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1. Microplastic in riverine fish is connected to species traits

   https://doi.org/10.1038/s41598-018-29980-9  

   McNeish, R. E. ; Kim, L. H. ; Barrett, H. A. ; Mason, S. A. ; Kelly, J. J. ; Hoellein, T. J. ( August 2018 , Scientific Reports)

   Microplastic is a contaminant of concern worldwide. Rivers are implicated as major pathways of microplastic transport to marine and lake ecosystems, and microplastic ingestion by freshwater biota is a risk associated with microplastic contamination, but there is little research on microplastic ecology within freshwater ecosystems. Microplastic uptake by fish is likely affected by environmental microplastic abundance and aspects of fish ecology, but these relationships have rarely been addressed. We measured the abundance and composition of microplastic in fish and surface waters from 3 major tributaries of Lake Michigan, USA. Microplastic was detected in fish and surface waters from all 3 sites, but there was no correlation between microplastic concentrations in fish and surface waters. Rather, there was a significant effect of functional feeding group on microplastic concentration in fish.Neogobius melanostomus(round goby, a zoobenthivore) had the highest concentration of gut microplastic (19 particles fish⁻¹) compared to 10 other fish taxa measured, and had a positive linear relationship between body size and number of microplastic particles. Surface water microplastic concentrations were lowest in the most northern, forested watershed, and highest in the most southern, agriculturally dominated watershed. Results suggest microplastic pollution is common in river food webs and is connected tomore »species feeding characteristics. Future research should focus on understanding the movement of microplastic from point-source and diffuse sources and into aquatic ecosystems, which will support pollution management efforts on inland waters.

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2. Spatial organization of the kelp microbiome at micron scales

   https://doi.org/10.1186/s40168-022-01235-w  

   Ramírez-Puebla, S. Tabita ; Weigel, Brooke L. ; Jack, Loretha ; Schlundt, Cathleen ; Pfister, Catherine A. ; Mark Welch, Jessica L. ( March 2022 , Microbiome)

   Elucidating the spatial structure of host-associated microbial communities is essential for understanding taxon-taxon interactions within the microbiota and between microbiota and host. Macroalgae are colonized by complex microbial communities, suggesting intimate symbioses that likely play key roles in both macroalgal and bacterial biology, yet little is known about the spatial organization of microbes associated with macroalgae. Canopy-forming kelp are ecologically significant, fixing teragrams of carbon per year in coastal kelp forest ecosystems. We characterized the micron-scale spatial organization of bacterial communities on blades of the kelpNereocystis luetkeanausing fluorescence in situ hybridization and spectral imaging with a probe set combining phylum-, class-, and genus-level probes to localize and identify > 90% of the microbial community.

   We show that kelp blades host a dense microbial biofilm composed of disparate microbial taxa in close contact with one another. The biofilm is spatially differentiated, with clustered cells of the dominant symbiontGranulosicoccussp. (Gammaproteobacteria) close to the kelp surface and filamentousBacteroidetesandAlphaproteobacteriarelatively more abundant near the biofilm-seawater interface. A community rich inBacteroidetescolonized the interior of kelp tissues. Microbial cell density increased markedly along the length of the kelp blade, from sparse microbial colonization of newly produced tissues at the meristematic base of the blade to anmore »abundant microbial biofilm on older tissues at the blade tip. Kelp from a declining population hosted fewer microbial cells compared to kelp from a stable population.

   Imaging revealed close association, at micrometer scales, of different microbial taxa with one another and with the host. This spatial organization creates the conditions necessary for metabolic exchange among microbes and between host and microbiota, such as provisioning of organic carbon to the microbiota and impacts of microbial nitrogen metabolisms on host kelp. The biofilm coating the surface of the kelp blade is well-positioned to mediate interactions between the host and surrounding organisms and to modulate the chemistry of the surrounding water column. The high density of microbial cells on kelp blades (10⁵–10⁷cells/cm²), combined with the immense surface area of kelp forests, indicates that biogeochemical functions of the kelp microbiome may play an important role in coastal ecosystems.

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3. Postglacial colonization in the Great Lakes Region by the white-footed mouse ( Peromyscus leucopus ): conflicts between genomic and field data

   https://doi.org/10.1093/jmammal/gyab158  

   Prado, Joyce R. ; Rubi, Tricia L. ; Baumgartner, Joseph ; Hoffman, Susan M. G. ; Dantzer, Ben ; Lacey Knowles, L. ; Baird, ed., Amy ( January 2022 , Journal of Mammalogy)

   For regions that were covered by ice during the Pleistocene glaciations, species must have emigrated from unglaciated regions. However, it can be difficult to discern when and from what ancestral source populations such expansions took place, especially since warming climates introduce the possibility of very recent expansions. For example, in the Great Lakes region, pronounced climatic change includes past glaciations as well as recent, rapid warming. Here we evaluate different expansion hypotheses with a genomic study of the white-footed mouse (Peromyscus leucopus noveboracensis), which is one of the most common mammals throughout the Great Lakes region. Ecological surveys coupled with historical museum records suggest a recent range expansion of P. leucopus associated with the warming climate over the last decades. These detailed records have yet to be complemented by genomic data that provide the requisite resolution for detecting recent expansion, although some mitochondrial DNA (mtDNA) sequences have suggested possible hypotheses about the geography of expansion. With more than 7,000 loci generated using RADseq, we evaluate support for multiple hypotheses of a geographic expansion in the Upper Peninsula of Michigan (UP). Analysis of a single random single-nucleotide polymorphism per locus revealed a fine-scale population structure separating the Lower Peninsula (LP)more »population from all other populations in the UP. We also detected a genetic structure that reflects an evolutionary history of postglacial colonization from two different origins into the UP, one coming from the LP and one coming from the west. Instead of supporting a climate-driven range expansion, as suggested by field surveys, our results support more ancient postglacial colonization of the UP from two different ancestral sources. With these results, we offer new insights about P. leucopus geographic expansion history, as well as a more general phylogeographic framework for testing range shifts in the Great Lakes region.

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4. Genetic diversity and selection in Puerto Rican horses

   https://doi.org/10.1038/s41598-021-04537-5  

   Wolfsberger, Walter W. ; Ayala, Nikole M. ; Castro-Marquez, Stephanie O. ; Irizarry-Negron, Valerie M. ; Potapchuk, Antoliy ; Shchubelka, Khrystyna ; Potish, Ludvig ; Majeske, Audrey J. ; Oliver, Luis Figueroa ; Lameiro, Alondra Diaz ; et al ( January 2022 , Scientific Reports)

   Since the first Spanish settlers brought horses to America centuries ago, several local varieties and breeds have been established in the New World. These were generally a consequence of the admixture of the different breeds arriving from Europe. In some instances, local horses have been selectively bred for specific traits, such as appearance, endurance, strength, and gait. We looked at the genetics of two breeds, the Puerto Rican Non-Purebred (PRNPB) (also known as the “Criollo”) horses and the Puerto Rican Paso Fino (PRPF), from the Caribbean Island of Puerto Rico. While it is reasonable to assume that there was a historic connection between the two, the genetic link between them has never been established. In our study, we started by looking at the genetic ancestry and diversity of current Puerto Rican horse populations using a 668 bp fragment of the mitochondrial DNA D-loop (HVR1) in 200 horses from 27 locations on the island. We then genotyped all 200 horses in our sample for the “gait-keeper”DMRT3mutant allele previously associated with the paso gait especially cherished in this island breed. We also genotyped a subset of 24 samples with the Illumina Neogen Equine Community genome-wide array (65,000 SNPs). This data was further combined with the publicly availablemore »PRPF genomes from other studies. Our analysis show an undeniable genetic connection between the two varieties in Puerto Rico, consistent with the hypothesis that PRNPB horses represent the descendants of the original genetic pool, a mix of horses imported from the Iberian Peninsula and elsewhere in Europe. Some of the original founders of PRNRB population must have carried the “gait-keeper”DMRT3allele upon arrival to the island. From this admixture, the desired traits were selected by the local people over the span of centuries. We propose that the frequency of the mutant “gait-keeper” allele originally increased in the local horses due to the selection for the smooth ride and other characters, long before the PRPF breed was established. To support this hypothesis, we demonstrate that PRNPB horses, and not the purebred PRPF, carry a signature of selection in the genomic region containing theDMRT3locus to this day. The lack of the detectable signature of selection associated with theDMRT3in the PRPF would be expected if this native breed was originally derived from the genetic pool of PRNPB horses established earlier and most of the founders already had the mutant allele. Consequently, selection specific to PRPF later focused on allels in other genes (includingCHRM5, CYP2E1, MYH7, SRSF1, PAM, PRNand others) that have not been previously associated with the prized paso gait phenotype in Puerto Rico or anywhere else.

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5. Arctic greening associated with lengthening growing seasons in Northern Alaska

   https://doi.org/10.1088/1748-9326/ab5e26  

   Arndt, Kyle A. ; Santos, Maria J. ; Ustin, Susan ; Davidson, Scott J. ; Stow, Doug ; Oechel, Walter C. ; Tran, Thao T. P. ; Graybill, Brian ; Zona, Donatella ( December 2019 , Environmental Research Letters)

   Many studies have reported that the Arctic is greening; however, we lack an understanding of the detailed patterns and processes that are leading to this observed greening. The normalized difference vegetation index (NDVI) is used to quantify greening, which has had largely positive trends over the last few decades using low spatial resolution satellite imagery such as AVHRR or MODIS over the pan-Arctic region. However, substantial fine scale spatial heterogeneity in the Arctic makes this large-scale investigation hard to interpret in terms of vegetation and other environmental changes. Here we focus on one area of the northern Alaskan Arctic using high spatial resolution (4 m) multispectral satellite imagery from DigitalGlobe^™to analyze the greening trend near Utqiaġvik (formerly known as Barrow) over 14 years from 2002 to 2016. We found that tundra vegetation has been greening (τ = 0.65,p = 0.01, NDVI increase of 0.01 yr⁻¹) despite no overall change in vegetation community composition. The greening is most closely correlated to the number of thawing degree days (R² = 0.77,F = 21.5,p < 0.001) which increased in a similar linear trend over the 14 year study period (1.79 ± 0.50 days per year,p < 0.01,τ = −0.56). This suggests that in this Arctic ecosystem, greening is occurring due to a lengthening growing season that appears tomore »stimulate plant productivity without any significant change in vegetation communities. We found that vegetation communities in wetter locations greened about twice as fast as those found in drier conditions supporting the hypothesis that these communities respond more strongly to warming. We suggest that in Arctic environments, vegetation productivity may continue to rise, particularly in wet areas.

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