An Introduction to the Callithrix Genus and Overview of Recent Advances in Marmoset Research

Abstract

We provide here a current overview of marmoset (Callithrix) evolution, hybridization, species biology, basic/biomedical research, and conservation initiatives. Composed of two subgroups, the aurita group (C. aurita and C. flaviceps) and the jacchus group (C. geoffroyi, C. jacchus, C. kuhlii and C. penicillata), this relatively young primate radiation is endemic to the Brazilian Cerrado, Caatinga, and Atlantic Forest biomes. Significant impacts on Callithrix within these biomes resulting from anthropogenic activity include: (1) population declines, particularly for the aurita group; (2) widespread geographic displacement, biological invasions, and range expansions of C. jacchus and C. penicillata; (3) anthropogenic hybridization; and (4) epizootic Yellow Fever and Zika viral outbreaks. A number of Brazilian legal and conservation initiatives are now in place to protect the threatened aurita group and increase research about them. Due to their small size and rapid life history, marmosets are prized biomedical models. As a result, there are increasingly sophisticated genomic Callithrix resources available and burgeoning marmoset functional, immuno-, and epi- genomic research. In both the laboratory and the wild, marmosets have given us insight into cognition, social group dynamics, human disease, and pregnancy. Callithrix jacchus and C. penicillata are emerging Neotropical primate models for arbovirus disease, including Dengue and Zika. Wild marmoset populations are helping us understand sylvatic transmission and human spillover of Zika and Yellow Fever viruses. All of these factors are positioning marmosets as preeminent models to facilitate understanding of facets of evolution, hybridization, conservation, human disease, and emerging infectious diseases.

Genomic Skimming and Nanopore Sequencing Uncover Cryptic Hybridization in One of World’s Most Threatened Primates

“…As can be seen from Figure 1, the phenotype of C. aurita is distinct from that of C. jacchus and C. penicillata, which are commonly found as invasive, exotic species in the natural range of C. aurita. Morphologically, the individual was within the expected body weight range for C. aurita (approximately 450g) 8 . Other Callithrix species tend to weight relatively much less (200-300g) 8 .…”

“…Morphologically, the individual was within the expected body weight range for C. aurita (approximately 450g) 8 . Other Callithrix species tend to weight relatively much less (200-300g) 8 .…”

“…Zoological records state that the individual originates from São Jose dos Campos, SP (Figure 1). Based on previous phenotypic and morphological description of the species 7,8,17 , we initially identified the individual as C. aurita. The individual had the yellow ear tufts characteristic of C. aurita, as well as yellow pelage above the forehead, and other yellow patches around the facial region 17 .…”

“…In this work, we aimed to develop a rapid, cost-effective protocol to obtain genomic data for one of the world's most endangered primates, the small buffy-tufted-ear marmoset C. aurita (Figure 1), for which there is relatively little genetic knowledge. This species is native to the mountainous regions of southeastern Brazil 6,7,8 , and there are about 10,000 mature C. aurita remaining in the wild 9 . The IUCN Red List considers this species Endangered, and C. aurita conservation threats include habitat deforestation, urbanization, and logging 9 .…”

“…Most Callithrix genetic work is based on phylogenetic analysis of short mitochondrial DNA (mtDNA) regions such as COI, COII, and the control region to resolve phylogenetic relationships (e.g., 10,13,14,15 ). However, due to the relatively recent divergence times between Callithrix mtDNA lineages 8,16 , these Callithrix phylogenies usually show polytomies or lack strong statistical support. Nonetheless, mitogenomics alleviates some of these difficulties in Callithrix phylogenetics studies 7,16 , and the C. aurita mitogenome was recently assembled and annotated with Sanger sequencing and short-read high-throughput sequencing 7 .…”