Implications of movement patterns of a dietary generalist for mistletoe seed dispersal

Abstract

Mistletoes are dispersed primarily by frugivorous birds and have highly aggregated distributions at multiple scales. Mistletoe specialist frugivores have been found to intensify infections within infected hosts and stands, and this is considered the most likely mechanism underlying clumped mistletoe distributions at these scales. How these patchy infections first develop and whether seed dispersers also contribute to aggregated mistletoe distributions at landscape and regional scales have not been evaluated. Here we predict the mistletoe seed shadow of a dietary generalist (spiny-cheeked honeyeater Acanthagenys rufogularis Aves: Meliphagidae), by combining our observations of movements via radio telemetry with previous data on gut passage times to estimate seed dispersal curves for individual birds. There was considerable variation in movements and inferred seed dispersal between individuals, with non-breeding birds predicted to regularly transport Amyema quandang (Santalales: Loranthaceae) seeds up to 700 m; well beyond the boundaries of an existing mistletoe infection. As the first work to consider explicitly the distance component of mistletoe seed dispersal by dietary generalists, this study poses further questions about the relative seed dispersal roles of dietary generalists and mistletoe specialists. Moreover, our findings highlight considerable intraspecific variation in movement and foraging behaviour, suggesting gender and reproductive status of birds should be considered explicitly when quantifying seed dispersal services.

Dominant network interactions are not correlated with resource availability: a case study using mistletoe host interactions

“…However, the observed distribution of mistletoe indicates a strong mechanistic explanation for the structure of this community. Other studies have found that larger trees house higher densities of mistletoes (Reid and Smith 2000, Aukema and Martinez del Rio 2002, Roxburgh and Nicolson 2008, and that spatial movements of frugivores influence dispersal of mistletoe (Murphy et al 1993, Ladley and Kelly 1996, García et al 2009, Rawsthorne et al 2011. It is likely that specific trees are preferentially selected by territorial or breeding birds (Roxburgh andNicolson 2008, Rawsthorne et al 2011), allowing neighboring trees to become highly susceptible to infection (Donohue 1995).…”

The Relative Contribution of Specialists and Generalists to Mistletoe Dispersal: Insights from a Neotropical Rain Forest

“…In Europe, North Africa, Madagascar, New Zealand, most of North America and all oceanic islands, mistletoe specialist frugivores are absent -mistletoe seeds are dispersed primarily by birds with broad diets (Watson 2004, Mathiasen et al 2008. Indeed, some of these non-specialists may be more effective in dispersing seeds beyond existing infections, their broader diet necessitating regular movement to stands and habitats without mistletoe and their longer gut passage rates allowing longer-distance dispersal (Godschalk 1985, Rawsthorne et al 2011. Indeed, some of these non-specialists may be more effective in dispersing seeds beyond existing infections, their broader diet necessitating regular movement to stands and habitats without mistletoe and their longer gut passage rates allowing longer-distance dispersal (Godschalk 1985, Rawsthorne et al 2011.…”

“…The relative contribution of seed dispersers to plant recruitment can be considered in terms of four factorsfrequency of visitation, number of seeds dispersed, quality of seed treatment and quality of seed deposition-these interacting determinants collectively defining seed disperser effectiveness (Schupp 1993, Schupp et al 2010. This unifying concept emphasizes between-disperser differences and, although more inclusive than previous frameworks for studying endozoochorous seed dispersal (Howe & Estabrook 1977, Wheelwright & Orians 1982, its application relies on an understanding of disperser movements (e.g., Rawsthorne et al 2011), the effects of seed treatment on germinability (e.g., Martìnez del Rio & Restrepo 1993), the defining attributes of safe sites for seedling establishment (Aukema 2004) and post-consumption behaviour of dispersers (e.g., Aukema & Martìnez del Rio 2004). Even when these parameters are known, variation in post-deposition factors-including seed predation, dormancy and secondary dispersal-affect seed fate and eventual plant recruitment (Forget et al 2002) making the individual importance of a specific seed disperser to the recruitment of a specific plant difficult to isolate and quantify.…”

Scale‐dependent responses of pollination and seed dispersal mutualisms in a habitat transformation scenario

“…Tristerix corymbosus was more abundant in transformed habitats (69% of the sampled mistletoes were found in transformed habitats; see Table S1), and was also found in denser aggregates than plants located in native habitat stands. Mistletoe spatial distributions are characteristically aggregated due to host and disperser effects (Medel et al 2004;Rawsthorne, Watson & Roshier 2011). In this study, transformed habitats offer favourable conditions for T. corymbosus and other fleshy-fruited plants that provide a rich mixed neighbourhood attractive to frugivores (Carlo & Morales 2008), which may result from a greater landscape complexity (Tscharntke et al 2012).…”

“…Mistletoe spatial distributions are characteristically aggregated due to host and disperser effects (Medel et al . ; Rawsthorne, Watson & Roshier ). In this study, transformed habitats offer favourable conditions for T. corymbosus and other fleshy‐fruited plants that provide a rich mixed neighbourhood attractive to frugivores (Carlo & Morales ), which may result from a greater landscape complexity (Tscharntke et al .…”