https://libjncir.jncasr.ac.in/xmlui/handle/10572/1521 2026-04-04T05:31:55Z 2026-04-04T05:31:55Z Dey, Snigdhadip Goswami, Bedartha Joshi, Amitabh https://libjncir.jncasr.ac.in/xmlui/handle/10572/2450 2017-02-21T10:25:24Z 2014-01-01T00:00:00Z

Effects of symmetric and asymmetric dispersal on the dynamics of heterogeneous metapopulations: Two-patch systems revisited Dey, Snigdhadip; Goswami, Bedartha; Joshi, Amitabh Although the effects of dispersal on the dynamics of two-patch metapopulations are well studied, potential interactions between local dynamics and asymmetric dispersal remain unexplored. We examined the dynamics of two Ricker models coupled by symmetric or asymmetric constant-fraction dispersal at different rates. Unlike previous studies, we extensively sampled the r(1)-r(2) space and found that stability of the coupled system was markedly affected by interactions between dispersal (in terms of strength and asymmetry) and local dynamics. When both subpopulations were intrinsically chaotic, increased symmetry in the exchange of individuals had a greater stabilizing impact on the dynamics of the system. When one subpopulation showed considerably more unstable dynamics than the other, higher asymmetry in the exchange of individuals had a stabilizing or destabilizing effect on the dynamics depending on whether the net dispersal bias was from the relatively stable to the relatively unstable subpopulation, or vice versa. The sensitivity of chaotic dynamics to stabilization due to dispersal varied with r-value in the chaotic subpopulation. Under unidirectional or bidirectional symmetric dispersal, when one subpopulation was intrinsically chaotic and the other had stable dynamics, the stabilization of chaotic subpopulations with r similar to 3.3-4.0 occurred at the lowest dispersal rates, followed by chaotic subpopulations with r similar to 2.7-2.95 and, finally, chaotic subpopulations with r similar to 2.95-3.3. The mechanism for this pattern is not known but might be related to the range and number of different attainable population sizes possible in different r-value zones. (C) 2013 Elsevier Ltd. All rights reserved. Restricted Access

2014-01-01T00:00:00Z Dey, Punyatirtha Mendiratta, Kanika Bose, Joy Joshi, Amitabh https://libjncir.jncasr.ac.in/xmlui/handle/10572/2163 2017-02-21T10:22:47Z 2016-01-01T00:00:00Z

Enhancement of larval immune system traits as a correlated response to selection for rapid development in Drosophila melanogaster Dey, Punyatirtha; Mendiratta, Kanika; Bose, Joy; Joshi, Amitabh Restricted Access

2016-01-01T00:00:00Z Nagarajan, Archana Natarajan, Sharmila Bharathi Jayaram, Mohan Thammanna, Ananda Chari, Sudarshan Bose, Joy Jois, Shreyas V. Joshi, Amitabh https://libjncir.jncasr.ac.in/xmlui/handle/10572/2161 2017-02-21T10:23:01Z 2016-01-01T00:00:00Z

Adaptation to larval crowding in Drosophila ananassae and Drosophila nasuta nasuta: increased larval competitive ability without increased larval feeding rate Nagarajan, Archana; Natarajan, Sharmila Bharathi; Jayaram, Mohan; Thammanna, Ananda; Chari, Sudarshan; Bose, Joy; Jois, Shreyas V.; Joshi, Amitabh The standard view of adaptation to larval crowding in fruitflies, built on results from 25 years of multiple experimental evolution studies on Drosophila melanogaster, was that enhanced competitive ability evolves primarily through increased larval feeding and foraging rate, and increased larval tolerance to nitrogenous wastes, at the cost of efficiency of food conversion to biomass. These results were at odds from the predictions of classical K-selection theory, notably the expectation that selection at high density should result in the increase of efficiency of conversion of food to biomass, and were better interpreted through the lens of alpha-selection. We show here that populations of D. ananassae and D. n. nasuta subjected to extreme larval crowding evolve greater competitive ability and pre-adult survivorship at high density, primarily through a combination of reduced larval duration, faster attainment of minimum critical size for pupation, greater time efficiency of food conversion to biomass and increased pupation height, with a relatively small role of increased urea/ammonia tolerance, if at all. This is a very different suite of traits than that seen to evolve under similar selection in D. melanogaster, and seems to be closer to the expectations from the canonical theory of K-selection. We also discuss possible reasons for these differences in results across the three species. Overall, the results reinforce the view that our understanding of the evolution of competitive ability in fruitflies needs to be more nuanced than before, with an appreciation that there may be multiple evolutionary routes through which higher competitive ability can be attained. Open Access

2016-01-01T00:00:00Z Sarangi, Manaswini Nagarajan, Archana Dey, Snigdhadip Bose, Joy Joshi, Amitabh https://libjncir.jncasr.ac.in/xmlui/handle/10572/2162 2017-02-21T10:23:09Z 2016-01-01T00:00:00Z

Evolution of increased larval competitive ability in Drosophila melanogaster without increased larval feeding rate Sarangi, Manaswini; Nagarajan, Archana; Dey, Snigdhadip; Bose, Joy; Joshi, Amitabh Multiple experimental evolution studies on Drosophila melanogaster in the 1980s and 1990s indicated that enhanced competitive ability evolved primarily through increased larval tolerance to nitrogenous wastes and increased larval feeding and foraging rate, at the cost of efficiency of food conversion to biomass, and this became the widely accepted view of how adaptation to larval crowding evolves in fruitflies. We recently showed that populations of D. ananassae and D. n. nasuta subjected to extreme larval crowding evolved greater competitive ability without evolving higher feeding rates, primarily through a combination of reduced larval duration, faster attainment of minimum critical size for pupation, greater efficiency of food conversion to biomass, increased pupation height and, perhaps, greater urea/ammonia tolerance. This was a very different suite of traits than that seen to evolve under similar selection in D. melanogaster and was closer to the expectations from the theory of K-selection. At that time, we suggested two possible reasons for the differences in the phenotypic correlates of greater competitive ability seen in the studies with D. melanogaster and the other two species. First, that D. ananassae and D. n. nasuta had a very different genetic architecture of traits affecting competitive ability compared to the long-term laboratory populations of D. melanogaster used in the earlier studies, either because the populations of the former two species were relatively recently wild-caught, or by virtue of being different species. Second, that the different evolutionary trajectories in D. ananassae and D. n. nasuta versus D. melanogaster were a reflection of differences in the manner in which larval crowding was imposed in the two sets of selection experiments. The D. melanogaster studies used a higher absolute density of eggs per unit volume of food, and a substantially larger total volume of food, than the studies on D. ananassae and D. n. nasuta. Here, we show that long-term laboratory populations of D. melanogaster, descended from some of the populations used in the earlier studies, evolve essentially the same set of traits as the D. ananassae and D. n. nasuta crowding-adapted populations when subjected to a similar larval density at low absolute volumes of food. As in the case of D. ananassae and D. n. nasuta, and in stark contrast to earlier studies with D. melanogaster, these crowding-adapted populations of D. melanogaster did not evolve greater larval feeding rates as a correlate of increased competitive ability. The present results clearly suggest that the suite of phenotypes through which the evolution of greater competitive ability is achieved in fruitflies depends critically not just on larval density per unit volume of food, but also on the total amount of food available in the culture vials. We discuss these results in the context of an hypothesis about how larval density and the height of the food column in culture vials might interact to alter the fitness costs and benefits of increased larval feeding rates, thus resulting in different routes to the evolution of greater competitive ability, depending on the details of exactly how the larval crowding was implemented. Open Access

2016-01-01T00:00:00Z