Population dynamics of three songbird species in a nestbox population in Central Europe show effects of density,climate and competitive interactions

Unravelling the contributions of density‐dependent and density‐independent factors in determining species population dynamics is a challenge, especially if the two factors interact. One approach is to apply stochastic population models to long‐term data, yet few studies have included interactions between density‐dependent and density‐independent factors, or explored more than one type of stochastic population model. However, both are important because model choice critically affects inference on population dynamics and stability. Here, we used a multiple models approach and applied log‐linear and non‐linear stochastic population models to time series (spanning 29 years) on the population growth rates of Blue Tits Cyanistes caeruleus, Great Tits Parus major and Pied Flycatchers Ficedula hypoleuca breeding in two nestbox populations in southern Germany. We focused on the roles of climate conditions and intra‐ and interspecific competition in determining population growth rates. Density dependence was evident in all populations. For Blue Tits in one population and for Great Tits in both populations, addition of a density‐independent factor improved model fit. At one location, Blue Tit population growth rate increased following warmer winters, whereas Great Tit population growth rates decreased following warmer springs. Importantly, Great Tit population growth rate also decreased following years of high Blue Tit abundance, but not vice versa. This finding is consistent with asymmetric interspecific competition and implies that competition could carry over to influence population dynamics. At the other location, Great Tit population growth rate decreased following years of high Pied Flycatcher abundance but only when Great Tit population numbers were low, illustrating that the roles of density‐dependent and density‐independent factors are not necessarily mutually exclusive. The dynamics of this Great Tit population, in contrast to the other populations, were unstable and chaotic, raising the question of whether interactions between density‐dependent and density‐independent factors play a role in determining the (in) stability of the dynamics of species populations.     

Soft–part preservation in heteromorph ammonites from the Cenomanian–Turonian Boundary Event (OAE 2) in north–west Germany

Abstract: From thinly laminated marlstones of the Hesseltal Formation, representing the Late Cenomanian Oceanic Anoxic Event (OAE) 2, at Lengerich in the Teutoburger Wald (Westfalen, north‐west Germany), 17 sediment‐compacted baculitid ammonites with carbonised and partially phosphatised soft parts are recorded. Some preserve remains of the buccal mass, including jaws (occasionally articulated) and radulae, as well as of the cephalic cartilage, such as eye capsules. Such have not yet been recorded previously for the order Ammonoidea. In addition, originally unmineralised parts found preserved in these specimens include extensive portions of the digestive tract, the siphonal tube, false colour patterns (megastriae), as well as traces of what would appear to be the oviduct. At the same levels, patches with numerous isolated horny upper and rarer lower jaws as well as radulae occur; these may represent regurgitates or faeces of larger predators. The cephalopod remains described were deposited in an epicontinental setting, possibly at palaeodepths between 200 and 600 m. In this particular Late Cretaceous fossil Lagerstätte, upper jaws and anaptychi of ammonites rank among the commonest fossils.     

Hesperotestudo (Testudines: Testudinidae) from the Pleistocene of Bermuda, with comments on the phylogenetic position of the genus

A recently discovered fossil land tortoise (Testudines: Testudinidae) is described from the Pleistocene of Bermuda. Its morphology is sufficiently well preserved to allow assignment to the extinct North American genus Hesperotestudo. However, several features of this tortoise are unique and it is named Hesperotestudo bermudae sp. nov. A review of the phylogenetic relationships of the better known genera of the Testudinidae suggests that the affinities of Hesperotestudo lie with other North American tortoises (Gopherus) and not with Geochelone or other testudinines; thus, Hesperotestudo is reassigned to the Xerobatinae. This is at least the fifth documentation of a testudinid dispersing over open ocean to an oceanic island (the first for Hesperotestudo) and it corroborates the hypothesis that members of this family are well suited to over-water dispersal.     

On the potential for ocean acidification to be a general cause of ancient reef crises

Anthropogenic rise in the carbon dioxide concentration in the atmosphere leads to global warming and acidification of the oceans. Ocean acidification (OA) is harmful to many organisms but especially to those that build massive skeletons of calcium carbonate, such as reef corals. Here, we test the recent suggestion that OA leads not only to declining calcification of reef corals and reduced growth rates of reefs but may also have been a trigger of ancient reef crises and mass extinctions in the sea. We analyse the fossil record of biogenic reefs and marine organisms to (1) assess the timing and intensity of ancient reef crises, (2) check which reef crises were concurrent with inferred pulses of carbon dioxide concentrations and (3) evaluate the correlation between reef crises and mass extinctions and their selectivity in terms of inferred physiological buffering. We conclude that four of five global metazoan reef crises in the last 500 Myr were probably at least partially governed by OA and rapid global warming. However, only two of the big five mass extinctions show geological evidence of OA.     

Relationships Between Invertebrate Phyla Based on Functional-Mechanical Analysis of the Hydrostatic Skeleton

SYNOPSIS. The phylogeny of the major groups of deuterostomecoelomates—the chordates,hemichordates and echinoderms—isdiscussed based on a mechanical-functional analysis of the hydrostaticskeleton and associated structures. The basic approach is tofirst establish transformation series of individual featuresand of functional complexes of features and secondto determinetheir "Lesrichtung" by showing the direction of increased economy(i.e., better adaptation) with respect to environmental factors.It is argued that a metameric coelom is primitive with respectto an oligomeric one and that the ancestral form of the deuterostomecoelomates is a metameric, coelomate worm-like animal with acomplex set of circular, transverse andlongitudinal body muscles.The coelom plus the complex body musculature formed the hydrostaticskeleton.The sequence of structural modifications leading to chordatesis: (a) appearance of the notochord; (b) specialization of thedorsal longitudinal muscles with a reduction and disappearanceof the transverse and circular muscles; (c) simultaneous appearanceof the dorsal hollow nerve cord; (d) development of a postanaltail; and (e) appearance and specialization of the branchialbasket with gill slits as a filter feeding apparatus. The primitivechordate would be most similar to the lancelet (Acrania). Tunicatesare advanced chordates specialized forsessile life and lostmost chordate features in the adult, but retained them in thelarvae as adaptations for active dispersal. Enteropneusts (acornworms) are another advanced group specialized for burrowingin fine sediments and that evolved the anterior proboscis asa peristaltic burrowing organ. The notochord was lost as wasthe dorsal nerve cord and segmented conditionof the coelom.A collar originated as a means to prevent discharged water fromre-entering themouth. Pterobranchs arose from enteropneustlikeforms; their major structural changes are reduction of the branchialbasket and modification of the collar into tentacles which areassociated with life in a closed tube. Finally, echinodermsarose from a pterobranch-like ancestor by specializing for sessilelife and feeding with tentacles and by final loss of the branchialbasket. Groups such as the tunicates, hemichordates and echinodermscould be eliminated as ancestral forms within the deuterostomecoelomates because the evolution of acraniates and vertebratesfrom each of these groups would involve the appearance of gillslits before the notochord and/or the evolution of a metamericcoelom from an oligomeric one, both of which are exceedinglyimprobable. Central to the methods used to establish the transformationseries of features and their direction of evolutionary change(Lesrichtung) are functional (mechanical) analysis and adaptiveinterpretation of features; hence, functional-adaptive analysesare an integral and essential part of the methodology of phylogeneticinvestigation.     

The Importance of Water Vapour for the Circulating Air Flow through Nelumbo nucifera

Aquatic vascular plants depend on an adequate oxygen supplyin order to maintain growth and reproduction in anaerobic environments.Nelumbo nucifera is able to survive with a gas transport systemwhich supplies oxygen to the roots and rhizomes submerged inthe anaerobic sediment. It was possible to demonstrate thatthis gas transport system is based on a purely physical phenomenonThermo-osmotic oxygen transport was first demonstrated on freshleaves with the help of an oxygen-sensitive electrode. A definiteenhancement of oxygen flow was obtained through excised leaveswhen a temperature difference between the ambient and lacunarair was present in light. These leaves were then dried to brittlenessand the enhanced oxygen flow was still detectable. This showsthat not only photosynthetic oxygen, but also atmospheric oxygencan be transported to the buried organs. The absolute flow ofoxygen through dry leaves was much lower than through freshleaves, but the thermo-osmotic transport of oxygen still functioned.Furthermore, the process of thermo-osmosis need not rely ona difference in humidity between the two sides of a porous partition,but may be linked causally to the temperature difference andthe pore size. Key words: Nelumbo nucifera, oxygen transport, thermo-osmosis of gases     

Patterns of divergence in the olive sunbird Cyanomitra olivacea (Aves: Nectariniidae) across the African rainforest–savanna ecotone

In the debate over modes of vertebrate diversification in tropical rainforests, two competing hypotheses of speciation predominate: those that emphasize the role of geographical isolation during glacial periods and those that stress the role of ecology and diversifying selection across ecotones or environmental gradients. To investigate the relative roles of selection versus isolation in refugia, we contrasted genetic and morphologic divergence of the olive sunbird (Cyanomitra olivacea) at 18 sites (approximately 200 individuals) across the forest–savanna ecotone of Central Africa in a region considered to have harboured three hypothesized refugia during glacial periods. Habitats were characterized using bioclimatic and satellite remote‐sensing data. We found relatively high levels of gene flow between ecotone and forest populations and between refugia. Consistent with a pattern of divergence‐with‐gene‐flow, we found morphological characters to be significantly divergent across the gradient [forest versus ecotone (mean ± SD): wing length 60.47 ± 1.81 mm versus 62.18 ± 1.35 mm; tarsus length 15.51 ± 0.82 mm versus 16.00 ± 0.57 mm; upper mandible length 21.77 ± 1.09 mm versus 23.19 ± 0.98 mm, respectively]. Within‐habitat comparisons across forest and ecotone sites showed no significant differences in morphology. The results show that divergence in morphological traits is tied to environmental variables across the gradient and is occurring despite gene flow. The pattern of divergence‐with‐gene‐flow found is similar to that described for other rainforest species across the gradient. These results suggest that neither refugia, nor isolation‐by‐distance have played a major role in divergence in the olive sunbird, although ecological differences along the forest and savanna ecotone may impose significant selection pressures on the phenotype and potentially be important in diversification. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 103 , 821–835.     

Subcellular compartmentation of elements in non-mycorrhizal and mycorrhizal roots of Pinus sylvestris: an X-ray microanalytical study. II. The distribution of calcium, potassium and sodium

The inter- and intracellular distribution of the elements calcium, potassium and sodium in non-mycorrhizal and mycorrhizal roots of Pinus sylvestris dependent on different external nutrient supply conditions was detected by energy-dispersive X-ray microanalysis after cryofixation, freeze-drying and pressure infiltration of the material. In non-mycorrhizal and mycorrhizal roots, calcium was mainly detectable in the apoplastic regions. The levels in vacuoles and cytoplasm were near the limits of detection by X-ray microanalysis. Incubation with high concentrations of potassium and sodium, or mycorrhizal infection with Suillus bovinus and Pisolithus tinctorius reduced the amounts of calcium detectable in the roots, especially in the apoplast of cortical cells. The studies revealed that: potassium is mainly localized in cytoplasm and cell walls; the cytoplasmic content is regulated over a wide range of external potassium concentrations; potassium levels in the inner parts of roots are higher than in the outer parts. Mycorrhizal infection with Suillus bovinus had no effect on the inter- and intracellular distribution of potassium in roots but, if the external supply was low, the potassium content in shoots was reduced. In non-mycorrhizal pine roots and those infected with Paxillus involutus an increase in the sodium content of all cell compartments was observed after treatment with high external concentrations of NaH₂PO₄. However, an increase in sodium content in mycorrhizas of S. bovinus was not detected. The X-ray microanalytical results are discussed in relation to the apoplastic movement of nutrients in non-mycorrhizal and mycorrhizal fine roots of pine and to the demand for these nutrients in different intracellular compartments.     

Is there any evidence that aphid alarm pheromones work as prey and host finding kairomones for natural enemies?

1. The aphid alarm pheromone (E)‐β‐farnesene (EBF) is often considered to be used by natural enemies as a prey/host finding kairomone. However, studies show opposing results, some appear to confirm an attraction of aphid natural enemies by EBF whereas others do not provide any evidence for the kairomone function of EBF. 2. To clarify if aphid natural enemies are attracted by the amounts of EBF naturally emitted by aphids, the existing literature was reviewed about EBF attractiveness to aphid natural enemies with consideration of the amounts of EBF used in the studies. 3. Thirty‐one publications that investigated the ability of EBF, aphid cornicle secretion, and attacked aphids, to attract aphid natural enemies were found. Several studies showed an attraction by EBF, but these used much higher amounts of EBF than usually emitted by aphids during a predator attack. Studies investigating EBF amounts similar to what is emitted by aphids are rare and failed to show attraction. Only two studies document an attraction of natural enemies by attacked aphids. 4. As EBF is emitted in very low amounts, not very stable, and only present after an attack, we suggest that aphid‐derived EBF is not a suitable kairomone for most natural enemy species, especially when they are able to use alternative cues. As EBF, amongst other volatiles, is also emitted by herbivore‐induced plants, we propose that natural enemies might use plant‐derived EBF as a synomone to identify aphid‐infested plants via an altered plant volatile bouquet.     

Robust dynamics of Amazon dieback to climate change with perturbed ecosystem model parameters

Climate change science is increasingly concerned with methods for managing and integrating sources of uncertainty from emission storylines, climate model projections, and ecosystem model parameterizations. In tropical ecosystems, regional climate projections and modeled ecosystem responses vary greatly, leading to a significant source of uncertainty in global biogeochemical accounting and possible future climate feedbacks. Here, we combine an ensemble of IPCC‐AR4 climate change projections for the Amazon Basin (eight general circulation models) with alternative ecosystem parameter sets for the dynamic global vegetation model, LPJmL. We evaluate LPJmL simulations of carbon stocks and fluxes against flux tower and aboveground biomass datasets for individual sites and the entire basin. Variability in LPJmL model sensitivity to future climate change is primarily related to light and water limitations through biochemical and water‐balance‐related parameters. Temperature‐dependent parameters related to plant respiration and photosynthesis appear to be less important than vegetation dynamics (and their parameters) for determining the magnitude of ecosystem response to climate change. Variance partitioning approaches reveal that relationships between uncertainty from ecosystem dynamics and climate projections are dependent on geographic location and the targeted ecosystem process. Parameter uncertainty from the LPJmL model does not affect the trajectory of ecosystem response for a given climate change scenario and the primary source of uncertainty for Amazon ‘dieback’ results from the uncertainty among climate projections. Our approach for describing uncertainty is applicable for informing and prioritizing policy options related to mitigation and adaptation where long‐term investments are required.