Secondary seed dispersal systems, frugivorous lizards and predatory birds in insular volcanic badlands

Abstract

Summary1. Secondary seed dispersal occurs whenever a seed is dispersed in two or more different dispersal events, so that different dispersal agents (e.g. animal frugivores or invertebrates) contribute to different events. Three secondary seed dispersal systems, in which lizards and predatory birds participate, are studied in Lanzarote (Canary Islands). 2.Seeds from all three plant species studied ( Lycium intricatum , Rubia fruticosa and Asparagus nesiotes ) were found with the remains of lizards ( Gallotia atlantica ) when they appeared inside shrike ( Lanius meridionalis ) and kestrel ( Falco tinnunculus ) pellets. This suggests that these two avian predators might secondarily disperse these plants by incidentally ingesting seeds when they prey upon the frugivorous lizards. 3. Lycium and Rubia seeds dispersed by Falco had significantly thinner seed coats compared to the other treatments ( Gallotia and Lanius ) and to uningested seeds. Correlated with this result, seed hardness increased from Lycium (the softest coat), to Rubia (intermediate values), to Asparagus. 4. Seed viability was high in all three species, although both viability and germination were significantly reduced in seeds of Lycium and Rubia dispersed by Falco . 5. The seed distribution was markedly different, Gallotia being an important disperser in the open ground microhabitats, Lanius in hillocks and Falco in hills. Because all three plant species were present in all these microhabitats, our observations suggest that the dispersal of these plants might be associated with the differential use of the habitat by the different dispersers. 6. Synthesis: Contrary to some long-distance seed dispersal (LDD) paradigms, the complex seed dispersal systems we describe are common and affect an important number of seeds that are moved each year to particular microhabitats. Finally, the simultaneous ecological factors analysed in this study support the hypotheses that diplochory by double endozoochory could have played a more important role in LDD events than is currently recognized, both in recent volcanic areas (lowlands) and also probably in the colonization of other subtropical islands.

The unnoticed effect of a top predator on complex mutualistic ecological interactions

“…owls, shrikes or kestrels) frequently prey on frugivorous lizards and disperse seeds already consumed by them (Grant et al 1975;Nogales et al 2002Nogales et al , 2007. Saurochory is such an important means of plant dispersal on many tropical and subtropical islands (Valido and Olesen 2007;Heleno et al 2011) that, in some high-profile cases, such as the Canary Islands, more than 70 % of fleshy-fruited plant species (&80 spp in the total archipelago) are dispersed by lizards (Valido 1999).…”

Predicting species' maximum dispersal distances from simple plant traits

“…Dispersal syndrome may generally be deduced from seed morphology, which is assumed to facilitate dispersal by a specific vector (e.g., animals, wind, water [Hughes et al 1994, Thomson et al 2010). However, a multiplicity of vectors, as well as variation in the behavior of these vectors, makes it difficult to establish a direct association between dispersal syndrome and long-distance dispersal (Nogales et al 2007). Even within a single dispersal syndrome, dispersal distances vary in magnitude (e.g., Augspurger 1986, Vittoz and Engler 2007, Muller-Landau et al 2008, Thomson et al 2011.…”

The potential of seed‐eating birds to spread viable seeds of weeds and other undesirable plants

“…Seeds can also be spread secondarily by predators which ingest seeds with their prey, and then pass viable seed (Dean & Milton 1988;Nogales et al 2002Nogales et al , 2007.…”