Edge effects as the principal cause of area effects on birds in fragmented secondary forest

Bird communities in tropical forests are strongly affected by both patch area and habitat edges. The fact that both effects are intrinsically confounded in space raises questions about how these two widely reported ecological patterns interact, and whether they are independent or simply different spatial manifestations of the same phenomenon. Moreover, do small patches of secondary forest, in landscapes where the most sensitive species have gone locally extinct, exhibit similar patterns to those previously observed in fragmented and continuous primary forests? We addressed these questions by testing edge-related differences in vegetation structure and bird community composition at 31 sites in fragmented and continuous landscapes in the imperilled Atlantic forest of Brazil. Over a two-year period, birds were captured with mist nets to a standardized effort of 680 net-hours at each site (similar to 22 000 net-hours resulting in 3381 captures from 114 species). We found that the bird community in patches of secondary forest was degraded in species composition compared to primary continuous forest, but still exhibited a strong response to edge effects. In fragmented secondary forests, edge and area effects also interacted, such that the magnitude of edge to interior differences on bird community composition declined markedly with patch size. The change in bird species composition between forest interiors and edges was similar to the change in community composition between large and small patches (because species had congruent responses to edge and area), but after controlling for edge effects community composition was no longer affected by patch area. Our results show that although secondary forests hold an impoverished bird community, ecological patterns such as area and edge effects are similar to those reported for primary forests. Our data provide further evidence that edge effects are the main drivers of area effects in fragmented landscapes.

Microhabitat Selection of three Forest Understory Birds in the Brazilian Atlantic Rainforest

When assessing fragmentation effects on species, not only habitat preferences on the landscape scale, but also microhabitat selection is an important factor to consider, as microhabitat is also affected by habitat disturbance, but nevertheless essential for species for foraging, nesting and sheltering. In the Atlantic Rainforest of Brazil we examined microhabitat selection of six Pyriglena leucoptera (white-shouldered fire-eye), 10 Sclerurus scansor (rufous-breasted leaftosser), and 30 Chiroxiphia caudata (blue manakin). We radio-tracked the individuals between May 2004 and February 2005 to gain home ranges based on individual fixed kernels. Vegetation structures in core plots and fringe plots were compared. In C. caudata, we additionally assessed the influence of behavioural traits on microhabitat selection. Further, we compared microhabitat structures in the fragmented forest with those in the contiguous, and contrasted the results with the birds` preferences. Pyriglena leucoptera preferred liana tangles that were more common in the fragmented forest, whereas S. scansor preferred woody debris, open forest floor (up to 0.5 m), and a thin closed leaf litter cover which all occurred significantly more often in the contiguous forest. Significant differences were detected in C. caudata for vegetation densities in the different strata; the distance of core plots to the nearest lek site was significantly influenced by sex and age. However, core sites of C. caudata in fragmented and contiguous forests showed no significant differences in structure. Exploring microhabitat selection and behavior may greatly support the understanding of habitat selection of species and their susceptibility to fragmentation on the landscape scale.

Is bird incidence in Atlantic forest fragments influenced by landscape patterns at multiple scales?

The degree to which habitat fragmentation affects bird incidence is species specific and may depend on varying spatial scales. Selecting the correct scale of measurement is essential to appropriately assess the effects of habitat fragmentation on bird occurrence. Our objective was to determine which spatial scale of landscape measurement best describes the incidence of three bird species (Pyriglena leucoptera, Xiphorhynchus fuscus and Chiroxiphia caudata) in the fragmented Brazilian Atlantic forest and test if multi-scalar models perform better than single-scalar ones. Bird incidence was assessed in 80 forest fragments. The surrounding landscape structure was described with four indices measured at four spatial scales (400-, 600-, 800- and 1,000-m buffers around the sample points). The explanatory power of each scale in predicting bird incidence was assessed using logistic regression, bootstrapped with 1,000 repetitions. The best results varied between species (1,000-m radius for P. leucoptera; 800-m for X. fuscus and 600-m for C. caudata), probably due to their distinct feeding habits and foraging strategies. Multi-scale models always resulted in better predictions than single-scale models, suggesting that different aspects of the landscape structure are related to different ecological processes influencing bird incidence. In particular, our results suggest that local extinction and (re)colonisation processes might simultaneously act at different scales. Thus, single-scale models may not be good enough to properly describe complex pattern-process relationships. Selecting variables at multiple ecologically relevant scales is a reasonable procedure to optimise the accuracy of species incidence models.

Are corridors, fragment size and forest structure important for the conservation of leaf-litter lizards in a fragmented landscape?

To investigate the implications of forest fragmentation for conservation of leaf-litter lizards the importance of fragment size, corridors and forest structure was examined in 20 forest fragments and six localities within a continuous forest in the Atlantic Plateau of Sao Paulo state, Brazil. The fragments were 2-276 ha in area and had different degrees of connectivity depending on the presence or absence of corridors. Two species of lizards were dominant, Ecpleopus gaudichaudii and Enyalius perditus. Variation in forest structure among sites was important only in explaining the abundance of E. perditus. Regardless of variation in forest structure, lizard species composition, total lizard abundance, number of species and abundance of E. perditus were sensitive to fragmentation per se but not to fragment size or corridor linkage. The inhospitable matrix surrounding fragments is probably what determines the presence and abundance of E. perditus and the high er lizard richness in continuous forests. These conditions may have prevented lizard species from recolonizing the forest fragments. Our results emphasize that the conservation of this leaf-litter fauna depends on the maintenance of large tracts of continuous forests and not on the size of fragments or on the presence of forest connections. Strategies for conservation of leaf-litter lizards in such highly fragmented Atlantic Forest landscapes should consider the enlargement of landscape connectivity between fragments and continuous forest, allowing the latter areas to act as a source of individuals for fragments.

Relative effects of fragment size and connectivity on bird community in the Atlantic Rain Forest: Implications for conservation

It is known that large fragment sizes and high connectivity levels are key components for maintaining species in fragments; however, their relative effects are poorly understood, especially in tropical areas. In order to test these effects, we built models for explaining understory birds occurrence in a fragmented Atlantic Rain Forest landscape with intermediate habitat cover (3%). Data from over 9000 mist-net hours from 17 fragments differing in size (2-175 ha) and connectivity (considering corridor linkages and distance to nearby fragments) were ranked under a model selection approach. A total 1293 individuals of 62 species were recorded. Species richness, abundance and compositional variation were mainly affected by connectivity indices that consider the capacity of species to use corridors and/or to cross short distances up to 30 m through the matrix. Bird functional groups were differently affected by area and connectivity: while terrestrial insectivores, omnivores and frugivores were affected by both area and connectivity, the other groups (understory insectivores, nectarivores, and others) were affected only by connectivity. In the studied landscape, well connected fragments can sustain an elevated number of species and individuals. Connectivity gives the opportunity for individuals to use multiple fragments, reducing the influence of fragment size. While preserving large fragments is a conservation target worldwide and should continue to be, our results indicated that connectivity between fragments can enhance the area functionally connected and is beneficial to all functional groups and therefore should be a conservation priority. (C) 2008 Elsevier Ltd. All rights reserved.

Importance of estimating matrix quality for modeling species distribution in complex tropical landscapes: a test with Atlantic forest small mammals

Information to guide decision making is especially urgent in human dominated landscapes in the tropics, where urban and agricultural frontiers are still expanding in an unplanned manner. Nevertheless, most studies that have investigated the influence of landscape structure on species distribution have not considered the heterogeneity of altered habitats of the matrix, which is usually high in human dominated landscapes. Using the distribution of small mammals in forest remnants and in the four main altered habitats in an Atlantic forest landscape, we investigated 1) how explanatory power of models describing species distribution in forest remnants varies between landscape structure variables that do or do not incorporate matrix quality and 2) the importance of spatial scale for analyzing the influence of landscape structure. We used standardized sampling in remnants and altered habitats to generate two indices of habitat quality, corresponding to the abundance and to the occurrence of small mammals. For each remnant, we calculated habitat quantity and connectivity in different spatial scales, considering or not the quality of surrounding habitats. The incorporation of matrix quality increased model explanatory power across all spatial scales for half the species that occurred in the matrix, but only when taking into account the distance between habitat patches (connectivity). These connectivity models were also less affected by spatial scale than habitat quantity models. The few consistent responses to the variation in spatial scales indicate that despite their small size, small mammals perceive landscape features at large spatial scales. Matrix quality index corresponding to species occurrence presented a better or similar performance compared to that of species abundance. Results indicate the importance of the matrix for the dynamics of fragmented landscapes and suggest that relatively simple indices can improve our understanding of species distribution, and could be applied in modeling, monitoring and managing complex tropical landscapes.

Movements of neotropical understory passerines affected by anthropogenic forest edges in the Brazilian Atlantic rainforest

Edge effects are suggested to have great impact on the persistence of species in fragmented landscapes. We tested edge avoidance by forest understory passerines in the Brazilian Atlantic Rainforest and also compared their mobility and movement patterns in contiguous and fragmented landscapes to assess whether movements would increase in the fragmented landscape. Between 2003 and 2005, 96 Chiroxiphia caudata, 38 Pyriglena leucoptera and 27 Sclerurus scansor were radio-tracked. The most strictly forest species C. caudata and S scansor avoided forest edges while P leucoptera showed affinities for the edge Both sensitive species showed larger mean step length and maximal observed daily distance in the fragmented forest versus the unfragmented forest. P. leucoptera did not show any significant difference. There were no significant differences in proportional daily home range use for any of the three species. Our results suggested that fragmentation and the consequent increase in edge areas do influence movement behavior of sensitive forest understory birds that avoided the use of edges and increased the speed and distance they covered daily. For the most restricted forest species, it would be advisable to protect larger patches of forest instead of many small or medium fragments connected by narrow corridors. However, by comparing our data with that obtained earlier, we concluded that movement behavior of resident birds differs from that of dispersing birds and might not allow to infer functional connectivity or landscape-scale sensitivity to fragmentation; a fact that should be taken into consideration when suggesting conservation strategies. (c) 2008 Elsevier Ltd. All rights reserved.

Isolation and characterization of microsatellite loci in the Brazilian orchid Epidendrum fulgens

Epidendrum fulgens has a patchy distribution along the Atlantic Rainforest in the Brazilian coast, due to the destruction of its native habitat. Here, we report on both the development of nine new microsatellite markers isolated from this species and the characterization of their allele variability in two distant and unrelated populations. The number of alleles observed for each locus ranged from 2 to 17 with an average of 6.4 alleles per locus. These microsatellites should be valuable tools for studying the effect of habitat fragmentation on the genetic structure of E. fulgens populations.

Time-lag in biological responses to landscape changes in a highly dynamic Atlantic forest region

Time-lagged responses of biological variables to landscape modifications are widely recognized, but rarely considered in ecological studies. In order to test for the existence of time-lags in the response of trees, small mammals, birds and frogs to changes in fragment area and connectivity, we studied a fragmented and highly dynamic landscape in the Atlantic forest region. We also investigated the biological correlates associated with differential responses among taxonomic groups. Species richness and abundance for four taxonomic groups were measured in 21 secondary forest fragments during the same period (2000-2002), following a standardized protocol. Data analyses were based on power regressions and model selection procedures. The model inputs included present (2000) and past (1962, 1981) fragment areas and connectivity, as well as observed changes in these parameters. Although past landscape structure was particularly relevant for trees, all taxonomic groups (except small mammals) were affected by landscape dynamics, exhibiting a time-lagged response. Furthermore, fragment area was more important for species groups with lower dispersal capacity, while species with higher dispersal ability had stronger responses to connectivity measures. Although these secondary forest fragments still maintain a large fraction of their original biodiversity, the delay in biological response combined with high rates of deforestation and fast forest regeneration imply in a reduction in the average age of the forest. This also indicates that future species losses are likely, especially those that are more strictly-forest dwellers. Conservation actions should be implemented to reduce species extinction, to maintain old-growth forests and to favour the regeneration process. Our results demonstrate that landscape history can strongly affect the present distribution pattern of species in fragmented landscapes, and should be considered in conservation planning. (C) 2009 Elsevier Ltd. All rights reserved.

The challenge of maintaining Atlantic forest biodiversity: A multi-taxa conservation assessment of specialist and generalist species in an agro-forestry mosaic in southern Bahia

Recent developments have highlighted the importance of forest amount at large spatial scales and of matrix quality for ecological processes in remnants. These developments, in turn, suggest the potential for reducing biodiversity loss through the maintenance of a high percentage of forest combined with sensitive management of anthropogenic areas. We conducted a multi-taxa survey to evaluate the potential for biodiversity maintenance in an Atlantic forest landscape that presented a favorable context from a theoretical perspective (high proportion of mature forest partly surrounded by structurally complex matrices). We sampled ferns, butterflies, frogs, lizards, bats, small mammals and birds in interiors and edges of large and small mature forest remnants and two matrices (second-growth forests and shade cacao plantations), as well as trees in interiors of small and large remnants. By considering richness, abundance and composition of forest specialists and generalists, we investigated the biodiversity value of matrix habitats (comparing them with interiors of large remnants for all groups except tree), and evaluated area (for all groups) and edge effects (for all groups except trees) in mature forest remnants. our results suggest that in landscapes comprising high amounts of mature forest and low contrasting matrices: (1) shade cacao plantations and second-growth forests harbor an appreciable number of forest specialists; (2) most forest specialist assemblages are not affected by area or edge effects, while most generalist assemblages proliferate at edges of small remnants. Nevertheless, differences in tree assemblages, especially among smaller trees, Suggest that observed patterns are unlikely to be stable over time. (C) 2009 Elsevier Ltd. All rights reserved.

Taxon surrogates among Amazonian mammals: Can total species richness be predicted by single orders?

Limited financial sources and the difficulty in performing complete surveys, allied to the speed of habitat fragmentation and the urgent necessity in select conservation areas, create the necessity of using some methodologies which bypass these problems. One possibility is the use of surrogate taxa that might be used as indicator of others groups richness and even total richness of an area. We investigated if the use of surrogate taxon is useful among seven mammal orders in Amazon. We tested through Pearson`s correlation (Bonferroni`s adjusted) if (1) there was a correlation between richness of total species and some order; (2) there was a significant pair wise correlation between species richness of each order; and (3) the combination of two orders would give better results as a surrogate for the total richness. The correlations found, in general, were positive. It means that the increase in the richness of an order was followed by its increase in another order, as well as in the total species richness. Only Didelphimorphia was significantly correlated with the total species richness. In the pair wise analyses only one assembly, Primates and Artiodactyla, was significantly correlated with total richness. Since indicator species are more effective within taxonomic groups (life-history characteristics are likely to be more different among than within major taxonomic groups), we suggest that an indicator group might be chosen for each one. In this case, for mammals from Amazon, it would be Didelphimorphia. (C) 2008 Elsevier Ltd. All rights reserved.

Carnivore mammals in a fragmented landscape in northeast of Sao Paulo State, Brazil

Sao Paulo is the most developed state in Brazil and little of its native vegetation remains. In Luiz Antonio and Santa Rita do Passa Quatro municipalities, only small fragments of cerrado (Brazilian savanna) physiognomies (cerrado, cerrado sensu stricto) and of semideciduous forest have been left, surrounded by eucalyptus silviculture and sugar-cane agriculture. However, that vegetation mosaic still shelters large mammals, including several carnivore species. To detect the carnivores present in such a mosaic area (50,000 ha), and to find out how they use the landscape, we recorded them through 21 camera traps and 21 track plots, during 18 months. Species richness, diversity and relative frequency were evaluated according to the habitat. Ten species were recorded, some of them locally threatened to extinction (Puma concolor, Leopardus pardalis, Chrysocyon brachyurus). Species diversity did not significantly differ among fragments, and although most species preferred one or another habitat, the carnivore community as a whole explored all the study area regardless of the vegetation cover;eucalyptus plantations were as used by the carnivores as the native fragments. Therefore, it seems possible to maintain such animals in agricultural landscapes, where some large native fragments are left and the matrix is permeable to native fauna.

Importance of interhabitat gaps and stepping-stones for lesser woodcreepers (Xiphorhynchus fuscus) in the Atlantic forest, Brazil

Translocation experiments showed that a woodcreeper bird species is able to move between isolated forest fragments, but this ability is limited by increasing interpatch distances. Larger distances (> 100 m) were overcome by using small stepping-stones (isolated trees), which enhance connectivity and are useful for the species conservation in fragmented landscapes.

Influence of multi-scale landscape structure on the occurrence of carnivorous mammals in a human-modified savanna, Brazil

So Paulo is the most developed state in Brazil and contains few fragments of native ecosystems, generally surrounded by intensive agriculture lands. Despite this, some areas still shelter large native animals. We aimed at understanding how medium and large carnivores use a mosaic landscape of forest/savanna and agroecosystems, and how the species respond to different landscape parameters (percentage of landcover and edge density), in a multi-scale perspective. The response variables were: species richness, carnivore frequency and frequency for the three most recorded species (Puma concolor, Chrysocyon brachyurus and Leopardus pardalis). We compared 11 competing models using Akaike`s information criterion (AIC) and assessed model support using weight of AIC. Concurrent models were combinations of landcover types (native vegetation, ""cerrado"" formations, ""cerrado"" and eucalypt plantation), landscape feature (percentage of landcover and edge density) and spatial scale. Herein, spatial scale refers to the radius around a sampling point defining a circular landscape. The scales analyzed were 250 (fine), 1,000 (medium) and 2,000 m (coarse). The shape of curves for response variables (linear, exponential and power) was also assessed. Our results indicate that species with high mobility, P. concolor and C. brachyurus, were best explained by edge density of the native vegetation at a coarse scale (2,000 m). The relationship between P. concolor and C. brachyurus frequency had a negative power-shaped response to explanatory variables. This general trend was also observed for species richness and carnivore frequency. Species richness and P. concolor frequency were also well explained by a second concurrent model: edge density of cerrado at the fine (250 m) scale. A different response was recorded for L. pardalis, as the frequency was best explained for the amount of cerrado at the fine (250 m) scale. The curve of response was linearly positive. The contrasting results (P. concolor and C. brachyurus vs L. pardalis) may be due to the much higher mobility of the two first species, in comparison with the third. Still, L. pardalis requires habitat with higher quality when compared with other two species. This study highlights the importance of considering multiple spatial scales when evaluating species responses to different habitats. An important and new finding was the prevalence of edge density over the habitat extension to explain overall carnivore distribution, a key information for planning and management of protected areas.