Variability in grape phylloxera preference and performance on canyon grape (Vitis arizonica).

Area of Science:

• Ecology
• Evolutionary Biology
• Entomology

Background:

• The deme-formation hypothesis suggests that sessile organisms adapt to local resources.
• Grape phylloxera (Daktulosphaira vitifoliae) are sessile, parthenogenetic herbivores feeding on grapevines (Vitis spp.).
• Understanding adaptation in herbivores is crucial for agricultural and ecological management.

Purpose of the Study:

• To experimentally test the deme-formation hypothesis in grape phylloxera populations.
• To investigate host preference and performance of phylloxera on different canyon grape (Vitis arizonica) genotypes.
• To determine the influence of host genotype and environmental factors on phylloxera adaptation.

Main Methods:

• Conducted experiments with four phylloxera populations and canyon grape hosts.
• Assessed phylloxera preference by measuring galled leaves.
• Evaluated performance through gall colonization, survivorship, and fecundity.
• Examined host clone x water treatment interactions in a second experiment.

Main Results:

• Phylloxera populations did not significantly prefer their original host.
• Significant effects of herbivore population, host, and population x host interactions were observed.
• Host genotype influenced phylloxera survivorship, but not always on the original host.
• Environmental factors (water treatment) interacted with host genotype, affecting survivorship and fecundity.
• No correlation found between field infestation levels and experimental susceptibility, indicating inherent host resistance.

Conclusions:

• The study's findings do not support the deme-formation hypothesis for grape phylloxera.
• Host genotype by environment interactions appear to prevent local adaptation to specific host genotypes.
• Ecological and evolutionary dynamics of herbivore-plant interactions are complex and influenced by multiple factors.