Fossilized bacteria in a Cretaceous pterosaur headcrest

Pinheiro F.L., Horn B.L.D., Schultz C.L., de Andrade J.A.F.G. and Sucerquia P.A., 2012: Fossilized bacteria in a Cretaceous pterosaur headcrest. Lethaia, Vol. 45, pp. 495–499. We report herein the first evidence of bacterial autolithification in the Crato Formation of Araripe Basin, Brazil. The fossilized bacteria are associated with a tapejarid pterosaur skull, replacing the soft‐tissue extension of the headcrest. EDS analyses indicate that the bacteria were replaced by phosphate minerals, probably apatite. The bacterial biofilm was likely part of the prokaryotic mat that decomposed the pterosaur carcass at the bottom of the Araripe lagoon. This work suggests that bacterial autolithification could have played a key‐role on soft‐tissue preservation of Crato Formation Lagerstätte. □Bacterial autolithification, Crato Formation, phosphatization, pterosaur, soft‐tissue preservation.     

Molecular phylogenetics of Alternanthera (Gomphrenoideae,Amaranthaceae): resolving a complex taxonomic history caused by different interpretations of morphological characters in a lineage with C4 and C3–C4 intermediate species

Alternanthera (Amaranthaceae) is a diverse genus (80–200 species) largely restricted to the American Tropics. With Pedersenia and Tidestromia, it makes up the ‘Alternantheroid clade’ in Gomphrenoideae. Parsimony and Bayesian analyses of nucleotide sequences of nuclear (ITS) and plastid (rpl16, trnL‐F) and morphological characters identify that the capitate stigma of Alternanthera is a synapomorpy within the Alternantheroids. Within Alternanthera, two major clades were resolved, both of which were marked by otherwise homoplasious characters of the gynoecium: Clade A [99% jackknife (JK); 1.0 posterior probability (PP)] with nine species and Clade B (60% JK; 0.98 PP) with 22 species. Four subclades (B1–B4), strongly supported statistically, were identified in Clade B. Previous subgeneric classifications of Alternanthera appear artificial in light of our new molecular phylogenetic analyses. Most major lineages are congruently resolved by nuclear and plastid data but some incongruence between the nrITS and plastid phylogenetic trees suggests hybridization may have played a role in the rampant speciation in Alternanthera. Whereas C₄ photosynthesis appears to have evolved in a single clade, the position of A. littoralis var. maritima (C₃) in this clade may be explained by hybrid speciation rather than a reversal from C₄ to C₃. All C₃–C₄ intermediates belong to a different clade that also contains C₃ species, but species limits, including the widely studied A. tenella, are unclear. The clade including A. tenella and A. halimifolia contains most of the species endemic to the Galápagos whereas A. nesiotes, also endemic to the islands, is nested among widespread American taxa. This suggests that the Galápagos radiation of Alternanthera may have arisen from at least two independent colonization events followed by a subsequent radiation in the former lineage. © 2012 The Linnean Society of London, Botanical Journal of the Linnean Society, 2012, 169 , 493–517.     

Population genetic structure of diploid sexual and polyploid apomictic hawthorns (Crataegus; Rosaceae) in the Pacific Northwest

Polyploidy and gametophytic apomixis are two important and associated processes in plants. Many hawthorn species are polyploids and can reproduce both sexually and apomictically. However, the population genetic structure of these species is poorly understood. Crataegus douglasii is represented exclusively by self-compatible tetraploid pseudogamous apomicts across North America, whereas Crataegus suksdorfii found in the Pacific Northwest is known to include self-incompatible diploid sexuals as well as polyploid apomicts. We compare population structure and genetic variability in these two closely related taxa using microsatellite and chloroplast sequence markers. Using 13 microsatellite loci located on four linkage groups, 251 alleles were detected in 239 individuals sampled from 15 localities. Within-population multilocus genotypic variation and molecular diversity are greatest in diploid sexuals and lowest in triploid apomicts. Apart from the isolation of eastern North American populations of C. douglasii , there is little evidence of isolation by distance in this taxon. Genetic diversity in western populations of C. douglasii suggests that gene flow is frequent, and that colonization and establishment are often successful. In contrast, local populations of C. suksdorfii are more markedly differentiated. Gene flow appears to be limited primarily by distance in diploids and by apomixis and self-compatibility in polyploids. We infer that apomixis and reproductive barriers between cytotypes are factors that reduce the frequency of gene flow among populations, and may ultimately lead to allopatric speciation in C. suksdorfii . Our findings shed light on evolution in woody plants that show heterogeneous ploidy levels and reproductive systems.     

Influence of typhoons on annual CO2 flux from a subtropical, humic lake

The Intergovernmental Panel on Climate Change predicts dramatic changes in precipitation patterns over the next century. One potential method for inferring how these changes in annual precipitation and intensity of storm events will influence aquatic ecosystems is to study and model present-day lakes that share climatic characteristics with future climate scenarios. A small lake in north-central Taiwan provided an excellent opportunity to explore the influence of intense meteorological events on CO₂ exchange between surface waters and the atmosphere. Each year Yuan Yang Lake (YYL) is influenced by multiple typhoons that pass near the island of Taiwan. This lake has been instrumented with a sensor network that monitors water column and meteorological parameters at a high temporal resolution (2–10 min intervals). Using this high-resolution data and manually collected CO₂ samples, a mass-balance model of CO₂ dynamics in YYL was developed. In addition, a generalized simulation model was used to explore how typhoon frequency, intensity, and timing impact CO₂ efflux to the atmosphere. Our findings suggest that increased annual precipitation and frequency of storm events results in greater epilimnetic interaction with the watershed and hypolimnion. These interactions resulted in elevated epilimetic CO₂ concentrations and therefore greater evasion of CO₂ to the atmosphere.     

Applying the light : nutrient hypothesis to stream periphyton

1. The light : nutrient hypothesis (LNH) states that algal nutrient content is determined by the balance of light and dissolved nutrients available to algae during growth. Light and phosphorus gradients in both laboratory and natural streams were used to examine the relevance of the LNH to stream periphyton. Controlled gradients of light (12–426 μmol photons m^?2 s^?1) and dissolved reactive phosphorus (DRP, 3–344 μg L^?1) were applied experimentally to large flow‐through laboratory streams, and natural variability in canopy cover and discharge from a wastewater treatment facility created gradients of light (0.4–35 mol photons m^?2 day^?1) and DRP (10–1766 μg L^?1) in a natural stream. 2. Periphyton phosphorus content was strongly influenced by the light and DRP gradients, ranging from 1.8 to 10.7 μg mg AFDM^?1 in the laboratory streams and from 2.3 to 36.9 μg mg AFDM^?1 in the natural stream. Phosphorus content decreased with increasing light and increased with increasing water column phosphorus. The simultaneous effects of light and phosphorus were consistent with the LNH that the balance between light and nutrients determines algal nutrient content. 3. In experiments in the laboratory streams, periphyton phosphorus increased hyperbolically with increasing DRP. Uptake then began levelling off around 50 μg L^?1. 4. The relationship between periphyton phosphorus and the light : phosphorus ratio was highly nonlinear in both the laboratory and natural streams, with phosphorus content declining sharply with initial increases in the light : phosphorus ratio, then leveling off at higher values of the ratio. 5. Although light and DRP both affected periphyton phosphorus content, the effects of DRP were much stronger than those of light in both the laboratory and natural streams. DRP explained substantially more of the overall variability in periphyton phosphorus than did light, and light effects were evident only at lower phosphorus concentrations (≤25 μg L^?1) in the laboratory streams. These results suggest that light has a significant negative effect on the food quality of grazers in streams only under a limited set of conditions.     

Phylogenetics and biogeography of the parasitic genus Thesium L. (Santalaceae), with an emphasis on the Cape of South Africa

Thesium is a large genus of parasitic shrubs belonging to tribe Thesieae of Santalaceae. It has a principally Old World distribution, with the greatest diversity being found in southern Africa. Little is known about the relationships within Thesium or its relationships with its closest relatives. In this article, we present a first estimate of species‐level phylogenetic relationships in Thesium based on internal transcribed spacer (ITS) and trnL–trnF sequence data, and use this to explore the biogeographical history of the group. One hundred and four samples representing 72 Thesium spp. were included in a phylogenetic analysis. Plastid and combined data resolve Thesium as paraphyletic relative to Thesidium and Austroamericium with high posterior probability and bootstrap support. ITS sequence data place Thesidium as sister to a large Thesium clade, but with weak support. Ancestral range reconstruction and dating analysis suggest a southern African origin for the group, with a crown age of 39.1 ± 11.9 Mya, followed by dispersal into Europe and South America. A large clade of Cape species split in the Miocene from a clade comprising tropical species (25.5 ± 7.3 Mya) with the diversification of extant species beginning at 16.7 ± 6.3 Mya. © 2010 The Linnean Society of London, Botanical Journal of the Linnean Society, 2010, 162 , 435–452.     

Sea‐level changes and palaeo‐ranges: reconstruction of ancient shorelines and river drainages and the phylogeography of the Australian land crayfish Engaeus sericatus Clark (Decapoda: Parastacidae)

Historical sea levels have been influential in shaping the phylogeography of freshwater‐limited taxa via palaeodrainage and palaeoshoreline connections. In this study, we demonstrate an approach to phylogeographic analysis incorporating historical sea‐level information in a nested clade phylogeographic analysis (NCPA) framework, using burrowing freshwater crayfish as the model organism. Our study area focuses on the Bass Strait region of southeastern Australia, which is marine region encompassing a shallow seabed that has emerged as a land bridge during glacial cycles connecting mainland Australia and Tasmania. Bathymetric data were analysed using Geographical Information Systems (GIS) to delineate a palaeodrainage model when the palaeocoastline was 150 m below present‐day sea level. Such sea levels occurred at least twice in the past 500 000 years, perhaps more often or of larger magnitude within the last 10 million years, linking Victoria and Tasmania. Inter‐locality distance measures confined to the palaeodrainage network were incorporated into an NCPA of crayfish (Engaeus sericatus Clark 1936) mitochondrial 16S rDNA haplotypes. The results were then compared to NCPAs using present‐day river drainages and traditional great‐circle distance measures. NCPA inferences were cross‐examined using frequentist and Bayesian procedures in the context of geomorphological and historical sea‐level data. We found distribution of present‐day genetic variation in E. sericatus to be partly explained not only by connectivity through palaeodrainages but also via present‐day drainages or overland (great circle) routes. We recommend that future studies consider all three of these distance measures, especially for studies of coastally distributed species.     

Breeding ecology of the Sulawesi Red-Knobbed Hornbill Aceros cassidix

Data are presented for a four-year study of the breeding biology of the Sulawesi Red-knobbed Hornbill Aceros cassidix. The breeding season normally began in mid-June and lasted 27–30 weeks. Initiation of nesting appeared to be stimulated by the cessation of the rains and timed such that chicks emerged during a period of fruit abundance. Nesting period averaged 139 days and incubation was estimated at 35–40 days. Females remain sealed in the nest for an average of 108 days and nestlings fledged, on average, 28 davs after the female emerged. Nesting densities were up to 10.4/km², nesting success was high (up to 80%) and repeated use of nests between years was common. Males delivered a low-protein diet of ripe fruits (89% of total diet) from 12 families and 52 species; invertebrates composed only 1% of food items. Figs ( Ficus spp.) were the primary diet item, accounting for 81% of fruit biomass. Males increased feeding visits throughout the study, but the biomass of fruit delivered declined shortly after the female emerged. Reduced feeding prior to fledging may entice the nestling to emerge. The long developmental period of Sulawesi Red-knobbed Hornbills may result, in part, from the low protein content of the diet. Despite a 16% annual production, numbers in the study area have remained stable over the past 15 years. It is suggested that high post-fledging mortality or dispersal to degraded areas outside the reserve maintains population numbers. Distinguishing between these mechanisms is important for understanding the dynamics of hornbill populations.     

Snow depth, soil freezing, and fluxes of carbon dioxide, nitrous oxide and methane in a northern hardwood forest

Soil–atmosphere fluxes of trace gases (especially nitrous oxide (N₂O)) can be significant during winter and at snowmelt. We investigated the effects of decreases in snow cover on soil freezing and trace gas fluxes at the Hubbard Brook Experimental Forest, a northern hardwood forest in New Hampshire, USA. We manipulated snow depth by shoveling to induce soil freezing, and measured fluxes of N₂O, methane (CH₄) and carbon dioxide (CO₂) in field chambers monthly (bi-weekly at snowmelt) in stands dominated by sugar maple or yellow birch. The snow manipulation and measurements were carried out in two winters (1997/1998 and 1998/1999) and measurements continued through 2000. Fluxes of CO₂ and CH₄ showed a strong seasonal pattern, with low rates in winter, but N₂O fluxes did not show strong seasonal variation. The snow manipulation induced soil freezing, increased N₂O flux and decreased CH₄ uptake in both treatment years, especially during winter. Annual N₂O fluxes in sugar maple treatment plots were 207 and 99 mg N m⁻² yr⁻¹ in 1998 and 1999 vs. 105 and 42 in reference plots. Tree species had no effect on N₂O or CO₂ fluxes, but CH₄ uptake was higher in plots dominated by yellow birch than in plots dominated by sugar maple. Our results suggest that winter fluxes of N₂O are important and that winter climate change that decreases snow cover will increase soil:atmosphere N₂O fluxes from northern hardwood forests.