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Are gastropods, rather than ants, important dispersers of seeds of myrmecochorous forest herbs?
(2012)
Seed dispersal by ants (myrmecochory) is widespread, and seed adaptations to myrmecochory are common, especially in the form of fatty appendices (elaiosomes). In a recent study, slugs were identified as seed dispersers of myrmecochores in a central European beech forest. Here we used 105 beech forest sites to test whether myrmecochore presence and abundance is related to ant or gastropod abundance and whether experimentally exposed seeds are removed by gastropods. Myrmecochorous plant cover was positively related to gastropod abundance but was negatively related to ant abundance. Gastropods were responsible for most seed removal and elaiosome damage, whereas insects (and rodents) played minor roles. These gastropod effects on seeds were independent of region or forest management. We suggest that terrestrial gastropods can generally act as seed dispersers of myrmecochorous plants and even substitute myrmecochory, especially where ants are absent or uncommon.
Moving in the Anthropocene
(2018)
Animal movement is fundamental for ecosystem functioning and species survival, yet the effects of the anthropogenic footprint on animal movements have not been estimated across species. Using a unique GPS-tracking database of 803 individuals across 57 species, we found that movements of mammals in areas with a comparatively high human footprint were on average one-half to one-third the extent of their movements in areas with a low human footprint. We attribute this reduction to behavioral changes of individual animals and to the exclusion of species with long-range movements from areas with higher human impact. Global loss of vagility alters a key ecological trait of animals that affects not only population persistence but also ecosystem processes such as predator-prey interactions, nutrient cycling, and disease transmission.
A cluster approach extended to the ONIOM methodology has been applied using several density functionals and Moller-Plesset perturbation theory (MP2) to simulate the adsorption of selected nitrogen-containing compounds [NCCs, 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT), 2,4-dinitroanisole (DNAN), and 3-nitro-1,2,4-triazole-5-one (NTO)] on the hydroxyated (100) surface of a-quartz. The structural properties were calculated using the M06-2X functional and 6-31G(d,p) basis set. The M06-2X-D3, PBE-D3, and MP2 methods were used to calculate the adsorption energies. Results have been compared with the data from other studies of adsorption of compounds of similar nature on silica. Effect of deformation of the silica surface and adsorbates on the binding energy values was also studied. The atoms in molecules (AIM) analysis was employed to characterize the adsorbate-adsorbent binding and to calculate the bond energies. The silica surface shows different sorption affinity toward the chemicals considered depending on their electronic structure. All target NCCs are physisorbed on the modeled silica surface. Adsorption occurs due to the formation of multiple hydrogen bonds between the functional groups of NCCs and surface silanol groups. Parallel orientation of NCCs interacting with the silica surface was found to be favorable when compared with perpendicularly oriented NCCs. NTO was found to be the most strongly adsorbed on the silica surface among all of the considered compounds. Dispersion correction was shown to play an important role in the DFT calculations of the adsorption energies of silica-NCC systems.
River ecosystems receive and process vast quantities of terrestrial organic carbon, the fate of which depends strongly on microbial activity. Variation in and controls of processing rates, however, are poorly characterized at the global scale. In response, we used a peer-sourced research network and a highly standardized carbon processing assay to conduct a global-scale field experiment in greater than 1000 river and riparian sites. We found that Earth’s biomes have distinct carbon processing signatures. Slow processing is evident across latitudes, whereas rapid rates are restricted to lower latitudes. Both the mean rate and variability decline with latitude, suggesting temperature constraints toward the poles and greater roles for other environmental drivers (e.g., nutrient loading) toward the equator. These results and data set the stage for unprecedented “next-generation biomonitoring” by establishing baselines to help quantify environmental impacts to the functioning of ecosystems at a global scale.
The northward motion of the Pamir indenter with respect to Eurasia has resulted in coeval thrusting, strike-slip faulting, and normal faulting. The eastern Pamir is currently deformed by east-west oriented extension, accompanied by uplift and exhumation of the Kongur Shan (7719m) and Muztagh Ata (7546m) gneiss domes. Both domes are an integral part of the footwall of the Kongur Shan extensional fault system (KES), a 250 km long, north-south oriented graben. Why active normal faulting within the Pamir is primarily localized along the KES and not distributed more widely throughout the orogen has remained unclear. In addition, relatively little is known about how deformation has evolved throughout the Cenozoic, despite refined estimates on present-day crustal deformation rates and microseismicity, which indicate where crustal deformation is presently being accommodated. To better constrain the spatiotemporal evolution of faulting along the KES, we present 39 new apatite fission track, zircon U-Th-Sm/He, and Ar-40/Ar-39 cooling ages from a series of footwall transects along the KES graben shoulder. Combining these data with present-day topographic relief, 1-D thermokinematic and exhumational modeling documents successive stages, rather than synchronous deformation and gneiss dome exhumation. While the exhumation of the Kongur Shan commenced during the late Miocene, extensional processes in the Muztagh Ata massif began earlier and have slowed down since the late Miocene. We present a new model of synorogenic extension suggesting that thermal and density effects associated with a lithospheric tear fault along the eastern margin of the subducting Alai slab localize extensional upper plate deformation along the KES and decouple crustal motion between the central/western Pamir and eastern Pamir/Tarim basin.
Coincident with the intensification of Northern Hemisphere Glaciation (WIG) around 2.73 million years (Ma) ago, sediment cores from both the open subarctic North Pacific and the Antarctic indicate a rapid decline in diatom opal accumulation flux to the seabed, representing one of the most abrupt and dramatic changes in the marine sediment record associated with the development of Pleistocene glacial cycles. In the North Pacific, bulk sediment nitrogen isotope data and alkenone-derived sea surface temperature (SST) estimates suggest that the productivity decline was driven by reduced exchange between surface and deep water, due to weaker wind-driven upwelling and/or a strengthening of the halocline (i.e. "stratification"). In this study of the 2.73 Ma transition at Ocean Drilling Program (ODP) Site 882 in the western subarctic North Pacific, diatom-bound nitrogen isotopes (delta N-15(db)), alkenone mass accumulation rate, and alkenone- and archaeal tetraether-based SST reconstructions support the stratification hypothesis, indicating perennially lower export production, generally higher nitrate consumption, and greater inter-seasonal variation in SST after the 2.73 Ma transition. In addition, the delta N-15(db) of large and small size fractions of Coscinodiscus spp. suggest that these diatoms grew mostly during the spring bloom during the late Pliocene, switching to their current fall-to-winter growth period at the 2.73 Ma transition; this view is consistent with their decline in dominance and provides further evidence for increased stratification (reduced vertical exchange) in the North Pacific after 2.73 Ma. The delta N-15(db) data indicate that, over the similar to 100 kyr period after the 2.73 Ma transition studied here, nitrate consumption did not reach late Pleistocene ice age levels and that nitrate consumption in post-2.73 Ma warm stages was similar to that before the transition, even though productivity was greatly reduced. We tentatively attribute this to relatively weak dust-borne iron inputs in the early post-2.73 Ma period.
Alcohol-related cues acquire incentive salience through Pavlovian conditioning and then can markedly affect instrumental behavior of alcohol-dependent patients to promote relapse. However, it is unclear whether similar effects occur with alcohol-unrelated cues. We tested 116 early-abstinent alcohol-dependent patients and 91 healthy controls who completed a delay discounting task to assess choice impulsivity, and a Pavlovian-to-instrumental transfer (PIT) paradigm employing both alcohol-unrelated and alcohol-related stimuli. To modify instrumental choice behavior, we tiled the background of the computer screen either with conditioned stimuli (CS) previously generated by pairing abstract pictures with pictures indicating monetary gains or losses, or with pictures displaying alcohol or water beverages. CS paired to money gains and losses affected instrumental choices differently. This PIT effect was significantly more pronounced in patients compared to controls, and the group difference was mainly driven by highly impulsive patients. The PIT effect was particularly strong in trials in which the instrumental stimulus required inhibition of instrumental response behavior and the background CS was associated to monetary gains. Under that condition, patients performed inappropriate approach behavior, contrary to their previously formed behavioral intention. Surprisingly, the effect of alcohol and water pictures as background stimuli resembled that of aversive and appetitive CS, respectively. These findings suggest that positively valenced background CS can provoke dysfunctional instrumental approach behavior in impulsive alcohol-dependent patients. Consequently, in real life they might be easily seduced by environmental cues to engage in actions thwarting their long-term goals. Such behaviors may include, but are not limited to, approaching alcohol.
Species diversity promotes the delivery of multiple ecosystem functions (multifunctionality). However, the relative functional importance of rare and common species in driving the biodiversity multifunctionality relationship remains unknown. We studied the relationship between the diversity of rare and common species (according to their local abundances and across nine different trophic groups), and multifunctionality indices derived from 14 ecosystem functions on 150 grasslands across a land use intensity (LUI) gradient. The diversity of above- and below-ground rare species had opposite effects, with rare above-ground species being associated with high levels of multifunctionality, probably because their effects on different functions did not trade off against each other. Conversely, common species were only related to average, not high, levels of multifunctionality, and their functional effects declined with LUI. Apart from the community level effects of diversity, we found significant positive associations between the abundance of individual species and multifunctionality in 6% of the species tested. Species specific functional effects were best predicted by their response to LUI: species that declined in abundance with land use intensification were those associated with higher levels of multifunctionality. Our results highlight the importance of rare species for ecosystem multifunctionality and help guiding future conservation priorities.
The timing of the late Cenozoic collision between the Pamir salient and the Tien Shan as well as changes in the relative motion between the Pamir and Tarim are poorly constrained. The northern margin of the Pamir salient indented northward by similar to 300 km during the late Cenozoic, accommodated by south-dipping intracontinental subduction along the Main Pamir Thrust (MPT) coupled to strike-slip faults on the eastern flank of the orogen and both strike-slip and thrust faults on the western margin. The Kashgar-Yecheng transfer system (KYTS) is the main dextral slip shear zone separating Tarim from the Eastern Pamir, with an estimated cumulative offset of similar to 280 km at an average late Cenozoic dextral slip rate of 11-15 mm/a (Cowgill, 2010). In order to better constrain the slip history of the KYTS, we collected thermochronologic samples along the eastward-flowing, deeply incised, antecedent Tashkorgan-Yarkand River, which crosses the fault system on the eastern flank of the orogen. We present 29 new biotite (40)Ar/(39)Ar ages, apatite and zircon (U-Th-Sm)/He ages, and apatite fission track (AFT) analysis, combined with published muscovite and biotite (40)Ar/(39)Ar and AFT data, to create a unique thermochronologic dataset in this poorly studied and remote region. We constrain the timing of four major N-trending faults: the latter three are strands of the KYTS. The westernmost, the Kuke fault, experienced significant dip-slip, west-side-up displacement between > 12 and 6 Ma. To the east, within the KYTS, our new thermochronologic data and geomorphic observations suggest that the Kumtag and Kusilaf dextral slip faults have been inactive since at least 3-5 Ma. Long-term incision rates across the Aertashi dextral slip fault, the easternmost strand of the KYTS, are compatible with slow horizontal slip rates of 1.7-5.3 mm/a over the past 3 to 5 Ma. In summary, these data show that the slip rate of the KYTS decreased substantially during the late Miocene or Pliocene. Furthermore, Miocene-present regional kinematic reconstructions suggest that this deceleration reflects the substantial increase of northward motion of Tarim rather than a significant decrease of the northward velocity of the Pamir. (C) 2011 Elsevier B.V. All rights reserved.