The distribution of major clades of Prochlorococcus tracks light, temperature and other environmental variables; yet, the drivers of genomic diversity within these ecotypes and the net effect on biodiversity of the larger community are poorly understood. We examined high light (HL) adapted Prochlorococcus communities across spatial and temporal environmental gradients in the Pacific Ocean to determine the ecological drivers of population structure and diversity across taxonomic ranks. We show that the Prochlorococcus community has the highest diversity at low latitudes, but seasonality driven by temperature, day length and nutrients adds complexity. At finer taxonomic resolution, some 'sub-ecotype' clades have unique, cohesive responses to environmental variables and distinct biogeographies, suggesting that presently defined ecotypes can be further partitioned into ecologically meaningful units. Intriguingly, biogeographies of the HL-I sub-ecotypes are driven by unique combinations of environmental traits, rather than through trait hierarchy, while the HL-II sub-ecotypes appear ecologically similar, thus demonstrating differences among these dominant HL ecotypes. Examining biodiversity across taxonomic ranks reveals high-resolution dynamics of Prochlorococcus evolution and ecology that are masked at phylogenetically coarse resolution. Spatial and seasonal trends of Prochlorococcus communities suggest that the future ocean may be comprised of different populations, with implications for ecosystem structure and function.

ABSTRACT1. Species reintroductions are an increasingly fashionable tool among conservation practitioners for restoring locally and nationally extinct populations. For a reintroduction programme to be successful, an understanding of the causes of the decline of a species is required. This, however, proves challenging when baseline data on the distribution and abundance of the species are limited.2. This paper uses evidence from historical literature to map the former distribution of the burbot (Lota lota) within UK rivers before its extinction in the early 1970s. A scoring system was developed to model anecdotal descriptions of burbot abundance from the collected literature.3. The former distribution was divided into four geographical areas based loosely on catchment boundaries. The literature identifies 42 rivers in eastern England in which the burbot was likely to have existed. The status of the species in the Thames catchment is still unclear as information from written sources is contradicted by evidence from the archaeological record.4. The findings indicate that the year of source data was a significant predictor of burbot abundance across the former population as a whole and for three of the four geographical areas (the Trent catchment, the Fenland rivers and the Yorkshire rivers). The timing of the burbot's decline showed differences between the geographical regions, with the Trent catchment exhibiting an earlier decline than the Fenland and Yorkshire areas.

Angiogenic sprouting is a critical process involved in vascular network formation within tissues. During sprouting, tip cells and ensuing stalk cells migrate collectively into the extracellular matrix while preserving cell–cell junctions, forming patent structures that support blood flow. Although several signaling pathways have been identified as controlling sprouting, it remains unclear to what extent this process is mechanoregulated. To address this question, we investigated the role of cellular contractility in sprout morphogenesis, using a biomimetic model of angiogenesis. Three-dimensional maps of mechanical deformations generated by sprouts revealed that mainly leader cells, not stalk cells, exert contractile forces on the surrounding matrix. Surprisingly, inhibiting cellular contractility with blebbistatin did not affect the extent of cellular invasion but resulted in cell–cell dissociation primarily between tip and stalk cells. Closer examination of cell–cell junctions revealed that blebbistatin impaired adherens-junction organization, particularly between tip and stalk cells. Using CRISPR/Cas9-mediated gene editing, we further identified NMIIA as the major isoform responsible for regulating multicellularity and cell contractility during sprouting. Together, these studies reveal a critical role for NMIIA-mediated contractile forces in maintaining multicellularity during sprouting and highlight the central role of forces in regulating cell–cell adhesions during collective motility.

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