Biology

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Data for: Competing adaptations maintain non-adaptive variation in a wild cricket population
(2024) Rayner, Jack; Eichenberger, Franca; Bainbridge, Jessica; Zhang, Shangzhe; Zhang, Xiao; Yusuf, Leeban; Balenger, Susan; Gaggiotti, Oscar; Bailey, Nathan
Evolution of an adaptive behavior and its sensory receptors promotes eye regression in blind cavefish
(Springer Nature, 2013-07-11) Yoshizawa, Masato; O’Quin, Kelly E; Jeffery, William R
How and why animals lose eyesight during adaptation to the dark and food-limited cave environment has puzzled biologists since the time of Darwin. More recently, several different adaptive hypotheses have been proposed to explain eye degeneration based on studies in the teleost Astyanax mexicanus, which consists of blind cave-dwelling (cavefish) and sighted surface-dwelling (surface fish) forms. One of these hypotheses is that eye regression is the result of indirect selection for constructive characters that are negatively linked to eye development through the pleiotropic effects of Sonic Hedgehog (SHH) signaling. However, subsequent genetic analyses suggested that other mechanisms also contribute to eye regression in Astyanax cavefish. Here, we introduce a new approach to this problem by investigating the phenotypic and genetic relationships between a suite of non-visual constructive traits and eye regression. Using quantitative genetic analysis of crosses between surface fish, the Pachón cavefish population and their hybrid progeny, we show that the adaptive vibration attraction behavior (VAB) and its sensory receptors, superficial neuromasts (SN) specifically found within the cavefish eye orbit (EO), are genetically correlated with reduced eye size. The quantitative trait loci (QTL) for these three traits form two clusters of congruent or overlapping QTL on Astyanax linkage groups (LG) 2 and 17, but not at the shh locus on LG 13. Ablation of EO SN in cavefish demonstrated a major role for these sensory receptors in VAB expression. Furthermore, experimental induction of eye regression in surface fish via shh overexpression showed that the absence of eyes was insufficient to promote the appearance of VAB or EO SN. We conclude that natural selection for the enhancement of VAB and EO SN indirectly promotes eye regression in the Pachón cavefish population through an antagonistic relationship involving genetic linkage or pleiotropy among the genetic factors underlying these traits. This study demonstrates a trade-off between the evolution of a non-visual sensory system and eye regression during the adaptive evolution of Astyanax to the cave environment.
UNDERSTANDING MANAGED RETREAT THROUGH A MULTI-STAKEHOLDER LENS: A CASE STUDY ON THE LOWER EASTERN SHORE OF MARYLAND
(2021) Miralles, Andrea Maria; Paolisso, Michael J.; Alcañiz, Isabella; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Due to concerns about increasing sea levels and climate displacement, there has been a growing interest in the adaptation option of managed retreat. In managed retreat, shorelines move inland acting as a natural buffer to coastal climate impacts, while coastal communities move to higher ground through voluntary home buyouts. Managed retreat is also highly controversial, as it is poorly understood and presents significant challenges to equity. In order to address these issues, this thesis research provides a multi-stakeholder analysis on the Lower Eastern Shore of Maryland focused on understandings and trust in managed retreat processes. Key findings from this research are that communities, government and non-governmental organizations have different understandings of managed retreat, that retreat discussions need to occur at official levels now, that equity must be a central component of planning, that trust is necessary for successful retreat and that any future retreat must emphasize community agency and collaboration.
MOVING TOWARD AN OPTIMUM: THE ADAPTATION GENETICS OF ARABIDOPSIS THALIANA.
(2015) Stearns, Frank Warren; Fenster, Charles B; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
Adaptation accounts for many of the interesting characteristics of biodiversity. Despite this, the genetic mechanisms underlying the process of adaptation in nature are largely unknown. While general principles are emerging, important questions remain. Although experimental evidence has corroborated theoretical predictions, very few studies have tested macroorganisms in nature, where adaptation is most relevant. My dissertation addresses several important questions in adaptation genetics in the context of fitness landscapes, primarily using the model plant Arabidopsis thaliana. Fitness landscapes are used to visualize the relationship between genetics and fitness (evolutionary success of an individual). Although fitness landscapes have been considered metaphorical, recent work (and this dissertation) suggests they may approximate reality, providing testable predictions. I first assess pleiotropy (when one gene has multiple effects), an important component of fitness landscape models. I examine this concept in historical context and suggest future directions for research. Next I evaluate how well genetic relatedness corresponds to climate adaptation across the native range of A. thaliana and find support for parallel evolution (identical but independent genetic changes), suggesting that fitness landscapes are complex. In my next chapter, using a combination of natural and artificial conditions, I examine how induced mutations impact traits that are fitness indicators as compared to general traits. I find that new mutations tend to reduce fitness, whereas their effect on general traits is bidirectional. This result is more pronounced under stressful field conditions. Finally, I evaluate a mathematical model of adaptation in the field using induced mutations in A. thaliana. I find support for a previous result from laboratory studies - that lineages that are less well adapted to an environment are more likely to benefit from new mutations whereas lineages that are well adapted are more likely to be disrupted by new mutations - and extend that to the wild. Throughout I explore the importance of contingency in evolution, sometimes underscoring how it leads to unpredictable adaptation (chapters one and two), yet also demonstrating that the actions of mutations can be fit to simplifying assumptions (chapters three and four). These studies therefore significantly contribute to the emerging scholarship on adaptation genetics.

Biology

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