1,721,312 research outputs found
Orchid diversity: an evolutionary consequence of deception?
No full textThe Orchidaceae are one of the most species-rich plant
families and their floral diversity and pollination biology
have long intrigued evolutionary biologists. About onethird
of the estimated 18 500 species are thought to be
pollinated by deceit. To date, the focus has been on how
such pollination evolved, how the different types of
deception work, and how it is maintained, but little
progress has been made in understanding its evolutionary
consequences. To address this issue, we discuss
here how deception affects orchid mating systems, the
evolution of reproductive isolation, speciation processes
and neutral genetic divergence among species. We
argue that pollination by deceit is one of the keys to
orchid floral and species diversity. A better understanding
of its evolutionary consequences could help
evolutionary biologists to unravel the reasons for the
evolutionary success of orchids
Evidence for reproductive isolate selection in Mediterranean orchids: karyotype differences compensate for the lack of pollinator specificity
No full textThe strength of reproductive isolation in hybridizing food deceptive orchids.
No full textReproductive isolation is of fundamental importance for maintaining species boundaries
in sympatry. In orchids, the wide variety of pollination systems and highly diverse floral
traits have traditionally suggested a prominent role for pollinator isolation, and thus for
prezygotic isolation, as an effective barrier to gene flow among species. Here, we examined
the nature of reproductive isolation between
Anacamptis morio
and
Anacamptis papilionacea
, two sister species of Mediterranean food-deceptive orchids, in two natural hybrid
zones. Comparative analyses of the two hybrid zones that are located on soils with volcanic
origin and have different and well-dated ages consistently revealed that all hybrid individuals
were morphologically and genetically intermediate between the parental species,
but had strongly reduced fitness. Molecular analyses based on nuclear ITS1 and (amplified
fragment length polymorphism) AFLP markers clearly showed that all examined hybrids
were F
1
hybrids, and that no introgression occurred between parental species. The maternally
inherited plastid DNA markers indicated that hybridization between
A. morio
and
A.
papilionacea
was bidirectional, as confirmed by the molecular analysis of seed families.
The genetic architecture of the two hybrid zones suggests that the two parental species easily
and frequently hybridize in sympatry as a consequence of partial pollinator overlap but
that strong postzygotic barriers reduce hybrid fitness and prevent gene introgression.
These results corroborate that chromosomal divergence is instrumental for reproductive
isolation between these food-deceptive orchids and suggest that hybridization is of limited
importance for their diversification
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Characterization of a minisatellite repeat locus in the chloroplast genome of Orchis palustris (Orchidaceae)
No full text- …
