Lobo, J. | bioRxiv Science

bioRxiv2017

Reconstructing deep-time paleoclimate legacies unveil the demise and turnover of the ancient (boreo)tropical flora

AimSince the Late Cretaceous, the Earth has gone through periods of climate change similar in scale and pace to the warming trend observed today in the Anthropocene. The impact of these ancient climatic events on the evolutionary trajectories of organisms provides clues on the organismal response to climate change, including extinction, migration or persistence. Here, we examine the evolutionary response to climate cooling/warming events of the clusioid families Calophyllaceae, Podostemaceae and Hypericaceae (CPH), and the genus Hypericum as test cases.\n\nLocationHolarctic.\n\nTime periodLate Cretaceous-Cenozoic\n\nMajor taxa studiedangiosperms\n\nMethodsWe use paleoclimate simulations, species distribution models and phylogenetic comparative approaches calibrated with fossils.\n\nResultsAncestral CPH lineages could have been distributed in the Holarctic 100 Ma, occupying tropical subhumid assemblages, a finding supported by the fossil record. Expansion to closed-canopy tropical rain forests occurred after 60 Ma, in the Cenozoic, in agreement with earlier ideas of a post-Cretaceous origin of current tropical rain forest. Cooling during this period triggered diversification declines on CPH tropical lineages, and was associated with a climatic shift towards temperate affinities in Hypericum. Hypericum subsequently migrated to tropical mountains where it encountered different temperate conditions than in the Holarctic.\n\nMain conclusionsWe hypothesize that most clusioid CPH lineages failed to adapt to temperate regimes during periods of Cenozoic climate change, and thus went extinct in the Holarctic. In contrast, boreotropical descendants including Hypericum that underwent niche evolution demonstrated selective advantages as climates became colder. Our results points toward macroevolutionary trajectories involving the altering fates of closely related clades that adapt to periods of global climate change versus those that do not. Moreover, they suggest the hypothesis that potentially many clades, particularly inhabitants of boreotropical floras, were likely extirpated from the Holarctic and persist today (if at all) in more southern tropical locations.

evolutionary biology↗

bioRxiv2017

DNA Metabarcoding For High-Throughput Monitoring Of Estuarine Macrobenthic Communities

Benthic communities are key components of aquatic ecosystems biomonitoring. However, morphology-based species identifications remain a low-throughput, and sometimes ambiguous, approach. Despite metabarcoding methodologies have been applied for above-species taxa inventories in marine meiofaunal communities, a comprehensive approach providing species-level identifications for estuarine macrobenthic communities is still lacking. Here we report a combination of experimental and field studies demonstrating the aptitude of COI metabarcoding to provide robust species-level identifications within a framework of high-throughput monitoring of estuarine macrobenthic communities. To investigate the ability to recover DNA barcodes from all species present in a bulk DNA extract, we assembled 3 phylogenetically diverse communities, using 4 different primer pairs to generate PCR products of the COI barcode region. Between 78 and 83% of the species in the tested communities were recovered through HTS. Subsequently, we compared morphology and metabarcoding-based approaches to determine the species composition from four distinct sites of an estuary. Our results indicate that the species richness would be considerably underestimated if only morphological methods were used. Although further refinement is required for improving the efficiency and output of this approach, here we show the great aptitude of COI metabarcoding to provide high quality and auditable species identifications in macrobenthos monitoring.

genetics↗