The role of canopy gaps in tropical dry forest (TDF) dynamics remains unclear. Here, 75 canopy gaps, mostly formed by the fall of Bursera spp. and Pachycereus pecten-aboriginum individuals, are described, and their potential consequences for forest regeneration are analysed in a Mexican TDF. In 50 randomly selected gaps, understorey vegetation was sampled with a paired design (inside and outside gaps) and by distinguishing two plant height categories. In total, 1940 plants were recorded (63% in gaps and 37% in non-gap plots). Community attributes (density, community cover, taxonomic richness and Shannon diversity) were significantly higher for both height categories in gap plots. Conversely, neither an NMDS ordination nor a multinomial classification of 187 species by habitat affinities revealed floristic segregation between gaps and non-gaps; almost all species were classified as habitat generalists, with only a few opportunistic forbs (but no single tree species) being classified as gap specialists. The most important effects of gap formation are significant increases in plant abundance and species richness, but not a different species composition. Against earlier views that gap-phase dynamics is inconsequential for TDF dynamics, these results suggest a more active, albeit modest, role of treefall gaps in TDF, through promoting an abundant establishment.

Canopy gaps create a temporary spatial heterogeneity, often allowing pioneer species to establish and grow in mature forests. In this study, we asked whether the above model holds for tropical dry forests in the Florida Keys. Six hundred and forty-eight canopy gaps in an extensive Key Largo forest were identified with a LiDAR digital canopy model. The structure and composition of juvenile trees were examined in 45 selected gaps in three stands of known age, and weighted averaging calibration and regression were applied to the data to determine the successional age optimum for each tree species, and the inferred age for each gap based on its sapling composition. Less than 1% of the forest area was recorded as canopy gaps in the LiDAR model. The inferred stand ages were about 70 y greater in canopy gaps in young forest than in the surrounding, unimpacted forest. This suggested that gap formation advanced succession rather than reversing or resetting it. The apparent lack of recruitment by early-successional species may be due to the small size of canopy gaps in this forest, and the minimal contrast between gap and understorey environments; light and water conditions in the small gaps may favour late-successional rather than pioneer species. Establishment of pioneer species may not take place without intense, large-scale disturbances such as fires and hurricanes that remove the entire canopy and consume or erode soils.

We studied the vegetation and soil properties of a dry forest that had once been disturbed in central Myanmar using 30 quadrats (20 × 20 m) established in 2012. For 30 species, the overall density was 706 individuals ha−1, and the basal area was 2.92 m2 ha−1. The forest was a mosaic of six community types, each of which was dominated by a single species. Dominant species that were capable of resprouting accounted for 47–78% of the total density and 56–83% of the basal area of the communities. We related seven soil properties to the vegetation patterns using canonical correspondence analysis (CCA). The CCA results highlighted remarkable associations of species such as Acacia catechu, Dalbergia paniculata, Terminalia oliveri and Millettia multiflora with soil texture. Acacia inopinata was associated with a high soil pH (i.e. 9–10), and Terminalia tomentosa was associated with soil hardness. Our results indicate that secondary succession of a dry forest is not initially led by pioneer species, but instead, by superior competitors capable of resprouting, and that species distributions are primarily determined by the filtering effects of edaphic conditions. We believe that the dry-forest species retain their soil–species relationships despite heavy disturbances.

We examined quantity and quality components of primary seed dispersal for an assemblage of sigmodontine rodents in a high-elevation montane tropical forest in Peru. We collected faecal samples from 134 individuals belonging to seven rodent species from the subfamily Sigmodontinae (Cricetidae) over a 2-y period. We conducted seed viability tests for seeds found in faecal samples. We identified seeds from eight plant families (Bromeliaceae, Annonaceae, Brassicaceae, Ericaceae, Melastomatacae, Myrtaceae, Rosaceae, Solanaceae), nine genera and 13 morphospecies. The most abundant seeds belonged to Gaultheria sp. 1 (46% of total) and Miconia sp. 1 (31% of total), while the most viable seeds belonged to Greigia sp. (84% viability) and Guatteria sp. (80% viability). We utilized relative rodent abundance, seed species diversity, seed abundance and seed viability per rodent species to calculate an index of rodent disperser effectiveness, and found that Thomasomys kalinowskii was the most effective disperser, followed by Akodon torques, Calomys sorellus, Thomasomys oreas, Oligoryzomys andinus and Microryzomys minutus. Plant genera dispersed by sigmodontine rodents overlapped more with bird- and terrestrial-mammal-dispersed plants than with bat-dispersed plants. Future neotropical seed dispersal studies should consider small rodents as potential seed-dispersers, especially in tropical habitats where small-seeded, berry-forming shrubs and trees are present.

The Atlantic forest is the biome most severely affected by deforestation in Brazil. Cabralea canjerana spp. canjerana is a dioecious tree species with widespread distribution in the Neotropical region. This species is considered a model to ascertain population ecology parameters for endangered plant species from the Atlantic forest. Fine-scale spatial genetic structure and pollen-mediated gene flow are crucial information in landscape genetics and evolutionary ecology. A total of 192 adults and 121 offspring were sampled in seven C. canjerana populations in the Southern Minas Gerais State, Brazil, to assess whether pollen-mediated gene flow is able to prevent spatial genetic structure within and among Atlantic forest fragments. Several molecular ecology parameters were estimated using microsatellite loci. High levels of genetic diversity (HE = 0.732) and moderate population structure (θ = 0.133) were recorded. No significant association between kinship and spatial distance amongst individuals within each population (Sp = 0.000109) was detected. Current pollen-mediated gene flow occurs mainly within forest fragments, probably due to short-distance flights of the pollinator of C. canjerana, and also the forest fragmentation may have restricted flight distance. The high levels of genetic differentiation found amongst the seven sites sampled demonstrated how habitat fragmentation affects the gene flow process in natural areas.

The Virginia opossum (Didelphis virginiana) is considered highly adaptable to anthropogenic disturbances; however, the genetic effects of disturbance on this marsupial have not been studied in wild populations in Mexico. Here we evaluated the genetic diversity of D. virginiana at sites with different levels of disturbance within the Highlands and Central Depression regions of Chiapas in southern Mexico. Twelve microsatellite loci were used and the results demonstrated moderate mean heterozygosity (He = 0.60; Ho = 0.50). No significant differences in heterozygosity were found among sites with different levels of disturbance in both regions (range Ho = 0.42–0.57). We observed low but significant levels of genetic differentiation according to disturbance level. The inbreeding coefficient did not differ significantly from zero, suggesting that low genetic differentiation in these environments may be associated with sufficient random mating and gene flow, a result associated with the high dispersal and tolerance characteristics of this marsupial. Our results for D. virginiana in this particular area of Mexico provide a foundation for exploring the impact of human disturbance on the genetic diversity of a common and generalist species.

Frogs are known to occasionally utilize the burrow systems of subterranean rodents, but this phenomenon has previously attracted little attention. We recorded frogs in burrows and in/under the molehills of three African mole-rat species (Bathyergidae, Rodentia) during burrow system mapping in Malawi and Zambia during the dry season. Eight frog species were detected. The most abundant of them, Kassina senegalensis, was found in large numbers in active Ansell's mole-rat nest areas, obviously tolerated by the hosts. We speculate that in areas with prolonged dry seasons mole-rats may increase anuran abundances and diversity.

Leaf traits of tropical tree species are known to operate as intrinsic determinants of insect herbivory. However, we know little about how habitat fragmentation affects these traits and what, if any, are the consequences of this process on herbivory. We tested the effects of forest fragmentation on the leaf traits of sapling of four light-demanding species: Acalypha diversifolia, Hampea nutricia, Myriocarpa longipes, Siparuna thecaphora, and two shade-tolerant species: Pseudolmedia glabrata and Garcinia intermedia, in Los Tuxtlas, Mexico. We also conducted an acceptability assay with a generalist herbivore Spodoptera frugiperda. Plant traits did not change with forest fragmentation, but did with plant regeneration mode and species identity. Light-demanding species had significantly higher water content, nitrogen concentration and specific leaf area than shade-tolerant species. The latter had significantly higher leaf strength, carbon concentration and carbon:nitrogen ratio. Acceptability was affected by fragmentation but only in P. glabrata; plant tissue from forest fragments was consumed 2.6 times more than that from continuous forest. We conclude that forest fragmentation did not affect leaf traits in this site.

Defensive chemicals in anuran skin secretions function in protection against potential predators. Although studies have demonstrated that particular chemicals are effective against certain predators, very little is known about how different chemicals from different species function against the same predators. Understanding how different chemicals function as a defence against similar predators is fundamental to the ecology and evolution of chemical defences in frogs. In the present study, the defensive function of bufadienolide-based defences in adult Rhaebo haematiticus (Bufonidae) were compared with alkaloid-based defences in adult and juvenile Dendrobates auratus (Dendrobatidae) against the same predators. Most bufonids contain synthesized bufadienolides, whereas dendrobatids contain dietary-derived alkaloids. Predation trials were performed with two potential invertebrate predators, Paraponera clavata (bullet ant) and Cupiennius coccineus (ctenid spider), to determine how these predators respond to two different types of frog chemical defence. The non-chemically defended frog Craugastor fitzingeri served as a control in all predation trials. Our results suggest that bufadienolide defences of R. haematiticus and alkaloid defences of D. auratus are equally effective towards bullet ant and ctenid spider predators. The similar avoidance and cleaning behaviours exhibited by these ants and spiders after contact with bufadienolides and alkaloids suggest that both types of defence are unpalatable to these arthropod predators.

Circadian use of time is an important, but often neglected, part of an animal's niche. We compared the activity patterns of the Neotropical otter Lontra longicaudis in two different areas in Brazil using camera traps placed at the entrance of holts. We obtained 58 independent photos in the Atlantic Forest (273 camera trap-days) and 46 photos in Pantanal (300 camera trap-days). We observed different kernel density probabilities on these two areas (45.6% and 14.1% overlap between the 95% and 50% density isopleths respectively). We observed the plasticity in Neotropical otter activity behaviour with different activity patterns in the two areas. In the Pantanal, the Neotropical otter selected daylight (Ivlev = 0.23) and avoided night (Ivlev = −0.44), while in the Atlantic Forest it selected dawn (Ivlev = 0.24) and night (Ivlev = 0.14), avoiding daylight (Ivlev = −0.33). We believe that this pattern can be due to human activity or shifts in prey activity.

Wood density and wood chemical traits are strong predictors of tree performance, carbon stock, and wood decomposition, which play important roles in ecosystem processes and carbon and nutrient cycling in forests. However, it remains unknown how root wood traits are related to stem wood traits. We examined the relationships of wood density and wood chemical traits (lignin and nitrogen concentrations, carbon-to-nitrogen ratio) between the stems and coarse roots of 90 individuals representing 53 tropical tree species in Malaysian Borneo. We developed regression equations of each wood trait using the standardized major axis method. Each root wood trait was highly correlated with the corresponding stem wood trait, and most regression equations fitted well (R2 > 0.5). The lignin concentration of roots was significantly greater than that of stems. We conclude that root wood traits can be estimated from the corresponding stem wood traits in South-East Asian tropical trees. Further analysis of coarse root decomposability will provide more accurate estimates of carbon and nutrient fluxes in tropical forest ecosystems.