Schwander Tanja, Oldroyd Benjamin P. (2016), Androgenesis: where males hijack eggs to clone themselves, in Phil. Trans. R. Soc. B
Tanja Schwander (2016), Evolution: The End of an Ancient Asexual Scandal, in Current Biology
, 26(6), R233 -R235.
A. Fontcuberta García-Cuenca, Z. Dumas, T. Schwander (2016), Extreme genetic diversity in asexual grass thrips populations., in Journal of Evolutionary Biology
Lavanchy Guillaume, Strehler Marie, Llanos-Roman Maria N., Lessard-Therrien Malie, Humbert Jean-Yves, Dumas Zoé, Jalvingh Kirsten, Ghali Karim, Fontcuberta García-Cuenca Amaranta, Zijlstra Bart, Arlettaz Raphael, Schwander Tanja (2016), Habitat heterogeneity favors asexual reproduction in natural populations of grassthrips, in Evolution
Larose Chloé, Schwander Tanja (2016), Nematode endoparasites do not codiversify with their stick insect hosts, in Ecology and Evolution
Kraaijeveld Jens Bast Ina Schaefer Tanja Schwander Mark Maraun Stefan Scheu Ken (2016), No accumulation of transposable elements in asexual arthropods, in Molecular Biology and Evolution
, 33(3), 697-706.
Kirsten Jalvingh, Jens Bast, Tanja Schwander (2016), The Evolution and Maintenance of Sex, in Wedell Nina (ed.), Editor-in-Chief: R. Kliman, Section Editor: N. Wedell, Elsevier, 89.
W.J. Ma, B.A. Pannebakker, van de Zande L., T. Schwander, B. Wertheim, L.W. Beukeboom (2015), Diploid males support a two-step mechanism of endosymbiont-induced thelytoky in a parasitoid wasp., in BMC Evolutionary Biology
, 15(1), 84-84.
D. Arbuthnott, B.J. Crespi, T. Schwander (2015), Female stick insects mate multiply to find compatible mates, in American Naturalist
, 186(4), 519-530.
van der Kooi C.J., T. Schwander (2015), Parthenogenesis: Birth of a New Lineage or Reproductive Accident?, in Current Biology
, 25(15), 659-661.
A.A. Comeault, S.M. Flaxman, R. Riesch, E. Curran, V. Soria-Carrasco, Z. Gompert, T.E. Farkas, M. Muschick, T.L. Parchman, T. Schwander, J. Slate, P. Nosil (2015), Selection on a genetic polymorphism counteracts ecological speciation in a stick insect., in Current Biology
, 25(15), 1975-1981.
Salazar-Jaramillo Laura, Paspati Angeliki, van de Zande Louis, Vermeulen Cornelis Joseph, Schwander Tanja, Wertheim Bregje (2014), Evolution of a Cellular Immune Response in Drosophila: A Phenotypic and Genomic Comparative Analysis, in GENOME BIOLOGY AND EVOLUTION
, 6(2), 273-289.
van der Kooi Casper J., Schwander Tanja (2014), EVOLUTION OF ASEXUALITY VIA DIFFERENT MECHANISMS IN GRASS THRIPS (THYSANOPTERA: Aptinothrips), in EVOLUTION
, 68(7), 1883-1893.
Neiman M., Sharbel TF., Schwander T (2014), Genetic causes of transitions from sexual reproduction to asexuality in plants and animals, in Journal of Evolutionary Biology
, 27(7), 1346.
Ma W-J, Pannebakker B.A., Beukeboom L.W., Schwander T.*, van de Zande L.* (2014), Genetics of decayed sexual traits in a parasitoid wasp with endosymbiont-induced asexuality, in Heredity
, 113(5), 424.
van der Kooi Casper J., Schwander Tanja (2014), On the fate of sexual traits under asexuality, in BIOLOGICAL REVIEWS
, 89(4), 805-819.
Schwander Tanja (2014), Parthenogenesis
, Oxford Bibliographies, Oxford.
Schwander T., Marais G., Roze D. (2014), Sex uncovered: the evolutionary biology of reproductive systems, in Journal of Evolutionary Biology
, 27(7), 1287.
Soria-Carrasco Victor, Gompert Zachariah, Comeault Aaron A., Farkas Timothy E., Parchman Thomas L., Johnston J. Spencer, Buerkle C. Alex, Feder Jeffrey L., Bast Jens, Schwander Tanja, Egan Scott P., Crespi Bernard J., Nosil Patrik (2014), Stick Insect Genomes Reveal Natural Selection's Role in Parallel Speciation, in SCIENCE
, 344(6185), 738-742.
Schwander Tanja, Libbrecht Romain, Keller Laurent (2014), Supergenes and Complex Phenotypes, in CURRENT BIOLOGY
, 24(7), 288-294.
Schwander Tanja, Arbuthnott Devin, Gries Regine, Gries Gerhard, Nosil Patrik, Crespi Bernard J. (2013), Hydrocarbon divergence and reproductive isolation in Timema stick insects, in BMC EVOLUTIONARY BIOLOGY
, 13, 151.
Schwander Tanja, Crespi Bernard J., Gries Regine, Gries Gerhard (2013), Neutral and selection-driven decay of sexual traits in asexual stick insects, in PROCEEDINGS OF THE ROYAL SOCIETY B-BIOLOGICAL SCIENCES
, 280(1764), 20130823.
Ma Wen-Juan, Schwander Tanja, Patterns and mechanisms in endosymbiont-induced parthenogenesis, in Journal of Evolutionary Biology
Explaining the widespread occurrence of sexual reproduction throughout the animal and plant kingdoms, despite the potential advantages of parthenogenesis, is one of the greatest challenges for evolutionary biology. The two-fold advantage a parthenogenetic female should enjoy because she does not produce sons that cannot themselves produce offspring, would have to be fully compensated by benefits conferred by sex and recombination. This paradox has generated a large body of theory seeking to explain the rarity of parthenogens among multicellular taxa, given their theoretical reproductive advantage. One aspect that is typically overlooked however, is that current parthenogens derive from sexual ancestors and that several genetic and developmental constraints should present a severe barrier to the transition to asexual reproduction. How the several thousand described asexual lineages have overcome these numerous expected constraints and what genetic and ecological changes underlie a successful transition to parthenogenesis in natural populations, remain completely elusive. My research proposal focuses on different aspects of transitional stages from sexual reproduction to parthenogenesis, using Orthopteroid insects as model systems. Orthopteroid insects comprise many independently derived asexual lineages, which allows conducting replicate comparisons between asexual lineages and their sexual counterparts. Parthenogenesis in this group does not involve reproductive parasites and can be achieved by different cellular processes, including clonal reproduction (mitotic parthenogenesis) as well as parthenogenesis modes involving meiosis and secondary restoration of somatic ploidy levels. Finally, the typical sex determination system in this group is XX:XO (females have two, males only one sex chromosome), which is the most widespread system in animals. As a consequence, insights on constraints for the evolution of parthenogenesis stemming from Orthopteroids are more representative than conclusions from groups with derived sex determination systems. The present proposal consists of three parts. The aim of the first part is to test whether the independent acquisition of parthenogenesis in related taxa results in similar cellular and developmental processes underlying the production of offspring. This will be addressed by conducting cytological assays and by analyzing sets of genes required for the proper completion of meiosis in seven independently derived asexual lineages of the stick insect genus Timema. The aim of the second part is to identify the genetic changes underlying transitions to asexuality in Timema parthenogens that recently derived from their sexual ancestors. These young asexual lineages occasionally produce males, which can be crossed to the females of the sexual sister species. Backcrosses then permit to introgress the genetic factors associated with parthenogenetic egg production into the sexual species, and for subsequent mapping via a quantitative trait locus approach. In the third part, artificial selection experiments are used to generate new asexual cricket and grasshopper lineages in the laboratory, by taking advantage of genetic variation for ‘spontaneous parthenogenesis’ observed in many sexually reproducing species. These experiments are designed to test whether obligate parthenogens can evolve gradually from sexual ancestors or whether transitions more likely occur via saltational steps. They will also reveal genetic correlations between the capacity for parthenogenesis and other life-history traits thereby developing further insights into causes and consequences of parthenogenesis.Understanding whether analogous genetic and developmental changes underlie asexuality in different lineages that evolved in parallel can shed light on the degree of evolutionary constraints in the transition from sexual reproduction to parthenogenesis and is therefore of prime importance to investigate the evolution of new asexual taxa and the outcome of competition between sexual and asexual lineages. Understanding the mechanisms favoring and constraining the transition from sexual reproduction to asexuality will allow us to gain novel insights into one of the major questions in evolutionary biology: why have sex?