Impact of urbanization and temperature on local abundance of Drosophila repleta Wollaston (1858) in the Western Himalayas

Ramniwas Seema,Kumar Girish,Pandey Manish,Singh Divya 한국응용곤충학회 2024 Journal of Asia-Pacific Entomology Vol.27 No.1

With rising global temperatures and expanding urbanization, rapid species abundance shifts and local extinctions may occur. We have observed a notable increase in the local population of Drosophila repleta, a species adapted to warmer environments, which was never documented at higher altitudes in the Western Himalayas before 2003. This change can be attributed to the recent acceleration of urbanization and the effects of climate change. To understand the species’ response to temperature variations, we conducted a comparison of life-history traits at two different temperatures: 17 ◦ C and 25 ◦ C. These temperatures were chosen to simulate the variations expe rienced in 2003 and 2017, respectively. Our findings revealed a significant decrease in trait values at 17 ◦ C, indicating a lower evolutionary capacity for adapting to colder and drier habitats. Additionally, we simulta neously examined the performance of life-history traits in response to different food resources, which corre sponded to the levels of urbanization (carbohydrate-rich vs. protein-rich). The results showed a significant increase in fecundity, viability, and the percentage of adult emergence in flies reared on protein-rich food. This suggests that D. repleta possesses the ability to survive by utilizing the available food resources in the newly urbanized habitats. Considering the projected rise in global temperatures and further urbanization in the near future, D. repleta is likely to become even more abundant in urban environments. However, this could potentially pose a health risk due to the species’ ability to transmit disease-causing organisms.

Climate warming mediates range shift of two differentially adapted stenothermal Drosophila species in the Western Himalayas

Ravi PARKASH,Seema RAMNIWAS,Babita Kajla 한국응용곤충학회 2013 Journal of Asia-Pacific Entomology Vol.16 No.2

The average temperature of the earth has increased from 0.3 to 0.6 °C, and warming is facilitating faunal reshuffling. Variable thermal environments warrant mechanisms to adjust the expression of phenotypic values to environmental needs. Ectothermic Drosophilids are profoundly affected by thermal selection (i.e., genetic effects)or through induced effects on phenotypes (i.e., plastic effects). Climatic data for the last fifty years involves a significant change in average temperature (Tave) ofWestern Himalayas,which has affected the distribution and boundaries of various Drosophilids in this region. There is a significant decline in the number of D. nepalensis from lower ranges; whereas D. ananassae is reported to be introduced to lower tomid mountainous ranges. Further, a comparison of fecundity, hatchability, and viability at different growth temperatures has shown significant decrease in trait values at 17 °C in D. ananassae and at 25 °C in D. nepalensis. Thus, the recent range changes of these two species involve genetic effects on ecophysiological and plastic effects on life history traits. Our results indicate that thermal plasticity of life history traits can be species-specific; thus climate change may lead to a mismatch of such traits to the changing environment. We suggest that D. nepalensis and D. ananassae could serve as indicator species for analyzing range changes under changing climatic conditions. Evolutionary biologists can provide unique perspective to the examination of how climate change will affect the earth's biota.

Fitness consequences of body melanization in Drosophila immigrans from montane habitats

Shama Singh,Seema RAMNIWAS,Ravi PARKASH 한국곤충학회 2009 Entomological Research Vol.39 No.3

We investigated eight populations of Drosophila immigrans from low to high montane localities (600–2202 m) for altitudinal variations in abdominal melanization and fitness-related traits (desiccation resistance, copulation duration, and fecundity). On the basis of common garden experiments, persistence between-population differences at 21°C suggests that observed variations in fitness-related traits have a genetic basis. Parent–offspring regression analyses showed higher heritability (h2= 0.77) for melanization patterns on all the abdominal tergites. All the traits showed significantly higher repeatability across generations. Under colder and drier environments in dispersed montane localities, abdominal melanization and desiccation resistance significantly increased (1.5–1.9 fold) along altitude. Thus, there are correlated effects of abdominal melanization on desiccation resistance. Genetic correlations, based on family means, were significantly high between abdominal melanization and other fitness traits. Furthermore, darker flies along increasing altitude resulted in a 35–40% increase in copulation duration as well as fecundity. There are significantly positive correlations of abdominal melanization with copulation duration as well as fecundity on the basis of within- as well as between-population variations. Such observations are in agreement with the thermal budget hypothesis. Present data suggest that changes in body melanization impact fitness-related traits in montane populations of Drosophila immigrans.

Melanization plasticity of Drosophila kikkawai, Drosophila leontia and reciprocal hybrids under different temperatures

Singh Divya,Ramniwas Seema,Tyagi Pankaj Kumar,Kumar Girish,Gola Deepak 한국응용곤충학회 2022 Journal of Asia-Pacific Entomology Vol.25 No.1

Drosophila (Sophophora) kikkawai, Burla, 1954 and Drosophila (Sophophora) leontia, Tsacas & David 1978 are closely related sibling species, the former being cosmopolitan and the latter is restricted to tropical localities. We investigated the influence of introgressive hybridization on phenotypic diversity of the two sibling species in the present study. How hybridization supports the relative abundance of pure species according to latitudinal cline is the aim of this study because hybrids show a tendency to acquire geographical location of their parent species in equal or greater abundance. How hybridization supports the plasticity for melanization of hybrids is not explored yet. The two species can cross and generate hybrids. For this, we crossed true breeding strains of both species to obtain the hybrids i.e. dark female (♀) of D. kikkawai (D. k) with males (♂) of D. leontia (D. l) in cross I and light ♀ of D. k with ♂ of D. l in cross II along with their reciprocal crosses. Finally, we studied the plasticity of both species and their hybrids at 6 growth temperatures (14, 17, 21, 25, 28 and 31 ◦ C). We found that there is no plasticity for melanization in true breeding darker and lighter strain of D. kikkawai as well as D. leontia whereas hybrids of both species showed high phenotypic plasticity. Significant differences in slope values across tem peratures in parental and hybrid lines suggest plastic effects. Phenotypic variation in abdominal melanization in hybrids can be interpreted as a result of gene introgression with D. kikkawai. We conclude that introgressive hybridization might be an important, although underestimated, mechanism shaping species distribution and adaptation.

Body melanization and its adaptive role in thermoregulation and tolerance against desiccating conditions in drosophilids

Subhash RAJPUROHIT,Ravi PARKASH,Seema RAMNIWAS 한국곤충학회 2008 Entomological Research Vol.38 No.1

Melanism seems to have evolved independently through diverse mechanisms in various taxa and different ecological factors could be responsible for selective responses. Increased body melanization at higher altitudes as well as latitudes is generally considered to be adaptive for thermoregulation. Physiological traits such as body melanization and desiccation resistance have been investigated independently in diverse insect taxa at three levels: within populations, between populations and among species. A substantial number of Drosophila studies have reported clinal variations in both these traits along latitude. A possible link between these traits had remained unexplored in wild and laboratory populations of ectothermic insect taxa, including drosophilids, to date. Simultaneous analysis of these traits in assorted darker and lighter phenotypes in each population in the present study showed parallel changes for body melanization and desiccation resistance. The mechanistic basis of evolving desiccation resistance was explained on the basis of differential rates of water loss per hour in darker versus lighter phenotypes in six populations of Drosophila melanogaster from adjacent localities differing substantially in altitude all along the Indian subcontinent. Data on cuticular impermeability suggest a possible role of melanization in desiccation tolerance. However, substantial gaps remain in extending these results to other insect taxa and further exploring the physiological and molecular changes involved in melanization for conferring desiccation resistance.

Climate change, boundary increase and elongation of a pre-existing cline: A case study in Drosophila ananassae

Subhash RAJPUROHIT,Ravi PARKASH,Shama SINGH,Seema RAMNIWAS 한국곤충학회 2008 Entomological Research Vol.38 No.4

During the past two to three decades, Drosophila ananassae, a warm adapted tropical species, has invaded low to mid altitude localities in the western Himalayas. Due to its cold sensitivity, this species had never been recorded from higher latitudes as well as altitudes in India to the 1960s. A latitudinal cline in this desiccation-sensitive species corresponds with southern humid tropical localities rather than northern drier subtropical localities. An extension of its cline into lowland to midland montane localities has resulted due to global climatic change as well as local thermal effects through anthropogenic impact. However, D. ananassae populations at species borders are characterized by lower genetic variability for body melanization as well as for desiccation resistance. There is a lack of thermal plastic effects for body melanization, and the observed extended cline might represent evolutionary (genetic) response due to selection pressure imposed by drier habitats. A comparison of fecundity, hatchability and viability at three growth temperatures (17, 20 and 25°C) showed significant reduction in trait values at 17 °C in D. ananassae. Thus, its recent range expansion into northern montane localities might involve genetic effects on stress-related traits and plastic effects on life history traits. We suggest that D. ananassae could serve as an indicator species for analyzing range expansion under changing climatic conditions.