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1.
Nature ; 573(7773): 256-260, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31477908

RESUMO

Mediterranean climates are characterized by strong seasonal contrasts between dry summers and wet winters. Changes in winter rainfall are critical for regional socioeconomic development, but are difficult to simulate accurately1 and reconstruct on Quaternary timescales. This is partly because regional hydroclimate records that cover multiple glacial-interglacial cycles2,3 with different orbital geometries, global ice volume and atmospheric greenhouse gas concentrations are scarce. Moreover, the underlying mechanisms of change and their persistence remain unexplored. Here we show that, over the past 1.36 million years, wet winters in the northcentral Mediterranean tend to occur with high contrasts in local, seasonal insolation and a vigorous African summer monsoon. Our proxy time series from Lake Ohrid on the Balkan Peninsula, together with a 784,000-year transient climate model hindcast, suggest that increased sea surface temperatures amplify local cyclone development and refuel North Atlantic low-pressure systems that enter the Mediterranean during phases of low continental ice volume and high concentrations of atmospheric greenhouse gases. A comparison with modern reanalysis data shows that current drivers of the amount of rainfall in the Mediterranean share some similarities to those that drive the reconstructed increases in precipitation. Our data cover multiple insolation maxima and are therefore an important benchmark for testing climate model performance.


Assuntos
Clima , Chuva , Estações do Ano , África , Região do Mediterrâneo , Modelos Teóricos
2.
J Evol Biol ; 31(12): 1969-1975, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30113099

RESUMO

Due to the ubiquity and high dispersal capacity of unicellular eukaryotes, their often extraordinary diversity found in isolated and long-lived ecosystems such as ancient lakes is typically attributed to multiple colonization events rather than to in situ speciation. However, respective evolutionary studies are very scarce and the often high number of species flocks in ancient lakes across multicellular taxa raises the question whether unicellular species, such as diatoms, may radiate as well. Here, we use an integrative approach that includes molecular data from benthic diatom species of the genus Aneumastus endemic to ancient Lake Ohrid, fossil data obtained from the sediment record of a recent deep-drilling project and biogeographical information to test if this group, indeed, constitutes a species flock. Molecular-clock and phylogenetic analyses indicate a young monophyletic group of several endemic species. Molecular, fossil and biogeographical data strongly suggest a rapid intralacustrine diversification, which was possibly triggered by the emergence of novel habitats. This finding is the first evidence for a species flock in diatoms and suggests that in situ speciation is also a relevant evolutionary process for unicellular eukaryotes in isolated ecosystems.


Assuntos
Diatomáceas/genética , Diatomáceas/fisiologia , Evolução Molecular , Água Doce , Variação Genética , Filogenia , Fósseis , Fatores de Tempo
3.
Sci Total Environ ; 829: 154536, 2022 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-35304150

RESUMO

Karst ecosystems play a unique role as exceptional natural habitats in sustaining biodiversity. This study focuses on diatoms, a diverse group of microeukaryotes in the periphytic community of a karstic river. In a multi-microhabitat study along the Krka River (Croatia), our goal was to obtain a detailed overview of diatom diversity and community structure using morphological and molecular approaches, and to assess the applicability of eDNA metabarcoding as a reliable tool for biomonitoring assessment. The results revealed a relatively low agreement in the diatom community composition between the two approaches, but also provided complementary information, with no differences in beta diversity detected between microhabitats. The SIMPER analysis underlined the importance of the molecular approach in identifying diatom community composition, due to errors in distinguishing between deposited diatom cells that occurred in the morphological analysis. In contrast, the morphological approach indicated a clear diatom community separation along the river with a strong location effect. Despite certain differences, both approaches provided a feasible assessment of the ecological status according to the relationship to environmental pressures, classifying the Krka River as High (morphological approach) or Good (molecular approach) throughout the most of its course. Moreover, diatom diversity based on both approaches provides a reliable dataset applicable in routine monitoring assessment and offers a deeper understanding of the presented ecological status. The incompleteness of a reference database presents one major drawback of the molecular approach, which needs further updating in order to improve routine diatom metabarcoding.


Assuntos
DNA Ambiental , Diatomáceas , Biodiversidade , Código de Barras de DNA Taxonômico , Diatomáceas/genética , Ecossistema , Monitoramento Ambiental/métodos , Rios
4.
Sci Adv ; 6(40)2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32998898

RESUMO

The scarcity of high-resolution empirical data directly tracking diversity over time limits our understanding of speciation and extinction dynamics and the drivers of rate changes. Here, we analyze a continuous species-level fossil record of endemic diatoms from ancient Lake Ohrid, along with environmental and climate indicator time series since lake formation 1.36 million years (Ma) ago. We show that speciation and extinction rates nearly simultaneously decreased in the environmentally dynamic phase after ecosystem formation and stabilized after deep-water conditions established in Lake Ohrid. As the lake deepens, we also see a switch in the macroevolutionary trade-off, resulting in a transition from a volatile assemblage of short-lived endemic species to a stable community of long-lived species. Our results emphasize the importance of the interplay between environmental/climate change, ecosystem stability, and environmental limits to diversity for diversification processes. The study also provides a new understanding of evolutionary dynamics in long-lived ecosystems.


Assuntos
Evolução Biológica , Ecossistema , Biodiversidade , Mudança Climática , Fósseis , Lagos
5.
Forensic Sci Int ; 127(3): 198-203, 2002 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-12175949

RESUMO

Results obtained by examination of 22 human cases suspected for drowning, one human case of death other than drowning and several tests on laboratory rats were used as a basis for evaluation of diatom method as supportive in forensic expertise of drowning. The recovery of diatoms from various examined organs, their qualitative and quantitative composition, if properly treated without the possibility of contamination, can be a reliable proof of the time and place of drowning. The priority of organ examination (external microflora determination, lungs, brain, heart (and/or blood), stomach, liver and kidney, and finally bone marrow) is discussed and established as well as the basic future research on cases suspected of drowning, but also on non-drowned victims and laboratory animals.


Assuntos
Diatomáceas/isolamento & purificação , Afogamento/diagnóstico , Medicina Legal/métodos , Animais , Autopsia , Medula Óssea/microbiologia , Encéfalo/microbiologia , Causas de Morte , Afogamento/microbiologia , Afogamento/mortalidade , Esôfago/microbiologia , Cabelo/microbiologia , Coração/microbiologia , Humanos , Rim/microbiologia , Fígado/microbiologia , Pulmão/microbiologia , Ratos , Pele/microbiologia , Estômago/microbiologia , Distribuição Tecidual , Microbiologia da Água
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