It has been increasingly recognized that the type of matrix surrounding habitat patches can affect biodiversity in landscapes, but there were only qualitative reviews of the subject focused on particular taxonomic groups. We present a quantitative review of studies from 1985 to 2008 that compared effects of different matrix types on individuals, populations and communities. We compiled 104 studies, most on animals, covering a broad range of landscape types and spatial scales. Most studies were empirical, focused on individuals and communities, and evaluated abundance/richness in the patch as the dependent variable. The type of matrix surrounding habitat patches influenced the studied parameters in 95% of the studies, but such effects were overall smaller compared to patch size or isolation effects. Matrix type effects were strongly species-specific, with different species responding differently to matrix type in 96% of studies comparing species or group of species. In 88% of studies, matrix types more similar in structure to the patch had higher quality for the studied organisms from the point of view of functional connectivity. Overall, the type of matrix is important, but patch size and isolation are the main determinants of ecological parameters in landscapes. Matrix quality generally increases with increasing structural similarity with habitat patches, a pattern that could be used as a general guideline for management of the matrix in fragmented landscapes.

Didelphids use vertical strata in different ways, suggesting the existence of a wider variety of niches than simply arboreal or terrestrial. This variety could be related to the differential ability to deal with support diameters and inclines, and might be important for the coexistence of species in local assemblages. From data obtained with the spool-and-line technique, the use of the vertical space and above-ground supports is described in four species of an assemblage of didelphid marsupials in south-east Brazil. The strati®cation in this and other assemblages in the Atlantic forest and in the Amazon is also compared. Animals were trapped in Serra dos O Â rga Äos, state of Rio de Janeiro, and equipped with a spool-and-line device before release. The paths were tracked by measuring variables related to support diameter, incline, distance and height moved above ground. The diameter of supports used was positively related to body size, and the incline to the dominant direction of movement (horizontal vs vertical). The more cursorial species, Metachirus nudicaudatus, only once moved above ground in > 3200 m of paths followed. Didelphis aurita moved mostly on the ground, but was the only species that occasionally reached the canopy. Philander frenata also moved mostly on the ground, occasionally used the understorey, but never reached the canopy. The more arboreal species, Marmosops incanus, moved mostly in the understorey, but never in the canopy. This pattern of strati®cation is similar to that observed in other sites in the Atlantic forest and in the Amazon.

Summary1. The relative importance of food supply and predation as determinants of animal population density is a topic of enduring debate among ecologists. To address it, many studies have tested the potential effects of food on population density by experimentally supplementing natural populations, with much focus on terrestrial vertebrates, especially small mammals. 2. Here we perform a meta-analysis of such experiments, testing two complementary hypotheses: (i) small mammal populations are bottom-up limited and (ii) population increases in response to food supplementation are constrained by predation, a top-down limitation. 3. In the 148 experiments recorded, food supplementation had an overall positive and significant effect, increasing population densities by 1Á5-fold. Larger population increases occurred when predation was reduced and populations were open to immigration. Predation appeared to be unimportant when populations were closed to immigration. Immigration was the major mechanism underlying increases in abundance by increasing local population density and crowding. Contributions of increased reproductive rate could be detected, but were minor compared to immigration, and no effects were detected from survival. 4. Our analyses support the view that animal population density is determined by both bottom-up and top-down forces. They also suggest the possibility that food supplementation experiments might unintentionally create ecological traps by aggregating both prey and predators in small areas of the landscape. We suggest an alternative experimental design to increase the contribution that food supplementation experiments can make in future.

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Species of didelphid marsupials (Didelphimorphia, Didelphidae) differ in their use of the forest strata, but it is not clear whether these differences are in fundamental or realized niches. The fundamental niche of seven species of didelphids (Caluromys philander, Didelphis aurita, Gracilinanus microtarsus, Marmosops incanus, Metachirus nudicaudatus, Micoureus demerarae, and Philander frenatus) was compared using their performance in arboreal walking. The association between performance and vertical use of the forest also was tested accounting for phylogenetic and allometric effects. Tests consisted of making the animal cross five 3 m long horizontal supports of different diameters, 1 m from the ground. The cycle of maximum speed was chosen to measure stride length, frequency and velocity. Arboreal species performed better than the terrestrial ones, but a major part of the variation in stride length (70.95%) and stride frequency (88.10%) was associated with body size. Part of the variation in stride length independent of body size (14.05%) was associated with the degree of vertical use of the forest, after phylogenetic effects were accounted for. Fundamental niches of six of the seven species were discriminated with the performance tests used. Discrepancies between the realized and fundamental niches can be inferred for two of these species, D. aurita and P. frenatus.

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Abstract:Perceptual range is used as a measure of the ability of animals to perceive the landscape, and can be used to infer functional connectivity between habitat patches such as forest remnants. A relationship of perceptual range with body mass was proposed by Mech and Zollner, but effects of life-history traits and environmental conditions were also acknowledged. We evaluated perceptual ranges and the influence of body mass, wind speed and direction, and grass height in four marsupial species of the Atlantic Forest of south-eastern Brazil. Release experiments were conducted and orientation towards the forest was determined using the spool-and-line technique. In 111 animals released, Didelphis aurita had the highest perceptual range (200 m), followed by Philander frenatus and Micoureus paraguayanus (100 m), and by Marmosops incanus (< 100 m). None of the species presented homing behaviour, and there was no difference in orientation abilities between sexes. Perceptual range was overestimated based on the equations of Mech and Zollner, but species were ordered in perceptual range according to their body size. Distance to the forest was a common determinant of the orientation in P. frenatus and M. paraguayanus, but grass height and wind direction were also important. Orientation of Didelphis aurita was determined by wind direction, showing anemotactic behaviour. Body mass is likely to affect perceptual ranges in didelphid marsupials, but only in interspecific comparisons. Within a species perception depends on the environmental context. Variables other than distance must be considered to estimate functional connectivity of the landscape based on perceptual range.

Summary1. For animal species inhabiting heterogeneous landscapes, the tortuosity of the dispersal path is a key determinant of the success in locating habitat patches. Path tortuosity within and beyond perceptual range must differ, and may be differently affected by intrinsic attributes of individuals and extrinsic environmental factors. Understanding how these factors interact to determine path tortuosity allows more accurate inference of successful movements between habitat patches. 2. We experimentally determined the effects of intrinsic (body mass and species identity) and extrinsic factors (distance to nearest forest fragment and matrix type) on the tortuosity of movements of three forest-dwelling didelphid marsupials, in a fragmented landscape of the Atlantic Forest, Brazil. 3. A total of 202 individuals were captured in forest fragments and released in three unsuitable matrix types (mowed pasture, abandoned pasture and manioc plantation), carrying spool-and-line devices. 4. Twenty-four models were formulated representing a priori hypotheses of major determinants of path tortuosity, grouped in three scenarios (only intrinsic factors, only extrinsic factors and models with combinations of both), and compared using a model selection approach. Models were tested separately for individuals released within the perceptual range of the species, and for individuals released beyond the perceptual range. 5. Matrix type strongly affected path tortuosity, with more obstructed matrix types hampering displacement of animals. Body mass was more important than species identity to determine path tortuosity, with larger animals moving more linearly. Increased distance to the fragment resulted in more tortuous paths, but actually reflects a threshold in perceptual range: linear paths within perceptual range, tortuous paths beyond. 6. The variables tested explained successfully path tortuosity, but only for animals released within the perceptual range. Other factors, such as wind intensity and direction of plantation rows, may be more important for individuals beyond their perceptual range. 7. Simplistic scenarios considering only intrinsic or extrinsic factors are inadequate to predict path tortuosity, and to infer dispersal success in heterogeneous landscapes. Perceptual range represents a fundamental threshold where the effects of matrix type, body mass and individual behaviour change drastically.