The tree of life is highly asymmetrical in its clade wise species richness, and this has often been attributed to variation in diversification rates either across time or lineages. Variations across lineages are usually associated with traits that increase lineage diversification. Certain traits can also hinder diversification by increasing extinction, and such traits are called evolutionary dead ends. Ecological specialization has usually been considered as an evolutionary dead end. However, recent analyses of specializations along single axes have provided mixed support for this model. Here, we test if fossoriality, a trait that forces specialization at multiple axes, acts as an evolutionary dead end in squamates (lizards and snakes) using recently developed phylogenetic comparative methods. We show that fossoriality is an evolutionary dead end in snakes but not in lizards. Fossorial snakes exhibit reduced speciation and increased extinction compared to nonfossorial snakes. Our analysis also indicates that transition rates from fossoriality to nonfossoriality in snakes are significantly lower than transition rates from nonfossoriality to fossoriality. Overall our results suggest that broad-scale ecological interactions that lead to specialization at multiple axes limit diversification.
Uropeltid snakes (Family Uropeltidae) are non-venomous, fossorial snakes that are found above ground occasionally, during which time they are exposed to predation. Many species are brightly coloured, mostly on the ventral surface, but these colours are expected to have no function below the ground. Observations have shown that the cephalic resemblance (resemblance to heads) of uropeltid tails may direct attacks of predators towards the hardened tails, thereby potentially increasing handling times for predators. Experiments have also shown that predators learn to avoid prey that are non-toxic and palatable but are difficult to capture, hard to process or require long handling time when such prey advertise their unprofitability through conspicuous colours. We here postulate that uropeltid snakes use their bright colours to signal long handling times associated with attack deflection to the tails, thereby securing reduced predation from predators that can learn to associate colour with handling time. Captive chicken experiments with dough models mimicking uropeltids indicate that attacks were more common on the tail than on the head. Field experiments with uropeltid clay models show that the conspicuous colours of these snakes decrease predation rates compared to cryptic models, but a novel conspicuous colour did not confer such a benefit. Overall, our experiments provide support for our hypothesis that the conspicuous colours of these snakes reduce predation, possibly because these colours advertise unprofitability due to long handling times.
Two new species of geckos of the genus Cnemaspis Strauch, 1887 are described from the southern Western Ghats of Kerala. Both species are medium to large sized Cnemaspis and can be differentiated from all other Indian congeners by a suite of distinct morphological characters. Both species are found in the high elevation forests of the two major massifs— Anaimalai Hills and Agasthyamalai Hills and are presently known to have very restricted distributional ranges. The discovery of these novel species highlights the understudied diversity of reptiles in the high mountain ranges of the Western Ghats.
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