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Integrative taxonomy of birds: Studies into the nature, origin and delimitation of species
Stockholm University, Faculty of Science, Department of Zoology.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Species are the basic currency in biodiversity studies but what constitutes a species has long been controversial. A major breakthough was the insight that most systematists agree that species are segments of population lineages, and that multiple lines of evidence should be employed and integrated, a procedure called integrative taxonomy. For this dissertation, I have studied integrative taxonomy from three angles. First, I address a series of influential claims about the nature and empirical basis of taxonomic change in birds. In Paper I, I show that taxonomic change is overwhelmingly data-driven. Thus, increasing numbers of species represent progress, not taxonomic inflation resulting from a change in species concept. In Paper II, I provide the first detailed quantitative analysis of how species are delimited in practice. This study shows that, contrary to widely held beliefs, avian taxonomy has not been dominated by the Biological Species Concept. Instead, species delimitation is increasingly pluralistic and eclectic. I argue that taxonomic practice is more unified than is implied by the controversy over species concepts. Integrative taxonomy can provide new insights into the speciation process. In Paper III, I show that two very different evolutionary patterns have been referred to by the term ‘ring species’ which are best distinguished using an integrative approach. Finally, two case studies of integrative taxonomy are presented. In Paper IV, we describe a new cryptic species of owl, the Rinjani Scops Owl (Otus jolandae), using evidence from plumage details, morphometrics, vocalizations and playback studies. Paper V presents a study of the evolutionary history of diversification in a widespread Indo-Pacific passerine, the Red-bellied Pitta (Erythropitta erythrogaster). Using molecular species delimitation methods and evidence from plumage details and morphometrics, we suggest that this species includes up to 17 species which originated during the Pleistocene

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University , 2013. , 36 p.
Keyword [en]
Aves, biogeography, integrative taxonomy, pluralism, ring species, speciation, species criteria, species limits, taxon chain
National Category
Biological Systematics
Research subject
Systematic Zoology
Identifiers
URN: urn:nbn:se:su:diva-96049ISBN: 978-91-7447-818-1 (print)OAI: oai:DiVA.org:su-96049DiVA: diva2:662902
Public defence
2013-12-12, Lilla hörsalen, Naturhistoriska riksmuseet, Frescativägen 40, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defence the following papers were unpublished and had a status as follows: Paper 2: Ahead of Print; Paper 3: Manuscript.

Available from: 2013-11-20 Created: 2013-11-08 Last updated: 2013-11-20Bibliographically approved
List of papers
1. Increasing numbers of bird species result from taxonomic progress, not taxonomic inflation.
Open this publication in new window or tab >>Increasing numbers of bird species result from taxonomic progress, not taxonomic inflation.
2009 (English)In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 276, 3185-3191 p.Article in journal (Refereed) Published
Abstract [en]

The impact and significance of modern taxonomy on other fields in biology have been subjects of much debate. It has been proposed that increasing numbers of vertebrate species are largely owing to ‘taxonomic inflation’. According to this hypothesis, newly recognized species result from reinterpretations of species limits based on phylogenetic species concepts (PSCs) rather than from new discoveries. Here, I examine 747 proposals to change the taxonomic rank of birds in the period 1950–2007. The trend to recognize more species of birds started at least two decades before the introduction of PSCs. Most (84.6%) newly recognized species were supported by new taxonomic data. Proposals to recognize more species resulted from application of all six major taxonomic criteria. Many newly recognized species (63.4%) were not based exclusively on PSC-based criteria (diagnosability, monophyly and exclusive coalescence of gene trees). Therefore, this study finds no empirical support for the idea that the increase in species is primarily epistemological rather than data-driven. This study shows that previous claims about the causes and effects of taxonomic inflation lack empirical support. I argue that a more appropriate term for the increase in species is ‘taxonomic progress’.

Keyword
taxonomy; species limits; species criteria; species concepts
National Category
Biological Systematics
Research subject
Systematic Zoology
Identifiers
urn:nbn:se:su:diva-42865 (URN)10.1098/rspb.2009.0582 (DOI)
Available from: 2010-10-07 Created: 2010-09-16 Last updated: 2013-11-08Bibliographically approved
2. The application of species criteria in avian taxonomy and its implications for the debate over species concepts
Open this publication in new window or tab >>The application of species criteria in avian taxonomy and its implications for the debate over species concepts
2014 (English)In: Biological Reviews, ISSN 1464-7931, E-ISSN 1469-185X, Vol. 89, no 1, 199-214 p.Article in journal (Refereed) Published
Abstract [en]

The debate over species concepts has produced a huge body of literature on how species can, may or should be delimited. By contrast, very few studies have documented how species taxa are delimited in practice. The aims of the present study were to (i) quantify the use of species criteria in taxonomy, (ii) discuss its implications for the debate over species concepts and (iii) assess recent claims about the impact of different species concepts on taxonomic stability and the ‘nature’ of species. The application of six species criteria was examined in taxonomic studies of birds published between 1950 and 2009. Three types of taxonomic studies were included: descriptions of new species (N=329), proposals to change the taxonomic rank of species and subspecies (N=808) and the taxonomic recommendations of the American Ornithologists’ Union Committee on Classification and Nomenclature (N=176). In all three datasets, diagnosability was the most frequently applied criterion, followed by reproductive isolation and degree of difference. This result is inconsistent with the popular notion that the Biological Species Concept is the dominant species concept in avian taxonomy. Since the 1950s, avian species-level taxonomy has become increasingly pluralistic and eclectic. This suggests that taxonomists consider different criteria as complementary rather than as rival approaches to species delimitation. Application of diagnosability more frequently led to the elevation of subspecies to species rank than application of reproductive isolation, although the difference was small. Hypotheses based on diagnosability and reproductive isolation were equally likely to be accepted in a mainstream checklist. These findings contradict recent claims that application of the Phylogenetic Species Concept causes instability and that broader application of the Biological Species Concept can stabilise taxonomy. The criteria diagnosability and monophyly, which are commonly associated with Phylogenetic Species Concepts, were used throughout the study period. Finally, no support was found for the idea that Phylogenetic Species Concepts have caused a change in the ‘nature’ of species taxa. This study demonstrates that there is a discrepancy between widely held perceptions of how species are delimited and the way species are actually delimited by taxonomists. Theoretically oriented debates over species concepts thus may benefit from empirical data on taxonomic practice.

Keyword
Biological Species Concept, birds, integrative taxonomy, Phylogenetic Species Concept, species limits, taxonomic stability
National Category
Biological Systematics
Research subject
Systematic Zoology
Identifiers
urn:nbn:se:su:diva-91100 (URN)10.1111/brv.12051 (DOI)000329357500011 ()
Available from: 2013-06-19 Created: 2013-06-19 Last updated: 2017-12-06Bibliographically approved
3. The ring species concept revisited
Open this publication in new window or tab >>The ring species concept revisited
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Ring species may offer important insights into the role of isolation by distance in speciation. In recent years, the study of ring species has been revigorated by the application of phylogeographic methods. The concept of ring species, however, has received little attention since its original formulation in the first half of the twentieth century. A review of the two best-documented cases of putative ring species suggests that different evolutionary patterns have been referred to by the term ‘ring species’. These putative ring species share a circular colonization pattern but have fundamentally different evolutionary histories and patterns of geographic variation. Because these patterns cannot be explained by a single evolutionary model, a terminological distinction is warranted. It is suggested that the term ‘ring species’ be restricted to taxa which form a single evolutionary unit and in which the end-points have diverged as a result of isolation by distance. The new evolutionary term ‘taxon chain’ is suggested for a clade consisting of multiple evolutionary units separated by secondary contact zones. The study of ring species and taxon chains requires an integrative approach, including the description of geographic variation, phylogeographic study of historical divergence, assessment of gene flow, and study of interactions in contact zones.

Keyword
circular overlaps, Ensatina, isolation by distance, Phylloscopus, speciation, taxon chain
National Category
Evolutionary Biology
Identifiers
urn:nbn:se:su:diva-95972 (URN)
Available from: 2013-11-07 Created: 2013-11-07 Last updated: 2013-11-08
4. A new owl species of the genus Otus (Aves: Strigidae) from Lombok, Indonesia
Open this publication in new window or tab >>A new owl species of the genus Otus (Aves: Strigidae) from Lombok, Indonesia
2013 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 2, e53712- p.Article in journal (Refereed) Published
Abstract [en]

The avifauna of Indonesia is one of the richest in the World but the taxonomic status of many species remains poorly documented. The sole species of scops owl known from Lombok has long been assigned to the widespread Moluccan Scops Owl Otus magicus on the basis of superficial similarities in morphology. Field work in 2003 has shown that the territorial song of the scops owls inhabiting the foothills of Gunung Rinjani differs dramatically from that of O. magicus and is more similar to those of Rufescent Scops Owl O. rufescens and Singapore Scops Owl O. cnephaeus. Detailed comparisons of sound recordings and museum specimens with those of other scops owls in Wallacea and the Indo-Malayan region have confirmed the distinctiveness of the Lombok population. We describe Otus jolandae as a new species, the Rinjani Scops Owl. It is locally common at elevations from 25-1350 m and occurs within Gunung Rinjani National Park. The new species is known from seven specimens collected by Alfred Everett in 1896. Otus jolandae represents the first endemic bird species from Lombok.

National Category
Biological Systematics
Research subject
Systematic Zoology
Identifiers
urn:nbn:se:su:diva-87645 (URN)10.1371/journal.pone.0053712 (DOI)000315970300012 ()
Available from: 2013-02-19 Created: 2013-02-13 Last updated: 2017-12-06Bibliographically approved
5. The spatio-temporal colonization and diversification across the Indo-Pacific by a ‘great speciator’ (Aves, Erythropitta erythrogaster)
Open this publication in new window or tab >>The spatio-temporal colonization and diversification across the Indo-Pacific by a ‘great speciator’ (Aves, Erythropitta erythrogaster)
Show others...
2013 (English)In: Proceedings of the Royal Society of London. Biological Sciences, ISSN 0962-8452, E-ISSN 1471-2954, Vol. 280, no 1759, 20130309- p.Article in journal (Refereed) Published
Abstract [en]

The Indo-Pacific region has arguably been the most important area for the formulation of theories about biogeography and speciation, but modern studies of the tempo, mode and magnitude of diversification across this region are scarce. We study the biogeographical history and characterize levels of diversification in the wide-ranging passerine bird Erythropitta erythrogaster using molecular, phylogeographic and population genetics methods, as well as morphometric and plumage analyses. Our results suggest that E. erythrogaster colonized the Indo-Pacific during the Pleistocene in an eastward direction following a stepping stone pathway, and that sea level fluctuations during the Pleistocene only locally may have promoted gene flow. A molecular species delimitation test suggests that several allopatric island populations of E. erythrogaster may be regarded as species. Most of these putative new species are further characterized by diagnostic differences in plumage. Our study reconfirms the E. erythrogaster complex as a ‘great speciator’: it represents a complex of up to 17 allopatrically distributed, reciprocally monophyletic and/or morphologically diagnosable species that originated during the Pleistocene. Our results support the view that observed latitudinal gradients of genetic divergence among avian sister-species may have been affected by incomplete knowledge of taxonomic limits in tropical bird species.

Keyword
island biogeography; integrative taxonomy; speciation; phylogeny; Pleistocene climate changes
National Category
Evolutionary Biology Ecology
Identifiers
urn:nbn:se:su:diva-88820 (URN)10.1098/rspb.2013.0309 (DOI)000317482100022 ()
Funder
Swedish Research Council, 621-2010-5321EU, European Research Council, PIEF-GA-2011-300924
Available from: 2013-04-01 Created: 2013-04-01 Last updated: 2017-12-06Bibliographically approved

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