Effects of forest age on fruit composition and removal in tropical bird-dispersed understorey trees

Abstract

Abstract:Little is known about how land-use changes affect interspecific interactions such as fruit–frugivore mutualisms. Forest age could affect both fruit sugar concentrations via differences in light availability or disperser abundance, and fruit removal rates via differences in bird and plant community composition. We examined how these two factors are affected by forest age in a Costa Rican rain forest. We compared seven young-secondary forest species, seven old-growth forest species, andMiconia nervosagrowing in both forests. We measured sugar concentrations in fruits and manipulated the location of paired fruiting branches, measuring subsequent fruit removal. Sugar concentration means were on average 2.1 percentage points higher in young-secondary forest species than in old-growth forest species, but did not differ amongMiconia nervosafruits from the two forests. Fruit removal rates were higher in young-secondary forest for 86% of young-secondary forest species, 71% of old-growth forest species, and on average for both young-secondary and old-growth forestMiconia nervosaindividuals. Higher sugar concentrations in young-secondary forest plants could reflect stronger competition for dispersers, while experimental fruit removal results suggests the opposite patterns of competition; fruits are more likely to be removed by dispersers in young-secondary forest independent of fruit nutrient concentration.

Storms drive altitudinal migration in a tropical bird

“…Higher-elevation breeding sites receive double the rainfall of lowland non-breeding sites and Whiteruffed Manakins primarily consume low-fat, low-protein, watery fruits (approx. 7% sugar; Lumpkin & Boyle 2009) leading to high food intake rates (Boyle 2009). Sexrelated differences in migratory tendency are consistent with the LFO hypothesis because males are 15 per cent smaller than females.…”

The Caribbean Lowland Evergreen Moist and Wet Forests

“…Forests of differing ages contain floristic differences that may also affect frugivory and seed dispersal by birds. Overall sugar concentrations of fruits found in secondary lowland forests are higher than those of fruits in primary forests, which results in faster fruit removal rates by birds in secondary habitats, although proportions of fruit removal do not differ among forests (Lumpkin and Boyle 2009).…”