Context
Theoretical models propose that the spatial extent at which landscape structure best predicts species responses (scale of effect, SoE) depends on habitat and dietary specialization, landscape ...metrics, and response variables. However, empirical support for such models is scarce, especially for apex predators.
Objectives
To determine SoE for diurnal raptors, and test for differences among ecological traits of habitat and dietary specialization, landscape metrics, and response variables.
Methods
We conducted 1.5 km transect surveys of diurnal raptors at 26 sites in a tropical dry forest from western Mexico. We measured four landscape metrics (forest cover, matrix hardness, forest patch density, edge density) in 16 concentric landscapes (400 to 3400 ha) around each survey site. We then assessed the landscape size at which each landscape metric best predicted each response variable (abundance, species richness, temporal beta diversity). Finally, we tested for differences in SoE among ecological traits of raptors, landscape metrics, and response variables.
Results
Landscape composition metrics of forest cover and matrix hardness decreased with increasing landscape size, and were the main landscape predictors influencing diurnal raptors. SoE differed significantly among landscape metrics, being larger for forest cover (2433.3 ha) than matrix hardness (1500 ha). However, SoE did not differ significantly among ecological traits of raptors, or response variables.
Conclusions
SoE was mainly driven by spatial metrics, with diurnal raptors being more strongly associated with forest cover measured over larger scales. This supports findings for other taxa and suggests that forest cover influences dispersal success across larger scales.
Context
Forest loss and fragmentation are rapidly expanding across the tropics. Although forest loss is a major driver of the current biodiversity crisis, the effect of fragmentation remains debated, ...particularly for forest-specialist species.
Objectives
We evaluated the univariate and combined effect of forest loss (percent of forest cover) and fragmentation (forest patch density) on populations of a forest-specialist primate, the black-fronted titi monkey (
Callicebus nigrifrons
), in the landscapes from a transitional zone between Atlantic Forest and Cerrado biomes.
Methods
We surveyed titi monkey density in 14 landscapes. Using a multiscale and multimodel inference approach, we tested the relative effect of each landscape variable assessed at their respective scales of effect on titi monkey density.
Results
Titi monkey density ranged from 0 to 12 groups/km
2
and was best predicted by the combined effect of forest cover and patch density. Density increased in forest patches embedded in more deforested and fragmented landscapes. Interestingly, the effect of forest patch density was consistently positive along the entire evaluated forest cover gradient (9–42%).
Conclusions
Our findings support that fragmentation per se can have positive effects on biodiversity, in this case, by increasing the likelihood that more individuals can be ‘rescued’ from deforestation and crowded in the remaining forest patches. Although the long-term consequences of living crowded in forest patches are unknown, a conservative approach for preserving this (and potentially other) forest-specialist species could be to promote forest restoration projects focused on increasing the number and/or size of forest patches in the landscape (i.e., reverse fragmentation).
Worldwide deforestation and degradation are limiting the capacity of tropical dry forests (TDFs) to provide environmental services. Agroforestry systems (AFSs) are agricultural land systems that ...combining perennial elements with crops, can provide important benefits to people (e.g. timber and non-timber products) and the environment (e.g. hosting biodiversity). Using a semi-quantitative methodology (i.e. weight of evidence), we assessed the role of the three main types of AFSs (intercropping, multistrata and silvopastoral and protective systems) in restoring key ecosystem services in TDFs. We found that each type of AFSs contributed differently to soil quality restoration, productivity, biodiversity, carbon sequestration, and culture preservation. Yet, AFSs can also deliver few disservices, such as yield reductions. Despite the identified knowledge gaps, such as the carbon sequestration capacity, our findings indicate that AFSs can contribute to restore TDFs by providing valuable ecosystem services to halt degradation and sustain people’s livelihood.
Human-modified landscapes are composed of different types of land covers in differing proportions (landscape composition), and each with differing spatial physiognomy (landscape configuration). ...Unfortunately, the information on the relative impact of these two components of landscape structure on biological assemblages is scarce, but urgently needed to improve conservation strategies. We assessed the relative influence of the composition (landscape forest cover and matrix composition) and configuration (degree of forest fragmentation and forest edge density) of 100-ha and 500-ha landscapes on the abundance, diversity, and evenness of phyllostomid bat assemblages in the Lacandona rainforest, Mexico. We assessed the complete bat assemblage and frugivorous bats separately, and we grouped frugivores into understory foragers and canopy foragers. Landscape forest cover was the main predictor of the complete bat assemblage, positively affecting species diversity, particularly the number of rare species. Thus, community evenness decreased in landscapes with higher forest cover. Although weaker, species diversity was positively related to fragmentation and negatively associated with edge density. Landscape composition also was relatively more important than configuration for frugivores. The number of common and dominant frugivorous species and the abundance of understory frugivores increased in landscapes with lower forest cover and dominated by secondary forests in the matrix. The abundance of canopy frugivores showed the opposite response. Thus, to preserve bat assemblages and their important functional roles, conservation initiatives should prioritize a reduction in deforestation and the increase of secondary forests in the matrix. Maintaining all remaining forest patches is needed to favor landscape complementation and supplementation dynamics.
•We test the relative impact of landscape composition and configuration on bats.•Forest spatial composition shows stronger impacts than forest spatial configuration.•Forest loss decreases species diversity, particularly the number of rare species.•Primary forest favors the whole assemblage and secondary forest favors frugivores.•Conservation initiatives should prioritize a reduction in deforestation.
The rapid loss and degradation of tropical forests threatens the maintenance of biodiversity across different spatial scales. Nevertheless, the extirpation and population decline of some ...disturbance-sensitive species may be compensated for by colonization and proliferation of disturbance-adapted species, thus allowing distributions of community-level attributes (e.g., abundance and diversity) to be preserved in human-modified tropical landscapes. To test this poorly assessed hypothesis we evaluated species- and community-level responses of amphibians and reptiles to differences in forest patch (patch size, shape, and distance to water bodies) and landscape metrics (old-growth forest cover, degree of fragmentation, and matrix composition) in the fragmented Lacandona rainforest, Mexico. We found that the abundance of several amphibian and reptile species was strongly associated with forest patch and landscape attributes, being particularly higher in larger patches surrounded by a greater forest cover. Such changes at the species level generated notable changes in reptile communities. In particular, the abundance, diversity, and evenness of reptile communities were strongly related to patch size, patch shape, and matrix composition. Yet, because of compensatory dynamics in amphibians, this group showed weak responses at the community level. Despite such compensatory dynamics, our results indicate that forest loss at the patch and landscape levels represents the main threat to both amphibians and reptiles, thus indicating that to preserve herpetological communities in this biodiversity hotspot, conservation initiatives should be focused on preventing further deforestation.
Context
The role of protected areas as biodiversity repositories has become increasingly important in face of increased deforestation. By adding free-living exotic mammals, removing forest-dependent ...native ones, isolating forest patches from large protected areas and reducing landscape forest cover, human activities may drive mammal communities towards regional biotic homogenization.
Objectives
We assessed how landscape forest cover and proximity to the largest and best-preserved area of the Catimbau National Park—one of the largest protected areas of the Brazilian Caatinga—affect α- and β-diversity of medium- and large-sized mammals, considering native and exotic species.
Methods
Using camera traps (total effort of 2340 cameras/day), we obtained 823 records of 15 species (8 natives and 7 exotics) in 18 landscapes of 1-km radius. We estimated diversity metrics within and among landscapes and used generalized linear models to assess the effect of forest loss and isolation on diversity metrics.
Results
As expected, forest loss decreased α-diversity of native species and increased the diversity and relative abundance of exotics. However, proximity to the preserved area showed weak effect on α-diversity, suggesting that this area does not work regionally as source for natives neither as ecological trap for exotics. Supporting the biotic homogenization hypothesis, β-diversity of natives decreased and β-diversity of exotics increased in more deforested landscapes. Yet, species composition was weakly related to forest cover and isolation.
Conclusions
Our findings demonstrate that deforestation jeopardizes native species, favors exotics, and drives mammal communities towards biotic homogenization. Protected areas should be properly implemented to safeguard mammal diversity.
Ecological traits of the world's primates Galán-Acedo, Carmen; Arroyo-Rodríguez, Víctor; Andresen, Ellen ...
Scientific data,
05/2019, Letnik:
6, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Ecosystems largely depend, for both their functioning and their ecological integrity, on the ecological traits of the species that inhabit them. Non-human primates have a wide geographic distribution ...and play vital roles in ecosystem structure, function, and resilience. However, there is no comprehensive and updated compilation of information on ecological traits of all the world's primate species to accurately assess such roles at a global scale. Here we present a database on some important ecological traits of the world's primates (504 species), including home range size, locomotion type, diel activity, trophic guild, body mass, habitat type, current conservation status, population trend, and geographic realm. We compiled this information through a careful review of 1,216 studies published between 1941 and 2018, resulting in a comprehensive, easily accessible and user-friendly database. This database has broad applicability in primatological studies, and can potentially be used to address many research questions at all spatial scales, from local to global.
Tropical forests are being exposed to increasing levels of habitat loss and fragmentation, threatening the maintenance of global biodiversity. However, the effect that land-use change may have on the ...spatial dissimilarities in taxonomic and functional composition of remaining assemblages (i.e., taxonomic/functional β-diversity) remains poorly understood. We examined a large vegetation database from an old and severely fragmented Atlantic forest landscape to test two alternative hypotheses: (1) tree assemblages experience a taxonomic and functional homogenization (reduced β-diversity) between forest fragments and along forest edges, or alternatively, (2) these edge-affected forests show increased taxonomic and functional differentiation (increased β-diversity) when compared to forest interior (reference) stands. Taxonomic and functional β-diversity were examined via novel abundance-based metrics and considering functional traits related to plant dispersion, recruitment, and growth. Overall, taxonomic β-diversity among fragments was significantly higher than among edge and reference plots. Edge plots also showed higher β-diversity than reference plots, but only when considering dominant species. In functional terms, β-diversity among reference plots was also lower than among forest fragments and among edge plots. These patterns support the landscape-divergence hypothesis, which postulates that variable human disturbances among forest fragments and along forest edges can lead to contrasting trajectories of vegetation changes, thus increasing the compositional and functional differentiation of tree communities in these emerging environments. Our results also show that such differentiation can preserve landscape-wide biodiversity, thus overriding negative effects of habitat fragmentation on local (α) diversity. Therefore, our findings demonstrate that forest fragments and forest edges can be more valuable for maintaining species diversity and ecosystem function in fragmented tropical landscapes than previously thought.
Forest fragmentation can lead to reductions in food availability, especially for some large-bodied tropical mammals such as spider monkeys. During a 15-mo period, we assessed the diet of Geoffroyi's ...spider monkey (Ateles geoffroyi) in continuous forest and fragments in the Lacandona region, southern Mexico, and related differences in diet to differences in vegetation structure and composition. We found that both forest types presented top food species for monkeys (e.g., Spondias spp., Brosimum alicastrum), but the sum of the importance value index of these species and the density of large trees were lower in fragments than in continuous forest. We also found that, compared with continuous forest, monkeys in fragments diversified their overall diet, increased consumption of leaves, and reduced the time they spent feeding on trees in favor of more time feeding on hemiepiphytes (particularly Ficus spp.) and palms, both of which were common in fragments. We attribute these changes to the relative food scarcity of the most favored feeding plants in forest fragments. Overall, our findings suggest that monkeys are able to adjust their diet to food availability in fragments, and thus persist in small- and medium-sized fragments. Although it is unlikely that the small size of two of the three study fragments (14 and 31 ha) can maintain viable populations of monkeys in the long term, they may function as stepping stones, facilitating inter-fragment movements and ultimately enhancing seed dispersal in fragmented landscapes.
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