Home About us Contact
|
Home About us Contact | ||
|
|
||
Own Population (own + population)
Selected AbstractsTHE EVOLUTION OF PREMATING ISOLATION: LOCAL ADAPTATION AND NATURAL AND SEXUAL SELECTION AGAINST HYBRIDSEVOLUTION, Issue 5 2004Maria R. Servedio Abstract Although reinforcement is ostensibly driven by selection against hybrids, there are often other components in empirical cases and theoretical models of reinforcement that may contribute to premating isolation. One of these components is local adaptation of a trait used in mate choice. I use several different comparisons to assess the roles that local adaptation and selection against hybrids may play in reinforcement models. Both numerical simulations of exact recursion equations and analytical weak selection approximations are employed. I find that selection against hybrids may play a small role in driving preference evolution in a reinforcement model where the mating cue is separate from loci causing hybrid incompatibilities. When females have preferences directly for purebreds of their own population, however, selection against hybrids can play a large role in premating isolation evolution. I present some situations in which this type of selection is likely to exist. This work also illustrates shortfalls of using a weak selection approach to address questions about reinforcement. [source] Reproductive performance of clonal and sexual bark beetles (Coleoptera: Scolytidae) in the fieldJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2000Løyning In Ips acuminatus (Gyll.) parthenogenetic females occur together with sexual females and with sexual males upon which they depend for sperm. In a reciprocal-transplant experiment, I studied fecundity differences among parthenogenetic and sexual females from two populations that differ dramatically in the proportion of clonal females. In a second experiment, I studied competition between larvae from different mothers and between females from the two source populations. Fecundity measured by the number of eggs per egg tunnel was influenced by the ambient environment at the sites of the experiment as well as the origin of the female, and was generally higher for clonal than for sexual females at both sites. In experimental groups where larvae competed with larvae from their own population (pure treatments), the number of surviving pupae was significantly lower than in groups where females from the two source populations were mixed. The high fecundity of clonal females makes coexistence of the two types of females difficult to explain. It makes the reproductive advantage associated with clonality in I. acuminatus even higher than the two-fold difference due to asexuality per sé. The significant differences in the number of pupae in mixed vs. pure groups suggest ecological divergence between sexual and clonal females. This would make the mortality of larvae not only density dependent, but also frequency dependent, which could explain the coexistence of sexual and clonal females. [source] Learning to Cooperate: Learning Networks and the Problem of AltruismAMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 3 2009John T. Scholz We explore how two populations learn to cooperate with each other in the absence of institutional support. Individuals play iterated prisoner's dilemmas with the other population, but learn about successful strategies from their own population. Our agent-based evolutionary models reconfirm that cooperation can emerge rapidly as long as payoffs provide a selective advantage for nice, retaliatory strategies like tit-for-tat, although attainable levels of cooperation are limited by the persistence of nonretaliatory altruists. Learning processes that adopt the current best response strategy do well only when initial conditions are very favorable to cooperation, while more adaptive learning processes can achieve high levels of cooperation under a wider range of initial conditions. When combined with adaptive learning, populations having larger, better connected learning relationships outperform populations with smaller, less connected ones. Clustered relationships can also enhance cooperation, particularly in these smaller, less connected populations. [source] Sexual Dysfunction after Rectal Surgery: A Retrospective Study of Men without Disease RecurrenceTHE JOURNAL OF SEXUAL MEDICINE, Issue 9 2010Vahudin Zugor MD ABSTRACT Introduction., Sexual dysfunction is a frequent complication of visceral surgery after rectal resections as a result of carcinoma of the rectum. Aim., The purpose of our study is to assess the incidence and form of sexual dysfunction in our own population of patients. Methods., The study comprised all patients who had undergone surgery for carcinoma of the rectum at the Erlangen Surgery University Hospital, Germany, in the period 2000,04. All male patients were retrospectively surveyed and asked to complete standardized (International Index of Erectile Function 15) questionnaires regarding their pre- and postsurgical sexual function. One hundred and forty-five questionnaires could be analyzed. The statistical evaluation was conducted with aid of the SPSS statistics program. The univariate analysis was carried out with the chi-square test and the U -test (Mann,Whitney Test). Main Outcome Measures., Erectile dysfunction, libido, and ability to have and sustain ejaculation and orgasm (both before and after surgery in each case) were among the dependent variables when compiling the data. The impact various surgical procedures and radiochemotherapy had on the severity of the sexual dysfunctions was analyzed. The scope of the postoperative urological care given was also assessed. Results., Erectile dysfunction was confirmed in N = 112 patients (77.3%) after surgery (P -value < 0.001). Other parameters such as orgasm capacity (4.1% vs. 16.5%), ejaculation ability (1.4% vs. 12.4%) and libido (3.4% vs. 22%) also showed a marked deterioration postoperatively. Postoperative erectile dysfunction was present in 77% of the patients with a colostomy and in 88.5% of the patients who had received neoadjuvant radiation. Conclusions., Male erectile dysfunction is a frequent complication after rectal resection as a result of carcinoma of the rectum. The high incidence of sexual dysfunctions results from the radical nature of the procedure and from additional radiation or colostomy therapy. These patients need accompanying urological care for treatment of their sexual dysfunction. Zugor V, Miskovic I, Lausen B, Matzel K, Hohenberger W, Schreiber M, Labanaris AP, Neuhuber W, Witt J, and Schott GE. Sexual dysfunction after rectal surgery: A retrospective study of men without disease recurrence. J Sex Med 2010;7:3199,3205. [source] The Elephant in the Living Room That No One Wants to Talk About: Why U.S. Anthropologists Are Unable to Acknowledge the End of CultureANTHROPOLOGY & EDUCATION QUARTERLY, Issue 1 2009Greg Tanaka Findings from a four-year action research project at a highly diverse, West Coast U.S. university reveal that a large percentage of white students cannot trace their identities to a particular nation in Europe and are, as a result, unable to name the shared meanings of a particular ethnic culture. Each time Latino, Asian American, and African American classmates describe their families' ethnic histories, it is the European American student who feels dissociated. Extracted from a polyphonic novelistic ethnography, this essay focuses on an exchange among three students at a town hall meeting and explores the ramifications for social cohesion when members of "the dominant group" appear to be experiencing declining subjectivity. This reflection also raises two larger disciplinary questions: (1) How can 10,000 U.S. anthropologists continue to deploy the concept of culture at field sites outside the United States when so many in their own population cannot claim an ethnic culture of their own? and (2) Given the recent turn in events in the U.S. political scene, shouldn't anthropologists now begin developing new constructs for social analysis after race and culture?,[culture concept, subjectivity, soul] [source] GEOGRAPHIC VARIATION OF GENETIC AND BEHAVIORAL TRAITS IN NORTHERN AND SOUTHERN TÚNGARA FROGSEVOLUTION, Issue 8 2006Heike Pröhl Abstract We use a combination of microsatellite marker analysis and mate-choice behavior experiments to assess patterns of reproductive isolation of the túngara frog Physalaemus pustulosus along a 550-km transect of 25 populations in Costa Rica and Panama. Earlier studies using allozymes and mitochondrial DNA defined two genetic groups of túngara frogs, one ranging from Mexico to northern Costa Rica (northern group), the second ranging from Panama to northern South America (southern group). Our more fine-scale survey also shows that the northern and southern túngara frogs are genetically different and geographically separated by a gap in the distribution in central Pacific Costa Rica. Genetic differences among populations are highly correlated with geographic distances. Temporal call parameters differed among populations as well as between genetic groups. Differences in calls were explained better by geographic distance than by genetic distance. Phonotaxis experiments showed that females preferred calls of males from their own populations over calls of males from other populations in about two-thirds to three-fourths of the contrasts tested. In mating experiments, females and males from the same group and females from the north with males from the south produced nests and tadpoles. In contrast, females from the south did not produce nests or tadpoles with males from the north. Thus, northern and southern túngara frogs have diverged both genetically and bioacoustically. There is evidence for some prezygotic isolation due to differences in mate recognition and fertilization success, but such isolation is hardly complete. Our results support the general observation that significant differences in sexual signals are often not correlated with strong genetic differentiation. [source] Sustaining the Ark: the challenges faced by zoos in maintaining viable populationsINTERNATIONAL ZOO YEARBOOK, Issue 1 2009C. M. LEES In the World Zoo and Aquarium Conservation Strategy, the world's leading zoos commit to focusing their efforts on conserving wildlife. Such a commitment is made as human activities are driving many species of wildlife towards extinction. The world's leading zoos aim to act as a counterbalance to activities that undermine the sustainability of wild populations of threatened species. However, to date, this same group of zoos has largely failed to manage its own populations of wildlife sustainably despite distinguished calls to action over the past 25 years, significant scientific input and much organizational effort. This paper explores the efforts of the global zoo community to bring sustainability and conservation value to its animal populations. It looks at where we have come from, where we are now and where we need to go from here. [source] The failure of pronatalism in developed states ,with cultural,ethnic hegemony': the Israeli lessonPOPULATION, SPACE AND PLACE (PREVIOUSLY:-INT JOURNAL OF POPULATION GEOGRAPHY), Issue 2 2008O. Winckler Abstract During the past two decades, the ,hot' demographic issue in the developed states ,with cultural,ethnic hegemony' changed radically , from a focus on ,global demographic pressure', namely, the ,Malthusian syndrome' of rapid population growth in the developing countries, to the ethno-religious composition of their own populations. The solution adopted by many of these countries to tackle the twin demographic challenges of population ageing and the changing dependency ratio was the implementation of pronatalist policies which aimed at reducing their dependence upon labour immigration. This article examines the efficiency of these pronatalist policies through the Israeli case. The core questions of the article are: Has the Israeli pronatalist policy achieved its basic aims? What influence did the Israeli natalist policy and the child allowance structure have on the fertility patterns of the Israeli-Arabs? What can be learned from the Israeli experience regarding the efficiency of these pronatalist policies in developed states? The major lesson from the Israeli experience is that, to a large extent, these pronatalist polices failed. The fertility rate of the Jewish middle class, the Christian-Arabs and the Druze steadily declined, while that of the Israeli-Muslims, although lower since the 1960s, is still twice that of the Jewish middle class. One can find a similar situation in all of the developed states ,with cultural,ethnic hegemony.' Thus, the inescapable conclusion is that in democratic-developed societies, in which women enjoy equity in every respect, fertility rates will eventually decline to below replacement-level regardless of pronatalist financial benefits. Consequently, the process of the developed states ,with cultural,ethnic hegemony' becoming developed states ,without cultural,ethnic hegemony' is irreversible due to the constant need for massive labour immigration. In the case of Israel, at the dawn of the twenty-first century, there are high fertility rates in only two communities , the Ultra-Orthodox Jews and the Muslims , paradoxically the two ,non-Zionist' communities. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||