01783nas a2200193   4500008004100000245011700041210006900158300001000227490000700237520107400244653001801318653002101336653002001357653001601377653001401393100002301407700002201430856013701452       1999                        eng d00aHormonal control of male horn lenght dimorphism in the dung beetle Onthophagus taurus (Coleoptera: Scarabaeidae)0 aHormonal control of male horn lenght dimorphism in the dung beet  a45-530 v453 aMale dung beetles (Onthophagus taurus) facultatively produce a pair of horns that extend from the base of the head: males growing larger than a threshold body size develop long horns, whereas males that do not achieve this size grow only rudimentary horns or no horns at all. Here we characterize the postembryonic development of these beetles, and begin to explore the hormonal regulation of horn growth. Using radioimmune assays to compare the ecdysteroid titers of horned males, hornless males, and females, we identify a small pulse of ecdysteroid which is present in both hornless males and females, but not in horned males. In addition, we identify a brief period near the end of the final (third) larval instar when topical applications of the juvenile hormone analog methoprene can switch the morphology of developing males. Small, normally hornless, males receiving methoprene during this sensitive period were induced to produce horns in 80% of the cases. We summarize this information in two models for the hormonal control of male dimorphism in horn length.10aHorned beetle10aJuvenile hormone10amale dimorphism10aPolyphenism10aThreshold1 aEmlen, Douglas, J.1 aNijhout, Frederik  uhttps://scarabnet.myspecies.info/hormonal-control-male-horn-lenght-dimorphism-dung-beetle-onthophagus-taurus-coleoptera-scarabaeidae02675nas a2200193   4500008004100000245010000041210006900141300000900210490000600219520196900225653003702194653001802231653002602249653001602275653002102291100002202312700002202334856012502356       2006                        eng d00aHorn possession reduces maneuverability in the horn-polyphenic beetle, Onthophagus nigriventris0 aHorn possession reduces maneuverability in the hornpolyphenic be  a1-100 v63 aAlternative male morphologies are common in a wide range of organisms and particularly extreme in horned beetles. Here, large males (majors) commonly develop extravagant weaponry such as horns or enlarged mandibles, whereas small males (minors) develop only rudimentary traits. In some taxa, including the genusOnthophagus, the transition from minors to majors occurs over a very small range of body sizes causing intermediate morphologies to be rare or absent from natural populations. Several studies have shown that majors use horns as weapons during male combat over females and that the possession of horns increases male fighting success, and presumably fitness. However, the advantages of a hornless morphology, if any, have remained elusive. Here the alternative male morphs are examined in the horn-polyphenic beetleOnthophagus nigriventris. In particular, the hypothesis was tested that lack of horns in minors increases their maneuverability inside tunnel systems in which these males sneak matings from major males. Using a simple behavioral assay the effects of horn possession on maneuverability were quantified inside an artificial tunnel. Minors were found to be significantly more mobile compared to majors. No such differences were found in mobility between similarly small and large females, which always lack horns. This suggests that mobility differences observed among male morphs are due to the presence or absence of horns rather than differences in body size. This notion was further supported in a second experiment in which surgical removal of horns significantly improved maneuverability, while subsequent re-attachment of horns reversed this effect. These results suggest that lack of horns increases male maneuverability inside tunnels and may thus be advantageous in the context of the particular social niche inhabited by minor males. The results are discussed in the context of the evolutionary ecology of horn-polyphenic beetles. 10aALTERNATIVE REPRODUCTIVE TACTICS10aHorned beetle10aphenotypic plasticity10aPolyphenism10asexual selection1 aMadewell, Richard1 aMoczek, Armin, P.  uhttps://scarabnet.myspecies.info/horn-possession-reduces-maneuverability-horn-polyphenic-beetle-onthophagus-nigriventris02061nas a2200205   4500008004100000245010100041210006900142260000800211300001400219490000700233520134300240653001301583653001801596653001601614653003401630653001501664100002301679700002201702856013101724       2008                        eng d00aRapid antagonistic coevolution between primary and secondary sexual characters in horned beetles0 aRapid antagonistic coevolution between primary and secondary sex  csep  a2423-24280 v623 aDifferent structures may compete during development for a shared and limited pool of resources to sustain growth and differ- entiation. The resulting resource allocation trade-offs have the potential to alter both ontogenetic outcomes and evolutionary trajectories. However, little is known about the evolutionary causes and consequences of resource allocation trade-offs in natural populations. Here, we explore the significance of resource allocation trade-offs between primary and secondary sexual traits in shaping early morphological divergences between four recently separated populations of the horned beetle Onthophagus taurus as well as macroevolutionary divergence patterns across 10 Onthophagus species. We show that resource allocation trade-offs leave a strong signature in morphological divergence patterns both within and between species. Furthermore, our results suggest that genital divergence may, under certain circumstances, occur as a byproduct of evolutionary changes in secondary sexual traits. Given the importance of copulatory organ morphology for reproductive isolation our findings begin to raise the possibility that secondary sexual trait evolution may promote speciation as a byproduct. We discuss the implications of our results on the causes and consequences of resource allocation trade-offs in insects. 10aAedeagus10aHorned beetle10aOnthophagus10aresource allocation trade-off10aspeciation1 aParzer, Harald, F.1 aMoczek, Armin, P.  uhttps://scarabnet.myspecies.info/rapid-antagonistic-coevolution-between-primary-and-secondary-sexual-characters-horned-beetles