Does nectar production reduce herbivore pressure on Passiflora species (Passifloraceae) in a tropical rainforest in Costa Rica?

Autor(en)

Maria Thurner, Veronika Mayer

Abstrakt

Mutualistic ant-plant associations are common and important elements of tropical ecosystems. The most common ant-plant associations are loose mutualisms due to the presence of extrafloral nectaries (EFN). Such loose mutualisms are also found in genus Passiflora. Some species develop extrafloral nectaries on the petiole, on the leaf blade and on sepals which are attractive to ants as food source.

It was suggested that the presence of foraging ants might protect the plants against herbivore attacks thus increasing the vitality and reproductive success of the plant. From some EFN bearing Passiflora species it is already known that ants help to diminuish herbivore pressure to a high degree. Differences in the structure of nectaries influence ant attendance (APPLE & FEENER 2001). Ant-activity can vary over time and space and especially rainfall has been prooved to reduced it significantly (WIRTH & LEAL 2001). Plant-attractiveness and location of the shoots in different altitudes of the forests have been found to be important for the presence of different ant species (LABEYRIE et al. 2001; HOSSAERT-MCKEY et al. 2001). It is not known whether (1) plants react on herbivore damage with differences in nectar production to attract more ants, (2) shoot growth depends on ant presence, and (3) to which degree Passifloa species with EFN rely on ants as herbivore defence.

To this aim, observations have been performed on eight different Passiflora species with EFNs in a tropical lowland rainforest in Costa Rica. The species differ in EFN number and size and the quantity of nectar production. To clarify the open questions the increase of stem length and changes in leaf area due to herbivore attacks has been measured in long term exclusion experiments with and without the precence of ants to notice probable positive effects caused by ant activity. Further ant activity without manipulation was observed for a period of 24 hours, as well as after artificial injuries, and behavioural aspects related to the different EFNs stated. Nectar production has been observed in the same way as ant activity, with and without artificial injuries to learn more about probable changes in quality and quantity of the nectar because of the damage. An important aspect of the study is the amount and quality of the nectar produced. Differences in number and structure of EFN and the amount of nectar produced in different parts of the plant may cause changes in the protective ambitions of the ants present. Development of EFNs and their health condition may influence nectar production to a high degree. Estimations and raster electronic analysis should help to find differences in the surface structure of EFN. And, finally, leaf content analyses should help to understand the necessity of ant protection, because newly grown leaves may not contain all defensive substances as adult leaves do.

Literature:

APPLE J. L. & D. H. FEENER (2001): Ant Visitation of Extrafloral Nectaries of Passiflora: the Effects of Nectary Attributes and Ant Behavior on Patterns in Facultative Ant-Plant Mutualisms. Oecologia 127: 409-416.

HOSSAERT-MCKEY M., ORIVEL J., LABEYRIE E., PASCAL L., DELABIE J. H. C. & A. DEJEAN (2001): Differential Associations With Ants of Three Co-Occurring Extrafloral Nectary-Bearing Plants. Ecoscience 8: 325-335.

LABEYRIE E., PASCAL L., DELABIE, J., ORIVEL, J., DEJEAN, A. & M. HOSSAERT-MCKEY (2001): Protection of Passiflora glandulosa (Passifloraceae) Against Herbivory: Impact of Ants Exploiting Extrafloral Nectaries. Sociobiology 38: 317-321.

WIRTH R. & I. R. LEAL (2001): Does Rainfall Affect Temporal Variability of Ant Protection in Passiflora Coccinea? Ecoscience 8: 450-453.

Organisation(en)

Externe Organisation(en)

Diözese Linz

Journal

Stapfia

Band

Seiten

599-606

ISSN

0252-192X

Publikationsdatum

2008

Peer-reviewed

ÖFOS 2012

1060 Biologie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/does-nectar-production-reduce-herbivore-pressure-on-passiflora-species-passifloraceae-in-a-tropical-rainforest-in-costa-rica(d69c49df-e666-4401-8c89-c235e1586f1d).html