Population dynamics of the shrub Acacia suaveolens (Sm.) Willd.: Seed production and predispersal seed predation

Abstract

Seed production and predispersal seed predation in the shrub Acacia suaveolens were examined over 3 consecutive years in eight populations in south-eastern Australia. Seed-crop sizes varied both between and within populations of different ages. Seed production was maximal in the first one to four flowering seasons after establishment, and then declined with plant age. The size of the annual seed-crop was also influenced by rainfall for that year.Predispersal seed predation varies between populations over fruiting seasons with the initial large seed-crops resulting in predator satiation. Within one fruiting season, no significant variation in the extent of predispersal seed predation was found in any of three populations studied. There were two major forms of predispersal seed loss: toss of whole fruits to Melanterius corosus (Coleoptera: Curculionidae) and external insect seed grazers, and loss of individual seeds within fruits to M. corosus. Exclusion experiments showed that seeds lost to these predispersal seed predators would otherwise have been matured by the parent plant. The effects of predispersal seed predation cannot be directly related to seedling recruitment. Indirectly, such predation may influence the dispersion of seeds in the soil profile and hence, subsequent recruitment.

Consumer pressure, seed versus safe-site limitation, and plant population dynamics

“…Many experimental studies now show that native insects can decrease native plant fecundity (Waloff and Richards 1977;Louda 1982aLouda , 1982bLouda , 1983Auld and Myerscough 1986;Louda and Potvin 1995;Root 1996;Maron 1998). However, how these reductions in fecundity translate across generations to affect plant population abundance is almost entirely unknown, particularly for plants with persistent seedbanks.…”

“…While a large number of experimental studies have documented such effects (Waloff and Richards 1977;Louda 1982aLouda , 1982bLouda , 1983Hendrix 1984;Auld 1986;Auld and Myerscough 1986;Zammit and Hood 1986;Andersen 1988Andersen , 1989bEvans et al 1989;Louda 1989;Louda and Potvin 1995;Wise and Sacchi 1996;Maron 1998), how these rather common herbivoredriven reductions in seed output affect future abundance and population dynamics of plants is still mostly a mystery. Of the hundreds of studies that have documented negative effects of consumers on plant performance, only a few have determined whether these effects have population-level impacts.…”

Evolutionary changes in correlations among functional traits in <i>Ceanothus</i> in response to Mediterranean conditions

“…A large seed with large nutrient stores reduces the dependence of seedling growth on external supply of both water and nutrients (Lee andFenner 1989, Jurado and and improves seedling survival under a variety of hazards (Leishman et al 2000). In addition, Cerastes seeds germinated earlier than resprouters seeds (13 vs 18.2 d after sown), a trait of shortlived species (Auld and Myerscough 1986) which could be related to their shorter generation time. Chaparral postfire seeders may represent a novel group combining early successional traits with traits proper of stress-tolerant species (Ackerly 2004a).…”

Prolonged Absence of Disturbance Associated with Increased Environmental Stress May Lead to Reduced Seedbank Size in Picea mariana in Boreal Eastern North America

“…Not only do ecologists still struggle to accurately predict mast years in tree species (Smaill and others 2011), there is an ongoing debate on universal factors that best predict seed production in a plant species (Leck 2012). For instance, factors such as plant size (Shipley and Dion 1992) and temperature (in heat limited areas ;Sirois 2000) are generally believed to positively affect a species' seedbank size, but other parameters such as plant age have been identified as both positive and negative drivers of seed production and seedbank size depending on the focal species (negative: Black and Bliss 1980;Auld and Myerscough 1986;positive: Witkowski and others 1991;Viglas and others 2013).…”