Nuanced qualitative trait approaches reveal environmental filtering and phylogenetic constraints on lichen communities
Koch, Natalia et al. (2022), Nuanced qualitative trait approaches reveal environmental filtering and phylogenetic constraints on lichen communities, Dryad, Dataset, https://doi.org/10.5061/dryad.51c59zw9d
We propose that a qualitative trait approach based on more detailed nuanced traits may reveal previously overlooked patterns, especially when combined with phylogenetic perspectives. By sampling epiphytic lichens and using a functional approach based on nuanced qualitative traits, such as a much greater resolution over photobiont identity, type of cortex and chemical compounds, we evaluated the effects of environmental filtering and phylogenetic constraints on community assembly along natural succession of Atlantic rainforest. We found changes in taxonomic, functional and phylogenetic composition, structure and diversity. Functional traits such as photobiont genera, type of cortex, reproductive structures, propagule size and protection strategies showed strong responses to succession. Mature forests with a closed canopy impose strong environment filtering that is reflected in lichen species turnover, limiting diversity, but also holding different functional and phylogenetic composition. The use of a nuanced qualitative trait approach may overcome some of the limitations of using this type of traits and show the importance of often overlooked key lichen functional traits, including presence of carbon concentrating mechanisms in photobionts and cortex properties. Furthermore, this is the first study showing how patterns of phylogenetic assembly along forest succession structure lichen communities.
This study was carried out in forest fragments in the river basin Maquiné, between 51o21’-50o05’W and 29o20’-29o50’S, northeastern Rio Grande do Sul state, southern Brazil, where the climate is classified as subtropical humid (Moreno 1961). The annual mean temperature varies from 13ºC to 22ºC and the annual precipitation is around 1400 and 1800 mm (Hasenack and Ferraro 1989). The original vegetation is composed of Atlantic rainforests and corresponds to the southern distribution limit of one of the most important and rich tropical forests in the world (Myers et al. 2000). The demographic density in the region is only 11 inhabitants/km2 (IBGE 2010), and the main economic activity is small scale agriculture (subsistence farming), which means that we do not expect any important anthropogenic influence on lichen communities. Lichen communities were sampled in four different sites, each of them located in different valleys and each containing stands of three different stages of forest succession: initial - between 6 and 10 years of natural regeneration, intermediate - between 12 and 20 years, and late - between 40 and 60 years (Koch et al. 2013). The criteria used for selecting the areas were the existence of reliable information about the forest age and the possibility of finding all stages in a similar range of altitude and climatic conditions. We estimated stand ages by interviewing local inhabitants, only those living in the areas for at least 40 years. In each successional stage from each site two sampling units (SUs) were set (for a total of twenty-four SUs), where three randomly selected adult trees were sampled, all in a radius of 5 m. These tree individuals had CBH > 18 cm (CBH: circumference at breast height – 1.30 m from the ground), with a straight stem without branches below 1.50 m, without a smooth or peeling cortex. In total, we sampled 72 trees distributed in 24 SUs in four valley slopes, varying from 30 to 250 m of altitude.We sampled lichens on the tree stems from 30 to 150 cm from the ground, in regular intervals of 10 cm, which represented 13 height levels, using the rubber band method (Marcelli 1992). This method consists in placing a rubber band, gradually marked in percent-coverage classes from 0 to 100% of coverage around the stem. The length of the rubber bands varied according to the stem circumference i.e., the percent coverage is always relative to the tree size. Lichen species coverage per tree was the sum of the percent coverage (standardized according to the stem circumference) and the coverage of each species in the SU corresponded to the mean value of the three sampled trees.
CNPq, Award: 313732/2009-4