A m A

Year 1 Year 2 Year 3

c) At more than yearly intervals c) At more than yearly intervals

d) Continuous with varying intensity

Fig. 4.3.12. Patterns of flowering relating to species from a tropical rainforest in Costa Rica. (After Newstrom et al. 1991, from Bronstein 1994)

Fig. 4.3.12. Patterns of flowering relating to species from a tropical rainforest in Costa Rica. (After Newstrom et al. 1991, from Bronstein 1994)

humming birds in Ecuador occupy a region and defend it. These show the importance of assessing temporal and spatial aspects of interactions between pollinators and flowering plants.

Temporal and spatial synchronisation, particularly the very different forms of flowers and the corresponding mouth parts of insects or bills of birds, show the very close interdependence of plant and animal partners, and has often been interpreted as a result of co-evolutionary processes. The obligate linkage of many insect imagos with flowers providing nectar as their only food source supports such an interpretation.

Figures are often quoted as a remarkable example of a particularly specialised pollination system which cannot be interpreted as random. Bertin (1989) described the cycle for Ficus syco-morus (Fig. 4.3.13). The syconium, the large, almost closed inflorescence of Ficus sycomorus, has a small distal opening, the ostiulum. Females of one wasp genus, Agaonides, are attracted by the smell of the flowers and carry pollen through this opening into the inner space (only in one direction). They distribute pollen

Seed-forming, long-styled female flower

Fig inflorescence

Short-styled Long-styled female flower female flower (eventually becomes a gall)

Male flower

Female wasp Ovipositor—

^ Ostiolum ' Tunnel Mature male flowers

Male wasp emerges from gall

Fertilised female wasp emerges from gall

¥Jr\ Receptive female flowers Immature male flowers

Female wasp flies to another fig carrying pollen

Fig, 4.3.13. Ficus sycomorus and its wasp pollinators. (After Meeuse and Morris 1984, from Bertin 1989)

to the numerous individual female flowers in the inner space. In some of them, particularly those with shorter stems, they lay eggs before they die. At the same time the individual figs develop and the larvae of the fig wasp feed on the galllike growing fig tissue. First the male wasps hatch and find galls with females and fertilise them. The males die, or dig tunnels and reach the outside. The females pass through these tunnels to the outside, taking up pollen near the tunnel opening in the process, so the cycle starts again.

For such co-evolution, a common floristic and faunal history must be assumed. This also applies to herbivory, which is discussed next.

Basis of Herbivory

Herbivory is a very complex field of interaction between plants and animals. Plant are not just eaten. Herbivores influence plants in many ways, affecting their fitness and growth, including expansion of the area in which they grow and the distribution within it, as well as the composi tion, diversity, structure and dynamics of plant communities. They change the terms of competition and usually cause stress, tolerated by plants or not, but which they may counteract successfully.

For herbivory to occur, sufficient plants must be available so that animals may find them, for which they require suitable sensors. Animals will eat plants which provide them with suitable food and that are not able to protect themselves against being eaten. Sometimes whole plants are destroyed, sometimes only parts are lost which they may be able to compensate for and survive. These processes, which are simple to describe, not only occur for individual plants, but also for whole communities, where the interactions are much more complicated, particularly if the numerous feedback effects are incorporated together with the poorly understood synecological relations (Fig. 4.3.I4A,B).

The most important interactions between the supply of food from plants and the food requirements of animals are outlined in Box 4.3.2, in-

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