Myiarchus flycatchers are the primary seed dispersers of Bursera longipes in a Mexican dry forest.

R Carlos Almazán-Núñez,Pablo Corcuera,María Del Coro Arizmendi,Luis E Eguiarte

doi:10.7717/peerj.2126

Abstract

We evaluated the seed dispersal of Bursera longipes by birds along a successional gradient of tropical dry forest (TDF) in southwestern Mexico. B. longipes is an endemic tree to the TDF in the Balsas basin. The relative abundance of frugivorous birds, their frequency of visits to B. longipes and the number of removed fruits were recorded at three study sites with different stages of forest succession (early, intermediate and mature) characterized by distinct floristic and structural elements. Flycatchers of the Myiarchus and Tyrannus genera removed the majority of fruits at each site. Overall, visits to B. longipes were less frequent at the early successional site. Birds that function as legitimate dispersers by consuming whole seeds and regurgitating or defecating intact seeds in the process also remove the pseudoaril from seeds, thereby facilitating the germination process. The highest germination percentages were recorded for seeds that passed through the digestive system of two migratory flycatchers: M. cinerascens and M. nutingii. Perch plants, mainly composed of legumes (e.g., Eysenhardtia polystachya, Acacia cochliacantha, Calliandra eryophylla, Mimosa polyantha), serve also as nurse plants since the number of young individuals recruited from B. longipes was higher under these than expected by chance. This study shows that Myiarchus flycatchers are the most efficient seed dispersers of B. longipes across all successional stages. This suggests a close mutualistic relationship derived from adaptive processes and local specializations throughout the distribution of both taxa, as supported by the geographic mosaic theory of coevolution.

Highlights

Biotic seed dispersal plays a central role in the spatial dynamics of plant populations (Spiegel & Nathan, 2007; Schupp, Jordano & Gomez, 2010; Jordano et al, 2010; Forget et al, How to cite this article Almazan-Nunez et al (2016), Myiarchus flycatchers are the primary seed dispersers of Bursera longipes in a Mexican dry forest
We describe the primary seed dispersal of B. longipes by frugivorous birds in a tropical dry forest (TDF) of the Balsas basin of Guerrero
The flycatcher T. verticalis remained for the longest time in the trees of the early stage (6.78 ± 1.30 min), T. vociferans in the intermediate stage (6.33 ± 1.13 min) and E. canicularis in the mature stage (8.00 ± 4.00 min; Table 1)

Summary

Introduction

Biotic seed dispersal plays a central role in the spatial dynamics of plant populations (Spiegel & Nathan, 2007; Schupp, Jordano & Gomez, 2010; Jordano et al, 2010; Forget et al., How to cite this article Almazan-Nun ̃ez et al (2016), Myiarchus flycatchers are the primary seed dispersers of Bursera longipes in a Mexican dry forest. Dispersion may encourage establishment of plants, since intraspecific competition is generally lower in sites distant from the parent plant (Godınez-Alvarez, Valiente-Banuet & Rojas-Martınez, 2002; Schupp, Milleron & Russo, 2002). In arid and semi-arid environments, biotic dispersal, germination and seedling establishment are critical phases of the plant life cycle (Valiente-Banuet et al, 1991; Godınez-Alvarez & Valiente-Banuet, 1998; Orozco-Almanza et al, 2003; Padilla & Pugnaire, 2006). Dispersers may deposit seeds in preferable microhabitats (i.e., under nurse plants) that promote germination and seedling survival (Perez-Villafana & Valiente-Banuet, 2009). The role of dispersers in depositing seeds in sites with appropriate conditions for germination in these environments is important because there are few adequate microhabitats in which seeds can be established (Vasconcellos-Neto, Barbosa de Albuquerque & Rodrigues Silva, 2009)

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