Women and Wolves
Women and Wolves
Importance of genetics when dealing with species conservation - why do genetics matter? Why should we care about genetics when trying to conserve an endangered species?
Rachael Willis
Species conservation requires knowledge of various disciplines, such as applied ecology, evolutionary biology, and environmental policy. When working to conserve an endangered species, it is easy to overlook the importance of genetics. Conservation genetics is an emerging field combining disciplines such as molecular biology, population genetics, evolutionary taxonomy, and mathematical modeling. Upon developing an understanding of the genetic relationships among the organisms of concern, managers are well-equipped to employ strategies to preserve biodiversity (Genetic Science Learning Center, n.d.).Understanding genetics is crucial to conserving endangered and threatened animals, such as the Mexican grey wolf. Generally, higher levels of genetic diversity are considered to be beneficial for a species’ survival. Fisher’s fundamental theorem states that the more additive genetic variation a population possesses, the better it can evolve in response to natural selection (Woodruff, 2004). In other words, if a population has more heritable traits in its gene pool, it is more likely to adapt to challenges such as environmental change, disease, or predation. This heightened adaptability offers safeguards against various disturbances. With higher genetic diversity, the likelihood of the entire population dying as a result of a disturbance is relatively low.On the contrary, low genetic diversity is detrimental to a population’s well-being. Low Small population size is often associated with lower heterozygosity (Willi et al., 2021). Heterozygosity is a common indicator of genetic diversity referring to the conditions of an individual having two different alleles for one particular gene. Lower heterozygosity across several different loci, or locations on a chromosome, indicates lower genetic diversity. Additionally, in small populations, there is a higher likelihood of inbreeding due to the small number of individuals (Willi et al., 2021). This leads to inbreeding depression, in which the fitness of the population is reduced due to inbreeding (Willi et al., 2021).It is well-documented that Mexican grey wolves have low genetic diversity and high inbreeding rates, most likely due to their recent population decline (Taron et al., 2021). With low levels of genetic diversity, Mexican grey wolves possess a lower ability to adapt to or survive environmental disturbances. However, further understanding of the Mexican grey wolf genome can provide conservation managers with key information to effectively conserve the subspecies
Inbreeding
Rachael Willis
Inbreeding occurs when two closely related organisms mate. This is common in small populations, such as those seen with Mexican grey wolves. Inbreeding often results in a phenomenon known as inbreeding depression, in which inbreeding reduces a population’s ability to survive and reproduce, thus negatively affecting its overall fitness (UC Museum of Paleontology, n.d.) This is especially problematic when it involves an endangered species, as harming each population’s fitness may lead to local extinction.
Unfortunately, inbreeding is a persistent problem impacting Mexican grey wolf conservation. Inbreeding in Mexican grey wolves is associated with lower genetic diversity (Fredrickson et al., 2007). Moreover, inbreeding may have the potential to lower individual Mexican grey wolves’ fitness (Fredrickson et al., 2007), thus impacting their ability to breed and produce viable offspring. Inbreeding is also correlated with lower fertility rates and pup survival rates (Survey Finds 257 Mexican Gray Wolves Living in U.S. Southwest, 2024), further demonstrating that inbreeding may negatively impact these wolves’ fitness.
Thankfully, there are methods to reduce the effects of inbreeding on Mexican grey wolf populations. Strategic captive breeding can produce new wolves with higher genetic variation (Harding et al., 2016). If reintroduced into the wild, these captive-bred wolves can increase the genetic diversity within a given population, thus mitigating some of the impacts of inbreeding.
How Dispersal & the I-40 Rule Affect Genetic Diversity in Arizona’s Mexican Grey Wolves
Photo by: George Andrejko
Developing metapopulation connectivity Mexican grey wolf recovery in the American Southwest is a challenging effort, primarily due to issues with genetic diversity, dispersal limitations, and restrictive regulations. Dispersal, the movement of wolves from one area to another, is key to ensuring healthy populations. For Mexican grey wolves, dispersal leads to encounters between genetically distinct individuals, facilitating gene flow and potential increases in Mexican grey wolf genetic diversity.
Recent estimates suggest that Mexican grey wolves are experiencing decreasing dispersal rates, which may accelerate their extinction risk if less than 0.5 wolves capable of contributing genetic material to the next generation disperse into new areas per generation (Carroll et al., 2013). When populations are under 150 to 200 wolves, limited dispersal increases their vulnerability to different environmental and genetic factors that may lead to extinction (Carroll et al., 2013).
Arizona’s I-40 boundary, as set by the U.S. Fish and Wildlife Service in the Mexican Wolf Experimental Population Area (MWEPA), restricts the territory where Mexican grey wolves can naturally roam. U.S. Fish and Wildlife Service regulations state that Mexican grey wolves must remain south of I-40, effectively creating a dividing line confining wolves to the central and southern regions of Arizona and New Mexico (Endangered and Threatened Wildlife and Plants (2022). Although this rule is intended to balance wolf conservation with human development north of I-40, it strictly limits the Mexican grey wolves; natural dispersal capabilities, subsequently affecting genetic diversity.
The restricted dispersal space established by the I-40 rule reduces potential encounters between genetically distinct Mexican grey wolves. These encounters could result in mating that would support genetic diversity (Defenders of Wildlife, 2024). As Mexican grey wolves face a limited dispersal area and quantity of mates, their genetic diversity continues to decrease. This may lead to increased inbreeding and reduced resilience to future environmental disturbances.
Various conservationists argue that allowing dispersal north of I-40 could expand the wolves’ range into areas with suitable habitats (Defenders of Wildlife, 2024). This, in turn, would promote population growth and genetic diversity, both of which are crucial for Mexican grey wolf conservation efforts. Moreover, increasing dispersal abilities would enhance gene flow, another critical factor for these isolated wolf populations.
Overall, the I-40 rule has created barriers that may negatively impact the genetic diversity and conservation of Mexican grey wolves. By prioritizing policies allowing for greater dispersal and easing current dispersal limitations, the state of Arizona can build the foundations for more resilient and genetically diverse Mexican grey wolf populations.
References
Fredrickson, R. J., Siminski, P., Woolf, M., & Hedrick, P. W. (2007). Genetic rescue and inbreeding depression in Mexican wolves. Proceedings of the Royal Society B: Biological Sciences, 274(1623), 2365–2371. https://doi.org/10.1098/rspb.2007.0785
Harding, L. E., Heffelfinger, J., Paetkau, D., Rubin, E., Dolphin, J., & Aoude, A. (2016). Genetic management and setting recovery goals for Mexican wolves (Canis lupus baileyi) in the wild. Biological Conservation, 203, 151–159. https://doi.org/10.1016/j.biocon.2016.09.018
Survey Finds 257 Mexican Gray Wolves Living in U.S. Southwest. (2024, March 5). Center for Biological Diversity. Retrieved October 27, 2024, from https://biologicaldiversity.org/w/news/press-releases/survey-finds-257-mexican-gray-wolves-living-in-us-southwest-2024-03-05/.
UC Museum of Paleontology. (n.d.). Inbreeding Depression. Understanding Evolution. https://evolution.berkeley.edu/the-relevance-of-evolution/conservation/inbreeding-depression/
Genetic Science Learning Center. (n.d.). Conservation Genetics. Learn Genetics. https://learn.genetics.utah.edu/content/science/conservation/
Taron, U. H., Salado, I., Escobar‐Rodríguez, M., Westbury, M. V., Butschkau, S., Paijmans, J. L., vonHoldt, B. M., Hofreiter, M., & Leonard, J. A. (2021). A sliver of the past: The decimation of the genetic diversity of the Mexican wolf. Molecular Ecology, 30(23), 6340–6354. https://doi.org/10.1111/mec.16037
Willi, Y., Kristensen, T. N., Sgrò, C. M., Weeks, A. R., Ørsted, M., & Hoffmann, A. A. (2021). Conservation genetics as a management tool: The five best-supported paradigms to assist the management of Threatened Species. Proceedings of the National Academy of Sciences, 119(1). https://doi.org/10.1073/pnas.2105076119
Woodruff, D. S. (2004). Populations, species, and conservation genetics. (S. A. Levin, Ed.).Encyclopedia of Biodiversity, 811–829. https://doi.org/10.1016/b0-12-226865-2/00355-2
Carroll, C., Fredrickson, R. J., & Lacy, R. C. (2013). Developing metapopulation connectivity criteria from genetic and habitat data to recover the endangered Mexican wolf. Conservation Biology, 28(1), 76–86. https://doi.org/10.1111/cobi.12156
Defenders of Wildlife. (2024, March 5). Mexican gray wolf numbers go up, but numbers aren’t the whole story and populations still dangerously low, says green groups. https://defenders.org/newsroom/mexican-gray-wolf-numbers-go-numbers-arent-whole-story-and-populations-still-dangerously
Endangered and Threatened Wildlife and Plants; Revision to the Nonessential Experimental Population of the Mexican Wolf, 50 C.F.R. § 17 (2022).