Genotypic differences in embryonic life history traits ofFolsomia quadrioculata(Collembola: Isotomidae) across a wide geographical range

Abstract

1. Life history traits play a central role in adaptation to specific environmental conditions. Egg development time, hatchling, and egg batch size in 10 populations of the soil‐dwelling collembolan species Folsomia quadrioculata (Tullberg, 1871) from diverse habitats across arctic and temperate regions, ranging in latitude from 43 to 81°N were studied. 2. For all traits, 15 °C was used as the reference temperature. Phenotypic plasticity was studied by changing temperature to 10 and 20 °C in hatchling size, and to 20 °C in egg development time. The effect of latitude, climatic zone, and summer temperature at their sites of sampling was tested to address the hypotheses that populations from cooler areas would have (i) a faster temperature‐dependent egg development, (ii) a larger hatchling size, (iii) smaller egg batches and (iv) higher phenotypic plasticity 3. The first and fourth hypothesis were not supported, whereas the second and third were partly supported when including the whole latitudinal gradient, but not within regions. Plasticity showed a complex pattern, including large differences between populations from similar macroclimates and considerable similarity between some populations from contrasting climates. Small effects of latitude and macroclimatic variables emphasised that local climate and microhabitat should be taken into account when evaluating thermal conditions as possible drivers of population‐specific differences in soil‐dwelling ectotherms. 4. There was a trade‐off between egg batch and hatchling sizes. A weak correlation between the population mean egg development time and the mean hatchling size suggested that the populations are, or have been, exposed to differential selection.

Thermal plasticity in postembryonic life history traits of a widely distributed Collembola: Effects of macroclimate and microhabitat on genotypic differences

“…This is consistent with the high survival of this population at the highest temperature treatment. Moreover, low reproduction, starting at an older age and larger size, together with previously documented large offspring size of this population (Sengupta et al., ) might be an adaptation to improve protection against desiccation (Kærsgaard, Holmstrup, Malte, & Bayley, ; Le Lagadec, Chown, & Scholtz, ). In the Oslo Forest population (OF), all traits, except size at first reproduction, indicated specialization to a narrower and fairly low temperature range than that in the other populations, with an optimum around 15°C. In addition, this population showed the clearest signs of heat stress at the highest temperatures studied.…”

“…Thus, similar to DK, LSI appears to be a temperature generalist, although for a different reason. It comes from a site characterized by highly unpredictable climate (Birkemoe & Leinaas, ; Sengupta et al., ). Consequently, the advantage of efficiently utilizing unpredictable warm spells may prevent typical cold adaptation in these traits (Clarke, ). The other high arctic population (ERI) had large body size and high reproduction at 20°C, but little or no reproduction at lower temperatures, even though it inhabits by far the coldest site of this study (Sengupta et al., ).…”

“…Folsomia quadrioculata is a soil litter‐dwelling (hemi‐edaphic) Collembolan. It is widespread in the Holarctic, inhabiting diverse habitats (Deharveng & Lek, ; Hågvar, ; Hertzberg, Leinaas, & Ims, ; Ponge, , ; Sengupta et al., ). It shows indeterminate growth, reproduces sexually, and life cycles range from several generations per year in continental Europe (Grégoire‐Wibo, ; Haarløv, ) to more than a 1‐year life cycle in the arctic (Birkemoe & Sømme, ; Hertzberg, Yoccoz, Ims, & Leinaas, ).…”

“…The stock cultures of each population were founded with 100–200 Collembolans, extracted without heating from 5 to 10 randomly collected soil samples. Both stock rearing and experiments used plastic culture boxes (diameter = 3.4 cm, height = 3 cm), with plastic lids and moist bottom of plaster of Paris mixed with charcoal (for detailed information on pre‐experimental treatment of the stock cultures see Appendix and Sengupta et al., ). For temperature treatments (10, 15, 20, and 25°C), we used climate incubators (Sanyo MIR 553, Osaka, Japan).…”

Evaluating the role and measures of juvenile growth rate: latitudinal variation in insect life histories

“…For body size, we recorded systematic genetically based converse Bergmann's latitudinal clines (Blanckenhorn and Demont , Chown and Gaston ) in each of the six distantly related lepidopteran species, selected for our experiments without any a priori knowledge about among‐population size differences. Emphasizing the consistency of these trends across the species, we still have to admit that our sample did not allow us to test for non‐linearity of this relationship, recently detected in some studies on the subject (Davenport and Hossack , Sengupta et al ).…”