Conflicting selection pressures on seed size: evolutionary ecology of fruit size in a bird-dispersed tree, Olea europaea

Abstract

Recent evidence indicates that fruit size has evolved according to dispersers’ size. This is hypothesized to result from a balance between factors favouring large seeds and dispersers setting the maximum fruit size. This hypothesis assumes that (1) the size of fruits that can be consumed by dispersers is limited, (2) fruit and seed size are positively correlated, and (3) the result of multiple selection pressures on seed size is positive. Our studies on the seed dispersal mutualism of Olea europaea have supported the first and second assumptions, but valid tests of the third assumption are still lacking. Here we confirm the third assumption. Using multiplicative fitness components, we show that conflicting selection pressures on seed size during and after dispersal reverse the negative pattern of selection exerted by dispersers.

The Crab-eating Fox (Cerdocyon thous) as a secondary seed disperser of Eugenia umbelliflora (Myrtaceae) in a Restinga forest of southeastern Brazil

“…Although differences between control and crab-eating fox seeds are small, fruit discrimination and dispersal of small seeds might lead to both immediate and delayed consequences to E. umbelliflora fitness. Larger seeds can aggregate more reserve tissues that improve growing and vigour of seedlings, turning them into stronger survivors and competitors under distinct environmental adversities (Leishman et al 2000, Alcántara & Rey 2003, Pizo et al 2006). Furthermore, they become more tolerant to shade, low soil moisture and nutrients, burial, and herbivory (Leishman et al 2000).…”

Variación individual en atributos de Clusia salvinii Donn. Smith asociados a la atracción de frugívoros en la dispersión de frutos y semillas

“…The study was developed in the Reserva de Nanchititla, State of Mexico (100° 15' -100° 37' WL and 18° 46' -19° Introducción La dispersión de frutos y semillas juega un papel central en la ecología y evolución de las plantas; es determinante en los estados subsecuentes del ciclo de vida de estas (Alcántara & Rey, 2003;Wang & Smith, 2002;Willson & Traveset, 2000). Algunos estudios han demostrado que ciertas características de las plantas como el tamaño y peso del fruto sirven como señales críticas para la atracción de dispersores (Alcántara & Rey, 2003;Valenta et al, 2013).…”

“…The dispersal of fruits and seeds plays an important central role in ecology and plant evolution; it is a crucial point in the subsequent states of the life cycle (Alcántara & Rey, 2003;Wang & Smith, 2002;Willson & Traveset, 2000). Some studies have shown that certain characteristics of plants, such as size and weight of the fruit, serve as critical signals to attract dispersers (Alcántara & Rey, 2003;Valenta et al, 2013).…”

“…Some studies have shown that certain characteristics of plants, such as size and weight of the fruit, serve as critical signals to attract dispersers (Alcántara & Rey, 2003;Valenta et al, 2013). According to Willson and Traveset (2000), the variance in the morphometric characteristics, such as weight of the fruit and weight of the arils, as well as the number and weight of the seeds, can have an effect on the dispersal.…”

Summer-autumn feeding ecology of Pied Flycatchers Ficedula hypolueca and Spotted Flycatchers Muscicapa striata: the importance of frugivory in a stopover area in north-west Iberia

“…Pied and Spotted Flycatchers preferred Dogwood fruits during the entire stopover period every year. Gape width and fruit size are limiting factors of the first order in seed-dispersing birds that normally swallow entire fruits (Jordano 2000, Herrera 2002, Alcántara and Rey 2003, so Blackthorn and Hawthorn fruits, with a mean length and width of generally . 10 mm (Herrera 1987, Snow andSnow 1988), were only consumed by larger bird species, with high positive selection of Blackthorn fruits by Common Blackbirds and Hawthorn fruits by Song Thrushes.…”