Sea level and faunal change during the late Wenlock and earliest Ludlow (Silurian): A point of view from the Algerian Sahara

A late Wenlock transgression (C. rigidus zone) affecting a large area of the Algerian Sahara has been known for the last thirty years; in this case there is no break at the Wenlock‐Ludlow boundary and the sedimentation is continuous to the earliest Ludlow. But in many other areas of Sahara a late Wenlock regression is observed. This regression may or may not be followed by a latest Wenlock or an early Ludlow transgression. A sedimentary model is proposed in despite of several problems. In order to compare what happens in each region a schematic diagram is used showing the tendencies to shallowing and deepening. Differences observed between the North Sahara basin and the other parts of the Algerian Sahara and comparison between local sea‐level curves and the global sea‐level curve proposed by Johnson et al. (1991) lead to reconsider the evidence of an eustatic early Ludlow event. To end the problem of the disappearance of nearly all graptolites at the end of Wenlock is discussed. The influence of land emergence in the evolution of marine fossil groups in the disturbance that it can bring to the development of the microplankton and the chemistry of the sea seems to have been too neglected.     

Pattern of some Silurian bioevents

The best‐known Silurian bioevent occurred at the end of the Wenlock: the lundgreni event, together with the nassa‐ludensis crisis, was established among planktic graptolites. The East Baltic data show several peaks of high diversity (especially triangulatus, turriculatus, scanicus zones) and three levels of low diversity of graptolites (antennularius, radians, ludensis zones). These are more or less coincident with sea‐level changes. Energetic innovation of the shallow shelf corals started in the early Silurian. The late Wenlock regression seems not to affect them seriously but the late Silurian decline coincides with the aridization of the climate and a regression of the shelf seas. The Agnatha had strong radiations in the Wenlock (ludensis Zone) and Ludlow (leintwardinensis Zone), the fishes in the Pridoli. Many Silurian vertebrates were long‐ranging and extinction rate was relatively low; only at the late leintwardinensis level and in the latest Ludlow did considerable extinctions occur.     

Devonian conodont biogeography: Quantitative analysis of provinciality

Cluster analysis of conodont faunas from each of 17 Lower‐lower Upper Devonian zones and subzones (data as reported by Klapper and Johnson, 1980) reveal changing patterns of provinciality.

Provinciality, expressed by a differentiation into western Laurussian and proto‐Tethyan biogeographic regions, is moderate in the lower Lochkovian but is low or absent in the upper Lochkovian‐lower Pragian. Provincialism returns in the Pragian and reaches its maximum development during the Emsian. Most Australian faunas are distinct from those of western Laurussia and the proto‐Tethys. Conodont faunas from suspect terranes of western North America display no unusual biogeographic affinities. Provincialism declines during the Eifelian and is only weakly developed in Givetian‐lower Frasnian faunas.

Changing global sea level during the Devonian may explain the development of Devonian conodont provinciality. As proposed by Klapper and Johnson (1980), low provinciality is associated with low stands of sea level. Endemic faunas develop in isolated epeiric seas during intermediate stages of sea level rise. High stands of sea level ultimately drown barriers to faunal exchange and prompt a return to low provinciality conditions.     

Biotic and environmental dynamics through the Late Jurassic–Early Cretaceous transition: evidence for protracted faunal and ecological turnover

The Late Jurassic to Early Cretaceous interval represents a time of environmental upheaval and cataclysmic events, combined with disruptions to terrestrial and marine ecosystems. Historically, the Jurassic/Cretaceous (J/K) boundary was classified as one of eight mass extinctions. However, more recent research has largely overturned this view, revealing a much more complex pattern of biotic and abiotic dynamics than has previously been appreciated. Here, we present a synthesis of our current knowledge of Late Jurassic–Early Cretaceous events, focusing particularly on events closest to the J/K boundary. We find evidence for a combination of short‐term catastrophic events, large‐scale tectonic processes and environmental perturbations, and major clade interactions that led to a seemingly dramatic faunal and ecological turnover in both the marine and terrestrial realms. This is coupled with a great reduction in global biodiversity which might in part be explained by poor sampling. Very few groups appear to have been entirely resilient to this J/K boundary ‘event’, which hints at a ‘cascade model’ of ecosystem changes driving faunal dynamics. Within terrestrial ecosystems, larger, more‐specialised organisms, such as saurischian dinosaurs, appear to have suffered the most. Medium‐sized tetanuran theropods declined, and were replaced by larger‐bodied groups, and basal eusauropods were replaced by neosauropod faunas. The ascent of paravian theropods is emphasised by escalated competition with contemporary pterosaur groups, culminating in the explosive radiation of birds, although the timing of this is obfuscated by biases in sampling. Smaller, more ecologically diverse terrestrial non‐archosaurs, such as lissamphibians and mammaliaforms, were comparatively resilient to extinctions, instead documenting the origination of many extant groups around the J/K boundary. In the marine realm, extinctions were focused on low‐latitude, shallow marine shelf‐dwelling faunas, corresponding to a significant eustatic sea‐level fall in the latest Jurassic. More mobile and ecologically plastic marine groups, such as ichthyosaurs, survived the boundary relatively unscathed. High rates of extinction and turnover in other macropredaceous marine groups, including plesiosaurs, are accompanied by the origin of most major lineages of extant sharks. Groups which occupied both marine and terrestrial ecosystems, including crocodylomorphs, document a selective extinction in shallow marine forms, whereas turtles appear to have diversified. These patterns suggest that different extinction selectivity and ecological processes were operating between marine and terrestrial ecosystems, which were ultimately important in determining the fates of many key groups, as well as the origins of many major extant lineages. We identify a series of potential abiotic candidates for driving these patterns, including multiple bolide impacts, several episodes of flood basalt eruptions, dramatic climate change, and major disruptions to oceanic systems. The J/K transition therefore, although not a mass extinction, represents an important transitional period in the co‐evolutionary history of life on Earth.     

Silurian (Wenlock–ludlow) Graptolites from Bolivia

Well preserved middle to upper Silurian (Wenlock–Ludlow) graptolites from Bolivia are described for the first time. Generally monospecific graptolite faunas, of species largely endemic to South America, are found in a few levels in the lower part of the Kirusillas, Rio Carrasco and Uncía formations. The oldest identified level yields specimens of Pristiograptus praedeubeli (Jaeger) and is referred to the upper Wenlock. Younger faunas belong to the Ludlow and include Saetograptus , Monograptus and Neodiversograptus specimens. These may be referred to the Gorstian (lower Ludlow). The fauna includes Saetograptus argentinus robustus ssp. nov. and Monograptus bolivianus sp. nov.     

The extinction of the dinosaurs

Non‐avian dinosaurs went extinct 66 million years ago, geologically coincident with the impact of a large bolide (comet or asteroid) during an interval of massive volcanic eruptions and changes in temperature and sea level. There has long been fervent debate about how these events affected dinosaurs. We review a wealth of new data accumulated over the past two decades, provide updated and novel analyses of long‐term dinosaur diversity trends during the latest Cretaceous, and discuss an emerging consensus on the extinction's tempo and causes. Little support exists for a global, long‐term decline across non‐avian dinosaur diversity prior to their extinction at the end of the Cretaceous. However, restructuring of latest Cretaceous dinosaur faunas in North America led to reduced diversity of large‐bodied herbivores, perhaps making communities more susceptible to cascading extinctions. The abruptness of the dinosaur extinction suggests a key role for the bolide impact, although the coarseness of the fossil record makes testing the effects of Deccan volcanism difficult.     

Extremely low genetic diversity across mangrove taxa reflects past sea level changes and hints at poor future responses

The projected increases in sea levels are expected to affect coastal ecosystems. Tropical communities, anchored by mangrove trees and having experienced frequent past sea level changes, appear to be vibrant at present. However, any optimism about the resilience of these ecosystems is premature because the impact of past climate events may not be reflected in the current abundance. To assess the impact of historical sea level changes, we conducted an extensive genetic diversity survey on the Indo‐Malayan coast, a hotspot with a large global mangrove distribution. A survey of 26 populations in six species reveals extremely low genome‐wide nucleotide diversity and hence very small effective population sizes (N_e) in all populations. Whole‐genome sequencing of three mangrove species further shows the decline in N_e to be strongly associated with the speed of past changes in sea level. We also used a recent series of flooding events in Yalong Bay, southern China, to test the robustness of mangroves to sea level changes in relation to their genetic diversity. The events resulted in the death of half of the mangrove trees in this area. Significantly, less genetically diverse mangrove species suffered much greater destruction. The dieback was accompanied by a drastic reduction in local invertebrate biodiversity. We thus predict that tropical coastal communities will be seriously endangered as the global sea level rises. Well‐planned coastal development near mangrove forests will be essential to avert this crisis.     

Late Devonian global ostracod palaeobiogeography

A global Late Devonian ostracod database is constructed, incorporating new materials from South China and Northwest China. Four palaeobiogeographical units (Cathaysia, North America, Europe and peri‐Gondwana) are recognized during the Frasnian and five palaeobiogeographical units (Cathaysia, North America, Europe, Siberia and Australia) in the Famennian. Three controlling factors (climatic zonation, geographical isolation and global sea‐level changes) are identified to have played roles in shaping the palaeogeographical regionalization of ostracod faunas in the Late Devonian. The ostracod palaeobiogeography in the Frasnian was mainly influenced by climatic zonation, while rapid changes in tectonic configuration in the Famennian drastically altered the global palaeobiogeography of ostracods. The palaeobiogeographical regionalization of ostracod faunas suggests that Laurussia and Gondwana continued to draw near during the Late Devonian, with the first collision occurring in Southern Central Europe in the Famennian. The South China plate drifted northward to the Kazakhstan plate away from the Australian plate, which gradually became isolated during the Famennian Stage.     

High‐resolution tide projections reveal extinction threshold in response to sea‐level rise

Sea‐level rise will affect coastal species worldwide, but models that aim to predict these effects are typically based on simple measures of sea level that do not capture its inherent complexity, especially variation over timescales shorter than 1 year. Coastal species might be most affected, however, by floods that exceed a critical threshold. The frequency and duration of such floods may be more important to population dynamics than mean measures of sea level. In particular, the potential for changes in the frequency and duration of flooding events to result in nonlinear population responses or biological thresholds merits further research, but may require that models incorporate greater resolution in sea level than is typically used. We created population simulations for a threatened songbird, the saltmarsh sparrow (Ammodramus caudacutus), in a region where sea level is predictable with high accuracy and precision. We show that incorporating the timing of semidiurnal high tide events throughout the breeding season, including how this timing is affected by mean sea‐level rise, predicts a reproductive threshold that is likely to cause a rapid demographic shift. This shift is likely to threaten the persistence of saltmarsh sparrows beyond 2060 and could cause extinction as soon as 2035. Neither extinction date nor the population trajectory was sensitive to the emissions scenarios underlying sea‐level projections, as most of the population decline occurred before scenarios diverge. Our results suggest that the variation and complexity of climate‐driven variables could be important for understanding the potential responses of coastal species to sea‐level rise, especially for species that rely on coastal areas for reproduction.     

Control mechanisms of Carboniferous brachiopod zones in eastern Australia

Analysis of the Carboniferous brachiopod zones of eastern Australia shows that they were affected by two major controlling factors - eustatic changes of sea level, and a deterioration (cooling) of climate. Eustatic lowering of sea level caused the removal of the sea from narrow shelf areas and a loss of habitat, and was responsible for the first (late early to middle Visean) of two major episodes of faunal extinction. Subsequent transgression restored a modified warm-water cosmopolitan fauna to the shelf regions. Smaller changes in sea levels were probably responsible for the abrupt disappearance of many species or genera at zonal boundaries and their replacement by a new set of species and genera in succeeding zones. The second major episode of extinction was caused by the lowering of temperature in the latest Visean to early Namurian because of the rapid southerly movement of Australia. The warm water cosmopolitan fauna was eliminated and replaced by the low-diversity Gondwana fauna. Both mechanisms produced particular faunal signatures. The diversity of faunas on either side of the hiatus produced by eustatic lowering of sea level is constant in areas with uniform climatic conditions, and in warm to temperate regions there are low levels of endemism. Faunas associated with a sudden lowering of temperature suffer a significant drop in diversity but are characterized by a high level of endemism.     

Precambrian trace fossils and the rise of bilaterian animals

In this attempt to synthesize present knowledge into a coherent story, the Cambrian explosion is interpreted to represent a true adaptive radiation, an event similar to Phanerozoic radiation events in principle but unique in its possibilities. A model of bilaterian evolution helps explain how this particular event involved the sudden initiation of major coelomate phyla. In many of these groups, preservable skeletons are part of the basic body plan. Biochemical‐sequence analyses indicate that acoelomates and pseudocoelomates branched off long before the coelomate radiation. The great differences between Vendian and Cambrian ichnofaunas, therefore, may be the result of a major shift in composition from Vendian acoelomate‐pseudocoelomate‐procoelomate faunas to Phanerozoic faunas dominated by new coelomate groups.     

The Indochinese–Sundaic zoogeographic transition: a description and analysis of terrestrial mammal species distributions

Aim We describe the distributions of mammal species between the Indochinese and Sundaic subregions and examine the traditional view that the two faunas show a transition near the Isthmus of Kra on the Thai–Malay peninsula. Location Species distributions are described along a 2000‐km transect from 20° N (northernmost Thailand) to 1° N (Singapore). Methods For the 325 species of native non‐marine mammals occurring along the transect we used published records to provide a database of their distributional records by degree of latitude. Results Along the transect we found 128 Indochinese species with southern range limits, 121 Sundaic species with northern range limits, four un‐assignable endemics and 72 widespread species. In total, 152 southern and 147 northern range limits were identified, and their distribution provides no evidence for a narrow faunal transition near the Isthmus of Kra (10°30′ N) or elsewhere. Range limits of both bats and non‐volant mammals cluster in northernmost peninsular Malaysia (5° N) and 800 km further north, where the peninsula joins the continent proper (14° N). The clusters of northern and southern range limits are not concordant but overlap by 100–200 km. Similarly, the range limits of bats and non‐volant mammals cluster at slightly different latitudes. There are 30% fewer species and range limits in the central and northern peninsula (between 6 and 13° N), and 35 more widely distributed species have range gaps in this region. In addition, we found 70 fewer species at the southern tip of the peninsula (1° N) than at 3–4° N. Main conclusions The deficiencies of both species and species range limits in the central and northern peninsula are attributed to an area effect caused by repeated sea‐level changes. Using a new global glacioeustatic curve developed by Miller and associates we show that there were > 58 rapid sea‐level rises of > 40 m in the last 5 Myr that would have resulted in significant faunal compression and local population extirpation in the narrow central and northern parts of the peninsula. This new global sea‐level curve appears to account for the observed patterns of the latitudinal diversity of mammal species, the concentration of species range limits north and south of this area, the nature and position of the transition between biogeographical subregions, and possibly the divergence of the faunas themselves during the Neogene. The decline of species diversity at the southern end of the transect is attributed to a peninsula effect similar to that described elsewhere.     

Holocene vegetation change and the mammal faunas of South America and Africa

Aim Although sharing many similarities in their vegetation types, South America and Africa harbour very dissimilar recent mammal faunas, not only taxonomically but also in terms of several faunistic patterns. However late Pleistocene and mid‐Holocene faunas, albeit taxonomically distinct, presented many convergent attributes. Here we propose that the effects of the Holocene climatic change on vegetation physiognomy has played a crucial role in shaping the extant mammalian faunistic patterns. Location South America and Africa from the late Pleistocene to the present. Methods Data presented here have been compiled from many distinct sources, including palaeontological and neontological mammalian studies, palaeoclimatology, palynology, and publications on vegetation ecology. Data on Pleistocene, Holocene and extant mammal faunas of South America and Africa allowed us to establish a number of similar and dissimilar faunistic patterns between the two continents across time. We then considered what changes in vegetation physiognomy would have occurred under the late Pleistocene last glacial maximum (LGM) and the Holocene climatic optimum (HCO) climatic regimes. We have ordained these proposed vegetation changes along rough physiognomic seral stages according to assumptions based on current botanical research. Finally, we have associated our hypothesized vegetation changes in South America and Africa with mammalian faunistic patterns, establishing a putative causal relationship between them. Results The extant mammal faunas of South America and Africa differ widely in taxonomical composition; the number of medium and large species they possess; behavioural and ecological characteristics related to herbivore herding, migration and predation; and biogeographical patterns. All such distinctions are mostly related to the open formation faunas, and have been completely established around the mid‐Holocene. Considering that the mid‐Holocene was a time of greater humidity than the late Pleistocene, vegetation cover in South America and Africa would have been dominated by forest or closed vegetation landscapes, at least for most of their lower altitude tropical regions. We attribute the loss of larger‐sized mammal lineages in South America to the decrease of open vegetation area, and their survival in Africa to the existence of vast savannas in formerly steppic or desertic areas in subtropical Africa, north and south of the equator. Alternative explanations, mostly dealing with the disappearance of South American megamammals, are then reviewed and criticized. Main conclusions The reduction of open formation areas during the HCO in South America and Africa explains most of the present distinct faunistic patterns between the two continents. While South America would have lost most of its open formations within the 30° latitudinal belt, Africa would have kept large areas suitable to the open formation mammalian fauna in areas presently occupied by desert and semi‐arid vegetation. Thus, the same general climatic events that affected South America in the late Pleistocene and Holocene also affected Africa, leading to our present day faunistic dissimilarities by maintaining the African mammalian communities almost unchanged while dramatically altering those of South America.     

Mangrove response to environmental change in Australia's Gulf of Carpentaria

Across their range, mangroves are responding to coastal environmental change. However, separating the influence of human activities from natural events and processes (including that associated with climatic fluctuation) is often difficult. In the Gulf of Carpentaria, northern Australia (Leichhardt, Nicholson, Mornington Inlet, and Flinders River catchments), changes in mangroves are assumed to be the result of natural drivers as human impacts are minimal. By comparing classifications from time series of Landsat sensor data for the period 1987–2014, mangroves were observed to have extended seawards by up to 1.9 km (perpendicular to the coastline), with inland intrusion occurring along many of the rivers and rivulets in the tidal reaches. Seaward expansion was particularly evident near the mouth of the Leichhardt River, and was associated with peaks in river discharge with LiDAR data indicating distinct structural zones developing following each large rainfall and discharge event. However, along the Gulf coast, and particularly within the Mornington Inlet catchment, the expansion was more gradual and linked to inundation and regular sediment supply through freshwater input. Landward expansion along the Mornington Inlet catchment was attributed to the combined effects of sea level rise and prolonged periods of tidal and freshwater inundation on coastal lowlands. The study concluded that increased amounts of rainfall and associated flooding and sea level rise were responsible for recent seaward and landward extension of mangroves in this region.     

Towards a ‘Sea‐Level Sensitive’ dynamic model: impact of island ontogeny and glacio‐eustasy on global patterns of marine island biogeography

A synthetic model is presented to enlarge the evolutionary framework of the General Dynamic Model (GDM) and the Glacial Sensitive Model (GSM) of oceanic island biogeography from the terrestrial to the marine realm. The proposed ‘Sea‐Level Sensitive’ dynamic model (SLS) of marine island biogeography integrates historical and ecological biogeography with patterns of glacio‐eustasy, merging concepts from areas as diverse as taxonomy, biogeography, marine biology, volcanology, sedimentology, stratigraphy, palaeontology, geochronology and geomorphology. Fundamental to the SLS model is the dynamic variation of the littoral area of volcanic oceanic islands (defined as the area between the intertidal and the 50‐m isobath) in response to sea‐level oscillations driven by glacial–interglacial cycles. The following questions are considered by means of this revision: (i) what was the impact of (global) glacio‐eustatic sea‐level oscillations, particularly those of the Pleistocene glacial–interglacial episodes, on the littoral marine fauna and flora of volcanic oceanic islands? (ii) What are the main factors that explain the present littoral marine biodiversity on volcanic oceanic islands? (iii) How can differences in historical and ecological biogeography be reconciled, from a marine point of view? These questions are addressed by compiling the bathymetry of 11 Atlantic archipelagos/islands to obtain quantitative data regarding changes in the littoral area based on Pleistocene sea‐level oscillations, from 150 thousand years ago (ka) to the present. Within the framework of a model sensitive to changing sea levels, we discuss the principal factors affecting the geographical range of marine species; the relationships between modes of larval development, dispersal strategies and geographical range; the relationships between times of speciation, modes of larval development, ecological zonation and geographical range; the influence of sea‐surface temperatures and latitude on littoral marine species diversity; the effect of eustatic sea‐level changes and their impact on the littoral marine biota; island marine species–area relationships; and finally, the physical effects of island ontogeny and its associated submarine topography and marine substrate on littoral biota. Based on the SLS dynamic model, we offer a number of predictions for tropical, subtropical and temperate volcanic oceanic islands on how rates of immigration, colonization, in‐situ speciation, local disappearance, and extinction interact and affect the marine biodiversity around islands during glacials and interglacials, thus allowing future testing of the theory.     

Quaternary refugia are associated with higher speciation rates in mammalian faunas of the Western Palaearctic

Quaternary climate changes have contributed to shape the biogeographic distribution of extant species. The combination of climatic niche conservatism and glacial‐interglacial cycles forced many species to retract their range limits for surviving under the advance of Pleistocene ice‐sheets. Refugia offered geographical opportunities for species to retreat, persist and, later on, begin recolonization processes under favourable environmental conditions. Here we explore the hypothesis that refugia have been not only crucial for the survival of multiple species but also acted as speciation centres for Western Palaearctic mammals. We define ‘recurrent massive refugia’ as those geographical regions that have historically accumulated the highest levels of co‐occurring species for several Quaternary cycles. Our assemblage‐level analyses identify the existence of refugia within the Iberian Peninsula and the Atlantic French margin that were recurrently selected by most mammals. The topographic heterogeneity, climatic stability and microhabitat availability of these refugial areas may have offered suitable habitat conditions for multiple species during different climatic events over time. Using a Bayesian analysis of macroevolutionary mixtures we detected that the higher level of divergence and accumulative evolutionary changes in mammals of the Western Palaearctic are found in refugia. The continuous retractions and expansions of species’ ranges during the Pleistocene promoted temporal changes in the composition and richness of communities in this biogeographic region. The reorganization of ecological composition driven by cyclical climatic events may have favoured the emergence of biotic interactions and ecological responses conducive to novel selective pressures. Our findings suggest, first, that multiple climatic changes in the form of glacial‐interglacial transitions during the Quaternary have left a detectable imprint on the observed geographical patterns of species richness in mammalian faunas of the Western Palaearctic, and second, highlight the importance of refugia for the preservation of species (‘museums’) and as centers of speciation and endemism (‘cradles’) as well.     

Resilient forest faunal communities in South Africa: a legacy of palaeoclimatic change and extinction filtering?

Aim To examine the influence of climatic extinction filtering during the last glacial maximum (LGM; c. 18,000 yr bp ) and of the subsequent recolonization of forest faunas on contemporary assemblage composition in southern African forests. Location South Africa, Mozambique, Swaziland, Zimbabwe. Methods Data comprised presence/absence by quarter‐degree grid cell for forest‐dependent and forest‐associated birds, non‐volant mammals and frogs. Twenty‐one forest subregions were assigned to one of three previously identified forest types: Afrotemperate, scarp, and Indian Ocean coastal belt. Differences among forest types were examined through patterns and gradients of species richness and endemism, assemblage similarity, species turnover, and coefficients of species dispersal direction. The influence of contemporary environment on assemblage composition was investigated using partial canonical correspondence analysis. Several alternative biogeographical hypotheses for the recolonization of forest faunas were tested. Results Afrotemperate faunas are relatively species‐poor, have low species turnover, and are unsaturated and infiltrated by generalist species. In northern and central regions, communities are supplemented by recolonization from scarp forest refugia, and among frogs by autochthanous speciation in localized refugia. Scarp faunas are relatively species‐rich, contain many forest‐dependent species, have high species turnover, and overlap with coastal and Afrotemperate faunas. Coastal forests are relatively species‐rich with high species turnover. Main conclusions Afrotemperate communities were affected most by climatic extinction filtering events. Scarp forests were Afrotemperate refugia during the LGM and are a contemporary overlap zone between Afrotemperate and coastal forest. Coastal faunas derive from post‐LGM colonization along the eastern seaboard from tropical East African refugia. The greatest diversity is achieved in scarp and coastal forest faunas in northern KwaZulu–Natal province. This historical centre of diversity has influenced the faunal diversity of nearly all other forests in South Africa. The response of vertebrate taxa to large‐scale, historical processes is dependent on their relative mobility: forest birds best illustrate patterns resulting from post‐glacial faunal dispersal, while among mammals and frogs the legacy of climatic extinction filtering remains stronger.     

The biogeography of land snails in the islands of the Gulf of Guinea

Data on land snail diversity in the Gulf of Guinea islands is presented and the biogeography of the Gulf of Guinea fauna is discussed with reference to island snail faunas in the other areas of the world. Although the land snail faunas of the four islands clearly have west and central African affinities, speciation events following rare colonizations have led to high rates of endemism at the species and generic levels. The influence of island size, altitude, isolation and other factors on the development of the land snail faunas is discussed. The effect of land use changes on the land snail fauna over the last 150 years is evaluated. Current threats include recent changes in agricultural practice leading to the destruction of snail habitats in both forest and plantation areas. The potential threat posed by introduced species is also discussed. The Gulf of Guinea snail faunas appear to be in relatively good health in comparison to many other island snail faunas. However, the uniqueness of the faunas makes it imperative that further ecological and taxonomic research is undertaken both to understand the processes by which they developed and to evaluate the current status of many species in terms of distribution and threats.     

Sensitivity of mangrove soil organic matter decay to warming and sea level change

Mangroves are among the world's most carbon‐dense ecosystems, but they are threatened by rapid climate change and rising sea levels. The accumulation and decomposition of soil organic matter (SOM) are closely tied to mangroves' carbon sink functions and resistance to rising sea levels. However, few studies have investigated the response of mangrove SOM dynamics to likely future environmental conditions. We quantified how mangrove SOM decay is affected by predicted global warming (+4°C), sea level changes (simulated by altering of the inundation duration to 0, 2, and 6 hr/day), and their interaction. Whilst changes in inundation duration between 2 and 6 hr/day did not affect SOM decay, the treatment without inundation led to a 60% increase. A warming of 4°C caused SOM decay to increase by 21%, but longer inundation moderated this temperature‐driven increase. Our results indicate that (a) sea level rise is unlikely to decrease the SOM decay rate, suggesting that previous mangrove elevation gain, which has allowed mangroves to persist in areas of sea level rise, might result from changes in root production and/or mineral sedimentation; (b) sea level fall events, predicted to double in frequency and area, will cause periods of intensified SOM decay; (c) changing tidal regimes in mangroves due to sea level rise might attenuate increases in SOM decay caused by global warming. Our results have important implications for forecasting mangrove carbon dynamics and the persistence of mangroves and other coastal wetlands under future scenarios of climate change.