Biology subjects

Kodandaramaiah, U.

Publications and source records attributed to Kodandaramaiah, U..

9 recordsLinked to original sources

bioRxiv2026

PUPAL COLOUR PLASTICITY AS A STRATEGY AGAINST DESICCATION

O_LITerrestrial insects are vulnerable to desiccation due to their small body size. Because insects lose most water through cuticular evaporation, cuticular traits strongly influence desiccation tolerance. Individuals with greater cuticular melanisation, i.e., darker ones, are hypothesised to tolerate desiccation better than less melanised ones. C_LIO_LIIn many butterflies, pupal colour is plastic - individuals pupating on leaves tend to be greener, while those that pupate away from leaves (off-leaf), such as on tree bark or defoliated twigs, tend to be browner. Brown pupae are hypothesised to have more cuticular melanin and are expected to experience higher desiccation stress than leaf-borne green pupae. Thus, plasticity in pupal melanisation may be an adaptation against desiccation. We tested this in the butterfly Eurema blanda. C_LIO_LIWe demonstrate that individuals pupating on on-leaf substrates are greener than those pupating on off-leaf substrates, and that desiccation stress is higher in the off-leaf substrates, a microenvironment typical of brown pupae, than in typical green pupae. Using Raman spectroscopy, we show that brown, but not green, pupal cuticles contain melanin. C_LIO_LIFollowing this, we obtained greener and browner pupae by manipulating substrate colour. When subjected to desiccation stress, browner pupae survived better than greener ones. There was no correlation between pupal colour and survival in the absence of desiccation stress. Thus, melanisation appears to confer a survival advantage to pupae by increasing desiccation tolerance. C_LIO_LISurvival under desiccating conditions was inversely related to water loss. Interestingly, melanisation did not correlate with water loss, suggesting that melanisation helps tolerate desiccation through physiological mechanisms not directly related to water loss reduction. C_LIO_LIOur findings reveal an additional, crucial, adaptive value of pupal colour plasticity, a trait that has been studied primarily from an anti-predatory perspective. C_LI

evolutionary biology↗

bioRxiv2026

Are seasonally plastic anti-predatory and desiccation tolerance traits developmentally linked?

In many tropical areas, seasonal rainfall leads to distinct dry and wet seasons. Many butterflies developing under wet season conditions develop into adults with large ventral eyespots on the wing margins, whereas those developing under dry season conditions have smaller or no eyespots. In greener, wet season habitats, larger eyespots can divert predator attacks toward the wing margins, while reduced eyespot size improves camouflage in the dry leaf litter-dominated habitat during the dry season. However, the dry season is also characterised by higher desiccation stress than the wet season. We hypothesised that larvae developing under dry season conditions develop into adults with higher desiccation tolerance than those reared under wet season conditions. We tested this by rearing larvae of the butterfly Mycalesis mineus under simulated dry and wet season conditions and assaying the desiccation tolerance of the resulting adults. Butterflies reared in dry conditions survived longer under desiccation stress, lost lesser water during pupal-adult metamorphosis, and were heavier than those reared in wet conditions. We also tested the correlation between eyespot size and desiccation tolerance. A negative correlation between the traits would be expected if similar developmental pathways regulate them. Consistent with this expectation, individuals with smaller eyespots had higher desiccation tolerance. Our results demonstrate plasticity in desiccation tolerance, and suggest that predator avoidance and desiccation tolerance traits may share similar developmental pathways.

evolutionary biology↗

bioRxiv2025

Contrasting mechanisms for using humidity as cue for seasonal polyphenism in two tropical butterflies

Many tropical butterflies show wing pattern plasticity across dry and wet seasons. Dry-season morphs of satyrines (Nymphalidae: Satyrinae) typically are cryptic with small or no eyespots on the ventral wing surface. In contrast, wet-season morphs have large eyespots on their wing margins. These eyespots deflect predator attacks away from vital body parts. Extensive studies have shown that eyespot size is influenced by the temperature experienced during larval development. Temperature-mediated eyespot size plasticity is adaptive in regions where temperature increases with the onset of the wet season. However, many tropical regions lack a reliable temperature-rainfall correlation, and thus, temperature may not always be a reliable predictor of the upcoming adult environment. A potential environmental cue that correlates strongly with seasonality is relative humidity (hereafter, humidity). With the approach of the wet season, humidity increases, and then declines with the onset of the dry season. Here, we tested whether humidity modulates eyespot-size plasticity in two sympatric butterflies that experience similar ecological pressures: Mycalesis mineus and Melanitis leda. We found that humidity directly influenced eyespot size in My. mineus; individuals reared at high humidity developed into adults with larger eyespots than those from low humidity. In contrast, eyespot size in Me. leda showed a weak direct effect of humidity. Instead, humidity modulated eyespot size in Me. leda indirectly through induced changes in the host plant quality. Since the late larval and prepupal stages are temporally closer to the adult environment, selection may favour greater sensitivity to the environmental cue during these stages than during early larval stages. To determine the humidity-sensitive phase, we conducted a switching experiment where humidity was shifted from low to high, and vice versa, at different developmental stages. We demonstrated that, in My. mineus, wandering larval and prepupal stages are sensitive to humidity, whereas the early-feeding larval phases are insensitive. Contrastingly, humidity switching did not influence the eyespot size in Me. leda. This study highlights how two diverging species, evolving under similar ecological pressures, integrate environmental cues in distinct ways to modulate wing pattern plasticity.

evolutionary biology↗

bioRxiv2025

Local adaptations in wing-pattern and life history trait plasticity in a butterfly: humidity as a cue where temperature is unreliable

Many butterflies have wet and dry season morphs with large and small wing eyespots respectively. Eyespot size plasticity is adaptive because the morphs function to avoid predation in their respective season. Eyespot size has been shown to be regulated by rearing temperature in many species. However, temperature is unreliable in some regions because it poorly predicts seasons, and other cues such as humidity may be more reliable. We investigated inter-population differences in cue use for eyespot plasticity in the butterfly Melanitis leda. We reared butterflies from three Indian populations under combinations of temperature and humidity. Butterflies from a population (Vithura) where humidity differentiates seasons but temperature does not, responded only to humidity. Butterflies from a population (Tirunelveli) where seasonality is not distinct, and where temperature and humidity are both unreliable, also responded only to humidity. Butterflies from another population (Coimbatore) where seasonality is not distinct, but where temperature has the highest intra-annual variation, responded only to temperature. This suggests local adaptation in cue use. Life-history traits also differed among populations, with the two populations from more arid regions developing faster and attaining larger body sizes than the one from the humid region. Fast development may be adaptive in dry regions where suitable host plants are available only briefly, while large body size may confer desiccation resistance. We show for the first time that humidity can regulate eyespot size, and that reaction norms vary across populations, fitting to regional climates.

ecology↗

bioRxiv2024

Correlated evolution of multiple traits gives butterflies a false head

Many butterflies possess a combination of characters at the posterior hindwing end, superficially resembling their head. This false head has been hypothesised to deflect predator attacks towards the false head area. A clear understanding of the diversity and evolution of false head traits across butterflies is lacking. Here, we tested whether false head traits evolved from simple to complex in order to achieve a greater resemblance to a head. We also tested if false head traits form an adaptive constellation and, thus, evolved correlatedly. Using a phylogenetic framework with 927 lycaenid species, our results illustrate evolutionary patterns of five false traits - (i) false antennae, (ii) spot, (iii) conspicuous colouration in the false head area, (iv) false head contour in the false head area, and (v) convergent lines. We found that false traits (i)-(iv) evolved in a correlated fashion across the phylogeny, likely driven by a common selective pressure. Our findings support the idea that false head functions as an adaptive constellation for predator attack deflection.

evolutionary biology↗

bioRxiv2023

Larval growth rate affects wing shape more than eyespot size in the seasonally polyphenic butterfly Melanitis leda

Butterflies often show adaptive phenotypic plasticity where environmental cues during early stages are used to produce a phenotype that maximizes fitness in the environment experienced by adults. Many tropical satyrine butterflies (Nymphalidae: Satyrinae) are seasonally polyphenic and produce distinct wet- and dry-season form adults providing tight environment-phenotype matching in seasonal environments. Dry-season forms, which are expressed in the dry season, can be induced in the laboratory by growing larvae at low temperatures or on poor food quality. Since both these factors also tend to reduce larval growth rate, larval growth rate may be an internal cue that translates the environmental cues into the expression of phenotypes. If this is the case, we predict that slower-growing larvae would be more likely to develop a dry-season phenotype. To test this hypothesis, we measured both larval growth rate and adult phenotype (eyespot size and wing shape) of individuals of the common evening brown butterfly (Melanitis leda), reared at various temperatures and on various host-plant species. We found that among treatments, larvae with lower growth rates (low temperature, particular host plants) were more likely to develop dry-season phenotypes (small eyespots, falcate wing tips), but within treatments, larval growth rate was mainly linked to wing shape, not eyespot size. These relationships tended to be stronger for males than females as males showed a wider range of eyespot sizes and wing shapes. Overall, only plasticity in wing shape appears to be (partly) mediated by larval growth, and in a sex-specific manner.

evolutionary biology↗

bioRxiv2023

Drivers of phenotypic differentiation across rock outcrop sky islands in Impatiens plants

Habitat specialization can lead to naturally fragmented populations separated by unoccupied habitats that comprise potential barriers to dispersal. Habitat fragmentation can result in phenotypic divergence between populations, and eventual speciation. We investigate trait divergence in a habitat specialist plant species - Impatiens lawii - that is specialized on rock outcrops in the Western Ghats mountains of India. We compare trait divergence in this species with that in a closely related species, I. oppositifolia, which is a continuously distributed habitat generalist that co-occurs with the former species on rock outcrops in addition to being found in intervening regions. As predicted, we found that floral traits were more strongly structured across populations in I. lawii than in I. oppositifolia, supporting the role of habitat specialization. In both species, floral traits were more strongly structured across populations than were vegetative traits. Interestingly, the population pairs that were significantly differentiated for floral traits differed from those differentiated for vegetative traits. Furthermore, some population pairs differed in vegetative traits but not in floral traits. The incongruence in patterns of floral and vegetative trait differentiation suggests the role of selection. There was no association between floral trait variation and geographic distance in either species. Surprisingly, there was a significant correlation between geographic distance and vegetative trait variation in I. oppositifolia, but not in I. lawii (Fig 4D; Table 2), possibly due to genetic drift. Overall, a combination of habitat specificity, drift and selection best explains trait variation in I. lawii.

evolutionary biology↗

bioRxiv2020

To group or not to group: Effect of prolonged exposure to predation and resource availability on the shoaling behaviour of zebrafish (Danio rerio)

Individuals of many species live in groups to obtain anti-predatory advantages, foraging benefits and for social reasons. Living in large groups can reduce predation, but as group size increases, competition for resources also increases. The trade-off between the advantages of group living for an individual and competition caused by it can determine group dynamics, and this trade-off can vary with environmental conditions. Shoaling behaviour, the tendency of fish to form groups, is shown to be affected by factors such as resource availability, presence of predators and conspecifics. Although studies indicate that both predation and starvation pressure in an environment can determine whether fish choose to shoal or not, whether prolonged exposure to such conditions influences shoaling behaviour remains little explored. Here, we test how predation pressure and resource availability may interactively shape the shoaling behaviour of zebrafish (Danio rerio) when exposed to combinations of these pressures over a two-week period. We find that shoal size increases with predation and decreases with starvation, and that greater predation pressure increases shoaling tendencies even under reduced food availability. Overall, we show that prolonged exposure to varying predation pressure and resource availability can together influence shoaling tendencies of fish even when such pressures are relaxed. Significant statementIn group living species, group structure and dynamics depend on various intrinsic factors and environmental stressors. Shoaling behaviour in fish, where individuals aggregate to form groups, is shown to be altered with environmental factors such as predation and resource availability. Although studies have examined the effects of these cues on shoaling behaviour, the ecological circumstances experienced by fish could also influence shoaling tendencies. We here show that shoaling behaviour is also shaped by previous experience of fish to predation and food resource availability. We check how shoaling behaviour varies with differences in predation pressure and resource availability after prolonged exposure to these conditions by measuring the shoal size and shoal cohesion in zebrafish. This study illuminates how shoaling tendencies of individuals shaped by the environmental conditions persist even when these environmental pressures are removed.

animal behavior and cognition↗

bioRxiv2020

The latitudinal diversity gradient in brush-footed butterflies (Nymphalidae): conserved ancestral tropical niche but different continental histories.

The latitudinal diversity gradient (LDG) is arguably one of the most striking patterns in nature. The global increase in species richness toward the tropics across continents and taxonomic groups stimulated the formulation of many hypotheses to explain the underlying mechanisms of this pattern. We evaluated several of these hypotheses to explain spatial diversity patterns in the butterfly family, Nymphalidae, by assessing the contributions of speciation, extinction, and dispersal to the LDG, and also the extent to which these processes differ among regions at the same latitude. We generated a new, time-calibrated phylogeny of Nymphalidae based on 10 gene fragments and containing ca. 2,800 species ([~]45% of extant diversity). Neither speciation nor extinction rate variations consistently explain the LDG among regions because temporal diversification dynamics differ greatly across longitude. For example, we found that Neotropical nymphalid diversity results from low extinction rates, not high speciation rates, and that biotic interchanges with other regions were rare. Southeast Asia was also characterized by a low speciation rate but, unlike the Neotropics, was the main source of dispersal events through time. Our results suggest that global climate change throughout the Cenozoic, particularly during the Eocene-Oligocene transition, combined with the conserved ancestral tropical niches, played a major role in generating the modern LDG of butterflies.

ecology↗