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Preferred Plant Species (prefer + plant_species)

Distribution by Scientific Domains
Life Sciences100%
Distribution within Life Sciences
Ecology & Organismal Biology50%

Selected Abstracts

Browsing in a heterogeneons savanna

ECOGRAPHY, Issue 5 2000
C. Skarpe
Large herbivores generally depend on and interact with a food resource that is heterogeneous at different spatial scales. Plants allocate resources to rapid growth or to defence mechanisms depending on the availability of resources relative to loss of resources from herbivory. Herbivores select food and feeding habitats in order to maximize intake rate of nutrients and digestible energy, while avoiding chemical and structural deterrents. To optimize foraging, herbivores select habitats and food items in a hierarchical way, and different attracting and deterring factors may govern selection at different scales. We studied the impact of twig biting by a guild of indigenous browsers in three vegetation types in a semi-arid savanna in Botswana. The heaviest browsing pressure was in the vegetation type richest in preferred plant species, although that type was also richest in defended species. There were large differences in relative utilization between plant species, and ranking of species was roughly similar in the different vegetation types. Browsing pressure varied between species from almost 0-30%. Overall, spinescent trees were less browsed than non-spinescent ones, and evergreen species were less browsed than deciduous ones. In two of the three vegetation types there was a negative correlation between browsing pressure on a species and its frequency. There was a high incidence of rebrowsing, and once a tree had been browsed, the probability that it would be browsed again increased. The results largely agree with predictions based on the resource availability hypothesis, the scarcity accessibility hypothesis and recent theories on the significance of plant defences and on plant's response to browsing and the subsequent response by herbivores on the plant's responses. [source]

Local floral composition and the behaviour of pollinators: attraction to and foraging within experimental patches

ECOLOGICAL ENTOMOLOGY, Issue 5 2010
AMPARO LÁZARO
1. Understanding how foraging decisions take place at the local scale is relevant because they may directly affect the fitness of individual plants. However, little is known about how local diversity and density affect the foraging behaviour of most pollinator groups. 2. By introducing two potted plant species (Salvia farinacae and Tagetes bonanza) into two populations of Taraxacum officinale, we investigated how plant identity, the mixtures of these plant species, and total plant density affected the attraction to and the foraging within a patch for six pollinator groups. 3. The foraging behaviour was mainly driven by the availability of the preferred plant species, and secondly by patch diversity and density. In general, dense patches and those containing the three-species mixture were preferred by all insect groups for arrival, although muscoid and hover flies responded less to local floral composition than bees. Local diversity and density had, however, a weaker effect on foraging behaviour within patches. Site dependence in response to floral treatments could be attributable to differences between sites in pollinator assemblage and Taraxacum density. 4. Studies like ours will help to understand how foraging decisions occur at the local scale and how foraging patterns may differ between pollinators and sites. [source]

Searching and oviposition behavior of a mymarid egg parasitoid, Anagrus nigriventris, on five host plant species of its leafhopper host, Circulifer tenellus

ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2000
A.K. Al-Wahaibi
Abstract Searching and oviposition behavior and parasitization ability of Anagrus nigriventris Girault (Hymenoptera: Mymaridae), an egg parasitoid of beet leafhopper, Circulifer tenellus (Baker) (Homoptera: Cicadellidae), were examined on five host plant species of beet leafhopper: sugar beet (Beta vulgaris L.), red stem filaree (Erodium cicutarium[L.]), peppergrass (Lepidium nitidum Nuttall), desert plantain (Plantago ovata Forsskal), and London rocket (Sisymbrium irio L.). Beet leafhopper embeds its eggs in the tissues of these plant species. For each plant species, A. nigriventris behavior was examined on plants with and without beet leafhopper eggs. Experimental design was a 5 (plant species) by 2 (host eggs present/absent) factorial. Additionally within each treatment, parasitoid behavior was observed over a 22-h period at five different observation periods: t=0, 3, 6, 9, and 22 h where t=0 h represents initial exposure of the insect with the plant. The behavioral events observed were: ,fast walking' (general searching), ,slow walking' (intensive searching), ovipositor probing, grooming, feeding, and resting. Significant differences (,=0.05) among plant species in time spent on the plant, percentage of host eggs parasitized, and behavioral variables associated with intensive searching and oviposition all indicated that the plant species fell into two groups: ,preferred' plants (sugar beet, London rocket, and peppergrass), and ,unpreferred' plants (filaree and plantago). These variables also indicated that the parasitoids spent more time on, searched more, probed more, and oviposited more in plants with host eggs than plants without host eggs. Consistent effects of time (over the observation periods from t=0 to t=22 h) generally were detected only in the preferred plant species that had host eggs present. In these cases, intensive searching and probing decreased as time advanced, while variables related to general searching (,fast walking') and abandoning host egg patches (leaving the plant) tended to increase over time. [source]

Levels of aloe mortality with and without elephants in the Thicket Biome of South Africa

AFRICAN JOURNAL OF ECOLOGY, Issue 2 2009
D. M. Parker
Abstract Studies concerning the influence of African elephants (Loxodonta africana) on vegetation have produced contradictory results; some show minimal or no effect while others report significant elephant-induced effects. Elephants are generalist megaherbivores but will selectively feed from preferred plant species. We investigated the mortality of aloe plants (highly preferred food items for elephants) at five sites with elephants (treatment) and five paired sites without elephants (control) in the Eastern Cape Province of South Africa. A significantly higher proportion of aloes were dead at treatment sites and significantly more aloes that had lost their crown (headless) were found at treatment sites compared with controls. We conclude that although the proportions of dead aloes at treatment sites were significantly higher, it remains unclear whether there is a need to be concerned with the potential small-scale extinction of aloes from parts of the Eastern Cape Province. The observed mortality may merely be an artefact of the loss of large herbivores through disease (e.g. rinderpest) and hunting in the past. Résumé Des études de l'influence des éléphants africains (Loxodonta africana) sur la végétation ont produit des résultats contradictoires: certaines montrent un effet minimal, voire nul, alors que d'autres signalent des effets significatifs. Les éléphants sont des grands herbivores généralistes, mais ils se nourrissent sélectivement de certaines parties des plantes. Nous avons étudié la mortalité de plants d'aloès (nourriture fortement privilégiée par les éléphants) à cinq sites avec éléphants (traitement) et à cinq autres sites sans éléphant (témoins), dans la Province du Cap oriental, en Afrique du Sud. Il y avait une proportion significativement plus grande d'aloès morts dans les sites du traitement, et ils étaient significativement plus nombreux à avoir perdu leur couronne (étêtés) que dans les sites témoins. Nous concluons que, bien que la proportion d'aloès morts soit significativement plus grande dans les sites du traitement, il n'est pas évident de savoir s'il faut s'inquiéter de cette possible extinction à petite échelle des aloès dans certaines parties de la Province du Cap oriental. La mortalité observée peut bien être simplement un artefact de la perte des grands herbivores en raison de maladies (ex. la peste bovine) et de la chasse dans le passé. [source]