Search results for " Environmental studies"
showing 10 items of 24 documents
Daphnia invest in sexual reproduction when its relative costs are reduced
2018
The timing of sex in facultatively sexual organisms is critical to fitness, due to the differing demographic consequences of sexual versus asexual reproduction. In addition to the costs of sex itself, an association of sex with the production of dormant life stages also influences the optimal use of sex, especially in environments where resting eggs are essential to survive unfavourable conditions. Here we document population dynamics and the occurrence of sexual reproduction in natural populations of Daphnia magna across their growing season. The frequency of sexually reproducing females and males increased with population density and with decreasing asexual clutch sizes. The frequency of…
Social transmission of avoidance among predators facilitates the spread of novel prey.
2018
Warning signals are an effective defence strategy for aposematic prey, but only if they are recognized by potential predators. If predators must eat prey to associate novel warning signals with unpalatability, how can aposematic prey ever evolve? Using experiments with great tits (Parus major) as predators, we show that social transmission enhances the acquisition of avoidance by a predator population. Observing another predator’s disgust towards tasting one novel conspicuous prey item led to fewer aposematic than cryptic prey being eaten for the predator population to learn. Despite reduced personal encounters with unpalatable prey, avoidance persisted and increased over subsequent trials.…
Inbreeding reveals mode of past selection on male reproductive characters in Drosophila melanogaster
2013
Directional dominance is a prerequisite of inbreeding depression. Directionality arises when selection drives alleles that increase fitness to fixation and eliminates dominant deleterious alleles, while deleterious recessives are hidden from it and maintained at low frequencies. Traits under directional selection (i.e., fitness traits) are expected to show directional dominance and therefore an increased susceptibility to inbreeding depression. In contrast, traits under stabilizing selection or weakly linked to fitness are predicted to exhibit little-to-no inbreeding depression. Here, we quantify the extent of inbreeding depression in a range of male reproductive characters and then infer t…
Shrines in Central Italy conserve plant diversity and large trees
2015
Sacred natural sites (SNS) are instances of biocultural landscapes protected for spiritual motives. These sites frequently host important biological values in areas of Asia and Africa, where traditional resource management is still upheld by local communities. In contrast, the biodiversity value of SNS has hardly been quantitatively tested in Western contexts, where customs and traditions have relatively lost importance due to modernization and secularization. To assess whether SNS in Western contexts retain value for biodiversity, we studied plant species composition at 30 SNS in Central Italy and compared them with a paired set of similar but not sacred reference sites. We demonstrate tha…
Postcopulatory sexual selection generates speciation phenotypes in Drosophila.
2013
Background: Identifying traits that reproductively isolate species and the selective forces underlying their divergence is a central goal of evolutionary biology and speciation research. There is growing recognition that postcopulatory sexual selection which can drive rapid diversification of interacting ejaculate and female reproductive tract traits that mediate sperm competition may be an engine of speciation. Conspecific sperm precedence (CSP) is a taxonomically widespread form of reproductive isolation but the selective causes and divergent traits responsible for CSP are poorly understood. Results: To test the hypothesis that postcopulatory sexual selection can generate reproductive iso…
Pairing context determines condition-dependence of song rate in a monogamous passerine bird.
2013
Condition-dependence of male ornaments is thought to provide honest signals on which females can base their sexual choice for genetic quality. Recent studies show that condition-dependence patterns can vary within populations. Although long-term association is thought to promote honest signalling, no study has explored the influence of pairing context on the condition-dependence of male ornaments. In this study, we assessed the influence of natural variation in body condition on song rate in zebra finches ( Taeniopygia guttata ) in three different situations: during short and long encounters with an unfamiliar female, and within heterosexual mated pairs. We found consistent individual diff…
Handbook of protocols for standardized measurement of terrestrial invertebrate functional traits
2017
Trait-based approaches are increasingly being used to test mechanisms underlying species assemblages and biotic interactions across a wide range of organisms including terrestrial arthropods and to investigate consequences for ecosystem processes. Such an approach relies on the standardized measurement of functional traits that can be applied across taxa and regions. Currently, however, unified methods of trait measurements are lacking for terrestrial arthropods and related macroinvertebrates (terrestrial invertebrates hereafter). Here, we present a comprehensive review and detailed protocol for a set of 29 traits known to be sensitive to global stressors and to affect ecosystem processes a…
Origin of modern syphilis and emergence of a pandemic Treponema pallidum cluster
2016
The abrupt onslaught of the syphilis pandemic that started in the late fifteenth century established this devastating infectious disease as one of the most feared in human history1 . Surprisingly, despite the availability of effective antibiotic treatment since the mid-twentieth century, this bacterial infection, which is caused by Treponema pallidum subsp. pallidum (TPA), has been re-emerging globally in the last few decades with an estimated 10.6 million cases in 2008 (ref. 2). Although resistance to penicillin has not yet been identified, an increasing number of strains fail to respond to the secondline antibiotic azithromycin3. Little is known about the genetic patterns in current infec…
Importance of Sequence and Timing in Parasite Coinfections
2019
Coinfections by multiple parasites predominate in the wild. Interactionsbetween parasites can be antagonistic, neutral, or facilitative, and they canhave significant implications for epidemiology, disease dynamics, and evolu-tion of virulence. Coinfections commonly result from sequential exposure ofhosts to different parasites. We argue that the sequential nature of coinfectionsis important for the consequences of infection in both natural and man-madeenvironments. Coinfections accumulate during host lifespan, determining thestructure of the parasite infracommunity. Interactions within the parasite com-munity and their joint effect on the host individual potentially shape evolution ofparasi…
Molecular characterization of Treponema pallidum subsp. pallidum in Switzerland and France with a new multilocus sequence typing scheme
2018
Syphilis is an important public health problem and an increasing incidence has been noted in recent years. Characterization of strain diversity through molecular data plays a critical role in the epidemiological understanding of this re-emergence. We here propose a new high-resolution multilocus sequence typing (MLST) scheme for Treponema pallidum subsp. pallidum (TPA). We analyzed 30 complete and draft TPA genomes obtained directly from clinical samples or from rabbit propagated strains to identify suitable typing loci and tested the new scheme on 120 clinical samples collected in Switzerland and France. Our analyses yielded three loci with high discriminatory power: TP0136, TP0548, and TP…