Phylogeographic Pattern of the Assassin Bug Sycanus bifidus Inferred from Mitochondrial Genomes and Nuclear Genes.

The assassin bug Sycanus bifidus has a wide distribution across southern China. This study explored its distribution and evolution by analyzing mitochondrial and nuclear ribosomal RNA genes, revealing how Pleistocene climate and geological changes shaped its phylogeography. We identified two main clades, A and B, that diverged in the Middle Pleistocene. Hainan Island's populations form a unique group within Clade A, suggesting that the Qiongzhou Strait served as a dispersal corridor during glaciation. Rising sea levels likely separated the Hainan population afterward. Ecological niche modeling showed that both populations have been viable since the last interglacial period, with demographic analyses indicating possible expansions during the Middle and Late Pleistocene, driven by favorable climates. This study highlights the significant effects of Pleistocene sea-level and climatic changes on the distribution and evolution of S. bifidus in China.

GIA imaging of 3-D mantle viscosity based on palaeo sea level observations - Part I: Sensitivity kernels for an Earth with laterally varying viscosity.

A key initial step in geophysical imaging is to devise an effective means of mapping the sensitivity of an observation to the model parameters, that is to compute its Fréchet derivatives or sensitivity kernel. In the absence of any simplifying assumptions and when faced with a large number of free parameters, the adjoint method can be an effective and efficient approach to calculating Fréchet derivatives and requires just two numerical simulations. In the Glacial Isostatic Adjustment problem, these consist of a forward simulation driven by changes in ice mass and an adjoint simulation driven by fictitious loads that are applied at the observation sites. The theoretical basis for this approach has seen considerable development over the last decade. Here, we present the final elements needed to image 3-D mantle viscosity using a dataset of palaeo sea-level observations. Developments include the calculation of viscosity Fréchet derivatives (i.e. sensitivity kernels) for relative sea-level observations, a modification to the numerical implementation of the forward and adjoint problem that permits application to 3-D viscosity structure, and a recalibration of initial sea level that ensures the forward simulation honours present-day topography. In the process of addressing these items, we build intuition concerning how absolute sea-level and relative sea-level observations sense Earth's viscosity structure and the physical processes involved. We discuss examples for potential observations located in the near field (Andenes, Norway), far field (Seychelles), and edge of the forebulge of the Laurentide ice sheet (Barbados). Examination of these kernels: (1) reveals why 1-D estimates of mantle viscosity from far-field relative sea-level observations can be biased; (2) hints at why an appropriate differential relative sea-level observation can provide a better constraint on local mantle viscosity and (3) demonstrates that sea-level observations have non-negligible 3-D sensitivity to deep mantle viscosity structure, which is counter to the intuition gained from 1-D radial viscosity Fréchet derivatives. Finally, we explore the influence of lateral variations in viscosity on relative sea-level observations in the Amundsen Sea Embayment and at Barbados. These predictions are based on a new global 3-D viscosity inference derived from the shear-wave speeds of GLAD-M25 and an inverse calibration scheme that ensures compatibility with certain fundamental geophysical observations. Use of the 3-D viscosity inference leads to: (1) generally greater complexity within the kernel; (2) an increase in sensitivity and presence of shorter length-scale features within lower viscosity regions; (3) a zeroing out of the sensitivity kernel within high-viscosity regions where elastic deformation dominates and (4) shifting of sensitivity at a given depth towards distal regions of weaker viscosity. The tools and intuition built here provide the necessary framework to explore inversions for 3-D mantle viscosity based on palaeo sea-level data.

Sea-level rise in Southwest Greenland as a contributor to Viking abandonment.

The first records of Greenland Vikings date to 985 CE. Archaeological evidence yields insight into how Vikings lived, yet drivers of their disappearance in the 15th century remain enigmatic. Research suggests a combination of environmental and socioeconomic factors, and the climatic shift from the Medieval Warm Period (~900 to 1250 CE) to the Little Ice Age (~1250 to 1900 CE) may have forced them to abandon Greenland. Glacial geomorphology and paleoclimate research suggest that the Southern Greenland Ice Sheet readvanced during Viking occupation, peaking in the Little Ice Age. Counterintuitively, the readvance caused sea-level rise near the ice margin due to increased gravitational attraction toward the ice sheet and crustal subsidence. We estimate ice growth in Southwestern Greenland using geomorphological indicators and lake core data from previous literature. We calculate the effect of ice growth on regional sea level by applying our ice history to a geophysical model of sea level with a resolution of ~1 km across Southwestern Greenland and compare the results to archaeological evidence. The results indicate that sea level rose up to ~3.3 m outside the glaciation zone during Viking settlement, producing shoreline retreat of hundreds of meters. Sea-level rise was progressive and encompassed the entire Eastern Settlement. Moreover, pervasive flooding would have forced abandonment of many coastal sites. These processes likely contributed to the suite of vulnerabilities that led to Viking abandonment of Greenland. Sea-level change thus represents an integral, missing element of the Viking story.

Historical connectivity and environmental filtering jointly determine the freshwater fish assemblages on Taiwan and Hainan Islands of China.

The biotas of Taiwan and Hainan Islands are of continental origin, but the manner with which historical and ecological factors shaped these insular species is still unclear. Here, we used freshwater fish as a model to fill this gap by quantifying the phylogenetic structure of the insular faunas and disentangling the relative contribution of potential drivers. Firstly, we used clustering and ordination analyses to identify regional species pools. To test whether the insular freshwater fish faunas were phylogenetically clustered or overdispersed, we calculated the net relatedness index (NRI) and the nearest taxon index (NTI). Finally, we implemented logistic regressions to disentangle the relative importance of species attributes (i.e., maximum body length, climatic niche dissimilarity [ND], and diversification) and historical connectivity (HC) in explaining the insular faunas. Our results showed that the most possible species pools of Taiwan are Zhejiang and Fujian provinces, and those of Hainan are Guangdong and Guangxi provinces. These insular faunas showed random phylogenetic structures in terms of NRI values. According to the NTI values, however, the Taiwanese fauna displayed more phylogenetic clustering, while the Hainanese one was more overdispersed. Both the standard and phylogenetic logistic regressions identified HC and climatic ND as the 2 top explanatory variables for species assemblages on these islands. Our reconstruction of the paleo-connected drainage basins provides insight into how historical processes and ecological factors interact to shape the freshwater fish fauna of the East Asian islands.

WALIS dashboard: An online tool to explore a global paleo sea-level database.

In this paper, we present WALIS Dashboard, an open-access interface to the World Atlas of Last Interglacial Shorelines (WALIS), which was developed and compiled thanks to funding from the European Research Council. WALIS is a database that includes thousands of samples (dated with different radiometric methods) and sea-level indicators formed during the Last Interglacial (~80 to 130 ka). The WALIS Dashboard was coded in R (shiny app), and allows querying a simplified version of WALIS by either geographic extent or by attributes. The user can then download the queried data and perform simple and reproducible data analysis. The WALIS Dashboard can be used both online and offline.

Tide gauges and satellites provide reliable measurements of sea-level changes since the beginning of the 20th century. To estimate sea-level changes before this period, we rely on sea-level indicators, i.e., geological features that were formed in close connection with sea level in the past, such as fossil shallow-water coral reefs or cemented beach deposits. Similar to tide gauge and satellite data, data on sea-level indicators are collected and standardised in databases, which are then made available to the scientific community (and the public at large) for further analysis. In this work, we present an open-source application that allows exploring, analysing, and downloading sea-level indicators included in the World Atlas of Last Interglacial Shorelines (WALIS), a paleo sea-level database compiled thanks to funding from the European Research Council. The application aims to facilitate access to this information for researchers, students, and citizens by creating more interactive and intuitive ways to explore the scientific information contained in WALIS.

Ecosystem design as an avenue for improving services provided by carbonate producing marine ecosystems.

Ecosystem Design (ED) is an approach for constructing habitats that places human needs for ecosystem services at the center of intervention, with the overarching goal of establishing self-sustaining habitats which require limited management. This concept was originally developed for use in mangrove ecosystems, and is understandably controversial, as it markedly diverges from other protection approaches that assign human use a minor priority or exclude it. However, the advantage of ED lies within the considered implementation of these designed ecosystems, thus preserving human benefits from potential later disturbances. Here, we outline the concept of ED in tropical carbonate depositional systems and discuss potential applications to aid ecosystem services such as beach nourishment and protection of coastlines and reef islands at risk from environmental and climate change, CO2 sequestration, food production, and tourism. Biological carbonate sediment production is a crucial source of stability of reef islands and reef-rimmed coastlines. Careful implementation of designed carbonate depositional ecosystems could help counterbalance sea-level rise and manage documented erosion effects of coastal constructions. Importantly, adhering to the core ethos of ED, careful dynamic assessments which provide a balanced approach to maximizing ecosystem services (e.g., carbonate production), should identify and avoid any potential damages to existing functioning ecosystems.

Demographic changes in Pleistocene sea turtles were driven by past sea level fluctuations affecting feeding habitat availability.

Pleistocene environmental changes are generally assumed to have dramatically affected species' demography via changes in habitat availability, but this is challenging to investigate due to our limited knowledge of how Pleistocene ecosystems changed through time. Here, we tracked changes in shallow marine habitat availability resulting from Pleistocene sea level fluctuations throughout the last glacial cycle (120-14 thousand years ago; kya) and assessed correlations with past changes in genetic diversity inferred from genome-wide SNPs, obtained via ddRAD sequencing, in Caribbean hawksbill turtles, which feed in coral reefs commonly found in shallow tropical waters. We found sea level regression resulted in an average 75% reduction in shallow marine habitat availability during the last glacial cycle. Changes in shallow marine habitat availability correlated strongly with past changes in hawksbill turtle genetic diversity, which gradually declined to ~1/4th of present-day levels during the Last Glacial Maximum (LGM; 26-19 kya). Shallow marine habitat availability and genetic diversity rapidly increased after the LGM, signifying a population expansion in response to warming environmental conditions. Our results suggest a positive correlation between Pleistocene environmental changes, habitat availability and species' demography, and that demographic changes in hawksbill turtles were potentially driven by feeding habitat availability. However, we also identified challenges associated with disentangling the potential environmental drivers of past demographic changes, which highlights the need for integrative approaches. Our conclusions underline the role of habitat availability on species' demography and biodiversity, and that the consequences of ongoing habitat loss should not be underestimated.

Temperature and historical land connectivity jointly shape the floristic relationship between Hainan Island and the neighbouring landmasses.

Present-day biodiversity in insular biota results from the interplay among geographical barriers, environmental filtering, and historical biogeography, but how these factors interact on insular biodiversity patterns is poorly understood. Here, we analysed the geographical patterns of beta diversity of seed plants between Hainan Island and the neighbouring landmasses in relation to space and the environmental factors to assess the relative effects of historical processes and ecological gradients on community assembly. We assessed beta diversity patterns by quantifying the turnover and nestedness components and used clustering and ordination to investigate the relationships between local floras from Hainan and the neighbouring landmasses. Utilising simple linear regression and linear mixed effect models, we evaluated the importance of historical processes and environmental gradients in shaping these beta diversity patterns. Our results show that the contributions of nestedness and turnover components to the total beta diversity vary across space. The flora of Hainan predominantly nests with the flora of Vietnam but shows larger species turnover with Guangdong, Guangxi, and Taiwan. Clustering and ordination analyses indicate that Hainan is first merged with Vietnam, after which it is grouped with mainland China and finally with Taiwan and the Philippines. The results of the linear mixed effect models consistently reveal that temperature, followed by the historical land connectivity, has the most important role in shaping the floristic dissimilarity. We conclude that the flora of Hainan is of continental origin and has the highest floristic affinity with Vietnam. The periodic emergence of a land bridge during Quaternary glacial cycles determines the origin of Hainan's flora, and temperature shapes the floristic dissimilarities via environmental filtering. Our study highlights the critical roles of historical sea level change and current environmental limitation in structuring the plant communities on Southeast Asian islands.

The geographic, environmental and phylogenetic evolution of the Alveolinoidea from the Cretaceous to the present day.

The superfamily Alveolinoidea is a member of the Order Miliolida, and comprises three main families, the Alveolinidae, the Fabulariidae and the Rhapydioninidae. They are examples of Larger benthic foraminifera (LBF), which are single-celled organisms with specific characteristic endoskeletons. Alveolinoids are found globally from the Cretaceous to the present day, and are important biostratigraphic index fossils in shallow-marine carbonates. They are often associated with hydrocarbon reservoirs, and exhibit provincialism with characteristic genera often confined to one of the American, Tethyan or Indo-Pacific provinces. Previously, the systematic study of the global interrelationship between the various alveolinoid lineages has not been possible because of the absence of biostratigraphic correlation between the geographically scattered assemblages, and the scarcity of described material from the Indo-Pacific province. Here we use the literature and new material from the Americas, the French Alps, Iran, Tibet, India and South East Asia, coupled with the use of the planktonic foraminiferal zonal (PZ) correlation scheme to propose a comprehensive, global, systematic analysis of the biostratigraphic, phylogenetic and paleogeographic evolution of the alveolinoids. The alveolinoids originated in the Cretaceous in the Tethyan province. During a global sea-level low stand, a westward migration of some alveolinoids species to the Americas occurred, a behaviour previously reported in contemporaneous orbitolinid LBF. After the Cretaceous/Palaeogene (K-P) event, which saw the extinction of all Cretaceous alveolinoids, rare new forms of alveolinoids evolved again, first in the Americas and later independently in Tethys. As was found in previous studies of rotalid LBF, sea-level low stands in the Paleocene also allowed some alveolinoid forms to migrate, but this time in an eastward direction from the Americas to Tethys, and from Tethys on to the Indo-Pacific province. Alveolinoids still exist today (Borelis and Alveolinella), the former of which is cosmopolitan, while the latter is restricted to the Indo-Pacific province. Throughout their phylogenetic history, alveolinoids characteristically exhibit convergent evolution, with the repeated re-occurrence of certain morphological features. Understanding this propensity to homoplasy is essential in understanding and constructing the phylogenetic relationships within the alveolinoid superfamily.

Coastal peat-beds and peatlands of the southern North Sea: their past, present and future.

Peat layers are well represented in the Holocene coastal deposits of the southern North Sea and provide evidence as to the extent and nature of the fens and bogs that occupied the region in the mid and late Holocene. While natural processes contributed to their demise, without human interference extensive areas of peatland would remain. We review the characteristics of the vegetation of these peatlands along with the processes that influenced their development. Spatial and temporal trends are explored through the use of palaeogeographic maps from three areas: the East Anglian Fenland, the Romney Marsh area and the Netherlands. The palaeoecological evidence indicates that eutrophic vegetation promoted by rising relative sea level (RSL) dominated in the mid Holocene, with a trend towards the development of oligotrophic and ombrotrophic vegetation in the late Holocene as the rate of RSL rise declined. Nevertheless, areas of eutrophic vegetation appear capable of long-term stability with areas of fen woodland and herbaceous fen persisting at some locations for several thousand years in the mid and late Holocene. Areas of active peat growth in the region are now largely confined to small remnants within agricultural settings. To retain their characteristic biodiversity these remnants have been managed using traditional practices, although their small size and fragmented distribution limits their biodiversity value. Biodiversity concerns and the ecosystem services peatlands provide, notably carbon sequestration and flood attenuation, underlie recent restoration projects. These efforts are likely to receive additional impetus as a consequence of rising water levels, given projected rates of RSL rise. Future large-scale restoration can be informed by a greater understanding of the processes that formed and sustained coastal peatlands in the past. We identify advances in palaeoenvironmental research that could enhance restoration efforts and help maximise the ecosystem services delivered through such projects.

Genetic differentiation through dispersal and isolation in two freshwater fish species from coastal basins of Northeastern Brazil

The coastal basins in Northeastern Brazil used in this study make up two different ecoregions for freshwater fishes (Amazonas estuary and coastal drainages, and Parnaiba) and two areas of endemism for Characiformes (Maranhão and Parnaíba), and exhibits a diversified yet poorly explored freshwater fish fauna. The population structure and biogeography of two migratory freshwater fish species that are commercially exploited from Maranhão and Parnaíba regions were herein analyzed. Molecular sequence data and statistical analyses were used to estimate haplotypes networks and lineage divergence times and correlated with hydrographic history of drainage and paleodrainages of the region. A total of 171 sequences was produced for both species, Schizodon dissimilis (coI, n = 70) and Prochilodus lacustris (D-loop, n = 101). All analyses identified the presence of three genetically delimited groups of S. dissimilis and six groups of P. lacustris. The lineage time analyses indicate diversification among these species within the past 1 million year. The results indicate the influence of geodispersal in the formation of the ichthyofauna in the studied area through headwater stream capture events and reticulated connections between the mouths of rivers along the coastal plain due to eustatic sea level fluctuations.(AU)

As bacias costeiras do nordeste do Brasil usadas neste estudo compõem duas ecorregiões diferentes para peixes de água doce (Estuário do Amazonas e drenagens costeiras e Parnaíba) e duas áreas de endemismo para Characiformes (Maranhão e Parnaíba), exibindo uma diversificada e ainda pouco explorada fauna de peixes de água doce. A estrutura populacional e biogeografia de duas espécies migradoras de peixes de água doce exploradas comercialmente nas regiões do Maranhão e Parnaíba foram analisadas. Dados de sequências moleculares e análises estatísticas foram utilizados para estimar redes de haplótipos e tempos de divergência entre linhagens, e foram correlacionados com a história hidrográfica das drenagens e paleodrenagens da região. Um total de 171 sequências foram geradas para ambas espécies, Schizodon dissimilis (coI, n = 70) e Prochilodus lacustris (D-loop, n = 101). Todas análises identificaram a presença de três grupos geneticamente delimitados para S. dissimilis e seis grupos para P. lacustris. A análise de tempo de divergência das linhagens indicou uma diversificação entre estas espécies nos últimos 1 Ma. Os resultados indicam influência da geodispersão na formação da ictiofauna do Maranhão, devido eventos de capturas de cabeceira e conexões reticuladas entre as fozes dos rios ao longo da planície costeira devido às flutuações eustáticas do nível do mar.(AU)

Impacts of Basin-Scale Climate Modes on Coastal Sea Level: a Review.

Global sea level rise (SLR) associated with a warming climate exerts significant stress on coastal societies and low-lying island regions. The rates of coastal SLR observed in the past few decades, however, have large spatial and temporal differences from the global mean, which to a large part have been attributed to basin-scale climate modes. In this paper, we review our current state of knowledge about climate modes' impacts on coastal sea level variability from interannual-to-multidecadal timescales. Relevant climate modes, their impacts and associated driving mechanisms through both remote and local processes are elaborated separately for the Pacific, Indian and Atlantic Oceans. This paper also identifies major issues and challenges for future research on climate modes' impacts on coastal sea level. Understanding the effects of climate modes is essential for skillful near-term predictions and reliable uncertainty quantifications for future projections of coastal SLR.

Relative sea-level change regulates organic carbon accumulation in coastal habitats.

Because coastal habitats store large amounts of organic carbon (Corg ), the conservation and restoration of these habitats are considered to be important measures for mitigating global climate change. Although future sea-level rise is predicted to change the characteristics of these habitats, its impact on their rate of Corg sequestration is highly uncertain. Here we used historical depositional records to show that relative sea-level (RSL) changes regulated Corg accumulation rates in boreal contiguous seagrass-saltmarsh habitats. Age-depth modeling and geological and biogeochemical approaches indicated that Corg accumulation rates varied as a function of changes in depositional environments and habitat relocations. In particular, Corg accumulation rates were enhanced in subtidal seagrass meadows during times of RSL rise, which were caused by postseismic land subsidence and climate change. Our findings identify historical analogs for the future impact of RSL rise driven by global climate change on rates of Corg sequestration in coastal habitats.

Causes of accelerating sea level on the East Coast of North America.

The tide-gauge record from the North American East Coast reveals significant accelerations in sea level starting in the late twentieth century. The estimated post-1990 accelerations range from near zero to ∼0.3 mm yr-2. We find that the observed sea level acceleration is well modeled using several processes: mass change in Greenland and Antarctica as measured by the Gravity Recovery and Climate Experiment satellites; ocean dynamic and steric variability provided by the GECCO2 ocean synthesis; and the inverted barometer effect. However, to achieve this fit requires estimation of an admittance for the dynamical and steric contribution, possibly due to the coarse resolution of this analysis or to simplifications associated with parameterization of bottom friction in the shallow coastal areas. The acceleration from ice loss alone is equivalent to a regional sea level rise in one century of 0.2 m in the north and 0.75 m in the south of this region.

Spatial Patterns of Sea Level Variability Associated with Natural Internal Climate Modes.

Sea level rise (SLR) can exert significant stress on highly populated coastal societies and low-lying island countries around the world. Because of this, there is huge societal demand for improved decadal predictions and future projections of SLR, particularly on a local scale along coastlines. Regionally, sea level variations can deviate considerably from the global mean due to various geophysical processes. These include changes of ocean circulations, which partially can be attributed to natural, internal modes of variability in the complex Earth's climate system. Anthropogenic influence may also contribute to regional sea level variations. Separating the effects of natural climate modes and anthropogenic forcing, however, remains a challenge and requires identification of the imprint of specific climate modes in observed sea level change patterns. In this paper, we review our current state of knowledge about spatial patterns of sea level variability associated with natural climate modes on interannual-to-multidecadal timescales, with particular focus on decadal-to-multidecadal variability. Relevant climate modes and our current state of understanding their associated sea level patterns and driving mechanisms are elaborated separately for the Pacific, the Indian, the Atlantic, and the Arctic and Southern Oceans. We also discuss the issues, challenges and future outlooks for understanding the regional sea level patterns associated with climate modes. Effects of these internal modes have to be taken into account in order to achieve more reliable near-term predictions and future projections of regional SLR.

Empty Niches after Extinctions Increase Population Sizes of Modern Corals.

Large environmental fluctuations often cause mass extinctions, extirpating species and transforming communities [1, 2]. While the effects on community structure are evident in the fossil record, demographic consequences for populations of individual species are harder to evaluate because fossils reveal relative, but not absolute, abundances. However, genomic analyses of living species that have survived a mass extinction event offer the potential for understanding the demographic effects of such environmental fluctuations on extant species. Here, we show how environmental variation since the Pliocene has shaped demographic changes in extant corals of the genus Orbicella, major extant reef builders in the Caribbean that today are endangered. We use genomic approaches to estimate previously unknown current and past population sizes over the last 3 million years. Populations of all three Orbicella declined around 2-1 million years ago, coincident with the extinction of at least 50% of Caribbean coral species. The estimated changes in population size are consistent across the three species despite their ecological differences. Subsequently, two shallow-water specialists expanded their population sizes at least 2-fold, over a time that overlaps with the disappearance of their sister competitor species O. nancyi (the organ-pipe Orbicella). Our study suggests that populations of Orbicella species are capable of rebounding from reductions in population size under suitable conditions and that the effective population size of modern corals provides rich standing genetic variation for corals to adapt to climate change. For conservation genetics, our study suggests the need to evaluate genetic variation under appropriate demographic models.

Global Ocean Integrals and Means, with Trend Implications.

Understanding the ocean requires determining and explaining global integrals and equivalent average values of temperature (heat), salinity (freshwater and salt content), sea level, energy, and other properties. Attempts to determine means, integrals, and climatologies have been hindered by thinly and poorly distributed historical observations in a system in which both signals and background noise are spatially very inhomogeneous, leading to potentially large temporal bias errors that must be corrected at the 1% level or better. With the exception of the upper ocean in the current altimetric-Argo era, no clear documentation exists on the best methods for estimating means and their changes for quantities such as heat and freshwater at the levels required for anthropogenic signals. Underestimates of trends are as likely as overestimates; for example, recent inferences that multidecadal oceanic heat uptake has been greatly underestimated are plausible. For new or augmented observing systems, calculating the accuracies and precisions of global, multidecadal sampling densities for the full water column is necessary to avoid the irrecoverable loss of scientifically essential information.

Gene flow, population growth and a novel substitution rate estimate in a subtidal rock specialist, the black-faced blenny Tripterygion delaisi (Perciformes, Blennioidei, Tripterygiidae) from the Adriatic Sea.

Population histories depend on the interplay between exogeneous and endogeneous factors. In marine species, phylogeographic and demographic patterns are often shaped by sea level fluctuations, water currents and dispersal ability. Using mitochondrial control region sequences (n = 120), we infer phylogeographic structure and historic population size changes of a common littoral fish species, the black-faced blenny Tripterygion delaisi (Perciformes, Blennioidei, Tripterygiidae) from the north-eastern Adriatic Sea. We find that Adriatic T. delaisi are differentiated from conspecific populations in the remaining Mediterranean, but display little phylogeographic structure within the Adriatic basin. The pattern is consistent with passive dispersal of planktonic larvae along cyclonic currents within the Adriatic Sea, but limited active dispersal of adults. Demographic reconstructions are consistent with recent population expansion, probably triggered by rising sea levels after the last glacial maximum (LGM). Placing the onset of population growth between the LGM and the warming of surface waters (18 000-13 000 years BP) and employing a novel expansion dating approach, we inferred a substitution rate of 2.61-3.61% per site per MY. Our study is one of only few existing investigations of the genetic structure of animals within the Adriatic basin and is the first to provide an estimate for mitochondrial control region substitution rates in blennioid fishes.

Genomic tests of the species-pump hypothesis: Recent island connectivity cycles drive population divergence but not speciation in Caribbean crickets across the Virgin Islands.

Harnessing the power of genomic scans, we test the debated "species pump" hypothesis that implicates repeated cycles of island connectivity and isolation as drivers of divergence. This question has gone understudied given the limited resolution of past molecular markers for studying such dynamic phenomena. With an average of 32,000 SNPs from the genome of 136 individuals from 10 populations of a Caribbean flightless ground cricket species (Amphiacusta sanctaecrucis) and a complementary set of statistical approaches, we infer a stepping-stone colonization model and high levels of genetic differentiation across the Virgin Islands, which have been periodically interconnected until 8 ka. Estimates of divergence times from models based on the site frequency spectrum coincide with a period of repeated connection and fragmentation of the islands at 75-130 ka. These results are consistent with a role of island connectivity cycles in promoting genomic divergence and indicate that the genetic distinctiveness of island populations has persisted despite subsequent and extended interisland connections identified from bathymetric data. We discuss these findings in the broader context of Caribbean biogeography, and more specifically why high levels of genomic divergence across the Virgin Islands associated with repeated connectivity cycles do not actually translate into species diversification.

Variation in palaeo-shorelines explains contemporary population genetic patterns of rocky shore species.

Processes driving and maintaining disjunct genetic populations in marine systems are poorly understood, owing to a lack of evidence of hard barriers that could have shaped patterns of extant population structure. Here, we map two genetically divergent lineages of an obligate rocky shore fish, Clinus cottoides, and model sea-level change during the last 110 000 years to provide the first evidence of a vicariant event along the southern coastline of Africa. Results reveal that lowered sea levels during glacial periods drastically reduced rocky intertidal habitat, which may have isolated populations in two refugia for at least 40 000 years. Contemporary coastal dynamics and oceanography explain secondary contact between lineages. This scenario provides an explanation for the origin of population genetic breaks despite a lack of obvious present-day geographical barriers and highlights the need for including palaeo-oceanography in unravelling extant population patterns.