Timing Is Everything. Temporal and Spatial Niche Segregation in Curculio spp. (Coleoptera: Curculionidae) Associated with Oak Trees

Abstract

Oak seed predatory weevils occurring in Poland are prone to increased interspecific competition due to the limited number of Quercus species, compared to southern Europe, in which they can develop. Therefore, analyses on the preferences of three weevil species for acorn sizes chosen for reproduction, as well as on reproductive period duration, were performed. Cafeteria-type experiments were set for females of three species associated with one oak species. Females were allowed to choose and oviposit in acorns of different sizes and growth stages. Research revealed statistically significant differences between the masses of acorns chosen for oviposition by females of Curculio glandium (the biggest), C. pellitus (medium), and C. venosus (the smallest). Studied weevils also differed in terms of the beginning of the reproductive period, which corresponded with the increasing mass of growing acorns. Moreover, C. glandium was observed to be the only species to perform radial egg galleries and lay a considerably higher and varied number of eggs. The results support the hypothesis of a strategy aimed at reducing interspecific competition between Curculio spp. in terms of limited host plant species number.

Hard Nut to Crack. Acorn Hardness Implications on Oviposition of the Acorn Weevil Curculio glandium Marsham, 1802 (Coleoptera: Curculionidae)

“…Additionally, this preference was confirmed by our previous observations made in the natural environment, when C. glandium females oviposited on fallen acorns (mostly not matured, abscissed ones) until mid-September [13]. Opportunistic behavior might be characteristic for C. glandium solely, as other species coexisting on oaks (C. venosus and C. pellitus) in Poland have not been observed using naturally cracked acorns for oviposition [12]. Additionally, C. elephas does not seem to exploit this niche too, even if it faces similar resource issues (M.R.…”

“…Some species in the Curculio genus are known for reproductive diapause. This is the case for European species associated with oaks (C. glandium, C venosus and C. pellitus), as the imago is present and active from May, but insects start reproduction no sooner than July [12,30]. A similar phenomenon was described in a Nearctic species, C. sayi (Gyllenhall), associated with Castanea trees in the United States.…”

“…Fifteen undamaged fruits originating from the same tree were collected once a week from July 23th to September 3rd. The period is the time frame covering C. glandium reproduction in Poland, which usually starts in the last week of July and ends in early September [12]. Acorns were picked up early in the morning, measured and then proceeded to further analysis in the Laboratory of Rheological Measurements (Institute of Food Sciences, Warsaw University of Life Sciences-SGGW).…”

“…Curculio glandium starts oviposition relatively late (i.e., starting in the third week of July) and females drill and lay eggs into considerably grown (but not fully matured) acorns. Furthermore, the discussed species turned out to be the only Curculio weevil known so far to create radial galleries (harboring significantly higher numbers of eggs, compared to co-occurring C. venosus and C. pellitus) instead of simple egg holes [12]. The most recently proven peculiarity of C. glandium reproduction is females' ability to oviposit, also into fallen acorns with natural cracks.…”

The Ant-like Tachydromia Complex in the Iberian Peninsula—Insights from Habitat Suitability Modelling for the Conservation of an Endemism (Diptera: Hybotidae)

“…Hence, in these areas, both the genetic diversity of oak taxa and of the highly sedentary ant-like flies was shaped by the same phylogeographic conditions. Consequently, these regions encompass umbrella-habitats that commonly harbor highly specific biodiversity [ 38 , 50 , 51 , 52 , 53 , 54 ]. Additionally, it is fundamental to complete the knowledge gaps regarding the species already known with very few presence records: T. stenoptera , T. cantabrica , T. nigrohirta , T. pieltaini, and T. pandellei .…”