A geographic cline induced by negative frequency-dependent selection

<p>Abstract</p> <p>Background</p> <p>Establishment of geographic morph frequency clines is difficult to explain in organisms with limited gene flow. Balancing selection, such as negative frequency-dependent selection (NFDS), is instead suggested to establish a morph frequency cline on a geographic scale at least theoretically. Here we tested whether a large-scale smooth cline in morph frequency is established by NFDS in the female-dimorphic damselfly, <it>Ischnura senegalensis</it>, where andromorphs and gynomorphs are maintained by NFDS.</p> <p>Results</p> <p>We found a large-scale latitudinal cline in the morph frequency: andromorph frequency ranged from 0.05 (South) to 0.79 (North). Based on the empirical data on the numbers of eggs, the number of ovariole, abdomen length and latitude, the potential fitness of andromorphs was estimated to be lower than that of gynomorphs in the south, and higher in the north, suggesting the gene-by-environment interaction. From the morph-specific latitudinal cline in potential fitness, the frequency of andromorphs was expected to shift from 0 to 1 without NFDS, because a morph with higher potential fitness wins completely and the two morphs will switch at some point. In contrast, NFDS led to the coexistence of two morphs with different potential fitness in a certain geographic range along latitude due to rare morph advantage, and resulted in a smooth geographic cline of morph frequency.</p> <p>Conclusion</p> <p>Our results provide suggestive evidence that the combination of NFDS and gene-by-environment interaction, i.e., multi-selection pressure on color morphs, can explain the geographic cline in morph frequency in the current system.</p

Visual Predators Select for Crypticity and Polymorphism in Virtual Prey

Cryptically colored animals commonly occur in several distinct pattern variants. Such phenotypic diversity may be promoted by frequency-dependent predation, in which more abundant variants are attacked disproportionately often, but the hypothesis has never been explicitly tested. Here we report the first controlled experiment on the effects of visual predators on prey crypticity and phenotypic variance, in which blue jays (Cyanocitta cristata) searched for digital moths on computer monitors. Moth phenotypes evolved via a genetic algorithm in which individuals detected by the jays were much less likely to reproduce. Jays often failed to detect atypical cryptic moths, confirming frequency- dependent selection and suggesting the use of searching images, which enhance the detection of common prey. Over successive generations, the moths evolved to become significantly harder to detect, and they showed significantly greater phenotypic variance than non-selected or frequency-independent selected controls

Leadership, governance and management in dental education - new societal challenges.

Dental schools around the world face new challenges that raise issues with regard to how they are governed, led and managed. With rapid societal changes, including globalization and consumerism, the roles of universities and their funding have become intensely debated topics. When financial burdens on universities increase, so does the pressure on dental schools. This is exacerbated by the relative expense of running dental schools and also by the limited understanding of both university managers and the public of the nature and scope of dentistry as a profession. In these circumstances, it is essential for dental schools to have good systems of leadership and management in place so that they can not only survive in difficult times, but flourish in the longer term. This paper discusses the concept of governance and how it relates to leadership, management and administration in dental schools and hospitals. Various approaches to governance and management in dental schools on different continents and regions are summarized and contrasted. A number of general governance and leadership issues are addressed. For example, a basic principle supported by the Working Group is that an effective governance structure must link authority and responsibility to performance and review, i.e. accountability, and that the mechanism for achieving this should be transparent. The paper also addresses issues specific to governing, leading and managing dental schools. Being a dean of a modern dental school is a very demanding role and some issues relating to this role are raised, including: dilemmas facing deans, preparing to be dean and succession planning. The importance of establishing a shared vision and mission, and creating the right culture and climate within a dental school, are emphasized. The Working Group advocates establishing a culture of scholarship in dental schools for both teaching and research. The paper addresses the need for effective staff management, motivation and development, and highlights the salience of good communication. The Working Group suggests establishing an advisory board to the dean and school, including lay persons and other external stakeholders, as one way of separating governance and management to some extent and providing some checks and balances within a dental school. Several other suggestions and recommendations are made about governance, management and leadership issues, including the need for schools to promote an awareness of their roles by good communication and thereby influence perceptions of others about their roles and values