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In the woody flora from the Mediterranean basin there are two character syndromes which differ in diversification rate : the sclerophyll and the nonsclerophyll syndrome ; the latter has the highest diversification rate mainly due to rampant speciation. The cause of this increased diversification rate in nonsclerophylls could be the overall and complex interaction between their syndrome traits (conspicuous flowers, dry fruits, small seeds, non-animal dispersal, fireinduced germination) and environmental pressures (pollinator competition, summer drought, poor soils, frequent fires). Alternatively, one or very few of the syndrome traits could be responsible of most of the difference in diversification rate (trait-driven diversification). This work examines the relative role of syndrome traits on nonsclerophyll diversification using ANCOVA analyses for the flora of Western Andalusia (Spain). The results point that the increased diversification rate typical of the nonsclerophyll syndrome is largely caused by one single trait : the obligate seeder strategy (that is, fireinduced germination in fire-killed shrubs). This is the only trait whose consideration erases the difference in diversification rate between both syndromes. This result cannot be explained as the effect of altitudinal range as a potentially confounding variable. Furthermore, obligate seeder genera show a much higher diversification rate than the other genera and account for most of the species richness here considered. Thus the origin of this Mediterranean flora can be better understood as the outcome of traitdriven (seeder strategy) instead of syndromedriven diversification. The role of fire in the evolution of this regional flora stands out over the other possible factors here considered.

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The possible influence of geographic range size on speciation remains a controversial subject in evolutionary ecology, with theory and data supporting positive, negative and bell-shaped relationships between speciation probability and ancestor range size. In this study, a surrogate of the speciation-range size relationship of extant European tree species (22 genera, 11 families) is obtained by comparing the range-size distribution of candidate ancestors (i.e. species which are thought to have originated new species) with that of relatives, controlling phylogenetic inertia and macroecological sampling bias. In this comparison, species range size is measured qualitatively using six categories. The candidate ancestors included seem to have speciated mainly through allopatric speciation, with fewer instances of hybridogenesis by allopolyploidy. The results show that speciation is significantly facilitated for species with intermediate range size. In the European tree flora, this pattern could be the result of multiple causes, including intermediate dispersal ability at these ranges. Descendant tree species tend to have narrow geographic ranges, a trend which arguably comes from limited dispersal ability in this case. Low dispersal ability could be common in new species as a consequence of widespread adaptation to stable habitats isolated by geographic barriers (“island habitats”) during allopatric speciation. This mechanism could be widespread among regional biotas and would facilitate narrow ranges in new species. This would provide a simple explanation to the observed abundance of narrow ranges in most macroecological species-range size distributions.

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