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Sunday, January 9th, 2022
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| 3:45p | [Paleontology • 2022] Bryozoan-rich Stromatolites (Bryostromatolites) from the Silurian of Gotland, Sweden and their Relation to Climate-related Perturbations of the Global Carbon Cycle
ABSTRACT Bryozoan–stromatolite associations (bryostromatolites) formed conspicuous reef structures throughout the Sheinwoodian (Wenlock) to Ludfordian (Ludlow) stratigraphy on Gotland but have not been described so far. They are mainly composed of encrusting bryozoans forming a complex intergrowth with porostromate and spongiostromate microbes and are different from the abundant stromatoporoid–coral–algal reefs with respect to their composition. In the bryostromatolite different growth stages can be identified. The observed succession can be taken as evidence for cyclic environmental changes during reef formation. Stenohaline reef-dwelling organisms, such as echinoderms, sponges, corals and trilobites, indicate fully marine salinities. Ten localities exposing bryostromatolites were discovered. Individual bryostromatolites are small with few decimetres up to one metre in size, and occur solely in shallow marine areas. Common features of these reefs on Gotland are cauliflower-like growth, a high bryozoan diversity, a high abundance of phosphatic fossils and components such as bryozoan pearls and inarticulate phosphatic brachiopods, enhanced bioerosion, Palaeomicrocodium crusts, vadose silt and gypsum pseudomorphs. The high abundance of Palaeomicrocodium, as well as the alternation with other crust-forming contributors, suggest that it could have been formed directly at the palaeo-sea surface, probably in times of minor but high-frequency sea-level fluctuations. Vadose silt and pseudomorphs after gypsum in reef cavities indicate subaerial exposure shortly after reef growth. The high amount of phosphatic components indicates a high nutrient input, probably by dust. All bryostromatolites were formed in times of strongly elevated δ13C values. The unusual combination of sedimentological and palaeoecological features, as well as their occurrence exclusively during strong positive δ13C excursions, are evidence that the bryostromatolite development responded to climatic/oceanographic changes, which may have played an important role in reef control. Keywords: Palaeomicrocodium, phosphate, reef, stable carbon isotopes, subaerial exposure
  CONCLUSIONS: The conclusions of this study can be summarized as follows: • For the first time bryostromatolite reefs are described from the Silurian of Gotland. They have a cauliflower-like appearance in the field and consist mostly of porostromate and spongiostromate microbial carbonates and bryozoans. • On Gotland, bryostromatolites only occur in the Högklint and Tofta formations (Sheinwoodian) and in the Eke and Hamra formations (Ludfordian). They grew in fully marine conditions, and formed a rigid framework and a topographic relief of several decimetres up to about 1 m. • The bryostromatolites show a relatively high diversity of bryozoans (with up to twenty species in a single reef), a high abundance of reef-building and reef-dwelling organisms, and a surprisingly high abundance of phosphatic constituents. • Repeated alternations of distinct layers dominated by either porostromate microbes, spongiostromate microbial layers, or encrusting bryozoans indicate cyclic environmental changes. • Reef growth took place in extremely shallow water. The occurrence of vadose silt and gypsum pseudomorphs in reef cavities indicate subaerial exposure shortly after reef growth. • The problematicum Palaeomicrocodium indicates an extreme environment and, according to Antoskhina (2006), even subaerial exposure. The high abundance and alternation with crust-forming reef-building organisms suggest short phases of subaerial exposure even during reef growth and, therefore, reef growth in extremely shallow water. • The high abundance of phosphatic components (for example, inarticulate brachiopods, bryozoan pearls and linings) indicates a high input of phosphorous by either rivers or wind. For bryozoan pearls and linings, this hypothesis is supported by several literature studies (e.g. Oakley, 1934; Conti & Serpagli, 1988; Ma et al., 2014b). According to the studies of Kozłowski (2015) in the Baltic area, an aeolian input seems more plausible. This fits the fact that so far, no bryostromatolites have been discovered from the humid equatorial belt. • Both the bryostromatolites on Gotland and bryostromatolites in the Silurian and Ordovician of other areas occur only in times of elevated δ13C values, indicating a close link of local bryostromatolite growth and global perturbations of the carbon cycle. Anna Lene Claussen, Axel Munnecke and Andrej Ernst. 2022. Bryozoan-rich Stromatolites (bryostromatolites) from the Silurian of Gotland and their Relation to Climate-related Perturbations of the Global Carbon Cycle. Sedimentology. 69(1) Special Issue: Understanding carbonate factories through palaeoecological and sedimentological signals – Tribute to Luis Pomar; 162-198. DOI: 10.1111/sed.12863 | ||||||
| 3:58p | [Botany • 2022] Uvariopsis dicaprio (Annonaceae) • A New Tree Species with Notes on Its Pollination Biology, and the Critically Endangered narrowly endemic Plant Species of the Ebo Forest, Cameroon
Abstract Background: The Ebo Forest area is a highly threatened centre of diversity in the Littoral Region of Cameroon, globally important for conservation with many threatened species including 68 threatened species of plant, yet not formally protected. The tropical African evergreen forest tree genus Uvariopsis Engl. & Diels (Annonaceae) is characterised by unisexual, usually cauliflorous flowers with a uniseriate corolla of four petals, and two sepals. Cameroon is the centre of diversity of the genus with 14 of the 19 known species. Methods: The herbarium collection MacKinnon 51 from Ebo is hypothesized to represent a new species to science of Uvariopsis. This hypothesis is tested by the study of herbarium specimens from a number of herbaria known to hold important collections from Cameroon and surrounding countries. Results: We test the hypothesis that MacKinnon 51 represents a new species to science, using the most recent dichotomous identification key, and comparing it morphologically with reference material of all known species of the genus. We make a detailed comparative morphological study focussing on three other Cameroonian species, Uvariopsis solheidii, U. korupensis and the sympatric U. submontana. In the context of a review of the pollination biology of Uvariopsis, we speculate that in a genus otherwise with species with dull, flesh-coloured (pink, red to brown) flowers pollinated (where known) by diptera, orthoptera and blattodea (flies, crickets and cockroaches), the glossy, pale yellow-green flowers of Uvariopsis dicaprio, with additional traits unique in the genus, may be pollinated by nocturnal moths. Based on MacKinnon 51, we formally name Uvariopsis dicaprio Cheek & Gosline (Annonaceae) as new to science, and we describe, and illustrate, and map it. Restricted so far to a single site in evergreen forest in the Ebo Forest, Littoral Region, Cameroon, Uvariopsis dicaprio is provisionally assessed as Critically Endangered using the IUCN, 2012 standard because the forest habitat of this species remains unprotected, and there exist imminent threats of logging and conversion to plantations. Discussion: We show that the highest density of species of the genus (12), and of narrow endemics (5), is found in the Cross-Sanaga Interval of SE Nigeria and Western Cameroon. A revised key to the 14 Cameroonian species of Uvariopsis is presented. We review the other seven narrowly endemic and threatened species unique to the Ebo forest of Cameroon and discuss the phytogeographic affinities of the area. Conclusions: Uvariopsis dicaprio adds to the growing list of species threatened with extinction at Ebo Forest due to current anthropogenic pressures.
Uvariopsis dicaprio Cheek & Gosline sp. nov. Syn. Uvariopsis ebo nom. nud. (Gosline et al., 2021: 5). Diagnosis. Similar to Uvariopsis solheidii (De Wild.) Robyns & Ghesq., differing in the stem, petioles and abaxial midrib glabrous (versus tomentose); number of secondary nerves on each side of the midrib 5–8 (versus 8–13); petals yellow-green, (14–) 16 × (5.5–) 9 mm (versus wine brown, 7–10 × 2.5–5 mm). HABITAT. Uvariopsis dicaprio is so far only known from lower submontane forest (850 m elev.). below the elevation for the upper montane forest indicator species Podocarpus latifolius (Thunb.) R.Br. ex Mirb. The geology is ancient, highly weathered basement complex, with some ferralitic areas in foothill areas which are inland, c. 100 km from the coast. Altitude varies from c. 200 m to 1,200 m elevation. The wet season (successive months with cumulative rainfall >100 mm) falls between March and November and is colder than the dry season. Average annual rainfall at Bekob measured 2010–2016 is 2,336 mm (E. Abwe, 2018 Ebo Forest Research Programme, Cameroon, personal communication, Abwe & Morgan, 2008; Cheek et al., 2018a). ETYMOLOGY. This threatened and spectacular tree is named for the American actor and conservationist Leonardo DiCaprio, who, through several months in 2020, lobbied extensively on social media (e.g. instagram.com/p/B_0LSAhFRue; twitter.com/LeoDiCaprio/status/1257729388314943490 both accessed 12 April 2021) to draw attention to threats for the numerous rare Ebo species from the logging concession that had been announced at Ebo earlier that year. The concession was cancelled in August 2020, surely partly due to his efforts. Conclusions: Such discoveries as this new species underline the urgency for making further such discoveries while it is still possible since in all but one of the cases given above, the species have very narrow geographic ranges and/or very few individuals, and face threats to their natural habitat, putting these species at high risk of extinction. About 2,000 new species of vascular plant have been discovered each year for the last decade or more. Until species are known to science, they cannot be assessed for their conservation status and the possibility of protecting them is reduced (Cheek et al., 2020). Documented extinctions of plant species are increasing, e.g. Oxygyne triandra Schltr. and Afrothismia pachyantha Schltr. of South West Region, Cameroon are now known to be globally extinct (Cheek & Williams, 1999; Cheek et al., 2018c; Cheek, Etuge & Williams, 2019). In some cases, species appear to be extinct even before they are known to science, such as Vepris bali Cheek, also from the Cross-Sanaga interval in Cameroon (Cheek, Gosline & Onana, 2018) and elsewhere, Nepenthes maximoides Cheek (King & Cheek, 2020). Most of the 815 Cameroonian species in the Red Data Book for the plants of Cameroon are threatened with extinction due to habitat clearance or degradation, especially of forest for small-holder and plantation agriculture following logging (Onana & Cheek, 2011). Efforts are now being made to delimit the highest priority areas in Cameroon for plant conservation as Tropical Important Plant Areas (TIPAs) using the revised IPA criteria set out in Darbyshire et al. (2017). This is intended to help avoid the global extinction of additional endemic species such as Uvariopsis dicaprio which will be included in the proposed Ebo Forest IPA. With only one locality known, Uvariopsis dicaprio represents another narrowly endemic Cameroonian species threatened with extinction due to deforestation for oil palm plantations, small-scale agriculture, mining and logging, widespread threats posing extinction risks to plant species in Cameroon (Onana & Cheek, 2011; Cheek et al., 2018a). George Gosline, Martin Cheek, Jean Michel Onana, Eric Ngansop Tchatchouang, Xander M. van der Burgt, Lorna MacKinnon and Léo-Paul M. J. Dagallier. 2022. Uvariopsis dicaprio (Annonaceae) A New Tree Species with Notes on Its Pollination Biology, and the Critically Endangered narrowly endemic Plant Species of the Ebo Forest, Cameroon. PeerJ. 9:e12614. DOI: 10.7717/peerj.12614 |
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