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Deep Phosphorus Banding in Winter Wheat: A risk management tool for the Southern Great Plains
No full textMorphological Trends in Experimental and Simulated Populations of Hybrid Swordtails
Get PDFNaturally hybridizing species represent important study systems in evolutionary biology, providing insight into the mechanisms that drive reproductive isolation and speciation. One such system involves the swordtails Xiphophorus malinche and X. birchmanni, which have formed several replicated hybrid zones oriented around elevational gradients in the drainages of the Rio Calnali in eastern Mexico. As such, this system presents a unique opportunity to study the relationship between natural and sexual selection in guiding hybrid evolution. However, these natural populations are characterized by several generations of natural and sexual selection. To gain a better understanding of how early generation hybrids morphologically evolve across different ecological environments over time, this project monitored and simulated replicated experimental early generation hybrid populations along an elevational gradient, collecting and analyzing morphological data to compare against trait values simulated under several theoretical scenarios. Simulations were designed to accurately mirror up to date knowledge on the Xiphophorus genome, including several recently published QTLs associated with traits of interest. Informed by the life history of parental species and hybrids, a variety of natural and sexual selection functions were implemented. Both empirical and simulated datasets were tested for significant effects of time and elevation on phenotype. Preliminary analysis of empirical data suggests decreasing trends in several morphometric traits, as well as apparent oscillations in a species diagnostic trait which may be seasonally influenced. Simulations intended to replicate Fisherian runaway selection demonstrate that such processes are reinforced when polygenic preference and sexually selected traits are paired with traits under active ecological selection. Comparative analysis of simulated and empirical datasets using a mean error methodology identifies simulations implementing natural selection of an intermediate increment as best fitting the empirical dataset, though there are several indications that the simulations designed do not effectively capture all aspects of variation in the empirical system
Forage Production Under Drought Conditions
No full textDryland Crop Management Strategies During Prolonged Drought in the Texas High Plain
