Abstract. The mutualistic breeding system involving fig trees (Moraceae, Ficus) and fig wasps (Hymenoptera, Chalcidoidea, Agaoninae) would appear so specialized that one may wonder at the evolutionary processes that could be responsible for the existence of about 750 species‐specific associations. In this paper we present data concerning two cases of species specificity breakdown between African fig trees and fig wasps. We then analyse the possible evolutionary scenarios which could be responsible, as well as the possible evolutionary outcomes of the observed situations. Our analyses range in scale from continental to habitats, and fig crops to individual figs (syconia). Habitat shifts and ecological barriers seem to be the more likely explanations for the evolution of novel fig tree‐fig wasp associations, but sympatric and parapatric scenarios cannot be ruled out.

We provide the first comprehensive inventory of the non-native plants on Madagascar since Perrier de la Bâthie's effort 80 years ago, and evaluate the characteristics and importance of this biota. Using botanical databases (especially the Tropicos Catalogue of the Vascular Plants of Madagascar), published plant lists, field observation, and relevant literature, we inventory 546 introduced species that have naturalized, as well as 611 other introduced species that only exist in cultivation. We also list 211 species with unclear status, eight native species that have had different genetic stock introduced, and three endemics that have naturalized outside their native range. Of the naturalized species, 101 display invasive behaviour. Highly represented families include Fabaceae (224 confirmed introduced species), Myrtaceae (143), Poaceae (71), Cactaceae (52), Asteraceae (50), and Solanaceae. (33). Humans have been bringing plants to Madagascar since they colonized the island, mainly for their utility. A number of plants with native varieties but which also have long histories of human use and transport are ripe for further historical biogeographical research (including Eragrostis, Panicum, Sorghum, Dioscorea, Ziziphus, and Adansonia). The introduced flora is similar in composition to other tropical regions; its numerical size appears to confirm that poorer countries experience relatively fewer plant introductions. Madagascar's introduced species deserve more attention, not just through the rubric of invasion biology, but as plants that build new ecologies and that sustain human communities. (Résumé d'auteur

On clearing fields, Ntumu farmers in southern Cameroon leave some large trees. The seed rain beneath 30 such remnant trees (12 species) was compared with that 10 m away from the edges of their crowns. Of a total of 39 765 seeds recorded in 90 seed traps over 2 y, 73.6% were of species different from the tree associated with each set of traps (‘foreign seed rain’). Seed rain included 100 morphospecies, two-thirds of which possessed endozoochorous seeds. Seeds of the pioneer tree Musanga cecropioides accounted for 71.4% of total foreign seed rain; seeds of this and other animal-dispersed species accounted for 94.5% of the total. Seed rain was 25 times higher beneath remnant trees than 10 m away. Mean species richness of monthly seed rain was three times higher beneath remnant trees than 10 m away. Both fleshy-fruited and wind-dispersed species of remnant trees attracted seed-dispersing animals which greatly enhanced the seed rain; attraction thus did not depend solely on presence of fleshy fruits. Seed rain was lower when human activity in fields was intense and increased during the period of growth of the last crops, which were not usually weeded. Heavy seed rain just before fallow may contribute significantly to regeneration, as does the presence of remnant trees.