3 resultados para sperm dichotomy

em DRUM (Digital Repository at the University of Maryland)


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Gemstone Team FISH

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ABSTRACT Title of Dissertation: A BETTER PLACE TO BE: REPUBLICANISM AS AN ALTENATIVE TO THE AUTHORITARIANISM-DEMOCRACY DICHOTOMY Christopher Ronald Binetti, Doctor of Philosophy, and 2016 Dissertation directed by: Dr. Charled Frederick Alford, Department of Government and Politics In this dissertation, I argue that in modern or ancient regimes, the simple dichotomy between democracies and autocracies/dictatorships is both factually wrong and problematic for policy purposes. It is factually wrong because regimes between the two opposite regime types exist and it is problematic because the either/or dichotomy leads to extreme thinking in terms of nation-building in places like Afghanistan. In planning for Afghanistan, the argument is that either we can quickly nation-build it into a liberal democracy or else we must leave it in the hands of a despotic dictator. This is a false choice created by both a faulty categorization of regime types and most importantly, a failure to understand history. History shows us that the republic is a regime type that defies the authoritarian-democracy dichotomy. A republic by my definition is a non-dominating regime, characterized by a (relative) lack of domination by any one interest group or actor, mostly non-violent competition for power among various interest groups/factions, the ability of factions/interest groups/individual actors to continue to legitimately play the political game even after electoral or issue-area defeat and some measure of effectiveness. Thus, a republic is a system of government that has institutions, laws, norms, attitudes, and beliefs that minimize the violation of the rule of law and monopolization of power by one individual or group as much as possible. These norms, laws, attitudes, and beliefs ae essential to the republican system in that they make those institutions that check and balance power work. My four cases are Assyria, Persia, Venice and Florence. Assyria and Persia are ancient regimes, the first was a republic and then became the frightening opposite of a republic, while the latter was a good republic for a long time, but had effectiveness issues towards the end. Venice is a classical example of a medieval or early modern republic, which was very inspirational to Madison and others in building republican America. Florence is the example of a medieval republic that fell to despotism, as immortalized by Machiavelli’s writings. In all of these examples, I test certain alternative hypotheses as well as my own.

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Males of many insect species feed their partner during courtship and mating. Studies of male nutrient donation in various systems have established that nuptial feeding has evolved mostly through sexual selection. Although there is extensive diversity in form, the function of nuptial gifts is typically limited to either facilitating copulation or increasing ejaculate transfer, depending on the time at which the gift is consumed by females. Unlike other insects, the Hawaiian swordtail cricket Laupala (Gryllidae: Trigonidiinae) exhibits serial transfer of nuptial gifts. Males transfer multiple spermless 'micro' spermatophores over several hours before mating at the end of the day (i.e. before the transfer of a single sperm-containing 'macro' spermatophore). By experimental manipulation of male microspermatophore donation, I tested several hypotheses pertaining to the adaptive significance of nuptial gifts in this system. I found that microspermatophore transfer improves insemination, by causing the female reproductive tract to take in more sperm. This result reveals a previously undocumented function for premating nuptial gift donation among insects. Enhanced sperm transfer due to microspermatophore donation may represent male manipulation or an internal mechanism of post-copulatory choice by females. I also performed experimental manipulation of male photoperiod to investigate how time and gender influence nuptial gift production and mating behavior. I found that the timing of mating is limited in males but not females and that the time of pair formation has consequences for the degree of nuptial gift donation, which suggests that both mating timing and microspermatophore number is important for male reproductive success. Finally, I observed the mating behavior of several trigonidiine taxa for a comparative analysis of sexual behavior and found that other genera also utilize spermless microspermatophores, which suggests that microspermatophore donation may be a common nuptial gift strategy among swordtail crickets. The elaborate nuptial feeding behavior of Hawaiian swordtail crickets prior to mating represents a newly discovered strategy to increase male insemination success rather than mating success. Based on this unexpected result, it is worth exploring whether courtship behaviors in other cricket or insect mating systems have also evolved to increase sperm uptake.