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Key messageThe species did not show a response pattern to flooding. Andira anthelmia and Vernonanthura discolor invested in plastic responses, while Guarea guidonia established a balance between integration and phenotypic plasticity.Dense ombrophilous forests are tropical phytophysiognomies that make up the vegetation mosaic of the Brazilian Atlantic Forest. These forests occur in humid regions and often contain flooded areas that impose obstacles to plant colonization. Some species such as Guarea guidonia (Meliaceae), Andira anthelmia (Fabaceae), and Vernonanthura discolor (Asteraceae) can tolerate these flooding conditions. However, little is known about the acclimatization of these species to flooding. For this reason, morphoanatomical and physiological analyses were performed on the leaves of five individuals of each species selected from a flooded and non-flooded site. The results showed that the species presented thicker leaves and higher specific leaf mass values under flooding conditions. However, it was observed that the thickening of G. guidonia and V. discolor is mainly influenced by the palisade parenchyma thickness, while in A. anthelmia thickening was more closely related to the spongy parenchyma thickness. Greater thickening of the cuticle and epidermis and greater density of stomata were also observed in the flooded site. The chlorophyll a and b and carotenoid contents were significantly lower in the flooded site. Chloroplasts exhibited higher amounts of starch grain, lipid drops, and plastoglobules in the flooded site. Regarding the quantum yield of photosystems II, only A. anthelmia showed a reduction in Fv/Fm values in the flooded site. Plasticity and phenotypic integration analyses made it possible to conclude that the acclimatization of A. anthelmia and V. discolor was mainly mediated by plastic adjustments. At the same time, G. guidonia presented greater phenotypic integration.

Key messageLandscape changes due to urbanization are reflected in the wood anatomy of Atlantic Forest species.Human activities have generated environmental alterations worldwide. Such impacts affect the development of trees and are related to a series of changes in wood anatomy. Thus, the analysis of wood can increase the understanding of how environmental alterations influence the hydraulic functioning of trees and their strategies for dealing with fluctuations in resources. To better understand how the modification of the landscape by anthropic actions can affect tree species, this work describes and compares the anatomical structure of Guarea guidonia, an evergreen species native to the Atlantic Forest, growing in a well-preserved forest, a peri-urban forest and an urban park in the Rio de Janeiro State. Wood samples from trees of each of these areas were analysed using optical microscopy and data were statistically compared among sites. Significant differences were observed among trees of different sites, such as smaller vessel element diameter, wider bands of axial parenchyma and wider rays in the urban park and greater frequency of fibres in the well-preserved forest. Guarea guidonia showed intraspecific variation related to the urbanization of the city of Rio de Janeiro, with a gradient of adaptations observed in relation to the proximity to the urban centre. The wood anatomy reflects the tissue reparation of the trees and indicates this species as bioindicator for biomonitoring studies.

Hurricanes cause dramatic changes to forests by opening the canopy and depositing debris onto the forest floor. How invasive rodent populations respond to hurricanes is not well understood, but shifts in rodent abundance and foraging may result from scarce fruit and seed resources that follow hurricanes. We conducted studies in a wet tropical forest in Puerto Rico to better understand how experimental (canopy trimming experiment) and natural (Hurricane Maria) hurricane effects alter populations of invasive rodents (Rattus rattus [rats] and Mus musculus [mice]) and their foraging behaviors. To monitor rodent populations, we used tracking tunnels (inked and baited cards inside tunnels enabling identification of animal visitors' footprints) within experimental hurricane plots (arborist trimmed in 2014) and reference plots (closed canopy forest). To assess shifts in rodent foraging, we compared seed removal of two tree species (Guarea guidonia and Prestoea acuminata) between vertebrate‐excluded and free‐access treatments in the same experimental and reference plots, and did so 3 months before and 9 months after Hurricane Maria (2017). Trail cameras were used to identify animals responsible for seed removal. Rat incidences generated from tracking tunnel surveys indicated that rat populations were not significantly affected by experimental or natural hurricanes. Before Hurricane Maria there were no mice in the forest interior, yet mice were present in forest plots closest to the road after the hurricane, and their forest invasion coincided with increased grass cover resulting from open forest canopy. Seed removal of Guarea and Prestoea across all plots was rat dominated (75%–100% rat‐removed) and was significantly less after than before Hurricane Maria. However, following Hurricane Maria, the experimental hurricane treatment plots of 2014 had 3.6 times greater seed removal by invasive rats than did the reference plots, which may have resulted from rats selecting post‐hurricane forest patches with greater understory cover for foraging. Invasive rodents are resistant to hurricane disturbance in this forest. Predictions of increased hurricane frequency from expected climate change should result in forest with more frequent periods of grassy understories and mouse presence, as well as with heightened rat foraging for fruit and seed in preexisting areas of disturbance.

Despite frequent occurrences of invasive rats (Rattus spp.) on islands, their known effects on forests are limited. Where invasive rats have been studied, they generally have significant negative impacts on native plants, birds, and other animals. This study aimed to determine invasive rat distribution and effects on native plant populations via short-term seed removal trials in tropical rain forest habitats in the Luquillo Experimental Forest, Puerto Rico. To address the first objective, we used tracking tunnels (inked and baited cards inside tunnels enabling animal visitors’footprints to be identified) placed on the ground and in the lower canopy within disturbed (treefall gaps, hurricane plots, stream edges) and undisturbed (continuous forest) habitats. We found that rats are present in all habitats tested. Secondly, we compared seed removal of four native tree species (Guarea guidonia, Buchenavia capitata, Tetragastris balsamifera, and Prestoea acuminata) between vertebrate-excluded and free-access treatments in the same disturbed and undisturbed habitats. Trail cameras were used to identify animals responsible for seed contact and removal. Black rats (Rattus rattus) were responsible for 65.1% of the interactions with seeds, of which 28.6% were confirmed seed removals. Two plant species had significantly more seeds removed in disturbed (gaps) than undisturbed forest. Prestoea acuminata had the lowest seed removal (9% in 10 days), whereas all other species had >30% removal. Black rats are likely influencing fates of seeds on the forest floor, and possibly forest community composition, through dispersal or predation. Further understanding of rat–plant interactions may be useful for formulating conservation strategies.

This study analyzes the lipid composition and the oxidative stability of oils of Sapindaceae and Meliaceae seeds. The oil content ranged from 14.7% (Guarea guidonia) to 30.1% (Allophylus puberulus and Paullinia elegans). Ten fatty acids were identified in seed oils. Guarea guidonia seeds accumulated mainly oleic (44.9%) and linoleic (24.1%) acid, whereas the unusual gondoic and paullinic acids were identified in A. puberulus (15.8%; 8.9%) and P. elegans (14.4%; 44.2%), respectively. The oil of P. elegans had the highest oxidative stability (16.2 h.). Tocopherol predominated in A. puberulus (10.4 mg/100 g) and tocotrienol predominated in G. guidonea and P. elegans (2.6 mg/100 g). The vitamers α-tocopherol, γ-tocopherol, and γ-tocotrienol were found in the studied oils. β-carotene was predominantly detected in the oil of A. puberulus seeds (22.4 μg/g). Guarea guidonia seed oil has a high potential in food due to richness in essential fatty acids. In turn, A. puberulus and P. elegans oils could be suggested for other industrial purposes (e.g., biodiesel, varnishes, paints, soaps, or oleochemicals) due to their content of long-chain fatty acids.

Can the coffee berry borer (Hypothenemus hampei, or CBB) use host plants other than coffee for food and shelter? The use of fruits other than coffee has been reported. However, the validity of these reports depends on accurate identification of CBB, which is sometimes uncertain. In this study we sampled potential alternate hosts in coffee farms in Puerto Rico. Fruits with perforations were collected and examined for the presence of scolytid beetles (Coleoptera: Curculionidae: Scolytinae). Scolytids were identified by morphology and DNA barcoding of the COI gene. Association between the presence of Inga vera and Guarea guidonia trees and infestation rate of CBB in coffee fruits was evaluated. Food preference tests were performed in the laboratory. A total of 3563 beetles were found and 587 were identified as Hypothenemus spp.; of these, 85 identifications were confirmed by DNA barcoding. Twenty-seven of the beetles identified were H. hampei, mostly in I. vera fruits in periods between coffee crops. Most scolytids identified were H. obscurus. In preference tests, some CBB initially penetrated G. guidonia fruits, but eventually chose coffee. There was no evidence of feeding or reproduction in fruits of G. guidonia or Cajanus cajan. The results show that in Puerto Rico it is rare to find CBB in fruits of alternate hosts. The scarcity of coffee fruits in the off-season might cause some CBBs to take refuge in other fruits, but they did not feed or reproduce in them in laboratory tests. Understanding the refugia of CBB in the off-season may be useful for designing effective management strategies.

Human-impacted forests are increasing in extent due to widespread regrowth of secondary forests on abandoned lands. The degree and speed of recovery from human disturbance in these forests will determine their value in terms of biodiversity conservation and ecosystem function. In areas subject to periodic, severe natural disturbances, such as hurricanes, it has been hypothesized that human and natural disturbance may interact to either erase or preserve land use legacies. To increase understanding of how interactions between human and natural disturbance influence forest regeneration and recovery, we monitored seedlings in a human- and hurricane-impacted forest in northeastern Puerto Rico over a ∼10-yr period and compared seedling composition and dynamics in areas that had experienced high- and low-intensity human disturbance during the first half of the 20th century. We found that land use history significantly affected the composition and diversity of the seedling layer and altered patterns of canopy openness and seedling dynamics following hurricane disturbance. The area that had been subject to high-intensity land use supported a higher density, but lower diversity, of species. In both land use history categories, the seedling layer was dominated by the same two species, Prestoea acuminata var. montana and Guarea guidonia . However, seedlings of secondary-successional species tended to be more abundant in the high-intensity land use area, while late-successional species were more abundant in the low-intensity area, consistent with patterns of adult tree distributions. Seedlings of secondary-forest species showed greater increases in growth and survival following hurricane disturbance compared to late-successional species, providing support for the hypothesis that hurricanes help preserve the signature of land use history. However, the increased performance of secondary-forest species occurred predominantly in the low-intensity land use area, suggesting that hurricanes act to homogenize differences in species composition between areas with differing land use histories by increasing secondary-forest species regeneration in areas that experienced little direct human disturbance. Our results suggest that, through effects on seedling dynamics, hurricanes may extend the signature of land use history beyond the average recovery time of forests not subject to intense natural disturbance events.

Endophytes are microorganisms that live inside plant tissues without causing symptoms of disease. They are a largely unexplored component of biodiversity, especially in the tropics. In this study, leaves from two populations of Guarea guidonia trees (Meliaceae) in the Luquillo region, Puerto Rico, were screened for diversity and composition of endophytic fungal communities. A total of 268 leaf fragments from 14 trees were surveyed. Thirty-eight morphospecies of endophytes were found. Phomopsis, Colletotrichum, Xylaria, and Rhizoctonia-like fungi were the most abundant taxa. Over 95 percent of the leaf pieces had endophytes. Communities had a few abundant species and many species with few individuals. The fungal community from the Guarea population in a forest preserve was more diverse than that from a disturbed area. Fungal communities were stratified according to height within a tree, but no differences were found between blade, petiolule, and rachis. The data suggest that the smaller and the more scattered the plant fragments sampled, the higher the probability of approaching real diversity values of endophytic fungal communities.

Changes in land cover from forest to agriculture often alter riparian vegetation, which modifies the physical conditions of streams. To understand the impacts of different categories of land cover on riparian and stream habitats, we sampled riparian vegetation and stream conditions in three adjacent watersheds in southeastern Puerto Rico. Land cover categories (pasture, mixed, and forest) were determined using aerial photographs. Vegetation structure and composition and characteristics of streams were assessed for 35 riparian sites. Sites were located along first-order streams, at 400-600 m elevation in the wet-forest life zone. Understory vegetation in the forest sites was mainly shrubs, herbs, and ferns, whereas the mixed and pasture sites were dominated by grasses, vines, and bare soil. Syzygium jambos and Spathodea campanulata, nonnatives, and Guarea guidonia, a native, were the most common tree species in the riparian areas. Surrounding land cover explained >60% of the variation among stream sites. There was a positive relationship between tree cover and percentage of dissolved oxygen, and a negative relationship between tree cover and percentage of substrata covered by sediments from eroded soil. The amount of woody debris in the streams tended to increase with forest cover. Overall, land cover is a landscape feature that effectively characterized riparian understory cover, tree species composition, and stream condition.