Search results for "Biological Evolution"
showing 10 items of 522 documents
Food plant diversity as broad-scale determinant of avian frugivore richness.
2007
The causes of variation in animal species richness at large spatial scales are intensively debated. Here, we examine whether the diversity of food plants, contemporary climate and energy, or habitat heterogeneity determine species richness patterns of avian frugivores across sub-Saharan Africa. Path models indicate that species richness of Ficus (their fruits being one of the major food resources for frugivores in the tropics) has the strongest direct effect on richness of avian frugivores, whereas the influences of variables related to water–energy and habitat heterogeneity are mainly indirect. The importance of Ficus richness for richness of avian frugivores diminishes with decreasing sp…
Tradeoffs in the evolution of plant farming by ants
2020
Diverse forms of cultivation have evolved across the tree of life. Efficient farming requires that the farmer deciphers and actively promotes conditions that increase crop yield. For plant cultivation, this can include evaluating tradeoffs among light, nutrients, and protection against herbivores. It is not understood if, or how, nonhuman farmers evaluate local conditions to increase payoffs. Here, we address this question using an obligate farming mutualism between the ant Philidris nagasau and epiphytic plants in the genus Squamellaria that are cultivated for their nesting sites and floral rewards. We focused on the ants' active fertilization of their crops and their protection against he…
Ergosterol biosynthesis: a fungal pathway for life on land?
2012
International audience; Sterols, essential lipids of most eukaryotic cells, ensure important structural and signaling functions. The selection pressure that has led to different dominant sterols in the three eukaryotic kingdoms remains unknown. Here, we investigated the influence of the progression in the different steps of the ergosterol biosynthetic pathway (EBP) on the yeast resistance to transitions from aqueous to aerial media, typical perturbations of the higher fungi habitats. Five mutants of the EBP (ergΔ), accumulating different sterol intermediates in the EBP, and the wild-type (WT) strain were exposed to drying under atmospheric air or nitrogen and wetting. Results show that the …
Genetic variability and evolutionary analysis of parietaria mottle virus: role of selection and genetic exchange
2015
[EN] The genetic variability and evolution of parietaria mottle virus (PMoV) of the genus Ilarvirus was studied by analyzing nucleotide sequences of 2b and CP genes from isolates collected in different countries. Phylogenetic analysis showed that PMoV isolates clustered in different clades: one (clade I) composed of only Italian isolates and three clades (clades II-IV) including the Spanish isolates. The Greek isolate GrT-1 used in this study was in clade IV for the CP phylogenetic tree whereas it formed a separate branch in the 2b phylogenetic tree. The nucleotide sequence diversity of both the 2b and CP genes was low (0.062 +/- A 0.006 and 0.063 +/- A 0.006 for 2b and CP, respectively) bu…
Better the devil you know? Guidelines for insightful utilization of nrDNA ITS in species-level evolutionary studies in plants.
2006
The internal transcribed spacers (ITS) of the nuclear ribosomal 18S–5.8S–26S cistron continue to be the most popular non-plastid region for species-level phylogenetic studies of plant groups despite the early warnings about their potential Xaws, which may ultimately result in incorrect assumptions of orthology. It has been gradually realized that the alternative target regions in the nuclear genome (lowcopy nuclear genes, LCNG) are burdened with similar problems. The consequence is that, to date, developing useful LCNG for nonmodel organisms requires an investment in time and eVort that hinders its use as a real practical alternative for many labs. It is here argued that ITS sequences, desp…
Negative association between parental care and sibling cooperation in earwigs: a new perspective on the early evolution of family life?
2015
International audience; The evolution of family life requires net fitness benefits for offspring, which are commonly assumed to mainly derive from parental care. However, an additional source of benefits for offspring is often overlooked: cooperative interactions among juvenile siblings. In this study, we examined how sibling cooperation and parental care could jointly contribute to the early evolution of family life. Specifically, we tested whether the level of food transferred among siblings (sibling cooperation) in the European earwig F orficula auricularia (1) depends on the level of maternal food provisioning (parental care) and (2) is translated into offspring survival, as well as fem…
Mammary olfactory signalisation in females and odor processing in neonates: ways evolved by rabbits and humans
2009
International audience; Mammalian females have long been known to release olfactory attraction in their offspring. Mammary odor cues control infant state, attention and directional responses, delay distress responses, stimulate breathing and positive oral actions, and finally can boost learning. Here, we survey female-offspring odor communication in two mammalian species - European rabbits and humans - taken as representatives of evolutionary extremes in terms of structure and dynamics of mother-infant relations, and level of neonatal autonomy. Despite these early psychobiological differences, females in both species have evolved mammary structures combining multiple sources of endogenous a…
Sexual pheromones and the evolution of the reward system of the brain: the chemosensory function of the amygdala.
2008
The amygdala of all tetrapod vertebrates receives direct projections from the main and accessory olfactory bulbs, and the strong similarities in the organization of these projections suggest that they have undergone a very conservative evolution. However, current ideas about the function of the amygdala do not pay sufficient attention to its chemosensory role, but only view it as the core of the emotional brain. In this study, we propose that both roles of the amygdala are intimately linked since the amygdala is actually involved in mediating emotional responses to chemical signals. The amygdala is the only structure in the brain receiving pheromonal information directly from the accessory …
Controversies on the origin of life
2005
Different viewpoints, many with deep philosophical and historical roots, have shaped the scientific study of the origin of life. Some of these argue that primeval life was based on simple anaerobic microorganisms able to use a wide inventory of abiotic organic materials (i.e. a heterotrophic origin), whereas others invoke a more sophisticated organization, one that thrived on simple inorganic molecules (i.e. an autotrophic origin). While many scientists assume that life started as a self-replicative molecule, the first gene, a primitive self-catalytic metabolic network has also been proposed as a starting point. Even the emergence of the cell itself is a contentious issue: did boundaries an…
Conservation of optical purity of amino acids: a principal problem in biochemical and proto-biochemical systems.
1981
Dor L-amino acids, regardless of their state (peptide-bound or free, in the solid state or in aqueous solution), tend to racemize. In a living cell this racemization is usually compensated by specific degradation and replacement of the unwanted polypeptides that contain the wrong enantiomers. But a few long-lived proteins that are synthesized at or near birth are never replaced. Well investigated is the racemization of L-aspartic acid at a rate of 0.1 to 1.14 per cent per year in proteins from lenses and dentine. Increased racemization of eye lens proteins has been related to a form of human eye disease known as brunescent cataracts. Also quite well investigated is the racemization of amino…