Genetic signatures of a demographic collapse in a large‐bodied forest dwelling primate (Mandrillus leucophaeus)

Abstract

It is difficult to predict how current climate change will affect wildlife species adapted to a tropical rainforest environment. Understanding how population dynamics fluctuated in such species throughout periods of past climatic change can provide insight into this issue. The drill (Mandrillus leucophaeus) is a large-bodied rainforest adapted mammal found in West Central Africa. In the middle of this endangered monkey's geographic range is Lake Barombi Mbo, which has a well-documented palynological record of environmental change that dates to the Late Pleistocene. We used a Bayesian coalescent-based framework to analyze 2,076 base pairs of mitochondrial DNA across wild drill populations to infer past changes in female effective population size since the Late Pleistocene. Our results suggest that the drill underwent a nearly 15-fold demographic collapse in female effective population size that was most prominent during the Mid Holocene (approximately 3-5 Ka). This time period coincides with a period of increased dryness and seasonality across Africa and a dramatic reduction in forest coverage at Lake Barombi Mbo. We believe that these changes in climate and forest coverage were the driving forces behind the drill population decline. Furthermore, the warm temperatures and increased aridity of the Mid Holocene are potentially analogous to current and future conditions faced by many tropical rainforest communities. In order to prevent future declines in population size in rainforest-adapted species such as the drill, large tracts of forest should be protected to both preserve habitat and prevent forest loss through aridification.

Genetic data suggest a natural prehuman origin of open habitats in northern Madagascar and question the deforestation narrative in this region

“…Similar results have also been suggested for other primates [orangutans (81) and howler monkeys (82)]. In all these species [detection of a more ancient population size change is discussed elsewhere (46,47)], the population bottleneck has been reasonably attributed to recent human-driven changes.…”

“…Indeed, the genome retains the specific signature of major events, such as recent contractions (44,45) or ancient expansions (46). Reconstructing the demographic history of extant species may thus help to investigate how climate change and anthropogenic impact affected the dynamic of their habitat (42,47).…”

Strong influence of palaeoclimate on the structure of modern African mammal communities

“…Molecular evidence suggests that shifts in forest vegetation during glacial and interglacial climate change strongly influenced African primates, including vicariance and dispersal in guenons [38,70] and gorillas [36], and demographic patterns in chimpanzees [80] and mandrills [81]. In addition, bioclimatic envelope models of African mammals and birds provide evidence for three major forest refugia in Central and West Africa [40], which would have represented the only viable habitats for most of Africa's primates during glacial periods.…”

Phylogeography, mitochondrial DNA diversity, and demographic history of geladas (Theropithecus gelada)

“…The estimated effective population size was given as N e multiplied by generation time. To get the effective population size, we divided the values by a generation time of 10 years, which is similar to those in drills ( Mandrillus leucophaeus ; 10–12 years, [ 68 ]) or rhesus macaques ( Macaca mulatta ; 11 years, [ 69 ]).…”