It's a dog's life: Canine transmissible venereal tumor is one of the few cancer lineages that is transferred among individuals through contact. It arose millennia ago and has been evolving independently from its hosts ever since. Baez-Ortega et al. looked at the phylogenetic history of the cancer and describe several distinctive mutational patterns (see the Perspective by Maley and Shibata). Most notably, both positive and negative selection show only weak or distant signals. This suggests that the main driver of the lineage's evolution is neutral genetic drift. Understanding the influence of drift may reshape how we think about long-term cancer evolution. Science , this issue p. eaau9923 ; see also p. 440

We identified 3 novel and distinct avulaviruses from Gentoo penguins sampled in Antarctica. We isolated these viruses and sequenced their complete genomes; serologic assays demonstrated that the viruses do not have cross-reactivity between them. Our findings suggest that these 3 new viruses represent members of 3 novel avulavirus species.

The monk parakeet (Myiopsitta monachus) is considered to be one of the most invasive bird species because its unique ability among parrots to build their own communal nests. Currently, they are considered an invasive species in 19 countries and a pest—even in their native distribution—because of economic losses derived from their impacts. During the reproductive seasons of 2017 and 2018, we registered interactions between invasive monk parakeets and resident bird species in Santiago, Chile. We observed agonistic and affiliative interactions, and further, we described monk parakeets’ nest occupancy by nine bird species, two invasive and seven native. For this reason, we consider that the monk parakeet is an allogenic ecosystem engineer with the potential to shape distribution and richness of sympatric species in urban environments. Our results contribute to an assessment of the implications of the monk parakeet’s ecological invasion to other synanthropic species, and raise concern of other potential impacts, such as pathogen transmission derived from these interactions.

Central Chile has been identified as a unique ecosystem with high conservation priority because of its high levels of endemism and intensive anthropic pressure. Over a period of almost four decades, the monk parakeet has been successful in establishing and dispersing in urban Santiago, although little is known about its potential impact. Furthermore, nothing is known about its epidemiological risks towards animals or even humans. For this reason, we conducted the first parasitic survey of monk parakeets in Chile through capture, necropsy and thorough external and internal inspection of 92 adult individuals. Among these, 45.7% presented lice that were identified as Paragoniocotes fulvofasciatum, 1.1% had mesostigmatid acari and 8.9% had free-ranging acari. Among 89 parakeets, 19.1% had structures identified as Cryptosporidium sp. This study provides the first description of Cryptosporidium sp. in monk parakeets. Along with the presence of a mesostigmatid acarus in one parakeet, this serves as a public health warning, given that both of these parasites have zoonotic potential.

Autonomous replication and segregation of mitochondrial DNA (mtDNA) creates the potential for evolutionary conflict driven by emergence of haplotypes under positive selection for ‘selfish’ traits, such as replicative advantage. However, few cases of this phenomenon arising within natural populations have been described. Here, we survey the frequency of mtDNA horizontal transfer within the canine transmissible venereal tumour (CTVT), a contagious cancer clone that occasionally acquires mtDNA from its hosts. Remarkably, one canine mtDNA haplotype, A1d1a, has repeatedly and recently colonised CTVT cells, recurrently replacing incumbent CTVT haplotypes. An A1d1a control region polymorphism predicted to influence transcription is fixed in the products of an A1d1a recombination event and occurs somatically on other CTVT mtDNA backgrounds. We present a model whereby ‘selfish’ positive selection acting on a regulatory variant drives repeated fixation of A1d1a within CTVT cells.