Elevational gradients are considered important for understanding causes behind gradients in species richness due to the large variation in climate and habitat within a small spatial extent. Geometric constraints are thought to interact with environmental variables and influence elevational patterns in species richness. However, the geographic setting of most mountain ranges, particularly continuity with low elevation areas may reduce the effect of geometric constraints at lower elevations. In the present study, we test the effects of climatic gradients and continuity with the low elevation plains of the eastern Himalayan mountain range on patterns of species richness. We studied species richness of ants (Hymenoptera: Formicidae) on an elevational gradient between 600m and 2400m in the Eastern Himalayapart of Himalaya biodiversity hotspot. Ants were sampled in nine elevational bands of 200m with four transects in each band using pitfall and Winkler traps. We used regression models to identify the most important environmental variables that predict species richness and used constrained null models to test the effects of contiguity between the mountain range and plains. We find a monotonic decline in species richness of ants with elevation. Temperature was a more important predictor of species richness than habitat complexity. Geometric constraints model weighted by temperature with a soft lower boundary and hard upper boundary best explained the species richness pattern. This suggests that a combination of climate and geometric constraints drive the elevational species richness patterns of ants.

Some fish groups are common on coral reefs, but we still lack fundamental information about how fish assemblages vary across seascapes. The order Tetraodontiformes, which includes pufferfish, triggerfish, shingles, porcupinefish, burrfish, leatherjacketfish, filefish, and trunkfish, is one such group. We systematically surveyed 75 sites around 52 islands of the Andaman and Nicobar archipelago to evaluate the occurrence and distribution of tetraodontiform fishes. We recorded 25 species from 16 genera and 6 families. We found the distribution of fishes to vary between sites and geographical regions, with the southern Nicobar region having higher species richness than other geographical regions in the island group. Possible reasons for the observed patterns of the occurrence and distribution of tetraodontiform fishes are discussed.

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Conservation of forests outside protected areas is essential for maintaining forest connectivity, which largely depends on the effectiveness of local institutions. In this study, we use Landsat data to explore the relationship between vegetation structure and forest management institutions, in order to assess the efficacy of local institutions in management of forests outside protected areas. These forests form part of an important tiger corridor in Eastern Maharashtra, India. We assessed forest condition using 450 randomly placed 10 m radius circular plots in forest patches of villages with and without local institutions, to understand the impact of these institutions on forest vegetation. Tree density and species richness were significantly different between villages with and without local forest institutions, but there was no difference in tree biomass. We also found a significant difference in the relationship between tree density and NDVI between villages with and without local forest institutions. However, the relationship between species richness and NDVI did not differ significantly. The methods proposed by this study evaluate the status of forest management in a forest corridor using remotely sensed data and could be effectively used to identify the extent of vegetation health and management status.

Diversity-environment relationships are distinct across species pools, and as a result species from different biogeographic pools have different environmental preferences. Regional communities are drawn from available biogeographic pools, subject to environmental and dispersal constraints. Does shared biogeographic history of taxa lead to similar relationships with the environment? We test this idea in the Indian subcontinent, which is at the confluence of multiple biogeographic regions resulting in species from multiple biogeographic pools being distributed here. Species were classified as belonging to four biogeographic affinities based on their geographic distributions: eastern, northern, western and endemic. We investigated spatial patterns of species richness for all mammals (over 1° x 1° grid cells), for each biogeographic group and for 5 major mammalian orders. Generalized Additive Models (GAM) were used to investigate environment-diversity relationship for all mammals, each biogeographic group, and for major mammalian orders in the Indian subcontinent. Species richness of all mammals was found to be highest in the montane regions of the Eastern Himalayas and the Western Ghats. Species richness of each biogeographic group was highest at the border it shared with Asia, in the direction of immigration from Asia. Environment and spatial variables were both correlated with species richness in the Indian subcontinent and each biogeographic group showed a distinct richness-environment relationship. Additionally, biogeographic groups sorted along environmental space, in keeping with our predictions based on their global distributions. Finally, analyses across mammalian orders had low predictive value, suggesting that shared phylogenetic history is relatively less important than biogeographic ancestry in determining relationships to environment. We conclude that historical factors such as immigration and the distinct evolutionary histories of species impact species richness patterns in the Indian subcontinent. Our results provide insights into drivers of regional community assembly in transition zones where multiple biogeographic species pools co-exist.

Beta diversity represents how species in the regional pool segregate among local communities and hence forms a link between local and regional species diversities. Therefore, the magnitude of beta diversity and its variation across geographic gradients can provide insights into mechanisms of community assembly. Along with limits on local or regional level diversities, effects of local abundance that lead to under-sampling of the regional species pool are important determinants of estimated beta diversity. We explore the effects of regional species pools, abundance distributions, and local abundance to show that patterns in beta diversity as well as the mean of species abundance distribution have distinct outcomes, depending on limits on species pools and under-sampling. We highlight the effect of under-sampling in some established relationships between gamma diversity and beta diversity using graphical methods. We then use empirical data on ant communities across an elevational gradient in the Eastern Himalayas to demonstrate a shift from effect of reduction in species pool to under-sampling at mid-elevations. Our results show that multiple processes with contrasting effects simultaneously affect patterns in beta diversity across geographic gradients.

The Vulnerable bumphead parrotfish Bolbometopon muricatum, a highly prized fishery resource worldwide, has experienced population declines throughout its geographical range. There is limited knowledge of the distribution and abundance of, and threats to, this fish in Indian waters, particularly for the Andaman and Nicobar Islands. To assess the species’ distribution and conservation status we conducted underwater surveys across 75 sites around 51 islands and interviewed 99 fishers across the Andaman and Nicobar archipelago. We recorded a total of 59 individual B. muricatum across nine sites from the northernmost island in the Andamans (Landfall Island) to the southernmost island in the Nicobars (Great Nicobar Island). Interviews revealed that most fishers (100% in Nicobar, 94% in Middle Andaman, 62% in South Andaman) had seen B. muricatum, and knowledge of the species is highest amongst spearfishers. Generalized linear models indicated that presence of marine protected areas and high live coral cover influenced the abundance and distribution of B. muricatum. The species' density seems to be naturally low in the archipelago. We discuss our findings in the light of protecting rare and threatened species, and recommend strengthening the existing marine protected areas in these islands.

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