Conservation and Genetics

Abstract

Humans are responsible for a cataclysm of species extinction that will change the world as we see it, and will adversely affect human health and wellbeing. We need to understand at individual and societal levels why species conservation is important. Accepting the premise that species have value, we need to next consider the mechanisms underlying species extinction and what we can do to reverse the process. One of the last stages of species extinction is the reduction of a species to a few populations of relatively few individuals, a scenario that leads invariably to inbreeding and its adverse consequences, inbreeding depression. Inbreeding depression can be so severe that populations become at risk of extinction not only because of the expression of harmful recessive alleles (alleles having no phenotypic effect when in the heterozygous condition, e.g., Aa, where a is the recessive allele), but also because of their inability to respond genetically with sufficient speed to adapt to changing environmental conditions. However, new conservation approaches based on foundational quantitative and population genetic theory advocate for active genetic management of fragmented populations by facilitating gene movements between populations, i.e., admixture, or genetic rescue. Why species conservation is critical, the genetic consequences of small population size that often lead to extinction, and possible solutions to the problem of small population size are discussed and presented.

Keywords: Biodiversity; Conservation; Ecosystem Services; Genetic Rescue; Inbreeding; Inbreeding Depression.

Figure 1

King Charles II. This remarkably unflattering portrait of King Charles II (despite the artist’s attempts to do otherwise) demonstrates the harmful consequences of close inbreeding in humans and the vast majority of non-haploid organisms. Because of prior generations of mating with close relatives, Charles II manifested the inbreeding slightly higher than expected in the offspring of a brother-sister mating (see text) [56]. KHM-Museumsverband.

Figure 2

The Florida Panther was reduced to a few individuals and demonstrated typical signs of inbreeding, including a high frequency of sterile sperm, and, in the case of cats, a high frequency of kinked tails, shown in the figure. The Florida Panthers also had low genetic variation, typical of an inbred population. Female panthers from Texas were introduced to the inbred Florida population, and the phenotypic manifestations of inbreeding disappeared simultaneous with the increased vigor of the population (see text) [60]. Reprinted from Current Biology, 3, M. E. Roelke, J. Martenson and S. J. O’Brien, The consequences of demographic reduction and genetic depletion in the endangered Florida panther, 340-350, 1993, with permission from Elsevier.

Figure 3

In Illinois, the last remnant population of Lakeside daisy was reduced to four individuals that unfortunately (by chance) all shared the same incompatibility genotype and consequently were unable to mate (make seed) with one another. The investigator [64] recognized that the species is self-incompatible and was able to produce copious seed by mating the Illinois individuals to individuals from Ohio of different incompatibility genotypes. Seed was germinated and in the early 1990s, seedlings were transferred to two sites in Illinois having the physical and biotic features of typical Lakeside daisy habitat. The two populations are still thriving. Photo courtesy of Juanita Armstrong-Ullberg and the Forest Preserve District of Will County, Illinois.