Surviving or thriving? Trade-offs between growth, defense, and reproduction in a native versus an invasive Rubus

Abstract

Little is known about limits to reproduction in plants, especially as to how their other life history functions (growth and defense) may constrain reproductive investment. Understanding these constraints can help researchers refine best practices for cultivating species like Rubus (Rosaceae) that produce nutritious fruits as well as for controlling invasive species. Here, we sought to elucidate potential trade-offs between growth, defense, and reproduction in native Rubus allegheniensis Porter (common blackberry) and invasive Rubus phoenicolasius Maxim. (wineberry) while accounting for the effects of varying insect herbivory and resource availability levels. We observed traits related to physical defense (e.g., prickle intensity), growth (e.g., cane length), and floral reproduction (e.g., ripe fruits), as well as carbon availability (e.g., canopy cover). We then used multiple regressions to characterize relationships between these variables for both species. We found potential evidence for 2 induced defenses in the invasive wineberry. Also, 5 models returned significant results indicative of trade-offs between reproduction and growth, reproduction and defense, and defense and growth in a single or both species. Our results highlight the importance of understanding the defensive strategies utilized by these species because inducible defenses may result in trade-offs that could reduce yields and (or) increase the invasive potential of Rubus species.