High‐resolution seismic profiles acquired in the eastern sector of Lago Fagnano, the southernmost ice‐free lake in the world, have shown the presence of very shallow gas‐bearing layers in the upper sedimentary sequences. The gas‐related features observed on seismic profiles include a typical, very strong reflection with reversed polarity, multiple reflections and acoustic blanking that hide subsurface sedimentary and structural features. The top of the acoustically high‐amplitude layer is located between 0.3–1.7 m below the lake floor. It generally forms a sharp boundary, often marked by a varying offset probably due to different levels of gas penetration, which could be related to the lithology of the overlying sediments. To confirm the presence of gas, some gravity cores were recovered in places where the blanking effect was most relevant and in the supposed gas‐free zone. Sediment core analyses have highlighted the occurrence of significant organic‐rich components within the uppermost, largely unconsolidated sedimentary layers, in correspondence of the seismically‐detected gassy zone, whereas only a few organic layers were found in the gas‐free zone. We assume that the main origin of gas is linked to the presence of a shallow, thin peat‐rich layer of Middle‐Late Holocene age. In fact, the mapped gassy zone occurs in correspondence of the outlet of the Rio Turbio, the principal tributary of Lago Fagnano, which discharges waters coming from a relatively small sag pond located immediately to the east of the eastern shore of the lake. To date, this is the first evidence of shallow gas in Tierra del Fuego lakes.
It has been argued that historical biogeography, the study of how processes that occur over long periods of time influence the distribution of life forms, is in the midst of a scientific revolution. The aim of this paper is to analyze the evolution of historical biogeography during the first decade of the 21st century and to identify major trends for the near future. We constructed a database containing all articles which dealt with historical biogeography published in the Journal of Biogeography during 1998–2010. The database included 610 contributions. Our results indicated that historical biogeography is going through a growth period. The papers analyzed were written by 2018 authors, with a mean of 3.3 authors per paper. Authors from 62 countries were involved, and most of them worked in Europe or North America. The Palearctic was the most analyzed region. Most contributions dealt with terrestrial habitats and were devoted to animal (especially Chordata) and plant taxa. Phylogeography was the most used approach (35%), followed by biota similarity and PAE (13%) and molecular biogeography (12%), with cladistic biogeography and event-based methods at 6% each. Some of the future challenges that historical biogeography faces are summarized: (1) to increase the study of taxa which are underrepresented according to the segment of biodiversity they represent; (2) to balance the amount of work devoted to different biogeographical regions; (3) to increase biogeographical knowledge of aquatic habitats; (4) to maintain the diversity of approaches, preventing the reduction of time, spatial, and taxonomic scales addressed by the discipline; and (5) to continue integrating historical biogeography along with other sources of information from other disciplines (e.g. ecology, paleontology, geology, isotope chemistry, remote sensing) into a richer context for explaining past, present, and future patterns of biodiversity on Earth.
The shortage of reliable primary taxonomic data limits the description of biological taxa and the understanding of biodiversity patterns and processes, complicating biogeographical, ecological, and evolutionary studies. This deficit creates a significant taxonomic impediment to biodiversity research and conservation planning. The taxonomic impediment and the biodiversity crisis are widely recognized, highlighting the urgent need for reliable taxonomic data. Over the past decade, numerous countries worldwide have devoted considerable effort to Target 1 of the Global Strategy for Plant Conservation (GSPC), which called for the preparation of a working list of all known plant species by 2010 and an online world Flora by 2020. Brazil is a megadiverse country, home to more of the world's known plant species than any other country. Despite that, Flora Brasiliensis, concluded in 1906, was the last comprehensive treatment of the Brazilian flora. The lack of accurate estimates of the number of species of algae, fungi, and plants occurring in Brazil contributes to the prevailing taxonomic impediment and delays progress towards the GSPC targets. Over the past 12 years, a legion of taxonomists motivated to meet Target 1 of the GSPC, worked together to gather and integrate knowledge on the algal, plant, and fungal diversity of Brazil. Overall, a team of about 980 taxonomists joined efforts in a highly collaborative project that used cybertaxonomy to prepare an updated Flora of Brazil, showing the power of scientific collaboration to reach ambitious goals. This paper presents an overview of the Brazilian Flora 2020 and provides taxonomic and spatial updates on the algae, fungi, and plants found in one of the world's most biodiverse countries. We further identify collection gaps and summarize future goals that extend beyond 2020. Our results show that Brazil is home to 46,975 native species of algae, fungi, and plants, of which 19,669 are endemic to the country. The data compiled to date suggests that the Atlantic Rainforest might be the most diverse Brazilian domain for all plant groups except gymnosperms, which are most diverse in the Amazon. However, scientific knowledge of Brazilian diversity is still unequally distributed, with the Atlantic Rainforest and the Cerrado being the most intensively sampled and studied biomes in the country. In times of “scientific reductionism”, with botanical and mycological sciences suffering pervasive depreciation in recent decades, the first online Flora of Brazil 2020 significantly enhanced the quality and quantity of taxonomic data available for algae, fungi, and plants from Brazil. This project also made all the information freely available online, providing a firm foundation for future research and for the management, conservation, and sustainable use of the Brazilian funga and flora.
Stevia Cav. (Asteraceae, Eupatorieae) includes ca. 235 species distributed from United States of America to Chile and Argentina in South America. During the taxonomic revision of the Argentinian species several specimens belonging to Stevia mandonii Sch. Bip. were found in the province of Jujuy, where it had not been previously cited. In this framework, the goals of the present article are 1) to report the species in Argentina for the first time, 2) to differentiate it among morphologically close species, and 3) to perform a taxonomical analysis based on herbarium specimens, populations in the field, bibliography and type material. Morphology was analyzed by means of optical microscopy and scanning electron microscopy techniques. Stevia mandonii is readily distinguished by its small size of 10-20 cm, rounded leaves and pappus formed by 9-17 bristles with presence of heterocarpy. A detailed morphological description, an illustration, a geographic distribution map, and a key to species of Stevia that occur in Jujuy are provided. The designation of a lectotype for the name Stevia mandonii is properly discussed.
A revision and a morphological analysis of the Uruguayan species of Stevia (Compositae, Eupatorieae) were performed. Leaf, inflorescence, pubescence and pappus traits were identified as key to separate species. Stevia entreriensis, S. entreriensis var. minor, and Dissothrix hassleriana were considered synonyms of S. hirsuta, and S. ophryodonta and S. oxylaena synonyms of S. veronicae. Lectotypes for the names Stevia cinerascens, S. megapotamica, S. linariifolia, S. selloi, S. selloi var. yparacayensis, S. oxylaena and S. veronicae were designated. Stevia burkartii was excluded from the Uruguayan flora. As a result, 10 Uruguayan species are considered: S. aristata, S. cinerascens, S. congesta, S. gratioloides, S. hirsuta, S. multiaristata, S. sabulonis, S. satureiifolia, S. selloi, and S. veronicae. A key to the Uruguayan species, descriptions, photographs and distribution maps are provided.
The elaboration of a comprehensive database about the distribution of the South American genus Nassauvia has allowed investigate its conservation biogeography. The combined use of historical (Dispersal Vicariance Analysis) and ecological (UPGMA) biogeographical approaches has led to detecting past, present and future critical areas in the evolution and persistence of the genus. According to the size of distribution areas, number of locations, environmental niche models, and predicted shifts of these spatial characteristics following the Intergovernmental Panel on Climate Change forecasts for the next decade, it has been possible to award the level of global and national risk for all species of the genus and assign their corresponding IUCN categories. Severe gaps in legal and in situ conservation policies have been detected within the region, making it urgent the adoption of measures aimed at preventing the extinction of the most endangered species. We identify a future dramatic loss of Nassauvia species in the Andes and conversely a species increase in Patagonia. Patagonia has emerged as the cradle of the genus and could be its refuge in the future according the predictions targeted by climate change. Communicated by Daniel Sanchez Mata. This article belongs to the Topical Collection: Biodiversity Conservation and Reserves.
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