Biology subjects

Kroh, A.

Publications and source records attributed to Kroh, A..

3 recordsLinked to original sources

bioRxiv2026

The fate of a dynasty: Population genomics uncovers the demographic history of Ardea insignis, one of the rarest bird species in the world

The White-bellied Heron (Ardea insignis) is one of the worlds rarest birds, with fewer than 60 known individuals remaining in the wild. Whether this extreme rarity reflects a recent anthropogenic collapse or a long history of persistently small population size has remained unknown, limiting our understanding of the species evolutionary resilience and conservation needs. Here, we present the first high-quality reference genome for A. insignis, generated using Oxford Nanopore long-read sequencing and complemented with Illumina whole-genome data. Comparative mitochondrial and nuclear phylogenomic analyses consistently recover A. insignis as the sister species of Purple Heron (A. purpurea), while revealing moderate mitonuclear discordance among deeper ardeid lineages. Genome-wide analyses demonstrate exceptionally low heterozygosity and extensive runs of homozygosity relative to the widespread and closely related Great Blue Heron (A. herodias), indicating pronounced genomic erosion and long-term inbreeding. However, the predominance of short and intermediate-length homozygous tracts, together with robust Pairwise Sequentially Markovian Coalescent (PSMC) reconstructions across alternative parameterizations, indicates that A. insignis has persisted with comparatively small effective population sizes over much of its evolutionary history rather than experiencing only a recent demographic collapse. The two sampled individuals nevertheless differ in the abundance of longer homozygous tracts, indicating that inbreeding accumulated over the past few generations has not been uniform among the surviving birds, despite their shared history of chronic rarity. Our results indicate that the White-bellied Heron represents a lineage that has survived prolonged demographic adversity and that its greatest genetic challenge may be limited adaptive potential rather than recent genomic deterioration alone. Beyond providing the first genomic resource for this critically endangered species, our study establishes an evolutionary baseline for future monitoring and highlights the importance of integrating genomic and ecological data to guide conservation strategies for species persisting at the edge of extinction.

evolutionary biology↗

bioRxiv2021

Phylogenomic analyses of echinoid diversification prompt a re-evaluation of their fossil record

Echinoids are key components of modern marine ecosystems. Despite a remarkable fossil record, the emergence of their crown group is documented by few specimens of unclear affinities, rendering much of their early history uncertain. The origin of sand dollars, one of its most distinctive clades, is also unclear due to an unstable phylogenetic context and discrepancies between molecular divergence times and fossil evidence. We employ seventeen novel genomes and transcriptomes to build a phylogenomic dataset with a near-complete sampling of major lineages. With it, we revise the phylogeny and divergence times of echinoids, and place their history within the broader context of echinoderm evolution. We also introduce the concept of a chronospace--a multidimensional representation of node ages--and use it to explore the effects of using alternative gene samples, models of molecular evolution, and clock priors. We find the choice of clock model to have the strongest impact on divergence times, while the use of site-heterogeneous models shows little effects. The choice of loci shows an intermediate impact, affecting mostly deep Paleozoic nodes, for which clock-like genes recover dates more congruent with fossil evidence. Our results reveal that crown group echinoids originated in the Permian and diversified rapidly in the Triassic, despite the relative lack of fossil evidence for this early diversification. We also clarify the relationships among sand dollars and their close relatives, showing that the genus Apatopygus represents a relict lineage with a deep Jurassic origin. Surprisingly, the origin of sand dollars is confidently dated to the Cretaceous, implying ghost ranges spanning approximately 50 million years, a remarkable discrepancy with their rich fossil record.

evolutionary biology↗

bioRxiv2020

Enhanced inflammatory response mediated by parenchymal cells associates with resistance towards mTOR inhibition

Activation of the mTOR pathway is frequently found in cancer, but mTOR inhibitors have thus far failed to demonstrate significant antiproliferative efficacy in the majority of cancer types. Besides cancer cell-intrinsic resistance mechanisms, it is conceivable that mTOR inhibitors impact on non-malignant host cells in a manner that ultimately supports resistance of cancer cells. Against this background, we sought to analyze the functional consequences of mTOR inhibition in hepatocytes for the growth of metastatic colon cancer. To this end, we established a liver epithelial cell (LEC)-specific knock-out (KO) of mTOR (mTORLEC mice). We used these mice to characterize the growth of colorectal liver metastases with and without partial hepatectomy to model different clinical settings. While the LEC-specific loss of mTOR remained without effect on metastasis growth in intact liver, partial liver resection resulted in the formation of larger metastases in mTORLEC mice compared to wildtype controls. This was accompanied by significantly enhanced inflammatory activity in LEC-specific mTOR KO livers after partial liver resection. Analysis of NF-{kappa}B target gene expression and immunohistochemistry of p65 displayed a significant activation of NF-{kappa}B in mTORLEC mice, suggesting a functional importance of this pathway for the observed inflammatory phenotype. Taken together, we show an unexpected acceleration of liver metastases upon deletion of mTOR in liver epithelial cells. Our results support the notion that non-malignant host cells can contribute to resistance against mTOR inhibitors and encourage to test if anti-inflammatory drugs are able to improve the efficacy of mTOR inhibitor for cancer therapy.

cancer biology↗