Biology subjects

Jahnke, M.

Publications and source records attributed to Jahnke, M..

3 recordsLinked to original sources

bioRxiv2024

Connectivity and population structure in a marginal sea - a review

The current biodiversity crisis calls for conservation measures that limit the negative human impact on important habitats and sensitive wild populations. To effectively protect biodiversity at all levels, including intraspecific diversity, conservation measures should be aligned with the connectivity and genetic structure of wild populations. In this review, we synthesise scientific literature on the connectivity and population structure of marine species in the Skagerrak - a marginal sea in the northeast Atlantic Ocean. We discuss the results in relation to the current management practices in the region, as well as the general transferability of our findings. The Skagerrak is one of the most intensively studied regions within this research field, and our findings show that the overall connectivity with adjacent seas is high, but asymmetric, for most species. Simultaneously, most species have populations in the Skagerrak distinct from both each other, and those in adjacent seas. Most of this population structure is associated with the convoluted Skagerrak coastline - population structure is common both among coastal populations and between coastal and offshore populations. In many mobile species, multiple populations are temporally sympatric in certain areas, but retain their genetic divergence through natal homing or other barriers to gene flow. The presence of population structure despite high connectivity is a challenge for area-based protection measures, and calls for temporally flexible management that also monitors intraspecific genetic diversity on multiple timescales.

ecology↗

bioRxiv2022

Ocean currents drive the worldwide colonization of the most widespread marine plant, eelgrass (Zostera marina)

Currents are unique drivers of oceanic phylogeography and so determine the distribution of marine coastal species, along with past glaciations and sea level changes. Here, we reconstruct the worldwide colonization history of eelgrass (Zostera marina L.), the most widely distributed marine flowering plant or seagrass from its origin in the Northwest Pacific, based on nuclear and chloroplast genomes. We identified two divergent Pacific clades with evidence for admixture along the East Pacific coast. Multiple west to east (trans-Pacific) colonization events support the key role of the North Pacific Current. Time-calibrated nuclear and chloroplast phylogenies yielded concordant estimates of the arrival of Z. marina in the Atlantic through the Canadian Arctic, suggesting that eelgrass-based ecosystems, hotspots of biodiversity and carbon sequestration, have only been present since [~]208 Kya (thousand years ago). Mediterranean populations were founded [~]53 Kya while extant distributions along western and eastern Atlantic shores coincide with the end of the Last Glacial Maximum ([~]20 Kya). The recent colonization and 5-to 7-fold lower genomic diversity of Atlantic compared to the Pacific populations raises concern and opportunity about how Atlantic eelgrass might respond to rapidly warming coastal oceans.

evolutionary biology↗

bioRxiv2022

Finding coarse and fine scale population structure in a coastal species: population demographics meets genomics

Population genetic studies often focus on patterns at a regional scale and use spatially aggregated samples to draw inferences about population structure and drivers, potentially masking ecologically relevant population sub-structure and dynamics. In this study we use a multidisciplinary approach combining genomic, demographic, and habitat data with an oceanographic particle drift model, to unravel the patterns of genetic structure at different scales in the black goby (Gobius niger) along the Norwegian coast. Using a high-density sampling protocol, we observed restricted gene flow both at a surprisingly fine (kms) and large (100s km) scale. Our results showed a pattern of isolation by distance related to the level of exposure along the Skagerrak coast, where sheltered sampling stations had an overall level of genetic divergence about three times higher (FST =0.0046) than levels observed among exposed samples (FST =0.0015). These results were corroborated by demographic analyses which showed that population-fluctuations decrease in synchrony with distance at much smaller scales for sheltered samples (20 km) than for exposed sites (80 km), suggesting higher population connectivity among exposed sites. We also found a pronounced genetic discontinuity between populations along the Norwegian west and east coasts, with a sharp "break" around the southern tip of Norway, likely driven both by lack of habitat and by oceanographic features.

genomics↗