Big Questions in Ecology and Evolution
Thomas N. Sherratt, David M. Wilkinson
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Why do we age? Why cooperate? Why do so many species engage in sex? Why do the tropics have so many species? When did humans start to affect world climate?
This book provides an introduction to a range of fundamental questions that have taxed evolutionary biologists and ecologists for decades. Some of the phenomena discussed are, on first reflection, simply puzzling to understand from an evolutionary perspective, whilst others have direct implications for the future of the planet. All of the questions posed have at least a partial solution, all have seen exciting breakthroughs in recent years, yet many of the explanations continue to be hotly debated.
Big Questions in Ecology and Evolution is a curiosity-driven book, written in an accessible way so as to appeal to a broad audience. It is very deliberately not a formal text book, but something designed to transmit the excitement and breadth of the field by discussing a number of major questions in ecology and evolution and how they have been answered. This is a book aimed at informing and inspiring anybody with an interest in ecology and evolution. It reveals to the reader the immense scope of the field, its fundamental importance, and the exciting breakthroughs that have been made in recent years.
illustrating the possibility that some of the asymmetries in species richness gradient could be the product of random processes—although in most cases, there are probably ecological explanations (such as hemispherical asymmetries in climate). 110 Big Questions in Ecology and Evolution number of large ranges must necessarily overlap more than the same number of small ranges in a ﬁxed area, making this a poor test of the mid-domain effect.46 What are we to make of the mid-domain explanation for
the tropics being ‘cradles’ of species richness. In addition, they were also probably more likely to survive there (tropics as ‘museums’ of species, in Stebbins’61 terminology) and so species also spread out from the tropics into non-tropical areas. Ecological explanations: diversity begets diversity? There are several ways in which the tropics could act as the ‘cradle’ of global species richness. First, rates of evolution in the tropics could be higher, perhaps because the organisms there have
argument, because similar to the tropical conservatism hypothesis discussed earlier, it stresses how initial differences can become magniﬁed over time. At its most basic, one might argue that the occurrence of many species of plants potentially allows more herbivores, which could then allow more carnivores. However, this ‘common sense’ explanation does not always match the data; for example, primate species richness in South America shows a positive correlation with plant productivity but not
7.3 One of the North Wales exclosures—this one is in Cwm Idwal (‘site 2’ in the paper by Hill et al.6). (a) Taken in 2002—note the much shorter grass outside the exclosure where there has been sheep grazing and the dark-coloured bushes of heather which are only able to grow inside the exclosure where they are protected from sheep. As part of the management of Cwm Idwal nature reserve attempts were made to exclude all sheep from late 1998. In 2001, Britain suffered a major outbreak of the animal
describing which plant species should be searched to ﬁnd caterpillars of any given species, as collectors often wanted to catch the larvae so they could be reared to provide undamaged adults for their collections.20 One potential explanation for this is that caterpillars have to specialize in only a few food plants because these are the only ones to which they have evolved mechanisms for dealing with potentially poisonous chemicals in the plant tissue (e.g. the cinnabar moth). The idea that plant