The Vestfold Hills are a 400 km2, isolated ice-free oasis in eastern Antarctica featuring large areas with translucent quartz rocks that provide habitat for hypolithic microbial communities underneath. We used high-throughput DNA sequencing of 16S and 18S ribosomal RNA amplicons to characterize bacterial and eukaryotic hypolithic communities across the Vestfold Hills. We found high-level, local heterogeneity in community structure consistent with limited dispersal between hypoliths. Hypolithic communities were dominated by heterotrophic Bacteroidetes (mean bacterial relative read abundance: 56%) as well as Cyanobacteria (35%), with the eukaryote component often dominated by Chlorophyta (43%). Small but significant proportions of the variation in microbial community composition and function were explained by soil salinity (5–7%) and water availability (8–11%), with distinct taxa associated with different salinities and water availabilities. Furthermore, many inferred bacterial metabolic pathways were enriched in hypolithic communities from either dry or high-salinity sites. Vestfold Hills hypolithic habitats are likely to be local refuges for bacterial and eukaryotic diversity. Gradients in soil salinity and water availability across the Vestfold Hills, in addition to the number and diversity of lake types and fjords as potential source populations, may contribute to the observed variation in the extremophile, hypolithic microbial community composition.

Mangroves are subject to rapid and large-scale habitat changes, which threaten their unique genetic diversity and provision of critically important ecosystem services. Habitat fragmentation reduces connectivity, which can impair dispersal and lead to genetic isolation. However, it is unclear whether fragmentation could impact mangrove genetic isolation, as mangrove propagules appear to be able to disperse long distances. Here, we conducted a meta-analysis of studies testing for a correlation between geographic distance and genetic distance in mangrove plants. From the 22 studies that met the inclusion criteria, we found a significant isolation-by-distance effect; geographic distance was significantly associated with Nei’s genetic distance and FST. Our results show that mangrove propagules may be limited in their capacity to disperse across long distances, which highlights the importance of maintaining close proximity between habitat patches and reducing habitat fragmentation.

Despite the great interest to quantify the structure of host–parasite interaction networks, the real influence of some factors such as taxonomy, host body size and ecological opportunity remains poorly understood. In this paper, we investigate the general patterns of organization and structure of interactions in two anuran–parasite networks in the Brazilian Pantanal (seasonally flooded environment) and Atlantic Forest (non-flooded forest). We present theoretical models to test whether the structures of these host–parasite interaction networks are influenced by neutrality, host taxonomy and host body size. Subsequently, we calculated metrics of connectance, nestedness and modularity to characterize the network structure. We demonstrated the structure networks were influenced mainly by body size and taxonomy of the host. Moreover, our results showed that the seasonally flooded environment present networks with higher connectance/nestedness and lower modularity compared to the other environment. The results also suggest that seasonal floods may promote ecological opportunities for new species associations.

Understanding why ecological communities contain the species they do is a long-standing question in ecology. Two common mechanisms that affect the species found within communities are dispersal limitation and environmental filtering. Correctly identifying the relative influences of these mechanisms has important consequences for our understanding of community assembly. Here variable selection was used to identify the environmental variables that best predict tropical forest primate community similarity in four biogeographic regions: the Neotropics, Afrotropics, Madagascar and the island of Borneo in South-East Asia. The environmental variables included net primary productivity and altitude, as well as multiple temperature, precipitation and topsoil variables. Using the best environmental variables in each region, Mantel and partial Mantel tests were used to reanalyse data from a previously published study. The proportion of variance explained increased for each region. Despite increases, much of the variation remained unexplained for all regions (R2: Africa = 0.45, South America = 0.16, Madagascar = 0.28, Borneo = 0.10), likely due to different evolutionary and biogeographic histories within each region. Nonetheless, substantial variation among regions in the environmental variables that best predicted primate community similarity were documented. For example, none of the 14 environmental variables was included for all four regions, yet each variable was included for at least one region. Contrary to prior results, environmental filtering was an important assembly mechanism for primate communities in tropical forests worldwide. Geographic distance more strongly predicted African and South American communities whereas environmental distance more strongly predicted Malagasy and Bornean communities. These results suggest that dispersal limitation structures primate communities more strongly than environmental filtering in Africa and in South America whereas environmental filtering structures primate communities more strongly than dispersal limitation in Madagascar and Borneo. For communities defined by genera, environmental distance more strongly predicted primate communities than geographic distance in all four regions, which suggests that environmental filtering is a more influential assembly mechanism at the genus level. Therefore, a more nuanced consideration of environmental variables affects conclusions about the influences of environmental filtering and dispersal limitation on primate community structure.

Recruitment success of individual plants is limited by an array of biotic and abiotic factors. Seedling survival may experience high mortality due to negative density dependence or altered microclimatic conditions. This study reports regeneration of Poulsenia armata (Moraceae), in the fragmented landscape of the Los Tuxtlas region in south-eastern Mexico. Density, survival and growth of seedlings (<1 y) and juveniles (<150 cm height) of P. armata were predicted to be significantly lower in forest fragments compared with extensive continuous forest. Contrary to expectation, density did not vary between habitats; however, we found twice the number of seedlings (n = 82) in forest fragments than in the continuous forest (n = 35). Forest fragments were associated with higher seedling densities close to adult trees. Unexpectedly, we found no evidence for negative density dependence in plant survival or growth. Survival and growth of P. armata were negatively impacted in forest fragments, with desiccation by warmer daily temperatures likely the cause of mortality, independent of density. Of the 111 individuals recorded in 2010 in forest fragments, 38% died over 2 y of census (n = 42), while 9% (n = 12) of the 127 individuals from the continuous forest died. Higher rates of mortality suggest that conditions in forest fragments are detrimental to seedling cohorts over time. Low juvenile recruitment jeopardizes persistence of P. armata, in fragmented populations of this rain-forest tree.

Trees of the family Dipterocarpaceae dominate the emergent canopy of most lowland rain forests in Asia (Ashton et al. 1988). The family is, therefore, one of the most ecologically important in South-East Asia. Shorea curtisii Dyer ex King is the most common tree species in the hill dipterocarp forests of Peninsular Malaysia (Burgess 1975, Symington 2004), and is considered a key species for the dynamics of such forests. Currently, most Malaysian hill forests are selectively logged. Trees over 50 cm dbh are harvested, and any subsequent harvests depend on the remaining smaller trees. Such selective logging takes no account of seedling regeneration. Hence, subsequent timber harvests rely on trees derived from the seedlings that are already present and future seeds produced by the residual trees (Appanah & Mohd. Rasol 1994). Existing seedlings of S. curtisii in the forest, therefore, play a significant role in the dynamics of the hill forest. However, the conditions that constitute a suitable habitat for S. curtisii seedling establishment and survival remain unknown.

Understanding tropical succession requires insight into propagule availability, which constrains possible woody plant recruitment, yet seed rain composition in multiple post-agricultural sites has seldom been examined. We monitored seed rain for 60 wk in five abandoned pastures in southern Costa Rica, collecting a total of 1 140 688 seeds of 165 morphospecies. Most seeds (80.1%) arrived during the wet season. Species richness was highest in the wet season and greater in forest than in pasture. Seed rain density was greatest at the forest/pasture edge and decreased drastically just a few metres into pastures. In and near the forest, animal-dispersed seeds were more abundant than seeds dispersed by other means, while wind-dispersed taxa increased in relative importance at greater distances from the forest. Total seed input to pastures did not reflect size of adjacent forest fragments, although seed rain density varied more than threefold among sites. Among-site variation in density of regenerating woody seedlings was roughly proportional to among-site variation in seed rain. Morphospecies composition differed significantly among sites. Also, seed rain and woody plant colonists were rather dissimilar in composition, suggesting that while propagule availability is necessary for early woody plant establishment, it is a poor predictor of successional trajectory.

We used regression models and information-theoretic model selection to assess the relative importance of environment, local dispersal and historical contingency as controls of the distributions of 26 common plant species in tropical forest on Barro Colorado Island (BCI), Panama. We censused eighty-eight 0.09-ha plots scattered across the landscape. Environmental control, local dispersal and historical contingency were represented by environmental variables (soil moisture, slope, soil type, distance to shore, old-forest presence), a spatial autoregressive parameter (ρ), and four spatial trend variables, respectively. We built regression models, representing all combinations of the three hypotheses, for each species. The probability that the best model included the environmental variables, spatial trend variables and ρ averaged 33%, 64% and 50% across the study species, respectively. The environmental variables, spatial trend variables, ρ, and a simple intercept model received the strongest support for 4, 15, 5 and 2 species, respectively. Comparing the model results to information on species traits showed that species with strong spatial trends produced few and heavy diaspores, while species with strong soil moisture relationships were particularly drought-sensitive. In conclusion, history and local dispersal appeared to be the dominant controls of the distributions of common plant species on BCI.

An estimated 154 million ha of tropical forest are cleared each year by human activities such as cattle ranching and agriculture (Whitmore 1997). When the economic return of these sites declines, they are often abandoned and allowed to regenerate. As a result, ‘secondary’ or ‘regenerating’ forests are becoming an increasingly common feature in tropical landscapes (Guariguata & Ostertag 2001). Unlike treefall gaps and other ‘naturally’ disturbed areas, the regeneration of secondary forests on anthropogenically disturbed lands does not always follow a predictable pathway (reviewed in Guariguata & Ostertag 2001). Instead, the type and intensity of post-clearing land use has major implications for the trajectory along which succession proceeds (Guariguata & Ostertag 2001, Mesquita et al. 2001, Uhl et al. 1988).

Tropical forests can recover after anthropogenic disturbances of light to moderate intensity (Aide et al. 1995, 1996, 2000; Uhl 1987, Uhl et al. 1988); however, severe disturbances (e.g. compaction or loss of soil) often result in conditions that prevent forest recovery. These degraded sites are often dominated by grasses (Aide & Cavelier 1994, Cabin et al. 2002, Cavelier et al. 1998, Uhl et al. 1988) and ferns (Cohen et al. 1995, García et al. 1994, Slocum et al. 2000, Walker & Boneta 1995) that can impose barriers for tree regeneration and arrest the succession process. Important barriers for tree regeneration include: (1) competition with grasses and ferns for soil moisture, nutrients and light (Aide & Cavelier 1994, Guimarães-Vieira et al. 1994, Holl et al. 2000, Nepstad et al. 1996, Russell et al. 1998, Walker 1994, Zimmerman et al. 2000), and (2) dispersal limitation given that grasses and fernlands offer few resources that attract seed dispersers (Guevara & Laborde 1993, Holl et al. 2000, McDonnell & Stiles 1983, Slocum & Horvitz 2000, Zimmerman et al. 2000).

The study presented here investigated the importance of environmental heterogeneity and clumping for the mesoscale distribution patterns of five palm species in old-growth Andean forest (Maquipucuna, Ecuador). Seedlings, juveniles and adults were recorded in 167 plots located throughout the 3-km × 3-km study area. Mountain (Cerro Sosa or Cerro Sta. Lucia), altitude, aspect, topographic-edaphic conditions and forest structure were also recorded. The following questions were investigated: (1) Are the distributions related to environmental heterogeneity? (2) Are the distribution patterns consistent with severe recruitment limitation? The distribution patterns of four species were related to environmental heterogeneity, especially to that created by the mountainous landscape itself, and at least four of the five species also exhibited strong clumping that was clearly linked to spatially restricted recruitment and could not be explained by the environmental parameters. Thus, both niche specialization and recruitment limitation probably play important roles in Andean palm community ecology. Consistent differences among the two mountains in forest structure and the frequency of certain palm stages most likely reflected extractivism.