Adaptive Inertia Caused by Hidden Pleiotropic Effects

Population Bottlenecks Increase Additive Genetic Variance But Do Not Break a Selection Limit in Rain Forest Drosophila

“…Additionally, artificial selection may have been opposed by natural selection on this trait in the laboratory, particularly as the bottlenecking procedure would have exposed recessives with deleterious effects on fitness-related traits; if antagonistic natural selection is important, selecting every second generation may have exaggerated this effect. Hidden pleiotropic effects inducing stabilizing selection on one character may hinder directional selection on another (Baatz and Wagner 1997). Furthermore, genetic interactions with other traits can also limit selection responses even when V A is present (Blows and Hoffmann 2005).…”

The fall and rise of Dr Pangloss: adaptationism and the Spandrels paper 20 years later

“…More complex and more realistic models have proven too difficult for easy mathematical tractability. The currently accepted generalization is that complex genotypic architectures are less, not more, amenable to being altered by natural selection 13 , that is, constraints are indeed a common and inescapable feature of living systems 14 . However, the debate still rages around how much genetic information is necessary to include in models of evolutionary trajectories, with population geneticists and optimality theorists discussing the possibility of a convergence of the two approaches -the so-called 'streetcar' model 15 .…”

“…The overwhelming range of hypotheses proposed to account for changes of species richness (Palmer 6 lists 120 named hypotheses for variation in species richness or coexistence, and Rohde 7 identifies 28 specifically applied to the latitudinal gradient) makes the task of sorting out which factors are causal and which are incidental a daunting one. Increasingly, using computationally intensive methods, ecologists and biogeographers are looking for answers at a regional or a global scale, putting models and hypotheses [7][8][9][10][11][12][13][14][15] to the test against increasingly comprehensive distributional data encompassing the still poorly known tropics [15][16][17][18][19] .…”

“…In spite of the plethora of climatic, ecological, evolutionary and historical explanations proposed to explain biogeographic diversity patterns, something fundamental has, until recently, been almost completely ignored: the geometry of species ranges in relation to geographical boundaries. Based both on simulations 11,12,14 and on analytical null models 13,15 , it is now clear that a mid-domain peak or plateau in species richness is inevitable for virtually any set of ranges, theoretical or empirical, when these ranges are randomly placed within a bounded geographical domain, in the complete absence of any supposition of environmental gradients within the domain. Qualitatively, this result survives a wide range of changes in model details and assumptions.…”

“…Based on regional biotas, geometric models 11,[13][14][15] demonstrate that the stochastic placement of species ranges between shared geographic boundaries can generate precise predictions of species richness at points between the boundaries. For example, in the case of random, one-dimensional placement of ranges between two boundaries, the null models predict a convex, symmetrical pattern of species richness: this pattern is either parabolic 11,13 or quasi-parabolic 11,15 depending upon alternative distributions of range sizes and of midpoints ( Fig.…”