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Introduced and cultivated fleshy-fruited plants: consequences of a mutualistic Mediterranean plant-bird system

1990; Springer Science+Business Media; Linguagem: Inglês

10.1007/978-94-009-1876-4_26

2215-1729

Max Debussche, Paul Isenmann,

African Botany and Ecology Studies

The Montpellier region (Mediterranean France) offers 65 native taxa with fleshy fruits whose seeds are dispersed mainly by bird species. Birds also remove the fleshy fruits of non-native plant species, cultivated ones (e.g. Vitis vinifera ssp. vinifera), weeds (e.g. Phytolacca americana), garden shrubs (e.g. Pyracantha coccinea, Ligustrum ovalifolium). We report that 19 non-native plant species are dispersed by 16 bird species. Grapes constitute a very importand food item for migrating and wintering thrushes (mainly Turdus philomelos and T. iliacus) and are as important as fruits of wild plants (Juniperus sp. pl.) in their diet. Pyracantha coccinea, and subsidiarily other garden shrubs (e.g. Cotoneaster sp. pl., Ligustrum ovalifolium) attract small passerines, predominantly Blackcaps (Sylvia atricapilla), during winter and at the beginning of spring. The diet of the Blackcap, a nearly exclusive frugivorous bird in autumn and winter, shows a significant trend from native to introduced fruits from summer to early spring, as the availability in native fruits progressively becomes more scarce. At the same time their populations are concentrated in villages and suburban gardens where crops of ornamental plant species persist for a long time. On the other hand, the diet of the European Robin (Erithacus rubecula) which is less dependent on fruits, does not show the same shift and their populations do not move to more anthropic areas. We suggest that the abundant crops provided by cultivated and ornamental plants may change the migrating and wintering behaviour of the fruit dependent bird species, allowing some of them to winter in more northern or different regions than they formerly used to do. Only 6 out of 19 listed plant-species can be considered as naturalized, but no one is actually invasive. We think that this absence of invasion success must be linked with several regional features, i.e. (1) climatic stresses (frost and drought), (2) edaphic constraints (calcareous soils), (3) landscape composition (predominance of wooded areas) and (4) richness in native fleshy- fruited species which offer large crops and a wide spectrum of availability, fruit types and pulp chemical contents.