Seed predation does not explain pine invasion success
Why some non-native plant species invade, and others fail remains an elusive question. Plant invasion success has been associated with specific species traits. Yet, we have limited knowledge of the mechanisms relating these traits to invasion potential. General patterns of biotic resistance by seed predation may provide a mechanism that helps separate invasive from non-invasive plants. Seed predation is an important barrier against plant establishment for many plant species. It may, therefore, create a selective filter against non-native plant establishment based on plant traits related to seed predation rate. In two cafeteria-style seed predation experiments in a steppe ecosystem in Patagonia (Argentina) we provided seeds of 16 non-native Pinaceae covering a 300-fold variation in seed mass, a 200-fold variation in seed volume and 75-fold variation in seed toughness. Seed removal decreased with seed mass and seed volume. Seed toughness was not a significant predictor while seed volume was the best predictor of predators’ preference. However, for species of this family small seed size is the most important predictor of species invasiveness. Our results show that seed predation does not explain Pinaceae invasive success. In our system, species that have smaller seeds (i.e., more invasive) are preferentially consumed by seed predators. Seed mass was not the best predictor of granivory rates, despite being the seed trait on which most studies have been focused. Our ability to predict future invasion and understand invasion success could benefit from other studies that focus on the mechanisms behind invasive traits.
KeywordsBiotic resistance Invasive plants Invasive traits Pinus Seed traits
This research was supported by Rufford Foundation Grant number 23089-1 and the National Agency of Scientific and Technologic Promotion (AGENCIA) grant “PICT 2014 No 0662 PRESTAMO BID”. We thank San Ramon ranch for their help in this study. We also thank Ariel Mayoral and Josefina Uijt den Bogaard for their valuable help on the field. We are very grateful with René Rodriguez, Alejandro Yawny and Graciela Bertolino from the National Centre of Atomic Energy (CNEA) for help with measurements of seed toughness and providing us access to their Instron 5567 Universal Testing Machine. We appreciate the help with the statistical analyzes provided by Florencia Tiribelli. Mauro Tammone helped with the identification of small mammals. We greatly appreciate the helpful comments from Adam Davis and Rob Gibson on an earlier version of this manuscript.
Author contribution statement
JM, MC, MN, and MRC conceived the idea and JM designed the methodology with help from all the authors. JM carried out the experiments and collected the data with help from MC. All authors participated in the discussion of the results. JM led the writing of the manuscript. MC, MN, and MRC revised the manuscript and made comments to improve it. All authors gave final approval for publication.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All applicable institutional and/or national guidelines for the care and use of animals were followed.
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