Gene flow between nascent species: geographic, genotypic and phenotypic differentiation within and between Aquilegia formosa and A. pubescens.

Speciation can be described as a reduction, and the eventual cessation, in the ability to interbreed. Thus, determining how gene flow differs within and between nascent species can illuminate the relative stage the taxa have attained in the speciation process. Aquilegia formosa and A. pubescens are fully intercompatible, yet occur in different habitats and have flowers specialized for pollination by hummingbirds and hawkmoths, respectively. Using 79 SNP loci, we genotyped nearly 1000 individuals from populations of both species in close proximity to each other and from putative hybrid zones. The species shared all but one SNP polymorphism, and on average, allele frequencies differed by only 0.14. However, the species were clearly differentiated using Structure, and admixed individuals were primarily identified at putative hybrid zones. PopGraph identified a highly integrated network among all populations, but populations of each species and hybrid zones occupied distinct regions in the network. Using either conditional graph distance (cGD) or Fst/(1-Fst), we found significant isolation by distance (IBD) among populations. Within species, IBD was strong, indicating high historic gene flow. IBD extended approximately 100 km in A. pubescens and 30 km in A. formosa. However, IBD between the species was very weak and extended only a few km beyond hybrid zones, suggesting little recent gene flow. The extensive sharing of SNP polymorphisms between these species suggests that they are very early in the speciation process while the low signal of IBD suggests that they have largely ceased gene exchange.

Are natural hybrids fit or unfit relative to their parents?

The process of natural hybridization may produce genotypes that establish new evolutionary lineages. However, many authors have concluded that natural hybridization is of little evolutionary importance because hybrids, in general, are unfit relative to their progenitors. Deciding between these alternative conclusions requires that fitness be measured for hybrid classes and parental species. Recent analyses have found that hybrids are not uniformly unfit, but rather are genotypic classes that possess lower, equivalent or higher levels of fitness relative to their parental taxa.

Columbines: a geographically widespread species flock.

Species in the columbine genus, Aquilegia, are known for their broad variation in ecology and floral morphology. Aquilegia is also known for the large degree of intercompatibility among its species, which has led to the suggestion that the genus has arisen recently. However, intercompatibility does not always imply recent divergence and the widespread distribution pattern of the genus has suggested an older age. We constructed phylogenies for Aquilegia plus its close relatives by using nucleotide sequence data from both nuclear and chloroplast DNA. The sequence data averaged over 1250 bp per species. Among the 14 columbine species sampled from Europe, Asia, and North America only 16-bp changes and one insertion/deletion event were detected. In contrast, related genera had from 3 to 45 times this level of variation. The phylogenies derived from the chloroplast and nuclear DNA sequences were highly concordant and suggest that the columbines are the result of a recent, rapid radiation. In contrast to other examples of species flocks, Aquilegia has radiated on a widespread geographical scale. By comparison with their related taxa, we suggest that the evolution of the nectar spur in Aquilegia was a key innovation for this genus and allowed rapid speciation through specialization to specific pollinators.

Floral and ecological isolation between Aquilegia formosa and Aquilegia pubescens.

Habitat preference and pollination syndrome have been suggested as major factors in reproductive isolation among plant species. The columbine genus Aquilegia contains species that have been used as classic examples of reproductive isolation due to ecological and floral factors. In this analysis Aquilegia formosa, Aquilegia pubescens, and natural hybrid populations between these two species were assayed for genetic and morphological variation. Clinal variation was evident for three "random amplified polymorphic DNA" loci and five morphological characters along a transect extending from a lower altitude A. formosa population, through an intermediate hybrid population, to a higher altitude A. pubescens population. Similar clinal variation was also discovered for a transect that included A. formosa-like, hybrid, and A. pubescens-like populations at a single elevation. The change in the frequency of both sets of markers was closely associated with change in habitat. The molecular markers indicate the presence of bidirectional introgression between these two species. In contrast, there was apparently selection against introgression of four of the five alternate floral characters. Selection against the incorporation of floral characters from one species into the other species was suggested by the introgression of the DNA markers with little or no introgression of the four floral characters. These findings suggest the importance of adaptations associated with both pollination syndromes and habitat preference on species integrity.

An experiment in the development of empathy in student nurses.

Student nurses were assessed for their specific interview behaviour with patients after experiencing an empathetic training and a psychological-mindedness experience. The results show that empathy was not increased or decreased. The reasons for the experimental findings are discussed.

Individual learning styles of student nurses, their teachers and ward sisters.

This paper presents a brief description of an experiential learning theory, which provides a model of learning and adaptation processes consistent with the structure of human cognition and the stages of human growth and development. It conceptualizes the learning process in such a way that differences in individual learning styles and corresponding learning environments can be identified. Sixty-two student nurses, 10 nurse teachers and 15 ward sisters completed a learning style inventory. No significant differences were detected. Learning style differences are discussed.