Parker-Nance, S. | Search bioRxiv

bioRxiv2021

Managing human mediated range shifts: understanding spatial, temporal and genetic variation in marine non- native species

The use of molecular methods to manage natural resources is increasingly common. However, DNA-based methods are seldom used to understand the spatial and temporal dynamics of species range shifts. This is important when managing range-shifting species such as non-native species (NNS), which can have negative impacts on biotic communities. Here we investigated the range-shifting NNS Ciona robusta, Clavelina lepadiformis, Microcosmus squamiger and Styela plicata using a combined methodological approach. We first conducted non-molecular biodiversity surveys for these NSS along the South African coastline, and compared the results with historical surveys. We detected no consistent change in range size across species, with some displaying range stability and others showing range shifts. We then sequenced a section of cytochrome c oxidase subunit I (COI) from tissue samples and found genetic differences along the coastline but no change over recent times. Finally, we found that environmental DNA metabarcoding data showed broad congruence with both the non-molecular biodiversity and the COI datasets, but failed to capture complete incidence of all NSS. Overall, we demonstrated how a combined methodological approach can effectively detect spatial and temporal variation in genetic composition and range size, which is key for managing biodiversity changes of both threatened and NSS.

ecology↗

bioRxiv2020

Family matters: The genomes of conserved bacterial symbionts provide insight into specialized metabolic relationships with their sponge host

As the oldest extant metazoans, sponges (Phylum Porifera) have been forming symbiotic relationships with microbes that may date back as far as 700 million years. Most symbionts are conserved within a narrow host range and perform specialized functions. However, there are widely distributed bacterial taxa such as Poribacteria, SAUL and Tethybacterales that are found in a broad range of invertebrate hosts. Here, we added eleven new genomes to the Tethybacterales order, identified a novel family, and show that functional potential differs between the three Tethybacterales families. We compare the Tethybacterales with the well-characterized Entoporibacteria and show that these broad-host range, sponge-associated bacteria likely perform distinct functions within their hosts and that their respective phylogenies are incongruent with their host phylogenies. These results suggests that ancestors of these bacteria may have undergone multiple association events, rather than a single association event followed by co-evolution. IMPORTANCEMarine sponges often form symbiotic relationships with bacteria that fulfil a specific need within the sponge holobiont, and these symbionts are often conserved within a narrow range of related taxa. To date, there exist only three know bacterial taxa (Entoporibacteria, SAUL and Tethybacterales) that are globally distributed and found in a broad range of sponge hosts, and little is known about the latter two. Understanding what distinguishes these broad-host range symbionts from specialized symbionts will provide insight into the mechanisms by which sponges form these symbioses. We show that the functional potential of broad-host range symbionts is conserved at a family level and that these symbionts have been acquired several times over evolutionary history. This contrasts with specialized symbionts, where function is often a strain-specific trait and have co-evolved with their host following a single association event.

microbiology↗