Coral reefs worldwide are threatened by thermal stress caused by climate change. Especially devastating periods of coral loss frequently occur during El Niño‐Southern Oscillation (ENSO) events ...originating in the Eastern Tropical Pacific (ETP). El Niño‐induced thermal stress is considered the primary threat to ETP coral reefs. An increase in the frequency and intensity of ENSO events predicted in the coming decades threatens a pan‐tropical collapse of coral reefs. During the 1982–1983 El Niño, most reefs in the Galapagos Islands collapsed, and many more in the region were decimated by massive coral bleaching and mortality. However, after repeated thermal stress disturbances, such as those caused by the 1997–1998 El Niño, ETP corals reefs have demonstrated regional persistence and resiliency. Using a 44 year dataset (1970–2014) of live coral cover from the ETP, we assess whether ETP reefs exhibit the same decline as seen globally for other reefs. Also, we compare the ETP live coral cover rate of change with data from the maximum Degree Heating Weeks experienced by these reefs to assess the role of thermal stress on coral reef survival. We find that during the period 1970–2014, ETP coral cover exhibited temporary reductions following major ENSO events, but no overall decline. Further, we find that ETP reef recovery patterns allow coral to persist under these El Niño‐stressed conditions, often recovering from these events in 10–15 years. Accumulative heat stress explains 31% of the overall annual rate of change of living coral cover in the ETP. This suggests that ETP coral reefs have adapted to thermal extremes to date, and may have the ability to adapt to near‐term future climate‐change thermal anomalies. These findings for ETP reef resilience may provide general insights for the future of coral reef survival and recovery elsewhere under intensifying El Niño scenarios.
El Niño is the main threat to coral reefs in the Eastern Tropical Pacific (ETP), but it is unknown if the coral cover decreases in the long term due to El Niño‐induced thermal stress. Based on a 44 year time‐series analysis of live coral cover (1970–2014), we determine that, unlike in the Caribbean and the Indo‐Pacific, coral reefs in the ETP do not show a long‐term decline. Our analysis indicates that ETP coral reefs show recovery patterns of 10–15 years, allowing them to persist under El Niño‐stressed conditions. We explore some possible explanations for this resilience to thermal stress.
Long-distance dispersal is believed to strongly influence coral reef population dynamics across the Tropical Pacific. However, the spatial scale and strength at which populations are potentially ...connected by dispersal remains uncertain. To determine the patterns in connectivity between the Eastern (ETP) and Central Tropical Pacific (CTP) ecoregions, we used a biophysical model incorporating ocean currents and larval biology to quantify the seascape-wide dispersal potential among all population. We quantified the likelihood and determined the oceanographic conditions that enable the dispersal of coral larvae across the Eastern Pacific Barrier (EP-Barrier) and identified the main connectivity pathways and their conservation value for dominant reef-building corals. Overall, we found that coral assemblages within the CTP and ETP are weakly connected through dispersal. Although the EP-Barrier isolates the ETP from the CTP ecoregion, we found evidence that the EP-Barrier may be breached, in both directions, by rare dispersal events. These rare events could explain the evolutionary genetic similarity among populations of pocilloporids in the ecoregions. Moreover, the ETP may function as a stronger source rather than a destination, providing potential recruits to CTP populations. We also show evidence for a connectivity loop in the ETP, which may positively influence long-term population persistence in the region. Coral conservation and management communities should consider eight-key stepping stone ecoregions when developing strategies to preserve the long-distance connectivity potential across the ETP and CTP.
Abstract
Anthozoan cnidarians (corals and sea anemones) include some of the world’s most important foundation species, capable of building massive reef complexes that support entire ecosystems. ...Although previous molecular phylogenetic analyses have revealed widespread homoplasy of the morphological characters traditionally used to define orders and families of anthozoans, analyses using mitochondrial genes or rDNA have failed to resolve many key nodes in the phylogeny. With a fully resolved, time-calibrated phylogeny for 234 species constructed from hundreds of ultraconserved elements and exon loci, we explore the evolutionary origins of the major clades of Anthozoa and some of their salient morphological features. The phylogeny supports reciprocally monophyletic Hexacorallia and Octocorallia, with Ceriantharia as the earliest diverging hexacorals; two reciprocally monophyletic clades of Octocorallia; and monophyly of all hexacoral orders with the exception of the enigmatic sea anemone Relicanthus daphneae. Divergence dating analyses place Anthozoa in the Cryogenian to Tonian periods (648–894 Ma), older than has been suggested by previous studies. Ancestral state reconstructions indicate that the ancestral anthozoan was a solitary polyp that had bilateral symmetry and lacked a skeleton. Colonial growth forms and the ability to precipitate calcium carbonate evolved in the Ediacaran (578 Ma) and Cambrian (503 Ma) respectively; these hallmarks of reef-building species have subsequently arisen multiple times independently in different orders. Anthozoans formed associations with photosymbionts by the Devonian (383 Ma), and photosymbioses have been gained and lost repeatedly in all orders. Together, these results have profound implications for the interpretation of the Precambrian environment and the early evolution of metazoans.Bilateral symmetry; coloniality; coral; early metazoans; exon capture; Hexacorallia; Octocorallia photosymbiosis; sea anemone; ultraconserved elements.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Switch between Morphospecies of Pocillopora Corals Paz-García, David A.; Hellberg, Michael E.; García-de-León, Francisco J. ...
The American naturalist,
09/2015, Letnik:
186, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Pocillopora corals are the main reef builders in the eastern tropical Pacific. The validity of Pocillopora morphospecies remains under debate because of disagreements between morphological and ...genetic data. To evaluate the temporal stability of morphospecies in situ, we monitored the shapes of individual colonies in three communities in the southern Gulf of California for 44 months. Twenty-three percent of tagged colonies of Pocillopora damicornis changed to Pocillopora inflata morphology during this time. This switch in identity coincided with a shift to a higher frequency of storms and lower water turbidity (i.e., lower chlorophyll a levels). Seven months after the switch, P. inflata colonies were recovering their original P. damicornis morphology. All colonies of both morphospecies shared a common mitochondrial identity, but most P. damicornis colonies undergoing change were at a site with low-flow conditions. This is the first in situ study to document switching between described morphospecies, and it elucidates the influence of temporal shifts in environmental conditions on morphologically plastic responses.
The conclusions reached by a diverse group of scientists who attended an intense 2‐day workshop on hybrid organic–inorganic perovskites are presented, including their thoughts on the most burning ...fundamental and practical questions regarding this unique class of materials, and their suggestions on various approaches to resolve these issues.
As climatic variation re‐shapes global biodiversity, understanding eco‐evolutionary feedbacks during species range shifts is of increasing importance. Theory on range expansions distinguishes between ...two different forms: “pulled” and “pushed” waves. Pulled waves occur when the source of the expansion comes from low‐density peripheral populations, while pushed waves occur when recruitment to the expanding edge is supplied by high‐density populations closer to the species' core. How extreme events shape pushed/pulled wave expansion events, as well as trailing‐edge declines/contractions, remains largely unexplored. We examined eco‐evolutionary responses of a marine invertebrate (the owl limpet, Lottia gigantea) that increased in abundance during the 2014–2016 marine heatwaves near the poleward edge of its geographic range in the northeastern Pacific. We used whole‐genome sequencing from 19 populations across >11 degrees of latitude to characterize genomic variation, gene flow, and demographic histories across the species' range. We estimated present‐day dispersal potential and past climatic stability to identify how contemporary and historical seascape features shape genomic characteristics. Consistent with expectations of a pushed wave, we found little genomic differentiation between core and leading‐edge populations, and higher genomic diversity at range edges. A large and well‐mixed population in the northern edge of the species' range is likely a result of ocean current anomalies increasing larval settlement and high‐dispersal potential across biogeographic boundaries. Trailing‐edge populations have higher differentiation from core populations, possibly driven by local selection and limited gene flow, as well as high genomic diversity likely as a result of climatic stability during the Last Glacial Maximum. Our findings suggest that extreme events can drive poleward range expansions that carry the adaptive potential of core populations, while also cautioning that trailing‐edge extirpations may threaten unique evolutionary variation. This work highlights the importance of understanding how both trailing and leading edges respond to global change and extreme events.
Owl limpets expanded their range northward with a marine heatwave in the Eastern Pacific. Ocean current anomalies may have allowed a large number of individuals from across the species' range to recruit to the northern edge, likely leading to higher population viability in the expanded range. The southern edge of the species' range is a unique evolutionary population, with potentially warm‐adapted genes that might be lost due to ongoing climate change impacts.
Abstract
Aim
The biogeography of predator‐induced defences is an understudied area of predator–prey dynamics. Range overlap with predators that induce the response and local demographics (e.g., prey ...abundances) are likely to be important factors for determining the biogeographic distribution of induced defences within species. However, with climate warming, range‐expanding warm‐water predators are increasingly preying upon temperate species. This is a consequence of a wider phenomenon known as tropicalisation. We aim to determine: (i) if individuals of a temperate barnacle with induced defences (‘bent morphs’) are primarily present where they co‐occur with range‐expanding warm‐water predators (muricid snails) and, (ii) if bent morphs are size‐structured within populations.
Location
North‐eastern Pacific rocky intertidal zone (~26–40° N).
Taxon
Tetraclita rubescens
(Nilsson‐Cantell, 1931), Balanomorpha.
Methods
We use photoquadrats from sites across the range of
T. rubescens
to determine the biogeographic distribution of populations with bent morphs and to assess size‐structure. We use a combination of field surveys, literature, and museum occurrences to assess range overlap between cool and warm‐water predators of
T. rubescens
and their association with populations with bent morphs and abundance patterns of
T. rubescens
.
Results
Bent morphs are commonly found within the equatorward portion of the species' range (where abundances are highest), in populations overlapping with range‐expanding warm‐water predators. Bent morphs primarily occur within the smaller size classes.
Main conclusions
To be partly resilient to the effects of tropicalisation, temperate prey must acclimatise/adapt to altered predator–prey dynamics. Predator‐induced defences are one way to do this. We show that bent morphs within a temperate prey species (
T. rubescens
) are largely restricted to populations that overlap with large‐bodied and range‐expanding warm‐water predators. This is evidence for the partial resilience of
T. rubescens
to tropicalisation and provides the rationale for further exploration of the eco‐evolutionary consequences of tropicalisation in this study system and others.
Objetivo
La biogeografía de las defensas inducidas por depredación es poco estudiada en la dinámica depredador‐presa. Es problable que el traslape de la distribución de depredadores y las características demográficas locales determinene la distribución biogeográfica local como la abundancia de presas. Con el cambio climático, los depredadores con afinidad tropical aumentan el traslape con presas de afinidad templada. Esto es un efecto indirecto conocido como tropicalización. Pretendemos determinar: (i) si la morfología de defensa inducida (‘morfotipo curvo’), de balanos con afinidad templada solo están presentes en poblaciones donde la distribución se traslapa con depredadores con afinidad tropical expandiendo su rango de distribución al norte (caracoles murícidos) y, (ii) si el morfotipo curvo tiene una estructura de talla dentro de sus poblaciones.
Ubicación
Zona intermareal rocosa del Pacífico Nororiental (~26–40° N).
Taxón
Tetraclita rubescens
(Nilsson‐Cantell, 1931), Balanomorpha.
Métodos
Determinamos la estructura de tallas y distribución geográfica de las poblaciones con el morfotipo curvo del balano templado
T. rubescens
con foto‐cuadrantes. Combinamos campo, literatura y registros de museos para evaluar los patrones de abundancia y distribución geográfica del morfotipo curvo y su traslape con depredadores de afinidad templada y tropical.
Resultados
El morfotipo curvo como defensa inducida se encuentra principalmente en tallas pequeñas al sur del rango de distribución de la especie (donde la abundancia es más alta) y en poblaciones donde se traslapa con la expansión norteña de los depredadores con afinidad tropical.
Principales conclusiones
Para ser parcialmente resiliente a los efectos de la tropicalización, las presas con afinidad templada deben encontrar formas de aclimatarse/adaptarse ante las dinámicas de depredación‐presa. Una forma de hacer esto son las defensas inducidas por depredación. Demostramos que el morfotipo curvo de (
T. rubescens
) están restringida a poblaciones que se sobrelapan con la expansión norteña de los depredadores de mayor tamaño con afinidad tropical. Esto evidencía la resiliencia parcial de esta especie y proporciona la base para explorar las consecuencias eco‐evolutivas de la tropicalización.
Antimalarial drug resistance has historically arisen through convergent
mutations in
parasite populations in Southeast Asia and South America. For the past decade in Southeast Asia, artemisinins, the ...core component of first-line antimalarial therapies, have experienced delayed parasite clearance associated with several
mutations, primarily C580Y. We report that mutant
has emerged independently in Guyana, with genome analysis indicating an evolutionary origin distinct from Southeast Asia.
C580Y parasites were observed in 1.6% (14/854) of samples collected in Guyana in 2016-2017. Introducing
C580Y or R539T mutations by gene editing into local parasites conferred high levels of
artemisinin resistance.
growth competition assays revealed a fitness cost associated with these
variants, potentially explaining why these resistance alleles have not increased in frequency more quickly in South America. These data place local malaria control efforts at risk in the Guiana Shield.
Aim
The poleward range expansion of tropical species, and range contraction of temperate species (known as tropicalisation) has mainly been studied from an ecological perspective, with little ...research on its genetic consequences. Here, we used distributional and genetic data to document the consequences of tropicalisation in rocky shore gastropods and assess more broadly the future implications of tropicalisation on phylogeographic patterns.
Location
Nineteen sampling sites along >3000 km of the eastern Pacific rocky intertidal zone, from the tip of the Baja California Peninsula to southern California.
Taxon
Temperate gastropods: Lottia conus, L. strigatella, Fissurella volcano and Tegula gallina.
Tropical gastropods: Fissurella rubropicta, Nerita funiculata and N. scabricosta.
Methods
We determine historical and modern distributions of tropical and temperate species by combining historical records with current field surveys. Using a section of the cytochrome oxidase subunit I gene, we utilised comparative phylogeography, analysis of molecular variance, FST pairwise comparison, mismatch distributions of haplotype differences and neutrality tests to detect genetic signatures of tropicalisation and to better understand its consequences.
Results
We identified range contractions in two temperate species and range expansion in all three tropical species. We detected genetic signatures of range expansion in the tropical species through unimodal distributions of pairwise haplotype differences and strongly negative values for the Fu and Li D and F* statistics. We found population subdivision and phylogeographic breaks in three temperate species, although the geographic location of the breaks differed among species.
Main Conclusions
Genetic signatures and field surveys indicate recent range expansions in tropical species, supporting tropicalisation along the studied coastline. Conversely, we found phylogeographic breaks in temperate species, suggesting that tropicalisation may cause genetic erosion of evolutionary distinct lineages with range‐contraction. The different locations of the phylogeographic breaks among temperate species suggests that some barriers are species specific.
RESUMEN
Objetivo
La expansión del área de distribución hacia los polos de especies tropicales y la contracción del área de distribución de especies de zonas templadas (conocidas como el proceso de tropicalización), se ha estudiado principalmente desde una perspectiva ecológica, mientras que poco se sabe sobre sus consecuencias genéticas. Aquí utilizamos datos de distribución e información genética para documentar las consecuencias de la tropicalización en gasterópodos de costas rocosas, evaluando de manera amplia las futuras implicaciones de la tropicalización sobre los patrones filogeográficos.
Ubicación
Diecinueve sitios de muestreo a lo largo de >3000 km de zonas rocosas intermareales del Pacífico oriental a lo largo de la península de Baja California.
Taxón
Gasterópodos de clima templado: Lottia conus, L. strigatella, Fissurella volcano y Tegula gallina.
Gasterópodos tropicales: Fissurella rubropicta, Nerita funiculata y N. scabricosta.
Métodos
Se determinaron las distribuciones históricas y recientes de las especies tropicales y templadas combinando los registros históricos con los monitoreos recientemente realizados en el intermareal. Se utilizó una sección del gen de la subunidad I del citocromo oxidasa, se utilizó una comparación filogeográfica, análisis de la variancia molecular, comparaciones pareadas de FST, distribuciones mismatch de diferencias de haplotipos, pruebas de neutralidad para detectar evidencias genéticas de la tropicalización y conocer mejor sus consecuencias.
Resultados
Se identificaron contracciones de rango de distribución en dos de las especies estudiadas con afinidad templada y expansión de la distribución en las tres especies con afinidad tropical. Detectamos evidencias genéticas del rango de expansión en las especies con afinidad tropical con distribuciones unimodales de las diferencias de haplotipos y valores altamente negativos para los indicadores estadísticos Fu y Li D y F*. Se encontró una subdivisión poblacional y quiebres filogeográficos en tres especies con afinidad templada, aunque la ubicación geográfica de los quiebres difirió entre las especies.
Principales Conclusiones
Las evidencias genéticas y los datos obtenidos en campo indican expansiones recientes del rango de distribución de las especies tropicales, lo que apoya la idea de una tropicalización a lo largo de la península de Baja California. En contraste, se encontraron quiebres filogeográficos en las especies con afinidad templada, lo que sugiere que la tropicalización puede causar erosión genética de los distintos linajes evolutivos con una contracción del rango de distribución. Las diferentes ubicaciones de los quiebres filogeográficos entre las especies con afinidad templada sugiere que existen algunas barreras específicas.
Mutational processes constantly shape the somatic genome, leading to immunity, aging, cancer, and other diseases. When cancer is the outcome, we are afforded a glimpse into these processes by the ...clonal expansion of the malignant cell. Here, we characterize a less explored layer of the mutational landscape of cancer: mutational asymmetries between the two DNA strands. Analyzing whole-genome sequences of 590 tumors from 14 different cancer types, we reveal widespread asymmetries across mutagenic processes, with transcriptional (“T-class”) asymmetry dominating UV-, smoking-, and liver-cancer-associated mutations and replicative (“R-class”) asymmetry dominating POLE-, APOBEC-, and MSI-associated mutations. We report a striking phenomenon of transcription-coupled damage (TCD) on the non-transcribed DNA strand and provide evidence that APOBEC mutagenesis occurs on the lagging-strand template during DNA replication. As more genomes are sequenced, studying and classifying their asymmetries will illuminate the underlying biological mechanisms of DNA damage and repair.
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•Replicative and transcriptional mutational asymmetries are widespread across cancer•APOBEC mutagenesis in humans primarily occurs on the lagging-strand template•Mismatch repair balances asymmetric replication errors•Transcription-coupled damage (TCD) introduces sense-strand mutations in liver cancer
Using an approach that distinguishes whether mutations in cancer genomes occurred on the transcribed or non-transcribed DNA strand with respect to transcription and on the leading or lagging strand with respect to replication, the predominant mutational mechanisms associated with different types of cancers and mutational patterns can be inferred.
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