Endangered plant-parrot mutualisms: seed tolerance to predation makes parrots pervasive dispersers of the Parana pine

Abstract

Parrots are largely considered plant antagonists as they usually destroy the seeds they feed on. However, there is evidence that parrots may also act as seed dispersers. We evaluated the dual role of parrots as predators and dispersers of the Critically Endangered Parana pine (Araucaria angustifolia). Eight of nine parrot species predated seeds from 48% of 526 Parana pines surveyed. Observations of the commonest parrot indicated that 22.5% of the picked seeds were dispersed by carrying them in their beaks. Another five parrot species dispersed seeds, at an estimated average distance of c. 250 m. Dispersal distances did not differ from those observed in jays, considered the main avian dispersers. Contrary to jays, parrots often dropped partially eaten seeds. Most of these seeds were handled by parrots, and the proportion of partially eaten seeds that germinated was higher than that of undamaged seeds. This may be explained by a predator satiation effect, suggesting that the large seeds of the Parana pine evolved to attract consumers for dispersal. This represents a thus far overlooked key plant-parrot mutualism, in which both components are threatened with extinction. The interaction is becoming locally extinct long before the global extinction of the species involved.

Seed‐dispersal interactions in fragmented landscapes – a metanetwork approach

“…; Tella et al . ; García & Borda‐de‐Água ). Diet‐generalist, small‐sized bird species contribute effectively to the seed‐rain of pristine‐forest species in rare events of dispersal among tropical forest fragments (Carlo & Morales ).…”

“…Nonetheless, rare events of seed-dispersal can also contribute to species movement and gene flow in fragmented landscapes (Nathan 2006;Jordano et al 2007;Sekercioglu et al 2007;Tella et al 2016;Garc ıa & Borda-de-Agua 2017). Diet-generalist, small-sized bird species contribute effectively to the seed-rain of pristine-forest species in rare events of dispersal among tropical forest fragments (Carlo & Morales 2016).…”

Incorporating the effects of generalist seed predators into plant community theory

“…) or bird (Tella et al . ) dispersal. Yet, the process of caching creates additional filters to seed survival (Lichti, Steele & Swihart ), and discerning what fraction of dispersed or cached seeds germinate and how this compares to the fraction of non‐dispersed seeds that germinate remains a poorly explored area of seed dynamics (but see Horvitz & Schemske ; Vander Wall ; Longland et al .…”

The relationship between forest fragmentation and the potential geographical distribution of psittacids (Psittaciformes: Psittacidae) in the Yucatan Peninsula, Mexico

“…Nonetheless, parrots are highly mobile species able to move among forest patches (Renton, 2001), therefore studies of fragmentation effects on birds at the patch level may not be applicable to parrots. However, parrots can be affected by changes that occur in the characteristics of their habitats and their extension, even if they can move among distant forest patches (Tella et al, 2016). Different species of parrots and parakeets select areas with a high proportion of forest, and avoid areas with low forest cover (Legault, Chartendrault, Theuerkauf, Rouys, & Barre, 2011).…”