Adriana de Arruda Bueno

Beyond the Fragmentation Threshold Hypothesis: Regime Shifts in Biodiversity Across Fragmented Landscapes

Ecological systems are vulnerable to irreversible change when key system properties are pushed over thresholds, resulting in the loss of resilience and the precipitation of a regime shift. Perhaps the most important of such properties in human-modified landscapes is the total amount of remnant native vegetation. In a seminal study Andrén proposed the existence of a fragmentation threshold in the total amount of remnant vegetation, below which landscape-scale connectivity is eroded and local species richness and abundance become dependent on patch size. Despite the fact that species patch-area effects have been a mainstay of conservation science there has yet to be a robust empirical evaluation of this hypothesis. Here we present and test a new conceptual model describing the mechanisms and consequences of biodiversity change in fragmented landscapes, identifying the fragmentation threshold as a first step in a positive feedback mechanism that has the capacity to impair ecological resilience, and drive a regime shift in biodiversity. The model considers that local extinction risk is defined by patch size, and immigration rates by landscape vegetation cover, and that the recovery from local species losses depends upon the landscape species pool. Using a unique dataset on the distribution of non-volant small mammals across replicate landscapes in the Atlantic forest of Brazil, we found strong evidence for our model predictions - that patch-area effects are evident only at intermediate levels of total forest cover, where landscape diversity is still high and opportunities for enhancing biodiversity through local management are greatest. Furthermore, high levels of forest loss can push native biota through an extinction filter, and result in the abrupt, landscape-wide loss of forest-specialist taxa, ecological resilience and management effectiveness. The proposed model links hitherto distinct theoretical approaches within a single framework, providing a powerful tool for analysing the potential effectiveness of management interventions.

Using ecological thresholds to evaluate the costs and benefits of set-asides in a biodiversity hotspot

Cost-effective conservation on private land How affordable is biodiversity conservation in a fragmented landscape? Banks-Leite et al. asked this question for the biodiversity hotspot of the Brazilian Atlantic Forest. An annual investment of <10% of Brazils agricultural subsidies could support effective ecological restoration on private lands. This would increase biodiversity in set-aside land to the same level observed in protected areas. The cost-effectiveness of this scheme suggests a path forward for conservation strategies in other similarly mixed landscapes, too. Science, this issue p. 1041 A small portion of Brazil’s agricultural subsidies would be enough to preserve private land in the Brazilian Atlantic Forest. Ecological set-asides are a promising strategy for conserving biodiversity in human-modified landscapes; however, landowner participation is often precluded by financial constraints. We assessed the ecological benefits and economic costs of paying landowners to set aside private land for restoration. Benefits were calculated from data on nearly 25,000 captures of Brazilian Atlantic Forest vertebrates, and economic costs were estimated for several restoration scenarios and values of payment for ecosystem services. We show that an annual investment equivalent to 6.5% of what Brazil spends on agricultural subsidies would revert species composition and ecological functions across farmlands to levels found inside protected areas, thereby benefiting local people. Hence, efforts to secure the future of this and other biodiversity hotspots may be cost-effective.

Food habits of two syntopic canids, the maned wolf (Chrysocyon brachyurus) and the crab-eating fox (Cerdocyon thous), in southeastern Brazil

El aguara guazu (Chrysocyon brachyurus) y el zorro del monte (Cerdocyon thous) son dos canidos sudamericanos cuyas distribuciones geograficas se sobreponen extensamente. Sin embargo, hay pocos datos sobre la ecologia comparativa de estas especies. El objetivo de esta investigacion fue cuantificar la dieta de estos dos canidos en sintopia en cuanto a tres niveles: frecuencia de ocurrencia, numero minimo de individuos depredados y biomasa ingerida estimada. Ademas, se evaluaron la estacionalidad en el consumo de grupos de presas mayores y la distribucion de tamano de las presas consumidas. El estudio tuvo lugar en la Estacion Experimental de Itapetininga, en el Estado de Sao Paulo, Brasil. Los resultados mostraron que ambos canidos son omnivoros. El aguara guazu consumio partes vegetales y animales en proporciones similares, pero los zorros consumieron mas presas animales, principalmente insectos. En relacion a la biomasa de las presas, ambas especies consumieron presas animales. El aguara guazu consumio muchos frutos de Solanum lycocarpum y micromamiferos en la estacion seca, mientras que los frutos miscelaneos dominaron la dieta durante la estacion lluviosa. El zorro del monte tambien ingirio mas frutos miscelaneos en la estacion lluviosa, mientras que los insectos fueron principalmente consumidos en los meses secos. El zorro es mas generalista que el aguara guazu, pero en lo que se refiere a habilidades de captura, el aguara parece ser capaz de manipular mas tipos de presas y frutos diferentes. La distribucion de tamanos de las presas consumidas sugiere una separacion de nicho trofico entre ambas especies: mientras que el aguara guazu consumio un espectro mas amplio de tamanos de presas, especialmente los vertebrados pequenos entre 10,1 y 100,0 g, el zorro consumio presas mas pequenas, principalmente insectos entre 0,01 y 0,1 g

Immigration Rates in Fragmented Landscapes – Empirical Evidence for the Importance of Habitat Amount for Species Persistence

Background The total amount of native vegetation is an important property of fragmented landscapes and is known to exert a strong influence on population and metapopulation dynamics. As the relationship between habitat loss and local patch and gap characteristics is strongly non-linear, theoretical models predict that immigration rates should decrease dramatically at low levels of remaining native vegetation cover, leading to patch-area effects and the existence of species extinction thresholds across fragmented landscapes with different proportions of remaining native vegetation. Although empirical patterns of species distribution and richness give support to these models, direct measurements of immigration rates across fragmented landscapes are still lacking. Methodology/Principal Findings Using the Brazilian Atlantic forest marsupial Gray Slender Mouse Opossum (Marmosops incanus) as a model species and estimating demographic parameters of populations in patches situated in three landscapes differing in the total amount of remaining forest, we tested the hypotheses that patch-area effects on population density are apparent only at intermediate levels of forest cover, and that immigration rates into forest patches are defined primarily by landscape context surrounding patches. As expected, we observed a positive patch-area effect on M. incanus density only within the landscape with intermediate forest cover. Density was independent of patch size in the most forested landscape and the species was absent from the most deforested landscape. Specifically, the mean estimated numbers of immigrants into small patches were lower in the landscape with intermediate forest cover compared to the most forested landscape. Conclusions/Significance Our results reveal the crucial importance of the total amount of remaining native vegetation for species persistence in fragmented landscapes, and specifically as to the role of variable immigration rates in providing the underlying mechanism that drives both patch-area effects and species extinction thresholds.

Feeding ecology of the maned wolf, Chrysocyon brachyurus (Illiger, 1815) (Mammalia: Canidae), in the Ecological Station of Itirapina, São Paulo state, Brazil

The feeding ecology of the maned wolf (Chrysocyon brachyurus) was studied from 1998 to 2002 in the Ecological Station of Itirapina, Sao Paulo State, southeastern Brazil, including estimates of prey number and biomass consumption. A total of 325 faecal samples was collected in the area. The species is omnivorous, with a broad diet including 68 species or morphospecies of fruits and animals. Armadillos (Dasypodidae), wolfs fruit (Solanum lycocarpum) and small mammals (mostly Clyomys bishopi) were the bulk of the diet, comprising 72.8 % of the total estimated biomass consumed (185,323.4 g). In terms of frequency of occurrence, on the other hand, only small mammals and other miscella-neous fruits yielded 43.4 % of the total occurrences (N = 1,054). Animal prey ranging from 0.01 and 0.1 Kg were the most captured category, resulting in 44.2 % of 507 captured animals. The maned wolf seems to be seasonally opportunistic, at least for fruits and insects, as indicated by the variation of the consumption of these items along the year. The higher consumption of fruits and animals characteristic of savannah can be an important factor to consider in future management plans for the species.

Habitat specialization interacts with habitat amount to determine dispersal success of rodents in fragmented landscapes

Abstract Habitat specialization is considered one of the most important determinants of species vulnerability to habitat loss and fragmentation because it defines species dispersal ability and thus the degree of isolation of populations. Further, dispersal success of habitat-specialist species depends on the distance between fragments, which is conditioned on the total amount of habitat in the landscape. Here, we compared the influence of total habitat amount on dispersal success and abundance patterns of 2 habitat specialists and 1 generalist Atlantic Forest rodent. We investigated short-term population dynamics in a continuous forest landscape as well as in 6 small forest fragments located in 2 landscapes differing in the amount of forest cover (30% and 50%). Further, we analyzed the influence of fragment size on population density in the fragmented landscapes. Number of immigrants and abundance of both habitat-specialist species decreased remarkably in small patches of the 30% forest cover landscape compared to both more-forested landscapes, and both species showed a patch-area effect on density in this landscape. In contrast, the generalist species showed similar immigration rates in continuous forest and patches of the less-forested landscape, high temporal and spatial variability in abundance, and no patch-area effect in any of the landscapes. The results provide empirical support for the interaction between habitat specialization and habitat amount in determining the response of species to habitat loss, showing that the response of habitat specialists—in contrast to generalists—is governed by the landscape-wide amount of habitat. Resumo Especialização de habitat é considerada uma dos mais importantes determinantes da vulnerabilidade das espécies à perda de habitat e fragmentação uma vez que define a capacidade de dispersão e consequentemente o grau de isolamento das populações. Além disso, a dispersão bem-sucedida de espécies especialistas de habitat depende da distância entre fragmentos, a qual é condicionada pela quantidade total de habitat na paisagem. Neste estudo comparamos a influencia da quantidade total de habitat no sucesso de dispersão e padrões de abundância de 2 espécies especialistas de habitat e 1 generalista de roedores da Mata Atlântica. Nós investigamos a dinâmica populacional em um estudo de curta duração em uma paisagem florestal contínua assim como em 6 pequenos fragmentos florestais localizados em paisagens que diferiam quanto à quantidade de cobertura florestal (30% e 50%). Adicionalmente, nós analisamos a influência do tamanho do fragmento na densidade populacional em paisagens fragmentadas. O número de imigrantes e abundância de ambas as espécies especialistas de habitat diminuíram consideravelmente em pequenos fragmentos da paisagem com 30% de cobertura florestal comparados com ambas as paisagens com maior cobertura florestal e ambas as espécies apresentaram um efeito patch-area em suas densidades nesta paisagem. Ao contrário, a espécie generalista apresentou taxas de imigração similares em florestas e fragmentos da paisagem com menor cobertura florestal, alta variabilidade temporal e espacial na abundância e nenhum efeito patch-area em nenhuma das paisagens. Os resultados fornecem apoio empírico para a interação entre a especialização de habitat e a quantidade de habitat na determinação da resposta das espécies à perda de habitat, mostrando que a resposta dos especialistas de habitat—ao contrário dos generalistas—é regulada pela quantidade de habitat numa escala mais ampla da paisagem.

Small Mammal Prey Selection by Two Owl Species in Southeastern Brazil

Abstract A variety of factors influence prey selection by predators. Because Barn Owls (Tyto alba) and Burrowing Owls (Athene cunicularia) differ in size and foraging tactics, we expected differential predation on small mammal prey. We hypothesized that the Barn Owl, an active predator, would prey on smaller and younger individuals than the Burrowing Owl, a sit-and-wait predator. We used pellet analyses to evaluate selection of small mammals by the two owls in relation to prey species, age, and size at the Ecological Station of Itirapina, state of São Paulo, in southeastern Brazil. Small mammals constituted most of the prey individuals and biomass in the diet of Barn Owls. Although Burrowing Owls consumed a wider range of taxa, small mammals represented one-third of all biomass consumed. With respect to small mammals, Barn Owls foraged selectively relative to prey species, size, and age. Burrowing Owls foraged opportunistically relative to prey species, but selectively relative to prey size and age. Barn Owls selected smaller and younger (juvenile and subadult) individuals of the delicate vesper mouse (Calomys tener) and Burrowing Owls preyed more on larger and older (subadult only) individuals. Morphology and behavior of both prey and predators may explain this differential predation. Our data suggest that the active predator feeds on smaller and younger prey and the sit-and-wait predator took relatively larger and older prey.

Feeding habits of the maned wolf, Chrysocyon brachyurus (Carnivora: Canidae), in southeast Brazil

The feeding habits of the maned wolf were studied in southeast Brazil to understand its response towards changes in the environment and in relation to its prey. By occurrence, miscellaneous fruits, small mammals and wolfs fruit were the most consumed items. Armadillos, small mammals and wolfs fruit (Solanum lycocarpum) provided most of the ingested biomass. While wolfs fruit and small mammals were mainly consumed in the dry season, other miscellaneous fruits were taken mostly in the wet season. There was selectivity in the predation on some small mammal species. The maned wolfs diet followed patterns similar to those found in more pristine areas. O hábito alimentar do lobo guará foi estudado no sudeste do Brasil para descrever suas respostas as alterações do ambiente e em relação as suas presas. Por frequência de ocorrência, as frutas silvestres, os pequenos mamíferos e a fruta-do-lobo foram os itens mais consumidos. Tatus, pequenos mamíferos e a frutas-do-lobo (Solanum lycocarpum) constituíram os itens mais importantes em relação à biomassa ingerida. A fruta-do-lobo e os pequenos mamíferos foram consumidos principalmente na estação seca, enquanto os demais frutos silvestres na época das chuvas. Houve seleção de algumas espécies de pequenos mamíferos. A dieta do lobo guará apresentou padrões semelhantes aqueles encontrados em áreas mais preservadas.

Response to Comment on “Using ecological thresholds to evaluate the costs and benefits of set-asides in a biodiversity hotspot”

Finney claims that we did not include transaction costs while assessing the economic costs of a set-aside program in Brazil and that accounting for them could potentially render large payments for environmental services (PES) projects unfeasible. We agree with the need for a better understanding of transaction costs but provide evidence that they do not alter the feasibility of the set-aside scheme we proposed.

Vulnerability of small mammals to vertebrate predators in the ecological station of Itirapina, SP

Resumen pt: Estudos sobre selecao de presas podem apresentar resultados bastante diferentes dependendo do predador analisado. Predadores com diferentes tecnicas de c...Prey selection studies may result in different conclusions depending on the analysed forager. Predators with different foraging modes, such as raptors and carnivorous mammals, may select different prey types. Certain prey morphological and behavioural patterns could explain selection. Predation would be favouring morphological/functional adaptations, such as inflated auditory bullae, saltatorial locomotion, use of habitat with shelters and higher activity levels during moonless nights. This kind of study is still scarce in Brazil. So, the goal of this research was the analysis of small mammal selection in the diet of three predators at Itirapina Ecological Station, SP, as well as to verify the vulnerability of small mammals in relation to hearing, locomotion, use and activity in different physiognomies during nights with varying lunar illumination. Analysis of prey selection by the Barn Owl (Tyto alba) was conducted in relation to species, size, age and sex. The Burrowing Owl (Athene cunicularia) was studied in relation to the consumption of small mammal species, size and age. The Maned Wolf (Chrysocyon brachyurus) was only evaluated concerning prey species selection. Remains of bones (mandibles and pelvic girdles) found in pellets and faeces of predators were utilized to identify prey species, sex and to quantify number of consumed individuals. Analysis of prey species selection was conducted by comparisons between proportion of prey found in the diet and in environment, applying G test and Bonferroni confidence intervals. Differential sex consumption was evaluated by G test and Fisher exact test. Mann-Whitney test was employed to compare prey size in the diet and in the environment. Rodent ages found in pellets/ faeces and in the field were compared by G test. The volumes of auditory bullae were obtained by injection of water in these structures using micro-syringe. Bipedalism index (ratio between fore and hind limb lengths) was calculated to find the best potential escape response among the studied rodents. Small mammal abundance/activity in three different physiognomies was assessed by pitfall traps during full or no moon nights. The Barn Owl was more selective than the Burrowing Owl in relation to prey species consumption, though both of them include the same small mammal species in their diets. Calomys tener and Oligoryzomys nigripes were the most preyed on rodents by the two owls. Small-sized and juvenile individuals of C. tener were more consumed by the Barn Owl, whereas sub-adults were more preyed on by the Burrowing Owl. Differences may be due to foraging mode of each owl and biological characteristics of prey. Selection of smaller individuals within species may suggest predation of more vulnerable prey. So small-sized rodent selection may not result from active predation by the owls, but from higher vulnerability of these prey. Oligoryzomys nigripes was never selected positively by any of the three predators and the Barn Owl consumed mainly juveniles in the dry season. These set of information may suggest that O. nigripes is a less vulnerable prey to the owls and to the maned wolf in comparison to the other rodents. Its saltatorial locomotion may explain these results. The poor hearing ability and lack of response to varying lunar illumination levels suggest a later escape response opposed to detection of predator in advance. Calomys tener seems to be a high vulnerable prey in Itirapina. Although it decreases activity/abundance level during full moon nights, it is the most consumed rodent by the two owls. Both hearing and locomotion are poor in relation to the other rodents. The three predators positively selected Bolomys lasiurus. However, its abundance was very low in the Ecological Station and further investigation on its abundance should be assessed before conclusions. The consumption of larger prey, such as Clyomys bishopi, by the larger predator, the Maned Wolf, was expected. Data revealed that Clyomys bishopi owns the best hearing capability, but the worst escape response, according to the bipedalism index. Although it has large auditory bullae, which could be related to communication among co specifics, it is the most consumed prey by the maned wolf. The low consumption of this Echymyidae by the Barn and Burrowing owls may be related to its great body mass and consequently difficulties in prey handling. Based on this study, depending on locality and differences in prey composition/abundance, predators may adopt different strategies. In the same area, resource was utilized in different manner by these predators, at least, in terms of prey proportion in the diet, size and age. Further studies using the same methodology, involving all components of trophic guilds, besides environmental variables, may better illustrate the role of each species in community. The so-called efficient escape strategies were the ones found among rodents in deserts. It may be the case in http://www.biotaneotropica.org.br that these morphological and behavioural characteristics may not confer less vulnerability in savannah-like environments. Besides, the lack of information about predator and prey sensory capabilities makes it difficult to interpret and test hypotheses. All these questions should be taken into account in further studies about prey selection and vulnerability. Key-words: small mammals; predation; vulnerability; savannah FICHA CATALOGRÁFICA: Bueno, Adriana de Arruda Vulnerabilidade de pequenos mamíferos de áreas abertas a vertebrados predadores na Estação Ecológica de Itirapina, SP. 99 páginas Dissertação (Mestrado) – Instituto de Biociências da Universidade de São Paulo. Departamento de Ecologia. 1. pequenos mamíferos; 2. predação; 3. vulnerabilidade; 4. cerrado. Universidade de São Paulo. Instituto de Biociências. Departamento de