Direct comparisons between historical and contemporary populations allow for detecting changes in genetic diversity through time and assessment of the impact of habitat fragmentation. Here, we determined the genetic architecture of both historical and modern lions to document changes in genetic diversity over the last century. We surveyed microsatellite and mitochondrial genome variation from 143 high-quality museum specimens of known provenance, allowing us to directly compare this information with data from several recently published nuclear and mitochondrial studies. Our results provide evidence for male-mediated gene flow and recent isolation of local subpopulations, likely due to habitat fragmentation. Nuclear markers showed a significant decrease in genetic diversity from the historical (HE=0.833) to the modern (HE=0.796) populations, while mitochondrial genetic diversity was maintained (Hd = 0.98 for both). While the historical population appears to have been panmictic based on nDNA data, hierarchical structure analysis identified four tiers of genetic structure in modern populations and was able to detect most sampling locations. Mitogenome analyses identified 4 clusters: Southern, Mixed, Eastern, and Western; and were consistent between modern and historically sampled haplotypes. Within the last century, habitat fragmentation caused lion subpopulations to become more geographically isolated as human expansion changed the African landscape. This resulted in an increase in fine-scale nuclear genetic structure and loss of genetic diversity as lion subpopulations became more differentiated, while mitochondrial structure and diversity were maintained over time.

Strategies of navigation have been shown to play a critical role when animals revisit resource sites across large home ranges. The habitual route system appears to be a sufficient strategy for animals to navigate while avoiding the cognitive cost of traveling using the Euclidean map. We hypothesize that wild elephants travel more frequently using habitual routes to revisit resource sites as opposed to using the Euclidean map. To identify the elephants' habitual routes, we created a python script, which accounted for frequently used route segments that constituted the habitual routes. Results showed elephant navigation flexibility traveling at Kruger National Park landscape. Elephants shift strategies of navigation depending on the familiarity of their surroundings. In the core area of their home range, elephants traveled using the Euclidean map, but intraindividual differences showed that elephants then converted to habitual routes when navigating within the less familiar periphery of their home range. These findings are analogous to recent experimental results found in smaller mammals that showed that rats encode locations according to their familiarity with their surroundings. Additionally, as recently observed in monkeys, intersections of habitual routes are important locations used by elephants when making navigation decisions. We found a strong association between intersections and new segment usage by elephants when they revisit resource sites, suggesting that intersection choice may contribute to the spatial representations elephants use when repeatedly revisiting resource sites.

The Luangwa Valley in eastern Zambia is a transverse offshoot of the Great Rift Valley system. This region appears to have an isolating effect as evidenced by suspected endemic subspecies, such as the Cookson’s wildebeest and Thornicroft’s giraffe. Recent mitochondrial DNA studies demonstrated that African lions in Zambia consist of two highly diverse eastern and western sub-populations. Herein, we report nuclear and mitochondrial DNA results from 409 lions that support this population substructure across Zambia but proposes only partial isolation of the Luangwa Valley with more movement between the populations than previously thought. Population assignment analysis identifies two populations with little evidence of admixture assigning lions to either the eastern or western sub-populations. A high occurrence of private alleles and clear evidence for a Wahlund effect further justify the presence of a highly structured population. But, while mitochondrial DNA analysis still shows little to no matrilineal gene flow (F ST = 0.53) between sub-populations, microsatellite analysis suggests there is gene flow (F ST = 0.04) with low but significant isolation-by-distance and an average of 6 migrants per generation. Evidence of isolation-by-distance is also found in factorial correspondence analysis with the Lower Zambezi National Park and eastern corridor clusters overlapping isolated clusters of the Luangwa Valley and western sub-population. From this evidence, the Luangwa Valley appears separated from the western sub-population with some dispersal through the southern regions of the eastern sub-population. Both the eastern and western sub-populations have high heterozygosity (0.68 and 0.69, respectively) and genetic diversity (0.47 and 0.50, respectively) values, indicative of genetically healthy populations.

Analysis of DNA sequence diversity at the 12S to 16S mitochondrial genes of 165 African lions (Panthera leo) from five main areas in Zambia has uncovered haplotypes which link Southern Africa with East Africa. Phylogenetic analysis suggests Zambia may serve as a bridge connecting the lion populations in southern Africa to eastern Africa, supporting earlier hypotheses that eastern-southern Africa may represent the evolutionary cradle for the species. Overall gene diversity throughout the Zambian lion population was 0.7319 +/- 0.0174 with eight haplotypes found; three haplotypes previously described and the remaining five novel. The addition of these five novel haplotypes, so far only found within Zambia, nearly doubles the number of haplotypes previously reported for any given geographic location of wild lions. However, based on an AMOVA analysis of these haplotypes, there is little to no matrilineal gene flow (Fst = 0.47) when the eastern and western regions of Zambia are considered as two regional sub-populations. Crossover haplotypes (H9, H11, and Z1) appear in both populations as rare in one but common in the other. This pattern is a possible result of the lion mating system in which predominately males disperse, as all individuals with crossover haplotypes were male. The determination and characterization of lion sub-populations, such as done in this study for Zambia, represent a higher-resolution of knowledge regarding both the genetic health and connectivity of lion populations, which can serve to inform conservation and management of this iconic species.

High-quality reference genomes are fundamental tools for understanding population history, and can provide estimates of genetic and demographic parameters relevant to the conservation of biodiversity. The federally endangered Pacific pocket mouse (PPM), which persists in three small, isolated populations in southern California, is a promising model for studying how demographic history shapes genetic diversity, and how diversity in turn may influence extinction risk. To facilitate these studies in PPM, we combined PacBio HiFi long reads with Omni-C and Hi-C data to generate a de novo genome assembly, and annotated the genome using RNAseq. The assembly comprised 28 chromosome-length scaffolds (N50 = 72.6 MB) and the complete mitochondrial genome, and included a long heterochromatic region on chromosome 18 not represented in the previously available short-read assembly. Heterozygosity was highly variable across the genome of the reference individual, with 18% of windows falling in runs of homozygosity >1 MB, and nearly 9% in tracts spanning >5 MB. Yet outside of runs of homozygosity, heterozygosity was relatively high (0.0027), and historical Ne estimates were large. These patterns of genetic variation suggest recent inbreeding in a formerly large population. Currently the most contiguous assembly for a heteromyid rodent, this reference genome provides insight into the past and recent demographic history of the population, and will be a critical tool for management and future studies of outbreeding depression, inbreeding depression, and genetic load.