Hippolais Pallida Species Complex
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J Ornithol (2005) 146: 127–136 DOI 10.1007/s10336-004-0071-4 ORIGINAL ARTICLE Ulf Ottosson Æ Staffan Bensch Æ Lars Svensson Jonas Waldenstro¨m Differentiation and phylogeny of the olivaceous warbler Hippolais pallida species complex Received: 15 June 2004 / Revised: 13 October 2004 / Accepted: 13 December 2004 / Published online: 18 March 2005 Ó Dt. Ornithologen-Gesellschaft e.V. 2005 Abstract The pattern of phenotypic and molecular var- same or closely related mtDNA haplotypes. It remains iation within the polytypic olivaceous warbler H. pallida open whether the African taxa should be regarded as was examined. This species is distributed in the southern three valid subspecies of the Eastern olivaceous warbler, parts of the western Palaearctic, central Asia and in the or if they are better treated as a single African subspe- arid parts of northern Africa, and also in parts of the cies. sub-Saharan Sahel zone. Based on morphology, five subspecies, at times assigned to three groups, have been Keywords Hippolais pallida Æ Morphology Æ identified. By comparing morphological, behavioural, Phylogeny Æ Sylviidae Æ Taxonomy vocal and molecular variation, we investigated the phe- notypic and phylogenetic relationships within the Hip- polais pallida group. The morphological and genetic data of the present study support the view of splitting the Introduction olivaceous warbler into a western (former subspecies opaca) and an eastern form (former subspecies elaeica, Traditionally, avian taxonomy has been based on mor- pallida, reiseri and laeneni). Opaca is consistently and phological and behavioural traits, incorporating differ- significantly larger than the other taxa in all size mea- ences in size and plumage, vocalisation and reproductive surements, even if it does share morphological proper- behaviour. However, in taxa where variation of such ties with elaeica in characters associated with migration. traits is limited and hard to measure objectively, e.g. in The song of the polytypic pallida differs clearly from that many genera within the family Sylviidae, phylogenetic of opaca, and is remarkably consistent within its wide relationships are hard to disentangle. In such groups, range which comprises four subspecies. The molecular DNA sequences can contribute a large number of phy- analysis, and the resulting phylogenetic pattern, clearly logenetically informative characters that will aid the separated opaca on a single branch distant from the traditional taxonomy (Shirihai et al. 2001). Although other subspecies. The eastern form consists of two non- genetic divergence as such does not delineate species overlapping haplotype groups: elaeica with relatively (Ferguson 2002), the distance and pattern of sequence diverse mtDNA variation, and the three African sub- divergence will indicate for how long and effective the species pallida, reiseri and laeneni, which all share the compared taxa have been isolated (Nichols 2001). Be- cause speciation correlates with time, genetic divergence Communicated by F. Bairlein will indicate how likely the two taxa are to behave as different species according to a defined species concept. U. Ottosson Æ J. Waldenstro¨ m Ottenby Bird Observatory, On the other hand, the scientific community has not PL 1500, 38065 Degerhamn, Sweden reached a consensus on the species concept. Hence, the debate of whether closely related taxa are species or not U. Ottosson Æ S. Bensch Æ J. Waldenstro¨ m Department of Animal Ecology, Lund University, will continue. Meanwhile, an improved understanding of Ecology Building, 22362 Lund, Sweden differences between closely related taxa will shed light on the speciation process, regardless of the species concept L. Svensson Runebergsgatan 4, 11429 Stockholm, Sweden applied. The reed warbler group is a species-rich clade tradi- U. Ottosson (&) 18A, rue de Mamer, 8280 Kehlen, Luxembourg tionally subdivided into three genera (Acrocephalus, E-mail: [email protected] Hippolais and Chloropeta) comprising species with sim- Tel.: +352-26-300290 ilar morphology and behaviour (Sibley and Monroe 128 1990, 1993; Helbig and Seibold 1999). Phylogenetic and the polytypic eastern olivaceous warbler H. elaeica. relationships based on mitochondrial cytochrome b se- Finally, Svensson (2001) treated all five taxa and reached quences have challenged both inter- and intrageneric the same conclusion as Helbig and Seibold (1999) based relationships, which have traditionally been based on on behavioural and morphological data. morphology (Leisler et al. 1997; Helbig and Seibold Variation in plumage and body size is very limited 1999). For example, H. pallida, H. caligata and H. rama between taxa in this group; they are basically grey- seem to be more closely related to the Acrocephalus brown above and off-white below with a short pale su- warblers than to the other Hippolais species. percillium. In fresh plumage, the eastern form elaeica Here we examine the pattern of phenotypic and has an olive tinge on the upperparts and a faint but molecular variation within the polytypic olivaceous obvious pale wing panel, both of which are lacking in warbler H. pallida. This species (group) is distributed in opaca, the western form. The three African taxa, which the southern parts of the western Palaearctic, Central are largely found in the vicinity of arid habitats includ- Asia and arid parts of northern Africa, and also in parts ing deserts and semi-desert, are smaller with more of the sub-Saharan Sahel zone. Based on morphology, rounded wings, browner above and, in the case of five subspecies, at times assigned to three groups, have laeneni, slightly paler. For further plumage characters, been identified (e.g. Sibley and Monroe 1990, 1993; see Svensson (2001) and below. Cramp 1992; Baker 1997; Urban et al. 1997 and refer- The dull and more or less featureless appearance ences therein): (1) opaca which breeds in Iberia and NW makes field identification difficult. This probably con- Africa and winters across the Sahel and the Sudan sa- tributed to the confusion regarding the distribution of vannahs from the Atlantic coast to Cameroon, and (2) these taxa, and also as to the distribution of their close elaeica, which breeds in SE Europe and SW Asia and relatives, booted warbler H. caligata and Sykes’s warbler winters mainly in eastern Africa. These two taxa can be H. rama (cf. Cramp 1992; Baker 1997; Urban et al. 1997; said to represent two separate groups. The third group, Svensson 2001). It is, for instance, unlikely that laeneni the ‘pallida group’, is divided into three subspecies: (3) breeds anywhere in the Nile Valley or that elaeica win- pallida, which breeds in Egypt (and possibly N Sudan), ters in India, to give just two examples of published but of which the northernmost subpopulation migrates questionable ranges. The level of difficulty is further south into Sudan, (4) reiseri, which breeds in oases in the demonstrated by the fact that a Hippolais population Sahara from W Algeria (and apparently S and SE breeding on the north Somalian coast (Ash and Pearson Morocco) to SW Tunisia (Nefta, Douz) and W Libya 2002) has still not been conclusively identified. A study (Fezzan), at least northern populations apparently mi- of song and DNA seems desirable before it can be grate to south of the desert in winter, and (5) laeneni, established whether these birds belong to H. p. pallida or which is resident in the arid Sahel-belt in sub-Saharan to Sykes’s warbler, or represent a hitherto undescribed Africa, in Niger, Nigeria, the Chad region and W Sudan. taxon. Interestingly, opaca and reiseri seem to breed parap- Here we compare morphological, behavioural, vocal atrically (or possibly locally sympatrically) in Morocco and molecular variation to resolve the phylogeny of the and Algeria (Roselaar in Cramp 1992; Urban et al. 1997; Hippolais pallida group. Svensson 2001). Based on morphological differences, Roselaar (in Cramp 1992) suggested a split of the pallida- group into three ‘incipient species’, opaca, pallida (with Methods suggested subspecies reiseri and laeneni), and elaeica. Helbig and Seibold (1999) did not treat the African taxa, Olivaceous warblers were studied both in the field and in but suggested a split into two species based on molecular museum collections (Table 1). Fieldwork was under- data, the monotypic western olivaceous warbler H. opaca taken in Spain and Morocco (opaca), The Gambia Table 1 Origin of collected samples of olivaceous warblers Taxa Site Morphology Behaviour Blood Feather Tissue Sequence Recordings Hippolais pallida and places of study laeneni Nigeria X X X X opaca Nigeria X X The Gambia X Spain X Morooco X X X X reiseri The Gambia X Mus. Paris X Tunisia X X X X elaeica Genebank X Bulgaria X X X Turkey X X X Kazakhstan X X X X pallida Egypt X X X X 129 (opaca, reiseri, unpublished data provided by J.M.B. King), Tunisia (reiseri), Nigeria (opaca, laeneni), Egypt (pallida), and in Greece, Bulgaria, Turkey and Ka- zakhstan (elaeica). The number of examined specimens is shown in Table 2. ) ) ) ) ), L. Svensson, 2001 2001 2001 2001 2001 Vocalisation Notes on vocalisation are largely based on field notes unpublished data and recordings made by L.S. Recordings of laeneni (Chappuis 2000, J. Wilson, unpublished data) and opaca (Chappuis 2000) were also used. Morphology Morphological measurements were taken from trapped birds and specimens examined in museum collections. Wing-length was measured to the closest 0.5 mm (maximum chord for live birds, method 3, Svensson 1992); bill-length, both to skull and to feather-base, to Type Origin Reference the closest 0.1 mm; bill-width partly (in Nigeria) according to the picture on p.178 in Svensson (1992), n partly (Svensson 2001, and later field work) at the inner edge of the nostrils, and to the closest 0.1 mm; tail- length in mm; and tail graduation, i.e. the difference between the longest and shortest tail-feathers measured complex on the folded tail to the closest millimetre. Wing formula was recorded as is customary, primaries measured from Mean Range tip of wing to tip of each primary on the closed wing, H.