et al. 2011;Chittenden et al. 2012), there has been little consensus in the scientific literature regarding the species status and relationships of southern African white-eyes (Warren et al. 2006;Oatley et al. 2012). Various authors have suggested that the treatment of their superspecies and species be regarded with caution (e.g. ...
... It is therefore no surprise that the recent scientific literature applies various binomial names to the Cape White-eye, including Zosterops pallidus (e.g. Franke et al. 1997;Hulley et al. 2004;Lunt et al. 2004), Z. virens The early history of the taxonomy of southern African white-eyes, in particular the work of Gill (1936), Roberts (1942), Moreau (1957), Clancey (1967) and Skead (1967), is described by Oatley (2011) (Table 1). More recently, southern African white-eyes were described by Clancey (1980) as a single polytypic species, Z. pallidus, possibly because of interbreeding and hybridisation known to occur between different white-eyes . ...
The recent scientific literature employs three binomial names for the southern African endemic bird known as the Cape White-eye: Zosterops capensis, Z. pallidus and Z. virens. This unacceptable inconsistency reflects the contention regarding white-eye systematics. Recent molecular work by Oatley and colleagues led to the suggestion that Z. virens and Z. capensis should both fall under the name Z. virens. We urge ornithologists to adopt this convention, and we encourage further molecular stud ies in order to clarify the taxonomy of southern African white-eyes.
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