Browsing by Subject "novelty"

Now showing 1 - 3 of 3
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    Causes and consequences of evolutionary innovation: An experimental approach to evaluating assumptions and predictions in macroevolutionary theory
    (2020-01) Gettle, Noah
    It has long been noted that there are some adaptations that appear to have played a disproportionate role in determining the evolutionary trajectories of the clades in which they arose. These adaptations, often termed evolutionary innovations, are often associated with increases in diversity and expansions into new niche spaces. The historic nature of evolutionary innovations, however, largely limit our ability to draw conclusions about causes and consequences, leaving broad-scale explanations constrained to theory. Using the power of experimental evolution, this work aims to explore empircally theories concerning the origins and evolutionary consequences of innovations. I used one proposed innovation, multicellularity, a trait that reliably arises in brewers’ yeast (Saccharomyces cerevisiae) under certain selective conditions. Using genomic tools, I show that despite their disruptive nature, loss-of-function mutations in largely “non-regulatory genes” are the major causal genetic changes underpinning convergent evolution of experimental yeast populations toward multicellularity. I further show that one of these mutations is also associated with major transcriptional and physiological effects one of which, increased apoptosis, has been previously described as a multicellular adaptation. Data presented here suggests this is less likely a direct effect of loss of gene activity than of microenvironmental shifts associated with a multicellular lifestyle. Finally, I present research that suggests that adaptive responses to environmental challenges often associated with complex multicellularity, such as division of labor, may not represent optimal fitness solutions but rather reflect a balance between the costs and benefits of retained multicellularity. In sum, my results reveal that current theories regarding multicellularity as well as other innovations may, at best, be incomplete and that generalizations about causes and consequences of evolutionary innovations may prove more difficult to come by than many have suggested.
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    The costs (and benefits) of standing out: Alternative reproductive behavior and novel trait evolution in the Pacific field cricket
    (2021-07) Olzer, Rachel
    Conspicuous animal signals are often under conflicting selection, with higher performance in one fitness component of life history diminishing performance in another component. The diversity of animal signals in nature suggests that novelty- a new structure or property of an organism that allows it to perform a different function, thus opening a new ‘adaptive zone’ is an important, but often overlooked aspect of signal evolution. The evolution of novelty has largely been absent from conversations about how diversity arises and how it can be maintained. This work seeks to examine both the causes and consequences of novel trait evolution. From individual behaviors to population-level dynamics, I have employed various methodologies for answering a decades-long question in evolutionary biology: how are novel traits accommodated in natural populations?
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    Exploring the Balance Between Novelty and Familiarity in Recommendation Systems
    (2018-09) Kumar, Vikas
    The balance users seek between the comfort of familiar recommendations and the excitement they solicit in novel ones is a challenge for recommendation systems. On the one hand, familiar options help improve the trust and confidence of users in the system. On the other hand, novel options play a key role in providing serendipity - the delightful surprise that makes system more engaging and useful. However, in their pursuit to achieve the delicate balance, existing recommendation techniques have overlooked user-specific needs and assumed that users have the same, constant appetite for the amount of novelty and familiarity in their recommendations. This thesis highlights and emphasizes the dynamics in user consumption of familiar versus novel items and explores the balance between the two in recommendations. Studying users' consumption patterns in online music streaming we first show that users have distinct and dynamic appetites for novelty in their consumption. We show how a recommender adaptive to the varying appetite of users' novelty consumption is more accurate than traditional one-size-fits-all approaches. Second, we show that not only do users have a distinct appetite, but that there exists a systematic relationship between the novel items they consume and the time elapsed between successive sessions. Third, we address the limitations of inferences from activity logs and the assumptions we impose on actions taken by users in developing algorithms. Instead, we use a qualitative approach in which we interview users while they engage in music listening in their everyday environments to identify how a combination of factors, such as attention needs, exposure to artists or songs etc., influence the balance users seek between novelty and familiarity in their selection. Finally, apart from analysis of what users consume, this thesis also demonstrates the implications of individual familiarity and novelty on the content users produce in online social platforms. Analyzing online location-tagged photos shared by users on Flickr and the familiarity of the users with a location, we show that the locals, who are more familiar with a location, capture more diverse photos of the location, yet it is the tourists who, in their short stay and being less familiar, capture more representative photos of the location. The thesis aims to provide a guiding tool to define, measure, and model the dynamics of the familiarity and novelty balance users consume on online media platforms. The simplicity of our method and its ability to be embedded within existing recommendation techniques supports the contribution of this thesis as well as its general adaptability to other domains of user interactions.