Synchronisation of egg hatching of brown hairstreak (Thecla betulae) and budburst of blackthorn (Prunus spinosa) in a warmer future

Synchronisation of the phenology of insect herbivores and their larval food plant is essential for the herbivores’ fitness. The monophagous brown hairstreak (Thecla betulae) lays its eggs during summer, hibernates as an egg, and hatches in April or May in the Netherlands. Its main larval food plant blackthorn (Prunus spinosa) flowers in early spring, just before the leaves appear. As soon as the Blackthorn opens its buds, and this varies with spring temperatures, food becomes available for the brown hairstreak. However, the suitability of the leaves as food for the young caterpillars is expected to decrease rapidly. Therefore, the timing of egg hatch is an important factor for larval growth. This study evaluates food availability for brown hairstreak at different temperatures. Egg hatch and budburst were monitored from 2004 to 2008 at different sites in the Netherlands. Results showed ample food availability at all monitored temperatures and sites but the degree of synchrony varied strongly with spring temperatures. To further study the effect of temperature on synchronisation, an experiment using normal temperatures of a reference year (T) and temperatures of T + 5°C was carried out in climate chambers. At T + 5°C, both budburst and egg hatch took place about 20 days earlier and thus, on average, elevated temperature did not affect synchrony. However, the total period of budburst was 11 days longer, whereas the period of egg hatching was 3 days shorter. The implications for larval growth by the brown hairstreak under a warmer climate are considered.

Old lineage on an old island : Pixibinthus, a new cricket genus endemic to New Caledonia shed light on gryllid diversification in a hotspot of biodiversity

Few studies have focused on the early colonization of New Caledonia by insects, after the re-emergence of the main island, 37 Myr ago. Here we investigate the mode and tempo of evolution of a new endemic cricket genus, Pixibinthus, recently discovered in southern New Caledonia. First we formally describe this new monotypic genus found exclusively in the open shrubby vegetation on metalliferous soils, named 'maquis minier', unique to New Caledonia. We then reconstruct a dated molecular phylogeny based on five mitochondrial and four nuclear loci in order to establish relationships of Pixibinthus within Eneopterinae crickets. Pixibinthus is recovered as thesister clade of the endemic genus Agnotecous, mostly rainforest-dwellers. Dating results show that the island colonization by their common ancestor occurred around 34.7 Myr, shortly after New Caledonia re-emergence. Pixibinthus and Agnotecous are then one of the oldest insect lineages documented so far for New Caledonia. This discovery highlights for the first time two clear-cut ecological specializations between sister clades, as Agnotecous is mainly found in rainforests with 19 species, whereas Pixibinthus is found in open habitats with a single documented species. The preference of Pixibinthus for open habitats and of Agnotecous for forest habitats nicely fits an acoustic specialization, either explained by differences in body size or in acoustic properties of their respective habitats. We hypothesize that landscape dynamics, linked to major past climatic events and recent change in fire regimes are possible causes for both present-day low diversity and rarity in genus Pixibinthus. The unique evolutionary history of this old New Caledonian lineage stresses the importance to increase our knowledge on the faunal biodiversity of 'maquis minier', in order to better understand the origin and past dynamics of New Caledonian biota

Landscape-scale expansion of Roesel's bush-cricket Metrioptera roeselii at the north-western range limit in Central Europe (Orthoptera : Tettigoniidae)

Wißmann J, Schielzeth H, Fartmann T. Landscape-scale expansion of Roesel's bush-cricket Metrioptera roeselii at the north-western range limit in Central Europe (Orthoptera : Tettigoniidae). Entomologia Generalis. 2009;31:317-326.Range expansion linked to global warming is a widespread phenomenon among insects. This range expansion may be either gradual and on a broad-front or discontinuous following long distance dispersal. Many species of Orthoptera show a distinct wing-length dimorphism related to dispersal and rare long-wing individuals are assumed to contribute significantly to the colonisation of new habitat patches. Grid-based distribution surveys of Roesel's bush cricket Metriopera roeselii (Hagenbach 1822) at the edge of the species' range in NW' Germany were conducted in 1991, 1996 and 2004. Most newly colonised grid cells were directly adjacent to cells that were occupied in previous surveys or were connected to them by other colonised cells. The maximal distance between newly colonised grid cells and cells that were occupied in previous surveys was 6.3 km between 1991 and 1996 and 5.1 km between 1996 and 2004. The proportion of macropterous individuals sampled in 2004 was very low (1.4%). Macropterous individuals tended to occur in newly colonised, more isolated and low abundance grid cells. Hence, range expansion of M roeselii took place by short-distance colonisation from cells that were occupied in previous surveys rather than by single events of long-distance dispersal