How slug herbivory of juvenile hybrid willows alters chemistry, growth and subsequent susceptibility to diverse plant enemies.

Background And Aims: Selective feeding by herbivores, especially at the seedling or juvenile phase, has the potential to change plant traits and ultimately the susceptibility of surviving plants to other enemies. Moreover, since hybridization is important to speciation and can lead to introgression of traits between plant species, differential feeding (herbivore-induced mortality) can influence the expression of resistance traits of hybrids and ultimately determine the consequences of hybridization. While it would be expected that herbivore-induced mortality would lead to greater resistance, there may be trade-offs whereby resistance to one herbivore increases susceptibility to others.

Leaf size in three generations of a dioecious tropical tree, Ocotea tenera (Lauraceae): Sexual dimorphism and changes with age.

Premise Of The Study: In dioecious species, selection should favor different leaf sizes in males and females whenever the sexes experience distinct environments or constraints such as different costs of reproduction. We took advantage of a long-term experimental study of Ocotea tenera (Lauraceae), a dioecious understory tree in Monteverde, Costa Rica, to explore leaf size differences between genders and age classes across generations.

Methods: We measured leaf size in adult trees in a natural population, in their adult F(1) offspring in two experimental populations, and in their F(2) offspring at the seedling stage.

Protein storage and root:shoot reallocation provide tolerance to damage in a hybrid willow system.

To determine the mechanistic basis of tolerance, we evaluated six candidate traits for tolerance to damage using F(2) interspecific hybrids in a willow hybrid system. A distinction was made between reproductive tolerance and biomass tolerance; reproductive tolerance was designated as a plant's proportional change in catkin production following damage, while biomass tolerance referred to a plant's proportional change in biomass (i.e.

Growth and chemical defense in willow seedlings: trade-offs are transient.

Many studies have failed to detect costs of defense and some have even found a positive correlation between growth and the concentrations of chemical defenses. These studies contradict the theoretical assumption that anti-herbivore defenses are costly-produced at the expense of growth and/or reproduction. Costs, however, may be transient and therefore difficult to detect.

Fitness and genetic architecture of parent and hybrid willows in common gardens.

Models of hybrid zone dynamics incorporate different patterns of hybrid fitness relative to parental species fitness. An important but understudied source of variation underlying these fitness differences is the environment. We investigated the performance of two willow species and their F1, F2, and backcross hybrids using a common-garden experiment with six replicated gardens that differed in soil moisture.

Plant genetic differences influence herbivore community structure: evidence from a hybrid willow system.

To determine the influence of plant genetic variation on community structure of insect herbivores, we examined the abundances of 14 herbivore species among six genetic classes of willow: Salix eriocephala, S. sericea, their F(1) and F(2) interspecific hybrids, and backcross hybrids to each parental species. We placed 1-year-old plants, grown from seeds generated from controlled crosses, in a common garden.

Seedling herbivory by slugs in a willow hybrid system: developmental changes in damage, chemical defense, and plant performance.

We evaluated feeding preference and damage by the slug, Arion subfuscus, on seedlings of two willow species, Salix sericea and S. eriocephala, and their F interspecific hybrids. Trays of seedlings were placed in the field and excised leaves were presented to slugs in choice tests.

FLUCTUATING ASYMMETRY IN A SALIX HYBRID SYSTEM: THE IMPORTANCE OF GENETIC VERSUS ENVIRONMENTAL CAUSES.

To examine the effects of hybridization and environmental stress on developmental instability, we examined fluctuating asymmetry (FA), the variance in random deviations from perfect symmetry in bilaterally symmetrical traits, for leaf symmetry in a Salix hybrid system. An abiotic environmental stress (water stress), an interspecific biotic stress (pathogen attack), and an intraspecific biotic stress (competition) were examined to determine which factors increase developmental instability. None of these three environmental stressors significantly increased FA.