Germination responses to temperature are not linked to elevation vegetational belts in alpine species of the Andes of central Chile

Abstract

Temperature is a major environmental cue for seed germination in alpine plant species, where high temperatures tend to promote seed germination. However, the extent to which germination responses to temperature differs between vegetation belts remains poorly studied, especially along elevational gradients in the temperate Andes. We quantified germination across three fluctuating temperature regimes (10/5° C, 20/10° C, 25/15° C) on 21 species representative of the Low- and High-Andean vegetation belts of central Chile. Using mixed-effects models with species as a random factor, we evaluated how temperature, vegetation belt, and their interaction influence final germination percentage and germination speed. Temperature significantly affected germination dynamics, with faster germination generally occurring under intermediate thermal conditions. In contrast, neither vegetation belt nor the belt × temperature interaction exerted significant effects on final germination or germination speed, indicating that elevational zone alone does not structure thermal germination niches. Species identity accounted for the largest portion of variance in both metrics, indicating intrinsic differences in germination responses. Classification of species into thermal response categories (cold-optimized, intermediate-temperature specialists, warm-enhanced germinators, and broad-temperature generalists) showed that all categories were represented in both vegetation belts. This lack of elevational segregation suggests that germination responses to temperature are not determinant on the elevational distribution in the central Chilean Andes. The facts that temperature influences germination speed more consistently than total germination, and that species-specific effects dominate germination responses suggest that climatic warming may differentially alter germination phenology among coexisting Andean species without uniformly increasing germination success.