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71.
One of the most direct human mechanisms of promoting cooperation is rewarding it. We study the effect of sharing a reward among cooperators in the most stringent form of social dilemma, namely the prisoner's dilemma (PD). Specifically, for a group of players that collect payoffs by playing a pairwise PD game with their partners, we consider an external entity that distributes a fixed reward equally among all cooperators. Thus, individuals confront a new dilemma: on the one hand, they may be inclined to choose the shared reward despite the possibility of being exploited by defectors; on the other hand, if too many players do that, cooperators will obtain a poor reward and defectors will outperform them. By appropriately tuning the amount to be shared a vast variety of scenarios arises, including the traditional ones in the study of cooperation as well as more complex situations where unexpected behavior can occur. We provide a complete classification of the equilibria of the n-player game as well as of its evolutionary dynamics. 相似文献
72.
Ariel E. Lugo 《Biotropica》2010,42(5):576-577
Cities contain over half of the world's population and are the source of many anthropogenic effects on the world's biota. Close examination of San Juan, Puerto Rico, a tropical city, reveals a significant green infrastructure. The city contains natural and human-constructed forests, urban aquatic systems with native and introduced species, and a thriving and diverse biota adapted to urban conditions. It behooves tropical ecologists to pay attention to the biodiversity of urban environments to learn lessons about ecological persistence and adaptation to novel anthropogenic environments. 相似文献
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74.
Based on studies from native Hawaiian Drosophila, a model was proposed to explain sexual isolation and mating asymmetry, from which one could potentially infer the 'direction of evolution'. We examined sexual isolation between allopatric cricket species of the genus Laupala, another endemic Hawaiian insect with an elaborate mating system, to begin to explore the nature of sexual isolation and mating asymmetry in closely related Hawaiian organisms. We studied sexual isolation and mating asymmetry in two contrasts. First, an inter-island comparison, including L. makaio from the older island of Maui and L. paranigra from the younger island of Hawaii, and second, an intra-island (Hawaii) comparison, including L. nigra from the older volcano of Mauna Kea and L. paranigra with a primary distribution on the younger volcanoes of Mauna Loa and Kilauea. We used a 'no-choice' experimental design, pairing individual males and females in homospecific or heterospecific combinations. Several behavioural aspects of courtship (proportion of male singing, latency to male singing, production of spermatophores and courtship initiation speed) were quantified as well as the success or failure of matings. We demonstrate asymmetry in sexual isolation between reciprocal combinations of L. makaio and L. paranigra. This result is examined in light of the differences in courtship behaviour manifest in the experiments with these two species. We did not find evidence of asymmetry in sexual isolation between L. nigra and L. paranigra, although differences in courtship initiation speed were evident between reciprocal combinations of these two species. In addition to the geological argument that species on older islands and older volcanoes give rise to species on younger islands and younger volcanoes, we discuss phylogenetic evidence consistent with these biogeographic hypotheses of relationships among the focal taxa. The patterns of asymmetrical sexual isolation and mating asymmetry are consistent with those found in the native Hawaiian Drosophila. 相似文献
75.
Torréns I Ojalvo AG Seralena A Pupo E Lugo V Páez R 《Biochemical and biophysical research communications》1999,266(1):230-236
Streptokinase (SK) is an efficacious thrombolytic drug for the treatment of myocardial infarction. Because of its immunogenicity, patients receiving SK therapy develop high anti-SK antibody (Ab) titers, which might provoke severe allergic reactions and neutralize SK activity. In this report we studied the reactivity of a synthetic 42-residue peptide resembling SKC-2 C-terminus with patient sera. SKC-2(373-414) peptide was recognized by 39 and 64% of patients, before and after SKC-2 therapy, respectively. An SKC-2 deletion mutant (mut-C42), lacking the same 42 C-terminal residues, was constructed and expressed in Escherichia coli. Recognition of mut-C42 by preexisting Abs from patient sera was 51 and 68% of reactivity to SKC-2, as assessed by direct binding and competition assays, respectively. For most of the patients, mut-C42-neutralizing activity titer (NAT) significantly decreased with respect to SKC-2-NAT. This study opens the possibility of producing a less immunogenic variant of SK, which could constitute a preferred alternative for thrombolytic therapy. 相似文献
76.
The relationships among seasons, host metabolic type, grazing and arbuscular mycorrhizal colonization were analyzed in a high South American native grassland. This study investigated seasonal changes and grazing effects on the symbiotic endomycorrhizal interaction in 5 Poaceae [C(3) metabolic pathway: Briza subaristata Lam., Deyeuxia hieronymi (Hack.) Türpe and Poa stuckertii (Hack.) Parodi; with C(4) metabolic pathway: Eragrostis lugens Nees and Sorghastrum pellitum (Hack.) Parodi; and a Rosaceae (Alchemilla pinnata Ruíz & Pav.)]. All hosts were dominant species in the mountain grassland in central Argentina. It was found that the seasons markedly influenced endomycorrhizal colonization, whereas grazing did not affect this interaction. C(4) grasses presented the highest root colonization. Hosts Briza subaristata (C(3) metabolic pathway) and Sorghastrum pellitum (C(4) metabolic pathway) showed Arum- and Paris-type colonization and intermediate forms. 相似文献
77.
Arbuscular mycorrhizal fungi (AMF) were studied in the rhizosphere of 3 Poaceae with metabolic pathway C(3) (Briza subaristata Lam., Deyeuxia hieronymi (Hack.) Türpe and Poa stuckertii (Hack.) Parodi), 2 Poaceae with C(4) metabolic type (Eragrostis lugens Nees and Sorghastrum pellitum (Hack.) Parodi.), and a Rosaceae (Alchemilla pinnata Ruíz & Pav.) from a natural mountain grassland in Central Argentina (South America). Host species, their metabolic type, seasonal changes, and grazing effects over AM fungal diversity were analyzed. Seventeen mycorrhizal fungi taxa were found, widespread in all families of Glomales. Density of endomycorrhizal fungi was found to be strongly influenced with seasons and host metabolic pathway, although biodiversity (H), richness (S) and evenness (E) did not change. In most cases grazing did not affect these variables. 相似文献
78.
79.
María de Lourdes Ramírez‐Ahuja Mayra A. Gmez‐Govea Angel Lugo‐Trampe Gissela Borrego‐Soto Ivn Delgado‐Enciso Gustavo Ponce‐Garcia Margarita L. Martínez‐Fierro Eda G. Ramírez‐Valles Víctor Trevio Adriana E. Flores‐Suarez Iram P. Rodríguez‐Sanchez 《Journal of Applied Entomology》2019,143(8):834-841
The microbiota of Hymenoptera is limited to certain bacterial species that vary according to the habitat and diet; however, the bacterial populations are not known in Telenomus tridentatus Johnson & Bin, an egg parasitoid of agricultural importance. We determined the microbiota composition of adults of T. tridentatus using next‐generation sequencing technologies. We found the presence of the Phylums Proteobacteria, in greater proportion followed by Actinobacteria and Firmicutes, respectively. The most abundant species were Cutibacterium acnes, Aquabacterium sp. and Massilia sp. The results of this study could lead to investigating the importance of symbiotic bacteria in T. tridentatus and its relation with agricultural plantations. 相似文献
80.
Ananworanich J Schuetz A Vandergeeten C Sereti I de Souza M Rerknimitr R Dewar R Marovich M van Griensven F Sekaly R Pinyakorn S Phanuphak N Trichavaroj R Rutvisuttinunt W Chomchey N Paris R Peel S Valcour V Maldarelli F Chomont N Michael N Phanuphak P Kim JH;RV/SEARCH Study Group 《PloS one》2012,7(3):e33948