Some of my recent papers are listed below. Click for a full list of scientific publications, congress papers, and outreach activities!
Disentangling a grasshopper species complex
Grasshoppers of the genus Chorthippus, especially the C. biguttulus group, are common and widespread, but at the same time notorious for posing problems to taxonomists. DNA barcoding or the use of single genetic markers, even complete mitochondrial genomes, have not been successful in delimiting these species. Our paper presents results of transcriptomic data for resolving this evolutionary young species complex.
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Hawlitschek O., Ortiz E.M., Noori S., Webster K.C., Husemann M., Pereira R. (2022): Transcriptomic data reveals nuclear-mitochondrial discordance in Gomphocerinae grasshoppers (Insecta: Orthoptera: Acrididae). Molecular Phylogenetics and Evolution 170, 107439. <get paper>
The future of cataloguing biodiversity
New species are continuously discovered and described. This process generates an enormous amount of data, but much of this data is not easily accessible or stored in a way that does not guarantee its availability for future generations. This paper reviews the types of data published along with species descriptions and data storage strategies. We advocate the use of cyberspecimens – linking various kinds of data, e.g., molecular data, 3D scan data, photographs, audio records, and other metadata with a voucher specimen deposited in a scientific collection via a unique specimen identifier. Creating the necessary infrastructure for this storage allows the handling of the data according to the FAIR principles—data should be Findable, Accessible, Interoperable, and Reusable.
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Miralles A., Bruy T., Wolcott K., Scherz M.D., Begerow D., Beszteri B., Bonkowski M., Felden J., Gemeinholzer B., Glaw F., Glöckner F.O., Hawlitschek O., Kostadinov I., Nattkemper T.W., Printzen C., Renz J., Rybalka N., Stadler M., Weibulat T., Wilke T., Renner S.S., Vences M. (2020): Repositories for taxonomic data: Where we are and what is missing. Systematic Biology 69, 1231-1253. <get paper>
The TaxonOMICS project at the Evolution 2018 conference in Montpellier
Click here to download a pdf of our poster "Admixture and fast speciation in species complexes of phytophagous Hymenoptera and Orthoptera: A MuseOMICS approach"!
Does biogeography prove geology wrong?
The fact that terrestrial species living on oceanic islands (which were never connected to any other landmass) cannot be older than these islands seems obvious. However, older taxa have been postulated for some islands, and indications were also shown for Grand Comoro. Our paper provides a robust phylogeny and molecular dating of the gecko genus Ebenavia to verify these assumptions. We show that not only the clade inhabiting Grand Comoro Island is much older than the island itself, but also that the clade endemic to the Comoros is older than all the clades of Madagascar, an island much older than the Comoros, The island of Mayotte was possibly re-colonized by a Malagasy clade after previous extinction of the Comoros clade. The small and inconspicuous Ebenavia geckos have proven to be excellent dispersers who travelled along the marine currents even to remote islands of the Western Indian Ocean. Further biogeographic study of reptiles of the region may clearly yield many more surprises.
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Hawlitschek O., Toussaint E.F.A.T., Crottini A., Gehring P.S., Ratsoavina F.M., Cole N., Nopper J., Lam A.W., Vences M., Glaw F. (2016): Gecko phylogeography in the Western Indian Ocean region: The oldest clade of Ebenavia inunguis lives on the youngest island. Journal of Biogeography 44, 409-420. <get paper>
Hawlitschek O., Scherz M.D., Ruthensteiner B., Crottini A., Glaw F. (2018): Computational molecular species delimitation and taxonomic revision of the genus Ebenavia Boettger, 1878. The Science of Nature 105: 49. <get paper>
Hawlitschek O., Scherz M.D., Ruthensteiner B., Crottini A., Glaw F. (2018): Computational molecular species delimitation and taxonomic revision of the genus Ebenavia Boettger, 1878. The Science of Nature 105: 49. <get paper>
The inverse latitudinal diversity gradient
Global biodiversity generally follows a pattern called the latitudinal diversity gradient: the number of species increases from the poles to the equator. This is observed not only in the overall species diversity of our planet, but also in many specific organism groups with a global distribution. Scientists attempt to explain this pattern with the assumption that tropical environments are geologically older, have been more stable over time, and therefore more time was available for speciation. The waterbeetle subfamily Colymbetinae, remarkably, shows the contrary pattern: an inverse latitudinal diversity gradient with higher species richness in temperate regions. We tested the importance of ecological niche conservatism in the phylogeny of this group. Our results suggest that the distribution pattern may have been maintained by temperate niche conservatism, i.e., the tendency of species living in temperate regions to maintain this ecological adaptation.
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Morinière J., van Dam M., Hawlitschek O., Bergsten J., Michat M., Hendrich L., Ribera I., Toussaint E.F.A.T., Balke M. (2016): Triggers of an inversed latitudinal diversity gradient – An Old World tropical twist in freshwater arthropods. Nature Scientific Reports 6, 26340. <get paper>
DNA barcoding of reptiles and amphibians of Germany
This joint data release of the projects Barcoding Fauna Bavarica and German Barcode of Life comprises DNA barcodes of all German species of reptiles and amphibians. Our database now allows the reliable species identification of all life stages and even of tissue remains. Furthermore, our paper highlights other potential applications of DNA barcoding, such as the detection of allochthonous lineages of German amphibians and reptiles, monitoring of gene flow and also noninvasive sampling via environmental DNA.
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Hawlitschek O., Morinière J., Dunz A., Franzen M., Rödder D., Glaw F., Haszprunar G. (2016): Comprehensive DNA barcoding of the herpetofauna of Germany. Molecular Ecology Resources 16, 242-253. <get paper>
Palleon: a new genus of ancient chameleons from Madagascar
Madagascar is the worldwide hot-spot of chameleon diversity and also houses some very ancient clades of this fascinating group of reptiles. Our understanding of this diversity has made enormous progress following the wide application of molecular phylogenetic methods. However, there are other modern methods that complement our understanding of chameleon evolution. X-ray computed tomograph scanning (CT) allows studies of the internal anatomy of organisms that were previously impossible at this level of detail. CT scanning supported the theory that two species of Malagasy chameleons represented a more ancient group than previously thought. They are now placed in their own new genus "Palleon", derived from the Greek words "palae-" (meaning "old") and word "leon" (meaning "lion", as in other chameleon genera).
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Glaw F., Hawlitschek O., Ruthensteiner B. (2013): A new genus name for an ancient Malagasy chameleon clade and a PDF-embedded 3D model of its skeleton. Salamandra 49, 237-238. <get paper>
Why and when subspecies still make sense
Species concepts (what is a species?) and species delimitation (how are particular species defined?) are highly debated topics in evolutionary biology. Today, researchers use modern species concepts, such as the phylogenetic, evolutionary or general lineage species concepts, and integrative taxonomy approaches to tackle these questions. The discussion of subspecies status and concepts has been addressed much less extensively, with some researchers completely refraining from recognizing subspecies. We use the examples of the snakes of the Comoros Islands to make a case for subspecies, describing why the snake previously recognized as Lycodryas sanctijohannis is in fact a complex of four lineages representing different levels of evolutionary divergence. Based on an integrative analysis of morphological and molecular data, we recognize two species (lineages of deeper divergence) with each two subspecies (of shallower divergence) and explain why subspecies still make sense.
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Hawlitschek O., Nagy Z.T., Glaw F. (2012): Island evolution and systematic revision of Comoran snakes: why and when subspecies still make sense. PLOS ONE 7, e42970. 19 pp. <get paper>
And check out the blog entry at The Bite Stuff!
Distinguishing indistinguishable species
Traditionally, species have been recognized based on visible morphological differences. However, the study of genetic data shows that many evolutionary lineages of organisms show divergence levels comparable to those of distinct species, even if they are morphologically indistinguishable. In the case of the Australian diving beetle Antiporus femoralis, we compare morphological, genetic, and ecological data between the Eastern and Western populations. Phylogenetic reconstruction shows that these two populations have evolved separately for millions of years, and ecological models support the view that they have adapted to different climate niches. We therefore recognized the Western population as a new species Antiporus occidentalis despite the absence of morphological differences. Evolution does not always leave easily visible traces.
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Hawlitschek O., Porch N., Hendrich L., Balke M. (2011): Ecological niche modelling and nDNA sequencing support a new, morphologically cryptic beetle species unveiled by DNA barcoding. PLOS ONE 6, e16662. 14 pp. <get paper>