Small mammal assemblages in a disturbed tropical landscape at Pozuzo,Peru

Deforestation in the Peruvian pre-montane forests has increased alarmingly in recent years. Particularly, fragmentation in these forests takes place against a background of very extensive continuous forest. Until now, no studies have detailed how Peruvian small mammals responded to forest fragmentation. In this paper, we report the results of an assessment of nonvolant small mammal fauna in forest remnants (one large fragment and one small fragment) and cattle pasture in a disturbed landscape at Pozuzo, formerly a pre-montane tropical forest in central Peru. In each forest remnant, we quantify habitat parameters and identified small mammals to know if there is a relationship between forest remnant size or microhabitat structure and small mammal assemblages. In addition, we investigated the influence of habitat structure on the presence of small mammal species. We did not find any evidence that habitat structure in large fragment was greater than small fragment. Actually, both forest remnants presented habitat features typical of forests subject to higher levels of disturbance. We found that abundance of small trees (10 - 19 cm DBH) was positively associated with the presence of Marmosops noctivagus, but negatively with the presence of Oecomys bicolor. Likewise, the presence of the arboreal Rhipidomys leucodactylus was associated with the abundance of larger trees (DBH > 50 cm). We recorded 12 small mammal species in large fragment, 9 in small fragment and 3 in cattle pasture. No significant differences were found in species richness between both fragments, but marsupial abundance in the small fragment was greater than large fragment. At Pozuzo, we recorded 9 species restricted to forest habitat and 3 to forest and cattle pastures. However, it is necessary to assess more fragments to improve our knowledge about species survival in this landscape.     

Habitat patch and matrix effects on small-mammal persistence in Amazonian forest fragments

Tropical forest mammal assemblages are widely affected by the twin effects of habitat loss and habitat fragmentation. We evaluated the effects of forest patch metrics, habitat structure, age of patch isolation, and landscape metrics on the species richness, abundance and composition of small mammals at 23 forest fragments (ranging in size from 43 to 7,035 ha) in a highly deforested 3,609-km² landscape of southwestern Brazilian Amazonia. Using pitfall traps and both terrestrial and arboreal traplines of Sherman, Tomahawk and snap traps, we captured a total of 844 individuals over 34,900 trap-nights representing 26 species and 20 genera of small-mammals, including 13 rodent and 13 marsupial species. We also consider the effects of distance from forest edges on species occupancy and abundance. Overall small mammal abundance, species richness and species composition were primarily affected by the quality of the open-habitat matrix of cattle pastures, rather than by patch metrics such as fragment size. Ultimately, small mammal community structure was determined by a combination of both landscape- and patch-scale variables. Knowledge of the anthropogenic factors that govern small mammal community structure is of critical importance for managing the persistence of forest vertebrates in increasingly fragmented neotropical forest landscapes.     

Long-term persistence of midsized to large-bodied mammals in Amazonian landscapes under varying contexts of forest cover

Both forest fragmentation and overhunting have profound effects on the structure of large-vertebrate assemblages in neotropical forests. However, the long-term value of habitat fragments for forest mammals remains poorly understood and few regional scale studies have replicated sampling across spatially independent landscapes. Here, we assess the species occupancy and abundance of midsized to large-bodied mammals within three neighbouring Amazonian forest landscapes varying widely in extent of forest cover. One of these consisted of forest fragments surrounded by semi-natural scrub savannahs that had been occupied by paleoindian populations for at least 7,000 years, whereas forest cover in the other two landscapes was either variegated or continuous. Data on species occurrence and abundance from diurnal and nocturnal line-transect surveys and local interviews in each landscape were used to examine the effects of forest cover and hunting pressure on mammal persistence within forest patches. The extent of forest cover was a key determinant of species persistence across the three landscapes, but populations of large-bodied species were either reduced or driven to local extinction by hunting even in the most forested and least fragmented landscape. Many game and non-game species persisted in forest isolates, even though, individually, these were likely too small to support viable populations. This study indicates that even small, long-term forest fragments may retain significant conservation value if they can be managed within the context of enhanced connectivity across wider fragmented landscapes.     

The importance of considering both taxonomic and habitat guild approaches in small mammal research

Studies on the effects of habitat fragmentation on small mammals often lead to confounding results as they only consider taxonomic groups in their analysis and neglect functional diversity of the communities. Here we describe the structure and composition of small mammal communities at 22 sites, ranging from 41 to 7035 ha, in a hyper‐fragmented landscape of an Amazonia‐Cerrado ecotone. Also, in considering a taxonomic and habitat guild approach, we report the effects of habitat structures and patch spatial attributes on richness, abundance and species composition. Small mammal richness reported in southern Amazonia (N = 23 species) is greater than most previous studies in the tropics. All rare small mammals captured in this study were forest interior species. Richness of forest interior species was positively related to larger patches, as shown by the species–area relationship. However, 52% of the small mammal species were in forest fragments smaller than 50 ha, highlighting the importance of preserving both large and small forest fragments in a landscape with accelerated habitat reduction. Richness of edge‐tolerant species was not associated with the tested variables, yet edge‐tolerant species were more abundant in degraded environments. Marsupials were positively associated with vertical habitat structures, while rodents were more strongly related to a ground‐level habitat structure. The landscape studied is extremely variable and has contributed to the difficulty in detecting clear patterns, particularly when considering only one approach. Because of the complementary outputs when analysing either taxonomic groups or habitat guilds, we recommend the use of multi‐taxa studies of different guilds to assist decision makers in designing conservation strategies and appropriate management of small mammal populations.     

Tropical rain forest fragmentation,howler monkeys (Alouatta palliata), and dung beetles at Los Tuxtlas,Mexico

In Neotropical rain forests, fresh mammal dung, especially that of howler monkeys, constitutes an important resource used by dung beetles as food and for oviposition and further feeding by their larvae. Tropical rain forest destruction, fragmentation, and subsequent isolation causing reductions in numbers of and the disappearance of howler moneys may result in decreasing numbers of dung beetles, but this has not been documented. In this study, we present information on the presence of howlers and dung beetles in 38 isolated forest fragments and 15 agricultural habitats. Howler monkeys were censused by visual means, while dung beetles were sampled with traps baited with a mixture of howler, cow, horse, and dog dung. Results indicated that loss of area and isolation of forest fragments result in significant decrements in howlers and dung beetles. However, dung beetle abundance was found to be closely related to the presence of howler monkeys at the sites and habitats investigated. Scenarios of land management designed to reduce isolation among forest fragments may help sustain populations of howler monkeys and dung beetles, which may have positive consequences for rain forest regeneration. Am. J. Primatol. 48:253–262, 1999. © 1999 Wiley‐Liss, Inc.     

Fruit-feeding butterflies in edge-dominated habitats: community structure,species persistence and cascade effect

As old-growth forests are converted into edge-affected habitats, a substantial proportion of tropical biodiversity is potentially threatened. Here, we examine a comprehensive set of community-level attributes of fruit-feeding butterfly assemblages inhabiting edge-affected habitats in a fragmented Atlantic forest landscape devoted to sugar cane production. We also explored whether the consequences of habitat loss and fragmentation can interact and cause cascading ecosystem changes, with the pervasive simplification of tree assemblages inhabiting edge-dominated habitats, altering fruit-feeding butterfly persistence. Butterflies were sampled in three forest habitats: small fragments, forest edges and patches of forest interior of a primary forest fragment. Assemblage attributes, including taxonomic composition, correlated to some patch (patch size) and landscape (such as forest cover) metrics as well as habitat structure (tree density and richness). Fruit-feeding butterfly assemblages in the forest interior differed from those in small fragments due to an increased abundance of edge-specialist species. On the other hand, several forest-dependent species were missing in both small fragments and forest edges. Our results suggest that edge-affected habitats dominated by pioneer tree species support taxonomically distinct assemblages, including the presence of disturbance-adapted species, and butterfly community structure is highly sensitive to fragmentation- and plant-related variables, such as forest cover and pioneer tree species. In this way, while the establishment of human-modified landscapes probably results in the local extirpation of forest-dependent species, it allows the persistence of disturbance-adapted species. Thus, forest-dependent species conservation and the plant–animal interaction webs they support could be improved by retaining a significant amount of core forest habitat.     

Population of the black howler monkey (Alouatta pigra) in a fragmented landscape in Palenque,Chiapas, Mexico

Little is known about the population characteristics of Alouatta pigra under conditions of forest fragmentation-information that is important to understanding its tolerance to habitat loss. In this work we present data on forest loss and on troop size, age, and sex composition for a population of black howler monkeys existing in the fragmented landscape surrounding the Mayan site of Palenque, Chiapas, Mexico. Two aerial photos (1:70,000) of the study area (261 km(2)) taken in 1984 and 2001 were examined to assess forest loss. Between June and December 2001 and January and March 2002 we surveyed 44 forest fragments for the presence of howler monkeys. Examination of aerial photos showed that 33% of the forest present in 1984 had disappeared by 2001, and detected an increment in the number of forest fragments present in the landscape. We discovered a total of 115 howler monkeys living in 22 of the 44 forest fragments studied, of which 107 were members of 18 troops. The rest were solitary males or small groups of males living in isolated forest fragments. Troop size ranged from two to 15 individuals (mean 5.9+3.0 ind). 31% and 15% of individuals in the troops were juveniles and infants, respectively, suggesting continued reproductive activity. Howler monkey troops in the forest fragments were on average smaller (5.9+/-3.0 ind) than troops in the nearby protected forest of the Mayan site (7.0+/-2.8 ind). The mean density of howlers in the forest fragments was 119+/-82.9 ind/km(2). The establishment of corridors is suggested as a possible conservation scenario for the fragmented howler population investigated, and as a conservation measure to connect this population with the howler population found in the protected forest of the Mayan site.     

Contrasting effects of mosaic structure on alpha and beta diversity of bird assemblages in a human‐modified landscape

Habitat loss and fragmentation are key processes causing biodiversity loss in human‐modified landscapes. Knowledge of these processes has largely been derived from measuring biodiversity at the scale of ‘within‐habitat’ fragments with the surrounding landscape considered as matrix. Yet, the loss of variation in species assemblages ‘among’ habitat fragments (landscape‐scale) may be as important a driver of biodiversity loss as the loss of diversity ‘within’ habitat fragments (local‐scale). We tested the hypothesis that heterogeneity in vegetation cover is important for maintaining alpha and beta diversity in human‐modified landscapes. We surveyed bird assemblages in eighty 300‐m‐long transects nested within twenty 1‐km² vegetation ‘mosaics’, with mosaics assigned to four categories defined by the cover extent and configuration of native eucalypt forest and exotic pine plantation. We examined bird assemblages at two spatial scales: 1) within and among transects, and 2) within and among mosaics. Alpha diversity was the mean species diversity within‐transects or within‐mosaics and beta diversity quantified the effective number of compositionally distinct transects or mosaics. We found that within‐transect alpha diversity was highest in vegetation mosaics defined by continuous eucalypt forest, lowest in mosaics of continuous pine plantation, and at intermediate levels in mosaics containing eucalypt patches in a pine matrix. We found that eucalypt mosaics had lower beta diversity than other mosaic types when ignoring relative abundances, but had similar or higher beta diversity when weighting with species abundances. Mosaics containing both pine and eucalypt forest differed in their bird compositional variation among transects, despite sharing a similar suite of species. This configuration effect at the mosaic scale reflected differences in vegetation composition among transects. Maintaining heterogeneity in vegetation cover could help to maintain variation among bird assemblages across landscapes, thus partially offsetting local‐scale diversity losses due to fragmentation. Critical to this is the retention of remnant native vegetation.     

Defaunation and fragmentation erode small mammal diversity dimensions in tropical forests

Forest fragmentation and defaunation are considered the main drivers of biodiversity loss, yet the synergistic effects of landscape changes and biotic interactions on assemblage structure have been poorly investigated. Here, we use an extensive dataset of 283 assemblages and 105 species of small mammals to understand how defaunation of medium and large mammals and forest fragmentation change the community composition and diversity of rodents and marsupials in tropical forests of South America. We used structured equation models to investigate the relationship between small mammal species, functional and phylogenetic diversity with forest size, forest cover and the occurrence of medium and large mammals. The best‐fit model showed that defaunation reduced functional diversity, and that species diversity of small mammals increased with forest patch size. Forest cover did not affect functional and phylogenetic diversity. Our results indicate that occurrence of medium and large sized mammals (probably acting as predators, or competitors of small mammals) and forest patch size help to retain species and functional diversity in small mammal communities. Further, the number of species in a small mammal community was critical to the maintenance of phylogenetic diversity, and may have a pronounced influence on the ecological functions played by small mammals. Identifying how phylogenetic and functional diversity change in function of human pressures allows us to better understand the contribution of extant lineages to ecosystem functioning in tropical forests.     

Influence of the landscape matrix on the abundance of arboreal primates in fragmented landscapes

Composition of the landscape matrix of surrounding forest fragments is thought to be critically important to the survival of arboreal primates because it offers structures that help the animals move between fragments and other foraging sites. However, little is known about the composition of the matrix used by these animals. The aim of this study was to quantitatively assess the importance of the landscape matrix and its effects on primate abundance, using black howler monkeys (Alouatta pigra) living in a landscape fragmented by the expansion of agriculture and pastures for livestock in southeastern Mexico. In 2008, a complete census of the monkeys was carried out across the 2000-ha landscape matrix, and for every site where we observed monkeys, we recorded canopy height, tree basal area, food-source abundance, and distance to the nearest fragment. A total of 244 howler monkeys, distributed among 48 groups (including six solitary males) were counted in the matrix. Mean troop size was 5.6 ± 2.8 individuals, and the mode was three individuals. The highest number of troops and greatest howler monkey abundance were recorded in the isolated trees, the eucalyptus plantation, and orchards. A generalized linear model revealed that monkey abundance tended to be higher in matrix elements with higher canopy height, greater food availability, and closest to rainforest fragments. These results suggest that it is necessary to take into account the many elements of the landscape when drawing up conservation and habitat management plans, particularly in order to establish connectivity among the fragments and elements of the matrix with native trees.     

The Influence of Large Tree Density on Howler Monkey (Alouatta palliata mexicana) Presence in Very Small Rain Forest Fragments

The populations of the Mexican mantled howler monkey ( Alouatta palliata mexicana ) in the Los Tuxtlas region, Mexico, have declined drastically due to habitat loss and fragmentation. Nevertheless, several troops still inhabit very small and isolated rain forest fragments. We identified the main vegetation attributes that can favor the presence of howlers within 18 small (< 10-ha) fragments that did not differ significantly in size, shape, and isolation (nine occupied and nine unoccupied by howlers). We found that habitat quality ( i.e. , food resources and vegetation structure) affected howler incidence in small fragments. Particularly, the occupied fragments showed greater density of big trees (dbh > 60 cm), greater total basal area, greater basal area of persistent tree species, and greater basal area of top food species than the unoccupied fragments; suggesting that even for small fragments the loss of big trees and particularly the decrease in size class of the top food species can negatively affect howler distribution in highly fragmented landscapes. These findings could be used to establish foreground conservation areas for this critically endangered subspecies in fragmented landscapes of Los Tuxtlas.     

Differing responses to landscape change: implications for small mammal assemblages in forest fragments

Human modification of landscapes typically results in many species being confined to small, isolated and degraded habitat fragments. While fragment size and isolation underpin many studies of modified landscapes, vegetation characteristics are less frequently incorporated. The relative influence of biogeographic (e.g. size, isolation) and vegetation parameters on assemblages is poorly understood, but critical for conservation management. In this study, a multiple hypothesis testing framework was used to determine the relative importance of biogeographic and vegetation parameters in explaining the occurrence of an assemblage of small mammals in 48 forest fragments in an agricultural landscape in south-eastern Australia. Fragment size and vegetation characteristics were consistently important predictors of occurrence across species. In contrast, fragment isolation was important for just one native species. Differing abilities of species to move through the landscape provide a reasonable explanation for these results. We conclude that for effective conservation of assemblages, it is important to: (1) consider differing responses of species to landscape change, and (2) move beyond a focus primarily on spatial attributes (size, isolation) to recognise that landscape change also has profound effects on habitat composition and quality.     

Fragmentation and pre-existing species turnover determine land-snail assemblages of tropical rain forest

Aim The main aims of the study were: (1) to investigate the effect of fragment age in relation to other patch‐ and landscape‐scale measures of forest fragmentation, and (2) to assess the relative importance of fragmentation, habitat degradation (i.e. degradation caused by selective logging and past shifting cultivation) and putative pre‐existing species turnover in structuring current land‐snail assemblages. Location South‐western Sri Lanka. Methods The land‐snail fauna was sampled using standardized belt transects. Fifty‐seven transects were sampled in 21 lowland rain forest fragments (c. 1–33,000 ha). The spatial arrangement of fragments in the study area was explicitly considered in an effort to take into account the non‐random nature of fragmentation and degradation and the possibility that current species composition may reflect patterns of species turnover that existed prior to fragmentation. The data set of 57 land‐snail species and 28 environmental and spatial variables was analysed using canonical correspondence analysis and partial canonical correspondence analysis. Results Fragment age, mean shape complexity (i.e. a landscape‐scale measure of shape complexity), altitude, and the spatial variables x (longitude), y (latitude) and y² explained significant variation in land‐snail species composition. None of the three nominal variables quantifying habitat degradation was significantly correlated with variation in species composition. The independent effects of fragment age and mean shape complexity were similar. The combined effect of the spatial variables alone was larger than the independent effects of fragment age, mean shape complexity or altitude, but was of the same order of magnitude. The total variation explained by the spatial variables was comparable to the total non‐spatial variation accounted for by fragment age, mean shape complexity and altitude. Main conclusions Fragment age was found to be one of only two key determinants (the other was shape complexity at the landscape scale) driving fragmentation‐related changes in community composition. The influence of pre‐fragmentation patterns of species turnover on assemblage structure can be stronger than the effects of fragmentation measures, such as age, and may override the effects of forest degradation. Thus, strong patterns of pre‐existing turnover may potentially confound interpretation of the effects of forest fragmentation and degradation.     

Spatial and temporal changes in bird assemblages in forest fragments in an eastern Amazonian savannah

We investigated the effects of forest fragmentation on bird assemblages in an Amazonian savannah landscape with forest fragments that have been isolated for more than 100 years. The study was conducted in areas surrounding the village of Alter do Chão (2°31′S, 55°00′W), Santarém, Brazil. Bird surveys and measurements of tree density were undertaken in 25 areas, with 19 plots in forest fragments of different sizes and six in an area of continuous forest. Data on forest‐fragment size, perimeter, and isolation were obtained from a georeferenced satellite image. Variation in number of bird species recorded per plot was not related to vegetation structure (tree density). The number of bird species recorded per plot increased significantly only with fragment area, but was not influenced by fragment shape or degree of isolation, even when considering species from the savannah matrix in the analysis. Fragments had fewer rare species. Multivariate ordination analyses (multiple dimensional scaling, [MDS]) indicated that bird species composition changed along a gradient from small to large forest fragments and continuous‐forest areas. In the Amazonian savannah landscapes of Alter do Chão, the organization and composition of bird assemblages in forest fragments are affected by local long‐term forest‐fragmentation processes. Differences in the number of bird species recorded per plot and assemblage composition between forest fragments and continuous forest were not influenced by forest structure, suggesting that the observed patterns in species composition result from the effects of fragmentation per se rather than from preexisting differences in vegetation structure between sites. Nevertheless, despite their long history of isolation, the forest fragments still preserve a large proportion (on average 80%) of the avifauna found in continuous‐forest areas. The fragments at Alter do Chão are surrounded by natural (rather than planted) grassland, with many trees in the savannah matrix and the landscape has vast areas covered by forest, which may have helped to ameliorate the influences of forest fragmentation.     

Non-volant small mammal community responses to fragmentation of kerangas forests in Brunei Darussalam

This paper summarises the effects of kerangas forest fragmentation on the non-volant small mammal community resident in the fragments based on a long term study conducted in Brunei Darussalam. These effects are shown as eight responses—a significant reduction in the species richness and diversity in relation to size of fragments, the disappearance of species with large home ranges and specific habitat requirements, invasion of generalists/opportunists into the fragments from degraded habitats, absence of predators, a possible reduction in the activity space of generalists in fragments, erosion in the trophic structure of the small mammal community, changes in the small mammal abundance in relation to fragment size and dominance of one species over other co-occurring species in an isolated fragment. These responses are briefly explained and their significance discussed.     

Non flying mammals and landscape changes in the tropical rain forest region of Los Tuxtlas, Mexico

The rapid and extensive conversion of Neotropical rain forests to a landscape consisting of pasture lands and other agricultural habitats has meant the local disappearance fragmentation and isolation of vertebrate populations To avoid further losses in biodiversity in Neotropical rain forests, it is imperative to determine how the different species that constitute the different vertebrate communities have responded to the anthropogenic alterations of their natural habitats To provide data in this direction we sampled non flying mammals in 35 forest fragments, in six disturbed forest sites in 12 regenerating forests, in 20 arboreal agricultural habitats (cacao coffee, mixed, citrus and allspice), in four live fence sites and in four pasture sites at Los Tuxtlas, Veracruz Mexico Sampling indicated that area of forest fragments and isolating distance were important variables influencing species richness Disturbed forest had fewer species and individuals present and supported a lower non flying mammal biomass than undisturbed and regenerating forests Shaded plantations (cacao coffee and mixed) were richer in species and in individuals than unshaded ones (citrus, allspice) Species richness in forests and agricultural habitats were associated to horizontal plant diversity and vertical foliage diversity Pasture habitats were the poorest man-made habitats in non flying mammal species Live fences supported a higher biomass and species of non flying mammals than pastures and were similar to forest and shaded man-made habitats in species assemblages     

Patch- and landscape-scale effects on howler monkey distribution and abundance in rainforest fragments

Variation at both the patch and landscape scale is known to influence the distribution and abundance of arboreal monkeys in rainforest fragments. However, few studies have examined the factors associated with these different scales of focus simultaneously. Using stepwise logistic-regression and generalized linear models (GLMs), howler monkey Alouatta palliata distribution and abundance were examined as a function of patch quality (fragment area, shape, tree DBH and canopy height) and landscape connectivity (isolation, total forest area, fragment and road abundance, corridor abundance and length) in 119 rainforest fragments in northern Chiapas, Mexico. The positive correlation observed between monkey distribution (presence/absence) and both fragment area and abundance may be explained by increased resources within larger fragments and those whose proximity allows greater exploration by monkeys. In contrast, GLM analysis indicated that monkey abundance in inhabited fragments was positively correlated with corridor abundance, canopy height and fragment area. These relationships could be explained by greater reproductive investments by monkeys in forest fragments whose size, degree of perturbation and degree of connectivity with other fragments suggest greater overall resource availability. Future studies should explicitly include a multi-scale approach to understanding the factors affecting patterns of monkey distribution and abundance, particularly as this relates to measures of and interactions between patch connectivity and resource availability.     

Low functional richness and redundancy of a predator assemblage in native forest fragments of Chiloe island, Chile

1. Changes in land use and habitat fragmentation are major drivers of global change, and studying their effects on biodiversity constitutes a major research programme. However, biodiversity is a multifaceted concept, with a functional component linking species richness to ecosystem function. Currently, the interaction between functional and taxonomic components of biodiversity under realistic scenarios of habitat degradation is poorly understood. 2. The expected functional richness (FR)-species richness relationship (FRSR) is positive, and attenuated for functional redundancy in species-rich assemblages. Further, environmental filters are expected to flatten that association by sorting species with similar traits. Thus, analysing FRSR can inform about the response of biodiversity to environmental gradients and habitat fragmentation, and its expected functional consequences. 3. Top predators affect ecosystem functioning through prey consumption and are particularly vulnerable to changes in land use and habitat fragmentation, being good indicators of ecosystem health and suitable models for assessing the effects of habitat fragmentation on their FR. 4. Thus, this study analyses the functional redundancy of a vertebrate predator assemblage at temperate forest fragments in a rural landscape of Chiloe island (Chile), testing the existence of environmental filters by contrasting an empirically derived FRSR against those predicted from null models, and testing the association between biodiversity components and the structure of forest fragments. 5. Overall, contrasts against null models indicate that regional factors determine low levels of FR and redundancy for the vertebrate predator assemblage studied, while recorded linear FRSR indicates proportional responses of the two biodiversity components to the structure of forest fragments. Further, most species were positively associated with either fragment size or shape complexity, which are highly correlated. This, and the absence of ecological filters at the single-fragment scale, rendered taxonomically and functionally richer predator assemblages at large complex-shaped fragments. 6. These results predict strong effects of deforestation on both components of biodiversity, potentially affecting the functioning of remnants of native temperate forest ecosystems. Thus, the present study assesses general responses of functional and taxonomic components of biodiversity to a specific human-driven process.     

Gastrointestinal parasites of Howler monkeys (Alouatta palliata) inhabiting the fragmented landscape of the Santa Marta mountain range,Veracruz, Mexico

In recent years populations of howler monkeys (Alouatta palliata) in southeastern Mexico have decreased substantially due to the transformation and loss of natural habitats. This is especially evident in the Santa Marta mountain range, Veracruz, Mexico where several studies have evaluated the impact of fragmentation on howler monkey populations in order to propose management programs for their conservation. The conditions generated by fragmentation likely change the rates of parasitic infection and could decrease howler survival. In this study, gastrointestinal parasite species richness, prevalence, and egg density of infection were determined in howler groups inhabiting five forest fragments at the Santa Marta mountain range. Two hundred and seventy‐eight fresh fecal samples were collected between October 2002 and April 2003. Three parasite species were found during the dry and the wet season in all forest fragments sampled: one unidentified species of Eimeriidae; Trypanoxyuris minutus (Oxyuridae); and Controrchis biliophilus (Dicrocoeliidae). Both the prevalence of T. minutus and infection density for all parasites differed between seasons and fragments (the largest fragment consistently differed from other fragments). Host density, distance to the nearest town, fragment size, fragment shape, and total basal area of food trees explained parasite prevalence, but each species had a different pattern. Although parasite richness was lower, prevalence and density were higher than values reported for howlers in conserved forests. These results suggest that the establishment of biological corridors and animal translocation programs must take into account the parasite ecology of each fragment to avoid higher infection rates and preclude potential consequent mortality. Am. J. Primatol. 72:539–548, 2010. © 2010 Wiley‐Liss, Inc.     

Habitat fragmentation,EFN‐bearing trees and ant communities: Ecological cascades in Atlantic Forest of northeastern Brazil

Habitat fragmentation has a marked impact on the functional composition of tropical forest tree assemblages, and such change is likely to cascade through other trophic levels. Here, we investigate how habitat fragmentation affects extrafloral nectary (EFN)‐bearing plants and ant functional groups known to attend EFNs in a fragmented landscape of the Atlantic Forest. Extrafloral nectary‐bearing trees were identified in 50 0.1‐ha plots located in forest fragments, edge and interior patches. Ants were surveyed in 30 1‐m² litter samples in each of 17 forest fragments and in forest interior. Extrafloral nectary‐bearing plants accounted for 19.9% of individuals and 10.5% of species and included both pioneer and shade‐tolerant species similarly rich in the three habitat types. However, shade‐tolerant individuals accounted for >80% of EFN‐bearing plants in forest interior, compared with 2% in forest edge and 29% in fragments. Forest edge and fragment plots had a third fewer EFN‐bearing individuals and species compared with forest interior. This appeared to have important implications for local ant communities as the density of EFN‐bearing trees was the most important variable explaining the species richness of arboreal dominant ants. Our results show that plant loser–winner replacements promoted by forest fragmentation can cascade through higher trophic levels, with implications for forest dynamics and biodiversity conservation.