Land use and elevation interact to shape bird functional and phylogenetic diversity and structure: Implications for designing optimal agriculture landscapes

Orchards and paddy differentially impact rock outcrop amphibians: Insights from community- and species-level responses

With agricultural demands increasing globally, determining the nature of impacts of different forms of agriculture on biodiversity, especially for threatened vertebrates and habitats, is critical to inform land management. This is especially true for open ecosystems such as the natural rock outcrops and amphibians, both of which are threatened by land-use change. Lateritic plateaus of the northern Western Ghats are rock outcrop ecosystems harboring endemic biodiversity. Since most of these plateaus are located outside protected areas and officially classified as wastelands, they are rapidly lost due to multiple human pressures, including agriculture. We compared amphibian composition, diversity, and species responses across these rocky plateaus (hereafter plateaus), orchards, and rice paddy in the Western Ghats-Sri Lanka biodiversity Hotspot, India. We sampled 50 belt transects across four geographically separated plateaus, covering three land-use classes in three of the plateaus, and recorded information on amphibians and their microhabitats. Each transect was sampled four times across the rainy season. We compared responses of amphibians across three land-use categories at the community level using Hill numbers, beta-diversity measures, and nonmetric multidimensional scaling, and at the species level using joint species distribution modeling. Converting plateaus to paddy and orchards significantly altered microhabitat availability by reducing the rock pool habitat availability in paddy and orchards, and increased deep, water-submerged areas and grass cover in paddy. Conversion to paddy mostly had species- and community-level impacts, that is, lowered species occurrence of certain species, lowered species richness, and more nested communities, whereas conversion to orchards mostly had species-level impacts, that is, lowered species occurrence, highlighting that different forms of agriculture have varying impacts on amphibians that can be determined by examining community- and species-level effects simultaneously. Using only community- or species-level metrics would not have unraveled these impacts completely. We show that large rock pools are critical microhabitats for frogs, most likely serving as refugia and protecting frogs from desiccation during dry spells in monsoons. Since Indian lateritic plateau habitats in low elevations are rapidly being converted to orchards, efforts are needed to conserve them in partnership with local communities, the custodians of these habitats.

Forest disturbance increases functional diversity but decreases phylogenetic diversity of an arboreal tropical ant community

Tropical rainforest trees host a diverse arthropod fauna that can be characterised by their functional diversity (FD) and phylogenetic diversity (PD). Human disturbance degrades tropical forests, often coinciding with species invasion and altered assembly that leads to a decrease in FD and PD. Tree canopies are thought to be particularly vulnerable, but rarely investigated. Here, we studied the effects of forest disturbance on an ecologically important invertebrate group, the ants, in a lowland rainforest in New Guinea. We compared an early successional disturbed plot (secondary forest) to an old-growth plot (primary forest) by exhaustively sampling their ant communities in a total of 852 trees. We expected that for each tree community (1) disturbance would decrease FD and PD in tree-dwelling ants, mediated through species invasion. (2) Disturbance would decrease ant trait variation due to a more homogeneous environment. (3) The main drivers behind these changes would be different contributions of true tree-nesting species and visiting species. We calculated FD and PD based on a species-level phylogeny and 10 ecomorphological traits. Furthermore, we assessed by data exclusion the influence of species, which were not nesting in individual trees (visitors) or only nesting species (nesters), and of non-native species on FD and PD. Primary forests had higher ant species richness and PD than secondary forest. However, we consistently found increased FD in secondary forest. This pattern was robust even if we decoupled functional and phylogenetic signals, or if non-native ant species were excluded from the data. Visitors did not contribute strongly to FD, but they increased PD and their community weighted trait means often varied from nesters. Moreover, all community-weighted trait means changed after forest disturbance. Our finding of contradictory FD and PD patterns highlights the importance of integrative measures of diversity. Our results indicate that the tree community trait diversity is not negatively affected, but possibly even enhanced by disturbance. Therefore, the functional diversity of arboreal ants is relatively robust when compared between old-growth and young trees. However, further study with higher plot-replication is necessary to solidify and generalise our findings.

Effects of Landscape Context on Bird Community in the Subtropical Evergreen Broad-Leaved Forest of Wuyishan National Park

Landscape context can reflect the habitat structure and play an important role in bird species occurrences and abundance. For local biodiversity conservation and restoration, we examined the effects of landscape context on bird communities at different altitude gradients. Our study was conducted in four altitude gradients (<300 m, 300-599 m, 600-899 m, 900-1200 m) of subtropical evergreen broad-leaved forest in Wuyishan National Park, China. The bird survey was carried out in 115 transects in spring, summer, autumn and winter. We examined the effects of altitude, season and landscape context. The result showed that (1) species richness and abundance at <300 m altitude were highest among the four altitude gradients, and they showed more significant differences than those at other altitude gradients; (2) the species richness of birds was associated with altitude, season and landscape context, as the season is more significant than other explanatory variables; (3) at the landscape level, habitat configuration is more important. The average canopy height and contagion index positively correlated with the species richness and abundance of birds at all four altitude gradients. In particular, the average canopy height is significant at 300-599 m and 600-899 m altitude gradients. The study results can provide a theoretical basis and guidance for future national park conservation and management and ecological restoration in the subtropical evergreen broad-leaved forest regions.

Trade-offs between economic development and biodiversity conservation on a tropical island

Resolving trade-offs between economic development and biodiversity conservation needs is one of the defining issues of our time. This is crucial in currently developing countries and in particularly sensitive systems harboring high biodiversity. Yet, such a task can be challenging as human activities may have complex effects on biodiversity. Here we assessed the effects of intense economic development on different components of biodiversity using Hainan Island (South China) as model. This highly biodiverse tropical island has experienced intense economic development and extensive forest to agriculture conversion and urbanization across the last two decades. We characterized three main habitat clusters, based on local land use, climate and economic changes across 145 grids (10×10 km), and estimated avian biodiversity responses between 1998 and 2013. We recorded ongoing taxonomic biotic homogenization at the regional scale (i.e., the whole island), evidenced by decreasing differences between traditional and directional alpha diversity. Communities became overall phylogenetically clustered and functionally overdispersed. Biodiversity's priority effects were pervasive, with less diverse communities showing positive and more diverse communities showing negative biodiversity changes. Finally, at the local scale, different economic and environmental indicators showed complex and divergent effects across habitat clusters and biodiversity components. These effects were only partially ameliorated within a newly established Ecological Function Conservation Area in the mountainous central part of the island. Thus, our results depict complex effects of economic development on different biodiversity dimensions in different areas of the island with different land uses and protection regimes, and between local and regional spatial scales. Profound ecosystem damage associated with economic development was partially averted, probably due to enhanced biodiversity conservation policies and law enforcement, yet at the cost of regional-scale biotic homogenization and local-scale biodiversity loss. This article is protected by copyright. All rights reserved.

Taxonomic, Phylogenetic and Functional Diversity of Bird Assemblages in Urban Green Spaces: Null Model Analyses, Temporal Variation and Ecological Drivers

Urban expansion is a pervasive driver of biodiversity loss. To understand the effects of urbanization on diversity, we investigated the response of bird taxonomic, phylogenetic, and functional diversity to urban green spaces’ characteristics in thirty-one green spaces of Mexico City. Selected sites encompassed variation of environmental factors along a transformation gradient, from natural protected areas to landscaped parks. Bird observations were conducted during winter (non-breeding season), spring (dry breeding season), and summer (wet breeding season). We used multi-model inference to assess the relationship of green space area, shape, isolation, tree richness, habitat diversity, and vegetation cover with species richness, Faith’s phylogenetic diversity, and functional richness. We calculated standardized effect sizes from null models to assess phylogenetic and functional structure. We registered 91 species belonging to 28 families across all sites and seasons. The number of detected species was largest in winter and decreased toward the dry breeding season, and then toward the wet breeding season. We found a moderate to strong positive relationship of species richness with phylogenetic diversity and functional richness. Overall, phylogenetic and functional structure of bird communities in green spaces was neither clustered nor over-dispersed. However, few cases of functional clustering, phylogenetic clustering, or both were observed, and they corresponded to natural protected areas. Results showed a predominant role of green space area in determining community diversity and phylogenetic structure while it did not influence functional structure. Contrary to our predictions, habitat diversity had a negative effect on species richness and phylogenetic diversity and this effect was detected only during the wet breeding season, whereas isolation showed a positive relationship with phylogenetic and functional structure, during the wet breeding season and winter, respectively. This study emphasizes the use of complementary measures of diversity together with the comparison between observed and expected values to get a better insight into the mechanisms by which green spaces’ characteristics affect bird diversity across the seasons.