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Pre-dispersal Seed Predation (pre-dispersal + seed_predation)
Selected AbstractsPre-dispersal acorn predation in mixed oak forests: interspecific differences are driven by the interplay among seed phenology, seed size and predator sizeJOURNAL OF ECOLOGY, Issue 6 2009Josep M. Espelta Summary 1.,Pre-dispersal seed predation (PSP) often occurs in multi-host,predator systems (e.g. several plant species exposed to a common array of granivorous insects). However, whether the interaction among seed phenology, seed size and predator size accounts for interspecific differences in PSP remains elusive. 2.,We studied PSP in a mixed-oak forest with two oaks (the larger-seeded Quercus humilis and the smaller-seeded Q. ilex), both depredated by two acorn weevils (the smaller Curculio glandium and the larger C. elephas). We intensively monitored acorn production and infestation phenology and we identified the weevil species depredating acorns by means of DNA taxonomy. 3.,The minimum acorn size required for infestation was lower for C. glandium than for C. elephas, in accordance with their different body sizes. This resulted in an earlier infestation phenology in C. glandium and the ability of this species to infest both smaller and larger acorns. Above a minimum acorn size threshold, no selection for larger acorns by weevils was observed. 4.,Initial acorn crop size was similar in the two oaks. Nonetheless, the earlier acorn phenology and the production of larger acorns in Q. humilis favoured the earlier infestation by C. glandium and the predation by both small and large weevils. Smaller acorns of Q. ilex almost excluded infestation by the larger C. elephas. 5.,Although larger acorns of Q. humilis could better survive infestation (preserve the embryo), higher PSP in this species finally resulted in a lower mature acorn crop size than in Q. ilex. 6.,Synthesis. In a multi-host,predator system, smaller-seeded species may benefit from a reduced PSP because they exclude larger granivorous insects, but also by means of a ,free-rider effect', if larger-seeded heterospecifics earlier reach a critical size to be depredated. These results also highlight the benefits of a small body size in granivorous insects to depredate seeds earlier and to forage on a wider range of seed sizes. Whether the advantage of ,being small' in this antagonistic plant,animal interaction is offset by other processes, or whether it results in a pressure towards seed and insect size reduction, deserves further attention. [source] Seed predation during general flowering events of varying magnitude in a Malaysian rain forestJOURNAL OF ECOLOGY, Issue 4 2007I-FANG SUN Summary 1The lowland dipterocarp forests of Southeast Asia exhibit interspecifically synchronized general flowering (GF) and mast fruiting at irregular multi-year intervals of 1 to 11 years. The predator satiation hypothesis (PSH) posits that GF events enhance seed survival by reducing the survival, reproduction and population sizes of seed predators between GF events, and then satiating the reduced seed predator populations during GF events. 2Three GF events of different magnitudes occurred in Pasoh Forest Reserve, Peninsular Malaysia, during 2001, 2002 and 2005. We exploited this natural experiment to test two predictions of the PSH. The first prediction was that seed survival should increase with the magnitude of the GF event. The second prediction was that seed predation should decrease with time since the previous GF event. 3A reproductive survey of all (c. 900) dipterocarp trees 30 cm d.b.h. in a 50 ha plot showed that flowering pervasiveness (the proportion of dipterocarp species participating) was high and similar in all three GF events. However, relative flowering magnitudes (measured by an index of individual tree participation and flowering intensity in Shorea species) were 2, 5 and 8 for the 2001, 2002 and 2005 GF events, respectively. 4The percentage of Shorea seeds surviving pre- and post-dispersal predation increased with the magnitude of GF events, which is consistent with the first prediction. 5Pre-dispersal insect seed predators consumed 12.9%, 11.2% and 3.4% of Shorea seeds in the 2001, 2002 and 2005 GF events, respectively, which is consistent with both predictions. 6Pre-dispersal seed predation by primates (mainly leaf monkeys) increased from 11.9% to 38.6% then fell to 9.3% in the 2001, 2002 and 2005 GF events, respectively. 7Predator satiation occurred only at population and community levels. At the individual tree level there was no relationship between the percentage of seeds surviving pre- and post-dispersal seed predation and variation in seed crop size or seed density beneath the tree. This suggests that attempts to test the PSH on the scale of individual trees may miss key community level effects. 8Our results suggest a more significant role of pre-dispersal seed predation in the evolution of reproductive synchrony than was recognized in the original statement of the PSH. [source] Pre-dispersal predation of Taraxacum officinale (dandelion) seedJOURNAL OF ECOLOGY, Issue 2 2005ALOIS HONEK Summary 1Pre-dispersal predation of seeds of Asteraceae has been studied in species where ripening seed is present on plants for long periods but rarely in those where seed maturation is ephemeral and density of consumers is therefore unlikely to keep pace with changes in seed availability. 2We therefore followed predation of dandelion (Taraxacum officinale) seeds by the larvae of Glocianus punctiger and Olibrus bicolor and predicted that both abundance of seed consumers and seed damage will be indirectly proportional to inflorescence availability, and that overall seed damage will be less than in species with longer lived inflorescences. 3We counted the number of dandelion capitula m,2, number of larvae capitulum,1 and percentage of damaged seeds at 10 sites, where the flowering time and densities of dandelions differed. The counts were made in 2002 and 2003, at half-weekly (April,May) or weekly (June,August) intervals. 4Abundance of both species of consumer varied among dandelion patches, and with change in availability of dandelion capitula. Numbers of larvae capitulum,1 were high early and late, when few capitula were available, but decreased at the time of peak flowering when there were many capitula. Production of ready-to-pupate larvae m,2 of a species at a site was similar in successive years, but values for O. bicolor and G. punctiger were not correlated. 5Seed damage paralleled the abundance of consumer larvae, with early and late flowers suffering most. A linear relationship correcting for lost seeds, predicted 30% damage when there were five larvae capitulum,1, below levels reported for species of Asteraceae with persistent inflorescences. 6The intensity of pre-dispersal seed predation is directly proportional to the abundance of seed consumer species and indirectly proportional to the availability of maturing capitula. Consequently, in species with ephemeral, synchronized flowering, where seed is available for only a short time, the majority of plants lose only a small proportion to predators. Although those flowering earlier or later than the peak will suffer a much higher risk, the low overall level of damage is unlikely to influence population biology. [source] Early fate of Myristica hypargyraea seeds dispersed by Ducula pacifica in Tonga, Western PolynesiaAUSTRAL ECOLOGY, Issue 4 2005HAYLEY J. MEEHAN Abstract Although pigeons from the genus Ducula are considered among the best avian dispersers of large seeds in Asia and the Pacific, little has been documented on their role. The early fate of dispersed and undispersed seeds of the large-seeded tree Myristica hypargyraea A. Gray was studied in order to understand the advantage of seed dispersal by the Pacific Pigeon, Ducula pacifica Gmelin in Tonga. Frequency of visits by frugivores to fruiting trees and dispersal distance of seeds were measured. Pre-dispersal vertebrate seed predation was assessed, then post-dispersal predation was measured over 160 days. Overall, pre-dispersal seed predation by parrots was low but variable among trees sampled. Most seeds (54.7%) in the study area were estimated to be dispersed by D. pacifica; 79.7% of those ingested were expelled directly beneath conspecific fruiting crowns, 20% were dispersed locally and <,0.3% were dispersed more than 300 m into a different forest type. Flying foxes (Pteropus tonganus Quoy and Gaimard) dispersed very few seeds (0.7%) and all were dropped below fruiting crowns. Between 4% and 39% of dispersed and undispersed seeds were still viable, or had established seedlings after 160 days. Most seeds had been removed or killed by rats, and seed survival was highest for locally dispersed seeds (approx. 20 m from source trees and within the M. hypargyraea forest). Although D. pacifica was the only frugivore observed to disperse seeds into this higher zone of survival, overall they did not confer a great advantage to seed survival since significant numbers of seeds/seedlings also persisted under fruiting crowns (27% under crowns compared with 39% locally dispersed). Nevertheless, D. pacifica was the only vector by which seeds were regularly moved within the M. hypargyraea forest and over longer distances, and hence, D. pacifica still plays a significant role in the regeneration of M. hypargyraea. [source] | ||||||||||