Center for Ecological Sciences

Mixed-species bird flocks are attractive models for the investigation of geographical variation in animal communities, as they represent a subset of the avifauna in most forested regions of the world. Yet studies of the regional variation in flock size and the composition of flocks are few, due to the predominance of studies carried out at single study site. Here, we review nine studies of mixed-species flocks conducted at 16 sites along the Western Ghats in India and in Sri Lanka. We find that flock size varies as much within this region as it does globally, with observation time being a confounding variable. Flock composition, however, is predictably related to elevation. Flocks at high elevations (>1200 m) in the Western Ghats strongly resemble flocks at high elevations in the mountain ranges of Sri Lanka in their composition, especially at the family level. We compare these flocks to flocks of other regions and make recommendations on study methodology that can facilitate comparisons across studies.

Occurrence and abundance of mammals were compared in five large protected rainforest patches inside the Indira Gandhi Wildlife Sanctuary and in four smaller, unprotected rainforest fragments in a plantation matrix in the Anamalai hills, southern Western Ghats using line transect distance sampling. Among the 28 mammal species found in contiguous protected rainforests, 24 persisted in unprotected fragments. For most species, population densities were similar between the two strata. Density of arboreal mammal species showed varying habitat correlates across the sites sampled; Indian giant squirrel density was negatively correlated to canopy overlap, lion-tailed macaque density negatively and Nilgiri langur positively to rainforest tree density respectively. Persistence of most mammals on private lands in a fragmented landscape may be attributed to proximity to the surrounding large tract of reserved forest areas as well as recent conservation efforts, including reduction of hunting and protection of fragments. Comparison with past estimates suggests that arboreal mammals have persisted and increased in abundance over the last decade, particularly in private fragments, possibly due to multiple factors, including the ability of the species to use matrix habitats, low hunting pressure, lack of predators and higher food availability.

antipredator vigilance foraging leadership meta-analysis mixed-species flock pairwise comparative method Mixed-species flocks of foraging birds have been documented from terrestrial habitats all over the world and are thought to form for either improved feeding efficiency or better protection from predators. Two kinds of flock participants are recognized: those that join other species ('followers') and are therefore likely to be the recipients of the benefits of flock participation and those that are joined ('leaders'). Through comparative analyses, using a large sample of flocks from around the world, we show that (1) 'followers' tend to be smaller, more insectivorous, and feed in higher strata than matched species that participate in flocks to a lesser extent and (2) 'leaders' tend to be cooperative breeders more often than matched species that are not known to lead flocks. Furthermore, meta-analyses of published results from across the world showed that bird species in terrestrial mixed-species flocks increase foraging rates and reduce vigilance compared to when they are solitary or in conspecific groups. Moreover, the increase in foraging rates is seen only with flock followers and not flock leaders. These findings suggest a role for predation in the evolution of mixed-species flocking. Species that are vulnerable to predation follow species whose vigilance they can exploit. By doing so, they are able to reduce their own vigilance and forage at higher rates. Ó

The effect of fragmentation on different life forms within tropical forest plant communities is poorly understood. We studied the effect of degree of fragmentation and surrounding matrix on trees, lianas, shrubs and epiphytes in tropical forest fragments of Kodagu, Western Ghats, India. These fragments exist as sacred groves amidst a highly modified agricultural landscape, and have been preserved by the religious sentiments of local communities. Plants were sampled at two sites in continuous forests and 11 forest fragments. A total of 122 species of trees, 29 species of lianas, 60 species of shrubs and 66 species of epiphytes were recorded. Trees exhibited a significant species-area relationship (R 2 = 0.74). Richness estimates after controlling for stem density (rarefaction) revealed that observed species-area relationship was not an artefact of passive sampling. Variation in species richness of the other three groups was explained by stem density and structural diversity. Linear distance from the reserve forest did not explain any variation in species richness. All life forms exhibited significant nested pattern. Trees were nested along the area gradient while nestedness in the other three groups showed evidence in support of habitat nestedness. The four life forms thus responded variably to degree of fragmentation. Our study revealed that 74% of the regional diversity for trees was contributed by diversity among plots, highlighting the importance of inter-patch habitat diversity in maintaining the total regional species pool. We conclude that trees alone cannot serve as good indicator for taking appropriate conservation measures to mitigate species loss resulting from habitat fragmentation.

Mucuna laticifera, a new species of Fabaceae from Sikkim state of India is described and illustrated here. It can be distinguished from its closely related species by the presence of a watery latex, uniformly green to pale yellow corolla, glabrous standard and wings and parallel pod margins.

Question: What are the relative roles of environmental and spatial factors in influencing variation in species composition of tropical woody plants at different spatial scales? Location: Tropical evergreen forests, Western Ghats, South India. Methods: Using a plot-based species inventory spanning the entire latitudinal extent (1,200 km) of the Western Ghats' wet evergreen forests, we collected primary data on spatial variation in species composition of woody plants. Each plot was characterized by a set of environmental descriptors consisting of topographic, edaphic and climatic variables, while eigenvector-based spatial variables and plot coordinates were used as spatial descriptors. We used ordination-based as well as distance-based variation partitioning techniques to partition the variation in species composition into components uniquely and jointly explained by environmental and spatial factors. Results: The compositional similarity of woody plants largely showed a linear decline with log-geographic distance. However, this relationship was spatially structured. After controlling for the differences in environment, compositional similarity was found to be strongly associated with geographic distance only at the smallest spatial scale. Variation partitioning analysis revealed that environmental variables explained a much larger proportion of variation in species composition overall compared to spatial variables. Among environmental variables, climatic variables emerged as the most important predictors of variation in species composition at regional and landscape scales. Conclusions: Strong association between compositional similarity and geographic distance at local scales indicates the influence of dispersal limitation, while niche differentiation seems to be a more important driver of variation in species composition at larger spatial scales. Overall, our results provide evidence for scale-dependent shifts in the relative importance of factors that are responsible for variation in species composition.

Narcondam Hornbill is a point endemic hornbill species restricted to the Narcondam Island (area: 6.8 sq. km) in the Andaman Sea, India. It has been classified as a Schedule 1 species in the Wildlife Protection Act (1972). The estimated population of the Narcondam Hornbill is 1026 (95% CI: 751 – 1402) birds and the population density of the hornbills is 151 hornbills per sq. km, which is among the highest reported hornbill densities in the world (Naniwadekar et al. 2020). Like other hornbills, Narcondam Hornbills nest in secondary tree cavities (Hussain, 1984; Kemp, 1995). No woodpeckers or barbets have been reported from Narcondam Island (Raman et al. 2013), so the secondary cavities on trees are likely formed because of branch break-offs may be due to storms and/ or wood rot.

Gleadovia ruborum Gamble & Prain (Orobanchaceae), a rare root parasite is recorded after a gap of 57 years from a new locality in Uttarakhand, western Himalaya.  A total of four individuals were located in a shady moist forest of Abies pindrow-Quercus floribunda at Surkanda hill near Mussoorie.  All the individual plants were growing on the roots of Rubus pedunculosus D. Don.  The current communication provides an updated description, habitat characteristics and host species of Gleadovia ruborum.

The high species richness of tropical forests has long been recognized, yet there remains substantial uncertainty regarding the actual number of tropical tree species. Using a pantropical tree inventory database from closed canopy forests, consisting of 657,630 trees belonging to 11,371 species, we use a fitted value of…

Within Magnoliales, Annonaceae is the most species-rich family (Chatrou et al. 2012). Miliusa Leschenault ex De Candolle (1832: 213) is placed in tribe Miliusae, subfamily Malmeoideae, according to the recent infrafamilial classification (Chatrou et al. 2012). Chaowasku et al. (2014) provided insights into the evolutionary relationships of tribe Miliusae, and Chaowasku & Keßler (2013) reconstructed the phylogeny of Miliusa with four well-supported clades. Miliusa is distributed across the Austro-Malesian region with most species exhibiting a restricted distribution to certain areas (Mols & Kessler 2003). Species known from India exhibit a high degree of endemism (Kundu 2006).

The present communication reports an update on the distribution of three endemic tree species of the Western Ghats-Sri Lanka biodiversity hotspot, namely, Atuna indica (Bedd.) Kosterm., Paracroton integrifolius (Airy Shaw) N.P.Balakr. & Chakrab. and Phaeanthus malabaricus Bedd.  The discovery of these taxa in the Makutta Ghat of Kodagu District results in the extension of their northern range limits and further enriches the flora of Karnataka state by three more tree species.  Within the Western Ghats, these taxa were previously recorded only from the states of Kerala and Tamil Nadu, while Paracroton integrifolius (Airy Shaw) N.P.Balakr. & Chakrab. has also been recorded from Sri Lanka.  Nomenclature updates, detailed descriptions, conservation status and relevant notes on the habitat, phenology and distribution localization are supplied.  Additionally, field photographs and scanned herbarium specimens are provided to facilitate easy identification of these taxa in the field. 

Dipterocarpus bourdillonii, a Critically Endangered tree species endemic to the Western Ghats, India, has hitherto been reported mainly from the states of Kerala and Karnataka on the western slopes of the mountain range. In Tamil Nadu, this species has been reported to occur in two locations, but no population details have been documented and the species has neither been listed in state floras nor in a recent compendium of plant species. The present study documents the occurrence of a population of the species, with at least 40 individuals, in the Anamalai Tiger Reserve, Tamil Nadu, extends the known upper limit of its altitudinal range to 733 m, and suggests further surveys and in situ conservation efforts. 

The Western Ghats (WG) mountain chain is a global biodiversity hotspot with high diversity and endemicity of woody plants. The latitudinal breadth of the WG offers an opportunity to determine the evolutionary drivers of latitudinal diversity patterns. We examined the spatial patterns of evolutionary diversity using complementary phylogenetic diversity and endemism measures. To examine if different regions of the WG serve as a museum or cradle of evolutionary diversity, we examined the distribution of 470 species based on distribution modelling and occurrence locations across the entire region. In accordance with the expectation, we found that the southern WG is both a museum and cradle of woody plant evolutionary diversity, as a higher proportion of both old and young evolutionary lineages are restricted to the southern WG. The diversity gradient is likely driven by high geo-climatic stability in the south and phylogenetic niche conservatism for moist and aseasonal sites. This is co...

The genus Meiogyne is distributed throughout South and Southeast Asia and includes approximately 33 described taxa. A new species, Meiogyne arunachalensis, is here described from the state of Arunachal Pradesh, India. This is the third species from India and the first from the Eastern Himalayan and Northeast Indian region. This species shows morphological similarity with Meiogyne maxiflora, a species distributed in Thailand, but it differs in a number of vegetative and reproductive characters. Meiogyne arunachalensis is the largest species of the genus described so far in terms of tree height and girth of the tree trunk. Detailed colour photographs are provided to highlight its morphological distinctness and facilitate identification in the field.

Oceanic islands, due to their evolutionary history and isolation, hold a disproportionately high proportion of endemic species. However, their evolutionary history also makes them vulnerable to extinctions, with most known extinctions occurring on islands. Plant-animal interactions are particularly important on islands, as island systems generally have low redundancy and are more vulnerable to disruption either via extinction or by invasive species. Here, we examined the fruit removal and seed predation of a keystone palm, Caryota mitis, on the remote oceanic island of Narcondam. The island endemic Narcondam hornbill (Rhyticeros narcondami), was the sole seed disperser of the Caryota mitis (90 hours; N = 15 trees), indicating a lack of redundancy in seed dispersal of the palm on this island. While the invasive rodent, Rattus cf. tiomanicus was the sole predator of the Caryota mitis seeds in the forest (N = 15 individual fruiting palms, 416 trap nights). Overall, 17.1% of the seeds placed (N = 375 seeds) were removed. Seeds placed under and away from the canopy, and at different densities (2 plots with 10 seeds each; 1 plot with 5 seeds, respectively), showed similar removal rates. This is indicative of ambient seed predation and the lack of safe sites for the regeneration of Caryota mitis, with potential deleterious effects on the subsequent stages of the "seed dispersal cycle". Here, from a data deficient site, we provide baseline information on the plant-frugivore interaction of a keystone palm and the potential impacts by an invasive rodent.

The Western Ghats (WG) mountain chain is a global biodiversity hotspot with high diversity and endemicity of woody plants. The latitudinal breadth of the WG offers an opportunity to determine the evolutionary drivers of latitudinal diversity patterns. We examined the spatial patterns of evolutionary diversity using complementary phylogenetic diversity and endemism measures. To examine if different regions of the WG serve as a museum or cradle of evolutionary diversity, we modelled the distribution of 470 woody plant species across the entire region.In accordance with the expectation, we found that the southern WG is both a museum and cradle of woody plant evolutionary diversity, as both old and young evolutionary lineages are restricted to the southern WG. The diversity gradient is likely driven by high geo-climatic stability in the south and phylogenetic niche conservatism for moist and aseasonal sites. This is corroborated by persistent lineage nestedness at almost all evolutionary depths (10-135 million years), and a strong correlation of evolutionary diversity with drought seasonality, precipitation and elevation. Our results highlight the global value of the WG, demonstrating, in particular, the importance of protecting the southern WG-an engine of plant diversification and persistence.

A new species of Salacia is described from Karnataka and Kerala states of the Western Ghats, India. It is unique within the genus on account of its obliquely dehiscing anthers and 7-10 cm long, prolate to broadly ellipsoid or ovoid, keeled, greenish-yellow 5-to 8-seeded fruit with thin epicarp and dry mesocarp. Salacia megacarpa sp. nov. can be grouped with S. fruticosa Heyne ex M.A.Lawson and S. oblonga Wight & Arn. which are the only other species from the sub-continent which exhibit axillary, ramiflorous, dichotomously branched cymes.