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In short, conserving human cultural diversity along with biological diversity and interactions between the two is fertile ground for collaboration among conservation biologists, anthropologists, and others. Perhaps the explosion of techniques, approaches, and applications of genetics to conservation (Box 5.1) will expand into the future to address issues conserving cultural diversity as well.

BOX 5.1 The role of genetics in conservation biology

      Genetics plays a special role in conservation biology. We touch on many uses of genetics throughout this book, but do not dwell much on the genetic approaches behind them. Here we “call out” the significant ways that modern genetics contributes to biodiversity conservation – some obvious and some surprising.

      Population Estimation

      Effective population size (N_e) is a critical piece of information for management of many rare species. In theory it is easy to count the number of individuals in the field, pass the numbers through some formulae, and estimate N_e. In reality, many creatures are very difficult to count in the wild (too rare, too shy, too cryptic, etc.). Genetic methods offer an alternative. One can estimate N_e by looking at the change in heterozygosity over time, something that can be done with historical and contemporary genetic samples. Genotypes can also be used as “tags,” like the bird rings and other crude methods biologists use to mark animals and estimate their population sizes through mark–recapture methods. This is particularly helpful for estimating populations of animals that are challenging to catch and mark, like grizzly bears (Kendall et al. 2016) or great white sharks (Andreotti et al. 2016), but whose DNA you can sample without catching them, for example from their hair left on trees, or feces on the ground or in the water. Signatures of population history can also be found in genetic data that provide insights into whether a population has declined, expanded, or remained stable over recent generations (Garrick et al. 2014).

      Landscape Genetics

      As hard as species are to count, it is even harder to know how they move around the landscape. Yet migration and dispersal are critical to understand, for example to maintain migration routes among protected areas. The history of movement of a species is captured in the pattern of how alleles are spread via gene flow by individuals moving around the landscape (Manel and Holderegger 2013), indicating what conduits of habitat should be protected (e.g. in the case of frogs on Mount Kilimanjaro: Zancolli et al. 2014). This is the essence of landscape genetics.

      Defining Units of Conservation

      Species are the typical focus of conservation, but just conserving species will not adequately protect intraspecific diversity, which is the basis of evolutionary potential. How are species and their constituent populations organized across their range? How should they best be protected? Fisheries biologists frequently try to distinguish stocks of fish for improved management – that is, uncovering “units of conservation” – a good example of which is the work of Zhivotovsky et al. (2015) on how a massive salmonid fish known as the taimen is organized around the Russian Far East.

      Hybridization

      Genetics is critical for measurement of hybridization between species. In many countries, hybrids are not protected by law. The ongoing controversy over listing the red wolf as an endangered “species” versus dropping protection because it is merely a hybrid of gray wolves and coyotes is one that pivots on new and ever more definitive genetic analyses published every few years (see Cahill et al. 2016). Hybridization is also a real threat to many rare species, and genetic methods enable us to detect the extent of the problem. Very occasionally hybrids can be used to restore depleted species (Edwards et al. 2013).

      “Genes that Matter”

      Most genetic analyses are based on “markers” with no known connection to the actual fitness. Which specific genes and alleles are actually tied to a particular challenge the species is facing? These genetic signatures of adaptation are critical for choosing the best individuals for rescuing a species, particularly in a changing world where certain alleles might be more advantageous. A good example is the use of scans of the entire genome of the endangered Przewalski’s horse of Mongolia to identify informative genetic markers to monitor and select for during captive breeding (Der Sarkissian et al. 2015).

      Phylogenetic Prioritization

      Knowing how one species is related to another is useful for at least three reasons. The first is identification of distinct lineages in need of protection (e.g. cryptic cave fish: Niemiller et al. 2013). The second is understanding a species’ relative phylogenetic distinctiveness (e.g. for prioritizing lineages of freshwater mussels for protection: Jones et al. 2015). The third is mapping areas of their world where evolutionary distinctiveness is concentrated (Jetz et al. 2014).

      Trade

      Molecular genetics has been helpful for identifying the sources and identity of traded species, for example in the case of elephant ivory (Wasser et al. 2015), caviar from endangered sturgeon (Fain et al. 2013), and mahogany in the timber trade (Degen et al. 2013).

      Diagnosing Disease

      Disease is a primary threat to many species but it is often difficult to diagnose based solely on external symptoms. Screening for the DNA of possible disease agents has revolutionized diagnosis and treatment, for example for many amphibians (e.g. Collins 2013) and Tasmanian devils (Morris et al. 2015).

      Environmental DNA

      Environmental DNA, or eDNA, is DNA collected from environmental samples such as soil, water, or even air rather than directly sampled from an individual organism. Such eDNA usually originates from shed skin cells that accumulate in an organism’s environment via feces, mucus, gametes, shed skin, carcasses, and hair. Sometimes, eDNA can be extracted from the meals found in guts of blood‐sucking or predator arthropods. Samples of the environment where organisms of interest might live can be analyzed with DNA sequencing methods, known as metagenomics, for rapid measurement and monitoring of species richness and community composition. eDNA is particularly useful for detecting rare species without having to capture them. The approach may eventually be able to tell us about population size and dynamics and species geographic distribution, but the methods are still under development. A helpful overview on the uses and limitations of eDNA is provided by Cristescu and Hebert (2018).

      Genetic Engineering

      We now are approaching a new era in which we can provide endangered species with new traits that enable them to deal with the threats they are facing. For example, scientists have transferred two genes from wheat into the American chestnut, conferring upon the chestnut resistance to a fungal blight that nearly eradicated it across the vast range in which it was a dominant species (Powell 2014). Genetic engineering may also generate novel genes that can be introduced into populations of invasive exotic species so that they limit their own numbers, a distinct possibility now for dealing with the scourge of endemic island species everywhere: black rats (Campbell et al. 2015). Genetic engineering falls within the realm of “synthetic biology” and offers extraordinary opportunities to address some seemingly intractable conservation issues (Piaggio et al. 2017) while also posing new ethical quandaries. Some straightforward applications include transplanting genes for resistance to white‐nose syndrome into bats and to chytrid fungus into amphibians, or giving corals that are vulnerable to bleaching carefully selected genes from nearby corals that are more tolerant of heat and acidity. More controversial would be eliminating populations of feral cats and

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