Hidden Pathways to Extinction

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· 제목 : Hidden Pathways to Extinction (Hardcover)
· 분류 : 외국도서 > 과학/수학/생태 > 과학 > 생명과학 > 생태학
· ISBN : 9783030867638
· 쪽수 : 237쪽
· 출판일 : 2022-05-18

Investigating how the diversity is organized is fundamental to understand how complexity can emerge and persist. The field of ecological networks has grown in the last decade, achieving a central position for ecology. This chapter will introduce the basic concepts needed to understand the network modelling approach to extinction cascades. The distinctive traits between different kinds of ecological networks (mutualistic/antagonistic; bipartite/unimode; directed/undirected) will be discussed as well.

3 - The drivers of biodiversity crisis

The collapse of ecological networks is promoted by two, distinct processes, namely: primary extinctions, i.e. the direct loss of nodes (i.e. species) due, for example, to over-exploitation; and secondary extinctions, i.e. the loss of species following the disappearance of their resources. Although the chapter will cover mainly the first aspect, it will also serve to introduce the coextinction concept, and to set out the scene for the many unsolved questions that will be covered in the rest of the book.

4 - The paradox of specialization

Intuitively, specialization should be strongly related to extinction risk. This, however, is in clear contrast with the commonness of specialization (for example, most parasites can infect only one, or a few hosts). This paradox can be explained, in an evolutionary perspective, by the fact that consumers tend to specialize on dependable resources, hence minimizing their risk of losing them. There are many aspects of this mechanism to be considered. In particular, the dependability of resources in the Anthropocene is not the same that when ecological networks have emerged. This has several implications, that will be discussed in order to introduce the idea of a 'neutral' approach to species vulnerability to extinctions (which will be treated extensively in a separate chapter).

5 - Co-Extinction debt

Many species are still extant, but nevertheless inevitably doomed to extinction, due to different causes. This constitutes the so-called extinction debt, which is a concept of primary importance for conservation biology. In this chapter, I will introduce and discuss the application of this concept to dependent species. In particular, I will emphasize how the extinction debt for parasites or mutualistic species is likely to be much wider than for free-living species.

6 - Escaping co-extinctions

In a very simplified view, a consumer goes extinct when all of the resources it depends on are lost. On the one hand, the consumer will experience troubles much before the complete extinction of its resources. Nevertheless, there exist also the possibility that the consumer finds a way to survive. The chapter will focus on ecological mechanisms such as host switch and adaptive foraging that can provide ways to escape co-extinctions.

7 - The past

Due to the current global scenario, where the environmental conditions are extremely different from the ones where networks evolved, we have a few chances to get a grasp on the 'naturalness' of ecological networks. One intriguing alternative is looking into the fossil record. Thanks to new technologies capable of recovering and processing ancient DNA from fossils, we are gaining more and more insights about past mass extinctions. This chapter will investigate if and how learning from the past can help us improve our future.

8 - Mutualistic vs antagonistic networks

The chapter will delineate the differences and the analogies between mutualistic and antagonistic networks. The chapter will aim more at finding unifying characters than distinctive ones, with the final aim to put mutualism and antagonism on a continuous gradient.

9 - Species vulnerability in the Anthropocene

The chapter will deal explicitly with the current way we identify vulnerability, and will aim at clarifying how the current perception of extinction risk, although meaningful at the species level, is disentangled from the assembly evolutionary rules that have generated ecological networks. This poses many caveats in how extinction risk categories (such as those provided by IUCN red list) should be used to predict diversity loss trajectories.

10 - Future Winners

Although it is undebatable that global change will lead to a dramatic reduction in biodiversity, we are already witnessing species expanding their range, finding new resources and outcompeting other species. This has clearly implications, because it creates new links in ecological networks, altering their structure, and possibly their response to species loss. The chapter will try to identify who are these global change ‘winners’, and to define their role in co-extinction processes.

11 - Life cycles, intermediate hosts, parateny

The chapter will deal with the determinants of co-extinction risks besides specificity. Life cycle complexity, the ability to survive in paratenic hosts, and the different degree of specialization in the various stages of development are all aspect that clearly affect a species’ co-extinction risk. Taking all of them into account in modelling studies, however, is often challenging. The chapter will tackle the issue, trying to provide hints on how this information should be taken into account to trace co-extinction trajectories.

12 - The future of infectious diseases

There is a paradox in the current perception of global change, in that despite diversity will sensibly decrease, we should expect an increase in infectious diseases. However, the co-extinction paradigm depicts a very different scenario, where the diversity of pests will instead decrease with biodiversity loss. Nevertheless, global mobility could promote host switch events, with dramatic consequences possibly leading to a further increment in extinction rates.

13 - Alien species, enemy release

The risk for emerging diseases is strongly related to co-extinction processes. Many parasite species could be subjected by strong selective pressures due to reduction in their hosts’ abundance. An alternative outcome to co-extinction, as anticipated in the previous chapter, is host switching. Global movements of organisms is making this kind of process more and more common, often leading to dramatic consequences. However, species invasions may have several different (and mostly unpredictable) effects, that can either increase or decrease co-extinction risks. The chapter will try to provide a clear framework, ideally covering all possible scenarios.

14 - A ‘neutral’ theory of extinctions

The previous chapters will serve to build up the thesis that focusing on extinction risk at the species level does not provide a fair representation of how biodiversity loss work at higher levels of organization. This chapter will address this issue explicitly, showing how human activity and global change have altered ecosystems so much, that current species vulnerability estimates have little use to predict overall biodiversity loss trajectories.

15 - Slowing down co-extinctions

The chapter will focus on how conservation biology can tackle the problem, and try to slow down processes. An interesting example deserving a thorough discussion about pros and cons, is that of reintroducing parasites as a mean to protect ecosystems.