Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Doctorat → États-Unis → 2008 → Gall morphology and the effects of host plant water status on the Asphondylia auripila group on Larrea tridentata in the Mojave Desert, Granite Mountains, California

University of California, Los Angeles (2008)

Gall morphology and the effects of host plant water status on the Asphondylia auripila group on Larrea tridentata in the Mojave Desert, Granite Mountains, California

Huggins, Thomas Roy

Titre : Gall morphology and the effects of host plant water status on the Asphondylia auripila group on Larrea tridentata in the Mojave Desert, Granite Mountains, California

Auteur : Huggins, Thomas Roy

Université de soutenance : University of California, Los Angeles

Grade : Doctor of Philosophy (PhD) 2008

Résumé
This dissertation is comprised of four studies about gall morphology and distribution in the Asphondylia auripila group (Diptera : Cecidomyiidae) on the desert shrub Larrea tridentata (Zygophyllaceae). Gall morphology in the Asphondylia auripila group is diverse and species specific. To explain this interspecific variation in gall morphology I introduce a "microclimate hypothesis" that proposes that gall morphologies represent unique adaptations to the abiotic properties or microclimate of a gall’s habitat. My results demonstrate that (1) galls in the auripila group have species-specific distributions within and between four discrete plant surfaces, (2) galls have discrete species-specific morphologies, but may be categorized into three gross morphological types, and (3) gall morphological types are more or less consistent within plant surfaces. Using plant morphology as a model for gall adaptation, variation in gall morphology such as SGA, surface area, and pubescence parallel well documented morphological plant adaptations in and environments, suggesting that microclimatic conditions associated with gall substrates may explain interspecific differences in gall morphology.
The relationship between plant water status and Asphondylia gall densities was also investigated. Improvements in plant water status due to increased precipitation were associated with community-wide declines in gall density, a result consistent with previous studies. Within the general decline in gall density, individual gall species behaved more or less independently. Ecologically sensitive galls responded robustly to relatively short-term interannual changes in plant water status. Gall species may be considered mesophyllic or xerophyllic based on the nature of their response to plant water status, their phenologies, as well as their response to plant characteristics associated with water status. During an experimental manipulation, galls again responded negatively to increases in plant water status. Total gall density was negatively correlated with stem water content and plant growth, but not correlated with meristem density. These results did not support the meristem hypothesis, which proposes that decreases in plant water status increase meristem density, which increases oviposition opportunities for gall-makers. Because gall density was strongly correlated with plant growth measured as node production, hypotheses based on plant growth rather than meristem density better explain the results of this study.

Search Oxford Libraries Online (SOLO)

ProQuest Dissertations Publishing

Page publiée le 13 mai 2011, mise à jour le 4 décembre 2018