Variation in life-history traits within a population is caused by genetic, maternal and environmental factors. We explored the high variability in development time, adult body weight and fecundity in females of the sexually size dimorphic spider Trichonephila senegalensis. Their mothers originated from two habitats - strongly seasonal Namibia and mildly seasonal South Africa - and we reared F1 females under standardized laboratory conditions. We found that a considerable part of the variability in recorded life-history traits is caused by family-specific effects, comprising genetic, maternal and early environmental influences. Furthermore, we show population differences in development time, where females originating from Namibia matured within shorter periods than females from South Africa. Also, the relationship between development time and adult weight differs between the two populations, as a significant correlation is only found in females with Namibian origin. Against common wisdom, there was a weak overall correlation between adult weight and clutch mass. We also found that females make different life-history decisions under increasing rather than under decreasing daylength. Although a considerable part of variability in life-history traits is family-specific, we discuss how the between-population differences in life histories and their trade-offs reflect adaptation to diverse habitats.