Estimating species richness in large biomes is a central challenge in ecology and conservation biology. However, accurate census data is often available only from small discrete plots distributed within the biome. Using tree species richness data collected from 48 plots (0.25 ha each) widely distributed through 60 000 km 2 in the rainforests of the Western Ghats of southern India, we test the application of a proposed method for estimating species richness at large scales from measured species commonalities between pairs of censused plots. We show that the method allows extrapolation of species richness from a scale of 0.25 ha plots to that of the entire biome, or 10 5 km 2 .
R. Krishnamani
Aim
How seasonal drought influences tree species distributions might shape future vegetation composition with impending changes to rainfall patterns. Theory suggests that across a seasonal drought gradient, dry‐tolerant species might have wider distributions than species sensitive to seasonal drought, which will be restricted to less seasonal conditions. As wet‐associated species drop out with increasing seasonality, the community will contain mainly dry‐tolerant species.
Time period
Present.
Location
Western Ghats Biodiversity Hotspot in peninsular India.
Major taxa studied
Woody angiosperms.
Methods
Across a 1,200 km seasonal drought gradient, we modelled occurrences of 183 species using Gaussian logistic regression in a hierarchical Bayesian framework. We used the first‐order model coefficients to attribute the association of species to seasonality (dry/wet) and second‐order coefficients to assess modal responses. For 92 species, we checked for an interaction between dry/wet association and two traits: wood density and specific leaf area (SLA). Finally, we assessed the consequences of the seasonality associations of species for regional community assembly.
Results
Of 183 species, 38% were significantly wet associated, 27% dry associated and 34% indifferent to seasonality. Nearly 80% of species had estimated modes of occurrence within the seasonality range considered here. Species with lower SLA and lower wood density were more likely to occur in more seasonal sites where dry‐associated species formed the majority of co‐occurring species. The proportion of wet‐associated species increased only after intermediate levels of seasonality. The community proportion of extreme wet‐associated species decreased prominently from less to more seasonal sites.
Main conclusions
Dry‐associated species persisted in less seasonal sites, but not vice versa. A shift toward more seasonal rainfall might favour dry‐associated species and shrink the ranges of wet‐associated species. Future work should assess how the intensity and duration of drought and interactions with other drivers of global change regulate the relative performance of species at more and less seasonal sites.
Geophagy or soil ingestion is a multidisciplinary phenomenon that has attracted the attention of many researchers in recent years; who have sought to understand why a large number of animals consume natural earths. To find out why animals ingest soils, it is of paramount importance to establish standard methods to analyze comestible soil. Researchers have used different methods to examine soils ingested by animals, often with incomplete or inconclusive results. To make meaningful comparisons among studies, it is necessary to perfect research designs and establish standard methods to evaluate and analyze geophagy in animals.
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