Dutch Avifaunal List: Species Concepts, Taxonomic Instability, and Taxonomic Changes in 1977-1998
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139 DUTCH AVIFAUNAL LIST: SPECIES CONCEPTS, TAXONOMIC INSTABILITY, AND TAXONOMIC CHANGES IN 1977-1998 GEORGE SANGSTER1, CORNELIS J. HAZEVOET2,3, ARNOUD B. VAN DEN BERG4, C.S. (KEES) ROSELAAR2 & RONALD SLUYS2 Sangster G., c.J. Hazevoet, A.B.Van den Berg, C.S. Roselaar & R. Sluys 1999. Ar dea 87: 139-165. The Dutch avifaunal list is revised based on the principles of phylogenetic theory and methodology. A phylogenetic approach to species-level taxa is adopted. In con trast to the 'Biological Species Concept', this approach is compatible with the recon struction of evolutionary relationships, recognises species on the basis of historical patterns and views species as products of history. Two basic rules are applied for the recognition of higher taxa: (1) higher taxa are named clades and represent monophy- letic groups of species or less inclusive clades, and (2) phylogenetic knowledge should be expressed as accurately as possible by taxonomy. Systematics is viewed as a historical science in which phylogenies are hypotheses of historical relationships. Taxonomies should reflect the best supported hypotheses of relationships and are subject to further modification as knowledge of relationships grows. Key words: systematics - taxonomy - phylogeny - species concepts - species - higher taxa lNieuwe Rijn 27, 2312 JD Leiden, Netherlands; E-mail: [email protected]; 2Insti tute of Systematics and Population Biology, Zoological Museum, University ofAm sterdam, P.O. Box 94766, 1090 GT Amsterdam, Netherlands; 3Museu e Laborat6rio Zool6gico e Antropol6gico (Museu Bocage), Rua da Escola Politecnica 58, 1250 e9 Lisboa, Portugal; 4Duinlustparkweg 98, 2082 EG Santpoort-Zuid, Netherlands INTRODUCTION (1998). Due to limitations of space, the present report only includes a brief summary of the ratio This report includes taxonomic and nomenclatu nale for each decision. More extensive and ex ral changes adopted by the Dutch committee for plicit motivations for the recognition of some of avian systematics (Commissie Systematiek Ne the species-level and higher taxa listed here will derlandse Avifauna, CSNA) since Voous (1977). be published elsewhere. Proposals affecting the Dutch list that were re jected by the CSNA are also discussed. The Neth Choice of species concept and its application erlands Ornithologists' Union (NOU) and the Over the past few years the fields of system Dutch Birding Association (DBA) support the atic and evolutionary biology have been invigo CSNA and its reports are published in both Ardea rated by a scientific discussion on the concept of and Dutch Birding. The present report is essen species (for reviews, see Sluys 1991; Mayden tially similar to two separate publications in 1997; Zink 1997). Although this discussion contin Dutch Birding (Sangster et al. 1997; 1998). The ues, it is also true that new and useful insights committee currently consists of five members have been gained already that can be incorporated (year of election between parentheses): Arnoud fruitfully into an up to date and modem descrip B. van den Berg (1995), Cornelis J. Hazevoet tion of avian diversity. One of the insights that has (1996), C.S. (Kees) Roselaar (1995), George surfaced in the literature is that different species Sangster, Secretary (1996) and Ronald Sluys concepts may be best for different purposes 140 ARDEA 87(1),1999 (Endler 1989) and it seems increasingly likely that gely based on these views. The Isolation Species no single species concept will satisfy the multiple Concept (popularly known as the 'Biological purposes of 'species' in the biological sciences Species Concept') is rejected because its proper (Sluys 1991; Hull 1997), However, a theme com ties violate all three aforementioned principles. mon to all biological sciences is that all taxa are First, interbreeding taxa are not necessarily more historically connected through their pattern of an closely related to each other than they are to taxa cestry and descent. All living taxa are the product from which they are reproductively isolated. Be ofhistory, and we can understand little about their cause interbreeding is the prime criterion for con diversity without knowledge of their history, i.e. specificity under the ISC, the ISC could still re the phylogenetic knowledge provided by system gard such interbreeding taxa as conspecifics. atics (O'Hara et al. 1988). Virtually all compara Therefore, the problem of lumping taxa which are tive studies of biological variation within and not closely related in a single species and, hence, among taxa depend on such phylogenetic knowl the misrepresentation of evolutionary history, is edge for interpretation (Felsenstein 1985; Brooks inherent to the ISC and does not simply result & McLennan 1991; Harvey & Pagel 1991). There from errors in application. Phylogenetic analyses fore, in biodiversity studies and comparative biol indicate that in various groups of birds 'polyty ogy a fundamental requirement of species-level pic' species recognised by the ISC do not repre taxa is that they are compatible with the recon sent natural (monophyletic) groups. Evidence struction of evolutionary relationships. Species comes from phylogenies based on both morpho concepts which group taxa that are not closely re logical (Livezey 1995a; Chu 1998; Veron 1999) and lated in a single species misrepresent evolution molecular data sets (Zink 1988; Friesen et al. 1996; ary history. Second, species-level taxa should be Leisler et al. 1997; Roy et al. 1997; Trewick 1997). delimited on the basis of historical subdivisions Second, under the ISC taxa are recognised as spe (i.e. historical patterns), rather than present-day cies ifthey remain 'reproductively isolated', in the or possible future interactions and processes sense that they do not fuse into a single population (Liden & Oxelman 1989), such as hybridisation (Mayr 1982; 1996). The ISC, therefore, is prospec and gene flow. Species concepts which are pro tive (O'Hara 1993; 1994; Maddison 1997); only fu spective and which require speculations about the ture events will show whether currently recog future are not helpful in biology; since all of our nised taxa remain reproductively isolated or fuse data are of the present and past, the units by into each other. This poses both theoretical and which we interpret these data must also be strictly practical problems. It makes little sense to try to historical (Maddison 1997). Third, species should interpret the past and present diversity of organ be basal, taxonomically comparable units (Cra isms with a taxonomy that is based on expecta craft 1987; 1989): species should be basal taxa, tions ('dreams', Maddison 1997) about the future. that is, taxa that contain no included taxa. A spe A practical problem is that, except for rare cases, cies concept should not combine several distinct the process of fusion transcends observable time. taxa in a single (polytypic) 'species' because such The likely time-to-fusion may be measured in 'species' actually are higher, more inclusive taxa. WOOs or even millions of years (Zink & McKi Species concepts which recognise not only single trick 1995). Third, many 'species' recognised by units (monotypic species) but also polytypic as the ISC contain more than one taxon. The ISC rec semblages (polytypic species) as 'species' run ognises monotypic species but may also unite up counter to the fundamental need for species-level to 10 or more diagnosable taxa and still recognise taxa to be basal and comparable. the resulting unit as a single 'species'. This not The decision by the CSNA to abandon the tra only underestimates and misrepresents biodiver ditional Isolation Species Concept (ISC) in favour sity but also compromises interspecific compari of a Phylogenetic Species Concept (PSC) was lar- sons (Prum 1994; Hazevoet 1996; Cracraft 1997). Sangster et at.: TAXONOMIC CHANGES IN 1977-1998 141 Two distinct Phylogenetic Species Concepts sion, however, would recognise the descendant have been advocated. These versions agree in species, but not the ancestral 'species', as a phy viewing species as products of evolution, not as logenetic species because only the former is players in evolution, and support the notion of monophyletic. Proponents of the monophyly ver species as basal taxa. The original version, pro sion propose that such ancestral 'species' are rec posed by Cracraft (1983) and further developed by ognised as a separate class of species, for which Nixon & Wheeler (1990) and Davis & Nixon they propose the term 'metaspecies' (Donoghue (1992), considers a phylogenetic species to be an 1985; De Queiroz & Donoghue 1988). irreducible cluster of organisms possessing at The CSNA has adopted the diagnosability least one diagnostic character state. This version version of the PSC as its operational species con thus focuses on the diagnosability of species. Dia cept because no phylogenetic analysis is required gnostic character states are discrete character prior to delimiting species, its implementation in states which are fixed within the species and are volves little modification of existing taxonomic absent from close relatives. Diagnosability of practices and does not require the recognition of species may be based on any intrinsic attribute, additional classes of species. It is believed that either morphological, molecular, ethological or a these are advantages over the monophyly version, combination of these. It should be emphasised and similar versions (Baum & Shaw 1995), and that