Navendu Page | Indian Institute of Science (original) (raw)

Papers by Navendu Page

Journal of Threatened Taxa, Sep 26, 2016

for facilities and encouragement. The Range Forest Officer, Brahmagiri Wildlife Sanctuary, Kodagu... more for facilities and encouragement. The Range Forest Officer, Brahmagiri Wildlife Sanctuary, Kodagu is acknowledged for help in carrying out field explorations in Makutta Ghat forest. The second author is grateful to Rufford small grant foundation (RSGF 10801-1) and Conservation Leadership Program (03190414) for supporting field work. Authors acknowledge with thanks the technical help provided by Dr. Raja K. Swamy.

Biotropica, Jun 26, 2021

Plant–seed disperser interactions are critical for maintaining tropical plant diversity. However,... more Plant–seed disperser interactions are critical for maintaining tropical plant diversity. However, these interactions are altered by habitat fragmentation, a pervasive threat to the tropics globally. We compared vegetation structure, richness and composition of plant–avian seed disperser interactions across two forest fragments (area: ~25 km2), and one contiguous forest site in the last remaining lowland tropical forests in north‐east India. We used network‐level indices (nestedness, generality, and vulnerability) and species‐level indices (degree and species strength) to identify key plant and bird groups across the three sites. We found that the three sites varied in habitat structure and were more similar in the composition of avian seed dispersers than plants. The low similarity in plant‐seed disperser interactions between the three sites was likely influenced by low similarity in fruiting plants. The fragmented sites exhibited fewer pairwise interactions and were characterized by a higher representation of small‐seeded plants, climbers, and open‐forest birds. Small‐bodied birds (bulbuls and barbets) played a central role in all the seed dispersal networks, while large‐bodied birds (hornbills) performed persistent interactions with large‐seeded plants at all sites. This is one of the first studies from the Asian tropics to investigate the differences in the plant–avian seed disperser communities between forest fragments and contiguous forest. Our findings highlight the conservation value of fragments given their potential to hold a distinct set of plant–seed disperser interactions, thereby maintaining functional diversity in fragmented tropical landscapes.Abstract in Hindi is available with online material.

Journal of Threatened Taxa, Mar 26, 2015

Range extension of Orophea malabarica and O. sivarajanii Sankararao et al.

Phytotaxa, Jan 22, 2016

Within Magnoliales, Annonaceae is the most species-rich family (Chatrou et al. 2012). Miliusa Les... more 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). Hooker & Thomson (1855), Hooker (1872), King (1893) and Gamble (1915) included the genus in their respective taxonomic studies of the flora of British India. Mitra (1993) enumerated 14 species of this genus from India (of which almost half are endemic) showing a disjunct distribution across the country with most species being restricted to northeast India, the Andaman Islands or the Western Ghats. Only two species [

PLOS ONE, Jul 16, 2020

Understanding the determinants of range location and size is fundamental to our understanding of ... more Understanding the determinants of range location and size is fundamental to our understanding of spatial patterns in species richness. Here, we aimed to test the role of 'climatic stability' in determining latitudinal trends in range size and as a consequence on species richness of tropical woody plants. Using primary data from 156 (0.06 ha) plots comprising 20,400 occurrences of more than 400 species of tropical woody plants, we built a biomewide species database that covers the entire latitudinal extent of the wet-evergreen forests of the Western Ghats (8 o to 20 o N), India. We consolidated this database using secondary data from other published species inventories. We then calculated the range sizes and climatic niche width of woody plants to test the predictions of the climatic stability hypothesis and examined the relationship between range position and climatic tolerance of species. Our results show a significant latitudinal gradient in species richness and turnover where local and regional species richness increase monotonically from higher latitudes to lower latitudes of the Western Ghats. We found strong support for Rapoport's Rule with an increase in range size from lower to higher latitudes; our results are consistent with the predictions of the climatic stability hypothesis, where species at higher latitudes exhibited greater tolerance to temperature and rainfall seasonality. Contrary to earlier work, our findings suggest that Rapoport's Rule and the climatic stability hypothesis can operate over regional scales, and even at lower latitudes. We suggest that latitude associated climatic seasonality through its influence on species ranges, can influence latitudinal patterns in species turnover as well as species richness.

Journal of Vegetation Science, Nov 29, 2017

Question: What are the relative roles of environmental and spatial factors in influencing variati... more 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.

Journal of Threatened Taxa, Aug 26, 2022

Dipterocarpus bourdillonii, a Critically Endangered tree species endemic to the Western Ghats, In... more 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.

Nordic Journal of Botany, Apr 1, 2020

A new species of Salacia is described from Karnataka and Kerala states of the Western Ghats, Indi... more 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.

Proceedings of The Royal Society B: Biological Sciences, Apr 26, 2023

The Western Ghats (WG) mountain chain is a global biodiversity hotspot with high diversity and en... more 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 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 topographic heterogeneity. 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.

bioRxiv (Cold Spring Harbor Laboratory), Dec 14, 2022

The Western Ghats (WG) mountain chain is a global biodiversity hotspot with high diversity and en... more 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.

Global Ecology and Biogeography, Jul 6, 2021

American Journal of Botany, Mar 21, 2021

PremiseThe woody plant group Memecylon (Melastomataceae) is a large clade occupying diverse fores... more PremiseThe woody plant group Memecylon (Melastomataceae) is a large clade occupying diverse forest habitats in the Old World tropics and exhibiting high regional endemism. Its phylogenetic relationships have been previously studied using ribosomal DNA with extensive sampling from Africa and Madagascar. However, divergence times, biogeography, and character evolution of Memecylon remain uninvestigated. We present a phylogenomic analysis of Memecylon to provide a broad evolutionary perspective of this clade.MethodsOne hundred supercontigs of 67 Memecylon taxa were harvested from target enrichment. The data were subjected to coalescent and concatenated phylogenetic analyses. A timeline was provided for Memecylon evolution using fossils and secondary calibration. The calibrated Memecylon phylogeny was used to elucidate its biogeography and ancestral character states.ResultsRelationships recovered by the phylogenomic analyses are strongly supported in both maximum likelihood and coalescent‐based species trees. Memecylon is inferred to have originated in Africa in the Eocene and subsequently dispersed predominantly eastward via long‐distance dispersal (LDD), although a reverse dispersal from South Asia westward to the Seychelles was postulated. Morphological data exhibited high levels of homoplasy, but also showed that several vegetative and reproductive characters were phylogenetically informative.ConclusionsThe current distribution of Memecylon appears to be the result of multiple ancestral LDD events. Our results demonstrate the importance of the combined effect of geographic and paleoclimatic factors in shaping the distribution of this group in the Old World tropics. Memecylon includes a number of evolutionarily derived morphological features that contribute to diversity within the clade.

Environmental Conservation

SummaryGrassland habitats currently face severe anthropogenic exploitation, thereby affecting the... more SummaryGrassland habitats currently face severe anthropogenic exploitation, thereby affecting the survival of grassland-dependent biodiversity globally. The biodiversity-rich grasslands of India lack quantitative spatiotemporal information on their status. We evaluated the status of upper Gangetic Plains grasslands in 2015 and compared it with those from 1985, 1995 and 2005. On-ground mapping and visual classifications revealed a 57% decline in these grasslands between 1985 (418 km2) and 2015 (178 km2), mostly driven by habitat conversion (74% contribution by cropland). Limited radiotelemetry data from endemic swamp deer indicated a possible grassland-dominated average home range size of 1.02 km2, and these patches were highly preferred (average Ivlev’s index = 0.85) over other land-use classes at both spatial and temporal scales. Camera-trapping within the core habitats suggests the critical use of these patches as fawning/breeding grounds. Habitat suitability analysis indicates on...

bioRxiv (Cold Spring Harbor Laboratory), Apr 7, 2023

Oceanic islands, due to their evolutionary history and isolation, hold a disproportionately high ... more 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.

Proceedings of the National Academy of Sciences, 2015

Edinburgh Journal of Botany

The genus Meiogyne is distributed throughout South and Southeast Asia and includes approximately ... more 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.

The Western Ghats (WG) mountain chain is a global biodiversity hotspot with high diversity and en... more 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...

Journal of Threatened Taxa, Sep 26, 2016

for facilities and encouragement. The Range Forest Officer, Brahmagiri Wildlife Sanctuary, Kodagu... more for facilities and encouragement. The Range Forest Officer, Brahmagiri Wildlife Sanctuary, Kodagu is acknowledged for help in carrying out field explorations in Makutta Ghat forest. The second author is grateful to Rufford small grant foundation (RSGF 10801-1) and Conservation Leadership Program (03190414) for supporting field work. Authors acknowledge with thanks the technical help provided by Dr. Raja K. Swamy.

Biotropica, Jun 26, 2021

Plant–seed disperser interactions are critical for maintaining tropical plant diversity. However,... more Plant–seed disperser interactions are critical for maintaining tropical plant diversity. However, these interactions are altered by habitat fragmentation, a pervasive threat to the tropics globally. We compared vegetation structure, richness and composition of plant–avian seed disperser interactions across two forest fragments (area: ~25 km2), and one contiguous forest site in the last remaining lowland tropical forests in north‐east India. We used network‐level indices (nestedness, generality, and vulnerability) and species‐level indices (degree and species strength) to identify key plant and bird groups across the three sites. We found that the three sites varied in habitat structure and were more similar in the composition of avian seed dispersers than plants. The low similarity in plant‐seed disperser interactions between the three sites was likely influenced by low similarity in fruiting plants. The fragmented sites exhibited fewer pairwise interactions and were characterized by a higher representation of small‐seeded plants, climbers, and open‐forest birds. Small‐bodied birds (bulbuls and barbets) played a central role in all the seed dispersal networks, while large‐bodied birds (hornbills) performed persistent interactions with large‐seeded plants at all sites. This is one of the first studies from the Asian tropics to investigate the differences in the plant–avian seed disperser communities between forest fragments and contiguous forest. Our findings highlight the conservation value of fragments given their potential to hold a distinct set of plant–seed disperser interactions, thereby maintaining functional diversity in fragmented tropical landscapes.Abstract in Hindi is available with online material.

Journal of Threatened Taxa, Mar 26, 2015

Range extension of Orophea malabarica and O. sivarajanii Sankararao et al.

Phytotaxa, Jan 22, 2016

Within Magnoliales, Annonaceae is the most species-rich family (Chatrou et al. 2012). Miliusa Les... more 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). Hooker & Thomson (1855), Hooker (1872), King (1893) and Gamble (1915) included the genus in their respective taxonomic studies of the flora of British India. Mitra (1993) enumerated 14 species of this genus from India (of which almost half are endemic) showing a disjunct distribution across the country with most species being restricted to northeast India, the Andaman Islands or the Western Ghats. Only two species [

PLOS ONE, Jul 16, 2020

Understanding the determinants of range location and size is fundamental to our understanding of ... more Understanding the determinants of range location and size is fundamental to our understanding of spatial patterns in species richness. Here, we aimed to test the role of 'climatic stability' in determining latitudinal trends in range size and as a consequence on species richness of tropical woody plants. Using primary data from 156 (0.06 ha) plots comprising 20,400 occurrences of more than 400 species of tropical woody plants, we built a biomewide species database that covers the entire latitudinal extent of the wet-evergreen forests of the Western Ghats (8 o to 20 o N), India. We consolidated this database using secondary data from other published species inventories. We then calculated the range sizes and climatic niche width of woody plants to test the predictions of the climatic stability hypothesis and examined the relationship between range position and climatic tolerance of species. Our results show a significant latitudinal gradient in species richness and turnover where local and regional species richness increase monotonically from higher latitudes to lower latitudes of the Western Ghats. We found strong support for Rapoport's Rule with an increase in range size from lower to higher latitudes; our results are consistent with the predictions of the climatic stability hypothesis, where species at higher latitudes exhibited greater tolerance to temperature and rainfall seasonality. Contrary to earlier work, our findings suggest that Rapoport's Rule and the climatic stability hypothesis can operate over regional scales, and even at lower latitudes. We suggest that latitude associated climatic seasonality through its influence on species ranges, can influence latitudinal patterns in species turnover as well as species richness.

Journal of Vegetation Science, Nov 29, 2017

Question: What are the relative roles of environmental and spatial factors in influencing variati... more 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.

Journal of Threatened Taxa, Aug 26, 2022

Dipterocarpus bourdillonii, a Critically Endangered tree species endemic to the Western Ghats, In... more 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.

Nordic Journal of Botany, Apr 1, 2020

A new species of Salacia is described from Karnataka and Kerala states of the Western Ghats, Indi... more 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.

Proceedings of The Royal Society B: Biological Sciences, Apr 26, 2023

The Western Ghats (WG) mountain chain is a global biodiversity hotspot with high diversity and en... more 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 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 topographic heterogeneity. 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.

bioRxiv (Cold Spring Harbor Laboratory), Dec 14, 2022

The Western Ghats (WG) mountain chain is a global biodiversity hotspot with high diversity and en... more 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.

Global Ecology and Biogeography, Jul 6, 2021

American Journal of Botany, Mar 21, 2021

PremiseThe woody plant group Memecylon (Melastomataceae) is a large clade occupying diverse fores... more PremiseThe woody plant group Memecylon (Melastomataceae) is a large clade occupying diverse forest habitats in the Old World tropics and exhibiting high regional endemism. Its phylogenetic relationships have been previously studied using ribosomal DNA with extensive sampling from Africa and Madagascar. However, divergence times, biogeography, and character evolution of Memecylon remain uninvestigated. We present a phylogenomic analysis of Memecylon to provide a broad evolutionary perspective of this clade.MethodsOne hundred supercontigs of 67 Memecylon taxa were harvested from target enrichment. The data were subjected to coalescent and concatenated phylogenetic analyses. A timeline was provided for Memecylon evolution using fossils and secondary calibration. The calibrated Memecylon phylogeny was used to elucidate its biogeography and ancestral character states.ResultsRelationships recovered by the phylogenomic analyses are strongly supported in both maximum likelihood and coalescent‐based species trees. Memecylon is inferred to have originated in Africa in the Eocene and subsequently dispersed predominantly eastward via long‐distance dispersal (LDD), although a reverse dispersal from South Asia westward to the Seychelles was postulated. Morphological data exhibited high levels of homoplasy, but also showed that several vegetative and reproductive characters were phylogenetically informative.ConclusionsThe current distribution of Memecylon appears to be the result of multiple ancestral LDD events. Our results demonstrate the importance of the combined effect of geographic and paleoclimatic factors in shaping the distribution of this group in the Old World tropics. Memecylon includes a number of evolutionarily derived morphological features that contribute to diversity within the clade.

Environmental Conservation

SummaryGrassland habitats currently face severe anthropogenic exploitation, thereby affecting the... more SummaryGrassland habitats currently face severe anthropogenic exploitation, thereby affecting the survival of grassland-dependent biodiversity globally. The biodiversity-rich grasslands of India lack quantitative spatiotemporal information on their status. We evaluated the status of upper Gangetic Plains grasslands in 2015 and compared it with those from 1985, 1995 and 2005. On-ground mapping and visual classifications revealed a 57% decline in these grasslands between 1985 (418 km2) and 2015 (178 km2), mostly driven by habitat conversion (74% contribution by cropland). Limited radiotelemetry data from endemic swamp deer indicated a possible grassland-dominated average home range size of 1.02 km2, and these patches were highly preferred (average Ivlev’s index = 0.85) over other land-use classes at both spatial and temporal scales. Camera-trapping within the core habitats suggests the critical use of these patches as fawning/breeding grounds. Habitat suitability analysis indicates on...

bioRxiv (Cold Spring Harbor Laboratory), Apr 7, 2023

Oceanic islands, due to their evolutionary history and isolation, hold a disproportionately high ... more 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.

Proceedings of the National Academy of Sciences, 2015

Edinburgh Journal of Botany

The genus Meiogyne is distributed throughout South and Southeast Asia and includes approximately ... more 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.

The Western Ghats (WG) mountain chain is a global biodiversity hotspot with high diversity and en... more 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...