9 research outputs found
Contrasting resource allocation patterns in Sedum lanceolatum Torr.: Biomass versus energy estimates
Biomass determinations and microbomb calorimetry were used to assess resource allocation in Sedum lanceolatum Torr. between 2,257 and 3,726 m above sea level in the Front Range of the Rocky Mountains, Colorado, USA. In general, energy values did not differ within a tissue among sites, but did differ among tissue types. Flowers and leaves had the greatest energy content per gram ashfree dry weight. Total kilojoules per plant were homogeneous along the elevational gradient.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47753/1/442_2004_Article_BF00379785.pd
Inbreeding depression and partial selfing: evolutionary implications of mixed-mating in a coastal endemic, Silene douglasii var. oraria (Caryophyllaceae)
Evidence for paternal transmission and heteroplasmy in the mitochondrial genome of Silene vulgaris, a gynodioecious plant
Seed weight increases with altitude in the Swiss Alps between related species but not among populations of individual species
Nectar sugar production across floral phases in the gynodioecious protandrous plant Geranium sylvaticum
Many zoophilous plants attract their pollinators by offering nectar as a reward. In gynodioecious plants (i.e. populations are
composed of female and hermaphrodite individuals) nectar production has been repeatedly reported to be larger in
hermaphrodite compared to female flowers even though nectar production across the different floral phases in
dichogamous plants (i.e. plants with time separation of pollen dispersal and stigma receptivity) has rarely been examined. In
this study, sugar production in nectar standing crop and secretion rate were investigated in Geranium sylvaticum,
a gynodioecious plant species with protandry (i.e. with hermaphrodite flowers releasing their pollen before the stigma is
receptive). We found that flowers from hermaphrodites produced more nectar than female flowers in terms of total nectar
sugar content. In addition, differences in nectar production among floral phases were found in hermaphrodite flowers but
not in female flowers. In hermaphrodite flowers, maximum sugar content coincided with pollen presentation and declined
slightly towards the female phase, indicating nectar reabsorption, whereas in female flowers sugar content did not differ
between the floral phases. These differences in floral reward are discussed in relation to visitation patterns by pollinators
and seed production in this species.peerReviewe
Is Race- and Sex-Based Targeting Efficient? A Closer Look at Tort Law's Discriminatory Damage Awards
Seed germination of gynodioecious species: theoretical considerations and a comparison of females and hermaphrodites
Life-History Responses to the Altitudinal Gradient
We review life-history variation along elevation in animals and plants and illustrate its drivers, mechanisms and constraints. Elevation shapes life histories into suites of correlated traits that are often remarkably convergent among organisms facing the same environmental challenges. Much of the variation observed along elevation is the result of direct physiological sensitivity to temperature and nutrient supply. As a general rule, alpine populations adopt ‘slow’ life cycles, involving long lifespan, delayed maturity, slow reproductive rates and strong inversions in parental care to enhance the chance of recruitment. Exceptions in both animals and plants are often rooted in evolutionary legacies (e.g. constraints to prolonging cycles in obligatory univoltine taxa) or biogeographic history (e.g. location near trailing or leading edges). Predicting evolutionary trajectories into the future must take into account genetic variability, gene flow and selection strength, which define the potential for local adaptation, as well as the rate of anthropogenic environmental change and species’ idiosyncratic reaction norms. Shifts up and down elevation in the past helped maintain genetic differentiation in alpine populations, with slow life cycles contributing to the accumulation of genetic diversity during upward migrations. Gene flow is facilitated by the proximity of neighbouring populations, and global warming is likely to move fast genotypes upwards and reduce some of those constraints dominating alpine life. Demographic buffering or compensation may protect local alpine populations against trends in environmental conditions, but such mechanisms may not last indefinitely if evolutionary trajectories cannot keep pace with rapid changes.Peer reviewe