Equivalent biodiversity area: A novel metric for No Net Loss success in Brazil's changing biomes.

This study presents a new method to incorporate the No Net Loss (NNL) principle within corporate Environmental, Social, and Governance (ESG) frameworks. This principle aims to ensure that biodiversity losses from human activities are fully offset. In this context, we tackle two main challenges: managing epistemic uncertainties in environmental modeling and accurately assessing compensatory areas needed to replace lost habitats. Focusing on Brazil's diverse biomes, which are undergoing rapid changes, we highlight the role of expert opinion surveys in addressing the uncertainties of the InVEST Habitat Quality, a model that simulates changes in landscape integrity under different land use scenarios. Our analysis across three of Brazil's regions - Caatinga Semi-arid, Cerrado Savanna, and Atlantic Forest - leverages open-source data to reveal substantial habitat losses due to activities like wind farm development, mining, and intensive agriculture, leading to a widespread decline in habitat quality. We introduce the Equivalent Biodiversity Area (EBA) metric to support NNL and Net Gain of Biodiversity efforts, measured in hectares. Findings show a reduction in EBA across all studied areas, highlighting the need for effective compensation strategies. Such strategies should merge Legal Reserves and ecological restoration into ESG policies, encourage landholder collaboration, and align with larger environmental efforts, such as watershed revitalization and Biodiversity Credits markets.

Population characteristics of Akodon montensis (Sigmodontinae) in response to habitat degradation and food availability.

Small mammal populations can be affected by habitat degradation, causing changes in their abundance, density and movement. Akodon montensis, a persistent host for Orthohantavirus, is a common rodent species in primary and secondary forest habitats and is considered a generalist species. This paper analyzes how habitat degradation and resource availability affect the population characteristics of the species. Six plots were classified into three levels of degradation, with sampling conducted in June and November 2015. After the June sampling, three plots were selected for the increase of food resources for three months, to assess how this factor affects the population. Abundance was estimated with the capture-mark-recapture method and density was estimated by dividing abundance by the effective sampling area. Home range was calculated using the Minimum Convex Polygon method, and the Maximum Distance Traveled as the longest average movement between two sampling stations where an individual was encountered. More degraded habitats supported lower average density and abundance of A. montensis compared to less degraded habitats. Increasing food availability led to increases in abundance in the more degraded habitats and decreases in the least degraded. Changes in home range were most evident, decreasing in the least degraded plots after the increase in resources. The sex ratio did not differ from equity in any plot, nor with respect to any of the factors studied. Population characteristics of the species are determined by several factors, including habitat quality and food distribution and abundance. If changes occur in these factors (either artificially or naturally) then movement, abundance and population density are affected in response to such changes. Although some results were not statistically significant, an apparent interaction was observed between habitat quality and resource availability, thereby influencing the abundance and density of A. montensis.

Las poblaciones de pequeños mamíferos pueden verse afectadas por las degradaciones en el hábitat, ocasionando cambios en la abundancia, densidad y movimiento de los mismos. Akodon montensis, un persistente hospedero para el Orthohantavirus, es una especie de roedor bastante común en hábitats de bosque primario y secundario, y es considerado como una especie generalista. Este trabajo analiza cómo la degradación del hábitat y la disponibilidad de recursos alimenticios, afectan las características poblacionales de la especie. Seis parcelas se clasificaron en tres niveles de degradación, realizándose muestreos en junio y noviembre del 2015. Luego del muestreo de junio, tres parcelas fueron seleccionadas como experimentales con el aumento de recursos durante tres meses, para evaluar cómo afecta este factor a la población, y las otras tres parcelas se mantuvieron como control sin el aumento de recursos. La abundancia se estimó con el método de captura-marca-recaptura y la densidad se estimó dividiendo la abundancia por el área efectiva de muestreo. Se calculó el área de acción mediante el método de Polígono Mínimo Convexo. Hábitats más degradados registraron un menor promedio de densidad y abundancia comparando con las degradaciones más bajas. Con el aumento de recursos, la disponibilidad de alimento generó aumentos en la abundancia de los hábitats más degradados mientras que disminuyeron en el menos degradado. Se observaron principalmente cambios en el área de acción, que disminuyeron en las parcelas menos degradadas luego del aumento de recursos. La proporción de sexos no presentó diferencias a la equidad en ninguna parcela, ni con respecto a alguno de los factores estudiados. Las características poblacionales de las especies están determinadas por factores como la calidad del hábitat, la distribución y abundancia de alimento. Cambios (artificiales o naturales) en estos factores, afectan el movimiento, la abundancia y densidad de las poblaciones. Aunque algunos resultados no fueron estadísticamente significativos, se observa cierta interacción entre la calidad del hábitat y disponibilidad de recursos, que influyen principalmente en la abundancia y densidad de A. montensis.

Effects of variation in forest fragment habitat on black howler monkey demography in the unprotected landscape around Palenque National Park, Mexico.

Habitat loss and fragmentation are leading threats to biodiversity today, and primates are particularly vulnerable to anthropogenic habitat disturbance. However, few studies have examined how differential effects of variation in forest fragment characteristics on males and females in a primate population may affect demography and population persistence. We quantified the effects of variation in forest fragment characteristics on the within-fragment demography of black howler monkeys (Alouatta pigra) in forest fragments around Palenque National Park, Mexico, and how these effects differed between adult males and females. We quantified forest loss in the landscape between 2000 and 2017, and used a redundancy analysis to examine the effects of 15 variables quantifying fragment dimensions, forest composition and physical structure, and isolation on fragment population size and density, the proportion of adult males and females in the fragment population, and the mean number of adult males and females per group in 34 fragments (N = 393 monkeys). We hypothesized that (i) population size is positively correlated with fragment area, while population density is negatively correlated, and (ii) the composition of fragment populations results from differential effects of fragment variables on adult males and females. Forest cover decreased by 23.3% from 2000 to 2017. Our results showed a significant effect of fragment variables on population demography in fragments, accounting for 0.69 of the variance in the demographic response variables. Population size increased with fragment area and connectivity, while density decreased. Larger, less isolated fragments with better connectivity, characteristics indicative of abundant secondary growth, and those with more diverse vegetation but lower Simpson's evenness indices tended to have more adult females per group and a higher proportion of adult females in the population. In contrast, fragments that were largely similar in characteristics of forest composition and structure, but that were more isolated from nearby fragments, had more adult males per group and a higher proportion of adult males. These results may stem from black howler females preferentially remaining in natal groups and fragments when possible, and dispersing shorter distances when they disperse, while males may be more likely to disperse between fragments, traveling longer distances through the matrix to more isolated fragments. These differential effects on males and females have important conservation implications: if females are more abundant in larger, less isolated fragments, while males are more abundant in more isolated fragments, then to effectively conserve this population, both landscape connectivity and fragment areas should be maintained and increased.

Sigmodontine community and species responses to El Niño and precipitation in different levels of forest degradation.

Few studies have focused on rodent communities at the margins of an ecoregion or the limits of species' distributions, where the community may be more sensitive to extrinsic variables, both biotic and abiotic. This study evaluates sigmodontine rodent species diversity and overall abundance, and variation associated with climatic variables, in three locations with differing levels of habitat degradation. The study was conducted in northeastern Paraguay, near the western limit of the Upper Paraná Atlantic Forest and near the distributional limits of the three most abundant species in the study sites. Three mark-recapture grids were established and classified as least, moderately and most-degraded based on an analysis of several vegetation parameters. The grids were sampled for five consecutive nights, six times during two years. Shannon diversity and overall abundance were calculated for each sample. Monthly Multivariate ENSO Index and rainfall values were obtained from publicly available resources. Product-moment correlations were calculated between community and climatic parameters, including cumulative values for the climatic variables. The same correlations were calculated for the three common sigmodontine species. 1,632 captures were recorded, representing 13 sigmodontine species. Species richness in the samples (one session on one grid) varied from four to seven. Akodon montensis, Hylaeamys megacephalus and Oligoryzomys nigripes were the three most abundant species. In general, species diversity was negatively correlated with ENSO index, precipitation and precipitation anomaly, including cumulative one- to six-month cumulative values of each. Total sigmodontine abundance was positively correlated with the climatic variables. However, these correlations were not uniform among the three levels of habitat degradation, nor did the three abundant species show similar correlation patterns. The three most abundant species are each near their distributional limits, whereas several less abundant species have distributions that extend well beyond the study area. This somewhat counterintuitive result bears further investigation in other sites at ecoregional margins, to determine whether it is a commonly observed pattern, or an exception. Overall sigmodontine abundances were generally reflective of Akodon montensis abundance, which generally correlated with precipitation (including cumulative amounts). Our analyses of these longitudinal data showed two major effects on sigmodontine species diversity and population. First, they are impacted by habitat and secondly, they are affected by climate (ENSO, precipitation). However, individual species are not impacted similarly. Akodon montensis abundances primarily were correlated with abiotic (climatic) variables, and the correlations were consistent across habitats (biotic factors). In contrast, Hylaeamys megacephalus abundance was correlated with climatic variables in two habitats, but not the moderately-degraded habitat, and Oligoryzomys nigripes abundance was not correlated with climate in the most-degraded habitat. Pocos estudios se han centrado en las comunidades de roedores en los márgenes de una ecorregión o en los límites de las distribuciones de las especies, donde la comunidad puede ser más sensible a las variables extrínsecas, tanto bióticas como abióticas. Este estudio evalúa la diversidad de especies y la abundancia general de roedores sigmodontinos, y la variación asociada con las variables climáticas, en tres lugares con diferentes niveles de degradación del hábitat. Se establecieron tres parcelas de captura-marca-recaptura y se clasificaron como la menos, moderada y más degradadas basadas en un análisis de vegetación de varios parámetros. Las parcelas fueron muestreadas durante cinco noches consecutivas, seis veces durante dos años. La diversidad de Shannon y la abundancia general se calcularon para cada muestra. El índice mensual de ENOS multivariable y los valores de precipitación se obtuvieron de sitios accesibles en Internet. Las correlaciones producto-momento se calcularon entre los parámetros climáticos y de la comunidad, incluidos los valores acumulados para las variables climáticas. Se calcularon las mismas correlaciones para las tres especies comunes de sigmodontinos. Se registraron 1,632 capturas, representando 13 especies sigmodontinos. La riqueza de especies en las muestras (una sesión en una parcela) varió de cuatro a siete. Akodon montensis, Hylaeamys megacephalus y Oligoryzomys nigripes fueron las tres especies más abundantes. En general, la diversidad de especies se correlacionó negativamente con el índice ENOS, la precipitación y la anomalía de la precipitación, incluidos los valores acumulativos de uno a seis meses de cada uno. La abundancia total de sigmodontinos se correlacionó positivamente con las variables climáticas. Sin embargo, estas correlaciones no fueron uniformes entre los tres niveles de degradación del hábitat, ni tampoco entre las tres especies abundantes. Las tres especies más abundantes están cada una cerca de sus límites de distribución, mientras que varias especies menos abundantes tienen distribuciones que se extienden mucho más allá de este sitio. Este resultado algo contraintuitivo conlleva una mayor investigación en otros sitios en los márgenes ecorregionales, para determinar si es un patrón observado comúnmente, o una excepción. Las abundancias de sigmodontinos generalmente reflejaron la abundancia de Akodon montensis, que generalmente se correlacionó con la precipitación (incluidas las cantidades acumuladas). Las conclusiones destacadas de este estudio fueron: (1) diferentes niveles de degradación del hábitat se correlacionan con la variación en la diversidad de especies y la abundancia general de los sigmodontinos, y las especies individuales no muestran los mismos niveles de correlación entre los diferentes hábitats; y (2) la variabilidad climática (ENOS y precipitación) también afecta la diversidad de especies sigmodontinos y la abundancia de la población, y las especies comunes no muestran correlaciones similares entre sí. Las abundancias de Akodon montensis se correlacionaron principalmente con variables abióticas (climáticas), y las correlaciones fueron consistentes en todos los hábitats (factores bióticos). En contraste, la abundancia de Hylaeamys megacephalus se correlacionó con las variables climáticas en dos hábitats, pero no en el hábitat moderadamente degradado, y Oligoryzomys nigripes no se correlacionó con el clima en el hábitat más degradado.

Genomics meets applied ecology: Characterizing habitat quality for sloths in a tropical agroecosystem.

Understanding how habitat quality in heterogeneous landscapes governs the distribution and fitness of individuals is a fundamental aspect of ecology. While mean individual fitness is generally considered a key to assessing habitat quality, a comprehensive understanding of habitat quality in heterogeneous landscapes requires estimates of dispersal rates among habitat types. The increasing accessibility of genomic approaches, combined with field-based demographic methods, provides novel opportunities for incorporating dispersal estimation into assessments of habitat quality. In this study, we integrated genomic kinship approaches with field-based estimates of fitness components and approximate Bayesian computation (ABC) procedures to estimate habitat-specific dispersal rates and characterize habitat quality in two-toed sloths (Choloepus hoffmanni) occurring in a Costa Rican agricultural ecosystem. Field-based observations indicated that birth and survival rates were similar in a sparsely shaded cacao farm and adjacent cattle pasture-forest mosaic. Sloth density was threefold higher in pasture compared with cacao, whereas home range size and overlap were greater in cacao compared with pasture. Dispersal rates were similar between the two habitats, as estimated using ABC procedures applied to the spatial distribution of pairs of related individuals identified using 3,431 single nucleotide polymorphism and 11 microsatellite locus genotypes. Our results indicate that crops produced under a sparse overstorey can, in some cases, constitute lower-quality habitat than pasture-forest mosaics for sloths, perhaps because of differences in food resources or predator communities. Finally, our study demonstrates that integrating field-based demographic approaches with genomic methods can provide a powerful means for characterizing habitat quality for animal populations occurring in heterogeneous landscapes.

Relating flight initiation distance in birds to tropical dry forest restoration

Flight initiation distance (FID), defined as the distance at which an individual flees from an approaching predator, might depend on how the individual perceives the risk of being predated. Using a standardized walking approach method on focal bird individuals, we investigated whether different levels of vegetation cover (habitat) influence the perception of predation risk. To do this, we worked in an area of tropical dry forest in central Mexico that is currently part of a restoration ecology experiment. We hypothesized that restoration decreases individuals predation risk perception by increasing the complexity of the vegetation cover. The escape responses of three tropical birds with different diets and foraging strategies were also contrasted. There was no effect of habitat on FID, suggesting that birds in both habitats perceived predation risk in a similar manner. There was, however, a difference in FID among species: the Golden-cheeked Woodpecker tolerated closer human presence before flight than the Inca Dove and Streak-backed Oriole. This difference is likely due to the use of an alternative avoidance strategy of this species, which uses trunks for hiding. To decrease birds perceived predation risk, restoration intervention plans should include a mosaic of larger excluded plots located near relatively well-conserved sites to increase the area covered by vegetation.

Relating flight initiation distance in birds to tropical dry forest restoration

Flight initiation distance (FID), defined as the distance at which an individual flees from an approaching predator, might depend on how the individual perceives the risk of being predated. Using a standardized walking approach method on focal bird individuals, we investigated whether different levels of vegetation cover (habitat) influence the perception of predation risk. To do this, we worked in an area of tropical dry forest in central Mexico that is currently part of a restoration ecology experiment. We hypothesized that restoration decreases individuals predation risk perception by increasing the complexity of the vegetation cover. The escape responses of three tropical birds with different diets and foraging strategies were also contrasted. There was no effect of habitat on FID, suggesting that birds in both habitats perceived predation risk in a similar manner. There was, however, a difference in FID among species: the Golden-cheeked Woodpecker tolerated closer human presence before flight than the Inca Dove and Streak-backed Oriole. This difference is likely due to the use of an alternative avoidance strategy of this species, which uses trunks for hiding. To decrease birds perceived predation risk, restoration intervention plans should include a mosaic of larger excluded plots located near relatively well-conserved sites to increase the area covered by vegetation.(AU)

Ecological Status of a Patagonian Mountain River: Usefulness of Environmental and Biotic Metrics for Rehabilitation Assessment.

This work evaluates the consequences of anthropogenic pressures at different sections of a Patagonian mountain river using a set of environmental and biological measures. A map of risk of soil erosion at a basin scale was also produced. The study was conducted at 12 sites along the Percy River system, where physicochemical parameters, riparian ecosystem quality, habitat condition, plants, and macroinvertebrates were investigated. While livestock and wood collection, the dominant activities at upper and mean basin sites resulted in an important loss of the forest cover still the riparian ecosystem remains in a relatively good status of conservation, as do the in-stream habitat conditions and physicochemical features. Besides, most indicators based on macroinvertebrates revealed that both upper and middle basin sections supported similar assemblages, richness, density, and most functional feeding group attributes. Instead, the lower urbanized basin showed increases in conductivity and nutrient values, poor quality in the riparian ecosystem, and habitat condition. According to the multivariate analysis, ammonia level, elevation, current velocity, and habitat conditions had explanatory power on benthos assemblages. Discharge, naturalness of the river channel, flood plain morphology, conservation status, and percent of urban areas were important moderators of plant composition. Finally, although the present land use in the basin would not produce a significant risk of soil erosion, unsustainable practices that promotes the substitution of the forest for shrubs would lead to severe consequences. Mitigation efforts should be directed to protect headwater forest, restore altered riparian ecosystem, and to control the incipient eutrophication process.

Comparison of fish and macroinvertebrates as bioindicators of Neotropical streams.

The biomonitoring of aquatic ecosystems in developing countries faces several limitations, especially related to gathering resources. The present study aimed at comparing the responses of fish and benthic macroinvertebrates to environmental change, to identify which group best indicates the differences between reference and impacted streams in southern Brazil. We determined reference and impacted sites based on physical and chemical variables of the water. For the analysis and comparison of biological responses, we calculated 22 metrics and submitted them to a discriminant analysis. We selected from this analysis only six metrics, which showed that the two studied assemblages respond differently to environmental change. A larger number of metrics were selected for macroinvertebrates than for fish in the separate analysis. The metrics selected for macroinvertebrates in the pooled analysis (i.e., fish and macroinvertebrates together) were different from those selected in the separate analysis for macroinvertebrates alone. However, the metrics selected for fish in the pooled analysis were the same selected in the separate analysis for fish alone. The macroinvertebrate assemblage was more effective for distinguishing reference from impacted sites. We suggest the use of macroinvertebrates as bioindicators of Neotropical streams, especially in situations in which time and money are short.

Structure and integrity of fish assemblages in streams associated to conservation units in Central Brazil

This study aims to characterize the spatial and seasonal distribution of the fish assemblage and evaluate the integrity of streams in a sustainable use area that includes integral protection conservation units in Distrito Federal, Central Brazil (Cerrado biome). For the study, 12 stretches of 8 streams were sampled in 2008 (dry season) and 2009 (wet season). For that evaluation was estimated the Physical Habitat Index (PHI), vegetation cover (VC), pH, dissolved oxygen, turbidity, and conductivity. We recorded 22 species, about eight undescribed species, by a total of 2,327 individuals. The most representative families in number of species were Characidae (31.8 percent), Loricariidae (31.8 percent), and Crenuchidae (13.6 percent). Knodus moenkhausii was the most abundant species with 1,476 individuals, added to Astyanax sp., Phalloceros harpagos, and Hasemania sp. they represent over 95 percent of the total abundance. The species Astyanax sp. (occurring in 79.2 percent of the stretches) and K. moenkhausii (50.0 percent) were considered constant in both seasons. The longitudinal gradient (River Continuum) exerts a strong influence on the studied assemblage. According to CCA, the variables that structure the fish assemblage are based on aspects related to water volume and habitat complexity. No seasonal variation in richness, diversity, abundance, and mass were detected. A cluster analysis suggests a separation of species composition between the stretches of higher and lower orders, which was not observed for seasonality. The streams were considered well preserved (mean PHI 82.9±7.5 percent), but in some stretches were observed anthropogenic influence, detected in the water quality and, mainly, on the riparian vegetation integrity. The exotic species Poecilia reticulata was sampled in the two stretches considered most affected by anthropogenic activities by PHI, conductivity, and VC.

Esse estudo teve como objetivo caracterizar a distribuição espacial e sazonal da taxocenose de peixes e avaliar a integridade dos córregos de uma área de uso sustentável que inclui unidades de conservação de proteção integral no Distrito Federal, Brasil Central (bioma Cerrado). Para o estudo, foram amostrados 12 trechos de oito cursos d'água em 2008 (estação seca) e 2009 (estação chuvosa). Para essa avaliação foram utilizados o Índice Físico do Habitat (IFH), cobertura vegetal (CV), pH, oxigênio dissolvido, turbidez e condutividade. Foram coletadas 22 espécies, sendo oito não descritas, em um total de 2.327 indivíduos. As famílias mais representativas em número de espécies foram Characidae (31,8 por cento), Loricariidae (31,8 por cento) e Crenuchidae (13,6 por cento). Knodus moenkhausii foi a espécie mais abundante, com 1.476 indivíduos, que juntamente com Astyanax sp., Phalloceros harpagos e Hasemania sp. representaram mais de 95 por cento da abundância total. As espécies Astyanax sp. (ocorrendo em 79,2 por cento dos trechos) e K. moenkhausii (50,0 por cento) foram consideradas constantes nas duas estações. O gradiente longitudinal (rio Contínuo) exerce forte influência na taxocenose estudada. De acordo com a CCA, as variáveis que estruturam a taxocenose íctica se baseiam em aspectos relacionados ao volume e complexidade dos habitats. Não foi detectada variação sazonal na riqueza, diversidade, abundância e massa. Uma análise de agrupamento sugere uma separação na composição de espécies entre trechos de maiores e menores ordens, o que não foi observado para a sazonalidade. Os córregos da APA encontram-se relativamente bem preservados (IFH médio de 82,9±7,5 por cento), porém em alguns trechos foi observada certa influência antrópica, detectada na qualidade da água e, principalmente, na integridade da vegetação ripária. A espécie exótica Poecilia reticulata foi coletada nos dois trechos considerados mais afetados por atividades antrópicas de acordo com o IFH, condutividade e CV.

Structure and integrity of fish assemblages in streams associated to conservation units in Central Brazil

This study aims to characterize the spatial and seasonal distribution of the fish assemblage and evaluate the integrity of streams in a sustainable use area that includes integral protection conservation units in Distrito Federal, Central Brazil (Cerrado biome). For the study, 12 stretches of 8 streams were sampled in 2008 (dry season) and 2009 (wet season). For that evaluation was estimated the Physical Habitat Index (PHI), vegetation cover (VC), pH, dissolved oxygen, turbidity, and conductivity. We recorded 22 species, about eight undescribed species, by a total of 2,327 individuals. The most representative families in number of species were Characidae (31.8 percent), Loricariidae (31.8 percent), and Crenuchidae (13.6 percent). Knodus moenkhausii was the most abundant species with 1,476 individuals, added to Astyanax sp., Phalloceros harpagos, and Hasemania sp. they represent over 95 percent of the total abundance. The species Astyanax sp. (occurring in 79.2 percent of the stretches) and K. moenkhausii (50.0 percent) were considered constant in both seasons. The longitudinal gradient (River Continuum) exerts a strong influence on the studied assemblage. According to CCA, the variables that structure the fish assemblage are based on aspects related to water volume and habitat complexity. No seasonal variation in richness, diversity, abundance, and mass were detected. A cluster analysis suggests a separation of species composition between the stretches of higher and lower orders, which was not observed for seasonality. The streams were considered well preserved (mean PHI 82.9±7.5 percent), but in some stretches were observed anthropogenic influence, detected in the water quality and, mainly, on the riparian vegetation integrity. The exotic species Poecilia reticulata was sampled in the two stretches considered most affected by anthropogenic activities by PHI, conductivity, and VC.(AU)

Esse estudo teve como objetivo caracterizar a distribuição espacial e sazonal da taxocenose de peixes e avaliar a integridade dos córregos de uma área de uso sustentável que inclui unidades de conservação de proteção integral no Distrito Federal, Brasil Central (bioma Cerrado). Para o estudo, foram amostrados 12 trechos de oito cursos d'água em 2008 (estação seca) e 2009 (estação chuvosa). Para essa avaliação foram utilizados o Índice Físico do Habitat (IFH), cobertura vegetal (CV), pH, oxigênio dissolvido, turbidez e condutividade. Foram coletadas 22 espécies, sendo oito não descritas, em um total de 2.327 indivíduos. As famílias mais representativas em número de espécies foram Characidae (31,8 por cento), Loricariidae (31,8 por cento) e Crenuchidae (13,6 por cento). Knodus moenkhausii foi a espécie mais abundante, com 1.476 indivíduos, que juntamente com Astyanax sp., Phalloceros harpagos e Hasemania sp. representaram mais de 95 por cento da abundância total. As espécies Astyanax sp. (ocorrendo em 79,2 por cento dos trechos) e K. moenkhausii (50,0 por cento) foram consideradas constantes nas duas estações. O gradiente longitudinal (rio Contínuo) exerce forte influência na taxocenose estudada. De acordo com a CCA, as variáveis que estruturam a taxocenose íctica se baseiam em aspectos relacionados ao volume e complexidade dos habitats. Não foi detectada variação sazonal na riqueza, diversidade, abundância e massa. Uma análise de agrupamento sugere uma separação na composição de espécies entre trechos de maiores e menores ordens, o que não foi observado para a sazonalidade. Os córregos da APA encontram-se relativamente bem preservados (IFH médio de 82,9±7,5 por cento), porém em alguns trechos foi observada certa influência antrópica, detectada na qualidade da água e, principalmente, na integridade da vegetação ripária. A espécie exótica Poecilia reticulata foi coletada nos dois trechos considerados mais afetados por atividades antrópicas de acordo com o IFH, condutividade e CV.(AU)

Habitat-specific effects of food abundance on the condition of ovenbirds wintering in Jamaica.

1. Food availability has been considered one of the most important factors limiting bird populations, yet the effects of food abundance on non-breeding insectivores has rarely been investigated. We studied the effects of food abundance on the body condition of ovenbirds (Seiurus aurocapillus L.), a sexually monomorphic, ground-foraging, Neotropical-Nearctic migrant warbler during two winters in three habitats on their wintering grounds in Jamaica. 2. Prey biomass decreased from early to late winter in all habitats. Concurrently, ovenbird body mass, corrected for differences in structural size, decreased significantly in five of six habitat-year combinations. Only in second growth scrub habitat in the 1995-96 winter did ovenbirds show no decrease in corrected body mass, and during this period there was no significant decrease in ant biomass, the dominant prey item of ovenbirds in all habitats. 3. Significant positive correlations were found between ovenbirds' rate of feather regrowth and the biomass of ants on their home ranges in early winter, and between overwinter change in ovenbird body mass and the biomass of ants on their home ranges in late winter. 4. The results of both the habitat- and home-range-based analyses suggest a similar threshold of ant biomass (2·5-3·0 mg m-2 ), below which ovenbirds did not maintain their body mass. 5. The results suggest that late winter rainfall mediates the biomass of prey abundance, which in turn affects the ovenbirds' overwinter body condition.