Aim: To test whether the degree of phylogenetic diversity differs in two congeneric, morphologically similar lichens that are both widespread and with a similar geographical range (Neotropics and Hawaii), but differ in altitudinal and habitat preferences, and whether the two species underwent isolation by distance (IBD), environment (IBE), or fragmentation (IBF).

Location: South and Central America, Caribbean, Hawaii, Azores.

Taxon: Sticta (Peltigeraceae).

Methods: Analysis of 395 specimens across the study area; ITS barcoding marker; maximum likelihood tree reconstruction within a broad taxonomic framework; TCS haplotype networks; Mantel test of genetic vs. geographic, environmental, and fragmentation distances; statistical comparison of BIOclim variables.

Results: Sticta andina exhibited high phenotypic variation and high reticulate phylogenetic diversity across its range, whereas the phenotypically more uniform S. scabrosa contained two main haplotypes, one unique to Hawaii (subsp. hawaiiensis). Sticta andina was restricted to well-preserved andine forests and paramos, habitats fragmented due to disruptive topology, whereas S. scabrosa was found in lowland to lower montane forests in rather exposed microsites, representing a more continuous habitat. These differences were statistically significant for several BIOclim variables. Mantel tests on genetic vs. geographic and environmental distances demonstrated that S. scabrosa followed a pattern of IBD across its full range but not within continental Central and South America. In contrast, S. andina did not exhibit IBD but showed weak, yet significant patterns of IBE at continental level and IBF in the northern Andes.

Main Conclusions: Autecology indirectly drives phylogenetic diversity in the two studied species. In the low altitude species, S. scabrosa, phylogenetic diversity is low and shows no correlation with geographic or environmental distances, except for the differentiation of the Hawaiian subspecies. We attribute this to rapid expansion and effective gene flow between populations across a more or less continuously distributed niche representing partially exposed microsites, including disturbed and anthropogenic vegetation, such as planted trees. In contrast, in the high altitude species, S. andina, phylogenetic diversity is high and correlated with both environmental niche differentiation (IBE) and fragmentation caused by the final Andean uplift (IBF). Therefore, an autoecological preference for high altitudes increases the likelihood for higher phylogenetic diversity.

The dataset contains the voucher information for the studied specimens (EXCEL); the ITS-based alignments (FASTA; sequences also available from GenBank); the specimen-based coordinates, altitude values, bioclim variables and tree cover layer data (EXCEL); the distance matrices used for the Mantel tests (tab-delimited TXT); and the best-scoring maximum likelihood trees derived from the ITS-based alignments (PDF).

Appendix S1. Voucher table of the studied samples.

Appendix S2. Global ITS alignment for the genus Sticta.

Appendix S3. Local ITS alignment for Sticta andina.

Appendix S4. Local ITS alignment for Sticta scabrosa (incl. subsp. hawaiiensis).

Appendix S5. Coordinates, altitude, and selected features for the specimens of Sticta andina and S. scabrosa (incl. subsp. hawaiiensis) studied.

Appendix S6. Data matrix for the analysis of bioclimatic variables and altitude and tree cover layers.

Appendix S7. Distance matrices used for the Mantel tests (zipped file).

Appendix S8. Global ITS tree for the genus Sticta.

Appendix S9. Local ITS tree for Sticta andina.

Appendix S10. Local ITS tree for Sticta scabrosa (incl. subsp. hawaiiensis).

Bioclim data derived from http://www.worldclim.org

Landsat tree cover layer derived from http://glcf.umd.edu/data/landsatTreecover