Search results for "Systematics"
showing 10 items of 6702 documents
Evolution education in natural history museums
2009
During 2009, scientists around the world will celebrate the 200th anniversary of the birth of Charles Darwin, the father of the theory of evolution, and the 150th anniversary of the publication of his main thesis, On the Origin of Species by Means of Natural Selection. Today, the theory of evolution is considered to be one of the greatest milestones in the history of science. Despite its undisputed merit in science, there seems to be constant turmoil around the theory in the public, which might be related to the incomplete understanding of the basic principles of evolution [1,2].
Tettigoniidae (Insecta: Orthoptera) collected in tropical forests of Zambia, Cameroon, Gabon and São Tomé during the entomological expeditions of Afr…
2021
The present study is based on a significant sample of Orthoptera, mainly Tettigonoidea, collected by the African Natural History Research Trust in four African countries; a total of 109 taxa was fo...
Plant Morphology: The Historic Concepts of Wilhelm Troll, Walter Zimmermann and Agnes Arber
2001
Recent molecular systematic and developmental genetic findings have drawn attention to plant morphology as a discipline dealing with the phenotypic appearance of plant forms. However, since different terms and conceptual frameworks have evolved over a period of more than 200 years, it is reasonable to survey the history of plant morphology; this is the first of two papers with this aim. The present paper deals with the historic concepts of Troll, Zimmermann and Arber, which are based on Goethe's morphology. Included are contrasting views of ‘unity and diversity’, ‘position and process’, and ‘morphology and phylogeny’, which, in part, are basic views of current plant morphology, phylogenetic…
When to be sexual: sex allocation theory and population density-dependent induction of sex in cyclical parthenogens
2008
The timing of sex is a critical fitness component in the cyclically parthenogenetic life-cycle of rotifers. It has been hypothesized that sex in rotifers is optimally timed to high population density because male‐female encounters are more probable. Because sexual females produce either males or, if inseminated, diapausing eggs, the advantage of a higher male‐female encounter rate is that allocation to male production can be lower. This is paradoxical in the context of the sex allocation theory developed for rotifers, as the theory predicts equal numbers of male-producing and diapausing-egg producing females. We investigated this paradox using both empirical data and theoretical analysis. L…
Testis asymmetry in birds: the influences of sexual and natural selection
2014
Gonad size and shape asymmetries are particularly common in birds. Although some obvious size and shape differences between the left and right testes in birds were first documented more than a century ago, little is known about what influences the variation across species in either the degree or the direction of these asymmetries. Here we show that a left bias in size is the most likely ancestral state in most orders and families, and that there is a weak but significant negative relation between the degree of size and shape asymmetries. In extant species, testis size and shape symmetries increase with the degree of sperm competition (relative testes mass), but those relations are significa…
Should the teaching of biological evolution include the origin of life?
2010
The development of mainstream research on the origin of life as an outcome of Darwinian evolution is discussed. It is argued that prebiotic evolution and the origin of life should not be excluded from the syllabus and should be part of classes on biological evolution, and that the transition from non-living to living matter is best understood when seen as part of evolutionary biology. The wide acceptance of evolutionary approaches to the study of the emergence of life in European and Latin American countries is discussed.
Morphological variation of the Oncocyclus irises (Iris: Iridaceae) in the southern Levant
2002
Morphological traits of Iris section Oncocyclus (Siems.) Baker in the southern Levant (Israel, Jordan, The Palestinian Authority and Sinai/Egypt) were analysed in order to clarify taxonomic relationships among taxa and the validity of diagnostic characters. Floral and vegetative characters were measured in 42 populations belonging to nine species during the peak of the flowering season in 1998‐2000. Pearson’s Coefficient of Racial Likelihood (CRL) was used to calculate morphological distances between populations. Twelve of the measured populations, distributed along the north-south aridity gradient in Israel, were further explored for morphological changes along the gradient. Cluster analys…
Productivity increases with variation in aggression among group members in Temnothorax ants
2011
Social insect societies are characterized not only by a reproductive division of labor between the queen and workers but also by a specialization of workers on different tasks. However, how this variation in behavior or morphology among workers influences colony fitness is largely unknown. We investigated in the ant Temnothorax longispinosus whether aggressive and exploratory behavior and/or variation among nest mates in these behavioral traits are associated with an important fitness measure, that is, per worker offspring production. In addition, we studied how body size and variation in size among workers affect this colony fitness correlate. First, we found strong differences in worker b…
Rapid growth of Atlantic salmon juveniles in captivity may indicate poor performance in nature
2011
Abstract The hatchery environment often favours completely different traits than natural selection in the wild. Consequently, hatchery-reared fish are usually larger and more aggressive than their wild counterparts. Increased growth rate and aggression are predicted to be beneficial in feeding competition in hatcheries, but not necessarily in nature, where food resources are spatially and temporally more variable. We compared the growth, condition and mortality of landlocked Atlantic salmon (Salmo salar L.) juveniles in a common hatchery environment and when feeding on natural prey in semi-natural channels. We found that the growth and survival probability of the fish in the hatchery was ne…
Mammalian nest predator feces as a cue in avian habitat selection decisions
2012
Breeding habitat selection is expected to be adaptive. Animals should respond to strong agents of natural selection, such as expected offspring mortality due to nest predators, in their settlement decisions. In birds, mammalian nest predators are a significant mortality source and birds are known to respond to their presence. However, the mechanism used by birds to perceive mammalian nest predators and estimate the nest predation risk remains unknown, in particular at larger spatial scales while comparing potential breeding habitat patches. We experimentally tested whether the farmland bird community can detect and perceive cues of a mammalian nest predator (urine and feces), and how this p…