Species abundances and richness are central parameters in ecology and crucial for describing diversity and composition across environments. Understanding how they vary in natural environments is critical for informed conservation decisions, especially in the face of anthropogenic pressures, such as deforestation and climate change. We evaluate the influence of landscape and local habitat variables on the richness and abundances of lizards in the Caatinga, the largest continuous block of seasonally dry tropical forests. We sampled seven lizard communities for three months using visual encounters along transects. We recorded landscape and microhabitat variables and evaluated their influence on lizard species richness, diversity, and occurrence using model selection. Ten lizard species were recorded, with Tropidurus semitaeniatus, Ameivula ocellifera, and Tropidurus hispidus being the most abundant. Topographic complexity and the number of rocky outcrops positively affect species richness and diversity by promoting environmental heterogeneity and hence increasing refuges, shelters, and thermoregulation sites. Different microhabitat and landscape variables were important predictors of the occurrences of individual lizard species. The quantity of rocks significantly increased the likelihood of Tropidurus semitaeniatus occurrence, while litter negatively affected Tropidurus hispidus, and fallen logs increased the probability of Ameiva ameiva occurrence. We argue that preserving topographically complex regions is essential for maintaining the diversity of lizards in the Caatinga biome.

Boswellia papyrifera (Del.) Hochst is a flagship species of semi-arid areas of the East African region with substantial economic, ecological and cultural values. However, its persistence is currently threatened by both anthropogenic and natural pressures. This calls for an immediate conservation action. Planting seedlings of B. papyrifera in natural habitats using nursery-grown seedlings from seed and cuttings has been little successful. Fencing of naturally regenerated seedlings (wildlings) established under the parent trees could be used as an alternative option. The objective of this study was to examine the effect of fencing on the seedling establishment and growth of B. papyrifera wildlings. The experiment was conducted using 36 plots in fenced and open conditions. The results showed that fencing significantly enhances the establishment and growth of B. papyrifera wildlings compared to the open areas. Fenced wildlings exhibited higher survival rates, increased height, greater leaf numbers, larger root collar diameters, larger leaf areas and higher leaf biomass compared to non-fenced wildlings. Therefore, the protection of B. papyrifera seedlings using a fencing intervention can improve the overall establishment and development of B. papyrifera seedlings, thereby contributing to the sustainable conservation and restoration of this valuable species.

Seed germination is regulated by temperature and can thus be quantified by thermal models, which can predict germination occurrence in biomes and plant survival under possible climate change scenarios. The objective of this study was to quantify germination based on thermal time and survival risk of 14 species in the Brazilian Cerrado in scenarios of future climate change. Seeds were collected in the warmer regions of the Cerrado, central Brazil, placed in incubators to germinate at constant temperatures of 10–50°C and evaluated every hour or day. Germination rate (R50), time for germination of 50% of the seeds (T50) and dent-like function were used to determine cardinal temperatures. Thermal time parameters were estimated using the Weibull model. Seed germination forecasts were made based on the International Panel on Climatic Change (IPCC) scenarios of global temperature increase. Base temperatures (Tb) ranged from 3.5 to 16.5°C, maximum temperatures (Tmax) from 35 to 50°C and optimum temperatures (To) from 30 to 35°C. Estimated thermal time varied from 484°C h to 400°C d at sub-optimal temperatures and 108°C h at 126°C d at supra-optimal temperatures. Species more distributed showed a higher thermal range of germination and are less susceptible to extinction in temperature increase scenarios. The results of this study suggest that seeds that are non-dormant after dispersal may be the most vulnerable in the future. In this context, our predictions contribute to understand how the survival of trees and shrubs will be affected in the Cerrado in the future.

Unlike well-known global patterns of plant species richness along altitudinal gradients, in the mountainous areas of the Brazilian Caatinga, species richness and diversity reach their maxima near mountain tops. The causes of this unusual pattern are not well understood, and in particular the role of edaphic factors on plant community assembly along these gradients has not been investigated. Our goal was to assess the role of edaphic factors (fertility and soil texture) on plant community composition and structure on two mountains of the Brazilian semi-arid region. In 71 plots (Bodocongó site, twenty-one 200-m2 plots, 401–680 m asl; Arara site, fifty 100-m2 plots, 487–660 m asl) we recorded 3114 individuals representing 61 plant species; in addition, at each plot we collected composite soil samples from 0–20 cm depth. Significant altitude-related changes were observed both for community structure and composition, and edaphic variables. A canonical correspondence analysis allowed the distinction of two groups of plots according to species abundances, indicating a preferential habitat distribution of species depending both on altitude and soil variables. Although soil fertility was lowest at the highest altitudes, these areas had high richness and diversity. Conversely, the more fertile foothills were characterized by the dominance of generalist pioneer species. Despite the relatively short altitudinal range that characterizes the studied mountains, this study elucidates the role of edaphic factors on the floristic composition and species richness patterns on the mountains of the Brazilian semi-arid region.

Although extrafloral nectar (EFN) is a key food resource for arboreal ants, its role in structuring ground-nesting ant communities has received little attention, despite these ants also being frequent EFN-attendants. We investigated the role of EFN as a driver of the spatial structure of ground-nesting ant communities occurring in dry forest in north-eastern Brazil. We examined the effects on this relationship of two global drivers of biodiversity decline, chronic anthropogenic disturbance and climate change (through decreasing rainfall). We mapped EFN-producing plants and ant nests in 20 plots distributed along independent gradients of disturbance and rainfall. We categorized ant species into three types according to their dependence on EFN: heavy users, occasional users and non-users. We found a strong relationship between ant dependence on EFN and nest proximity to EFN-producing plants: heavy-users (mean distance 1.1 m) nested closer to EFN-producing plants than did occasional users (1.7 m), which in turn nested closer to EFN-producing plants than did non-users (2.3 m). Neither disturbance nor rainfall affected the proximity of heavy-user nests to EFN-producing plants. Our study shows for the first time that EFN is a key driver of the spatial structure of entire communities of ground-nesting ants.

Pollen and charcoal records from two large, shallow lakes reveal that throughout most of the past 50,000 yr Noel Kempff Mercado National Park, in northeastern lowland Bolivia (southwestern Amazon Basin), was predominantly covered by savannas and seasonally dry semideciduous forests. Lowered atmospheric CO2 concentrations, in combination with a longer dry season, caused expansion of dry forests and savannas during the last glacial period, especially at the last glacial maximum. These ecosystems persisted until the mid-Holocene, although they underwent significant species reassortment. Forest communities containing a mixture of evergreen and semideciduous species began to expand between 6000 and 3000 14C yr B.P. Humid evergreen rain forests expanded to cover most of the area within the past 2000 14C yr B.P. coincident with a reduction in fire frequencies. Comparisons between modern pollen spectra and vegetation reveal that the Moraceae-dominated rain forest pollen spectra likely have a regional source area at least 2–3 km beyond the lake shore, whereas the grass- and sedge-dominated savanna pollen spectra likely have a predominantly local source area. The Holocene vegetation changes are consistent with independent paleoprecipitation records from the Bolivian Altiplano and paleovegetation records from other parts of southwestern Amazonia. The progressive expansion in rain forests through the Holocene can be largely attributed to enhanced convective activity over Amazonia, due to greater seasonality of insolation in the Southern Hemisphere tropics driven by the precession cycle according to the Milankovitch Astronomical Theory.

To identify forests of high priority for conservation in tropical dry forests of New Caledonia, Fiji, the Marquesas and Hawaii, we examined patterns of woody plant species richness (total, native and endemic) and threatened species (IUCN categorization and density) at the stand level, using Gentry's transect method. There were associations between total, native and endemic plant species richness in all four Pacific dry forest regions but we found no significant association with the presence or density of species listed on the IUCN Red List. Dry forests in New Caledonia and Hawaii merit the highest conservation priority in the Pacific, based on level of endemism and number of threatened species. The study sites that merit high conservation priority are Metzdorf, Nekoro and Pindai, in New Caledonia, Kokee and Kaupulehu, in Hawaii, and Vatia, in Fiji. New Caledonia and Fiji have a small dry forest extent and protected area extent compared with other dry forests in biodiversity hotspots. Although we identified priority areas for dry forest conservation, more comparative plot data, presence/absence data in fragments and regional geographical data are needed to adequately manage and protect dry forests in the Pacific.

This study aimed at developing allometric models from destructive sample field data for estimating both aboveground and belowground tree biomass and assessing changes in root biomass after old-growth Brachystegia-Julbernardia (miombo) woodland clearing in central Zambia. Logarithmic linear models were selected for estimating tree biomass because they gave the most accurate (low mean error) predictions. On average aboveground and belowground biomass in regrowth woodland represented 29% and 41%, respectively, of the biomass in old-growth woodland. The root:shoot ratios were 0.54 and 0.77 in old-growth and regrowth woodland, respectively. Ten years after clear-cutting old-growth woodland, root biomass loss was about 60% of the original biomass. The main cause of post clearing root biomass loss was fire which at the study sites occurred annually or biannually. Control of fire in cleared sites should be encouraged in forest management for carbon storage and sequestration in miombo woodland of southern Africa.

We identified and quantified regional and local environmental factors and spatial variation associated with tree-species composition across a 2000-m altitudinal gradient of Andean forest in north-western Argentina. A network of 47 1-ha plots was established along the altitudinal gradient within an area of about 25 000 km2; all trees ≥ 10 cm dbh were identified and measured. Constrained ordinations and variance-partitioning analyses were performed to investigate the determinants of tree-species distribution at the regional scale, across and within forest types (i.e. dry and cloud forests). We marked and measured a total of 22 240 trees belonging to 160 species. Significant environmental factors and spatial location combined accounted for 35% of total variation explained. A high proportion of variation was explained by climatic factors that were spatially structured; after removing the spatial effect, climate explained more variation in species composition across the complete gradient than did local factors. Relative importance of regional and local factors varied with geographic extent. Local factors explained more variation in tree-species composition at the within-forest scale than at the scale of the complete gradient. Our findings support the conceptual model of multi-scale controls on vegetation distribution, where local community composition and abundance result from processes at both regional and local scales.

The fate of seeds of eight tree species was followed during 4 y of storage in the soil of an Afromontane forest at Gara Ades in the eastern highlands of Ethiopia. Seeds were enclosed in nylon mesh bags and buried at 5 cm soil depth. The bags were exhumed at intervals and the viability of the seeds was assessed by germination and cutting tests. Seeds of Bersama abyssinica and Ekebergia capensis germinated in the soil almost completely within a year after burial. The seeds of Juniperus procera, Olea europaea and Podocarpus falcatus also germinated to a substantial degree in the soil but with a distribution over several years, and some seeds of these species remained viable at the end of the 4-y period. Germination in the soil was very low in seeds of Acacia abyssinica and Croton macrostachyus throughout the whole burial period and the seeds kept their viability. In C. macrostachyus fresh seeds were highly dormant, but after 3 y or more in the soil they germinated readily in the laboratory suggesting an altered dormancy with time in the soil. Dormancy in seeds of A. abyssinica and Indigofera rothii was not altered throughout the study period as evidenced by marginal or no germination during incubation in the laboratory. The differential seed behaviour observed during storage in the soil can be an indicator of the regeneration strategy of the species studied. B. abyssinica, E. capensis, J. procera, O. europaea and P. falcatus form seedling banks on the forest floor and lack persistent soil seed reserves in contrast to A. abyssinica, C. macrostachyus and I. rothii which accumulate reserves of long-lived seeds in the soil. The generally high levels of dormancy and somewhat extended viability in the soil, even in several of the species producing seedlings in undisturbed forest, may have been selected for under a climate of seasonal drought and unreliable rainfall that characterizes this region.

As forest fragmentation and intentional burning of grasslands increase, the frequency of fires penetrating the dry and subhumid tropical forests of Bolivia is also likely to increase. To expand our understanding of the role of fire in tropical dry forest, the physical and thermal properties of barks of tree species were studied to determine their relative resistances to cambial damage by fire. For 16 tree species found in the dry forest of the Lomerío region of eastern Bolivia, bark thickness, moisture content, and specific gravity were measured. Insulating capabilities of bark were measured by obtaining cambial and surface temperatures during experimental wick fires. Bark thickness on trees 5-100 cm dbh (diameter at 1.4 m) ranged from 2–51 mm and both thick- and thin-barked species were represented. For all species, bark thickness increased as stem diameter increased. Bark thickness explained more (63%) of the variation in peak cambial temperatures during fires than did bark moisture content (4%) or specific gravity (1%). A threshold bark thickness of 18 mm was associated with the ability to withstand lethal cambial temperatures during the experimental, low intensity fires. For 13 of the 16 species included in this study, trees ≤20 cm dbh have bark thickness below the threshold 18 mm and, therefore, are likely to experience cambial injury from low intensity fires. Our results suggest that the forest presently characteristic of the Lomerío region did not develop with frequent fires and that species composition is likely to be substantially affected by an increase in fire frequency.

Western Madagascar's dry forests have suffered greater levels of deforestation than the island's humid eastern forests, and many of the largest remaining contiguous tracts of dry forest are conserved in Kirindy Mite National Park. To assist Kirindy Mite's management plan, we assessed land cover change in and around the Park, remotely sensing forest cover within the Park and an arbitrary 5-km buffer from Landsat images taken in 1990, 2000 and 2006. We then quantified forest cover and change and compared the values between the Park and buffer, interpreting the results through expert knowledge of the area. Kirindy Mite had lower rates of deforestation, higher rates of reforestation, and less net change than the unprotected zone in both 1990–2000 and 2000–2006. Park deforestation rates were approximately one third to one fourth those of the buffer, and Park reforestation rates were approximately double those of the buffer. Net change in the Park fluctuated between the two periods, with deforestation during 2000–2006 slightly exceeding reforestation during 1990–2000. All land cover changes accelerated over the study period, and disturbances in the Park were most frequent near its boundary. To maintain the forest as differences in forest cover across the Park boundary increase, we suggest including or intensifying measures to: (1) expand the Park boundary, simplifying its shape, (2) cooperate with the local people in managing a buffer zone, and (3) increase monitoring to minimize anthropogenic disturbances crossing the Park boundary.

The Endangered Madagascar giant jumping rat, Hypogeomys antimena, has suffered a major decline in distribution and is now restricted to two seemingly unconnected sub-populations in the largest remaining fragment of deciduous, seasonally dry forest in Menabe, western Madagascar. In a previous study a rapid decrease in numbers of H. antimena was observed in relatively intact forest, suggesting a factor of population decline additional to habitat loss, and provoking fears of a negative trend occurring across its remaining range. In the current study we conducted extensive line transect surveys to estimate active H. antimena burrow density in 2004 and 2005 as an index of population size, and trapping to estimate mean group size, as a multiplier for population size estimation. Within the surveyed areas we estimated the combined size of the two H. antimena sub-populations in 2005 to be c. 36,000, considerably larger than previously assumed. There was no evidence that active burrow density across the species’ known range changed between 2000 and 2005. H. antimena was not uniformly distributed, with higher densities of active burrows found in forest with the highest canopy in areas furthest from forest edges. These core forest areas are vital for the species’ conservation and the recent declaration that the Menabe forest will receive statutory protection provides hope that H. antimena may be safeguarded. However, given its restricted range and low reproductive output, among other factors, H. antimena remains threatened and requires close future monitoring.

The Madagascar flat-tailed tortoise Pyxis planicauda is threatened with extinction through loss of its deciduous, dry forest habitat and illegal collection for the pet trade. Little is known of the population status of this species as no systematic survey across its range has previously been conducted. Surveying P. planicauda is problematic as it has cryptic colouration, is only active during the wet season, and spends periods of time hidden under leaf litter. In this study we designed a line transect survey, which incorporated an approximation of the amount of time tortoises were available for sampling, to produce an unbiased estimate of population size. We estimated density of P. planicauda in the main forest block in central Menabe, which represents the majority of its range, to be 0.40 ha-1 with a total population size of nearly 28,000 individuals (95% confidence interval 16,323-47,669). This estimate is substantially higher than previous predictions of <10,000 individuals. Nevertheless, the species faces ongoing threats from deforestation and probably from illegal collection, although the recent designation of the Menabe forest as a protected area will probably help reduce these threats. This study provides a baseline density estimate of P. planicauda and a survey protocol for monitoring future population trends.

To study vertical gradients of arthropod species richness in tropical forests, adult chrysomelids were surveyed with similar sampling effort by beating in four plots of 0.8 ha, representative of the canopy and understorey of one wet and one dry forest in Panama. Samples included in total 4615 individuals representing 253 species, and were of similar species richness at the two study sites. At both sites, chrysomelids were significantly more species-rich in the canopy than in the understorey. The proportion of species shared between the two study sites was 24%, whereas 16% and 28% of species were shared between the canopy and understorey of the wet and dry sites, respectively. Mature trees supported more and different chrysomelid species than conspecific saplings. A higher proportion of liana feeders vs. tree feeders occurred at the dry site than at the wet site. Multivariate analyses confirmed the faunal differences between the wet and dry sites and that stratification was more marked at the wet site than at the dry site. The latter observation may relate to differences in forest physiognomy (a tall and closed canopy at the wet site) and to the high interconnectivity via lianas between the understorey and canopy at the dry site.

This study describes the fruiting phenology of woody plants and their dispersal syndromes in caatinga (semi-arid region in the northeast of Brazil). The fruiting phenology of 42 species with different dispersal modes and life-forms was followed over a period of 1 y. Animal dispersal was the most commonly observed dispersal mode (36%),followed by anemochory (33%), ballistic dispersal (19%) and barochory (12%). Overall, a greater number of speciesfruited during the rainy season. Zoochorous species were the most representative in the rainy season, whereasanemochorous species predominated during the dry season. Five different life-forms were observed, and the occurrence of dispersal modes was discussed for each of them. In the caatinga plant community studied the patterns of life-forms, fruiting phenology and seed dispersal syndromes were similar to other tropical seasonal ecosystems.

Este trabalho teve como objetivo principal descrever como se comportam asespécies de caatinga (região semi-árida do Nordestebrasileiro) com relação ao modo de dispersão durante asestações seca e chuvosa. Foram observados também osmodos de dispersão apresentados em cada forma de vida. A fenofase defrutificação foi acompanhada em 10 indivíduos de42 espécies durante um intervalo de um ano. A zoocoria representou omodo de dispersão mais observado (36%), seguido da anemocoria (33%),balística (19%) e barocoria (12%). Um maior número deespécies frutificou durante a estação de chuvas, sendoa zoocoria mais representativa nesta estação, enquanto que aanemocoria foi mais representativa na época de estiagem. Foramobservadas várias formas de vida, discutindo-se o modo de dispersãoem cada uma delas. Constatou-se que as espécies de caatinga estudadasencontram-se dentro dos padrões gerais de época de dispersãodos diásporos e representatividade das síndromes de dispersãoobservados em outros ecossistemas com sazonalidade.

The dry forests constitute one of the most distinct, yet least protected, ecosystems in Madagascar, an island renowned for high levels of endemism. They have generally been considered one of the most intact of Madagascar's climax vegetation types and accordingly have received little conservation effort. In particular, the Mikea Forest, a unique area between the Mangoky and Fiherenana rivers, currently receives negligible formal protection. It contains remarkably diverse plant and reptile assemblages, including several taxa that are found nowhere else, plus the only populations of two threatened bird species: the subdesert mesite Monias benschi and long-tailed ground-roller Uratelornis chimaera. From satellite imagery we estimate that primary forest cover declined by 15.6 per cent from 1962 to 1999, and that the rate of deforestation has increased from 0.35 per cent per annum in 1962–94 to 0.93 per cent per annum over the past 5 years. The most important factors underlying this process are slash-and-burn maize cultivation in the northern Mikea Forest and charcoal production at its southern fringe. Given these alarming circumstances, we suggest that combinations of conservation measures are required to safeguard the biological diversity of the area. Specifically, we recommend the establishment of a large protected area to the north of Manombo, a co-ordinated network of community-based conservation areas throughout the Mikea Forest, development projects to improve agriculture, and a regional research and education centre.

Frugivorous butterflies were studied in a set of forested islands (0.1 to 1.15 ha) in a reservoir in eastern Venezuela to investigate the effects of fragmentation and the resulting isolation on their abundance, diversity and species composition. While some islands showed reduced abundance and species diversity in comparison to unfragmented (or control) sites, others did not. Isolation status affected both butterfly abundance and diversity. Islands located close to their colonizing sources (0.1–1 km) tended to support similar densities of butterflies but lower numbers of species in comparison to control sites. Far fragments (1–3 km from their colonizing sources) tended to harbour lower butterfly densities in comparison to control sites but undiminished numbers of species. Species composition varied significantly between control sites and islands and amongst control sites, near islands and far islands. Interspecific differences were observed in species' responses to fragmentation. Charaxines, medium-sized satyrines, morphines and brassolines may be vulnerable to extinction after habitat fragmentation while small-sized satyrines may be relatively resistant. Observations during the dry season indicate that butterfly species may exist as mainland-island metapopulations in Lago Guri, in which small habitat fragments require recolonization every year from source populations in large islands and mainland habitat.

The dry and largely deciduous forests in Santa Rosa National Park in northwestern lowland Guanacaste Province, Costa Rica, Central America, have a moth fauna of about 2800 species. These moths pass the six month rain-free dry season, and some other portions of the year, by: (a) remaining dormant in the egg stage (1 species only), (b) remaining dormant in the pupal or prepupal stage (many species), (c) undergoing larval development (a few species of particular life forms) (d) remaining in the Park as a potentially active but non-reproductive adult (many species), and (e) migrating out of the Park after one to two generations and then returning at the beginning of the following rainy season (a few species of particular life forms). The migrating moths constitute a strong link between the dry forest and the rainforests to the east of the dry forest. The seasonal patterns of dormancy of immatures, reproductively dormant adults, and migration are not well correlated with the simple presence or absence of foliage on host plants, or with climate changes (except that the temperature drop that occurs at the beginning of the rainy season appears to be a widely used cue for pupal eclosion). The pattern of habitat use by leaf-eating caterpillars is probably determined more by the seasonal abundance of carnivores (parasitoids and predators) than by the mere presence of leaves; this process is very strongly evident in the failure of many moths to have more than one generation per year, even when their host plants are leafy throughout the six month rainy season or are even evergreen.