Biology subjects

Karanth, K. P.

Publications and source records attributed to Karanth, K. P..

6 recordsLinked to original sources

bioRxiv2024

Gut feeling: host and habitat as drivers of the microbiome in blackbuck (Antilope cervicapra)

The gut microbiome can be shaped by both intrinsic host factors and extrinsic environmental factors. However, the relative importance of intrinsic and extrinsic factors in gut microbial composition has rarely been investigated, particularly for a single host across its natural range. Here, we characterise the gut microbiome of an endemic, endangered antelope, the blackbuck or Antilope cervicapra. We evaluated the influence of seven predictor variables, which were classified into intrinsic and extrinsic factors, on the gut microbiome. We determined which of these seven variables explains greater variation in the microbiome within (-diversity) and between ({beta}-diversity) the blackbuck host. We analysed the microbiome of 60 blackbuck hosts from ten different populations across India. We recorded 11800 unique OTUs across 30 known phyla and 2.9 million reads. We find an average of 2056 OTUs per individual, with firmicutes and bacteroidetes being the most dominant phyla. We find that nucleotide diversity (intrinsic), blackbuck population density (intrinsic), distance to human settlement (extrinsic), and anthropogenic land-use (extrinsic) explain within-host variation. In contrast, precipitation (extrinsic), nucleotide diversity, distance to human settlement, and anthropogenic land-use explain between-host variation. Overall, we also show that the genetic diversity of the host is more important than their environment for both within- and between-host variation in the microbiome, in blackbuck. Therefore, conservation efforts should be directed to not only preserve natural habitats but also increase the genetic pool of the blackbuck populations, which will positively impact their survival through diverse gut microbiomes.

ecology↗

bioRxiv2021

An insight into the evolutionary history of Indoplanorbis exustus (Bulinidae: Gastropoda)at the scale of population and species

The history of a lineage is intertwined with the history of the landscape it resides in. Here we showcase how the geo-tectonic and climatic evolution in South Asia and surrounding landmasses have shaped the biogeographic history of Indoplanorbis exustus, a tropical Asian, freshwater, pulmonated snail. We amplified partial COI gene fragment from all over India and combined this with a larger dataset from South and Southeast Asia to carry out phylogenetic reconstruction, species delimitation analysis, and population genetic analyses. Two nuclear genes were also amplified from one individual per putative species to carry out divergence dating and ancestral area reconstruction analyses. The results suggest that Indoplanorbis dispersed out of Africa into India during Eocene. Furthermore, molecular data suggests Indoplanorbis is a species complex consisting of multiple putative species. The primary diversification took place in Northern Indian plains or the Northeast India. The speciation events appear to be primarily allopatric caused by a series of aridification events starting from late Miocene to early Pleistocene. None of the species seemed to have any underlying genetic structure suggestive of high vagility. All the species underwent population fluctuations during the Pleistocene likely driven by the Quaternary climatic fluctuations.

evolutionary biology↗

bioRxiv2021

Cryptic speciation in freshwaters: are speciation in lentic species shaped by paleohydrological events?

The Indian subcontinent is extremely diverse in terms of its flora and fauna. However, there is a severe underestimation of the biotic diversity in invertebrate groups as well as a lack of understanding of the processes generating diversity in these groups. Here we aimed to jointly estimate the cryptic diversity of two freshwater snail species complexes - Pila globosa and Pila virens, and uncover the processes behind the speciation in these groups. We employed phylogenetic, morphometric, population genetic and niche modelling technique to address these questions. We found out that both species complexes consist of several genetically and ecologically distinct putative species. The speciation was primarily driven by allopatric isolation into different river basins. A combination of paleoclimatic and paleohydrological changes during the Miocene have shaped the speciation events. Local climatic adaptation also could have contributed towards some of the speciation events. The study sheds light on the complex interaction between the biology of the species and the environment that shape the diversification patterns in a group.

evolutionary biology↗

bioRxiv2019

Into-India or out-of-India? Historical biogeography of freshwater gastropod genus Pila (Ampullariidae)

The biota of the Indian subcontinent has assembled during various points of the history of its continental drift: some when it was still a part of Gondwanaland and subsequently dispersed out-of-India and some dispersed into-India after it collided with Asia. However, the relative contribution of these connection to the current biotic assembly of the subcontinent is still under-explored. We aimed to understand the relative importance of these various routes of biotic assembly in India through studying the historical biogeography of tropical Old World freshwater snail genus Pila. We reconstructed a near-complete phylogeny of Ampullariidae including all the described Pila species from India and published sequences of Ampullariids from all over the world from two mitochondrial and two nuclear markers. Thereafter molecular dating and ancestral area reconstruction analyses were carried out in order to ascertain the time frame and route of colonization of India. The results suggest that Pila dispersed into India as well as other parts of tropical Asia from Africa after both India and Africa collided with Eurasia. Furthermore, multiple dispersals have taken place between Southeast Asia and India. The findings consolidate the rapidly building evidence that much of the current assemblage of biota actually dispersed into-India after it collided with Asia.

evolutionary biology↗

bioRxiv2018

Hybridisation or Incomplete Lineage Sorting: The convoluted story about the origin of the capped-golden langur lineage (Cercopithecidae: Colobinae)

Hybridisation and incomplete lineage sorting (ILS) are two of the many naturally occurring evolutionary processes that contribute to variability in individual gene histories. However, distinguishing between hybridisation and ILS is challenging and these processes can lead to serious difficulties in inferring phylogenies. These processes have been invoked as a possible explanation for the evolution of the endangered golden langur and its sister species, the capped langur. Previous molecular studies have retrieved conflicting phylogenies, with mitochondrial tree grouping capped and golden langur (CG) lineage with a largely Indian genus Semnopithecus while nuclear markers supporting their affiliation with a Southeast Asian genus, Trachypithecus. However, as pointed by others, the use of nuclear copies of mitochondrial DNA in the above studies might have generated the discordance. Because of this discordance, the phylogenetic position of CG lineage has been much debated in recent times. In this study, we have used nine nuclear and eight mitochondrial markers in conjunction with coalescent based species tree approach to better understand the evolutionary origin of CG lineage. Concatenated nuclear as well as the mitochondrial dataset recovered congruent relationships where CG lineage was sister to Trachypithecus. However nuclear species tree estimated using different multispecies coalescent methods were incongruent with the above result, suggesting presence of ILS/hybridisation. Furthermore, CG lineage is morphologically intermediate between Semnopithecus and Trachypithecus with respect to skull and body measurements. Based on these evidences, we argue that CG lineage evolved through hybridisation between Semnopithecus and Trachypithecus. Taxonomic and conservation implications of these results are also discussed.

evolutionary biology↗

bioRxiv2018

Role of geography and climatic oscillations in governing into-India dispersal of freshwater snails of the family: Viviparidae

The Indian subcontinent has experienced numerous paleogeological and paleoclimatic events during the Cenozoic which shaped the biotic assembly over time in the subcontinent. The role of these events in governing the biotic exchange between Southeast Asia and Indian subregion is underexplored. We aimed to uncover the effects the collision of the Indian and Asian plate, marine transgression in the Bengal basin as well as the paleoclimatic changes in the subcontinent and adjoining regions, on the dispersal of freshwater snail family Viviparidae from Southeast Asia (SEA) to Indian subregion. Extensive sampling was carried out throughout the Indian subcontinent to capture the current diversity of the targeted lineages. Three mitochondrial and two nuclear markers were sequenced from these samples and combined with published sequences to reconstruct a near complete global phylogeny of Viviparidae. Molecular dating and ancestral range estimation were undertaken to obtain the time frame for the dispersal events. Results from these analyses were contrasted with paleoclimate and paleogeology to better understand the biogeography of Indian viviparids. Results support at least two dispersal events into India from Southeast Asia. The earlier event is likely to have occurred during a warm and humid Eocene period before a permanent land connection was established between the two landmasses. While the more recent dispersal occurred post-suturing and overlapped with a time in late Tertiary to Quaternary when arid climate prevailed. However, we could not firmly establish how the marine transgressions influenced the dispersal events. Even though most biotic exchange between India and SEA are noted to be post-suturing, our results add to a growing body of work that suggests faunal exchange pre-suturing probably mediated by intermittent land connections.

evolutionary biology↗