Genetical Research



Evolution of reduced pre-adult viability and larval growth rate in laboratory populations of Drosophila melanogaster selected for shorter development time


N. G. PRASAD a1, MALLIKARJUN SHAKARAD a1, VISHAL M. GOHIL a1p1, V. SHEEBA a1, M. RAJAMANI a1 and AMITABH JOSHI a1c1
a1 Evolutionary Biology Laboratory, Evolutionary & Organismal Biology Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, PO Box No. 6436, Jakkur, Bangalore 560 064, India

Abstract

Four large (n > 1000) populations of Drosophila melanogaster, derived from control populations maintained on a 3 week discrete generation cycle, were subjected to selection for fast development and early reproduction. Egg to eclosion survivorship and development time and dry weight at eclosion were monitored every 10 generations. Over 70 generations of selection, development time in the selected populations decreased by approximately 36 h relative to controls, a 20% decline. The difference in male and female development time was also reduced in the selected populations. Flies from the selected populations were increasingly lighter at eclosion than controls, with the reduction in dry weight at eclosion over 70 generations of selection being approximately 45% in males and 39% in females. Larval growth rate (dry weight at eclosion/development time) was also reduced in the selected lines over 70 generations, relative to controls, by approximately 32% in males and 24% in females. However, part of this relative reduction was due to an increase in growth rate of the controls populations, presumably an expression of adaptation to conditions in our laboratory. After 50 generations of selection had elapsed, a considerable and increasing pre- adult viability cost to faster development became apparent, with viability in the selected populations being about 22% less than that of controls at generation 70 of selection.

(Received July 28 1999)
(Revised February 29 2000)
(Revised June 12 2000)


Correspondence:
c1 Corresponding author. Tel: +80 8462750. Fax: +80 8462766. e-mail: ajoshi@jncasr.ac.in
p1 Present address: Department of Biological Sciences, Wayne State University, Detroit MI 48202, USA.


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