Taxonomic Partition Suggests a High Degree of Coevolution Between Termites and Their Termitophiles

Termites have a tight interaction with their social parasitic Corotocini beetles. This association is thought to be mainly host-specific, despite some host-switch events. By analyzing the taxonomic partition between species and genera of Corotocini, we propose the hypothesis that the main driver of the diversity of these termitophiles is coevolution.

Diversity and Eco-Evolutionary Associations of Endosymbiotic Astome Ciliates With Their Lumbricid Earthworm Hosts

Coevolution of endosymbionts with their hosts plays an important role in the processes of speciation and is among the most fascinating topics in evolutionary biology. Astome ciliates represent an interesting model for coevolutionary studies because they are so tightly associated with their host organisms that they completely lost the cell oral apparatus. In the present study, we used five nuclear markers (18S rRNA gene, ITS1–5.8S–ITS2 region, and 28S rRNA gene) and two mitochondrial genes (16S rRNA gene and cytochrome c oxidase subunit I) to explore the diversity of astomes inhabiting the digestive tract of lumbricid earthworms at temperate latitudes in Central Europe and to cast more light on their host specificity and coevolution events that shaped their diversification. The present coevolutionary and phylogenetic interaction-adjusted similarity analyses suggested that almost every host switch leads to speciation and firm association with the new host. Nevertheless, the suggested high structural host specificity of astomes needs to be tested with increased earthworm sampling, as only 52 out of 735 lumbricid earthworms (7.07%) were inhabited by ciliates. On the other hand, the diversification of astomes associated with megascolecid and glossoscolecid earthworms might have been driven by duplication events without host switching.

An Experimental Test of Defenses Against Avian Brood Parasitism in a Recent Host

Theoretical studies predict that hosts of avian brood parasites should evolve defenses against parasitism in a matter of decades. However, opportunities to test these predictions are limited because brood parasites rarely switch to naïve hosts. Here, we capitalize on a recent host switch by the brood-parasitic Pacific Koel (Eudynamys orientalis) in eastern Australia, to investigate how quickly the Red Wattlebird (Anthochaera carunculata), a recent host that has been annexed by the koel within the last 90 years, can learn to recognize and mob adult cuckoos and evolve the ability to eject parasite eggs. Pacific Koel nestlings kill all host young, so there should be strong selection for hosts to evolve defenses. However, low parasitism rates and high egg recognition costs might slow the spread of egg ejection in our study populations, while adult parasite recognition should be able to spread more rapidly, as this defense has been shown to be a learned trait rather than a genetically inherited defense. We tested Red Wattlebirds at two sites where parasitism rate differed. As predicted, we found that the Red Wattlebird showed little or no ability to eject foreign model eggs at either site, whereas two historical hosts showed high levels of egg ejection at both sites. However, Red Wattlebirds responded significantly more aggressively to a koel mount than to mounts of a harmless control and nest predator at the site with the higher parasitism rate and gave significantly more alarm calls overall toward the koel mount. Our results support previous evidence that recognition and mobbing of a brood parasite are learned traits and may be especially beneficial to naïve hosts that have not had enough time or a high enough selection pressure to evolve egg rejection.

Nosema ceranae - a new threat to honey bees (Apis mellifera)?

Back in 1900 already, the Microsporidium Nosema apis was described inApis mellifera. Thereby the Nosemosis remains without symptoms in the beehive to a certain degree. Studies indicate that infected bees have a shortened lifespan, due to a series of changes in physiological parameters. The consequence of these changes are diarrheal symptoms and the spread of infectious spores in thehive. There is also a seasonal infection course observed, which has its peak in spring time (April, May). Colloquially, the Nosemosis is therefore also known as spring shrinking craze. More recently, a new Nosema species in the European honey bee has been described, where a host-switch from the Asian honey bee A. cerana to A. mellifera has occurred. N. ceranae is blamed for colony losses in the south of Spain, many general colony losses during wintertime in Europe and has also a contribution to the Colony Collapse Disorder (CCD) in the U.S. It seems likely that the original Nosema species (N. apis) is displaced more and more by N. ceranae for unknown reasons. Within the EU project „BEE DOC“, monitoring studies on colonies in southern Germany, Switzerland, southern France, Sweden and Finland were performed. Although the high prevalence of N. ceranae could be confirmed, no increased colony mortality due to Nosemosis was recorded. This was also observed by other colleagues and thus the „new threat“ is open to debate.

Host Ant Change of a Socially Parasitic Butterfly (Phengaris alcon) through Host Nest Take-Over

The socially parasitic Alcon blue butterfly (Phengaris alcon) starts its larval stage by feeding on the seeds of gentians, after which it completes development in the nests of suitable Myrmica ant species. The host plant and host ant species can differ at the population level within a region, and local adaptation is common, but some host switches are observed. It has been suggested that one mechanism of change is through the re-adoption of caterpillars by different ant species, either through occupation of abandoned nests or take-over of established nests by competitively superior colonies. To test this question in the lab we introduced relatively strong colonies (50 workers) of alien Myrmica species to the arenas of weaker colonies (two caterpillars with six workers), and to orphaned caterpillars (two caterpillars without ants). We used caterpillars from a xerophylic population of P. alcon, and both local hosts, M. sabuleti and M. scabrinodis, testing the possibility of host switch between these two host ant species during larval development. Most of the caterpillars were successfully readopted by alien ants, and survived well. Our results suggest higher ecological plasticity in host ant usage of this butterfly than generally thought.

Genomic determinants of pathogenicity in SARS-CoV-2 and other human coronaviruses

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) poses an immediate, major threat to public health across the globe. Here we report an in-depth molecular analysis to reconstruct the evolutionary origins of the enhanced pathogenicity of SARS-CoV-2 and other coronaviruses that are severe human pathogens. Using integrated comparative genomics and machine learning techniques, we identify key genomic features that differentiate SARS-CoV-2 and the viruses behind the two previous deadly coronavirus outbreaks, SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV), from less pathogenic coronaviruses. These features include enhancement of the nuclear localization signals in the nucleocapsid protein and distinct inserts in the spike glycoprotein that appear to be associated with high case fatality rate of these coronaviruses as well as the host switch from animals to humans. The identified features could be crucial contributors to coronavirus pathogenicity and possible targets for diagnostics, prognostication, and interventions.

Genomic determinants of pathogenicity in SARS-CoV-2 and other human coronaviruses

SARS-CoV-2 poses an immediate, major threat to public health across the globe. Here we report an in-depth molecular analysis to reconstruct the evolutionary origins of the enhanced pathogenicity of SARS-CoV-2 and other coronaviruses that are severe human pathogens. Using integrated comparative genomics and machine learning techniques, we identify key genomic features that differentiate SARS-CoV-2 and the viruses behind the two previous deadly coronavirus outbreaks, SARS-CoV and MERS-CoV, from less pathogenic coronaviruses. These features include enhancement of the nuclear localization signals in the nucleocapsid protein and distinct inserts in the spike glycoprotein that appear to be associated with high case fatality rate of these coronaviruses as well as the host switch from animals to humans. The identified features could be crucial elements of coronavirus pathogenicity and possible targets for diagnostics, prognostication and interventions.

Papillomaviruses infecting cetaceans exhibit signs of genome adaptation following a recombination event

Papillomaviruses (PVs) have evolved through a complex evolutionary scenario where virus–host co-evolution alone is not enough to explain the phenotypic and genotypic PV diversity observed today. Other evolutionary processes, such as host switch and recombination, also appear to play an important role in PV evolution. In this study, we have examined the genomic impact of a recombination event between distantly related PVs infecting Cetartiodactyla (even-toed ungulates and cetaceans). Our phylogenetic analyses suggest that one single recombination was responsible for the generation of extant ‘chimeric’ PV genomes infecting cetaceans. By correlating the phylogenetic relationships to the genomic content, we observed important differences between the recombinant and non-recombinant cetartiodactyle PV genomes. Notably, recombinant PVs contain a unique set of conserved motifs in the upstream regulatory region (URR). We interpret these regulatory changes as an adaptive response to drastic changes in the PV genome. In terms of codon usage preferences (CUPrefs), we did not detect any particular differences between orthologous open reading frames in recombinant and non-recombinant PVs. Instead, our results are in line with previous observations suggesting that CUPrefs in PVs are rather linked to gene expression patterns as well as to gene function. We show that the non-coding URR of PVs infecting cetaceans, the central regulatory element in these viruses, exhibits signs of adaptation following a recombination event. Our results suggest that also in PVs, the evolution of gene regulation can play an important role in speciation and adaptation to novel environments.