| dc.description.abstract | Much of systematics done in the past was based on morphological data. One of the
drawbacks of using morphological data is that in groups with conserved morphology, the
diversity is often underestimated and relationships difficult to infer. One such group are the
fossorial blindsnakes (superfamily Typhlopoidea, infraorder Scolecophidia). The diversity,
life histories and ecology of such groups remain unexplored due to their sub-terranean and
secretive habit. India has around 17 species, spanning four genera and two families.
However, many of these species have not been discovered since their first descriptions, and
many are suspected to be synonyms. For my PhD, I studied the diversity of the four
typhlopoid genera in India, from a phylogenetic and biogeographical perspective, and
attempted to understand diversification patterns within one species group, which gave rise to
the Indotyphlops braminus, a blindsnake with a surprisingly cosmopolitan distribution.
In the first chapter, I explore the phylogenetic positions of the four genera- Gerrhopilus,
Indotyphlops, Grypotyphlops and Argyrophis, in the global phylogeny. I use a concatenated
dataset of five nuclear markers to reconstruct the phylogenies using maximum likelihood and
Bayesian methods. The results show that Indian typhlopoids have very diverse affiliations.
Gerrhopilus is retrieved as sister to all other typhlopoids. Grypotyphlops is nested with the
African genera, which corroborates its classification based on morphology. Indotyphlops was
shown to be polyphyletic, with Indotyphlops porrectus being sister to all southeast Asian
typhlopoids, and thus requiring a taxonomic revision. We also find an Indian radiation of
Indotyphlops. Argyrophis from India is sister to the Argyrophis from southeast Asia.
The second chapter looks at the biogeographic origins of the four genera. The divergence
times were estimated using the concatenated five gene dataset used in the first chapter, with
nine fossils used to calibrate the time-tree. The time-tree was then used for ancestral area
estimation in BioGeoBEARS, implemented in R. I carried out a time stratified analysis to
accommodate the dramatic changes in the position of the Indian landmass over geological
time and model fitting to compare multiple dispersal and vicariance hypotheses. The best fit
model invokes both dispersal and vicariance as the explanations for the current distribution of
typhlopoids in India. India harbours an ancient Gondwanan group of typhlopoids as well as
comparatively younger dispersals from Africa and Asia.
The third chapter looks at more fine scale diversification of blindsnakes in peninsular India,
particularly Indotyphlops braminus. Indotyphlops braminus is an enigmatic blindsnake that
has a pan-tropical distribution, most probably due to human mediated dispersal. It is also
proposed to be the only obligate parthenogenetic snake as of now. Karyotyping studies have
shown Indotyphlops braminus to be triploid, which has been proposed to be a result of
hybridization, and a possible cause of the parthenogenetic reproduction. I investigated the
discordance between mitochondrial and nuclear phylogenies to understand whether
Indotyphlops braminus is a result of hybridization between two Indian species. I also
explored additional lines of evidence by looking at the discordance between gene trees and
species trees and a statistical test for hybridization. The results strongly suggest that this
cosmopolitan, triploid, parthenogenetic taxon is indeed a hybrid of two Indotyphlops species
found in India, but it is not the true Indotyphlops braminus. This new, hybrid species,
therefore, merits a taxonomic revision.
The underlying theme of my thesis is understanding the origins and diversification patterns in
the Indian typhlopoids at broad and fine taxonomic scales, from phylogenetic and
biogeographical perspectives. | en_US |
