Abstract
Animal movement and behaviour is fundamental for ecosystem functioning. The process of seed dispersal by frugivorous animals is a showcase for this paradigm since their behaviour shapes the spatial patterns of the earliest stage of plant regeneration. However, we still lack a general understanding of how intrinsic (frugivore and plant species traits) and extrinsic (landscape features) factors interact to determine how seeds of a given species are more likely to be deposited in some places more than in others. We develop a multi-species mechanistic model of seed dispersal based on frugivore behavioural responses to landscape heterogeneity. The model was fitted to data from three-years of spatially-explicit field observations on the behaviour of six frugivorous thrushes and the fruiting patterns of three fleshy-fruited trees in a secondary forest of the Cantabrian range (N Spain). With such model we explore how seed rain patterns arise from the interaction between animal behaviour and landscape heterogeneity. We show that different species of thrushes respond differently to landscape heterogeneity even though they belong to the same genus, and that provide complementary seed dispersal functions. Simulated seed rain patterns are only realistic when at least some landscape heterogeneity (forest cover and fruit abundance) is taken into account. The common and simple approach of re-sampling movement data to quantify seed dispersal produces biases in both the distance and the habitat at which seeds arrive. Movement behaviour not only affects dispersal distance and seed rain patterns but also can affect frugivore diet composition even if there is no built-in preference for fruiting species. In summary, the fate of seeds produced by a given plant species is strongly affected by both the composition of the frugivore assemblage and the landscape-scale context of the plant location, including the presence of fruits from other plants (from the same or different species).
Highlights
The role of animals as vectors linking ecological processes between habitat patches across space and time [1] derives from the idea that their movement and behaviour cascade into key ecosystem functions [2,3]
We still lack a general understanding of how intrinsic and extrinsic factors interact to determine whether seeds of a given species are more likely to be deposited in some places rather than in others
For the less abundant T. pilaris and T. torquatus model selection favoured the exclusion of either fruit abundance or cover as factors affecting movements (Table S4.2 in Text S4)
Summary
The role of animals as vectors linking ecological processes between habitat patches across space and time [1] derives from the idea that their movement and behaviour cascade into key ecosystem functions [2,3] Among these processes, seed dispersal by frugivorous animals is is perhaps the best studied and most emblematic. Frugivore movement is highly contingent on the abundance and distribution of fruit resources [7,8,9] and other landscape features such as the availability and arrangement of different habitats [10,11,12] Ignoring these effects of landscape heterogeneity in animal movements could lead to oversimplified views of seed dispersal, implying very different demographic projections for plant populations [9,13,14] than those empirically experienced in real systems
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