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Title: The effect of pre-dispersal seed predators on the reproductive potential of Calotropis procera (Aiton) W.T. Aiton in Punjab, Pakistan
Authors: Ali, Shahid
Keywords: Biological & Medical Sciences
Issue Date: 2020
Publisher: University of the Punjab , Lahore
Abstract: The present study was aimed to evaluate the effect of pre-dispersal seed predators on the reproductive potential of Calotropis procera. The study was conducted in five districts viz; Lahore, Kasur, Faisalabad, Sheikhupura, and Gujranwala of the Punjab Province, Pakistan. There were seven sites in Lahore and one each in the rest of the districts. During the study, 28 insects were found to be associated with Calotropis procera, out of these, seven were pollinators, thirteen casual visitors, and five being generalized herbivores while three were specialized herbivores. The specialized herbivores included one stem borer (Niphona grisea) and two pre-dispersal seed predators (Paramecops farinosus and Dacus persicus). Paramecops farinosus and D. persicus were prioritized for detailed studies on their life histories, incidence, seasonal damage potential, and current and future distribution predictions. The developmental duration (oviposition to adult) of P. farinosus was 59.9 ± 0.82 days. A single female, in its life span, oviposits 5.4 ± 0.32 times and laid 32.9 eggs, and from these eggs, 25.1 adults emerged and added to the progeny. The generation time ranged between 40-49 days with an average 42.1 ± 0.4 days. Newly emerged single female of D. persicus in her life oviposits 4.5 ± 0.26 times and laid 81.6 eggs, from these eggs total 66.1 adults were added to the progeny. Both insects had a relatively short generation period with at least two generations per year in Lahore, Pakistan. Due to their high intrinsic reproductive potential, both P. farinosus and D. persicus build their populations in the field quickly. The highest number of P. farinosus adults‟ plant-1 was 11.3 ± 4.6 in the peak of the summer season (July August) while a minimum (1.98 ± 0.2) was recorded in the winter season (December). On the other hand, the highest number of D. persicus adults plant-1 (17.5 ± 8.8) was recorded in late summer (September-October) while the lowest number plant-1 was 4.1 iv ± 2.1 in the winter season (December). As the populations of P. farinosus and D. persicus build up in the field, they started to infest and damage the fruits, thereby declining the reproductive potential of C. procera. Infestation percentage (%) of P. farinosus was maximum in mid-summer season (Jun-July) and of D. persicus it was in late summer season (September-October). During the peak infestation stage, there were up to 24 % and 74 % fruits showing up to 100 % seed damaged by P. farinosus and D. persicus, respectively. The average length of P. farinosus and D. persicus infested fruits was 31 % (4.03 ± 0.61 cm) and 32 % (3.98 ± 0.22 cm) smaller as compared to healthy fruits (5.9 ± 0.16 cm) (P < 0.05). Similarly, the average fresh mass of P. farinosus and D. persicus infested fruits was up to 24 % (18.8 ± 2.62 g) and 58 % (10.3 ± 1.21 g) less compared to the fresh mass of healthy fruits (24.8 ± 1.06 g; P < 0.05), respectively. To predict the distribution of P. farinosus and D. persicus under current and future climate change (+ 3 oC) scenarios, CLIMEX modeling program was used. Based on a CLIMEX model for the current climate, all hotter and drier parts of Asia, Africa, South America and Australia are predicted to be suitable for the D. persicus. It was predicted that a climate change (+ 3 oC) scenario will be more suitable for D. persicus for its distribution. The model predicts that at present, central and northern parts of Pakistan, southern and eastern parts of India, and almost all parts of Sri Lanka are suitable for P. farinosus. Similarly, the central parts of Africa and America and the eastern coastline of Australia are suitable for P. farinosus. However, a contraction in the suitability of P. farinosus was observed for the climate change scenario as compared to the current suitability. Keywords: Invasive species, biological control, pre-dispersal seed predators, damage potential, CLIMEX modeling
Gov't Doc #: 21803
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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