Oogenesis in Unisexual Whiptail Lizards (genus Aspidoscelis)

Parthenogenesis is a reproductive mode that does not require males. Though theoretically advantageous, its rarity among metazoans suggests otherwise. Paradoxically, some unisexual species within the genus Aspidoscelis appear to be thriving by reproducing through obligate parthenogenesis. Formed via hybridization between different bisexual species, these lizards apparently reap the benefits of both hybrid vigor and higher reproductive potential. Previous studies have demonstrated the high degree of heterozygosity between generations, which contributes to the success of these lineages; a loss of heterozygosity would likely be accompanied by a decrease in fitness. How meiosis is modified in these animals is unknown. The predominant hypothesis suggests that endoreplication takes place prior to meiosis, resulting in a two-fold increase in DNA; however this has not been definitively shown. Further, the downstream modifications that result in a heterozygous gamete have merely been speculated upon. In the following thesis, meiosis within three parthenogenetic species is investigated. Quantification of DNA in germinal vesicles of the diploid parthenogen A. tesselata and the bisexual species A. gularis demonstrated that the parthenogen contains two-fold more DNA, despite equivalent somatic cell ploidy. Chiasmata were present on diplotene-stage chromosomes in both species, indicating that recombination is not bypassed. Additionally, synaptonemal complexes were found during pachytene in each species. Maintenance of heterozygosity is highly dependent on chromosome pairing in the parthenogen. Pairing between homologous chromosomes would result in a decrease; whereas pairing between identical (sister) chromosomes resulting from the additional DNA doubling event would preserve heterozygosity. Using homolog specific FISH probes in the parthenogen A. neomexicana, sister chromosome pairing is revealed. Thus, sister chromosome pairing after an additional DNA doubling allows for maintenance of heterozygosity in Aspidoscelis parthenogens. Secondly, four self-sustaining lineages of a new tetraploid species were generated from the mating between the diploid bisexual species Aspidoscelis inornata and triploid parthenogen A. exsanguis. The identity of these hybrids was confirmed by genotyping analysis. Females retain the ability to reproduce parthenogenetically through the doubling mechanism described in diploid species. These tetraploids have demonstrated how ploidy elevation hypothetically occurs in natural parthenogens. The mechanisms described in this thesis may be utilized in other parthenogens. Recent findings and future directions based on this work are presented

Practicum Pairs: An Alternative for First Field Experience in Early Childhood Teacher Education

This paper focuses on partnership between pairs of students in early childhood education during a teaching practicum in preschools and kindergartens. One hundred students enrolled in early childhood preservice teacher education programs at a large metropolitan Australian University were paired and placed in kindergartens and preschools with host teachers. The project aimed to explore the perceptions and experiences of host teachers and students involved in the paired practicum which was evaluated qualitatively using semi-structured surveys of host teachers and students. This paper identifies eight practices and two principles making this paired practicum successful or not successful

Experience matters: Females use smell to select experienced males for paternal care

Mate choice and mating preferences often rely on the information content of signals exchanged between potential partners. In species where a female's reproduction is the terminal event in life it is to be expected that females choose high quality males and assess males using some honest indicator of male quality. The Nereidid polychaete, Neanthes acuminata, exhibits monogamous pairing and the release of eggs by females terminates her life and larval success relies entirely on a male's ability to provide paternal care. As such females should have developed reliable, condition-dependent criteria to choose mates to guarantee survival and care for offspring. We show that females actively chose males experienced in fatherhood over others. In the absence of experienced males dominance, as evident from male-male fights, is utilized for mate selection. The preference for experienced males is not affected by previous social interactions between the individuals. We show that the choice of the partner is based on chemical signals demonstrating a 'scent of experience' to females providing evidence for the role of chemical signals in sexual selection for paternal care adding to our understanding of the mechanisms regulating condition-dependent mate choice

Harness the Power of Frontline Supervisors to Turn HR Policies into Performance Gains

Key Findings: • Frontline supervisors play a critical role in implementing HR policies by developing employees and managing performance. • Coaching counts—one-on-one feedback from frontline supervisors increases the bottom-line by improving individual productivity. • Coaching alone isn’t enough. It is much more effective when combined with other management practices—for example, group incentives that enhance collaborative problem-solving and learning, and reinforce the lessons from individual coaching. • The resources and constraints of workplace technologies can affect the return on your frontline coaching and HR management strategies. Don’t overlook the level of process automation and rate of technical change on the job

Lights, Camera, Action! Exploring Effects of Visual Distractions on Completion of Security Tasks

Human errors in performing security-critical tasks are typically blamed on the complexity of those tasks. However, such errors can also occur because of (possibly unexpected) sensory distractions. A sensory distraction that produces negative effects can be abused by the adversary that controls the environment. Meanwhile, a distraction with positive effects can be artificially introduced to improve user performance. The goal of this work is to explore the effects of visual stimuli on the performance of security-critical tasks. To this end, we experimented with a large number of subjects who were exposed to a range of unexpected visual stimuli while attempting to perform Bluetooth Pairing. Our results clearly demonstrate substantially increased task completion times and markedly lower task success rates. These negative effects are noteworthy, especially, when contrasted with prior results on audio distractions which had positive effects on performance of similar tasks. Experiments were conducted in a novel (fully automated and completely unattended) experimental environment. This yielded more uniform experiments, better scalability and significantly lower financial and logistical burdens. We discuss this experience, including benefits and limitations of the unattended automated experiment paradigm

Pair programming and the re-appropriation of individual tools for collaborative software development

Although pair programming is becoming more prevalent in software development, and a number of reports have been written about it [10] [13], few have addressed the manner in which pairing actually takes place [12]. Even fewer consider the methods used to manage issues such as role change or the communication of complex issues. This paper highlights the way resources designed for individuals are re-appropriated and augmented by pair programmers to facilitate collaboration. It also illustrates that pair verbalisations can augment the benefits of the collocated team, providing examples from ethnographic studies of pair programmers 'in the wild'