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(a) Map showing the location of Mauritius in the Indian Ocean. (b) Map of the island indicating the approximate coastline during the 'Last Glacial Maximum' (−115 m), altitude lines (200-m steps), the distribution of main vegetation types before colonization (adapted from Cheke and Hume, 2008), and the extent of palm woodland according to our results (this paper). Lower montane forest includes mid-altitude forest, moist forest, wet forest, and upland vegetation types (e.g. heath). Coastal forest, mangroves, and wetlands are not shown. White dots indicate study areas discussed in the text: 1 De Boer et al. (2014), 2 Van der Plas et al. (2012), 3 De Boer et al. (2013b), 4 De Boer et al. (2013a). (c) Map of southeast Mauritius and the location of Mare aux Songes (MAS).
Source publication
Analyses of pollen, diatoms, XRF geochemistry, and pigments provide a unique window into how an insular ecosystem in Mauritius responded to an extreme drought event 4200 years ago. We provide a reconstruction of regional vegetation change and local wetland development under influence of sea level rise and inferred climate change between 4400 and 41...
Contexts in source publication
Context 1
... is a volcanic island located ~900 km east of Madagas- car in the SW Indian Ocean (Figure 1). The island has a surface of 1865 km 2 , with several peaks reaching up to 828-m elevation and a central flat upland area between 500-and 650-m elevation that slopes gently toward the lowlands at the northern and eastern coastlines. ...
Context 2
... presence of spores of Sporormiella and other coprophilous fungi indicates that these larger vertebrates were visiting the rock valley, as these spores have a limited dispersal distance (Wood et al., 2011). Stagnant freshwater is rare in this part of the low- lands because of rocky basaltic soils with poor water retention capacity and high evaporation rates ( Rijsdijk et al., 2009; Figure 1c). The dominance of F. brevistriata also indicates that water levels were relatively high and were relatively rich in suspended organic matter. ...
Context 3
... Tatos rock valley in the eastern Mauritian lowlands (Fig- ure 1b), which records a dynamic environmental history during the last 8000 years, shows an unstable climatic period between approximately 4500 and 4000 cal. yr BP, during which decadal to centennial droughts alternate with decadal wet pulses (De Boer et al., 2014). ...
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An array of infections, including the novel coronavirus (SARS-CoV-2), trigger macrophage activation syndrome (MAS) and subsequently hypercytokinemia , commonly referred to as a cytokine storm (CS). It is postulated that CS is mainly responsible for critical COVID-19 cases, including acute respiratory distress syndrome (ARDS). Recognizing the therap...
Citations
... Reunion, a younger island (2 my) is in the erosion and landslide phase and has a very rugged landscape, reaching an elevation of 3071 m, while Mauritius, an older island (8 my) in the late basal plain phase, has experienced the long-term effects of erosion and culminates at just 828 m (Duncan, 2009). Global climatic events, including Late Quaternary events, appear to have affected species' demographic histories on both islands (de Boer et al., 2015;Garot et al., 2019;Heller et al., 2008;Salmona et al., 2012;Salmona, Heller, Quéméré, et al., 2017). However, the intensity of ecological disruption as experienced by animal and plant populations may have been very different on the two islands since the persistence of possible refugia during extreme cooling events is positively related to mountainous topography (Harter et al., 2015;Mastretta-Yanes et al., 2015; but see Salces-Castellano et al., 2021). ...
Disentangling the effects of ecological disruptions operating at different spatial and temporal scales in shaping past species' demography is particularly important in the current context of rapid environmental changes driven by both local and regional factors. We argue that volcanic oceanic islands provide useful settings to study the influence of past ecological disruptions operating at local and regional scales on population demographic histories. We investigate potential drivers of past population dynamics for three closely related species of passerine birds from two volcanic oceanic islands, Reunion and Mauritius (Mascarene archipelago), with distinct volcanic history. Using ABC and PSMC inferences from complete genomes, we reconstructed the demographic history of the Reunion Grey White‐eye ( Zosterops borbonicus (Pennant, 1781)), the Reunion Olive White‐eye ( Z. olivaceus (Linnaeus, 1766)) and the Mauritius Grey White‐eye ( Z. mauritianus (Gmelin, 1789)) and searched for possible causes underlying similarities or differences between species living on the same or different islands. Both demographic inferences strongly support ancient and long‐term expansions in all species. They also reveal different trajectories between species inhabiting different islands, but consistent demographic trajectories in species or populations from the same island. Species from Reunion appear to have experienced synchronous reductions in population size during the Last Glacial Maximum, a trend not seen in the Mauritian species. Overall, this study suggests that local events may have played a role in shaping population trajectories of these island species. It also highlights the potential of our conceptual framework to disentangle the effects of local and regional drivers on past species' demography and long‐term population processes.
... All fossil remains of N. mauritianus were collected at the Mare aux Songes, a marsh situated in a lowland, coastal region of southeast Mauritius. This was originally a lake surrounded by tall canopy wet forest interspersed with more open dry, palm and Pandanus-rich vegetation (de Boer et al., 2015), and this may have been the preferred habitat. It formed large flocks, at least when flying, and may have undertaken intra-island migrations to feeding grounds or breeding sites, as did the extinct Mauritian sheldgoose Alopochen mauritiana (Newton and Gadow, 1893) (Leguat, 1708;Hume and Winters, 2016). ...
Night herons of the genus Nycticorax and Nyctanassa are adept island colonisers, occurring on a number of oceanic islands and island archipelagos. Continental species and those inhabiting large islands are generally not considered threatened, whereas night herons restricted to small, oceanic islands are particularly
vulnerable to human interference. As a result, six out of nine described species and one subspecies, all derived from Nycticorax nycticorax, Nycticorax caledonicus or Nyctanassa violacea, are now extinct whereas a further three extinct species await description. The extinct island endemics generally exhibit morphological adaptations to an insular environment and diet, such as an increase or decrease in size, robust jaws and legs, and smaller wings with associated reduced flying ability than founding stock. Here I present an osteological comparison along with historical descriptions of the extinct, oceanic island night herons, with special reference to the Mascarene and Ascension fossil species, and Bonin Island subspecies, and show the degree of morphological changes between the founding and island taxa. I further discuss the reasons why they became extinct.
... Many of these tree species reach enormous heights -abbott's booby on Christmas Island typically nests in trees from 10 -40 m above the ground (Nelson 1971(Nelson , 1978Boland et al. 2012) -so the MaS and surrounding area would have provided an abundant supply of tall trees for nesting. On Christmas Island, abbott's booby prefers Eugenia (Myrtaceae), Tristiropsis (Sapindaceae), Ficus (Moraceae) and Planchonella (Sapotaceae) for nest sites (Nelson & Powell 1986;Nelson 2006), which are tree families well represented in the MaS fossil deposit, as well as occurring elsewhere on Mauritius (de Boer et al. 2013(de Boer et al. , 2015. No native predators on Mauritius were large enough to hunt adult Mascarene booby, but an extirpated Mauritius population of Réunion Harrier Circus maillardi J. Verreaux, 1862 could have tackled chicks, as reported for the similar-sized Christmas Island Goshawk Accipiter fasciatus natalis (lister, 1889) (Hennicke 2012b). ...
a new subspecies of Papasula booby is described from fossil remains collected in the Mascarene Islands of Mauritius and Rodrigues, southwestern Indian Ocean. The Mascarene Booby Papasula abbotti nelsoni ssp. nov., larger than nominate abbott's Booby P. a. abbotti from Christmas Island, northeast Indian Ocean, was approximately the same size as the extinct Hiva Oa Booby P. a. costelloi from the Marquesas in the Eastern Pacific. Mentioned in early accounts of Mauritius in 1668 and in 1725-26 and 1761 on Rodrigues, the Mascarene booby became extinct by the end of the 18th century. Members of another isolated but now extirpated population of Papasula abbotti from assumption Island in the Seychelles archipelago, the island from which the type specimen was collected, are identical to extant Christmas Island birds in size and colouration and discussed in detail herein.
... This scenario appears attractive at first glance, since it exerts particular events for the origin of a unique thanatocoenosis. Deadly cocktails produced by cyanobacteria can kill a substantial amount of animals in short amounts of time (de Boer et al. 2015;Bengis et al. 2016). However, there is additional evidence challenging the "poison scenario" at Neumark. ...
The high-resolution palaeoenvironmental record from the last interglacial (Eemian) lakeland at NeumarkNord (Saxony-Anhalt, Germany) holds the rare potential to study Neanderthal subsistence ca.125,000 years ago in remarkable detail. Using the palynological record from the large lake Neumark-Nord 1 (NN1) and the adjacent small “pool” Neumark-Nord 2 (NN2) a sequence of lithic and faunal assemblages has been established, indicating Neanderthal presence in the lakeland throughout the Eemian. Calculations of the herbivore carrying capacity for the Neumark area during the Eemian reveal high biomass estimates. Using these estimates it was possible to calculate the structure of the source population, based on the faunal record rich in species and individuals, from littoral deposits assigned to the frst mesocratic phase of the Eemian. The results can be used as a frame of reference for making inferences on subsistence opportunities and prey selection based on taphonomical and zooarchaeological studies of the Neumark-Nord faunal assemblages. In a broader perspective our study demonstrates the benefts from inferring energy values (kcal) and body mass (kg) as ancillary parameters to zooarchaeological analyses to understand the relationships between death assemblage and their habitats from which they originate.
... This scenario appears attractive at first glance, since it exerts particular events for the origin of a unique thanatocoenosis. Deadly cocktails produced by cyanobacteria can kill a substantial amount of animals in short amounts of time (de Boer et al. 2015;Bengis et al. 2016). However, there is additional evidence challenging the "poison scenario" at Neumark. ...
The high-resolution palaeoenvironmental record from the last interglacial (Eemian) lakeland at Neumark-Nord (Saxony-Anhalt, Germany) holds the rare potential to study Neanderthal subsistence ca. 125,000 years ago in remarkable detail. Using the palynological record from the large lake Neumark-Nord 1 (NN1) and the adjacent small "pool" Neumark-Nord 2 (NN2) a sequence of lithic and faunal assemblages has been established , indicating Neanderthal presence in the lakeland throughout the Eemian. Calculations of the herbi-vore carrying capacity for the Neumark area during the Eemian reveal high biomass estimates. Using these estimates it was possible to calculate the structure of the source population, based on the faunal record rich in species and individuals, from littoral deposits assigned to the first mesocratic phase of the Eemian. The results can be used as a frame of reference for making inferences on subsistence opportunities and prey selection based on taphonomical and zooarchaeological studies of the Neumark-Nord faunal assemblages. In a broader perspective our study demonstrates the benefits from inferring energy values (kcal) and body mass (kg) as ancillary parameters to zooarchaeological analyses to understand the relationships between death assemblage and their habitats from which they originate.
... A lower RSL is recorded in Makoba Bay from ∼4400 cal yr BP, as indicated by the change in mangrove composition from lower to middle intertidal mangroves in BMAK-1 until ∼3200 cal yr BP. This period coincides with a regionally arid phase recorded across East Africa commencing around 4500-4100 cal yr BP (Hassan, 1997;Bonnefille and Chalie, 2000;Thompson et al., 2002;Marchant and Hooghiemstra, 2004;Kiage and Liu, 2006;Rijsdijk et al., 2011;de Boer et al., 2015). After 3200 cal yr BP, and prior to 2900 cal yr BP, a RSL rise occurred indicative of a change from middle to lower intertidal mangroves. ...
There is continued uncertainty regarding the rate, timing, duration and direction of Holocene sea-level for the Indian Ocean, and indeed the wider tropical realm. We present the first synthesis, and a new chronology, for Holocene relative sea-level (RSL) using a range sediment cores retrieved from mangrove ecosystems in three locations along coastal Tanzania. This study applies the relationship of ratios between the key mangrove taxa of Sonneratia:(Bruguiera/Ceriops) (S/BC) (ranging from 0 – 22.9) and Sonneratia:Rhizophora (S/R) (ranging from 0 – 2.29), vegetation and altitude to interpret mangrove dynamics and refine the vertical errors associated with relative sea level change. The variations in mangrove taxa ratios in the sediment cores obtained from each site shows mangrove development at different periods during the Holocene from around 7900 cal yr BP. An early to mid-Holocene RSL rise occurred from ∼7900 to ∼4600 cal yr BP that may have reached a higher level than present. A lower RSL occurred after 4600 cal yr BP, resulting in mangroves retreating seaward at all three study locations, before a low magnitude RSL rise occurred between 4400 and 2000 cal yr BP. Another RSL rise is recorded at ∼500 cal yr BP before falling to a level lower than present at ∼100 cal yr BP. There is evidence of a recent RSL rise recorded from mangrove ratios during the last century. In addition, the sedimentation rates among sites are relatively different due to different altitudinal ranges with freshwater input, sediment supply and progradation having significantly more effect in the Rufiji Delta (2.1–10.9 mm cal yr−1) than at the Zanzibar sites (0.3–6.6 mm cal yr−1).
... Prehistoric mass mortalities involving deer, horses, elephants, aurochs and cave lions in Pleistocene and eocene lakes have been attributed to toxic cyanobacteria 176,177 . A severe drought ~4,000 years ago led to dense cyanobacterial blooms in wetlands on the island of mauritius, coinciding with mass mortalities of thousands of dodos and giant turtles 178 . ...
Cyanobacteria can form dense and sometimes toxic blooms in freshwater and marine environments, which threaten ecosystem functioning and degrade water quality for recreation, drinking water, fisheries and human health. Here, we review evidence indicating that cyanobacterial blooms are increasing in frequency, magnitude and duration globally. We highlight species traits and environmental conditions that enable cyanobacteria to thrive and explain why eutrophication and climate change catalyse the global expansion of cyanobacterial blooms. Finally, we discuss management strategies, including nutrient load reductions, changes in hydrodynamics and chemical and biological controls, that can help to prevent or mitigate the proliferation of cyanobacterial blooms.
... Earth-Science Reviews 178 (2018) 322-378 between 4100 and 4300 yr BP. A major drying event around 4200 yr BP has been widely detected and dated, and linked to a series of droughts that were responsible for events such as mass extinctions on Mauritius (de Boer et al., 2015). Archaeologically, during this period we see an expansion of pastoralist activity (Coughenour and Ellis, 1993). ...
... However, there is a significant caveat to assessing the impact that severe drought events may have as the palaeoenvironmental and archaeological records may not be well enough resolved (in terms of chronology and sampling) to detect these short-term, but intense, events. Where it has been possible to examine the impact of this, it has been within a closed island system and with animals who are not able to escape those conditions (e.g., de Boer et al., 2015), whereas people will arguably move to new areas. Whilst we may be seeing this with the expansion of pastoralism in East Africa at this time, as pastoral populations expanded farther southwards from an increasingly dry Sahara, finding the direct chronological and environmental link between people and the climatic events is still elusive. ...
... For example, palaeoecological studies from Mauritius show that the now extinct dodo and two species of giant tortoise lived in dense populations in the coastal lowlands 75 . These populations experienced regular environmental hazards from tropical storms and seasonal droughts 76 . A prolonged drought 4,200 years ago caused a mass death in the Mare aux Songes 76 . ...
The discovery and colonisation of islands by humans has invariably resulted in their widespread ecological transformation. The small and isolated populations of many island taxa, and their evolution in the absence of humans and their introduced taxa, mean that they are particularly vulnerable to human activities. Consequently, even the most degraded islands are a focus for restoration, eradication, and monitoring programmes to protect the remaining endemic and/or relict populations. Here, we build a framework that incorporates an assessment of the degree of change from multiple baseline reference periods using long-term ecological data. The use of multiple reference points may provide information on both the variability of natural systems and responses to successive waves of cultural transformation of island ecosystems, involving, for example, the alteration of fire and grazing regimes and the introduction of non-native species. We provide exemplification of how such approaches can provide valuable information for biodiversity conservation managers of island ecosystems.
... Excess of nutrients was therefore an exception rather than a rule, although historical cases of local eutrophication exist. For instance, in Mauritius a severe drought around 4200 years before present triggered a drastic change in nutrient flows (De Boer et al., 2015). Driven by thirst, large vertebrates including giant tortoises and dodos migrated massively to the only freshwater source left. ...
... While drinking the last bits of water, these animals dropped their excrements causing toxic hypertrophic conditions in which cyanobacterial blooms prevailed. Finally, these toxic conditions became fatal to the large vertebrates leading to a mass extinction close to the water source, which triggered an even higher nutrient load from the animal remains (De Boer et al., 2015). More of these early eutrophication cases took place; however, these occurred at a much smaller scale than today. ...
