Adaptation, speciation and extinction in the Anthropocene

Abstract

Humans have dramatically altered the planet over the course of a century, from the acidity of our oceans to the fragmentation of our landscapes and the temperature of our climate. Species find themselves in novel environments, within communities assembled from never before encountered mixtures of invasives and natives. The speed with which the biotic and abiotic environment of species has changed has already altered the evolutionary trajectory of species, a trend that promises to escalate. In this article, I reflect upon this altered course of evolution. Human activities have reshaped selection pressures, favouring individuals that better survive in our built landscapes, that avoid our hunting and fishing, and that best tolerate the species that we have introduced. Human-altered selection pressures have also modified how organisms live and move through the landscape, and even the nature of reproduction and genome structure. Humans are also shaping selection pressures at the species level, and I discuss how species traits are affecting both extinction and speciation rates in the Anthropocene.

Keywords: Anthropocene; anthropogenic; evolution; extinction; selection.

Figure 1.

Human-altered selective forces. (a) Selection in built environments: feathers left on a window illustrate the high death toll of birds colliding with buildings and automobiles [12], selecting against migratory behaviour [13] and for manoeuvrability [14]. (b) Selection to avoid hunting or harvesting: humans target individuals with preferred traits, selecting against traits such as long ivory tusks [15]. (c) Selection in novel communities: both abiotic and biotic selection pressures are reshaped when humans bring together species in new assemblages, as found in cardinals nesting in introduced honeysuckles [16]. (d) Selection on dispersal: fragmented landscapes select for individuals that can remain in hospitable environments, favouring non-dispersing seeds in Crepis sancta [17]. (e) Selection on inheritance systems: rapid evolution associated with human cultivation can alter the genome, with increased recombination rates and polyploidy found in many domesticated plants, such as oats [18]. Photographs: (a) Alan Hensel; (b) Sarah Otto; (c) Jeff Whitlock; (d) Susan Lambrecht; (e) Henrik Sendelbach.