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Contrasting drivers of diversity in hosts and parasites across the tropical Andes.

ABSTRACT: Geographic turnover in community composition is created and maintained by eco-evolutionary forces that limit the ranges of species. One such force may be antagonistic interactions among hosts and parasites, but its general importance is unknown. Understanding the processes that underpin turnover requires distinguishing the contributions of key abiotic and biotic drivers over a range of spatial and temporal scales. Here, we address these challenges using flexible, nonlinear models to identify the factors that underlie richness (alpha diversity) and turnover (beta diversity) patterns of interacting host and parasite communities in a global biodiversity hot spot. We sampled 18 communities in the Peruvian Andes, encompassing ∼1,350 bird species and ∼400 hemosporidian parasite lineages, and spanning broad ranges of elevation, climate, primary productivity, and species richness. Turnover in both parasite and host communities was most strongly predicted by variation in precipitation, but secondary predictors differed between parasites and hosts, and between contemporary and phylogenetic timescales. Host communities shaped parasite diversity patterns, but there was little evidence for reciprocal effects. The results for parasite communities contradicted the prevailing view that biotic interactions filter communities at local scales while environmental filtering and dispersal barriers shape regional communities. Rather, subtle differences in precipitation had strong, fine-scale effects on parasite turnover while host-community effects only manifested at broad scales. We used these models to map bird and parasite turnover onto the ecological gradients of the Andean landscape, illustrating beta-diversity hot spots and their mechanistic underpinnings.

SUBMITTER: McNew SM

PROVIDER: S-EPMC8000519 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Environmental and anthropogenic factors are known to drive fish community structure in aquatic systems across the world. This study investigates fish assemblages in lower order streams across contrasting landscapes in central and eastern India. We documented the species diversity of these monsoon driven lower order streams in the two regions. We also investigated the potential common environmental drivers of richness and diversity and effect of season in these tropical streams. The study was based on seasonal data on abundance of fishes and environmental parameters collected between 2015-2017 from streams in states of Madhya Pradesh and West Bengal. Species diversity were compared across regions and seasons, based on their richness (SR) as well as diversity (Shannon index H'). Drivers of overall richness and diversity were analyzed using multiple linear regression methods, based on best subset selection. Analysis of data revealed high diversity in these streams in both regions. Cyprinidae, Bagridae and Channidae were the most dominant families in both regions. Despite the geographical and local ecological differences across the regions, common environmental parameters were found to influence richness and diversity across the two regions, indicating these as being key drivers of fish community structure. Water flow was a common factor driving both richness and diversity across both regions. Our study revealed a lack of seasonal effect in structuring fish communities in tropical streams. With stream and river ecosystems facing increasing threats due to habitat alterations and water quality degradation in countries such as India, a clear understanding of regional and local drivers of community structure of aquatic fauna is crucial. These results on the role of common environmental factors across ecoregions provides baseline information for understanding their ecological roles and developing management plans for important river basins and fish conservation in future.

Project description:AimWe sought to determine the relationship of forest composition and alpha diversity (the species diversity of a local assemblage) to altitude, soil, and spatial factors over a 440-2,950 m a.s.l gradient.LocationAltitudinal gradient on the Caribbean slope of the Talamanca Cordillera, Costa Rica.TaxonAngiosperm and gymnosperm trees, palms, and tree ferns.MethodsWe measured and identified all stems ≥10 cm dbh in 32 0.25-ha undisturbed rain forest plots over the gradient. We determined compositional patterns using Non-Metric Multidimensional Scaling (NMS) ordination, and used linear regressions to explore the relationship between four alpha diversity metrics and altitude. With variation partitioning (VARPART), we determined the compositional variation explained by altitude, soil, and spatial variables quantified using Principle Components of Neighbor matrices.ResultsWe identified 425 species. NMS axis 1 separated a lowland zone (440-1,120 m asl) from a transitional one dominated by holarctic Oreomunnea mexicana (1,400-1,600 m asl) and Quercus-dominated forests at altitudes >2,100 m asl. The lowland zone was separated into two clusters of plots on NMS axis 2, the first in the 430-620 m asl range and the second at 1,000-1,120 masl. Regressions showed that all alpha diversity metrics were strongly negatively related to altitude (R 2 > 0.78). Overall, adjusted R 2 from VARPART was 0.43, with 0.30, 0.21, and 0.17 for altitude, soil, and space respectively. The respective adjusted R 2 of individual matrices, on controlling for the other two, was 0.06, 0.05 and 0.09 (p < 0.001).Main conclusionsThere are two well-defined forest compositional zones on this gradient-lowlands 430-1,120 m asl and montane forests >2,150 m asl-with a transitional zone at 1,400-1,600 m asl, where lowland tropical and montane holarctic species are found together. Montane forests are very distinct in their composition and low alpha diversity. Vegetation and soil respond to altitude, and therefore temperature, as an integrated system, a model that goes beyond niche assembly as shown by the significant effect of space in the VARPART.

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Contrasting drivers of diversity in hosts and parasites across the tropical Andes.

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