High-resolution sequence stratigraphy of a mixed carbonate-siliciclastic, cratonic ramp (Upper Ordovician; Kentucky–Ohio, USA): insights into the relative influence of eustasy and tectonics through analysis of facies gradients

Detailed facies analysis and event stratigraphy of an Upper Ordovician (Rocklandian–Edenian) cratonic ramp succession in eastern North America yields insights into eustatically driven sequence architecture and localized tectonic instability. Seven, predominantly subtidal, mixed carbonate-siliciclastic depositional sequences (3rd order) are identified and correlated across the length of a 275-km ramp–to–basin profile. Within the larger depositional sequences (3rd order) at least two smaller orders (4th and 5th) of cyclicity are recognizable. Three systems tracts occur within each sequence (transgressive, TST; highstand, HST; regressive, RST) and are considered in terms of their component parasequences (5th order). Generally, TSTs are composed of skeletal grainstone–rudstone facies, HSTs are dominated by shaly nodular wacke-packstone facies, and RSTs are mostly calcarenite facies. Systems tracts, sequence boundaries and their correlative conformities, maximum flooding surfaces, and forced regression surfaces were traced from shallow shelf to basinal settings. This high-resolution framework also provides insight into the timing of tectonic fluctuations on this cratonic ramp during the Taconic Orogeny and documents the relative influence of tectonism on lateral facies distributions and eustatically derived cyclicity.     

Modern tropical analogs for Carboniferous standing forests: Comparison of extinct Mesocalamites with extant Montrichardia

Assemblages of in situ upright stem casts, or fossil standing forests, provide information on the composition and spatial arrangement of the original plant communities they record, with minimal taphonomic bias. Stands of calamites and lycopsids are found repeatedly as fossil forests in the Late Carboniferous, while other major groups of plants are only rarely preserved in this way. The Carboniferous coal measures of Europe and North America were formed in low‐latitude, tropical environments. The ancient plant communities of these settings can be interpreted by comparison of their taxa with specific, modern tropical analogs. Here, ancient standing forests of the extinct sphenopsid Mesocalamites suckowii are compared with modern stands of the monocot Montrichardia arborescens. These modern analogs occur in the Orinoco Delta of Venezuela and the mouth of the Amazon. Montrichardia and its ancient counterparts occur in comparable clastic facies of fluvio‐deltaic and estuarine depositional systems. Although Mesocalamites and Montrichardia are very different anatomically and taxonomically, they exhibit some intriguing morphological similarities that can be linked to a common ecology. These modern and ancient taxa have evolved convergent forms of vegetative propagation that enable the plants to colonize and survive in environments characterized by very high rates of sedimentation, or episodic sedimentation events. Such environments have an unusually high potential to preserve standing forests.     

Facies,depositional sequences,and biostratigraphy of the Oligo-Miocene Asmari Formation in Marun oilfield,North Dezful Embayment,Zagros Basin,SW Iran

The Asmari Formation in Marun oilfield (south-west Iran), is about 440 m-thick marine carbonate succession with subordinate siliciclastic rocks, characterized by abundant benthic foraminifera (perforate and imperforate). Foraminiferal biostratigraphy indicates that this unit is Oligocene–Miocene in age. The distribution of benthic foraminifera and other components have led to the recognition of three siliciclastic and ten carbonate facies that were deposited in inner ramp (shoreline, tidal flat, restricted and open lagoon and shoal), middle and outer ramp sub-environments. Based on vertical facies trends, three third-order sequences in the Oligocene and three third-order sequences in the Miocene sediments have been identified. These depositional sequences are bounded by both type 1 and type 2 sequence boundaries. The transgressive systems tracts (TST) of sequences show deepening-upward facies trend with a gradual upward increase in perforate foraminifera, whereas the highstand systems tracts (HST) have a shallowing-upward facies trend and contain predominantly imperforate foraminifera. Deposition of these depositional sequences (DS) were controlled by both eustasy and tectonic subsidence.     

Ecosystem engineering by a canopy‐forming kelp facilitates the recruitment of native oysters

Ecosystem engineers are species that influence the abiotic and biotic environment around them and may assist the restoration of associated species, including other habitat‐forming species. We deployed an array of 28 artificial reefs with transplanted Ecklonia radiata, the dominant canopy‐forming kelp species across southern Australia, to investigate how the patch size and density of E. radiata influenced the establishment of the associated communities of plants and animals. Many of the reefs were rapidly colonized by Ostrea angasi, a critically depleted reef‐forming oyster. Over the 24‐month deployment of the reefs, thick oyster mats formed across the entire surface of many of the reefs with estimated biomass densities exceeding 5 kg of live oysters/m²; however, oyster density was dependent on E. radiata patch size and density. Increasing patch size and the presence of kelp resulted in significantly higher densities of oysters 5 months after the reefs were deployed and at the end of the experiment, where oysters were approximately three times more numerous on reefs with kelp compared to those without kelp. E. radiata appeared to facilitate the establishment of O. angasi largely through its capacity to reduce benthic light and thus suppress competition from turfing algae. These results may inform the development of novel approaches to tackle recruitment bottlenecks affecting the restoration of O. angasi reefs.     

Sequence stratigraphy of the Early–Middle Devonian succession (Padeha Formation) in Tabas Block,East-Central Iran: Implication for mixed tidal flat deposits

The facies and sequence stratigraphic analyses of the Padeha Formation (Early–Middle Devonian) in the East-Central Iran are based on two measured stratigraphic sections in the Ozbak-Kuh (type section) and Deranjal (Dahaneh-Kalot section) Mountains in the northern Tabas Block, with a thickness of 492 and 320 m respectively. The field observations and laboratory studies were used to identify sixteen lithofacies and four architectural elements. The facies associations were classified into five categories including sandstone (St, Sp, Sr, Sh, Sl), fine grained (siltstone–claystone) or mud rock (Fl), interbedded sandstone–mud rock (Sr(Fl), Sr/Fl, Fl(Sr)), dolomite (Dl and Ds), and evaporate (El, Efl, Efm, Edl). Structural (wave and interference ripples, planar cross-bedding and herringbone, flaser-wavy and lenticular beddings, tepee and stromatolite structures, entrolothic foldings, shrinkage and syneresis cracks, rain drop imprints, and salt casts) and textural (mature–supermature quartzarenite) features, as well as predominant bimodal pattern of paleocurrents in most lithofacies, show that sediments of the Padeha Formation have been deposited in a tidal flat environment. The sandstone, interbedded sandstone–mud rock, and dolomite facies (SB and LA architectural elements) are related to subtidal and intertidal settings, and fine-grained sediments and evaporate facies (consisting of FF and E architectural elements) were deposited in the supratidal and sabkha settings. Detail sequence stratigraphic study led to identification of two 3rd order complete depositional sequences (DS₂ and DS₃) with SB₁ sequence boundaries and two incomplete sequences (DS₁ and DS₄). Supratidal and sabkha facies were formed during the fall of relative sea level and are related to the lowstand systems tract (LST). The intertidal facies were formed at a rise of relative sea level and are interpreted as transgressive (TST) and highstand (HST) systems tracts.     

Facies of a Lower Ordovician carbonate shelf (Mungok Formation: Taebaeksan Basin,Korea)

Summary The lithologic associations within the Lower Ordovician Mungok Formation in Korea define four depositional facies that formed across a continental margin fringing the Sino-Korean block: these facies represent lagoonal/restricted marine, shoal, inner shelf, and outer shelf environments. The stacking pattern of these facies reveals two systems tracts composed of five depositional sequences. The lower highstand systems tract consists of the lagoonal/restricted marine and shoal facies, whereas the upper lowstand systems tract comprises, in ascending order, inner shelf, outer shelf, and inner shelf facies. Three trilobite biofacies are recognized in the Mungok Formation: i.e.,Yosimuraspis, Kainella, andShumardia biofacies in ascending order. TheYosimuraspis Biofacies is dominated byYosimuraspis but also containsJujuyaspis andElkanaspis. The predominance of the endemic eponymous taxon suggests a lagoonal/restricted marine environment. The nearly monotaxicKainella Biofacies, which comprises pandemic genera such asKainella and occasionallyLeiostegium, may represent a less restricted environment than theYosimuraspis Biofacies. TheShumardia Biofacies occurs in the marlstone/shale lithofacies through relatively thick stratigraphic interval and is dominated by cosmopolitan trilobite taxa with some endemic species. The lithofacies and cosmopolitan trilobite assemblage of theShumardia Biofacies indicate that it occupied an outer shelf environment. The vertical succession of lithofacies and trilobite biofacies in the Mungok Formation records in general a shift from a restricted, shallow water environment to deeper-water environment.     

Changhsingian brachiopod communities along a marine depth gradient in South China and their ecological significance in the end-Permian mass extinction

Diversity indices (dominance and evenness) and ecological spatial structure (lifestyles and relative abundances) are important features of Changhsingian brachiopod communities prior to the end-Permian mass extinction (EPME) and could predict temporal and spatial extinction patterns during the EPME. In South China, Changhsingian brachiopod communities show higher diversity than other contemporaneous brachiopod communities in the world and have been reported from a variety of sedimentary environments. In this paper, brachiopods from 18 sections in South China were selected to divide communities and compare their ecological structure. Based on the results of network analysis, cluster analysis and quantitative data from the selected sections, we show that Changhsingian brachiopod communities in South China can be categorized into three assemblages along a marine depth gradient: the Neochonetes–Fusichonetes–Paryphella Assemblage from the shallow-water clastic-rock facies, Spinomarginifera–Peltichia–Oldhamina Assemblage from the shallow-water carbonate platform facies and Fusichonetes–Crurithyris Assemblage from the deep-water siliciclastic intracontinental basin facies. Compared with communities from carbonate platform facies, the communities from siliciclastic facies were characterized by high dominance, low evenness and low lifestyle diversity, which might be important biotic factors leading to earlier extinctions. After the extinction began in all environments, the whole earliest Triassic brachiopod community was first dominated by Fusichonetes and then by Crurithyris. These patterns of domination and replacement could be explained by morphological and ecological advantages. The domination of these two genera, which were already adapted to the oxygen and food-limited deep-water habitat, indicates that the cooler deep-water environment might have been a relatively less stressed habitat after the beginning of the EPME. This suggests that global warming might be the main trigger among the previously proposed synergistic environmental stresses, while anoxia might not, at least for the beginning of EPME.     

Large forests enhance songbird nesting success in agricultural‐ dominated landscapes of the Midwestern US

We studied the effects of habitat composition and distance from edges on nesting success and brood parasitism of forest birds in the Kaskaskia River Bottoms, one of the largest remaining tracts of floodplain forest in the agricultural Midwestern United States. Our goal was to help the private landowners, who have maintained this region in forest cover, enhance the value of these forests for nesting birds. We measured nest predation rates and levels of brood parasitism of four species, the indigo bunting Passerina cyanea, Acadian flycatcher Empidonax virescens, northern cardinal Cardinalis cardinalis and prothonotary warbler Protonotaria citrea in relation to distances from natural and anthropogenic edges and proportion of natural and anthropogenic habitats within fixed radii around nests. We predicted that nesting success would increase with increasing distance from anthropogenic habitats and with increasing land cover in natural habitats. Our results showed no strong effect of any of these variables on avian nesting success, although parasitism levels increased slightly with increasing proportion of agricultural land around nests for two of the species. Nevertheless, nesting success for at least three of these species was much higher than in more fragmented forest tracts elsewhere in the agricultural Midwest where most forest tracts appear to be population sinks for most species. These results suggest that forest tracts in the Kaskaskia may be saturated with nest predators and brood parasites, but are not super‐saturated in a way that would cause these tracts to become ‘black hole’ population sinks. Our data further suggest that, as long as landowners maintain their private landholdings in forest cover, the details of how they manage their land may have little effect on songbird nesting success. These results also suggest that reforestation efforts in areas with many openings may still benefit forest birds.     

Trilobite biofacies and sequence stratigraphy: an example from the Upper Ordovician of Oklahoma

There have been surprisingly few empirical investigations of the fundamental principle that the architecture of depositional sequences exerts considerable control on observed patterns of faunal distribution and replacement. In this paper, we examine trilobite associations in two sequences of the Upper Ordovician (Sandbian) Bromide Formation of southern Oklahoma. Cluster analysis and ordination of genus abundance data identified five lithofacies‐related biofacies that are also differentiated by diversity patterns. Biofacies of the transgressive system tract (TST) of successive sequences are more similar to each other than they are to biofacies in the highstand systems tract (HST) of the same sequence. This similarity likely records dominance of large, robust convex sclerites in taphonomically degraded samples from condensed, strongly winnowed grainstone and rudstone. Horizons with articulated exoskeletons of isoteline trilobites preserved by obrution deposits occur most commonly in the early HST and record behavioural aggregations. Grainstone and rudstone of the later HST are less winnowed than those of the TST and show less fragmentation and sorting of sclerites. These changes in taphonomic conditions preserve ecological patterns more clearly. In most biofacies, rarefied alpha diversity (samples) and gamma diversity (biofacies) of middle‐ and outer‐ramp HST deposits are greater than in the TSTs, and biofacies replace each other down ramp. Diversity patterns do not agree with model predictions and other data sets that indicate low beta and high alpha diversity in the TST, likely because of taphonomic degradation. Vertical replacement of biofacies is expressed by the appearance of peritidal facies in which trilobites are rare. Biofacies shifts also characterize sequence boundaries and are most profound in the inner‐ramp successions characterized by sharp facies offsets. Comparison with bathymetrically similar deposits in the Taconic foreland basin showed similar diversity trends along environmental gradients, with some differences in shallow‐water settings attributed to taphonomic differences.     

Higher contribution of globally rare bacterial taxa reflects environmental transitions across the surface ocean

Microbial taxa range from being ubiquitous and abundant across space to extremely rare and endemic, depending on their ecophysiology and on different processes acting locally or regionally. However, little is known about how cosmopolitan or rare taxa combine to constitute communities and whether environmental variations promote changes in their relative abundances. Here we identified the Spatial Abundance Distribution (SpAD) of individual prokaryotic taxa (16S rDNA‐defined Operational Taxonomic Units, OTUs) across 108 globally‐distributed surface ocean stations. We grouped taxa based on their SpAD shape (“normal‐like”‐ abundant and ubiquitous; “logistic”‐ globally rare, present in few sites; and “bimodal”‐ abundant only in certain oceanic regions), and investigated how the abundance of these three categories relates to environmental gradients. Most surface assemblages were numerically dominated by a few cosmopolitan “normal‐like” OTUs, yet there was a gradual shift towards assemblages dominated by “logistic” taxa in specific areas with productivity and temperature differing the most from the average conditions in the sampled stations. When we performed the SpAD categorization including additional habitats (deeper layers and particles of varying sizes), the SpAD of many OTUs changed towards fewer “normal‐like” shapes, and OTUs categorized as globally rare in the surface ocean became abundant. This suggests that understanding the mechanisms behind microbial rarity and dominance requires expanding the context of study beyond local communities and single habitats. We show that marine bacterial communities comprise taxa displaying a continuum of SpADs, and that variations in their abundances can be linked to habitat transitions or barriers that delimit the distribution of community members.     

Applications of nummulitids and other larger benthic foraminifera in depositional environment and sequence stratigraphy: an example from the Eocene deposits in Zagros Basin,SW Iran

The Tale-Zang Formation in Zagros Mountains (south-west Iran) is a Lower to Middle Eocene carbonate sequence. Carbonate sequences of the Tale-Zang Formation consist mainly of large benthic foraminifera (e.g. Nummulites and Alveolina), along with other skeletal and non-skeletal components. Water depth during deposition of the formation was determined based on the variation and types of benthic foraminifera, and other components in different facies. Microfacies analysis led to the recognition of ten microfacies that are related to four facies belts such as tidal flat, lagoon, shoal and open marine. An absence of turbidite deposits, reefal facies, gradual facies changes and widespread tidal flat deposits indicate that the Tale-Zang Formation was deposited in a carbonate ramp environment. Due to the great diversity and abundance of larger benthic foraminifera, this carbonate ramp is referred to as a “foraminifera-dominated carbonate ramp system”. Based on the field observations, microfacies analysis and sequence stratigraphic studies, three third-order sequences in the Langar type section and one third-order sequence in the Kialo section were identified. These depositional sequences have been separated by both type-1 and type-2 sequence boundaries. The transgressive systems tracts of sequences show a gradual upward increase in perforate foraminifera, whereas the highstand systems tracts of sequences contain predominantly imperforate foraminifera.     

Power law relationships among hierarchical taxonomic categories in algae reveal a new paradox of the plankton

Aim In this continental‐scale study, the biodiversity of benthic and planktonic algal communities was explored. A recent analysis of extinct and extant tree communities by Enquist et al. (2002) showed that richness of higher taxa was a power function of species richness, invariant across temporal and spatial scales. Here we examined whether the relationships between algal richness at hierarchical taxonomic levels conform to power laws as seen for trees, and if these relationships differ between benthic and planktonic habitats. Location Streams from more than 50 major watersheds in the United States. Method A total of 3698 samples were collected from 1277 locations by the National Water‐Quality Assessment Program. Three types of stream habitat were sampled: richest targeted habitats, depositional targeted habitats, and phytoplankton. The relationships between taxonomic richness at the species level vs. all higher categories from genus to phylum across the three habitats were examined by ordinary least squares (OLS) regressions after ln‐transformation of all variables. The slopes, b, of these regressions represent the exponents of the power functions that scaled the richness of higher taxonomic levels (T) to species richness (S) in the form: T∝S^b. Results Algal richness at hierarchical taxonomic categories (genus to phylum) is a power function of species richness. The scaling exponent of this function, which captures the diversification of higher taxa, i.e. the rate of increase of their richness with the increase of species richness, is significantly different across environments. Main conclusions The differential algal diversification in the three studied habitats emphasizes the fundamental role of the environment in structuring the communities of simple organisms such as algae. The finding that the diversification of higher taxa is greater in the seemingly homogeneous planktonic environment, when compared to benthic habitats, encompassing an array of ecological niches, poses a new paradox of the plankton.     

Bacterial Communities Associated with the Digestive Tract of the Predatory Ground Beetle, <Emphasis Type="Italic">Poecilus chalcites,</Emphasis> and Their Modification by Laboratory Rearing and Antibiotic Treatment

Ground beetles such as Poecilus chalcites (Coleoptera: Carabidae) are beneficial insects in agricultural systems where they contribute to the control of insect and weed pests. We assessed the complexity of bacterial communities occurring in the digestive tracts of field-collected P. chalcites using terminal restriction fragment length polymorphism analyses of polymerase chain reaction-amplified 16S rRNA genes. Bacterial identification was performed by the construction of 16S rRNA gene clone libraries and sequence analysis. Intestinal bacteria in field-collected beetles were then compared to those from groups of beetles that were reared in the lab on an artificial diet with and without antibiotics. Direct cell counts estimated 1.5 × 10⁸ bacteria per milliliter of gut. The digestive tract of field-collected P. chalcites produced an average of 4.8 terminal restriction fragments (tRF) for each beetle. The most abundant clones were affiliated with the genus Lactobacillus, followed by the taxa Enterobacteriaceae, Clostridia, and Bacteriodetes. The majority of the sequences recovered were closely related to those reported from other insect gastrointestinal tracts. Lab-reared beetles produced fewer tRF, an average of 3.1 per beetle, and a reduced number of taxa with a higher number of clones from the family Enterobacteriaceae compared to the field-collected beetles. Antibiotic treatment significantly (p < 0.05) reduced the number of tRF per beetle and selected for a less diverse set of bacterial taxa. We conclude that the digestive tract of P. chalcites is colonized by a simple community of bacteria that possess autochthonous characteristics. Laboratory-reared beetles harbored the most common bacteria found in field-collected beetles, and these bacterial communities may be manipulated in the laboratory with the addition of antibiotics to the diet to allow study of functional roles.     

Incest versus abstinence: reproductive trade‐offs between mate limitation and progeny fitness in a self‐incompatible invasive plant

Plant mating systems represent an evolutionary and ecological trade‐off between reproductive assurance through selfing and maximizing progeny fitness through outbreeding. However, many plants with sporophytic self‐incompatibility systems exhibit dominance interactions at the S‐locus that allow biparental inbreeding, thereby facilitating mating between individuals that share alleles at the S‐locus. We investigated this trade‐off by estimating mate availability and biparental inbreeding depression in wild radish from five different populations across Australia. We found dominance interactions among S‐alleles increased mate availability relative to estimates based on individuals that did not share S‐alleles. Twelve of the sixteen fitness variables were significantly reduced by inbreeding. For all the three life‐history phases evaluated, self‐fertilized offspring suffered a greater than 50% reduction in fitness, while full‐sib and half‐sib offspring suffered a less than 50% reduction in fitness. Theory indicates that fitness costs greater than 50% can result in an evolutionary trajectory toward a stable state of self‐incompatibility (SI). This study suggests that dominance interactions at the S‐locus provide a possible third stable state between SI and SC where biparental inbreeding increases mate availability with relatively minor fitness costs. This strategy allows weeds to establish in new environments while maintaining a functional SI system.     

Gut region induces gastrointestinal microbiota community shift in Ujimqin sheep (Ovis aries): from a multi-domain perspective

Gastrointestinal (GI) microbiota is one of the most complicated microbial ecosystems and is vital in regulating biological processes associated with nutrient absorption and homeostatic maintenance. Although several efforts have been achieved in characterizing bacterial communities across gut regions, the variation of non-bacterial communities across GI tracts is still largely unexplored. To address this, we investigated microbial biogeography throughout the whole GI tracts of Ujimqin sheep (Ovis aries) by amplicon sequencing which targeted bacteria, fungi, and archaea. The results indicated that the community structures of all three domains were significantly distinguished according to GI tracts (stomach, small intestine, and large intestine), and a more strong and efficient species interaction was detected in small intestine based on cross-domain network analysis. Moreover, a between-domain difference in microbial assembly mechanism of among-GI regions was revealed here, wherein bacterial community is dominantly governed by variable selection (explaining ~62% of taxa turnover), while fungal and archaeal communities mainly governed by homogenizing dispersal (explaining ~49% and 60% of the turnover, respectively). Overall, these data highlight the GI section- and domain-dependence of GI microbial structure and assembly mechanism, suggesting that multi-domain should be explicitly considered when evaluating the influences of GI selection on gut microbial communities.     

Response of nematode communities after large‐scale ice‐shelf collapse events in the Antarctic Larsen area

Owing to large‐scale ice‐shelf disintegration events, the Antarctic Larsen A and B areas recently became ice‐free. During the ANT‐XXIII/8 Polarstern campaign, this region was sampled for the first time. Our study is the first to investigate benthic communities in this area and their response to the collapse of ice shelves in the Antarctic. The nematofauna appears to be strongly influenced by the sudden ice‐cover removal, although its response differs from that of the macro‐ and megabenthos. Our results indicate that precollapse, sub‐ice communities were impoverished and characterized by low densities, low diversity and high dominance of a few taxa. This might still be visible at a station located deep inside the Larsen B embayment, where Halomonhystera was dominant. Post‐collapse recolonization of the ‘inner’ stations, i.e. those located furthermost from the former ice‐shelf edge, is believed to be a long‐time process. At the time of sampling, community structure at the inner stations was not or only slightly influenced by colonization, and might be structured by local environmental conditions. Our results indicate that a locally increased food supply after ice‐cover removal could provoke a faster, local response of the nematode assemblages compared with the response due to recolonization. Thalassomonhystera is recognized as an opportunist, taking advantage of increased food supply at inner stations A_South and B_North. Communities living close to the former ice‐shelf edge are believed to be at an intermediate or late stage of succession, with a dominance of Microlaimus, a common Antarctic genus and quick colonizer. Densities here were comparable with those at other Antarctic stations, whereas they were considerably decreased at the inner stations. In general, the collapse of the Larsen ice shelves initially has a positive effect on the shelf nematode fauna in the area, both in terms of abundance and diversity.     

The gut microbiome and metabolome of saddleback tamarins (Leontocebus weddelli): Insights into the foraging ecology of a small‐bodied primate

Body mass is a strong predictor of diet and nutritional requirements across a wide range of mammalian taxa. In the case of small‐bodied primates, because of their limited gut volume, rapid food passage rate, and high metabolic rate, they are hypothesized to maintain high digestive efficiency by exploiting foods rich in protein, fats, and readily available energy. However, our understanding of the dietary requirements of wild primates is limited because little is known concerning the contributions of their gut microbiome to the breakdown and assimilation of macronutrients and energy. To study how the gut microbiome contributes to the feeding ecology of a small‐bodied primate, we analyzed the fecal microbiome composition and metabolome of 22 wild saddleback tamarins (adult body mass 360–390 g) in Northern Bolivia. Samples were analyzed using high‐throughput Illumina sequencing of the 16 S rRNA gene V3‐V5 regions, coupled with GC‐MS metabolomic profiling. Our analysis revealed that the distal microbiome of Leontocebus weddelli is largely dominated by two main bacterial genera: Xylanibacter and Hallella (34.7 ± 14.7 and 22.6 ± 12.4%, respectively). A predictive analysis of functions likely carried out by bacteria in the tamarin gut demonstrated the dominance of membrane transport systems and carbohydrate metabolism as the predominant metabolic pathways. Moreover, given a fecal metabolome composed mainly of glucose, fructose, and lactic acid (21.7 ± 15.9%, 16.5 ± 10.7%, and 6.8 ± 5.5%, respectively), the processing of highly fermentable carbohydrates appears to play a central role in the nutritional ecology of these small‐bodied primates. Finally, the results also show a potential influence of environmentally‐derived bacteria in colonizing the tamarin gut. These results indicate high energetic turnover in the distal gut of Weddell's saddleback tamarin, likely influenced by dominant bacterial taxa that facilitate dietary dependence on highly digestible carbohydrates present in nectar, plant exudates, and ripe fruits.     

Does desertification diminish biodiversity? Enhancement of ant diversity by shrub invasion in south‐western USA

The conversion of desert grasslands to shrublands is a long‐standing concern in the south‐western United States, but the effects of this change on native animals defy generalization. Here, I consider evidence that shrub invasion and encroachment, particularly that of honey mesquite (Prosopis glandulosa), has led to increasing ecological dominance and diversity of ants in general, as well as increases in specific native taxa. The effects of shrub invasion on ants were measured at two scales: (1) between Chihuahuan Desert landscapes that vary slightly in temperature and strongly in the dominance of mesquite, and (2) across variation in mesquite density occurring within a generally mesquite‐dominated landscape. Ant richness and numerical dominance was measured at pitfall traps over 2 years and baits were used to assess ecological dominance across different temperatures. The mesquite‐dominated Jornada site harboured four times the number of ant foragers found at the relatively ‘pristine’ Sevilleta site, with several ecologically dominant taxa driving this pattern, especially Dorymyrmex bicolor. Species richness and ecological dominance were also greatest at the Jornada. Within the Jornada landscape, turnover in species composition was related to mesquite density, but local richness and abundance was unrelated to mesquite density. Coupled with the results of previous manipulative experiments and comparative studies, there is support for the notion that ant diversity is not negatively affected by shrub invasion but that several taxa prosper from it. The Jornada is uniquely saturated by dominant ant taxa, perhaps as a consequence of an overall high level of shrub availability that provides a reliable source of carbohydrate‐rich plant exudates. This raises important questions about the relationship between environmental degradation, ecosystem productivity, and animal diversity.     

Patterns of sclerobiont colonization on the rugose coral Schlotheimophyllum patellatum (Schlotheim, 1820) from the Silurian of Gotland,Sweden

Analysis of mushroom-shaped rugose corals Schlotheimophyllum patellatum (Schlotheim, 1820) from the Silurian (Upper Visby Beds, Lower Wenlock, Sheinwoodian) of Gotland, Sweden, showed that they were colonized on both the upper (exposed) and lower (cryptic) sides by a variety of encrusting and boring (sclerobiont) biotas, represented by 10 taxa and at least 23 species. Bryozoans and microconchid tubeworms, the most abundant encrusters, dominated on the cryptic undersides of the corals, while the dominant endobionts responsible for Trypanites borings overwhelmingly dominated the exposed surfaces. Except for cnidarian sphenothallids, which were exclusive colonizers of the underside of only one coral host, no other encrusters could be referred to as obligate cryptobionts. Because the upper surface of these corals was likely covered by soft-tissues during life, in specimens lifted off the sea-floor sclerobionts must have settled on the cryptic sides first. They could colonize the upper side only after the coral’s death, unless it was covered by sediment as could be the case in some flat specimens. With time, the space on the underside of the coral skeleton may have progressively been filled by sediment as well, precluding further colonization by sclerobionts. In that respect, the colonization patterns of these corals by encrusters and borers were controlled by the complex interplay of environmental factors, sclerobiont dynamics and coral growth in a given Silurian habitat. Compared with Silurian stromatoporoid hosts, the sclerobiont diversity and abundance noted on the Schlotheimophyllum corals may be regarded as representative for the Silurian as a whole.