Virus epidemics can lead to a population‐wide spread of intragenomic parasites in a previously parasite‐free asexual population

Sexual reproduction is problematic to explain due to its costs, most notably the twofold cost of sex. Yet, sex has been suggested to be favourable in the presence of proliferating intragenomic parasites given that sexual recombination provides a mechanism to confine the accumulation of deleterious mutations. Kraaijeveld et al. compared recently the accumulation of transposons in sexually and asexually reproducing lines of the same species, the parasitoid wasp Leptopilina clavipes. They discovered that within asexually reproducing wasps, the number of gypsy‐like retrotransposons was increased fourfold, whereas other retrotransposons were not. Interestingly, gypsy‐like retrotransposons are closely related to retroviruses. Endogenous retroviruses are retroviruses that have integrated to the germ line cells and are inherited thereafter vertically. They can also replicate within the genome similarly to retrotransposons as well as form virus particles and infect previously uninfected cells. This highlights the possibility that endogenous retroviruses could play a role in the evolution of sexual reproduction. Here, we show with an individual‐based computational model that a virus epidemic within a previously parasite‐free asexual population may establish a new intragenomic parasite to the population. Moreover and in contrast to other transposons, the possibility of endogenous viruses to maintain a virus epidemic and simultaneously provide resistance to individuals carrying active endogenous viruses selects for the presence of active intragenomic parasites in the population despite their deleterious effects. Our results suggest that the viral nature of certain intragenomic parasites should be taken into account when sex and its benefits are being considered.     

Marine island biogeography. Response to comment on ‘Island biogeography: patterns of marine shallow‐water organisms’

In this response we have incorporated data on gastropod and seaweed biodiversity referred to by Ávila et al. (2016, Journal of Biogeography, doi: 10.1111/jbi.12816 ) to allow an updated analysis on marine shallow‐water biogeography patterns. When compared to the biogeography patterns reported in Hachich et al. (2015, Journal of Biogeography, 42 , 1871–1882), we find (1) no differences in the patterns originally reported for reef fish or seaweeds, (2) minor differences in gastropod species–area and species–age patterns and (3) a significant difference for the gastropod species‐isolation pattern. In our original work, we reported that there was limited evidence that gastropod species richness was influenced by island isolation; however, our new analysis reveals a power‐model relationship between these variables. Thus, we are now able to conclude that gastropod species diversity, whose dispersal capacity is intermediate between seaweeds (lowest) and reef fish (highest), is also influenced by island isolation.     

Integrating the ‘genomic mosaic’ view of species into studies of biotic interactions: a comment on Bernhardsson et al. ()

The co‐occurrence of geographical structure in herbivore communities, metabolomes and defence genes in forest trees has been analysed in the context of ‘geographical mosaics’ of coevolution. A deeper understanding of these important issues will require full integration of a ‘genomic mosaic’ view of species into community ecology.