Natural and human-impacted diversity of bryophytes along an elevational gradient on an oceanic island (La Palma, Canarias)

Bryophyte Diversity and Distribution Patterns along Elevation Gradients of the Mount Etna (Sicily), the Highest Active Volcano in Europea

Mt Etna in Sicily hosts a bryophyte floristic richness of 306 taxa, corresponding to 259 mosses, 43 liverworts, and 4 hornworts. Species richness shows a hump-shaped relationship with the elevation, with a peak at 1200-1700 m a.s.l. Chorotype patterns clearly change along an altitudinal gradient, from the Mediterranean, located at 0-300 m a.s.l., to Arctic-montane and boreo-Arctic montane at 1800-2700 m a.s.l., showing a correlation with the bioclimatic belts identified for the Mt Etna. In regard to the life form pattern, the turf species are the most represented in each elevation gradient, except at 2300-2700 m a.s.l. where the tuft species are prevalent. The life strategy pattern shows the colonists as the prevailing species, featured by an increasing trend up to 2200 m of elevation; above this limit, they are exceeded by the perennial stayers. Furthermore, taking into consideration the red-listed species (at the European and/or Italian level), as well as the species of phytogeographical interest, it was possible to identify the high bryophyte conservation priority areas; these areas are located in thermo-Mediterranean and oro-Mediterranean bioclimatic belts, the latter corresponding to the oldest substrates of the volcano where some of the most interesting bryophyte glacial relicts find refuge.

Diversity of lithophytic moss species in karst regions in response to elevation gradients

The distribution pattern of species diversity along various elevation gradients reflects the biological and ecological characteristics of species, distribution status and adaptability to the environment. Altitude, a comprehensive ecological factor, affects the spatial distribution of species diversity in plant communities by causing integrated changes in light, temperature, water and soil factors. In Guiyang City, we studied the species diversity of lithophytic mosses and the relationships between species and environmental factors. The results showed that: (1) There were 52 species of bryophytes in 26 genera and 13 families within the study area. The dominant families were Brachytheciaceae, Hypnaceae and Thuidiaceae. The dominant genera were Brachythecium, Hypnum, Eurhynchium, Thuidium, Anomodon and Plagiomnium; The dominant species were Eurohypnum leptothallum, Brachythecium salebrosum, Brachythecium pendulum etc. The number of family species and dominant family genera increased first and then decreased with the increase of altitude, and their distribution in elevation gradient III (1334-1515m) was the largest, with 8 families, 13 genera and 21 species. The elevation gradient I (970-1151m) was the least species distributed, with 5 families, 10 genera and 14 species. The dominant species with the largest number in each elevational gradient were Eurohypnum leptothallum, Brachythecium pendulum, Brachythecium salebrosum and Entodon prorepens; (2) There were five kinds of life forms in different elevation gradients, including Wefts, Turfs, Mat, Pendants and Tail. Among them, wefts and turfs appeared in all elevations, while a small amount of Pendants appeared in the area of elevational gradient I (970-1151m), and the most abundant life form was found in the range of elevational gradient III (1334-1515m); (3) Patrick richness index and Shannon-Wiener diversity index were highly significantly (p<0.01) positively correlated, both of which increased and then decreased with elevation, reaching a maximum at elevation gradient III (1334-1515m); The Simpson dominance index had a highly significant (p<0.01) negative correlation with the Patrick richness index and the Shannon-Wiener diversity index, which showed a decreasing and then increasing trend with increasing altitude; Pielou evenness index showed no discernible trend; (4) β diversity study revealed that while the similarity coefficient tended to decrease with increasing altitude, the species composition of bryophytes increased. The elevation gradient II (1151-1332m) and elevation gradient I (970-1151m) shared the most similarities, whereas elevation gradient III (1515-1694m) and elevation gradient I shared the least similarities (970-1151m). The findings can enrich the theory of the distribution pattern of lithophytic moss species diversity at distinct elevation gradients in karst regions, and serve a scientific and reasonable reference for restoring rocky desertification and protecting biodiversity there.