Drought-adapted leaves are produced even when more water is available in dry tropical forest.

Species in dry environments may adjust their anatomical and physiological behaviors by adopting safer or more efficient strategies. Thus, species distributed across a water availability gradient may possess different phenotypes depending on the specific environmental conditions to which they are subjected. Leaf and vascular tissues are plastic and may vary strongly in response to environmental changes affecting an individual's survival and species distribution. To identify whether and how legumes leaves vary across a water availability gradient in a seasonally dry tropical forest, we quantified leaf construction costs and performed an anatomical study on the leaves of seven legume species. We evaluated seven species, which were divided into three categories of rainfall preference: wet species, which are more abundant in wetter areas; indifferent species, which are more abundant and occur indistinctly under both rainfall conditions; and dry species, which are more abundant in dryer areas. We observed two different patterns based on rainfall preference categories. Contrary to our expectations, wet and indifferent species changed traits in the sense of security when occupying lower rainfall areas, whereas dry species changed some traits when more water was available, such as increasing cuticle and spongy parenchyma thickness, or producing smaller and more numerous stomata. Trischidium molle, the most plastic and wet species, exhibited a similar strategy to the dry species. Our results corroborate the risks to vegetation under future climate change scenarios as stressed species and populations may not endure even more severe conditions.

Diversity and evolution of leaflet anatomical characters in the Pterocarpus clade (Fabaceae: Papilionoideae).

The Pterocarpus clade includes 23 genera previously attributed to different Fabaceae tribes. The recent rearrangements of many genera in the clade do not recognize morphological synapomorphies. This study aimed to identify new synapomorphies for the Pterocarpus clade, to identify characters supporting inter-generic relationships currently resolved only by molecular data and to identify diagnostic characters at the genus and species levels. Subterminal leaflets of the studied genera were selected and analyzed using light and scanning electron microscopy. Ancestral reconstruction was performed using morphological and anatomical characters of 16 genera of the Pterocarpus clade. The convex epidermal relief in the region of the main vein indicated the relationship among all genera of the group. Anchor-like multicellular trichomes are features shared by Brya and Cranocarpus, which are the sister group to the other genera of the clade. Subepidermal layers are features shared by the Centrolobium, Etaballia, Paramachaerium, Pterocarpus and Tipuana genera, and the sclerenchyma sheath in the leaflet margin is reported in the Discolobium, Riedeliella and Platymiscium genera. Bulbous based glandular trichomes and vesicular glandular trichomes are diagnostic at the species level in Centrolobium and Pterocarpus, respectively. The leaflet characters investigated can be useful for the taxonomic delimitation at both the genus and species levels of the Pterocarpus clade. Our dataset provides new synapomorphies, elucidates the inter-generic relationships and reinforces the phylogenetic classification of the Pterocarpus clade resolved by molecular data.