100 research outputs found
Speciation and species delimitation in insular and continental systems
Hintergrund
Zu den grundlegendsten Fragestellungen in der Biologie gehört die Frage nach der Natur und Entstehung biologischer Arten. Dieses Problem der Artdefinition (Engl. "Species Problem") war der Ursprung weitlĂ€ufiger und kontroverser Diskussionen seit der Formulierung der Darwin'schen Evolutionstheorie. Bis heute wurden etwa 30 verschiedene und zum Teil gegensĂ€tzliche Konzepte zur Definition und wissenschaftlichen Abgrenzung der Art veröffentlicht. Eine Einigung ist nicht in Sicht. Gleichzeitig ist die Taxonomie mit der Herausforderung konfrontiert, dass ein immenser Teil der weltweiten Artenvielfalt wissenschaftlich noch nicht erfasst und beschrieben ist. Dies erfordert Methoden, die die Beschreibung neuer Arten beschleunigen und gleichzeitig deren ZuverlĂ€ssigkeit und Nachvollziehbarkeit wahren. DNA-Barcoding, d.h. Artbestimmung an Hand eines kurzen standardisierten Fragments der DNA, soll die Erfassung der Artenvielfalt und das Erkennen unbekannter Arten beschleunigen. Die so genannte "Cybertaxonomie" erlaubt leichteren und schnelleren Zugriff auf vorhandene taxonomische Informationen, indem Daten online und kostenfrei zur VerfĂŒgung gestellt werden. Dies trĂ€gt zur Steigerung der Effizienz taxonomischer Prozesse bei. Integrative Taxonomie kombiniert verschiedene Beweislinien, wie zum Beispiel morphologische, molekulare und ökologische Daten, um die ZuverlĂ€ssigkeit und Nachvollziehbarkeit bei der Abgrenzung und Beschreibung von Arten zu erhöhen.
In dieser Dissertation untersuche ich zwei verschiedene Studiensysteme, um derzeit als gĂŒltig angesehene Modelle der Artbildung und Methoden der Artabgrenzung zu testen. Bei diesen Systemen handelt es sich um die Reptilien der Komoren, einer Gruppe ozeanischer Inseln im westlichen Indischen Ozean, und australische WasserkĂ€fer. Die Biogeographie dieser beiden Gruppen ist durch höchst unterschiedliche Faktoren geprĂ€gt: Die Komoren sind vergleichsweise junge vulkanische Inseln, deren einheimische, landbewohnende und flugunfĂ€hige Faunenelemente ausschlieĂlich auf Besiedelung durch Drift ĂŒber das offene Meer zurĂŒckgehen. Dagegen stellt Australien eine alte und isolierte Landmasse dar, deren Lebensgemeinschaften durch KlimaverĂ€nderungen in der Erdgeschichte geprĂ€gt sind. Ozeanische Inseln wurden schon von frĂŒhen Forschern als wichtige Systeme zum Studium der Biogeographie erkannt, und meine Untersuchung dieser beiden so unterschiedlichen Systeme stellt sowohl die Gemeinsamkeiten als auch die Unterschiede der Biogeographie von Inseln und Kontinenten heraus.
Methoden und wesentliche Ergebnisse
Als Fallbeispiele zur Untersuchung im Rahmen dieser Dissertation wĂ€hlte ich zwei Teilgruppen der komorischen Reptilien (Geckos der Gattung Paroedura und Schlangen der Gattung Lycodryas) sowie drei Teilgruppen der australischen WasserkĂ€fer (die Familie Hygrobiidae und die Gattungen Antiporus und Sternopriscus aus der Familie Dytiscidae) aus. In beiden FĂ€llen wurde der Grundstein fĂŒr weitere Untersuchungen durch DNA-Barcoding gelegt, wie fĂŒr die Reptilien als Teil dieser Dissertation beschrieben. Als nĂ€chsten Schritt fĂŒhrte ich Untersuchungen an mehreren mitochondrialen und nukleĂ€ren Genmarkern durch, um die Phylogenien der jeweiligen Gruppen zu rekonstruieren und, im Fall der Hygrobiidae, das Alter der Phylogenie durch eine molekulare Uhr abzuschĂ€tzen. Ich versuchte, die Phylogenien komorischer Reptilien mit geologischen Daten ĂŒber die erdgeschichtliche Entstehung der Inseln sowie die Ausbreitungsmöglichkeiten zu und zwischen den Inseln in Verbindung zu bringen. Bei Phylogenien australischer KĂ€fer der Gattungen Antiporus und Sternopriscus suchte ich nach Korrelationen zu KlimaverĂ€nderungen in der Erdgeschichte, der Entstehung der australischen Trockengebiete und den Eiszeiten im PleistozĂ€n. Diese Hypothesen konnte ich durch Belege fĂŒr die ökologische Diversifikation australischer KĂ€fer aus meinen Ăkologischen Nischenmodellierungen untermauern.
Auf der Grundlage der Ergebnisse von DNA-Barcoding und molekularen Phylogenien unternahm ich taxonomische Revisionen der betreffenden Gruppen nach Methoden der integrativen Taxonomie. Als Beweislinien verwendete ich Daten aus morphologischen Untersuchungen, mitochondrialen und nukleĂ€ren Genen, sowie kategorische und quantitative ökologische Daten. Dieser Ansatz fĂŒhrte zur Beschreibung einer neuen Art von KĂ€fern (Antiporus occidentalis HAWLITSCHEK, HENDRICH, PORCH, & BALKE, 2011), zweier neuer Arten (Paroedura stellata HAWLITSCHEK & GLAW, 2012 and Lycodryas cococola HAWLITSCHEK, NAGY & GLAW, 2012) und einer Unterart von Reptilien (Lycodryas cococola innocens HAWLITSCHEK, NAGY & GLAW, 2012), sowie zur BestĂ€tigung oder Wiederherstellung der GĂŒltigkeit der zuvor beschriebene Taxa Lycodryas maculatus (GĂNTHER, 1858) und Lycodryas maculatus comorensis (PETERS, 1874). Alle taxonomischen Handlungen wurden gemÀà dem Konzept der Cybertaxonomie ausgefĂŒhrt: es wurden LSID-Nummern vergeben, EintrĂ€ge in Online-Datenbanken vorgenommen, und nach Möglichkeit Publikationsmodi mit freiem Zugang fĂŒr Leser gewĂ€hlt.
Zudem verwendete ich die im Rahmen meiner Dissertation gesammelten Daten zur AbschĂ€tzung des artenschutzfachlichen Status der Reptilien der Komoren. AuĂerdem dienten sie als Basis fĂŒr die Entwicklung von SmartHerper Comoros, einem NaturfĂŒhrer zur Herpetofauna der Komoren als Applikation fĂŒr Smartphone.
Schlussfolgerungen
Die Ergebnisse meiner Untersuchungen weisen auf komplexe biogeographische Muster sowohl im insulĂ€ren als auch im kontinentalen Untersuchungsgebiet hin. Demzufolge haben die Stammformen der dort heimischen Reptilien die Komoren in einem sehr komplizierten Muster besiedelt, das z.B. im Fall der Gecko-Gattung Paroedura mehrere Aussterbe- und Wiederbesiedlungsereignisse beinhaltet und kaum mit der geographischen Lage und dem geologischen Alter der Inseln korreliert. Viele endemische Arten zeigen mögliche morphologische Anpassungen an den Insellebensraum. Molekulare Daten komorischer Reptilien legen nahe, dass Grand Comoro, zuvor als geologisch jĂŒngste Insel angesehen, möglicherweise weit Ă€lter ist als bislang angenommen. Ăber australische WasserkĂ€fer erhobene Daten zeigten, dass Artbildungsereignisse innerhalb dieser Gruppe von höchst unterschiedlichem erdgeschichtlichem Alter sind und vom Mesozoikum (Hygrobiidae) ĂŒber das PleistozĂ€n (Antiporus) bis in die jĂŒngste erdgeschichtliche Vergangenheit (Sternopriscus) reichen. Molekulare Unterschiede weisen darauf hin, dass die "Sternopriscus tarsalis radiation" einen der am schnellsten verlaufenen bislang beschriebenen Artbildungsprozesse innerhalb der Insekten darstellt.
Der integrativ-taxonomische Ansatz erwies sich in meinen Augen bei der Abgrenzung aller neu beschriebenen Taxa wie auch bei der BestĂ€tigung bestehender Taxa als höchst erfolgreich. Durch diesen Ansatz standen Belege fĂŒr die Artabgrenzung auch bei unzureichender morphologischer oder genetischer Differenzierung in ausreichendem MaĂe zur VerfĂŒgung. Ăkologische Daten, insbesondere solche, die bei Ăkologischer Nischenmodellierung gewonnen wurden, haben sich in diesen FĂ€llen als höchst aussagekrĂ€ftig bei der Artabgrenzung erwiesen. Bei der Anwendung des integrativ-taxonomischen Ansatzes auf Schlangen der Gattung Lycodryas argumentierte ich, den Rang der Unterart auf infraspezifische Einheiten mit einem gewissen Grad der Differenzierung anzuwenden.
Schlussendlich liefern die Ergebnisse der Untersuchungen in meiner Dissertation nur einen kleinen, aber meiner Meinung nach dennoch nĂŒtzlichen Beitrag zu unserem VerstĂ€ndnis darĂŒber, wie biologische Arten entstehen und wie sie wissenschaftlich erfasst werden können. Meine Dissertation prĂ€sentiert diese Ergebnisse im Kontext der Debatte ĂŒber die Artdefinition und stellt auch meine Meinung und Position darin dar. Meiner Ansicht nach ist diese Ă€uĂerst fruchtbare Debatte von hoher Bedeutung fĂŒr die zeitgenössische Entwicklung der Evolutionsbiologie und BiodiversitĂ€tsforschung.Background
The question of the nature and the origin of biological species is one of the most fundamental issues in biology. This so-called 'species problem' has been intensely debated since the formulation of the theory of evolution by Darwin. To date, about 30 concepts have been published that attempt to define, often conflictingly, what a species is and how it can be recognized by scientists, and a general agreement is not in sight. At the same time, taxonomy faces the challenge of a huge amount of global biodiversity that remains to be scientifically described. Therefore, taxonomic methods are required that make the description of new species faster and at the same time make them more reliable and reproducible. DNA barcoding, i.e., the use of a short standardized fragment of DNA for species identification, means to accelerate biodiversity inventories and the recognition of new species. Cybertaxonomy makes the access to taxonomic information easier and faster and helps increasing the efficiency of the taxonomic workflow by making data available online and free. Integrative taxonomy combines different lines of evidence, such as morphological, molecular, and ecological data, to make species delimitation and species descriptions more reliable and reproducible.
In this dissertation I explore two different zoological study systems in order to test current models of speciation and methods of species delimitation. These study systems are the reptiles of the Comoros Archipelago, a group of oceanic islands in the Western Indian Ocean, and aquatic beetles of Australia. The biogeographical backgrounds of these two groups are very different: The Comoros are relatively young volcanic islands whose native terrestrial and non-flying fauna originates exclusively from overseas dispersal. In contrast, Australia is an old isolated landmass whose biota were shaped by past climate change. Oceanic islands have been recognized as prime study systems even by early biogeographers, and my study of these two different systems highlights the common grounds as well as the differences between insular and continental biogeography.
Methods and principal findings
I selected two groups out of the Comoran reptiles (Paroedura geckos and Lycodryas snakes) and three groups out of the Australian aquatic beetles (family Hygrobiidae and genera Antiporus and Sternopriscus, Dytiscidae) as study groups for this dissertation. In both cases, the data fundament for subsequent studies was laid by DNA barcoding, as included for reptiles in this dissertation. I then conducted analyses of several mitochondrial and nuclear genetic markers to reconstruct the phylogenies of the study groups and, in Hygrobiidae, estimate the divergence times within the phylogeny in a molecular clock approach. In Comoran reptiles, I attempted to correlate phylogenetic hypotheses with the geological history of island emergence and dispersal to and within the archipelago. In Australian Antiporus and Sternopriscus beetles, I attempted to correlate phylogenies with past climate change, the genesis of the Australian arid zone, and the Pleistocene climate oscillations. I used Ecological Niche Modeling to corroborate these hypotheses with evidence for ecological diversification in Australian beetles.
Based on the results of DNA barcoding and molecular phylogenies, I used an integrative taxonomic approach to revise the taxonomy of the study groups accordingly. The lines of evidence I used were morphological data, mitochondrial molecular markers, nuclear molecular markers, and categorical and quantitative ecological data. This approach led to the description of one new species of beetle (Antiporus occidentalis HAWLITSCHEK, HENDRICH, PORCH, & BALKE, 2011) and two new species (Paroedura stellata HAWLITSCHEK & GLAW, 2012 and Lycodryas cococola HAWLITSCHEK, NAGY & GLAW, 2012), and one subspecies (Lycodryas cococola innocens HAWLITSCHEK, NAGY & GLAW, 2012), of reptiles, as well as to the confirmation or resurrection of the previously described taxa Lycodryas maculatus (GĂNTHER, 1858) and Lycodryas maculatus comorensis (PETERS, 1874). All taxonomic acts followed a cybertaxonomic concept by using LSID numbers, online databases, and, as far as possible, open access publication.
Additionally, I used data collected in the course of this dissertation for estimating the conservation status of Comoran reptiles and for the development of SmartHerper Comoros, a field guide to the herpetofauna of the Comoros as a mobile application for smartphone.
Conclusions
The results of my studies show complex biogeographic patterns in both the insular and the continental study system. According to these results, the ancestors of native reptiles have colonized the Comoros Archipelago in a very complex pattern, including several events of extinction and re-colonization, e.g., in the case of the gecko genus Paroedura, with little correlation to the geographic positions or geological ages of the islands. Many endemic species show possible morphological adaptations to the island environment. Molecular data of reptiles suggest that Grand Comoro, the presumably geologically youngest island, may be considerably older than previously estimated. In Australian aquatic beetles, speciation events were shown to be of very different ages from Mesozoic (Hygrobiidae) to Pleistocene (Antiporus) and very recent (Sternopriscus). Molecular divergences indicate that speciation in the Sternopriscus tarsalis radiation was one of the fastest speciation events so far described among insects.
I applied an integrative taxonomical approach in the delimitation of all newly described taxa and in the confirmation of previously described taxa. This approach provided sufficient evidence for species delimitation even in the absence of morphological differentiation (Antiporus), or when genetic data did not provide any clear evidence (Sternopriscus tarsalis radiation). In these cases, ecological data, particularly such data from Ecological Niche Modeling, was shown to be highly useful in integrative species delimitation. In the same approach applied to Lycodryas snakes, I argued for the usefulness of the subspecies rank for infraspecific entities with some degree of differentiation.
I conclude that my research in the study systems I investigated in this dissertation are but small pieces that nevertheless advance our understanding of speciation and species delimitation by contributing to the ongoing debate on the species problem. My dissertation presents these results and represents my position in the debate. I see this debate as a very fruitful process that is highly important for the current development of evolutionary biology and biodiversity research
Speciation and species delimitation in insular and continental systems
Hintergrund
Zu den grundlegendsten Fragestellungen in der Biologie gehört die Frage nach der Natur und Entstehung biologischer Arten. Dieses Problem der Artdefinition (Engl. "Species Problem") war der Ursprung weitlĂ€ufiger und kontroverser Diskussionen seit der Formulierung der Darwin'schen Evolutionstheorie. Bis heute wurden etwa 30 verschiedene und zum Teil gegensĂ€tzliche Konzepte zur Definition und wissenschaftlichen Abgrenzung der Art veröffentlicht. Eine Einigung ist nicht in Sicht. Gleichzeitig ist die Taxonomie mit der Herausforderung konfrontiert, dass ein immenser Teil der weltweiten Artenvielfalt wissenschaftlich noch nicht erfasst und beschrieben ist. Dies erfordert Methoden, die die Beschreibung neuer Arten beschleunigen und gleichzeitig deren ZuverlĂ€ssigkeit und Nachvollziehbarkeit wahren. DNA-Barcoding, d.h. Artbestimmung an Hand eines kurzen standardisierten Fragments der DNA, soll die Erfassung der Artenvielfalt und das Erkennen unbekannter Arten beschleunigen. Die so genannte "Cybertaxonomie" erlaubt leichteren und schnelleren Zugriff auf vorhandene taxonomische Informationen, indem Daten online und kostenfrei zur VerfĂŒgung gestellt werden. Dies trĂ€gt zur Steigerung der Effizienz taxonomischer Prozesse bei. Integrative Taxonomie kombiniert verschiedene Beweislinien, wie zum Beispiel morphologische, molekulare und ökologische Daten, um die ZuverlĂ€ssigkeit und Nachvollziehbarkeit bei der Abgrenzung und Beschreibung von Arten zu erhöhen.
In dieser Dissertation untersuche ich zwei verschiedene Studiensysteme, um derzeit als gĂŒltig angesehene Modelle der Artbildung und Methoden der Artabgrenzung zu testen. Bei diesen Systemen handelt es sich um die Reptilien der Komoren, einer Gruppe ozeanischer Inseln im westlichen Indischen Ozean, und australische WasserkĂ€fer. Die Biogeographie dieser beiden Gruppen ist durch höchst unterschiedliche Faktoren geprĂ€gt: Die Komoren sind vergleichsweise junge vulkanische Inseln, deren einheimische, landbewohnende und flugunfĂ€hige Faunenelemente ausschlieĂlich auf Besiedelung durch Drift ĂŒber das offene Meer zurĂŒckgehen. Dagegen stellt Australien eine alte und isolierte Landmasse dar, deren Lebensgemeinschaften durch KlimaverĂ€nderungen in der Erdgeschichte geprĂ€gt sind. Ozeanische Inseln wurden schon von frĂŒhen Forschern als wichtige Systeme zum Studium der Biogeographie erkannt, und meine Untersuchung dieser beiden so unterschiedlichen Systeme stellt sowohl die Gemeinsamkeiten als auch die Unterschiede der Biogeographie von Inseln und Kontinenten heraus.
Methoden und wesentliche Ergebnisse
Als Fallbeispiele zur Untersuchung im Rahmen dieser Dissertation wĂ€hlte ich zwei Teilgruppen der komorischen Reptilien (Geckos der Gattung Paroedura und Schlangen der Gattung Lycodryas) sowie drei Teilgruppen der australischen WasserkĂ€fer (die Familie Hygrobiidae und die Gattungen Antiporus und Sternopriscus aus der Familie Dytiscidae) aus. In beiden FĂ€llen wurde der Grundstein fĂŒr weitere Untersuchungen durch DNA-Barcoding gelegt, wie fĂŒr die Reptilien als Teil dieser Dissertation beschrieben. Als nĂ€chsten Schritt fĂŒhrte ich Untersuchungen an mehreren mitochondrialen und nukleĂ€ren Genmarkern durch, um die Phylogenien der jeweiligen Gruppen zu rekonstruieren und, im Fall der Hygrobiidae, das Alter der Phylogenie durch eine molekulare Uhr abzuschĂ€tzen. Ich versuchte, die Phylogenien komorischer Reptilien mit geologischen Daten ĂŒber die erdgeschichtliche Entstehung der Inseln sowie die Ausbreitungsmöglichkeiten zu und zwischen den Inseln in Verbindung zu bringen. Bei Phylogenien australischer KĂ€fer der Gattungen Antiporus und Sternopriscus suchte ich nach Korrelationen zu KlimaverĂ€nderungen in der Erdgeschichte, der Entstehung der australischen Trockengebiete und den Eiszeiten im PleistozĂ€n. Diese Hypothesen konnte ich durch Belege fĂŒr die ökologische Diversifikation australischer KĂ€fer aus meinen Ăkologischen Nischenmodellierungen untermauern.
Auf der Grundlage der Ergebnisse von DNA-Barcoding und molekularen Phylogenien unternahm ich taxonomische Revisionen der betreffenden Gruppen nach Methoden der integrativen Taxonomie. Als Beweislinien verwendete ich Daten aus morphologischen Untersuchungen, mitochondrialen und nukleĂ€ren Genen, sowie kategorische und quantitative ökologische Daten. Dieser Ansatz fĂŒhrte zur Beschreibung einer neuen Art von KĂ€fern (Antiporus occidentalis HAWLITSCHEK, HENDRICH, PORCH, & BALKE, 2011), zweier neuer Arten (Paroedura stellata HAWLITSCHEK & GLAW, 2012 and Lycodryas cococola HAWLITSCHEK, NAGY & GLAW, 2012) und einer Unterart von Reptilien (Lycodryas cococola innocens HAWLITSCHEK, NAGY & GLAW, 2012), sowie zur BestĂ€tigung oder Wiederherstellung der GĂŒltigkeit der zuvor beschriebene Taxa Lycodryas maculatus (GĂNTHER, 1858) und Lycodryas maculatus comorensis (PETERS, 1874). Alle taxonomischen Handlungen wurden gemÀà dem Konzept der Cybertaxonomie ausgefĂŒhrt: es wurden LSID-Nummern vergeben, EintrĂ€ge in Online-Datenbanken vorgenommen, und nach Möglichkeit Publikationsmodi mit freiem Zugang fĂŒr Leser gewĂ€hlt.
Zudem verwendete ich die im Rahmen meiner Dissertation gesammelten Daten zur AbschĂ€tzung des artenschutzfachlichen Status der Reptilien der Komoren. AuĂerdem dienten sie als Basis fĂŒr die Entwicklung von SmartHerper Comoros, einem NaturfĂŒhrer zur Herpetofauna der Komoren als Applikation fĂŒr Smartphone.
Schlussfolgerungen
Die Ergebnisse meiner Untersuchungen weisen auf komplexe biogeographische Muster sowohl im insulĂ€ren als auch im kontinentalen Untersuchungsgebiet hin. Demzufolge haben die Stammformen der dort heimischen Reptilien die Komoren in einem sehr komplizierten Muster besiedelt, das z.B. im Fall der Gecko-Gattung Paroedura mehrere Aussterbe- und Wiederbesiedlungsereignisse beinhaltet und kaum mit der geographischen Lage und dem geologischen Alter der Inseln korreliert. Viele endemische Arten zeigen mögliche morphologische Anpassungen an den Insellebensraum. Molekulare Daten komorischer Reptilien legen nahe, dass Grand Comoro, zuvor als geologisch jĂŒngste Insel angesehen, möglicherweise weit Ă€lter ist als bislang angenommen. Ăber australische WasserkĂ€fer erhobene Daten zeigten, dass Artbildungsereignisse innerhalb dieser Gruppe von höchst unterschiedlichem erdgeschichtlichem Alter sind und vom Mesozoikum (Hygrobiidae) ĂŒber das PleistozĂ€n (Antiporus) bis in die jĂŒngste erdgeschichtliche Vergangenheit (Sternopriscus) reichen. Molekulare Unterschiede weisen darauf hin, dass die "Sternopriscus tarsalis radiation" einen der am schnellsten verlaufenen bislang beschriebenen Artbildungsprozesse innerhalb der Insekten darstellt.
Der integrativ-taxonomische Ansatz erwies sich in meinen Augen bei der Abgrenzung aller neu beschriebenen Taxa wie auch bei der BestĂ€tigung bestehender Taxa als höchst erfolgreich. Durch diesen Ansatz standen Belege fĂŒr die Artabgrenzung auch bei unzureichender morphologischer oder genetischer Differenzierung in ausreichendem MaĂe zur VerfĂŒgung. Ăkologische Daten, insbesondere solche, die bei Ăkologischer Nischenmodellierung gewonnen wurden, haben sich in diesen FĂ€llen als höchst aussagekrĂ€ftig bei der Artabgrenzung erwiesen. Bei der Anwendung des integrativ-taxonomischen Ansatzes auf Schlangen der Gattung Lycodryas argumentierte ich, den Rang der Unterart auf infraspezifische Einheiten mit einem gewissen Grad der Differenzierung anzuwenden.
Schlussendlich liefern die Ergebnisse der Untersuchungen in meiner Dissertation nur einen kleinen, aber meiner Meinung nach dennoch nĂŒtzlichen Beitrag zu unserem VerstĂ€ndnis darĂŒber, wie biologische Arten entstehen und wie sie wissenschaftlich erfasst werden können. Meine Dissertation prĂ€sentiert diese Ergebnisse im Kontext der Debatte ĂŒber die Artdefinition und stellt auch meine Meinung und Position darin dar. Meiner Ansicht nach ist diese Ă€uĂerst fruchtbare Debatte von hoher Bedeutung fĂŒr die zeitgenössische Entwicklung der Evolutionsbiologie und BiodiversitĂ€tsforschung.Background
The question of the nature and the origin of biological species is one of the most fundamental issues in biology. This so-called 'species problem' has been intensely debated since the formulation of the theory of evolution by Darwin. To date, about 30 concepts have been published that attempt to define, often conflictingly, what a species is and how it can be recognized by scientists, and a general agreement is not in sight. At the same time, taxonomy faces the challenge of a huge amount of global biodiversity that remains to be scientifically described. Therefore, taxonomic methods are required that make the description of new species faster and at the same time make them more reliable and reproducible. DNA barcoding, i.e., the use of a short standardized fragment of DNA for species identification, means to accelerate biodiversity inventories and the recognition of new species. Cybertaxonomy makes the access to taxonomic information easier and faster and helps increasing the efficiency of the taxonomic workflow by making data available online and free. Integrative taxonomy combines different lines of evidence, such as morphological, molecular, and ecological data, to make species delimitation and species descriptions more reliable and reproducible.
In this dissertation I explore two different zoological study systems in order to test current models of speciation and methods of species delimitation. These study systems are the reptiles of the Comoros Archipelago, a group of oceanic islands in the Western Indian Ocean, and aquatic beetles of Australia. The biogeographical backgrounds of these two groups are very different: The Comoros are relatively young volcanic islands whose native terrestrial and non-flying fauna originates exclusively from overseas dispersal. In contrast, Australia is an old isolated landmass whose biota were shaped by past climate change. Oceanic islands have been recognized as prime study systems even by early biogeographers, and my study of these two different systems highlights the common grounds as well as the differences between insular and continental biogeography.
Methods and principal findings
I selected two groups out of the Comoran reptiles (Paroedura geckos and Lycodryas snakes) and three groups out of the Australian aquatic beetles (family Hygrobiidae and genera Antiporus and Sternopriscus, Dytiscidae) as study groups for this dissertation. In both cases, the data fundament for subsequent studies was laid by DNA barcoding, as included for reptiles in this dissertation. I then conducted analyses of several mitochondrial and nuclear genetic markers to reconstruct the phylogenies of the study groups and, in Hygrobiidae, estimate the divergence times within the phylogeny in a molecular clock approach. In Comoran reptiles, I attempted to correlate phylogenetic hypotheses with the geological history of island emergence and dispersal to and within the archipelago. In Australian Antiporus and Sternopriscus beetles, I attempted to correlate phylogenies with past climate change, the genesis of the Australian arid zone, and the Pleistocene climate oscillations. I used Ecological Niche Modeling to corroborate these hypotheses with evidence for ecological diversification in Australian beetles.
Based on the results of DNA barcoding and molecular phylogenies, I used an integrative taxonomic approach to revise the taxonomy of the study groups accordingly. The lines of evidence I used were morphological data, mitochondrial molecular markers, nuclear molecular markers, and categorical and quantitative ecological data. This approach led to the description of one new species of beetle (Antiporus occidentalis HAWLITSCHEK, HENDRICH, PORCH, & BALKE, 2011) and two new species (Paroedura stellata HAWLITSCHEK & GLAW, 2012 and Lycodryas cococola HAWLITSCHEK, NAGY & GLAW, 2012), and one subspecies (Lycodryas cococola innocens HAWLITSCHEK, NAGY & GLAW, 2012), of reptiles, as well as to the confirmation or resurrection of the previously described taxa Lycodryas maculatus (GĂNTHER, 1858) and Lycodryas maculatus comorensis (PETERS, 1874). All taxonomic acts followed a cybertaxonomic concept by using LSID numbers, online databases, and, as far as possible, open access publication.
Additionally, I used data collected in the course of this dissertation for estimating the conservation status of Comoran reptiles and for the development of SmartHerper Comoros, a field guide to the herpetofauna of the Comoros as a mobile application for smartphone.
Conclusions
The results of my studies show complex biogeographic patterns in both the insular and the continental study system. According to these results, the ancestors of native reptiles have colonized the Comoros Archipelago in a very complex pattern, including several events of extinction and re-colonization, e.g., in the case of the gecko genus Paroedura, with little correlation to the geographic positions or geological ages of the islands. Many endemic species show possible morphological adaptations to the island environment. Molecular data of reptiles suggest that Grand Comoro, the presumably geologically youngest island, may be considerably older than previously estimated. In Australian aquatic beetles, speciation events were shown to be of very different ages from Mesozoic (Hygrobiidae) to Pleistocene (Antiporus) and very recent (Sternopriscus). Molecular divergences indicate that speciation in the Sternopriscus tarsalis radiation was one of the fastest speciation events so far described among insects.
I applied an integrative taxonomical approach in the delimitation of all newly described taxa and in the confirmation of previously described taxa. This approach provided sufficient evidence for species delimitation even in the absence of morphological differentiation (Antiporus), or when genetic data did not provide any clear evidence (Sternopriscus tarsalis radiation). In these cases, ecological data, particularly such data from Ecological Niche Modeling, was shown to be highly useful in integrative species delimitation. In the same approach applied to Lycodryas snakes, I argued for the usefulness of the subspecies rank for infraspecific entities with some degree of differentiation.
I conclude that my research in the study systems I investigated in this dissertation are but small pieces that nevertheless advance our understanding of speciation and species delimitation by contributing to the ongoing debate on the species problem. My dissertation presents these results and represents my position in the debate. I see this debate as a very fruitful process that is highly important for the current development of evolutionary biology and biodiversity research
Leaping towards a saltatorial lifestyle? An unusually long-legged new species of Rhombophryne (Anura, Microhylidae) from the Sorata massif in northern Madagascar
The Madagascar-endemic microhylid genus Rhombophryne consists of a range of partly or completely fossorial frog species. They lead a poorly known, secretive lifestyle, and may be more diverse than previously thought. We describe a new species from the high altitude forests of the Sorata massif in north Madagascar with unusual characteristics for this genus; R. longicrus sp. n. has long, slender legs, unlike most of its fossorial or semi-fossorial congeners. The new species is closely related to R. minuta, a much smaller frog from the Marojejy massif to the southeast of Sorata with similarly long legs. We discuss the morphology of these species relative to the rest of the genus, and argue that it suggests adaptation away from burrowing and toward a more saltatorial locomotion and an accordingly more terrestrial lifestyle. If this is the case, then these frogs represent yet more ecological diversity within the already diverse Cophylinae. We recommend an IUCN Red List status of Endangered B1ab(iii) for R. longicrus sp. n., because it is known only from a single site in a forested area of roughly 250 km2, which is not yet incorporated into any protected area.Field research was conducted under permit No. 265/12/MEF/SG/DGF/DCB.SAP/SCB (dated 18 Oct. 2012), exportation of specimens under permit No. 163N-EA12/MG12 (dated 17 Dec. 2012), (both issued by the Direction GĂ©nĂ©rale des ForĂȘts de Madagascar), and funded by the Mohamed bin Zayed Species Conservation Fund (project 11253064) and BIOPAT.Peer reviewe
ComposiciĂłn de la dieta de un ensamble de peces del lago tupe, Amazonas, Brasil
Taxonomic composition and diet composition of a fish assemblage in the lake TupĂ© during low water season were studied. Lake TupĂ© is a Central Amazonian blackwater lake in the Rio Negro basin. At high water season, fishes have access to the flooded forest and can freely migrate between the lake and the river Negro, while at low water season these options are not available. Fishes were captured at three dates during low water. Specimens were identified, and for each specimen degree of stomach repletion, content of adipose tissue and stomach content were examined. With the results, fish species were assigned a trophical class. Some species could not be assigned any of these classes and were considered unspecific herbivores, unspecific carnivores or omnivores. The two most abundant species were Acestrorhynchus falcirostris and Hemiodus immaculatus. The most important food item was plant material, and the most abundant trophic class was specialized herbivore. Plant material is generally considered to play a minor role in the diet of Amazonian fishes. This supports the conclusions that during low water, the fish community in the lake TupĂ© relies heavily on allochtonous input of food. Therefore, and due to the high degree of competition, many fish species perform strong shifts in their feeding habits.La composiciĂłn taxonĂłmica y composiciĂłn de la dieta de una ensamble de peces en el lago TupĂ© durante la temporada de estiaje fueron estudiadas. El lago TupĂ© es se ubica en la parte Central AmazĂłnica, de aguas negras en la cuenca del rĂo Negro. En la temporada de inundaciĂłn, los peces tienen acceso al bosque y pueden migrar libremente entre el lago y el rĂo Negro, mientras que en Ă©poca de estiaje estas opciones no estĂĄn disponibles. Los peces fueron capturados en tres momentos durante el estiaje. Los especĂmenes fueron identificados, y para cada espĂ©cimen se examinĂł el grado de repleciĂłn del estĂłmago, el contenido de tejido adiposo y el contenido del estĂłmago. Con los resultados, las especies de peces fueron asignados a una clase trĂłfica. Algunas especies no se pudieron asignar en cualquiera de estas clases y fueron considerados herbĂvoros inespecĂficos, carnĂvoros u omnĂvoros inespecĂficos. Las dos especies mĂĄs abundantes fueron Acestrorhynchus falcirostris y Hemiodus immaculatus. El tipo de alimento mĂĄs importante fue material vegetal y la clase trĂłfica mĂĄs abundante fue herbĂvoro especializado. El material vegetal generalmente se considera que desempeñan un papel de menor importancia en la dieta de los peces amazĂłnicos. Esto apoya la conclusiĂłn de que durante el estiaje, la comunidad de peces en el lago TupĂ© basa en gran medida su dieta en la entrada alĂłctona de los alimentos. Por lo tanto, y debido al alto grado de competencia, muchas especies de peces realizan fuertes cambios en sus hĂĄbitos de alimentaciĂłn
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Pleistocene climate change promoted rapid diversification of aquatic invertebrates in Southeast Australia
Background: The Pleistocene Ice Ages were the most recent geohistorical event of major global impact, but their consequences for most parts of the Southern hemisphere remain poorly known. We investigate a radiation of ten species of Sternopriscus, the most species-rich genus of epigean Australian diving beetles. These species are distinct based on genital morphology but cannot be distinguished readily by mtDNA and nDNA because of genotype sharing caused by incomplete lineage sorting. Their genetic similarity suggests a Pleistocene origin. Results: We use a dataset of 3858 bp of mitochondrial and nuclear DNA to reconstruct a phylogeny of Sternopriscus using gene and species trees. Diversification analyses support the finding of a recent rapid speciation event with estimated speciation rates of up to 2.40 species per MY, which is considerably higher than the proposed average rate of 0.16 species per MY for insects. Additionally, we use ecological niche modeling and analyze data on habitat preferences to test for niche divergence between species of the recent Sternopriscus radiation. These analyses show that the species can be characterized by a set of ecological variables referring to habitat, climate and altitude. Conclusions: Our results suggest that the repeated isolation of populations in glacial refugia might have led to divergent ecological adaptations and the fixation of morphological traits supporting reproductive isolation and therefore may have promoted speciation. The recent Sternopriscus radiation fulfills many characteristics of a species flock and would be the first described example of an aquatic insect species flock. We argue that the species of this group may represent a stage in speciation past the species flock condition because of their mostly broad and often non-overlapping ranges and preferences for different habitat types.Organismic and Evolutionary Biolog
Pleistocene climate change promoted rapid diversification of aquatic invertebrates in Southeast Australia
Background: The Pleistocene Ice Ages were the most recent geohistorical event of major global impact, but their consequences for most parts of the Southern hemisphere remain poorly known. We investigate a radiation of ten species of Sternopriscus, the most species-rich genus of epigean Australian diving beetles. These species are distinct based on genital morphology but cannot be distinguished readily by mtDNA and nDNA because of genotype sharing caused by incomplete lineage sorting. Their genetic similarity suggests a Pleistocene origin. Results: We use a dataset of 3858 bp of mitochondrial and nuclear DNA to reconstruct a phylogeny of Sternopriscus using gene and species trees. Diversification analyses support the finding of a recent rapid speciation event with estimated speciation rates of up to 2.40 species per MY, which is considerably higher than the proposed average rate of 0.16 species per MY for insects. Additionally, we use ecological niche modeling and analyze data on habitat preferences to test for niche divergence between species of the recent Sternopriscus radiation. These analyses show that the species can be characterized by a set of ecological variables referring to habitat, climate and altitude. Conclusions: Our results suggest that the repeated isolation of populations in glacial refugia might have led to divergent ecological adaptations and the fixation of morphological traits supporting reproductive isolation and therefore may have promoted speciation. The recent Sternopriscus radiation fulfills many characteristics of a species flock and would be the first described example of an aquatic insect species flock. We argue that the species of this group may represent a stage in speciation past the species flock condition because of their mostly broad and often non-overlapping ranges and preferences for different habitat types
Extensive introgression at late stages of species formation: Insights from grasshopper hybrid zones
The process of species formation is characterized by the accumulation of multiple reproductive barriers. The evolution of hybrid male sterility, or Haldane's rule, typically characterizes later stages of species formation, when reproductive isolation is strongest. Yet, understanding how quickly reproductive barriers evolve and their consequences for maintaining genetic boundaries between emerging species remains a challenging task because it requires studying taxa that hybridize in nature. Here, we address these questions using the meadow grasshopper Pseudochorthippus parallelus, where populations that show multiple reproductive barriers, including hybrid male sterility, hybridize in two natural hybrid zones. Using mitochondrial data, we infer that such populations diverged some 100,000 years ago, at the beginning of the last glacial cycle in Europe. Nuclear data show that contractions at multiple glacial refugia, and post-glacial expansions have facilitated genetic differentiation between lineages that today interact in hybrid zones. We find extensive introgression throughout the sampled species range, irrespective of the current strength of reproductive isolation. Populations exhibiting hybrid male sterility in two hybrid zones show repeatable patterns of genomic differentiation, consistent with shared genomic constraints affecting ancestral divergence or with the role of those regions in reproductive isolation. Together, our results suggest that reproductive barriers that characterize late stages of species formation can evolve relatively quickly, particularly when associated with strong demographic changes. Moreover, we show that such barriers persist in the face of extensive gene flow, allowing future studies to identify associated genomic regions
The Genomics of Isolated Populations of Gampsocleis glabra (Orthoptera: Tettigoniidae) in Central and Western Europe
Habitat destruction and fragmentation are among the major current threats to global biodiversity. Fragmentation may also affect species with good dispersal abilities. We study the heath bushcricket Gampsocleis glabra, a specialist of steppe-like habitats across Europe that are highly fragmented, investigating if these isolated populations can be distinguished using population genomics and if there are any traces of admixture or dispersal among them. We try to answer these questions using genome-wide SNP data generated with ddRAD sequencing. We calculated F-statistics and visualized differentiation using STRUCTURE plots. While limited by the difficulty of sampling this threatened species, our results show that all populations except one that was represented by a singleton were clearly distinct, with pairwise FST values between 0.010 and 0.181. STRUCTURE indicated limited but visible admixture across most populations and probably also an exchange of individuals between populations of Germany and The Netherlands. We conclude that in G. glabra, a certain amount of gene flow has persisted, at least in the past, also among populations that are isolated today. We also detect a possibly more recent dispersal event between a population in The Netherlands and one in Germany, which may be human aided. We suggest that the conservation of larger populations should be maintained, that efforts should be taken to restore abandoned habitat, that the preservation even of small habitat fragments may be beneficial for the conservation of this species, and that these habitats should be regularly monitored for possible (re-)colonization
When Giant Stick Insects Play With Colors: Molecular Phylogeny of the Achriopterini and Description of Two New Splendid Species (Phasmatodea: Achrioptera) From Madagascar
Achrioptera is a taxon of extremely large and exceptionally colorful stick insects endemic to Madagascar and the Comoros Archipelago. We studied the phylogenetic position of the Achriopterini, comprising the genera Achrioptera and Glawiana, based on a multigene phylogeny and concluded that it is a sister group to other Madagascan phasmids (Anisacanthidae) rather than to Neotropical or Australo-Pacific groups as was suggested in a previous study based on morphology. Our results also point to unresolved relationships (potential paraphyly of Achrioptera), taxonomic issues (elevation of A. punctipes cliquennoisi to species level), and detection of cryptic diversity (in A. impennis), demonstrating the need of additional research. A DNA barcoding approach based on COI sequences of Achrioptera species revealed a clear discrimination between closely related and morphologically similar species. Applying integrative taxonomy using multiple lines of evidence, we demonstrated that the well-known species with blue males from Montagne des Français and Foret d'Orangea in the far north of Madagascar, previously attributed to Achrioptera fallax, represents a new species, which we describe as Achrioptera manga sp. nov. based on morphological, chromatic, and genetic (mitochondrial and nuclear) differences. We also describe a second new giant species from this massif: Achrioptera maroloko sp. nov. is among the largest insects (females reaching up to 24 cm total length) and differs from its sister species A. spinosissima from western Madagascar in morphology, coloration, and substantial DNA barcode divergence. These magnificent new species confirm the significance of the Montagne des Français area as a hotspot of biodiversity and microendemism. The biogeographic pattern of the species pair A. fallax/A. manga is paralleled by species pairs of reptiles and amphibians suggesting a similar evolutionary history. Finally, we discuss the sexual dichromatism of Achrioptera species with conspicuous males and mostly cryptic females. As possible reasons, we consider female mate choice and divergent habits of males and females, but aposematism combined with toxic substances produced in defense glands or accumulated in the insect's body from nutritional plants are more plausible explanations for this phenomenon
Repositories for Taxonomic Data: Where We Are and What is Missing
AbstractNatural history collections are leading successful large-scale projects of specimen digitization (images, metadata, DNA barcodes), thereby transforming taxonomy into a big data science. Yet, little effort has been directed towards safeguarding and subsequently mobilizing the considerable amount of original data generated during the process of naming 15,000â20,000 species every year. From the perspective of alpha-taxonomists, we provide a review of the properties and diversity of taxonomic data, assess their volume and use, and establish criteria for optimizing data repositories. We surveyed 4113 alpha-taxonomic studies in representative journals for 2002, 2010, and 2018, and found an increasing yet comparatively limited use of molecular data in species diagnosis and description. In 2018, of the 2661 papers published in specialized taxonomic journals, molecular data were widely used in mycology (94%), regularly in vertebrates (53%), but rarely in botany (15%) and entomology (10%). Images play an important role in taxonomic research on all taxa, with photographs used in &gt;80% and drawings in 58% of the surveyed papers. The use of omics (high-throughput) approaches or 3D documentation is still rare. Improved archiving strategies for metabarcoding consensus reads, genome and transcriptome assemblies, and chemical and metabolomic data could help to mobilize the wealth of high-throughput data for alpha-taxonomy. Because long-termâideally perpetualâdata storage is of particular importance for taxonomy, energy footprint reduction via less storage-demanding formats is a priority if their information content suffices for the purpose of taxonomic studies. Whereas taxonomic assignments are quasifacts for most biological disciplines, they remain hypotheses pertaining to evolutionary relatedness of individuals for alpha-taxonomy. For this reason, an improved reuse of taxonomic data, including machine-learning-based species identification and delimitation pipelines, requires a cyberspecimen approachâlinking data via unique specimen identifiers, and thereby making them findable, accessible, interoperable, and reusable for taxonomic research. This poses both qualitative challenges to adapt the existing infrastructure of data centers to a specimen-centered concept and quantitative challenges to host and connect an estimated 2 million images produced per year by alpha-taxonomic studies, plus many millions of images from digitization campaigns. Of the 30,000â40,000 taxonomists globally, many are thought to be nonprofessionals, and capturing the data for online storage and reuse therefore requires low-complexity submission workflows and cost-free repository use. Expert taxonomists are the main stakeholders able to identify and formalize the needs of the discipline; their expertise is needed to implement the envisioned virtual collections of cyberspecimens. [Big data; cyberspecimen; new species; omics; repositories; specimen identifier; taxonomy; taxonomic data.]</jats:p
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