Abstract
Pre-dispersal flters imposed on the seed stage can alter the likelihood of seed dispersal. We evaluate pre-dispersal seed loss due to predation by insects and abortion in Prosopis flexuosa and P. chilensis . This study was conducted in two protected areas in the Monte Desert. We collected P. flexuosa and P. chilensis fruits from different trees, from two plots and two years. Samples were maintained for 50 days in translucent PVC boles stored in a laboratory under stable temperature (25 °C) and natural photoperiod, awaiting the emergence of insects. Then we opened the fruits and individually examined all seeds to determine their condition. We found that total pre-dispersal seed loss was 32% in P. flexuosa and 21% in P. chilensis . Seed predation by insects was the major source of pre dispersal seed loss (19% in P. flexuosa and 14% in P. chilensis ). The main seed predator was the apionid weevil (Brentidae: Apioninae) in P. flexuosa , and bruchid beetles (Chrysomelidae: Bruchinae) in P. chilensis . Some bruchid beetles prey upon seeds, completing their life cycle, whereas others remain inside seeds (41% in P. flexuosa and 49% in P. chilensis , of total seed damaged by bruchid beetles). Seed abortion was another important source of seed loss, especially for P. flexuosa , but its cause still remains unknown. We show and discuss the extent of a proposed methodology to account for pre-dispersal seed predation that includes the immature stages of non-emergent bruchid. Pre-dispersal seed loss by insects and abortion represent an ecological flter that limits the amount of seeds available for dispersal and establishment of these species. Understanding seed loss process may contribute to know and predict Prosopis population dynamics, revealing the natural regeneration mechanisms to forest recovery. https://doi.org/10.25260/EA.18.28.2.0.576
Highlights
Biotic and abiotic pre-dispersal filters imposed on the seed stage can alter the likelihood of seed dispersal (Janzen 1971), affecting the probability of transition to the following stages
Facilitate the occurrence of many other species in P. flexuosa and P. chilensis, it has been sug- under their crowns (Rossi and Villagra 2003; gested that the fruits fallen on the ground are Rossi 2004; Larrea-Alcázar et al 2005; Villagra usually more preyed upon by insects than those remaining on al. 2013)
We identified four sources of seed loss in ripe pods of P. flexuosa (Table 2): seed predation by apionid weevils, seed predation by bruchid beetles, seed predation by unidentified insects, and seed abortion
Summary
In spe- (Villagra et al 2009; Bastin et al 2017) These cies of Prosopis, only 20-45% of initiated fruits trees are considered key species because they reach full size (Cariaga et al 2005). Facilitate the occurrence of many other species in P. flexuosa and P. chilensis, it has been sug- under their crowns (Rossi and Villagra 2003; gested that the fruits fallen on the ground are Rossi 2004; Larrea-Alcázar et al 2005; Villagra usually more preyed upon by insects (particu- and Álvarez 2006; Cesca et al 2012; Greco et larly bruchid beetles) than those remaining on al. The specific goals were 1) to identify, quantify and compare the sources of pre-dispersal seed loss in unripe and ripe pods; and 2) to explore the effects of the location of ripe pods in relation to the parent plant (crown and ground) on insect predation of seeds
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