Improved retrieval of phylogenetic signals from normalized foliar reflectance spectra in Neotropical forest gaps

Diniz, Écio Souza and do Amaral, Cibele Hummel and de Almeida Telles, Lucas Arthur and Meira-Neto, João Augusto Alves (2023) Improved retrieval of phylogenetic signals from normalized foliar reflectance spectra in Neotropical forest gaps. COMMUNITY ECOLOGY, 24 (2). pp. 283-291. ISSN 1585-8553 (print); 1588-2756 (online)

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Abstract

Distinct data pre-processing techniques affect features derived from spectral data, such as the occurrence of phylogenetic signals in the foliar spectra. This study investigates how untransformed and transformed foliar spectral data affect the phylogenetic signal of 53 woody plant species located in regenerating forest gaps. The spectral signature for each species was considered under untransformed (raw reflectance spectra) and transformed (normalization by first derivative) aver- age of reflected wavelengths from four spectral regions: VIS (visible region: 400–700 nm), NIR (near-infrared region: 701–1349 nm), SWIR-1 (short-wave infrared region part one: 1350–1850 nm), and SWIR-2 (short-wave infrared region part two: 1851–2450). We evaluated the evolutionary conservation (phylogenetic signal) through Blomberg (K) and Pagel (λ) metrics for all 2051 averaged (untransformed and transformed) reflected wavelengths of the species. We found a predomi- nant evolutionary convergence of wavelengths in both transformed and untransformed foliar spectra. Specifically, we found significant phylogenetic signal for transformed spectra in NIR and SWIR-1 regions and reduced portions in SWIR-2. For the untransformed spectra, the significant phylogenetic signals in SWIR-2 stand out. In conclusion, such main results indicate that normalization by first derivative performs better in disentangling overlapping wavelengths. Thus, we recommend to perform phylogenetic analysis on the transformed spectra since it can highlight the phylogenetic signal of plant features that otherwise are underemphasized in untransformed foliar spectra.

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