Regional patterns of evolutionary turnover in Neogene coral reefs from the central Indo-West Pacific Ocean

The Indo-Pacific is an area of intense ecological interest, not least because of the region’s rich biodiversity. Important insights into the origins, evolutionary history, and maintenance of Indo-Pacific reef faunas depend upon the analysis of faunal occurrences derived from detailed stratigraphic sections. We investigated Neogene origination and extinction patterns derived from a combination of new coral occurrences and previously published records from the central Indo-West Pacific Ocean (cIWP, Indonesia, Papua New Guinea and Fiji). Two faunal turnover events were observed. In the first, an increase in generic richness of Scleractinia from the cIWP during the middle Miocene (17–14 Ma) coincided with both large-scale sea level fluctuations and the great Mid-Miocene collision event. We raise the hypothesis that Mid-Miocene origination was facilitated by habitat and population fragmentation associated with tectonism and sea level fall. The second, subsequent, turnover event was characterized by an overall lowering of generic diversity throughout the late Miocene and Pliocene (7–3 Ma), and was followed by a pronounced pulse of extinction at the Pliocene–Pleistocene boundary (~2.6 Ma). With the exception of the onset of Pleistocene sea-level cycles and the onset of northern hemisphere glaciation around 2.5 Ma, which might explain increased extinction during this time interval, there are no tectonic, eustatic, climatic or oceanographic events that neatly coincide with this second episode of Neogene coral taxonomic turnover. Our results reveal a total of 62 genera, including synonyms, from the Miocene to the Pleistocene. Neither episode of turnover among coral genera is exactly coincident with turnover in the Atlantic thus regional environmental change is found to drive Neogene reef dynamics.     

Neogene reef coral assemblages of the Bocas del Toro region, Panama: the rise of Acropora palmata

Temporal patterns are evaluated in Neogene reef coral assemblages from the Bocas del Toro Basin of Panama in order to understand how reef ecosystems respond to long-term environmental change. Analyses are based on a total of 1,702 zooxanthellate coral specimens collected from six coral-bearing units ranging in age from the earliest Late Miocene to the Early Pleistocene: (1) Valiente Formation (12–11 Ma), (2) Fish Hole Member of the Old Bank Formation (5.8–5.6 Ma), (3) La Gruta Member of the Isla Colon Formation (2.2–1.4 Ma), (4) Ground Creek Member of the Isla Colon Formation (2.2–1.4 Ma), (5) Mimitimbi Member of the Urracá Formation (1.2–0.8 Ma), and (6) Hill Point Member of the Urracá Formation (1.2–0.8 Ma). Over 100 coral species occur in the six units, with faunal assemblages ranging from less than 10% extant taxa (Valiente Formation) to over 85% extant taxa (Ground Creek Member). The collections provide new temporal constraints on the emergence of modern Caribbean reefs, with the La Gruta Member containing the earliest occurrence of large monospecific stands of the dominant Caribbean reef coral Acropora palmata, and the Urracá Formation containing the last fossil occurrences of 15 regionally extinct taxa. Canonical correspondence analysis of 41 Late Miocene to Recent reef coral assemblages from the Caribbean region suggests changes in community structure coincident with effective oceanic closure of the Central American Seaway (~3.5 Ma). These changes, including increased Acropora dominance, may have contributed to a protracted period of elevated extinction debt prior to the major peak in regional coral extinctions (~2–1 Ma).     

Planktonic foraminiferal turnover, diversity fluctuations and geochemical signals across the Eocene/Oligocene boundary in Tanzania

A major turnover in planktonic foraminifera occurred across the Eocene/Oligocene (E/O) boundary. New drill holes through the E/O boundary in southern Tanzania contain extremely well-preserved and diverse assemblages of planktonic foraminifera. Here we document a 1.2 million year record of assemblages, diversity and stable isotope fluctuations through this critical interval, which is often dissolved and/or recrystallised in carbonate-rich facies. The E/O boundary is marked by the abrupt extinction of all five remaining species of the family Hantkeninidae and a distinct size reduction in the genus Pseudohastigerina. The boundary is preceded over a short stratigraphic interval by the extinction of Turborotalia cerroazulensis, Turborotalia cocoaensis and Turborotalia cunialensis. Quantitative analysis of planktonic foraminiferal assemblages reveals significant changes in the abundance of certain species and the composition of the assemblages. We compare diversity fluctuations to the stable isotope record of Pseudohastigerina naguewichiensis and use multispecies stable isotope analyses to determine the life habitats of the most important species. A major shift in the evenness occurs at ~ 33.8 Ma associated with the extinction of the T cerroazulensis group suggesting acute ecological disturbance. We propose that the extinction of the T. cerroazulensis group at ~ 33.8 Ma was directly related to cooling of sea surface temperatures, while the extinction of Hantkeninidae was due to modifications in the thermal structure of the oceans and associated productivity changes. After the extinctions, renewed origination and diversification occurred, leading to a characteristic Oligocene planktonic foraminifer assemblage.     

A dynamic global equilibrium in carnivoran diversification over 20 million years

The ecological and evolutionary processes leading to present-day biological diversity can be inferred by reconstructing the phylogeny of living organisms, and then modelling potential processes that could have produced this genealogy. A more direct approach is to estimate past processes from the fossil record. The Carnivora (Mammalia) has both substantial extant species richness and a rich fossil record. We compiled species-level data for over 10 000 fossil occurrences of nearly 1400 carnivoran species. Using this compilation, we estimated extinction, speciation and net diversification for carnivorans through the Neogene (22–2 Ma), while simultaneously modelling sampling probability. Our analyses show that caniforms (dogs, bears and relatives) have higher speciation and extinction rates than feliforms (cats, hyenas and relatives), but lower rates of net diversification. We also find that despite continual species turnover, net carnivoran diversification through the Neogene is surprisingly stable, suggesting a saturated adaptive zone, despite restructuring of the physical environment. This result is strikingly different from analyses of carnivoran diversification estimated from extant species alone. Two intervals show elevated diversification rates (13–12 Ma and 4–3 Ma), although the precise causal factors behind the two peaks in carnivoran diversification remain open questions.     

Patterns of diversity for aphidiine (Hymenoptera: Braconidae) parasitoid assemblages on aphids (Homoptera)

We used aphids (Aphidae) as a representative hemimetabolous host family to investigate patterns of parasitoid (Aphidiine) assemblage size. The aphidiine assemblages from 477 aphid species were used to estimate average assemblage size and the influence of eight ecological and taxonomic variables. Aphids species support an average of 1.7 aphidiine species. Aphid subfamily and invasion status (native or exotic) were the most important determinants of parasitoid richness, explaining 28% of the deviance in aphidiine assemblage size. Aphids within the largest aphid subfamily, the Aphidinae, support larger parasitoid assemblages than those in other subfamilies. Parasitoid diversity was also highest on exotic aphid hosts (within the Aphidinae) and on hosts in developed habitats (agricultural or urban), though the latter effect is weak. Patterns related to aphid food plant architecture were influenced by an interaction with aphid invasion status; parasitoid diversity drops with increasing architectural complexity on exotic aphids, whereas the diversities on native aphid hosts are similar on different plant types. Weak effects were also found for aphid food plant alternation (whether or not aphids switch hosts seasonally) and climate (annual range in temperature); alternating aphids support more parasitoids than non-alternating hosts, and parasitoid assemblage size is lowest in warm climates. Taxonomic isolation of aphids at the generic level showed no significant relationship with parasitoid diversity. Finally, in contrast to parasitoid assemblages on holometabolous hosts, sample size effects were weak for aphids, possibly due to the narrow host ranges of aphidiines. Received: 22 November 1997 / Accepted: 7 March 1998     

Cactus species turnover and diversity along a latitudinal transect in the Chihuahuan Desert Region

A standardized sampling method was used to evaluate turnover (β diversity) among cactus species assemblages along a 798 km long latitudinal megatransect across the Chihuahuan Desert Region, from north-central Mexico to southern Texas. A total of 71 cactus species were found along the megatransect, 66.2% of which appeared at low frequencies, mostly as a consequence of their highly discontinuous distribution pattern. At the scale the study was conducted, there was always species turnover among cactus assemblages. The rate of turnover among contiguous sites primarily fluctuated from low to medium, but when all site combinations were considered (contiguous and non-contiguous), medium β diversity values were predominant (β = 0.331–0.66); however, 25.4% of the site pair combinations registered high values (β = 0.661–1.0). Our results showed that turnover among cactus species assemblages in the CDR does not consist for the most part of a process of species succession in the geographic space. Instead, we concluded that the continuous spatial changes in cactus species composition are primarily explained by the commonly intermittent distribution patterns of the species, by the presence in the megatransect of species at the margin of their distribution range, and, to a lesser extent, by the existence of narrowly endemic species.     

Mammalian Faunal Dynamics During the Last 1.8 Million Years of the Cretaceous in Garfield County, Montana

This study provides an analysis of biotic change in successive mammalian communities during the last 1.8 million years of the Cretaceous (67.3–65.58 Ma) from the Hell Creek Formation in Garfield County, Montana. Results show changes in relative abundances of species, mean individual body size, and to some extent taxonomic composition through the Hell Creek Formation. These results are interpreted as “normal” mammalian responses to fluctuating temperatures during the latest Cretaceous. By contrast, the extinction of 22–27 mammalian species at or near the Cretaceous-Tertiary (K-T) boundary cannot be explained by the coincident cooling interval alone. At the scale of temporal resolution available, these fossil data are inconsistent with an extended gradual pattern of extinction (linear-response) and are most consistent with either a non-linear response pattern for the K-T extinction, resulting from the accumulated stress of multiple long- and short-term environmental perturbations (e.g., climate change, sea-level regression, volcanism, an extraterrestrial impact), or a single, short-term cause (an extraterrestrial impact).     

Nested bird and micro-habitat assemblages in a peatland archipelago

Biotic assemblages of insular habitats are nested when poor assemblages are subsets of richer ones. Nestedness of species assemblages is frequent and may result from selective extinction or frequent colonization in insular habitats. It may also be created by a nested distribution of habitats among islands or by sampling bias. We sampled 67 isolated peatlands (7–843 ha) in southern Quebec, Canada, to measure nestedness of bird species assemblages among peatlands and assess the habitat nestedness hypothesis. Species and microhabitat assemblages were both strongly nested among peatlands. Whether sites were ranked by species richness, microhabitat richness or peatland area had no effect on nestedness. However, microhabitat nestedness was significantly reduced when sites were sorted by area rather than by microhabitat richness. As expected, if bird-microhabitat associations are responsible for the nested pattern of distribution, we found a positive correlation between the contributions of bird species and microhabitats to individual site nestedness. Nevertheless, microhabitat assemblages were significantly less nested than bird species assemblages, possibly because of frequent recolonization by birds or uneven sampling among sites. Received: 12 June 1998 / Accepted: 20 September 1998     

Environmental change drove macroevolution in cupuladriid bryozoans

Most macroevolutionary events are correlated with changes in the environment, but more rigorous evidence of cause and effect has been elusive. We compiled a 10 Myr record of origination and extinction, changes in mode of reproduction, morphologies and abundances of cupuladriid bryozoan species, spanning the time when primary productivity collapsed in the southwestern Caribbean as the Isthmus of Panama closed. The dominant mode of reproduction shifted dramatically from clonal to aclonal, due in part to a pulse of origination followed by extinction that was strongly selective in favour of aclonal species. Modern-day studies predict reduced clonality in increasingly oligotrophic conditions, thereby providing a mechanistic explanation supporting the hypothesis that the collapse in primary productivity was the cause of turnover. However, whereas originations were synchronous with changing environments, extinctions lagged 1–2 Myr. Extinct species failed to become more robust and reduce their rate of cloning when the new environmental conditions arose, and subsequently saw progressive reductions in abundance towards their delayed demise. Environmental change is therefore established as the root cause of macroevolutionary turnover despite the lag between origination and extinction.     

小兴安岭阔叶红松林地表甲虫Beta多样性

Beta多样性用来衡量集群内物种组成的变异性,可以被分解为空间物种转换和物种集群镶嵌两个组分,是揭示群落构建机制的重要基础。目前开展了较多的地上生态系统beta多样性研究,然而地下生态系统beta多样性进展缓慢。以小兴安岭凉水和丰林自然保护区为研究地区,于2015年8、10月采用陷阱法对阔叶红松林进行调查,揭示地表甲虫(步甲科、隐翅虫科、葬甲科)的beta多样性。结果表明:(1)凉水共发现39种、856只地表甲虫,丰林共发现43种、1182只地表甲虫。8月凉水明显具有较高的全部甲虫(三个科的总和)物种多样性和丰富度,10月正好相反。(2)凉水和丰林之间地表甲虫beta多样性的差异仅发现于8月的步甲科和葬甲科之间。(3)凉水和丰林地表甲虫的beta多样性主要由空间物种转换组成,物种集群镶嵌对beta多样性的贡献很小,说明地表甲虫物种组成变异主要由本地物种之间较高的转换引起。研究表明小兴安岭阔叶红松林地表甲虫的beta多样性主要由空间物种转换组成,在揭示群落构建机制过程中,其内部物种交换和环境调控不容忽视。     

Evidence for a Late Pliocene faunal transition based on a new rodent assemblage from Oldowan locality Hadar A.L. 894, Afar Region, Ethiopia

The time interval between 3 Ma and 2 Ma marks several important transitions in human evolution, including the extinction of Australopithecus afarensis, the origin of the genus Homo, and the appearance of concentrated stone tool assemblages forming recognizable archaeological sites. The period also marks important changes in Earth’s climatic history, with the onset of northern hemisphere glaciation starting sometime between 2.8 Ma and 2.5 Ma, and it remains an unresolved question in paleoanthropology whether or not the global climatic events influenced in whole or in part, local terrestrial paleoenvironments in Africa and, through this, the course of human evolution.Changes in the terrestrial mammalian faunas of East Africa during this time interval are an important source of data about terrestrial paleoenvironments, and it has been argued that during this time period the mammalian faunas of Africa experienced a sudden pulse in the extinction and origination of taxa. The data corroborating this Turnover Pulse Hypothesis derive from both large mammal and micromammal data, though the fossil record of the former is much more abundant in this interval. New micromammal fossils recovered from ca. 2.4 Ma deposits at locality A.L. 894, low in the Busidima Formation in the Hadar study area of the Afar region, Ethiopia, reveal a significant faunal turnover when compared with previously published material from older 3.2 Ma micromammal assemblages from the Hadar Formation deposits. The results support the hypothesis of a major faunal transition, but larger sample sizes and more extensive temporal sampling are needed to refine the time and rate of change within this interval at Hadar.     

Global Taxonomic Diversity of Anomodonts (Tetrapoda,Therapsida) and the Terrestrial Rock Record Across the Permian-Triassic Boundary

The end-Permian biotic crisis (∼252.5 Ma) represents the most severe extinction event in Earth''s history. This paper investigates diversity patterns in Anomodontia, an extinct group of therapsid synapsids (‘mammal-like reptiles’), through time and in particular across this event. As herbivores and the dominant terrestrial tetrapods of their time, anomodonts play a central role in assessing the impact of the end-Permian extinction on terrestrial ecosystems. Taxonomic diversity analysis reveals that anomodonts experienced three distinct phases of diversification interrupted by the same number of extinctions, i.e. an end-Guadalupian, an end-Permian, and a mid-Triassic extinction. A positive correlation between the number of taxa and the number of formations per time interval shows that anomodont diversity is biased by the Permian-Triassic terrestrial rock record. Normalized diversity curves indicate that anomodont richness continuously declines from the Middle Permian to the Late Triassic, but also reveals all three extinction events. Taxonomic rates (origination and extinction) indicate that the end-Guadalupian and end-Permian extinctions were driven by increased rates of extinction as well as low origination rates. However, this pattern is not evident at the final decline of anomodont diversity during the Middle Triassic. Therefore, it remains unclear whether the Middle Triassic extinction represents a gradual or abrupt event that is unique to anomodonts or more common among terrestrial tetrapods. The end-Permian extinction represents the most distinct event in terms of decline in anomodont richness and turnover rates.     

Diversity dynamics of Miocene mammals in relation to the history of tectonism and climate

Continental biodiversity gradients result not only from ecological processes, but also from evolutionary and geohistorical processes involving biotic turnover in landscape and climatic history over millions of years. Here, we investigate the evolutionary and historical contributions to the gradient of increasing species richness with topographic complexity. We analysed a dataset of 418 fossil rodent species from western North America spanning 25 to 5 Ma. We compared diversification histories between tectonically active (Intermontane West) and quiescent (Great Plains) regions. Although diversification histories differed between the two regions, species richness, origination rate and extinction rate per million years were not systematically different over the 20 Myr interval. In the tectonically active region, the greatest increase in originations coincided with a Middle Miocene episode of intensified tectonic activity and global warming. During subsequent global cooling, species richness declined in the montane region and increased on the Great Plains. These results suggest that interactions between tectonic activity and climate change stimulate diversification in mammals. The elevational diversity gradient characteristic of modern mammalian faunas was not a persistent feature over geologic time. Rather, the Miocene rodent record suggests that the elevational diversity gradient is a transient feature arising during particular episodes of Earth''s history.     

Latitudinal diversity gradients for brachiopod genera during late Palaeozoic time: links between climate, biogeography and evolutionary rates

Aim The latitudinal diversity gradient, in which taxonomic richness is greatest at low latitudes and declines towards the poles, is a pervasive feature of the biota through geological time. This study utilizes fossil data to examine how the latitudinal diversity gradient and associated spatial patterns covaried through the major climate shifts at the onset and end of the late Palaeozoic ice age. Location Data were acquired from fossil localities from around the world. Methods Latitudinal patterns of diversity, mean geographical range size and macroevolutionary rates were constructed from a literature‐derived data base of occurrences of fossil brachiopod genera in space and time. The literature search resulted in a total of 18,596 occurrences for 991 genera from 2320 localities. Results Climate changes associated with the onset of the late Palaeozoic ice age (c. 327 Ma) altered the biogeographical structure of the brachiopod fauna by the preferential elimination of narrowly distributed, largely tropical genera when glaciation began. Because the oceans were left populated primarily with widespread genera, the slope of the diversity gradient became gentle at this time, and the gradient of average latitudinal range size weakened. In addition, because narrowly distributed genera had intrinsically high rates of origination and extinction, the gradients of both of these macroevolutionary rates were also reduced. These patterns were reversed when the ice age climate abated in early Permian time (c. 290 Ma): narrowly distributed genera rediversified at low latitudes, restoring steep gradients of diversity, average latitudinal range size and macroevolutionary rates. Main conclusions During late Palaeozoic time, these latitudinal gradients for brachiopods may have been linked by the increased magnitude of seasonality during the late Palaeozoic ice age. Pronounced seasonality would have prevented the existence of genera with narrow latitudinal ranges. These results for the late Palaeozoic ice age suggest a climatic basis for the present‐day latitudinal diversity gradient.     

Temporal Beta Diversity of Bird Assemblages in Agricultural Landscapes: Land Cover Change vs. Stochastic Processes

Temporal variation in the composition of species assemblages could be the result of deterministic processes driven by environmental change and/or stochastic processes of colonization and local extinction. Here, we analyzed the relative roles of deterministic and stochastic processes on bird assemblages in an agricultural landscape of southwestern France. We first assessed the impact of land cover change that occurred between 1982 and 2007 on (i) the species composition (presence/absence) of bird assemblages and (ii) the spatial pattern of taxonomic beta diversity. We also compared the observed temporal change of bird assemblages with a null model accounting for the effect of stochastic dynamics on temporal beta diversity. Temporal assemblage dissimilarity was partitioned into two separate components, accounting for the replacement of species (i.e. turnover) and for the nested species losses (or gains) from one time to the other (i.e. nestedness-resultant dissimilarity), respectively. Neither the turnover nor the nestedness-resultant components of temporal variation were accurately explained by any of the measured variables accounting for land cover change (r²<0.06 in all cases). Additionally, the amount of spatial assemblage heterogeneity in the region did not significantly change between 1982 and 2007, and site-specific observed temporal dissimilarities were larger than null expectations in only 1% of sites for temporal turnover and 13% of sites for nestedness-resultant dissimilarity. Taken together, our results suggest that land cover change in this agricultural landscape had little impact on temporal beta diversity of bird assemblages. Although other unmeasured deterministic process could be driving the observed patterns, it is also possible that the observed changes in presence/absence species composition of local bird assemblages might be the consequence of stochastic processes in which species populations appeared and disappeared from specific localities in a random-like way. Our results might be case-specific, but if stochastic dynamics are generally dominant, the ability of correlative and mechanistic models to predict land cover change effects on species composition would be compromised.     

Diversification and extinction patterns among Neogene perimediterranean mammals

The best mammalian fossil record during the Neogene of Western Europe is that of the rodents, the most successful and diversified mammal order. The study of origination and extinction during the Neogene (24-3 Ma BP) in one of the best-documented areas, Spain and southern France, gives an insight into the dynamics of these communities and indicates the possible nature of the driving forces. Three main periods of time show a high rate of origination: the late Burdigalian (17.5 Ma BP), the early Vallesian (11.5-11 Ma BP) and the early Pliocene (4.2-3.8 Ma BP). Two of these high origination-rate periods are immediately followed by important extinction events during which all cohorts are deeply affected (11.5-11 Ma BP and 4.2-3.8 Ma BP). The most important extinction event seems to occur during the early Vallesian (11.5-11 Ma BP), which probably includes the middle/late Miocene boundary. At the Miocene/Pliocene boundary, and during the early Pliocene, the faunal turnover seems to become faster, inducing a strong decrease of the mean species duration. Whereas the main immigration event, which occurs at 17.5 Ma BP, can be related to other faunal migrations in terms of the closure of the Tethys, as it occurs also in eastern Africa and in southwest Asia, the middle/late Miocene boundary event may have been related to a period of ice growth in the Southern Hemisphere. The extinction event that affects the planktonic foraminifera at 12 Ma BP cannot be chronologically correlated to this southwestern European land-mammal extinction event, because the calibration of the marine fossil record during that time-span has to be precise. Some limited terrestrial faunal exchanges that occur during the Messinian between southwestern Europe and northwestern Africa do not deeply affect the general faunal dynamics. Both allochthonous cohorts of immigrants become rapidly extinct. Several endemic rodent faunas, indicating insular conditions, have been reported from the southern edge of the western European continent from the middle Miocene up to the Pliocene. All show low taxonomic diversity, strong endemism and short survival. Some of them, like those of the Gargano Islands during the late Miocene, underwent peculiar morphological changes and also speciation. The large number of rodent genera coevolving in the Gargano Islands is indicative of the large surface areas of these islands. The general geographic pattern of southwestern Europe during the Neogene may therefore correspond to a large continental province including Spain and southern France with some kind of fast-modifying archipelago on its southern rim.     

The effects of taxonomic standardization on sampling-standardized estimates of historical diversity

Occurrence-based databases such as the Palaeobiology database (PBDB) provide means of accommodating the heterogeneities of the fossil record when evaluating historical diversity patterns. Although palaeontologists have given ample attention to the effects of taxonomic practice on diversity patterns derived from synoptic databases (those using first and last appearances of taxa), workers have not examined the effects of taxonomic error on occurrence-based diversity studies. Here, we contrast diversity patterns and diversity dynamics between raw data and taxonomically vetted data in the PBDB to evaluate the effects of taxonomic errors. We examine three groups: Palaeozoic gastropods, Jurassic bivalves and Cenozoic bivalves. We contrast genus-level diversity patterns based on: (i) all occurrences assigned to a genus (i.e. both species records and records identifying only the genus), (ii) only occurrences for which a species is identified, and (iii) only occurrences for which a species is identified, but after vetting the genus to which the species is assigned.Extensive generic reassignments elevate origination and extinction rates within Palaeozoic gastropods and origination rates within Cenozoic bivalves. However, vetting increases generic richness markedly only for Cenozoic bivalves, and even then the increase is less than 10%. Moreover, the patterns of standing generic richness are highly similar under all three data treatments. Unless our results are unusual, taxonomic standardization can elevate diversity dynamics in some cases, but it will not greatly change inferred richness over time.     

Evolutionary rates of the Triassic marine macrofauna and sea-level changes: Evidences from the Northwestern Caucasus,Northern Neotethys (Russia)

A diverse Triassic marine macrofauna from the Northwestern Caucasus sheds new light on the biotic evolution after the end-Permian mass extinction. In the early Mesozoic, the study area was located on the northern margin of the Neotethys Ocean. Data on stratigraphic ranges of 130 genera of brachiopods, bivalves, ammonoids, corals, and sponges have been used to calculate the changes in two evolutionary rates, namely faunal transformation rate (FTR) and rate of transformation of the taxonomic diversity structure (TTDSR). The FTR demonstrates the changes in the generic composition of assemblages through geologic time, whereas the TTDSR indicates changes in the generic control of the species diversity. The Triassic marine macrofauna of the Northwestern Caucasus was characterized by very high FTR and TTDSR during the Early Triassic through early Late Triassic. The FTR slowed in the Middle Triassic, and accelerated again in the Carnian–Norian. In contrast, the FTR was abnormally slow in the Norian–Rhaetian. A remarkable turnover among macrofauna occurred at the Carnian–Norian transition. Regional sea-level changes were similar to the global eustatic fluctuations. It is difficult to establish their direct connections with changes in the evolutionary rates, although the turnover at the Carnian–Norian boundary coincided with a prominent regressive episode. In general, high evolutionary rates reported for the Triassic marine macrofauna of the Northwestern Caucasus may be explained as a consequence of the devastating end-Permian mass extinction.     

Patterns and drivers of Nothobranchius killifish diversity in lowland Tanzania

Temporary pools are seasonal wetland habitats with specifically adapted biota, including annual Nothobranchius killifishes that survive habitat desiccation as diapausing eggs encased in dry sediment. To understand the patterns in the structure of Nothobranchius assemblages and their potential in wetland conservation, we compared biodiversity components (alpha, beta, and gamma) between regions and estimated the role and sources of nestedness and turnover on their diversity. We sampled Nothobranchius assemblages from 127 pools across seven local regions in lowland Eastern Tanzania over 2 years, using dip net and seine nets. We estimated species composition and richness for each pool, and beta and gamma diversity for each region. We decomposed beta diversity into nestedness and turnover components. We tested nestedness in three main regions (Ruvu, Rufiji, and Mbezi) using the number of decreasing fills metric and compared the roles of pool area, isolation, and altitude on nestedness. A total of 15 species formed assemblages containing 1–6 species. Most Nothobranchius species were endemic to one or two adjacent regions. Regional diversity was highest in the Ruvu, Rufiji, and Mbezi regions. Nestedness was significant in Ruvu and Rufiji, with shared core (N. melanospilus, N. eggersi, and N. janpapi) and common (N. ocellatus and N. annectens) species, and distinctive rare species. Nestedness apparently resulted from selective colonization rather than selective extinction, and local species richness was negatively associated with altitude. The Nothobranchius assemblages in the Mbezi region were not nested, and had many endemic species and the highest beta diversity driven by species turnover. Overall, we found unexpected local variation in the sources of beta diversity (nestedness and turnover) within the study area. The Mbezi region contained the highest diversity and many endemic species, apparently due to repeated colonizations of the region rather than local diversification. We suggest that annual killifish can serve as a flagship taxon for small wetland conservation.     

Genetic diversity in the mtDNA control region and population structure in the small yellow croaker <Emphasis Type="Italic">Larimichthys polyactis</Emphasis>

The genetic diversity and population genetic structure of the small yellow croaker (Larimichthys polyactis) were investigated. One hundred and fourteen individuals were sampled from 8 localities of the Yellow Sea and the northern East China Sea. Genetic variation in DNA sequences were examined from the first hypervariable region (HVR-1) of the mitochondrial DNA control region. High levels of haplotype diversity (h = 0.98 ± 0.87%) in the HVR-1 region were detected, indicating a high level of genetic diverstiy. A total of 84 polymorphic sites were found, and 87 haplotypes were defined. The pairwise nucleotide differences between samples ranged from 3.83 ± 2.19 to 6.56 ± 3.25. The demographic history of L. polyactis was examined by using neutrality tests and mismatch distribution analysis, which indicated a Pleistocene population expansion at about 49,300–197,000 years. The star burst structure of the minimum spanning tree also suggestted a very recent origin for most haplotypes. Hierarchical molecular variance analysis (AMOVA) and conventional population Fst comparisons revealed no significant genetic structure throughout the examined range, which is inconsistent with previous findings based on the morphological and ecological studies. Long-term dispersal and high gene flow likely have contributed to the genetically homogeneous population structure of the species. The knowledge on genetic diversity and genetic structure will be crucial to establish appropriate fishery management stocks for the species.