Ecological network complexity scales with area

Larger geographical areas contain more species—an observation raised to a law in ecology. Less explored is whether biodiversity changes are accompanied by a modification of interaction networks. We use data from 32 spatial interaction networks from different ecosystems to analyse how network structure changes with area. We find that basic community structure descriptors (number of species, links and links per species) increase with area following a power law. Yet, the distribution of links per species varies little with area, indicating that the fundamental organization of interactions within networks is conserved. Our null model analyses suggest that the spatial scaling of network structure is determined by factors beyond species richness and the number of links. We demonstrate that biodiversity–area relationships can be extended from species counts to higher levels of network complexity. Therefore, the consequences of anthropogenic habitat destruction may extend from species loss to wider simplification of natural communities.This work was supported by the TULIP Laboratory of Excellence (ANR-10-LABX-41 and 394 ANR-11-IDEX-002-02) to J.M.M., by a Region Midi-Pyrenees project (CNRS 121090) to J.M.M., and by the FRAGCLIM Consolidator Grant (726176) to J.M.M. from the European Research Council under the European Union’s Horizon 2020 Research and Innovation Program. The study was also supported by Spanish MICINN projects CGL2009-12646, CSD2008-0040 and CGL2013-41856 to J.B. and A.R. C.E. was funded through the São Paulo Research Foundation (FAPESP 2015/15172-7). V.A.G.B. was funded by National Funds through FCT—Foundation for Science and Technology under the Project UIDB/05183/2020. W.T. received funding from the ERA-Net BiodivERsA—Belmont Forum, with the national funder Agence National pour la Recherche (FutureWeb: ANR-18-EBI4–0009 and BearConnect: ANR-16-EBI3-0003).Peer reviewe

Bird-habitat associations in coastal rangelands of southern Brazil

Nearly all remnants of temperate grasslands in southeastern South America are used for livestock ranching and are subject to habitat degradation resulting from this activity. Exploring how habitat features affect the composition of grassland avifaunal communities is a first step to understand how current cattle-ranching management practices impact avian diversity. We used canonical ordination to test for relationships between five habitat variables and the composition of the bird community in coastal grasslands in southern Brazil. We sampled pastures with different heights, from overgrazed short-grass to tall herbaceous vegetation. We recorded 1,535 individuals and 27 species of birds. The first ordination axis indicated a strong contribution of mean vegetation height on the composition of the bird community, whereas the second axis revealed the influence of herbaceous vegetation patchiness and woody vegetation cover. Three groups of species were revealed by the ordination: one more diffuse associated with intermediate and tall herbaceous vegetation, another with short grass, and a third with vegetation patchiness and woody vegetation. Species restricted to tall herbaceous vegetation are negatively impacted from habitat degradation resulting from overgrazing and trampling by livestock, and mowing and burning of tall plants. Occurrence of these species in our study area is related with the presence of swales immediately behind the dune system and where remnants of tall vegetation persist. Birds of pastures with ample cover of short herbaceous plants, including one globally threatened species and six other restricted to short-grass habitat, apparently benefit from local livestock management practices. Woody vegetation possibly functions as a keystone structure, enabling the occurrence in grasslands of avian species that rely on shrubby habitat. Although livestock ranching promotes the diversity of habitats by creating distinct patches of vegetation height in grasslands, current management practices directed to the maintenance of short grass pastures may eliminate an entire subset of species, including regionally threatened taxa, and reduce avian diversity. The maintenance of large patches of tall herbaceous plants is needed to ensure the survival of species reliant on this type of grassland structure in our study area

First nesting record of the Bay-Capped Wren-Spinetail Spartonoica maluroides (Aves, Furnariidae) in Brazil, with nest and nestling descriptions and notes on breeding behavior

The only breeding record of Spartonoica maluroides (d'Orbigny & Lafresnaye, 1837) for Brazil is based on the observation of a fledgling in southern Rio Grande do Sul in January 1976. On 7 December 2005 we discovered a nest containing three nestlings at the southeastern end of Lagoa Pequena, municipality of Pelotas, Rio Grande do Sul. The nest was concealed at the base of a cavity in a Spartina densiflora (Poaceae) tussock located at the edge of a saltmarsh. The nest was built of fine pieces of dead Scirpus olneyi (Cyperaceae) and S. densiflora leaves firmly interlaced to the internal leaves of the tussock. Live leaves of S. densiflora lining the cavity comprised a substantial part of the nest's architecture, forming most of its upper lateral walls and roof. The lower section was more elaborate, resembling a deep cup and forming a distinct incubation chamber. Adults reached the nest's interior through an irregular apical opening amidst the leaves. The nest was 244 mm high and 140 mm wide. The incubation chamber had an external diameter of 138.5 mm, an internal diameter of 79.4 mm and was 86 mm deep. It was lined with fine leaves and white plant fibers. Nestlings were five to six days old. A total of 107 neossoptiles restricted to the capital, spinal and alar tracts were recorded in one nestling. The distribution of neossoptiles in the ocular region of S. maluroides forms a distinct pattern which can be typical of Furnariidae and related families. Two adults attended the nest, bringing small insects to the nestlings and removing fecal sacs. We recorded at least 74 visits to the nest during a ca. 6 h period during an afternoon. The average number of visits per hour was 12.8 ± 1.3. An adult bird spent on average 0.7 ± 0.56 minutes inside the nest attending nestlings. The nest remained unattended on average for 3.61 ± 3.13 minutes. The hour of the day had no influence on the amount of time spent by an adult in the nest or away from it. We returned to the area on 15 December 2005 and found the nest abandoned. Observations confirm that S. maluroides is a resident breeder in southern Brazil and that the saltmarshes of the Lagoa do Patos estuary are an important year-round habitat for the species. A nestling and the nest were collected to document the record.O único registro de reprodução de Spartonoica maluroides (d'Orbigny & Lafresnaye, 1837) no Brasil é baseado na observação de um filhote recém-saído do ninho no sul do Rio Grande do Sul em janeiro de 1976. Em 7 de dezembro de 2005, descobrimos um ninho contendo três filhotes na extremidade sudoeste da Lagoa Pequena, município de Pelotas, Rio Grande do Sul. O ninho estava oculto na base de uma cavidade dentro de uma touceira de Spartina densiflora (Poaceae) situada na margem de uma marisma. O ninho era constituído de pedaços delgados de folhas mortas de Scirpus olneyi (Cyperaceae) e S. densiflora firmemente entrelaçados às folhas da touceira. Folhas vivas de S. densiflora que orlavam a cavidade compreendiam uma parte substancial da arquitetura do ninho, constituindo a maior parte da porção superior das paredes laterais e o teto. A seção inferior era mais elaborada, similar a uma taça profunda e formando uma câmara incubatória distinta. Os adultos acessavam o ninho através de uma abertura apical de formato irregular por entre as folhas. O ninho media 244 mm de altura e 140 mm de largura. A câmara incubatória apresentava um diâmetro externo de 138,5 mm, um diâmetro interno de 79,4 mm e uma profundidade de 86 mm, sendo forrada de folhas delgadas e fibras vegetais brancas. Os ninhegos tinham de cinco a seis dias de idade. Um ninhego exibiu um total de 107 neossóptilas restritas aos tratos capital, espinal e alar. A distribuição das neossóptilas na região ocular de S. maluroides forma um padrão distinto que pode ser típico de Furnariidae e famílias afins. Dois adultos atendiam o ninho, trazendo pequenos insetos para os ninhegos e removendo sacos fecais. Registramos pelo menos 74 visitas ao ninho em um período de ca. 6 h durante uma tarde. O número médio de visitas por hora foi de 12,8 ± 1,3. Os adultos permaneceram em média 0,7 ± 0,56 minutos dentro do ninho atendendo os filhotes. O ninho permaneceu sem atendimento em média por 3,61 ± 3,13 minutos. O horário do dia não influenciou o tempo de permanência dos adultos no ninho ou longe deste. Retornamos ao local em 15 de dezembro de 2005 e encontramos o ninho abandonado. Observações confirmam que S. maluroides é um residente reprodutor no sul do Brasil e que as marismas do estuário da Lagoa dos Patos constituem um importante hábitat para a espécie durante todo o ano. Um ninhego e o ninho foram coletados para documentar o registro

Network and parasitological analyses reveal latitudinal gradient in bats‐ectoparasitic fly interactions across the Neotropic

Abstract Ecological interactions between parasites and their hosts play a fundamental role in evolutionary processes. Selection pressures are exerted on parasites and their hosts, usually resulting in high levels of specificity. Such is the case of ectoparasitic bat‐flies, but how large‐scale spatial gradients affect the dynamics of their interactions with their bat hosts is still unknown. In the present study, we investigated interaction patterns between bats and their ectoparasitic flies (Streblidae and Nycteribiidae), both presenting their peak of diversity in the Neotropical region, along a latitudinal gradient. Using network analyses and parasitic indices, grounded on the latitudinal diversity gradient pattern, we evaluated how spatial gradients affect species interactions and parasitic indices at the biogeopraphic scale, with increasing species richness in interaction networks closer to the tropics, leading to increases in network modularity, size, and specialization, and to a decrease in nesting and connectivity. We conducted a literature review, focusing on studies done in the Neotropical region, and own data. We obtained a bat richness of 97 species parasitized by 128 species of ectoparasitic flies, distributed into 57 interaction networks between latitudes 29° S and 19° N in the Neotropic. Network metrics and parasitic indices varied along the latitudinal gradient, with changes in the richness of bats and their ectoparasitic flies and in the structure of their interactions; network specialization, modularity, and connectance increase with latitude, while network size decreases with latitude. Regions closer to the equator had higher parasite loads. Our results show that interaction network metrics present a latitudinal gradient and that such interactions, when observed at a local scale, hide variations that only become perceptible at larger scales. In this way, ectoparasites such as bat flies are not only influenced by the ecology and biology of their hosts, but also by other environmental factors acting directly on their distribution and survival

Shifts in composition of avian communities related to temperate-grassland afforestation in southeastern South America

Afforestation of temperate grasslands with fast-growing trees for industrial pulpwood production is spreading in South America. Despite high afforestation rates resulting from governmental policies that stimulate pulpwood production in grasslands of southern Brazil and Uruguay, the impact of this activity on biodiversity remains to be properly assessed. We used an Impact-Reference study design to evaluate how grassland afforestation affects the composition of grassland bird assemblages. We sampled eucalyptus plantations and neighboring natural grasslands in southern Brazil from 2006-2009, and relied on nested sampling and analysis to separate the effects of afforestation from the natural variability of grasslands. We recorded a significant difference in composition between assemblages from grasslands and tree plantations. Species adapted to open, treeless areas tended to be negatively affected in relation to edge or forest birds in eucalyptus plantations. Afforestation is systematically replacing the bird assemblage of hilltop grasslands by a collection of common edge and forest species that occur in nearby riverine and hillside forests. Although most grassland birds negatively affected by tree plantations are common and widespread, observed and predicted afforestation rates in southeastern South America may result in regional population reductions in the near future

The impact of climate warming on species diversity across scales: Lessons from experimental meta‐ecosystems

International audienceAim: To evaluate the effects of climate warming on biodiversity across spatial scales (i.e., α-, βand γ-diversity) and the effects of patch openness and experimental context on diversity responses. Location: Global Time period: 1995-2017 Major taxa studies: Fungi, Invertebrates, Phytoplankton, Plants, Sea weed, Soil Microbes, Zooplankton Methods: We compiled data from warming experiments and conducted a meta-analysis to evaluate the effects of warming on different components of diversity (such as species richness and equivalent numbers) at different spatial scales (α-, β-and γ-diversity, partitioning β-diversity into species turnover and nestedness components). We also investigated how these effects were modulated by system openness, defined as the possibility of replicates being colonized by new species, and experimental context (duration, mean temperature change and ecosystem type). Results: Experimental warming did not affect local species richness (α-diversity) but decreased effective numbers of species by affecting species dominance. Warming increased species spatial turnover (β-diversity), although no significant changes were detected at the regional scale (γdiversity). Site openness and experimental context did not significantly affect our results, despite significant heterogeneity in the effect sizes of α-and β-diversity. Main conclusions: Our meta-analysis shows that the effects of warming on biodiversity are scaledependent. While local and regional inventory diversity remain unaltered, species composition across temperature gradients and the patterns of species dominance change with temperature, creating novel communities that might be harder to predict