Adaptive radiation through phenological shift: the importance of the temporal niche in species diversification

Abstract

International audience1. Phenological shift in oviposition in seed predators may be a key factor for adaptive radiation if temporal differences lead to less intense competition. 2. This hypothesis was tested at two sites in the French Alps in three sympatric species of larch cone flies grouped into two phenological groups (early and late) differing in adult emergence and oviposition timing by approximately 2 weeks. The present study assessed the intensity of competition within and between groups by measuring four larval traits. Cone traits were measured, and the impact of early species parasitism on cone development was assessed. 3. The occupation of the central axis of a developing cone by one early larva has a strong detrimental effect on cone growth and seed production. However, there was almost no correlation between the variables measured on the cones and on the larvae, suggesting that the resources available were not limiting. 4. Inter-group competition had no significant effect on early larvae. In contrast, both inter- and intra-group competition had a significant negative effect on late larvae length (-11% and -16% respectively), dry mass (-8% and -23%), and lipid mass (-15% and -26%). The intensity of competition was stronger among larvae in the same phenological group, which is consistent with the hypothesis that shifts in oviposition promote adaptive radiation in larch cone flies by reducing competition among larvae

Niche separation of pollen beetle parasitoids

“…In the absence of plant odors, T. heterocerus preferred late first instar larvae against a control, but in the presence of uninfested OSR with an equal ratio of buds and flowers, T. heterocerus preferred the odor of the smallest stage (early first instar) over plant odor alone. Background odors are always present in nature and may affect the use of volatiles by parasitoids in various ways (Hilker and McNeil, 2008;Schröder and Hilker, 2008). It is difficult to explain why uninfested plant odor decreases the attractivity of late first instar larvae while it enhances the attractivity of early first instar larvae, but it is possible that flower volatiles, indicating floral nectar and pollen, may play some confounding role here.…”

“…Parasitoid wasps that attack and develop in the same host can achieve this e.g., by temporal and spatial separation (Comins and Hassel, 1996;Hackett-Jones et al, 2009;Sachet et al, 2009), specialization on different developmental stages of the host (Briggs et al, 1993;Yamamoto et al, 2007), specialization on different microhabitats (Fleury et al, 2009), differential host detection behavior (van Dijken and van Alphen, 1998), or wasp life history parameters (Bonsall et al, 2002).…”

Forest Insects and Climate Change

“…Seed and cone insects are poorly studied in relation to climate change response. Since most species are host-specific and depend on tight synchrony with cone development to share the cone niche [115][116][117], climate change is likely to affect interactions between cones and insects as well as between insect species. However, adult emergence of three species of larch cone flies, Strobilomyia spp., appeared to adjust tightly to the earlier blossoming of larch in the Alps, which has advanced 12-15 days since the 1980s (Roques, unpublished observations).…”

The effect of climate on masting in the European larch and on its specific seed predators

“…Other factors acting on Strobilomyia populations were not taken into account in this study, including competition between Strobilomyia species (Sachet et al 2008), competition with other predators of larch seeds such as Cecidomyiids (Roques 1993), the length of diapause (Roques 1993), or the occurrence of parasitoids (Roques 1988). The ability of all species of Strobilomyia to enter into prolonged diapause (i.e., as pupae in the soil for up to 4 years) is presumably an adaptive strategy evolved by the fly to overcome the masting strategy evolved by its host plant.…”