![]() The classical «escape and radiate hypothesis» proposed by Ehrlich and Raven in 1964, based on butterflies and plants, provides a potential mechanism for the co-diversification of enemies and their victims. And the pressure to find an «enemy-free space» (ways of living that reduce or eliminate a species vulnerability to natural enemies) may spur further complementary radiation of the victims, followed by counter-evolution in the enemies. Enemies also impact the evolutionary trajectories of their victims, because victims evolve to escape. Thus, the adaptive radiation of a taxon of victims galvanizes the diversifying response of their enemies, producing an evolutionary cascading effect through the food web ( Brodersen, Post, & Seehausen, 2017).īut this is not necessarily a unilateral process. Avel Chuklanov/Unsplashīasically, a group of organisms takes profit from the ecological opportunity of being exposed to a novel source of victims that remain still untouched by other potential enemies, so that they are the first ones to get the job offer of being enemies of the novel victims. In the picture, a lioness observes a group of zebras. In this sense, natural enemies represent a substantial part of biodiversity. Many organisms all over the world provide food for others. These include the diversification of phytophagous insects after the arising of flowering plants and the adaptive radiation of horses in North America during the Miocene after the appearance of grasslands – with the latter resulting in a diverse family (Equidae) displaying a wide range of body sizes and tooth morphological adaptations for grazing. The idea helps explain the evolutionary explosions of natural enemies along the arc of Earth history. The old but powerful concept of «ecological opportunity» – crucially including novel resources – has been invoked by ecologists and evolutionary biologists to explain why and when adaptive radiation occurs. That ancestral species diversifies into multiple different species in part due to how it experiences environmental heterogeneity (ecological opportunity Stroud & Losos, 2016). One of the most fascinating and productive evolutionary mechanisms of biodiversity genesis is the adaptive radiation that produces punctual explosions of a variety of life forms from a single ancestor over macroevolutionary timescales. ![]() THE ESCAPE AND PERSECUTION GAME AS A BIODIVERSITY ENGINE But natural enemies are more than an appreciable portion of the biodiversity pie for they also contribute to its elaboration, preservation, stability, and, often, even reciprocally feed on the pie. As an extreme case, the little tinamou ( Crypturellus soui), which belongs to one of the most ancient bird lineages on Earth, hosts more than twenty species of lice, with up to nine species recorded from a single individual. ![]() Almost every animal or plant species hosts its own parasite community. Parasites account for at least one third of all animal and plant species based on the most conservative estimates, and some less conservative counts consider them to comprise up to half or more of all living things. What would happen if a person with enough magic power decided to remove all of the natural enemies from this world in an attempt to make it more peaceful? Probably this peaceful kingdom would prove ultimately boring to her eyes, but her feelings would not matter because her act of sorcery would also remove herself! Humans are one of the dominant top predators on the planet. Natural enemies represent a substantial portion of biodiversity. The term includes predators, herbivores, parasites, parasitoids, pathogens, and even some plants. All of these consumers are «natural enemies», species that inflict harm on others (their victims) by taking resources (energy and nutrients) from them by force or stealth for their own benefits (as measured in reproduction and survival). The American chestnut might grow to over 35 meters, but the species has been driven to near extinction by a tiny infective fungus. Parasites dramatically break the constraint on relative size, feeding on often much larger hosts. You can picture a horse peacefully feeding on the grass, flies trapped in spider webs, your domestic cat bringing his last bird trophy to your room, flickering television images of the elegant and fast movements of the cheetah pursuing a Thomson’s gazelle, or the impressive air jump of a great white shark catching a seal from the sea surface.īut even the magnificent shark is fed on by other organisms, because not only the big one eats the little one. Many living organisms on the Earth provide food for others.
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