ALBERT

Description: Significance Assessing change in Southern Ocean ecosystems is challenging due to its remoteness. Large-scale datasets that allow comparison between present-day conditions and those prior to large-scale ecosystem disturbances caused by humans (e.g., fishing/whaling) are rare. We infer the contemporary offshore foraging distribution of a marine predator, southern right whales (n = 1,002), using a customized stable isotope-based assignment approach based on biogeochemical models of the Southern Ocean. We then compare the contemporary distributions during the late austral summer and autumn to whaling catch data representing historical distributions during the same seasons. We show remarkable consistency of mid-latitude distribution across four centuries but shifts in foraging grounds in the past 30 y, particularly in the high latitudes that are likely driven by climate-associated alterations in prey availability. Abstract Assessing environmental changes in Southern Ocean ecosystems is difficult due to its remoteness and data sparsity. Monitoring marine predators that respond rapidly to environmental variation may enable us to track anthropogenic effects on ecosystems. Yet, many long-term datasets of marine predators are incomplete because they are spatially constrained and/or track ecosystems already modified by industrial fishing and whaling in the latter half of the 20th century. Here, we assess the contemporary offshore distribution of a wide-ranging marine predator, the southern right whale (SRW, Eubalaena australis), that forages on copepods and krill from ~30°S to the Antarctic ice edge (〉60°S). We analyzed carbon and nitrogen isotope values of 1,002 skin samples from six genetically distinct SRW populations using a customized assignment approach that accounts for temporal and spatial variation in the Southern Ocean phytoplankton isoscape. Over the past three decades, SRWs increased their use of mid-latitude foraging grounds in the south Atlantic and southwest (SW) Indian oceans in the late austral summer and autumn and slightly increased their use of high-latitude (〉60°S) foraging grounds in the SW Pacific, coincident with observed changes in prey distribution and abundance on a circumpolar scale. Comparing foraging assignments with whaling records since the 18th century showed remarkable stability in use of mid-latitude foraging areas. We attribute this consistency across four centuries to the physical stability of ocean fronts and resulting productivity in mid-latitude ecosystems of the Southern Ocean compared with polar regions that may be more influenced by recent climate change.

Description: Animal gastrointestinal tracts harbor a microbiome that is integral to host function, yet species from diverse phyla have evolved a reduced digestive system or lost it completely. Whether such changes are associated with alterations in the diversity and/or abundance of the microbiome remains an untested hypothesis in evolutionary symbiosis. Here, using the life history transition from planktotrophy (feeding) to lecithotrophy (nonfeeding) in the sea urchin Heliocidaris, we demonstrate that the lack of a functional gut corresponds with a reduction in microbial community diversity and abundance as well as the association with a diet-specific microbiome. We also determine that the lecithotroph vertically transmits a Rickettsiales that may complement host nutrition through amino acid biosynthesis and influence host reproduction. Our results indicate that the evolutionary loss of a functional gut correlates with a reduction in the microbiome and the association with an endosymbiont. Symbiotic transitions can therefore accompany life history transitions in the evolution of developmental strategies.

Description: Significance: Adaptive radiation, the evolutionary process whereby a lineage diversifies over a short period of time, often occurs in geographically isolated or newly formed habitats where colonizing species encounter unoccupied niches and reduced selective pressures. Rapid radiations may also occur in diverse and complex environments, but these cases are less well documented. Here, we show that the hamlets, a group of Caribbean reef fishes, radiated within the last 10,000 generations in a burst of diversification that ranks among the fastest in fishes. Genomic analysis suggests that color pattern diversity is generated by different combinations of alleles at a few genes with large effect. Such a modular genomic architecture of diversification is emerging as a common denominator to a variety of radiations. Abstract: Rapid diversification is often observed when founding species invade isolated or newly formed habitats that provide ecological opportunity for adaptive radiation. However, most of the Earth’s diversity arose in diverse environments where ecological opportunities appear to be more constrained. Here, we present a striking example of a rapid radiation in a highly diverse marine habitat. The hamlets, a group of reef fishes from the wider Caribbean, have radiated into a stunning diversity of color patterns but show low divergence across other ecological axes. Although the hamlet lineage is ∼26 My old, the radiation appears to have occurred within the last 10,000 generations in a burst of diversification that ranks among the fastest in fishes. As such, the hamlets provide a compelling backdrop to uncover the genomic elements associated with phenotypic diversification and an excellent opportunity to build a broader comparative framework for understanding the drivers of adaptive radiation. The analysis of 170 genomes suggests that color pattern diversity is generated by different combinations of alleles at a few large-effect loci. Such a modular genomic architecture of diversification has been documented before in Heliconius butterflies, capuchino finches, and munia finches, three other tropical radiations that took place in highly diverse and complex environments. The hamlet radiation also occurred in a context of high effective population size, which is typical of marine populations. This allows for the accumulation of new variants through mutation and the retention of ancestral genetic variation, both of which appear to be important in this radiation.

Description: Significance: A central goal in invasion genomics is to identify and determine the mechanisms that underlie the successful colonization, establishment, and subsequent range expansion of invasive populations of nonindigenous species. Using a whole-genome approach, we evaluate the importance of genetic diversity for the successful establishment of nonindigenous species. Our study shows that genetic diversity per se is not the major factor driving invasions, since we observed all possible scenarios with invasive populations showing reduced, similar but also increased, genetic diversity relative to the native population. Using coalescent methods, we reconstruct the demographic history of the invasion and infer the source population of each invasion event, which shows that propagule pressure and multiple introductions play an important role in determining invasion success. Abstract: Invasion rates have increased in the past 100 y irrespective of international conventions. What characterizes a successful invasion event? And how does genetic diversity translate into invasion success? Employing a whole-genome perspective using one of the most successful marine invasive species world-wide as a model, we resolve temporal invasion dynamics during independent invasion events in Eurasia. We reveal complex regionally independent invasion histories including cases of recurrent translocations, time-limited translocations, and stepping-stone range expansions with severe bottlenecks within the same species. Irrespective of these different invasion dynamics, which lead to contrasting patterns of genetic diversity, all nonindigenous populations are similarly successful. This illustrates that genetic diversity, per se, is not necessarily the driving force behind invasion success. Other factors such as propagule pressure and repeated introductions are an important contribution to facilitate successful invasions. This calls into question the dominant paradigm of the genetic paradox of invasions, i.e., the successful establishment of nonindigenous populations with low levels of genetic diversity.

Description: Prochlorococcus is a key member of open-ocean primary producer communities. Despite its importance, little is known about the predators that consume this cyanobacterium and make its biomass available to higher trophic levels. We identify potential predators along a gradient wherein Prochlorococcus abundance increased from near detection limits (coastal California) to 〉200,000 cells mL-1 (subtropical North Pacific Gyre). A replicated RNA-Stable Isotope Probing experiment involving the in situ community, and labeled Prochlorococcus as prey, revealed choanoflagellates as the most active predators of Prochlorococcus, alongside a radiolarian, chrysophytes, dictyochophytes, and specific MAST lineages. These predators were not appropriately highlighted in multiyear conventional 18S rRNA gene amplicon surveys where dinoflagellates and other taxa had highest relative amplicon abundances across the gradient. In identifying direct consumers of Prochlorococcus, we reveal food-web linkages of individual protistan taxa and resolve routes of carbon transfer from the base of marine food webs.

Description: With over 18,000 species, the Acanthomorpha, or spiny-rayed fishes, form the largest and arguably most diverse radiation of vertebrates. One of the key novelties that contributed to their evolutionary success are the spiny rays in their fins that serve as a defense mechanism. We investigated the patterning mechanisms underlying the differentiation of median fin Anlagen into discrete spiny and soft rayed domains during the ontogeny of the direct-developing cichlid fish Astatotilapia burtoni. Distinct transcription factor signatures characterize these two fin domains, whereby mutually exclusive expression of hoxa13a/b with alx4a/b and tbx2b marks the spine to soft-ray boundary. The soft-ray domain is established by BMP inhibition via gremlin1b, which synergizes in the posterior fin with shh secreted from a zone of polarizing activity. Modulation of BMP signaling by chemical inhibition or gremlin1b CRISPR/Cas9 knockout induces homeotic transformations of spines into soft rays and vice versa. The expression of spine and soft-ray genes in nonacanthomorph fins indicates that a combination of exaptation and posterior expansion of an ancestral developmental program for the anterior fin margin allowed the evolution of robustly individuated spiny and soft-rayed domains. We propose that a repeated exaptation of such pattern might underly the convergent evolution of anterior spiny fin elements across fishes.

Description: Significance Resilience to global change will require adaptation to multiple concurrent environmental changes. However, it is unclear if adaptations to multiple stressors can be predicted from the sum of single-stressor adaptation. To answer this question, we experimentally evolved a marine copepod to warming, acidification, and their combination, finding that copepods were able to adapt to all conditions over 25 generations. Warming was a much stronger selective pressure than acidification alone and under multiple-stressor conditions. Nevertheless, the multiple-stressor response to selection was synergistic and unique from either single stressor. Thus, adaptation to single stressors may not reveal adaptive potential or mechanisms of adaptation under multiple stressors, demonstrating the complexity of predicting adaptive responses under multifaceted environmental change. Abstract Metazoan adaptation to global change relies on selection of standing genetic variation. Determining the extent to which this variation exists in natural populations, particularly for responses to simultaneous stressors, is essential to make accurate predictions for persistence in future conditions. Here, we identified the genetic variation enabling the copepod Acartia tonsa to adapt to experimental ocean warming, acidification, and combined ocean warming and acidification (OWA) over 25 generations of continual selection. Replicate populations showed a consistent polygenic response to each condition, targeting an array of adaptive mechanisms including cellular homeostasis, development, and stress response. We used a genome-wide covariance approach to partition the allelic changes into three categories: selection, drift and replicate-specific selection, and laboratory adaptation responses. The majority of allele frequency change in warming (57%) and OWA (63%) was driven by shared selection pressures across replicates, but this effect was weaker under acidification alone (20%). OWA and warming shared 37% of their response to selection but OWA and acidification shared just 1%, indicating that warming is the dominant driver of selection in OWA. Despite the dominance of warming, the interaction with acidification was still critical as the OWA selection response was highly synergistic with 47% of the allelic selection response unique from either individual treatment. These results disentangle how genomic targets of selection differ between single and multiple stressors and demonstrate the complexity that nonadditive multiple stressors will contribute to predictions of adaptation to complex environmental shifts caused by global change.

Description: Mantle-derived noble gases in volcanic gases are powerful tracers of terrestrial volatile evolution, as they contain mixtures of both primordial (from Earth's accretion) and secondary (e.g., radiogenic) isotope signals that characterize the composition of deep Earth. However, volcanic gases emitted through subaerial hydrothermal systems also contain contributions from shallow reservoirs (groundwater, crust, atmosphere). Deconvolving deep and shallow source signals is critical for robust interpretations of mantle-derived signals. Here, we use a novel dynamic mass spectrometry technique to measure argon, krypton, and xenon isotopes in volcanic gas with ultrahigh precision. Data from Iceland, Germany, United States (Yellowstone, Salton Sea), Costa Rica, and Chile show that subsurface isotope fractionation within hydrothermal systems is a globally pervasive and previously unrecognized process causing substantial nonradiogenic Ar-Kr-Xe isotope variations. Quantitatively accounting for this process is vital for accurately interpreting mantle-derived volatile (e.g., noble gas and nitrogen) signals, with profound implications for our understanding of terrestrial volatile evolution.

Description: Published

Description: eadg2566

Description: OSV2: Complessità dei processi vulcanici: approcci multidisciplinari e multiparametrici

Description: JCR Journal

Description: The South Shetland Trough, Antarctica, is an underexplored region for microbiological and biotechnological exploitation. Herein, we describe the isolation and characterization of the novel bacterium Lacinutrix shetlandiensis sp. nov. WUR7 from a deep-sea environment. We explored its chemical diversity via a metabologenomics approach, wherein the OSMAC strategy was strategically employed to upregulate cryptic genes for secondary metabolite production. Based on hybrid de novo whole genome sequencing and digital DNA–DNA hybridization, isolate WUR7 was identified as a novel species from the Gram-negative genus Lacinutrix. Its genome was mined for the presence of biosynthetic gene clusters with limited results. However, extensive investigation of its metabolism uncovered an unusual tryptophan decarboxylase with high sequence homology and conserved structure of the active site as compared to ZP_02040762, a highly specific tryptophan decarboxylase from Ruminococcus gnavus. Therefore, WUR7's metabolism was directed toward indole-based alkaloid biosynthesis by feeding it with L-tryptophan. As expected, its metabolome profile changed dramatically, by triggering the extracellular accumulation of a massive array of metabolites unexpressed in the absence of tryptophan. Untargeted LC-MS/MS coupled with molecular networking, followed along with chemoinformatic dereplication, allowed for the annotation of 10 indole alkaloids, belonging to β-carboline, bisindole, and monoindole classes, alongside several unknown alkaloids. These findings guided us to the isolation of a new natural bisindole alkaloid 8,9-dihydrocoscinamide B (1), as the first alkaloid from the genus Lacinutrix, whose structure was elucidated on the basis of extensive 1D and 2D NMR and HR-ESIMS experiments. This comprehensive strategy allowed us to unlock the previously unexploited metabolome of L. shetlandiensis sp. nov. WUR7.

Description: The Tierra Blanca Joven (TBJ) eruption from Ilopango volcano deposited thick ash over much of El Salvador when it was inhabited by the Maya, and rendered all areas within at least 80 km of the volcano uninhabitable for years to decades after the eruption. Nonetheless, the more widespread environmental and climatic impacts of this large eruption are not well known because the eruption magnitude and date are not well constrained. In this multifaceted study we have resolved the date of the eruption to 431 ± 2 CE by identifying the ash layer in a well-dated, high-resolution Greenland ice-core record that is 〉7,000 km from Ilopango; and calculated that between 37 and 82 km3 of magma was dispersed from an eruption coignimbrite column that rose to ∼45 km by modeling the deposit thickness using state-of-the-art tephra dispersal methods. Sulfate records from an array of ice cores suggest stratospheric injection of 14 ± 2 Tg S associated with the TBJ eruption, exceeding those of the historic eruption of Pinatubo in 1991. Based on these estimates it is likely that the TBJ eruption produced a cooling of around 0.5 °C for a few years after the eruption. The modeled dispersal and higher sulfate concentrations recorded in Antarctic ice cores imply that the cooling would have been more pronounced in the Southern Hemisphere. The new date confirms the eruption occurred within the Early Classic phase when Maya expanded across Central America.

Description: Published

Description: 26061-26068

Description: 1V. Storia eruttiva

Description: JCR Journal