Causes of maladaptation.

Steven P Brady,Thomas Lamy,Gregor Rolshausen,Christopher G Eckert,Andrew G Mcadam,Gregor F Fussmann,Rowan D.H Barrett,Andrew Gonzalez,Andrew M Simons,Daniel I Bolnick,Alison M Derry,Erika Crispo,Amy L Angert,Antoine Paccard,Frederic Guichard,Andrew P Hendry,Dylan J Fraser,Amy E.M Newman

doi:10.1111/eva.12844

Abstract

Evolutionary biologists tend to approach the study of the natural world within a framework of adaptation, inspired perhaps by the power of natural selection to produce fitness advantages that drive population persistence and biological diversity. In contrast, evolution has rarely been studied through the lens of adaptation's complement, maladaptation. This contrast is surprising because maladaptation is a prevalent feature of evolution: population trait values are rarely distributed optimally; local populations often have lower fitness than imported ones; populations decline; and local and global extinctions are common. Yet we lack a general framework for understanding maladaptation; for instance in terms of distribution, severity, and dynamics. Similar uncertainties apply to the causes of maladaptation. We suggest that incorporating maladaptation‐based perspectives into evolutionary biology would facilitate better understanding of the natural world. Approaches within a maladaptation framework might be especially profitable in applied evolution contexts – where reductions in fitness are common. Toward advancing a more balanced study of evolution, here we present a conceptual framework describing causes of maladaptation. As the introductory article for a Special Feature on maladaptation, we also summarize the studies in this Issue, highlighting the causes of maladaptation in each study. We hope that our framework and the papers in this Special Issue will help catalyze the study of maladaptation in applied evolution, supporting greater understanding of evolutionary dynamics in our rapidly changing world.

Highlights

| 1230 framework might be especially profitable in applied evolution contexts – where re‐ ductions in fitness are common
What would we learn if instead we looked for maladaptation (Brady, 2013, 2017; Crespi, 2000; Gould & Lewontin, 1979; Hendry & Gonzalez, 2008; Hereford & Winn, 2008; Rogalski, 2017)? For instance, quantitative syntheses and meta‐analyses of reciprocal transplant experiments have found that the classic signature of local adaptation is present in about 70% of the contrasts, meaning that it was absent 30% of the time (Hereford, 2009; Leimu & Fischer, 2008)
There, the butterflies remained adapted to their traditional host and maladapted to the novel host in six sepa‐ rate host‐adaptive traits, including alighting bias, geotaxis, clutch size, and offspring performance. Despite these maladaptations caused by a moving target, insect fitness increased on the poorly defended, novel host compared to the traditional host that was still used in adjacent unlogged patches

Summary

Introduction

| 1230 framework might be especially profitable in applied evolution contexts – where re‐ ductions in fitness are common. Shifts in mean trait value can be caused by maladaptive plasticity generated by en‐ vironmental stressors or other novel environmental changes. The optimal phenotype can change with environmental conditions (black arrow “C” pointing to the right in Figure 3), which can increase the distance of the optimum phenotype from current phenotypes, which should decrease mean fitness.

Results

Conclusion