Are post-dispersed seeds of <i>Eucalyptus globulus</i> predated in the introduced range? Evidence from an experiment in Portugal

Abstract

Abstract. Plantations of Eucalyptus globulus Labill. have been expanding rapidly worldwide. The species is considered invasive in several regions. While in the native range, post-dispersal seed predation is known to severely limit eucalypt recruitment, there is no experimental evidence of seed predation in the introduced range. We hypothesised that E. globulus seeds largely escape predation in Portugal, which may explain its prolific recruitment in some locations. We tested this hypothesis in central Portugal by exposing E. globulus seeds to the local fauna. For comparison purposes, we also used seeds from locally common species: Acacia dealbata Link (alien, larger, elaiosome-bearing seeds) and Cistus salviifolius L. (native, similarly sized seeds). We installed 30 feeding stations across three study sites, each one dominated by one study species. Each feeding station featured four feeders with different animal-access treatments: invertebrates; vertebrates; full access; no access (control). We placed five seeds of each plant species every day in each feeder and registered the number of seeds missing, eaten and elaiosome detached over 9 summer days. Eucalyptus globulus seeds were highly attractive to fauna in the three sites. Nearly half of E. globulus seeds were predated or removed, thus contradicting our hypothesis. Surprisingly, E. globulus and A. dealbata seeds were used by animals in similar proportions and C. salviifolius seeds were the least preferred. Vertebrates were the predominant seed predators and preferred the alien seeds. Invertebrates used all seed species in similar proportions. We found spatial variation regarding the predominant type of seed predators and the levels of seed predation according to the following patterns: predominance of vertebrates; predominance of invertebrates; negligible seed predator activity. Locations with negligible seed predation were abundant and scattered across the study area. Such spatial variation may help to explain the heterogeneous recruitment patterns of E. globulus seedlings found in previous studies.

Post-Fire Demography, Growth, and Control of Eucalyptus globulus Wildlings

“…Seeds have higher germination success if adequate moisture conditions are met shortly after dehiscence. The shorter the time-lag between dehiscence and germination cues, the higher will be the probability that seeds will escape predation and natural decay [58,59]. The fire occurred unusually late in early autumn (15 October), two days before significant rainfall (13 mm).…”

Seed abundance affects seed removal of an alien and a native tree in the Brazilian savanna: Implications for biotic resistance

“…The consumption of alien seeds by seed predators is observed elsewhere (Blaney & Kotanen 2001;Nuñez et al 2008;Pearson et al 2014;Preukschas et al 2014;Deus et al 2018;Montesinos et al 2018). In agreement with other studies, the removal rates of our alien seeds were lower (Shahid et al 2009;Connolly et al 2014).…”

“…For instance, post-dispersal seed predators are often generalists and readily consume new food items of great energetic value (Kelrick et al 1986), and their activity can provide biotic resistance against alien plant invasion in some contexts (Nuñez et al 2008;Pearson et al 2011Pearson et al , 2014. However, the response of granivores to invasive species is highly variable, and studies comparing seed removal of native and invasive species have found controversial findings (Blaney & Kotanen 2001;Shahid et al 2009;Connolly et al 2014;Preukschas et al 2014;Deus et al 2018;Montesinos et al 2018). The identity of granivores and their preferences for native seeds over exotic seeds can be important for the outcome of invasion (reviewed by Parker et al 2006).…”

Origins, Diversity and Naturalization of Eucalyptus globulus (Myrtaceae) in California

“…At a local scale, studies in Portugal have shown saplings were more abundant on moist aspects [14], and spread more along natural drainage lines and in the direction of the prevailing wind [19]. At this local scale, the likelihood of sapling establishment has also been shown to depend upon the reproductive output of the E. globulus source population [11,15,19], adjacent plant community type [18,49], fire [11,15,17,80,81] and, potentially, levels of seed predation [80,82].…”