Effect of biological soil crusts on soil elemental concentrations: implications for biogeochemistry and as traceable biosignatures of ancient life on land

Biological soil crusts (BSCs) are topsoil biosedimentary structures built by photosynthetic microbes commonly found today on arid soils. They play a role in soil stabilization and the fertility of arid lands, and are considered modern analogues of ancient terrestrial microbial communities. We determined the concentrations of four biogenic and 21 other elements, mostly metals, in surface soils that hosted BSCs, in the soils underneath those crusts, and in proximate but non-crusted surface soils. The samples were from six sites in the Colorado Plateau highlands and the Sonoran Desert lowlands. In spite of the variability in climate and geologic setting, we found statistically significant overall trends of enrichment in biogenic elements and depletion in non-biogenic elements when BSCs were compared with non-crusted soils. The differences between crusted and non-crusted soils were statistically significant at ∼95% confidence for C, N (enrichments) and for Ca, Cr, Mn, Cu, Zn, As, and Zr (depletions). These trends are best explained by the activity of microbes. As expected, no differences in the concentrations of C, N, P, and S were detected between the soils underneath the crusts and the non-crusted soils, but the former showed depletion of non-biogenic elements, indicating that the leaching effect of crust microbes extends downward in the soil. These patterns speak to the need for a sustained input of allochthonous material, possibly dust, to maintain BSC fertility. These elemental patterns can be considered a biosignature that may be preserved in the rock record and might help identify ancient microbial communities on land.     

Predicting spring oviposition by raspberry cane midge from accumulated derived soil temperatures

An accumulated soil temperature model is described which calculates the first oviposition date for overwintered populations of the raspberry cane midge (Resseliella theobaldi). The model uses values for mean 10 cm soil temperature, derived from daily maximum and minimum air temperatures and 10 cm soil temperature at 0900 GMT. It was developed by minimising the variation between observed dates for the start of oviposition over an 8-yr period and accumulated air or soil temperature, using a series of base temperatures. The best fit was obtained with soil temperatures accumulated above a base temperature of 4°C. Oviposition was predicted to start when the daily accumulated soil temperature reached 339°C days above a base temperature of 4°C. Field observations and model predictions suggested that emergence and oviposition dates were influenced by the direction of the slope of raspberry plantations. To compensate for this, an empirical correction has been incorporated into the model to advance or retard the predicted oviposition date by adjusting the estimated maximum soil temperature to allow for aspect. The geographical variation between dates for first oviposition was simulated by running the model for nine meteorological sites in the UK in 1985 and 1986.     

The Control of Inter-pollination between Sweet and Flint Corn

The breeding system of sweet corn, a sugary seeded race of Zeamays L., was studied by randomly planting equal numbers of sweetand flint plants and determining the amount of cross-pollinationmeasured by the contamination on sweet ears. It was found thatinter-crossing with flint varied significantly from plant toplant; the out-crossing generally was lower than anticipated.The effects of date of silking and tasselling, and protandryof sweet plants on their out-crossing was demonstrated by usingmultiple regression analysis. Even so, as prediction was stillnot satisfactory other factors must have been involved. Thesevariables were all highly correlated. A relation between contaminationand temporal isolation was established; this was similar tothat for spatial isolation. It was postulated that there mayhave been genetical control of inter-pollination, as later earson the same sweet-corn plants were not less contaminated thanearlier ones and because out-crossing was generally low throughoutthe experiment.     

Impacts of climate change and urban development on the spotted marsh frog (Limnodynastes tasmaniensis)

Climate change and urbanization are among the most serious threats to amphibians, although little is known about their combined effects. We used a predictive spatial habitat suitability model to explore the potential impacts of climate change and urban development on the spotted marsh frog (Limnodynastes tasmaniensis) on the urban‐fringe of Melbourne, Australia. The CSIRO climate‐change predictions for the region indicate likely temperature increases of 3°C, and annual rainfall reductions of around 200 mm by the year 2070. Much of the study area overlaps a region that has been identified as one of the city's growth corridors. We used Bayesian logistic regression modelling to estimate current and future habitat suitability of pond sites in the Merri Creek catchment, exploring a range of best‐ to worst‐case scenarios through the use of hydrological and urbanization models. Our predictions for 2070, even under a moderate climate‐change scenario, suggest that the majority of ponds in the study area will be dry throughout much of the year. This has obvious implications for L. tasmaniensis, which is an aquatic breeding species. However, in the short term, urbanization is likely to have a more significant effect on the distribution of L. tasmaniensis in the Merri Creek catchment, particularly if development moves beyond the current urban growth boundary. The combined effects of climate change and urbanization could have a profound impact on the species, potentially causing it to disappear from within the study area. We provide recommendations for including such predictive models in urban planning and restoration activities to prepare for future conservation challenges.     

Molecular genetic evidence for alternative reproductive strategies in North American pitvipers (Serpentes: Viperidae): long‐term sperm storage and facultative parthenogenesis

The first documentation of facultative parthenogenesis (FP) in non‐avian reptiles (snakes) occurred in 1997, following the application of molecular genetic methods for parentage analysis, and since has been described in only four additional snake species. Here, in two species of live‐bearing (viviparous) North American pitviper snakes, using microsatellite DNA fingerprinting, we describe the first record of a virgin birth by FP in the copperhead (Agkistrodon contortrix), and the first genetically confirmed case of long‐term sperm storage (LTSS) of exceptional duration (5 years) in the eastern diamond‐backed rattlesnake (Crotalus adamanteus). The capacity of female squamate reptiles (snakes, lizards, and amphisbaenians) to store viable sperm for extended periods of time is a competing hypothesis to FP, and it is often inferred when interpreting certain births where adult females have been isolated from adult male mates for prolonged periods. On reviewing the literature of certain cases of LTSS in snakes, we provide compelling support for the prevalence of FP, casting doubt over the widespread acceptance of LTSS. Accordingly, with the discovery of FP in squamates and the results of the present study, we advocate that in order to differentiate between LTSS and FP, especially under natural conditions, rigorous molecular testing will be required. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104 , 934–942.     

Time limitation affects offspring traits and female's fitness through maternal oviposition behaviour

Plasticity of various life‐history traits has evoked continuing interest among biologists. For example, the plasticity of offspring characteristics as well as maternal effects may be affected by time limitation and by limitation caused by changing environmental conditions. However, it is difficult to tell apart the effect of a time constraint, experienced by the mother, from food limitation, which is experienced by the offspring at the end of the season. In this study, we controlled for food limitation and simulated a time constraint for the mother. We tested how the seed beetle, Coccotrypes dactyliperda, adapts its reproductive investment after encountering a period of low availability of seeds as oviposition sites, as compared with females that encountered a seed at an early adult stage, while maintaining a similar food supply for offspring of both groups. We show that time limitation has a significant effect on the reproductive investment patterns of females. Females that were prevented from ovipositing, but provided with abundant food and later given oviposition sites, produced more, but smaller offspring than control females. Although the number of offspring increased, there was no indication of competition for food between offspring. We propose that, in order to compensate for the loss of time, mothers that experienced a shortage of oviposition sites influence their offspring to mature faster at the cost of a smaller than average body size. This study emphasizes the importance of considering more than one offspring generation in order to correctly estimate female fitness. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 728–736.     

Immunological responses from brachiopod skeletal macromolecules; a new technique for assessing taxonomic relationships using shells

The phylogenetic relationships of living, calcareous-shelled brachiopods have been assessed on the basis of immunological responses from intracrystalline macromolecules. Calculations of immunological distances between representatives of the order Terebratulida have revealed a primary threefold division which correlates precisely with a proposed subdivision of the order into three superfamilies but refutes attempts to establish a fourth superfamily. This conclusion was confirmed by carrying out immunological investigations of small shell fragments from other brachiopod genera which were so rare that no antisera could be prepared. The immunological results also indicate a fundamental subdivision of the long-looped brachiopods, with one group perhaps being derived from short-looped terebratuloids rather than long-looped terebratelloids. Sero-taxonomy of skeletal macromolecules provides an ideal method of acquiring molecular phylogenetic data in many groups because a large number of taxa can be surveyed in a short period of time, and microscopic pieces of shell contain sufficient antigenic determinants for many reactions. The technique can also be applied to specimens which have been stored without special treatment in museum collections, making the technique particularly applicable to rare taxa for which no other form of molecular data is available. □ Immunology, Brachiopoda, taxonomy, intracrystalline molecules.     

Cultural Landscapes in the Ancient Andes: Archaeologies of Place

Cultural Landscapes in the Ancient Andes: Archaeologies of Place . Jerry D. Moore. Gainesville: University Press of Florida, 2005. 270 pp.