Meta-analysis using a Lehmann classifier of obligate seeding species germination in fire-prone Mediterranean Type environments

The generalization that specific seed traits such as dormancy, longevity, or heat-triggered germination of plant species expanding in pyrogenic environments where stochastically but recurrently fire disturbance occurs is a fitness increasing adaptation of obligate seeders dates from the early 20th century. During the last few decades, this hypothesis, qualified as a pyrophytic strategy, is re-evaluated under the lenses of conservation biology and climate change research. The validity of pyrophytism as an equilibrium response to fire vs. the interpretation that the obligate seeding strategy is instead an opportunistic or generalist response to the multitude of abiotic and biotic factors determining the variability and heterogeneity of fire-prone environments such as the Mediterranean Type Ecosystems is indirectly examined and narratively promoted in the renewed fire ecology literature. In this paper, I suggest a need for a typified meta-analysis of the abundant but disparate wealth of research protocols and data to achieve a quantitatively strict understanding of the limits of the contrasting hypotheses. I develop a meta-analytic classifier and test its feasibility and applicability across taxonomic, biologic, and ecological levels of organization, i.e., from the intra-population or inter-individual local level progressively to inter-genus and intra-family levels, across the Mediterranean Basin. Cistaceae species, emblems of the Mediterranean shrublands, are the model for this research. The results of this exercise support the feasibility and flexibility of the Lehmann-type classifier developed. Although Cistus species do respond positively to heat-shocks at the local level, significant variability is uncovered among higher taxa levels and furthermost as the environmental variability increases. The germination variability complicates generalizations when climatic variability and change come into play, questioning long-standing ‘certitudes’ and Mediterranean forest managers and conservation planners' practices.