Presence of two types of flowers with respect to nectar sugar in two gregariously flowering species

Many species of animal-pollinated flowers are known to vary widely in the nectar content of flowers. Some proportion of flowers in many species is apparently nectarless, and such flowers are believed to be 'cheaters'. Cheating may explain a part of the variability in nectar content. If cheating exists as a qualitatively different strategy then we expect bimodality in the distribution of nectar content of flowers. It has been shown in a multispecies study that gregarious species have a higher proportion of cheater flowers. We studied the frequency distribution of total nectar sugar in two gregariously flowering species Lantana camara and Utricularia purpurascens, which differed in other floral and ecological characters. At the population level, both the species showed significant bimodality in the total sugar content of flowers. The obvious sources of heterogeneity in the data did not explain bimodality. In Lantana camara, bimodality was observed within flowers of some of the individual plants sampled. In Utricularia purpurascens the proportion of nectarless flowers was more in high-density patches, suggesting that the gregariousness hypothesis may work within a species as well. The results support the hypothesis of cheating as a distinct strategy since two distinct types of flowers were observed in both the species. The effect of density in Utricularia purpurascens also supports the gregariousness hypothesis

Did southern Western Ghats of peninsular India serve as refugia for its endemic biota during the Cretaceous volcanism?

The Western Ghats (WG) of south India, a global biodiversity hotspot, has experienced complex geological history being part of Gondwana landmass and encountered extensive volcanic activity at the end of Cretaceous epoch. It also has a climatically and topographically heterogeneous landscape. Thus, the WG offer a unique setting to explore the influence of ecological and geological processes on the current diversity and distribution of its biota. To this end, three explicit biogeographical scenarios were hypothesized to evaluate the distribution and diversification of wet evergreen species of the WG - (1) southern WG was a refuge for the wet evergreen species during the Cretaceous volcanism, (2) phylogenetic breaks in the species phylogeny would correspond to geographic breaks (i.e., the Palghat gap) in the WG, and (3) species from each of the biogeographic subdivisions within the WG would form distinct clades. These hypotheses were tested on the centipede genus Digitipes from the WG which is known to be an ancient, endemic, and monophyletic group. The Digitipes molecular phylogeny was subjected to divergence date estimation using Bayesian approach, and ancestral areas were reconstructed using parsimony approach for each node in the phylogeny. Ancestral-area reconstruction suggested 13 independent dispersal events to explain the current distribution of the Digitipes species in the WG. Among these 13 dispersals, two dispersal events were at higher level in the Digitipes phylogeny and were from the southern WG to the central and northern WG independently in the Early Paleocene, after the Cretaceous Volcanism. The remaining 11 dispersal events explained the species' range expansions of which nine dispersals were from the southern WG to other biogeographic subdivisions in the Eocene-Miocene in the post-volcanic periods where species-level diversifications occurred. Taken together, these results suggest that southern WG might have served as a refuge for Digitipes species during Cretaceous volcanism

Evolutionary biogeography of the centipede genus Ethmostigmus from Peninsular India: testing an ancient vicariance hypothesis for Old World tropical diversity

Abstract Background Understanding the relative influence of vicariance and dispersal in shaping Old World tropical biodiversity remains a challenge. We aimed to infer the roles of these alternative biogeographic processes using a species time-tree for the centipede genus Ethmostigmus from the Old World tropics. Additionally, we explored fine-scale biogeographic patterns for an endemic radiation of Ethmostigmus from the peninsular Indian Plate (PIP), an area with complex geological and climatic history. Results Divergence time estimates suggest that Ethmostigmus began diversifying in the Late Cretaceous, 99 (± 25) million years ago (Ma), its early biogeographic history shaped by vicariance. Members of Ethmostigmus in PIP form a monophyletic group that underwent endemic radiation in the Late Cretaceous, 72 (± 25) Ma. In contrast, a new species of Ethmostigmus from north-east India formed a clade with African/Australian species. Fine-scale biogeographic analyses in PIP predict that Indian Ethmostigmus had an ancestor in southern-central parts of the Western Ghats. This was followed by four independent dispersal events from the southern-central Western Ghats to the Eastern Ghats, and between different parts of the Western Ghats in the Cenozoic. Conclusions Our results are consistent with Gondwanan break-up driving the early evolutionary history of the genus Ethmostigmus. Multiple dispersal events coinciding with geo-climatic events throughout the Cenozoic shaped diversification in PIP. Ethmostigmus species in PIP are restricted to wet forests and have retained that niche throughout their diversification

Data from: Evolution of ontogenic change in color defenses of swallowtail butterflies

Natural selection by visually-hunting predators has led to evolution of color defense strategies such as masquerade, crypsis and aposematism that reduce the risk of predation in prey species. These color defenses are not mutually exclusive, and switches between strategies with ontogenic development are widespread across taxa. However, the evolutionary dynamics of ontogenic color change are poorly understood. Using comparative phylogenetics, we studied the evolution of color defenses in the complex lifecycles of swallowtail butterflies (Family: Papilionidae). We also tested the relative importance of life history traits, chemical and visual backgrounds, and ancestry on the evolution of protective coloration. We found that vulnerable early and late instar caterpillars of species that feed on sparsely-vegetated, toxic plants were aposematic, whereas species that feed on densely-vegetated, non-toxic plants had masquerading and cryptic caterpillars. Masquerading caterpillars resembled bird droppings at early instars, and transitioned to crypsis with an increase in body size at late instars. The immobile pupae – safe from motion-detecting, visually hunting predators – retained the ancestral cryptic coloration in all lineages irrespective of the toxic nature of the host plant. Thus, color defense strategy (masquerade, crypsis or aposematism) at a particular lifestage in the lifecycle of swallowtail butterflies was determined by the interaction between life history traits such as body size and motion levels, phytochemical and visual backgrounds, and ancestry. We show that ontogenic color change in swallowtail butterflies is an adaptive response to age-dependent vulnerability to predation

Cretaceous-Tertiary diversification among select Scolopendrid centipedes of South India

Given that peninsular India was part of the Gondwanan super continent, part of its current biota has Gondwanan origin. To determine the Gondwanan component of the peninsular Indian biota, a large number of species spanning diverse taxonomic groups need to be sampled from multiple, if not all, of the former Gondwanan fragments. Such a large scale phylogenetic approach will be time consuming and resource intensive. Here, we explore the utility of a limited sampling approach, wherein sampling is confined to one of the Gondwanan fragments (peninsular India), in identifying putative Gondwanan elements. To this end, samples of Scolopendrid centipedes from Western Ghats region of peninsular India were subjected to molecular phylogenetic and dating analyses. The resulting phylogenetic tree supported monophyly of the family Scolopendridae which was in turn split into two clades constituting tribes Otostigmini and Scolopendrini-Asanadini. Bayesian divergence date estimates suggested that the earliest diversifications within various genera were between 86 and 73 mya, indicating that these genera might have Gondwanan origin. In particular, at least four genera of Scolopendrid centipedes, Scolopendra, Cormocephalus, Rhysida and Digitipes, might have undergone diversification on the drifting peninsular India during the Late Cretaceous. These putative Gondwanan taxa can be subjected to more extensive sampling to confirm their Gondwanan origin. (C) 2011 Elsevier Inc. All rights reserved

Tracking the variability of phenotypic traits on a molecular phylogeny: an example from scolopendrid centipedes in peninsular India

Taxonomic studies on scolopendrid centipedes have often documented variability at the individual and population levels and applied those data to questions of species delimitation, but these investigations have mostly lacked an explicit phylogenetic framework. A molecular phylogeny and recent taxonomic revision for Indian species of the scolopendrid Digitipes Attems, 1930, permit variability of traditional taxonomic characters for Scolopendridae to be mapped onto a phylogeny. Based on their fit to the tree using maximum likelihood, reliable species-level characters include the number of glabrous antennal articles, presence of a median ridge on the tergites, and presence or absence of a tarsal spur on leg 20. Characters that are conserved within and diagnostic for particular species but labile within others (typically with geographic structure) include the first tergite with paramedian sutures, presence or absence of a lateral spine on the coxopleuron, and the number of spines in a ventromedial row on the ultimate leg prefemur. Comparisons with published accounts of variability in species of other scolopendrid genera, particularly Scolopendra and Otostigmus, show that Indian Digitipes has conserved morphology in some characters that are taxonomically useful elsewhere in the family, and most of its taxonomically informative characters have analogous patterns of variability in other genera. The approach used in this study to evaluate morphological variation in a phylogenetic framework can be applied to other taxa in which morphologically cryptic species have been reported and where species diagnosis requires a combination of characters

Sampling localities of the genus <i>Digitipes</i> in the Western Ghats (WG).

<p>Boundaries of northern, central and southern WG and Nilgiris are also shown.</p

Coalescent Method in Conjunction with Niche Modeling Reveals Cryptic Diversity among Centipedes in the Western Ghats of South India

<div><h3>Background</h3><p>There has been growing interest in integrative taxonomy that uses data from multiple disciplines for species delimitation. Typically, in such studies, monophyly is taken as a proxy for taxonomic distinctiveness and these units are treated as potential species. However, monophyly could arise due to stochastic processes. Thus here, we have employed a recently developed tool based on coalescent approach to ascertain the taxonomic distinctiveness of various monophyletic units. Subsequently, the species status of these taxonomic units was further tested using corroborative evidence from morphology and ecology. This inter-disciplinary approach was implemented on endemic centipedes of the genus Digitipes (Attems 1930) from the Western Ghats (WG) biodiversity hotspot of India. The species of the genus Digitipes are morphologically conserved, despite their ancient late Cretaceous origin.</p> <h3>Principal Findings</h3><p>Our coalescent analysis based on mitochondrial dataset indicated the presence of nine putative species. The integrative approach, which includes nuclear, morphology, and climate datasets supported distinctiveness of eight putative species, of which three represent described species and five were new species. Among the five new species, three were morphologically cryptic species, emphasizing the effectiveness of this approach in discovering cryptic diversity in less explored areas of the tropics like the WG. In addition, species pairs showed variable divergence along the molecular, morphological and climate axes.</p> <h3>Conclusions</h3><p>A multidisciplinary approach illustrated here is successful in discovering cryptic diversity with an indication that the current estimates of invertebrate species richness for the WG might have been underestimated. Additionally, the importance of measuring multiple secondary properties of species while defining species boundaries was highlighted given variable divergence of each species pair across the disciplines.</p> </div