Seed dispersal by a frugivorous marsupial shapes the spatial scale of a mistletoe population

Abstract

Summary 1.Seed dispersal is considered critical for shaping the spatial structure of plant populations, though little empirical effort has been made to interpret this effect in terms of the scale at which plant species are distributed and cope with environmental heterogeneity. We assessed the spatial role of seed dispersal in Tristerix corymbosus , a mistletoe dispersed exclusively in the temperate forests of Patagonia by the endemic marsupial Dromiciops gliroides . 2. We examined how fruit resource tracking and seed dispersal by the marsupial affects mistletoe recruitment, employing a spatially explicit approach aimed at breaking down the spatial structure of the mistletoe and marsupial populations at different scales. 3. In a single fruiting season, we evaluated the abundance of mistletoe fruits, adult plants, dispersed seeds and recruits (seedlings and saplings), as well as the abundance of marsupials, along a 1500-m linear transect. 4. Both mistletoe and marsupial abundances were distributed hierarchically in space, with large patches containing smaller ones. Marsupial patchiness matched that of mistletoe fruits, at least at a broad scale within the transect. Marsupial abundance also varied at a large-scale, being conditioned by habitat features and decreasing progressively along the transect. Mistletoe seed rain accounted for the patchiness of adult plants and fruits, and for the large-scale pattern of marsupial activity. The spatial pattern of mistletoe recruitment closely matched seed rain. 5. Synthesis. Seed dispersal by marsupials shaped the scale of mistletoe recruitment in two ways. First, marsupials created a spatial match between mistletoe adults and recruits as a result of fruit resource tracking. Second, they generated patchiness in mistletoe offspring at a larger scale than in adults. Dispersal process performed as a strong demographic filter capable of changing the mistletoe spatial structure from adults to recruits, despite a low frequency of far-from-adult dispersal events. Similar effects of scale shaping by seed dispersers may be generalized among plants in which there is a sharp spatial match between fruits and frugivores, and whose dispersed seeds have a higher probability of recruiting than undispersed ones.

Ecology of neotropical mistletoes: an important canopy-dwelling component of Brazilian ecosystems

“…Th e global seed dispersers of Viscaceae and Loranthaceae are primarily birds; the only exception is Tristerix corymbosus (L.) Kuijt, which is dispersed by an endemic marsupial (Dromiciops gliroides -Microbiotheriidae) in Argentina (Amico & Aizen 2000;García et al 2009). Birds may disperse Viscaceae seeds via endozoocory or epizoocory (Arceuthobium in North America), whereas only endozoochory has been observed for Loranthacae.…”

Local and landscape-scale biotic correlates of mistletoe distribution in Mediterranean pine forests

“…Seed dispersal by frugivorous animals is responsible for the distribution of various plant species , and in particular of mistletoes (Aukema, 2004;García et al, 2009). There is not scientificallyproven evidence of the influence of birds on the distribution of mistletoes in our study area, but the importance of the percentage of area covered with Olive orchards suggests that the occurrence of mistletoes on P. halepensis could be highly influenced by the ecology of its main dispersers.…”

“…Mistletoe presence is constrained at different spatial scales by a wide range of factors, including the abiotic limitations of temperature and water availability on mistletoe growth (Zuber, 2004), the biotic specificity regarding the host type and quality (de Buen et al, 2002), and landscape-scale biotic factors influencing the abundance and movement of their main bird dispersers (García et al, 2009;MacRaild et al, 2010;Rodríguez-Cabal et al, 2007). Abiotic conditions and host quality affect the availability of suitable habitats for mistletoe establishment (Watson, 2009b), while landscape properties -such as fruiting neighborhood (Carlo and Aukema, 2005), tree spatial distribution and size structure (Aukema, 2004;Kathleen, 1995)-influence the behavior of animal dispersers and modify seed deposition (Morales and Carlo, 2006).…”

Neighborhood effects on seed dispersal by frugivores: testing theory with a mistletoe–marsupial system in Patagonia

“…Intraspecific neighborhood density was measured by mapping and measuring the size (largest diameter) of all T. corymbosus plants found within a radius of 5 m from the focal plants. All plants were located in the lower forest strata at a height of 0-3 m, which is where the most common host trees (Aristotelia chilensis and Maytenus boaria) are found (Garcı´a et al 2009). …”