Constraints on avian seed dispersal reduce potential for resilience in degraded tropical forests

1. Seed dispersal is fundamental to tropical forest resilience. Forest loss or degradation typically leads to defaunation, altering seed transfer dynamics and impairing the ability of forested habitats to regenerate or recover from perturbation. However, the extent of defaunation, and its likely impacts on the seed dispersers needed to restore highly degraded or clear‐felled areas, remains poorly understood in tropical forest landscapes. 2. To quantify defaunation of seed‐dispersing birds, we used field survey data from 499 transects in three forested regions of Brazil, first comparing the observed assemblages with those predicted by geographic range maps, and then assessing habitat associations of frugivores across land cover gradients. 3. We found that current bird assemblages have lower functional diversity (FD) than predicted by species range maps in Amazonia (4%–6%), with a greater reduction in FD (28%) for the Atlantic Forest, which has been more heavily deforested for a longer period. 4. Direct measures of seed dispersal are difficult to obtain, so we focused on potential seed transfer inferred from shared species occurrence. Of 83 predominantly frugivorous bird species recorded in relatively intact forests, we show that 10% were absent from degraded forest, and 57% absent from the surrounding matrix of agricultural land covers, including many large‐gaped species. Of 112 frugivorous species using degraded forest, 47% were absent from matrix habitats. Overall, frugivores occurring in both intact forest and matrix habitats were outnumbered by (mostly small‐gaped) frugivores occurring in both degraded forest and matrix habitats (23 additional species; 64% higher diversity). 5. These findings suggest that birds have the potential to disperse seeds from intact and degraded forest to adjacent cleared lands, but that direct seed transfer from intact forests is limited, particularly for large‐seeded trees. Degraded forests may play a vital role in supporting natural regeneration of small‐seeded tree species as well as providing a ‘stepping‐stone’ in the regeneration pathway for large‐seeded trees. We propose that both intact and degraded forests will support the restoration potential of tropical forest landscapes, and that bird‐assisted seed dispersal can be enhanced by maintaining buffer zones of degraded or secondary forests around remaining intact forest patches

Mediation of area and edge effects by adjacent land use.

Habitat loss, fragmentation and degradation have pervasive detrimental effects on tropical forest biodiversity, but the role of the surrounding land use (i.e. matrix) in determining the severity of these impacts remains poorly understood. We surveyed bird species across an interior-edge-matrix gradient to assess the effects of matrix type on biodiversity at 49 different sites with varying levels of landscape fragmentation in the Brazilian Atlantic Forest - a highly threatened biodiversity hotspot. Our findings revealed that both area and edge effects are more pronounced in forest patches bordering pasture matrix, while patches bordering Eucalyptus plantation maintained compositionally similar bird communities between the edge and the interior, in addition to exhibiting reduced effects of patch size. These results suggest that the type of matrix in which forest fragments are situated can explain a substantial amount of the widely-reported variability in biodiversity responses to forest loss and fragmentation. This article is protected by copyright. All rights reserved

Lost, gained, and regained functional and phylogenetic diversity of European mammals since 8000 years ago

Mammals have experienced high levels of human-mediated extirpations but have also been widely introduced to new locations, and some have recovered from historic persecution. Both of these processes—losses and gains—have resulted in concern about functional losses and changes in ecological communities as new ecological states develop. The question of whether species turnover inevitably leads to declines in functional and phylogenetic diversity depends, however, on the traits and phylogenetic distinctiveness of the species that are lost, gained, or regained. Comparing ~8000 years ago with the last century, we show that extirpations and range retractions have indeed reduced the functional and phylogenetic diversity of mammals in most European regions (countries and island groups), but species recoveries and the introduction of non-native species have increased functional and phylogenetic diversity by equivalent or greater amounts in many regions. Overall, across Europe, the median species richness showed no change; median phylogenetic diversity increased by 0.7% over the last 8000 years, while median functional diversity decreased by 0.6%. The balance of losses (extirpations) and gains (introductions, range expansions) has, however, led to net increases in functional diversity on many islands, where the original diversity was low, and across most of western Europe. Historically extirpated mega- and mesofaunal species have recolonized or been reintroduced to many European regions, contributing to recent functional and phylogenetic diversity recovery. If conservation rewilding projects continue to reintroduce regionally extirpated species and domestic descendants of “extinct” species to provide replacement grazing, browsing, and predation, there is potential to generate net functional and phylogenetic diversity gains (relative to 8000 years ago) in most European regions

Constraints on avian seed dispersal reduce potential for resilience in degraded tropical forests

Seed dispersal is fundamental to tropical forest resilience. Forest loss or degradation typically leads to defaunation, altering seed transfer dynamics and impairing the ability of forested habitats to regenerate or recover from perturbation. However, the extent of defaunation, and its likely impacts on the seed dispersers needed to restore highly degraded or clear‐felled areas, remains poorly understood in tropical forest landscapes. To quantify defaunation of seed‐dispersing birds, we used field survey data from 499 transects in three forested regions of Brazil, first comparing the observed assemblages with those predicted by geographic range maps, and then assessing habitat associations of frugivores across land cover gradients. We found that current bird assemblages have lower functional diversity (FD) than predicted by species range maps in Amazonia (4%–6%), with a greater reduction in FD (28%) for the Atlantic Forest, which has been more heavily deforested for a longer period. Direct measures of seed dispersal are difficult to obtain, so we focused on potential seed transfer inferred from shared species occurrence. Of 83 predominantly frugivorous bird species recorded in relatively intact forests, we show that 10% were absent from degraded forest, and 57% absent from the surrounding matrix of agricultural land covers, including many large‐gaped species. Of 112 frugivorous species using degraded forest, 47% were absent from matrix habitats. Overall, frugivores occurring in both intact forest and matrix habitats were outnumbered by (mostly small‐gaped) frugivores occurring in both degraded forest and matrix habitats (23 additional species; 64% higher diversity). These findings suggest that birds have the potential to disperse seeds from intact and degraded forest to adjacent cleared lands, but that direct seed transfer from intact forests is limited, particularly for large‐seeded trees. Degraded forests may play a vital role in supporting natural regeneration of small‐seeded tree species as well as providing a ‘stepping‐stone’ in the regeneration pathway for large‐seeded trees. We propose that both intact and degraded forests will support the restoration potential of tropical forest landscapes, and that bird‐assisted seed dispersal can be enhanced by maintaining buffer zones of degraded or secondary forests around remaining intact forest patches. Read the free Plain Language Summary for this article on the Journal blog

Deforestation alters species interactions

Interspecific interactions are a major determinant of stability in ecological communities, and are known to vary with biotic and abiotic conditions. Deforestation is the primary driver of the ongoing sixth mass extinction, yet its effect on species interactions remains largely unexplored. We investigate how deforestation affects species interactions using a complex systems model and a co-occurrence dataset of 363 bird species, observed across 134 sites, from five regions across the Brazilian Atlantic Forest totalling 27,226 interactions. Both theoretical and empirical results show that interspecific interactions vary non-monotonically with forest cover, and are more positive than average in areas with higher forest cover, and to a lesser extent in highly deforested areas. Observed differences in interactions reflect both species turnover and changes in pairwise interactions. Our results point to changes in stability across the gradient of deforestation that may lead to varying community resilience to environmental perturbations

Deforestation alters species interactions

Abstract Interspecific interactions are a major determinant of stability in ecological communities and are known to vary with biotic and abiotic conditions. Deforestation is the primary driver of the ongoing sixth mass extinction, yet its effect on species interactions remains largely unexplored. We investigate how deforestation affects species interactions using a complex systems model and a co‐occurrence dataset of 363 bird species, observed across 134 sites, from 5 regions across the Brazilian Atlantic Forest totalling 27,226 interactions. Both theoretical and empirical results show that interspecific interactions vary non‐monotonically with forest cover and are more positive than average in areas with higher forest cover, and to a lesser extent in highly deforested areas. Observed differences in interactions reflect both species turnover and changes in pairwise interactions. Our results point to changes in stability across the gradient of deforestation that may lead to varying community resilience to environmental perturbations. Key Interdisciplinary Aspects Species interactions are expected to vary due to the biological, chemical and physical changes caused by deforestation on their local environment. We use a mathematical complex systems approach, as well as ecological data, to show that species interactions are more positive in highly forested areas. We propose that the alteration of species interactions caused by deforestation will affect the stability of communities and their resilience to future perturbations (e.g. climate change)

The Continuing Relevance of 19th-Century Philosophy of Psychology: Brentano and the Autonomy of Psychological Methods

This paper provides an analysis of Franz Brentano’s thesis that psychology employs a distinctive method, which sets it apart from physiology. The aim of the paper is two-fold: First, I situate Brentano’s thesis (and the broader metaphysical system that underwrites it) within the context of specific debates about the nature and status of psychology, arguing that we regard him as engaging in a form of boundary work. Second, I explore the relevance of Brentano’s considerations to more recent debates about autonomy on the one hand and theoretical and/or methodological integration on the other. I argue that Brentano puts his finger on the idea that an integrated research process presupposes the existence of distinct methods and approaches, and that he highlights the philosophical challenge of accounting for such distinct methods. I suggest that Brentano’s ideas offer unconventional perspectives on current debates, in particular regarding first-person methods and the investigative process in cognitive science