Phylogenetic signatures in reflected foliar spectra of regenerating plants in Neotropical forest gaps

Abstract

Spectroscopy can be used to investigate ecosystem functioning and phylogenetic relationships, since it can provide information about the optical properties of a plant – a critical functional trait with regard to light usage. The link between phylogenetic relationships and foliar reflectance spectra of Neotropical species has rarely been considered and no previous studies have explored this in relation to forest regeneration following natural gap formation. We investigated phylogenetic signatures, i.e. evolutionary conservation, of foliar spectra in gap-regenerating woody species in conserved Neotropical forests. We collected foliar spectra of 53 regenerating woody species in the forest gaps at two sites of Atlantic Seasonal Semi-deciduous forest, and quantified the phylogenetic signal for spectral wavelengths using Blomberg's K, Pagel's lambda (λ) and LIPA (Local indicator of phylogenetic association) statistics. Analysis of foliar reflectance spectra showed that the largest portion of phylogenetic signature from both K and λ occurred within the first part of the shortwave infrared region (SWIR-1: 1551–1849 nm), followed by the near infrared (NIR: 701–1349 nm), and the lowest portion within the visible region (VIS: 400–700 nm). Most of the significant phylogenetic signal found for wavelengths of all spectral regions suggested convergent conservation, i.e. homoplasy. The largest portion of positive LIPA (i.e. phylogenetic similarity) was found for wavelengths within the second part of the SWIR (SWIR-2: 2051–2450 nm), while most of the negative LIPA (i.e. phylogenetic distinctiveness) occurred within the VIS. We conclude that there is a tendency towards evolutionary convergence in the phylogenetic signature of foliar spectra in certain parts of the spectrum. The extent of phylogenetic signal found in the SWIR allows us to conclude that this region carries the most potential for future investigations of phylogenetic influence on spectral community dynamics within Neotropical forests.