When snows bloom: snow algae associated microbial communities are underpinned by trophic partitioning

Snow microbial communities (algae, bacteria, and fungi) play major roles in snow ecosystem processes and are linked to snowmelt dynamics, but patterns and mechanisms underpinning their spatial distributions, community assembly, and maintenance dynamics are poorly understood. Here we examine nival microbial communities and physicochemical measures across a semi-continental scale and across categorical snow algae bloom zones to elucidate interrelation between communities and their environment. Evidence suggests that trophic partitioning may be a major driver of snow community sub-networks. Samples from snows from the Cascade Mountains (USA) and the Rocky Mountains (USA) were collected from active red snow algae blooms from the center of the bloom (medial), from the edge of the bloom (peripheral), and in adjacent ‘white’ snow. Medial sections of snow algae blooms show increased levels of anemophilous bisaccate pollen, lower oxidation-reduction potential, decreased algal and increased bacterial richness, and increased levels of potassium. Fungal communities between the Cascade and Rocky Mountains are distinct but bacterial and algal communities show little intracontinental differentiation. Ecological modules were identified using a weighted gene co-expression analysis (WGCNA), which shows that dominant microbial consortia correlate differentially to environmental parameters, suggesting complex subcommunities drive observed ecological patterns. Individual OTU networks (fungi and bacteria) show high levels of network connectivity compared to networks based on the snow algae Sanguina nivaloides, which underscores associative differences between algal dominated networks and other OTU networks, indicative of trophic partitioning.

Extensive Diversity and Disparity of the Early Miocene Platanistoids (Cetacea, Odontoceti) in the Southeastern Pacific (Chilcatay Formation, Peru)

Several aspects of the fascinating evolutionary history of toothed and baleen whales (Cetacea) are still to be clarified due to the fragmentation and discontinuity (in space and time) of the fossil record. Here we open a window on the past, describing a part of the extraordinary cetacean fossil assemblage deposited in a restricted interval of time (19–18 Ma) in the Chilcatay Formation (Peru). All the fossils here examined belong to the Platanistoidea clade as here redefined, a toothed whale group nowadays represented only by the Asian river dolphin Platanista gangetica. Two new genera and species, the hyper-longirostrine Ensidelphis riveroi and the squalodelphinid Furcacetus flexirostrum, are described together with new material referred to the squalodelphinid Notocetus vanbenedeni and fragmentary remains showing affinities with the platanistid Araeodelphis. Our cladistic analysis defines the new clade Platanidelphidi, sister-group to Allodelphinidae and including E. riveroi and the clade Squalodelphinidae + Platanistidae. The fossils here examined further confirm the high diversity and disparity of platanistoids during the early Miocene. Finally, morphofunctional considerations on the entire platanistoid assemblage of the Chilcatay Formation suggest a high trophic partitioning of this peculiar cetacean paleocommunity.