Biology subjects

Nadler, T.

Publications and source records attributed to Nadler, T..

3 recordsLinked to original sources

bioRxiv2026

Ancient admixture catalyzes homoploid hybrid speciation and intense genomic erosion in Asian langurs

Ancient admixture catalyzes evolutionary innovation, yet its long-term genomic consequences for newly formed lineages remain poorly understood. Here, based on 53 genomes covering 19 species of the Asian langur genus Trachypithecus, we explore admixtures role in shaping a reticulated radiation. Genome-wide analyses of phylogenomic triplet topologies demonstrate that phylogenetic discordance across this radiation is primarily driven by widespread introgression rather than incomplete lineage sorting. To mitigate historical noise and resolve the ancestral species tree, we anchored our phylogenetic analysis on the X-linked recombination desert (XLRD), which exhibits an 84.5% introgression reduction compared to autosomes. We identify Delacours langur as a clear case of homoploid hybrid speciation, arising from ancient admixture with [~]70:30 genomic contributions from ancestral northern and southern limestone langur lineages. This hybrid species fixed key reproductive isolation loci; notably, alternate inheritance of pigmentation genes (SLC45A4, HPS5, ADCY10) systematically coupled with a fixed RNF175 chimeric allele to drive its diagnostic pelage phenotype. This illustrates how introgressed multi-gene networks rapidly establish prezygotic visual barriers and profound phenotypic divergence. However, subsequent spatial isolation within fragmented karst landscapes forced a major conversion of genetic burden into realized load. Genome-wide, over 82% of loss-of-function variants occur in a homozygous state, reflecting the expression of lethal recessive mutations within long runs of homozygosity. Together, our findings demonstrate that ancient admixture can trigger homoploid hybrid speciation, yet subsequent ecological restriction locks derived lineages into severe, long-term genomic erosion, revealing a fundamental trade-off in reticulate evolutionary radiations.

evolutionary biology↗

bioRxiv2021

Variation in predicted COVID-19 risk among lemurs and lorises

The novel coronavirus SARS-CoV-2, which in humans leads to the disease COVID-19, has caused global disruption and more than 1.5 million fatalities since it first emerged in late 2019. As we write, infection rates are currently at their highest point globally and are rising extremely rapidly in some areas due to more infectious variants. The primary viral target is the cellular receptor angiotensin-converting enzyme-2 (ACE2). Recent sequence analyses of the ACE2 gene predicts that many nonhuman primates are also likely to be highly susceptible to infection. However, the anticipated risk is not equal across the Order. Furthermore, some taxonomic groups show high ACE2 amino acid conservation, while others exhibit high variability at this locus. As an example of the latter, analyses of strepsirrhine primate ACE2 sequences to date indicate large variation among lemurs and lorises compared to other primate clades despite low sampling effort. Here, we report ACE2 gene and protein sequences for 71 individual strepsirrhines, spanning 51 species and 19 genera. Our study reinforces previous results and finds additional variability in other strepsirrhine species, and suggests several clades of lemurs have high potential susceptibility to SARS-CoV-2 infection. Troublingly, some species, including the rare and Endangered aye-aye (Daubentonia madagascariensis), as well as those in the genera Avahi and Propithecus, may be at high risk. Given that lemurs are endemic to Madagascar and among the primates at highest risk of extinction globally, further understanding of the potential threat of COVID-19 to their health should be a conservation priority. All feasible actions should be taken to limit their exposure to SARS-CoV-2.

genetics↗

bioRxiv2017

Associations Between Nutrition, Gut Microbiome, and Health in A Novel Nonhuman Primate Model

Red-shanked doucs (Pygathrix nemaeus) are endangered, foregut-fermenting colobine primates which are difficult to maintain in captivity. There are critical gaps in our understanding of their natural dietary habits including consumption of leaves, unripe fruit, flowers, seeds, and other plant parts. There is also a lack of understanding of enteric adaptations, including their unique microflora. To address these knowledge gaps, we used the douc as a model to study relationships between gastrointestinal microbial community structure, diet, and health. We analyzed published fecal samples as well as detailed dietary history from doucs with four distinct lifestyles (wild, semi-wild, semi-captive, and captive) and determined gastrointestinal bacterial microbiome composition using 16S rRNA sequencing. A clear gradient of microbiome composition was revealed along an axis of natural lifestyle disruption, including significant associations with diet, health, biodiversity, and microbial function. We identified potential microbial biomarkers of douc dysbiosis, including Bacteroides and Prevotella. Our results suggest a gradient-like shift in captivity causes an attendant shift to severe gut dysbiosis, thereby resulting in gastrointestinal issues.

microbiology↗