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The Relative Contribution of Specialists and Generalists to Mistletoe Dispersal: Insights from a Neotropical Rain Forest
Author(s) -
Watson David M.
Publication year - 2013
Publication title -
biotropica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.813
H-Index - 96
eISSN - 1744-7429
pISSN - 0006-3606
DOI - 10.1111/j.1744-7429.2012.00905.x
Subject(s) - frugivore , generalist and specialist species , understory , biology , seed dispersal , biological dispersal , ecology , canopy , habitat , demography , population , sociology
Mistletoes rely on birds for seed dispersal, but the presumed importance of mistletoe‐specialist frugivores has not been critically examined nor compared with generalist frugivores and opportunistic foragers. The contribution of these three groups was compared directly by quantifying bird visitation to fruiting mistletoe plants ( O ryctanthus occidentalis : L oranthaceae) at B arro C olorado I sland, P anama, and by comparing these results with proportions calculated from other empirical studies of mistletoe visitation conducted elsewhere. After more than 100 h of timed watches, 23 bird species were recorded visiting eight heavily infected host trees ( L uehea seemannii : T iliaceae). Eight of these species visited mistletoe, of which five (all tyrannids) consumed mistletoe fruit. Although two mistletoe specialist frugivores ( T yrannulus elatus and Z immerius vilissimus ) removed most fruit (73%), more than a quarter was consumed by one generalist frugivore ( M ionectes oleagineus ) and two opportunists ( M yiozetetes cayanensis and M yiozetetes similis ). Post consumption behaviour varied: the specialists flew from mistletoe to mistletoe, the generalist rested in the subcanopy and understory, and the opportunists spent most time hawking insects and resting high in the canopy. Integrating these data with previous work, the dietary specialization, short gut passage rate and strict habitat preferences of mistletoe specialists suggests that their services relate primarily to intensification and contagious dispersal, while species with broader diets are more likely to visit uninfected trees and establish new infections. The presumed importance of mistletoe‐specialist frugivores was not supported and mistletoes are considered to be comparable to many other bird‐dispersed plants, relying on both specialist and generalist frugivores, while opportunists may be disproportionately important in long‐distance dispersal.