Influence of phylogenetic diversity of plant communities on tri-trophic interactions

Abstract

Phylogenetic diversity of plant communities can influence the interaction between plants, herbivores, and their natural enemies. Plant communities with phylogenetically distant species tend to present a wide variety of functional traits and ecological niches, which in turn can influence competitive interactions among plants as well as food and habitat quality for herbivores and their natural enemies. To assess some different mechanisms by which phylogenetic diversity of plant communities can influence herbivores and their natural enemies, we established 12 experimental plots of tropical trees with two treatments: high and low phylogenetic diversity. We measured plant growth and anti-herbivore defenses, herbivore foliar damage, and predator activity in seven species that were present in both treatments. We found significant differences in the expression of plant traits as a function of species identity and their life history, but also depending on the phylogenetic context in which they grew. Pioneer species had higher growth and produced more phenolics in plots with high phylogenetic diversity versus plants in plots with low phylogenetic diversity. Accordingly, herbivore damage in these species was greater in plots with low phylogenetic diversity. Finally, predator activity on caterpillar clay models placed on plants was greater within the low phylogenetic diversity treatment, but only for non-myrmecophytic species. These results suggest that plant phylogenetic diversity can influence the expression of growth and defensive traits and further modify the interaction between plants, herbivores, and their natural enemies. However, such effects depend on plant life history and the presence of mutualistic interaction with ants.

Keywords: Defenses; Growth; Herbivory; Life history; Phylogenetic diversity; Resource allocation; Tropical trees.

Fig. 1

Growth in relative height (A, B) growth in relative diameter (C, D) leaf thickness (E, F) specific leaf mass (G, H) total free phenols (I, J) and leaf damage (K, L) in all focal species in plots with low (gray bars) and high (black bars) phylogenetic diversity. Plants were distinguished by their life history (pioneers and tolerant) and species identity: Vachellia cornigera (Vaco), Cecropia obtusifolia (Ceob), Cedrela odorata (Ceod), Ceiba pentandra (Cepe), Eugenia acapulcensis (Euac), Inga vera (Inve), and Zanthoxylum limonella (Zali). Mean and error bars (± 1 SE) are shown. Asterisks (*) indicate significant differences at < 0.05

Fig. 2

Relationships between relative height growth and leaf thickness in pioneer species. Black dots correspond to plants in the high phylogenetic diversity treatment and gray dots to plants in the low phylogenetic diversity treatment. The 95% confidence interval is indicated by the shaded area in gray

Fig. 3

Relationships between total free phenolics and herbivory in pioneer species. Black dots correspond to plants in the high phylogenetic diversity treatment and gray dots to plants in the low phylogenetic diversity treatment. The 95% confidence interval is in indicated in y the shaded area in gray

Fig. 4

Response of the third trophic level (A) and the percentage of leaf damage (B) in myrmecophyte and non-myrmecophyte species in plots with high (black bars) and low (gray bars) phylogenetic diversity. Mean and error bars (± 1 SE) are shown. Asterisks (*) indicate significant differences at < 0.05