Macrolichen diversity in subtropical forests of north-central Florida

We sampled epiphytic and ground macrolichens in three subtropical forest types in north-central Florida (sand pine scrub, longleaf pine and hardwood bottoms). We detected 101 macrolichen taxa during community surveys in the three subtropical forest types. We used nonmeteric multidimensional scaling to determine factors associated with gradients in lichen community composition. In addition, we evaluated diversity of macrolichen species and species groups among the three vegetation types. Gradients in lichen community composition were closely associated with differences in vegetation structure (canopy cover, percent evergreen conifers) of the three forest vegetation types. Sand pine scrub forests supported the richest diversity and highest abundances of macrolichens, despite the young age of the stands. Sand pine scrub stands were young due to the frequency of stand-replacing fires. Alpha diversity averaged 26 macrolichen taxa per plot, ranging from 12 species in the youngest longleaf pine stand to 51 species in a mature sand pine scrub stand. Ground lichen cover ranged from 0–82% and, when present, formed a mat from 5–14 cm thick. Longleaf pine stands lacked ground lichen cover due to their dense grass understory and high fire frequency. These stands also had lower diversities and abundances of epiphytic macrolichens. The hardwood bottom vegetation type is often flooded with water and lacks both a consistent vascular plant and ground lichen cover. Hardwood bottoms experience fire infrequently and are intermediate in canopy lichen diversity. We used Indicator Species Analysis to determine if macrolichen species associated more closely with one or more of the three subtropical forest types studied. Lichen species indicative of sand pine scrub communities include Bulbothrix confoederata, Cladina evansii, C. subtenuis, Cladonia prostrata, C. ravenelii, Crocynia pyxinoides, Parmotrema sulfuratum and Usnea dimorpha. Dirinaria picta, Heterodermia albicans, Leptogium cyanescens, Ramalina americana and Ramalina willeyi were indicative of hardwood bottoms, and no lichen species were consistently indicative of longleaf pine communities.