TY - JOUR A1 - Mitesser, Oliver A1 - Weissel, Norbert A1 - Strohm, Erhard A1 - Poethke, Hans-Joachim T1 - Adaptive dynamic resource allocation in annual eusocial insects: Environmental variation will not necessarily promote graded control N2 - Background: According to the classical model of Macevicz and Oster, annual eusocial insects should show a clear dichotomous "bang-bang" strategy of resource allocation; colony fitness is maximised when a period of pure colony growth (exclusive production of workers) is followed by a single reproductive period characterised by the exclusive production of sexuals. However, in several species graded investment strategies with a simultaneous production of workers and sexuals have been observed. Such deviations from the "bang-bang" strategy are usually interpreted as an adaptive (bet-hedging) response to environmental fluctuations such as variation in season length or food availability. To generate predictions about the optimal investment pattern of insect colonies in fluctuating environments, we slightly modified Macevicz and Oster's classical model of annual colony dynamics and used a dynamic programming approach nested into a recurrence procedure for the solution of the stochastic optimal control problem. Results: 1) The optimal switching time between pure colony growth and the exclusive production of sexuals decreases with increasing environmental variance. 2) Yet, for reasonable levels of environmental fluctuations no deviation from the typical bang-bang strategy is predicted. 3) Model calculations for the halictid bee Lasioglossum malachurum reveal that bet-hedging is not likely to be the reason for the graded allocation into sexuals versus workers observed in this species. 4) When environmental variance reaches a critical level our model predicts an abrupt change from dichotomous behaviour to graded allocation strategies, but the transition between colony growth and production of sexuals is not necessarily monotonic. Both, the critical level of environmental variance as well as the characteristic pattern of resource allocation strongly depend on the type of function used to describe environmental fluctuations. Conclusion: Up to now bet-hedging as an evolutionary response to variation in season length has been the main argument to explain field observations of graded resource allocation in annual eusocial insect species. However, our model shows that the effect of moderate fluctuations of environmental conditions does not select for deviation from the classical bang-bang strategy and that the evolution of graded allocation strategies can be triggered only by extreme fluctuations. Detailed quantitative observations on resource allocation in eusocial insects are needed to analyse the relevance of alternative explanations, e.g. logistic colony growth or reproductive conflict between queen and workers, for the evolution of graded allocation strategies. KW - Insekten KW - Fitness KW - Evolution KW - Sozialität KW - resource allocation KW - fitness KW - evolution KW - eusociality KW - insect Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-45412 ER - TY - JOUR A1 - Tomaszkiewicz, Marta A1 - Chalopin, Domitille A1 - Schartl, Manfred A1 - Galiana, Delphine A1 - Volff, Jean-Nicolas T1 - A multicopy Y-chromosomal SGNH hydrolase gene expressed in the testis of the platyfish has been captured and mobilized by a Helitron transposon JF - BMC Genetics N2 - Background: Teleost fish present a high diversity of sex determination systems, with possible frequent evolutionary turnover of sex chromosomes and sex-determining genes. In order to identify genes involved in male sex determination and differentiation in the platyfish Xiphophorus maculatus, bacterial artificial chromosome contigs from the sex-determining region differentiating the Y from the X chromosome have been assembled and analyzed. Results: A novel three-copy gene called teximY (for testis-expressed in Xiphophorus maculatus on the Y) was identified on the Y but not on the X chromosome. A highly related sequence called texim1, probably at the origin of the Y-linked genes, as well as three more divergent texim genes were detected in (pseudo) autosomal regions of the platyfish genome. Texim genes, for which no functional data are available so far in any organism, encode predicted esterases/lipases with a SGNH hydrolase domain. Texim proteins are related to proteins from very different origins, including proteins encoded by animal CR1 retrotransposons, animal platelet-activating factor acetylhydrolases (PAFah) and bacterial hydrolases. Texim gene distribution is patchy in animals. Texim sequences were detected in several fish species including killifish, medaka, pufferfish, sea bass, cod and gar, but not in zebrafish. Texim-like genes are also present in Oikopleura (urochordate), Amphioxus (cephalochordate) and sea urchin (echinoderm) but absent from mammals and other tetrapods. Interestingly, texim genes are associated with a Helitron transposon in different fish species but not in urochordates, cephalochordates and echinoderms, suggesting capture and mobilization of an ancestral texim gene in the bony fish lineage. RT-qPCR analyses showed that Y-linked teximY genes are preferentially expressed in testis, with expression at late stages of spermatogenesis (late spermatids and spermatozeugmata). Conclusions: These observations suggest either that TeximY proteins play a role in Helitron transposition in the male germ line in fish, or that texim genes are spermatogenesis genes mobilized and spread by transposable elements in fish genomes. KW - sex determination KW - testis KW - Y chromosome KW - rolling-circle transposons KW - factor acetylhydrolase activity KW - platelet activation factor KW - xiphophorus maculatus KW - oryzias-latipes KW - sequence alignment KW - DM-domain gene KW - sex-determining region KW - evolution KW - fish KW - SGNH hydrolase KW - helitron KW - transposition KW - platyfish KW - sex chromosomes Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-116746 VL - 15 IS - 44 ER - TY - JOUR A1 - Biscotti, Maria Assunta A1 - Adolfi, Mateus Contar A1 - Barucca, Marco A1 - Forconi, Mariko A1 - Pallavicini, Alberto A1 - Gerdol, Marco A1 - Canapa, Adriana A1 - Schartl, Manfred T1 - A comparative view on sex differentiation and gametogenesis genes in lungfish and coelacanths JF - Genome Biology and Evolution N2 - Gonadal sex differentiation and reproduction are the keys to the perpetuation of favorable gene combinations and positively selected traits. In vertebrates, several gonad development features that differentiate tetrapods and fishes are likely to be, at least in part, related to the water-to-land transition. The collection of information from basal sarcopterygians, coelacanths, and lungfishes, is crucial to improve our understanding of the molecular evolution of pathways involved in reproductive functions, since these organisms are generally regarded as “living fossils” and as the direct ancestors of tetrapods. Here, we report for the first time the characterization of >50 genes related to sex differentiation and gametogenesis in Latimeria menadoensis and Protopterus annectens. Although the expression profiles of most genes is consistent with the intermediate position of basal sarcopterygians between actinopterygian fish and tetrapods, their phylogenetic placement and presence/absence patterns often reveal a closer affinity to the tetrapod orthologs. On the other hand, particular genes, for example, the male gonad factor gsdf (Gonadal Soma-Derived Factor), provide examples of ancestral traits shared with actinopterygians, which disappeared in the tetrapod lineage. KW - sex differentiation KW - Latimeria menadoensis KW - Protopterus annectens KW - evolution KW - testis KW - gametogenesis KW - ovary Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-176774 VL - 10 IS - 6 ER -