In spite of environmental differences, P. reticulata from the Atlantic Forest and Cerrado showed similar phenological behavior with only about 10% of the total diversity being attributed to differences between biomes.

The Brazilian Atlantic Forest is a typically multi‐layer tropical forest, while cerrado (savanna) is a patchy habitat with different physiognomy. Despite these differences, both habitats have high light heterogeneity. Functional traits of Dalbergia nigra and D. miscolobium from the Atlantic Forest and cerrado, respectively, were evaluated under shade (25% of full sunlight) and full sunlight in a nursery experiment. We hypothesised that both species should benefit from high phenotypic plasticity in relation to light. Plasticity was estimated using the relative distance phenotypic index (RDPI). D. miscolobium had lower shoot growth under both light conditions, suggesting it has low competitive capacity in the forest environment, which could explain its limited ability to expand over areas of Atlantic Forest. The studied species exhibited photoprotection strategies under high light and improved light capture under low light. Stomatal conductance, ETRmax (maximum electron transport rate), PPFDsat (saturating photosynthetically active photon flux density), chlorophyll and carotenoid content had higher RDPI than stem morphological traits. Although both species showed considerable phenotypic plasticity, D. miscolobium had higher RDPI for eight of 11 evaluated traits. This high plasticity could be one of the factors that explain the occurrence of this species in a wide range of environmental conditions, from open grassland to dense woodlands, and it could also reflect its adaptation to high light. D. nigra also had considerable plasticity and good growth performance in both shade and full sunlight, but its absence in areas of cerrado suggests that factors other than light limit its occurrence in these habitats.

Senna multijuga and Plathymenia reticulata are tropical tree species native to the Brazilian Atlantic Forest and the Brazilian Cerrado, respectively. Seed-coat dormancy variation was evaluated within and among natural populations of these two species. Scarified and non-scarified seeds from different plants within populations were germinated at 28°C, and the percentage of germinated seeds was estimated for both species. Mean germination percentages of non-scarified seeds tended to be higher for P. reticulata populations (40 and 62%) than for S. multijuga populations (9 and 35%). After scarification, germination percentages increased significantly in both species, with all populations showing mean values above 84%. The level of seed dormancy, evaluated through the experiment with non-scarified seeds, differed significantly within and among populations of both species (P < 0.05). The values of the coefficient of genotypic determination were high for populations of both species (b = 0.85). Although this coefficient is an overestimation, since it includes non-genetic maternal effects, its high values suggest that a considerable part of the phenotypic variation in seed dormancy in S. multijuga and P. reticulata is of genetic origin. Variation in seed dormancy can be an important factor for increasing genetic diversity in populations of these species, making them able to respond to environmental changes.

Light intensity and heterogeneity are some of the main environmental factors that differ between forest and savanna habitats, and plant species from these habitats form distinct functional types. In this study, we tested the hypothesis that not only differences in morphological and physiological traits but also phenotypic plasticity in response to light are involved in adaptation to forest and savanna habitats by investigating ecotypic differentiation between populations of Plathymenia reticulata (Leguminosae: Mimosoideae), a tree from the Brazilian Atlantic Forest and the Brazilian Cerrado (savanna). Seeds from four natural populations (one from each biome core area and two from ecotonal regions) were grown in a common garden with four light treatments. Fifteen morphological and physiological characteristics were evaluated until individuals reached 6 mo old. Comparisons among populations showed differences for seven traits in at least one light treatment. These differences pointed to local adaptation to different biomes. Populations showed different levels of phenotypic plasticity in response to light in seven traits. Higher plasticity was found either in the forest core population or ecotonal populations; lower values were found in the cerrado core population. Lower plasticity in the cerrado population emphasizes the stress resistant syndrome, as lower plasticity is probably advantageous in a habitat where a conservative resource use is crucial. Higher plasticity in forest individuals suggests higher ability in exploiting the light heterogeneity in this habitat. Also, higher plasticity in ecotonal populations can be important to ensure the maintenance of P. reticulata in these temporally and spatially dynamic areas.Abstract in Portugese is available at http://www.blackwell-synergy.com/loi/btp.

ABSTRACT

Plathymenia reticulata is a tree species that occurs in two different Brazilian biomes, the Cerrado (a savannah environment), and the Atlantic Forest. In the present study, we evaluated morphological variation within and among five populations located in these vegetation types and in transitional sites in order to test the hypothesis that habitat selective pressures, being different in the Cerrado and the Atlantic Forest, would cause adaptive differences in morphological traits in individuals occurring under these different circumstances. Thirteen morphological traits of fruits, seeds, and of the membranous endocarp were obtained from 30 fruits and 20 seeds from each of nine to 10 individuals per population. Significant variation was found for all traits while comparing individuals within populations, and most traits varied significantly among populations as well. Some traits differed significantly between forest and Cerrado populations, while transition sites showed intermediate patterns and higher within-population variation. Contrary to our hypothesis, variation in seed size and mass among populations from different habitats was not significant. However, as predicted, the membranous endocarp was shorter for the seeds from Cerrado populations than from the Atlantic Forest. These data suggest the existence of P. reticulata ecotypes from Cerrado and Atlantic Forest; the relevance to Plathymenia evolution and to its wide ecological distribution is discussed.

The variability of ecophysiological traits among populations can be a result of selection in response to environmental pressure and/or due to random factors, like the genetic drift. The analysis of both genetic and phenotypic variation within populations can lead to better understanding of adaptation in order to colonize different habitats. In the last years we have developed several studies with an widely ecogeographic distributed legume tree species, Plathymenia reticulata, which were focused on identifying specific morphological and physiological traits related to adaptation to the habitats of origin of each studied population. We studied populations from Atlantic Forest, Cerrado and ecotonal sites in relation to phenology, seed morphological traits and their relation with seed dispersion, seed dormancy and germination, and growth traits in a common garden experiment. In several analyzed traits we found high diversity in this species that can explain its occurrence in a broad geographical range. The existence of genetically based differences of traits in an adaptive way among savanna and forest populations suggests a degree of divergence that characterizes the existence of ecotypes from Cerrado and Atlantic Forest. We also pointed future perspectives in studies at population level in evolutionary ecophysiology and implications of these studies for flora conservation and habitat restoration. Key words: Ecotypes, evolutionary ecophysiology, intraspecific variation, local adaptation Abordagem populacional em estudos ecofisiológicos: o caso de /Plathymenia reticulata/, uma árvore do Cerrado e da Mata Atlântica: A variação em características ecofisiológicas entre populações pode ser devido ao resultado da seleção em resposta a pressão ambiental e/ou pode ser devido a fatores aleatórios como a deriva genética. A análise tanto da variação genética quanto da variação fenotípica das populações, pode levar ao melhor conhecimento sobre adaptações necessárias para a ocupação de diferentes ambientes. Nos últimos anos, nós temos desenvolvido diversos estudos com populações de Plathymenia reticulata, uma leguminosa arbórea de ocorrência em ampla extensão ecogeográfica, com o objetivo de identificar características morfológicas e fisiológicas envolvidas na adaptação das populações aos seus ambientes de origem. Populações provenientes da Mata Atlântica, do Cerrado e de áreas ecotonais entre estes biomas foram avaliadas em relação à fenologia, morfologia e germinação de sementes, bem como em relação à características de crescimento de plantas cultivadas em um mesmo ambiente experimental. Em muitas das características analisadas nessa espécie foi encontrada grande diversidade, o que poderia explicar a sua ocorrência em uma ampla extensão geográfica. A existência de diferenças genéticas em características na direção adaptativa entre as populações provenientes de ambientes de savana e florestais sugere a existência de ecótipos de Cerrado e de Mata Atlântica. Nós também apontamos perspectivas futuras para estudos de ecofisiologia ...

The phenotypic plasticity to light of two congeneric species of leguminous trees from distinct habitats was evaluated in a common-garden experiment. For that, we assessed the following two groups of leaf morphological and anatomical traits of 1-year-old seedlings: (1) traits related to light interception (tissues thickness and leaflet mass per area), and (2) traits related to gas exchange (number of leaflets per leaf and measurements of stomatal size and density). Dalbergia nigra (Vell.) Allemão ex Benth. is an endemic Atlantic forest species, and D. miscolobium Benth. is a typical cerrado species. Both were grown under shade and full-sunlight conditions. The phenotypic plasticity of leaves was determined by a relative distance plasticity index (RDPI). For both species, sun leaflets were thicker than shade ones, and only D. nigra presented lower values for stomatal density (nst), percentage of the leaflet area occupied by stomatal pores (nast) and estimated stomatal conductance (gst) under shade conditions. The forest species (D. nigra) had higher plasticity for variables related to gas exchange (number of leaflets per leaf, nst, ast, nast and gst), whereas the cerrado species (D. miscolobium) had higher plasticity for variables related to light interception, such as leaflet mass per area, leaflet thickness and palisade and spongy parenchyma thickness. The degree of plasticity was different for each analysed parameter, and not used to define which species is more plastic. The leaf traits of D. nigra and D. miscolobium that showed high plasticity were related to resources that are not limiting to improve its photosynthesis in a changing light environment.