Are seeds able to germinate before fruit color ripening? Evidence from six Neotropical bird‐dispersed plant species

Abstract

Many plants attract seed dispersers and indicate the presence of ripe, fleshy fruits with coloration changes. If seed maturation is simultaneous with visual signs for frugivorous, a portion of seeds can be removed before being ready for dispersal. In this study, we tested the delay visual signal hypothesis (DVSH), which implies high reproductive success when seed maturation precedes the visual signal of the fruit ripening, limiting the dispersal of unviable seeds. We evaluated this hypothesis with six tropical species that have fruits with discrete coloration for the immature, intermediate, and mature stages, testing the prediction that the development of mature and intermediate seeds is similar. First, we verified that the coloration of three categories was differentiable with color analysis. Next, we carried out germination and viability tests (i.e., electrical conductivity [EC] and tetrazolium) as an approach to evaluate the germination potential along development. We found that the EC of three species decreased constantly during fruit ripening, suggesting that the seed maturation is a gradual process, with a substantial germination of intermediate seeds. In the other species, the conductivity of seeds of fruits with intermediate coloration was lower than that of mature fruit, because mature seeds are more affected by predators and pathogens. The tetrazolium tests indicated that the viability of seeds of three species increased with maturity and smaller differences between intermediate and mature stages were observed, supporting the DVSH. Only two species achieved high percentages of germination, and for Myrcia splendens, the pattern was very consistent with the hypothesis. We concluded that the germination and viability rates of the seeds of each plant species depend on many factors (e.g., dormancy and time of exposure to predators); however, for all the species studied, there is some evidence that seeds can germinate before they reach maturity by color.

Seed dispersal by monkey spitting in Scadoxus (Amaryllidaceae): Fruit selection, dispersal distances and effects on seed germination

“…It should be kept in mind that the green fruits used in this experiment were close to ripening (they were taken from infructescences where some fruits had already turned red) and therefore that these germination results cannot be extrapolated to fruits, which are in early stages of ripening. However, fruit colour changes, normally indicative of ripening, do not affect the germination of the seeds of many species (Cruz-Tejada et al 2018). Manipulation by monkey seed dispersers does increase the rate of germination of seeds of these two Scadoxus species through the removal of fruit pulp; however, it does not affect final germination percentage (Fig.…”

“…However, fruit colour changes, normally indicative of ripening, do not affect the germination of the seeds of many species (Cruz‐Tejada et al . 2018). Manipulation by monkey seed dispersers does increase the rate of germination of seeds of these two Scadoxus species through the removal of fruit pulp; however, it does not affect final germination percentage (Fig.…”

Seed dispersal by proboscis monkeys: the case of Nauclea spp.

“…We observed that UF seeds (control seeds from unripe fruits) had a higher probability of germination than RF seeds (control seeds from ripe fruits) by the end of the germination experiment (d 80: 60 days of shade followed by 20 days of sun exposure). Although counterintuitive (Arthur 1985), higher or similar germination success of seeds from unripe fruits, compare with mature fruits, has been reported (Foster 1977;Arditti et al 1981;Cruz-Tejada et al 2018). In the case of N. orientalis (used for control treatments), this could be an advantage to benefit from seed dispersal by animals that preferentially feed on unripe fruits, such as colobines (Davies et al 1988;Dasilva 1994;Matsuda et al 2009;Hanya and Bernard 2012;Ehlers Smith et al 2013).…”

Seed viability changes during fruit ripening of Tapirira guianensis Aubl.: Implications for collection

“…However, many forest species show unevenness fruit maturation and, therefore, can produce seeds with different levels of physiological quality. In addition, there are species in which the seeds that become viable before the fruits become fully mature (Cruz-Tejada, et al, 2018). In addition, the physiological maturation process of seeds can differ between natural populations of a specie, due the genetic structure of a single plant to influence the germination potential of seeds (Yuan, et al, 2016).…”