Ize, Density, Ecological Groups, and Dispersal Syndromes of the Seed Rain in Urban Atlantic Forest Fragments in Northeastern Brazil

Abstract

Urban expansion has been one of the main factors contributing to the reduction and fragmentation of tropical forests, and such urban green areas are crucial for conserving and maintaining local and regional biodiversity. This study assessed different aspects of the seed rain (seed size, seed density, dispersal syndromes, ecological groups) in two urban Atlantic Forest fragments (Jardim Botânico -11 ha / Mata do Curado -106 ha) in Recife, northeastern Brazil. We expected that i) the connectivity and large size would reduce the floristic homogenization in Mata do Curado, ii) the continuous human presence would increase the abundance of non-shaded tolerant species, and iii) in the Jardim Botânico the absence of connectivity and small size would reduce the abundance of shade-tolerant species (large seeds). A total of 50 fruit traps were maintained for 12 months at each site, and visits were performed fortnightly to collect seeds. The collected seeds were quantified, measured (length and width), and categorized into dispersal syndromes (zoochoric, anemochoric, autochoric) and ecological groups (shade and non-shade tolerant). 4,621 seeds were collected in the traps across the study period (Jardim Botânico: 1,778; 7 spp. / Mata do Curado: 2,843; 8 spp. plus 18 morphotypes). Overall, large seeds (15.1 mm -30 mm) were more abundant in the Jardim Botânico. Zoochoric seeds were longer in length and width in the Mata do Curado. As expected, connectivity and size appeared to contribute to the decrease of floristic homogenization, and human presence increased the abundance of non-shade tolerant seeds in the Mata do Curado. In contrast, albeit small and isolated, the Jardim Botânico demonstrated a higher abundance of shade-tolerant seeds. Our results reinforce the urgency of preserving urban forests to conserve regional biodiversity.