Human-modified ecosystems and future evolution

Our global impact is finally receiving the scientific attention it deserves. The outcome will largely determine the future course of evolution. Human-modified ecosystems are shaped by our activities and their side effects. They share a common set of traits including simplified food webs, landscape homogenization, and high nutrient and energy inputs. Ecosystem simplification is the ecological hallmark of humanity and the reason for our evolutionary success. However, the side effects of our profligacy and poor resource practices are now so pervasive as to threaten our future no less than that of biological diversity itself. This article looks at human impact on ecosystems and the consequences for evolution. It concludes that future evolution will be shaped by our awareness of the global threats, our willingness to take action, and our ability to do so. Our ability is presently hampered by several factors, including the poor state of ecosystem and planetary knowledge, ignorance of human impact, lack of guidelines for sustainability, and a paucity of good policies, practices, and incentives for adopting those guidelines in daily life. Conservation philosophy, science, and practice must be framed against the reality of human-dominated ecosystems, rather than the separation of humanity and nature underlying the modern conservation movement. The steps scientists can take to imbed science in conservation and conservation in the societal process affecting the future of ecosystems and human well-being are discussed.

Female mating preference for bold males in the guppy, Poecilia reticulata.

Although females prefer to mate with brightly colored males in numerous species, the benefits accruing to such females are virtually unknown. According to one hypothesis of sexual selection theory, if the expression of costly preferred traits in males (such as conspicuous colors) is proportional to the male's overall quality or reveals his quality, a well-developed trait should indicate good condition and/or viability for example. A female choosing such a male would therefore stand to gain direct or indirect fitness benefits, or both. Among potential phenotypic indicators of an individual's quality are the amount and brightness of its carotenoid-based colors and its boldness, as measured by its willingness to risk approaching predators without being killed. Here, we show experimentally that in the Trinidadian guppy (Poecilia reticulata) the visual conspicuousness of the color pattern of males correlates positively with boldness toward, and with escape distance from, a cichlid fish predator. Bold individuals are thus more informed about nearby predators and more likely to survive encounters with them. Mate-choice experiments showed that females prefer colorful males as mates, but prefer bolder males irrespective of their coloration when given the opportunity to observe their behavior toward a potential fish predator. By preferentially mating with colorful males, female guppies are thus choosing on average, relatively bold, and perhaps more viable, individuals. In doing so, and to the extent that viability is heritable, they potentially gain indirect fitness benefits by producing more viable offspring than otherwise.