Together Apart: Evaluating Lichen-Phorophyte Specificity in the Canarian Laurel Forest

Abstract

The effects of host tree identity on epiphyte lichen communities are a controversial issue, as the results obtained in different forest environments studied are not consistent. We investigated the host preferences for lichens in the laurel forest of Macaronesia. For this purpose, we analyzed the lichen communities growing on the four most common trees (Erica canariensis Rivas-Mart., M. Osorio and Wildpret, Morella faya (Aiton) Wilbur, Laurus novoca-nariensis Rivas-Mart., Lousa, Fern. Prieto, E. Días, J.C. Costa and C. Aguiar, and Ilex canariensis Poir. in Lamarck) in the laurel forest of the Canary Islands. The diversity, richness, and lichen composition showed a repetitive and common pattern with the functional traits studied. Although the existence of specificity with respect to the phorophyte species was not demonstrated, there was a clear affinity of the epiphytic lichens to the physico-chemical features of the bark (texture and pH), canopy architecture, foliar characteristics, etc. Our results highlight the importance of the natural diversity of tree species in the laurel forest. Due to the diversity and uniqueness of the lichen species that support each of the phorophytes, this fact should be taken into account in landscape protection and restoration actions, especially in those islands where the forest is highly fragmented.

Keywords: Canary Islands; Macaronesia; epiphytic lichen; laurel forest; phorophyte.

Figure 1

Field plots installed on potential area of humid laurel forest (Lauro novocanariensis—Perseetum indicae) in La Palma, La Gomera, and Tenerife islands.

Figure 2

(a): Sampling methodology: frame on laurel forest’s tree. (b): Laurel forest in La Gomera Island. (c–f): Tree bark of Erica canariensis (c), Ilex canariensis (d), Laurus novocanariensis (e), and Morella faya (f).

Figure 3

Boxplot of richness (S) by phorophyte (a) and Venn diagram of unique and shared lichen taxa of four phorophytes (Erica canariensis, Ilex canariensis, Laurus novocanariensis, and Morella faya) in all studied islands (b).

Figure 4

Morphological traits of lichen in Morella faya (black bars), Erica canariensis (dark gray bars), Laurus novocanariensis (gray bars), and Ilex canariensis (white bars); biotypes: Cr: crustaceous, Fl: foliose, Fr: fruticose, Sq: squamulose, Di: dimorphic, Pu: pulverulent/leprose, Wt: without thallus; photobionts: GC: green clorococcoid algae, GT: Trentepohliaceae algae, Ci: cyanobacteria, WA: without algae; and reproduction/multiplication: Sp: spore, So: soredia, Is: isidia, So + Is: soredia and isidia, Fr: fragmentation, Co: conidia.

Figure 5

Percentage of unique species in each category of functional groups value and phorophytes studied: (a) substrata pH, (b) solar irradiation, (c) aridity, (d) eutrophication, and (e) poleotolerance.

Figure 6

NMDS plot based on abundances matrix and Jaccard distances. Each point represents the sum of lichen abundance in the two trees sampled of each different phorophyte in each plot. Stress: 0.28.