Biology subjects

Rakotoarivony, R.

Publications and source records attributed to Rakotoarivony, R..

4 recordsLinked to original sources

bioRxiv2026

Fine-scale population structure within and among Malagasy societies

The population of Madagascar exhibits a globally unique combination of African and Asian genetic ancestries. Previous studies have described the admixture history of Madagascar at island-wide scales [1,2], but less focus has been paid to fine-scale population structure across the island. We present new genome-wide genetic data from 192 individuals sampled across five regions of Madagascar. We identify population structure at extremely fine spatial scales ([~]10 km) among the Merina of the central highlands. By analysing subpopulations separately, we found one Merina group exhibited similarity to coastal populations in f4 ratios, estimated admixture dates, and pairwise FST distances, while another group was similar to other highland individuals in the same measures. This fine-scale substructure is likely associated with historical coastal-to-highland migration during the 18th and 19th centuries. In contrast, we also observe macro-scale structure in estimated timing of admixture across the island, with southeastern coastal groups exhibiting the earliest estimated admixture timings, and northern groups exhibiting the latest. This pattern corroborates previous results [1,2], and may suggest differing histories of admixture timing among Malagasy populations. Our results emphasise the importance of deep micro-geographic sampling to complement macro-scale analysis when characterising demographic history.

genetics↗

bioRxiv2024

De novo genome assembly for an endangered lemur using portable nanopore sequencing in rural Madagascar

As one of the most threatened mammalian taxa, lemurs of Madagascar are facing unprecedented anthropogenic pressures. To address conservation imperatives such as this, researchers have increasingly relied on conservation genomics to identify populations of particular concern. However, many of these genomic approaches necessitate high-quality genomes. While the advent of next generation sequencing technologies and the resulting reduction of associated costs have led to the proliferation of genomic data and high-quality reference genomes, global discrepancies in genomic sequencing capabilities often result in biological samples from biodiverse host countries being exported to facilities in the Global North, creating inequalities in access and training within genomic research. Here, we present the first reference genome for the endangered red-fronted brown lemur (Eulemur rufifrons) from sequencing efforts conducted entirely within the host country using portable Oxford Nanopore sequencing. Using an archived E. rufifrons specimen, we conducted long-read, nanopore sequencing at the Centre ValBio Research Station near Ranomafana National Park, in rural Madagascar, generating over 750 Gb of sequencing data from 10 MinION flow cells. Exclusively using this long-read data, we assembled 2.21 gigabase, 20,330-contig nuclear assembly with an N50 of 98.9 Mb and a 17,108 bp mitogenome. The nuclear assembly had 31x average coverage and was comparable in completeness to other primate reference genomes, with a 95.47% BUSCO completeness score for primate-specific genes. As the first reference genome for E. rufifrons and the only annotated genome available for the speciose Eulemur genus, this resource will prove vital for conservation genomic studies while our efforts exhibit the potential of this protocol to address research inequalities and build genomic capacity.

genomics↗

bioRxiv2023

Whole-genome Studies of Malagasy People Uncover Novel Body Composition Associations

The majority of human genomic research studies have been conducted in European ancestry cohorts, at the loss of detecting potentially novel and globally impactful findings. Here, we present the first whole genome sequence data and genome-wide association study in a cohort of 264 Malagasy individuals from three locations on the island of Madagascar. We describe genetic variation in this Malagasy cohort, providing insight into the shared and unique patterns of genetic variation across the island. We observe phenotypic variation by location, and find high rates of hypertension particularly in the Southern Highlands as well as elevated malaria prevalence in the West Coast relative to other sites. We find a number of genetic associations with body composition traits, including many variants that are unique to African populations or populations with admixed African ancestry such as Madagascar. This study highlights the utility of including diverse populations in genomic research for the potential to gain novel insights, even with small cohort sizes. This project was conducted in partnership and consultation with local Malagasy stakeholders and serves as an example for equitable genomic research with potential impacts on our understanding of human health and disease.

genomics↗

bioRxiv2023

African bush pigs exhibit porous species boundaries and appeared in Madagascar concurrently with human arrival

Several African mammals exhibit a phylogeographic pattern where closely related taxa are split between West/Central and East/Southern Africa, but their evolutionary relationships and histories remain controversial. Bushpigs (Potamochoerus larvatus) and red river hogs (P. porcus) are recognised as separate species due to morphological distinctions, a perceived lack of interbreeding at contact, and putatively old divergence times, but historically, they were considered conspecific. Moreover, the presence of Malagasy bushpigs as the sole large terrestrial mammal shared with the African mainland raises intriguing questions about its origin and arrival in Madagascar. Analyses of 67 whole genomes revealed a genetic continuum between the two species, with putative signatures of historical gene flow, variable FST values, and a recent divergence time (<500,000 years). Thus, our study challenges key arguments for splitting Potamochoerus into two species and suggests their speciation might be incomplete. Our findings also indicate that Malagasy bushpigs diverged from southern African populations and underwent a limited bottleneck 1,000-5,000 years ago, concurrent with human arrival in Madagascar. These results shed new light on the evolutionary history of an iconic and widespread African genus and provide insight into the longstanding biogeographic puzzle surrounding the bushpigs presence in Madagascar.

evolutionary biology↗