Predatory hymenopteran assemblages in boreal Alaska: associations with forest composition and post-fire succession

Abstract

Changes to the fire regime in boreal Alaska are shifting the ratio of coniferous to deciduous dominance on the landscape. The increase in aspen and birch may have important effects on predatory hymenopteran assemblages by providing a source of extrafloral nectar and increasing prey availability. Furthermore, fire-induced changes in successional age alter habitat structure and microclimate in ways that may favor ants. This study is the first to characterize the influence of fire-related vegetation changes on boreal predatory hymenopteran assemblages. We compare the abundance, species richness, and composition of predatory hymenopteran assemblages among forests at different stages of succession and of varying post-fire tree species compositions. Ant assemblages were weakly related to forest composition, but ants were significantly more abundant and speciose in early-successional forests than in mid-late successional forests. In contrast, macropterous wasp morphospecies richness and abundance, and micropterous wasp abundance, were positively related to the basal area of aspen, but were not related to successional stage. The results suggest that shifts in boreal vegetation related to climate warming will result in changes to the predaceous insect community, with ants responding positively to disturbance and wasps responding positively to an increase in the representation of aspen on the landscape.

Functional Role of Extrafloral Nectar in Boreal Forest Ecosystems under Climate Change

“…Other commonly encountered, yet not behaviorally dominant, ant species in boreal forests include Formica neogagates Viereck, F. subsericea Say, Lasius americanus Emery, Aphaenogaster rudis Enzmann, and several species of the genus Myrmica [84,85]. In early-successional aspen stands of inner Alaska, Formica podzolica Francoeur, Leptothorax muscorum (Nylander), F. subaenescens Emery, F. aserva Forel, and Camponotus herculeanus have been found to be characteristic species [35]. It has been suggested that early successional aspen stands may provide critical resources such as EFN [36] or prey availability for these species [35].…”

“…In early-successional aspen stands of inner Alaska, Formica podzolica Francoeur, Leptothorax muscorum (Nylander), F. subaenescens Emery, F. aserva Forel, and Camponotus herculeanus have been found to be characteristic species [35]. It has been suggested that early successional aspen stands may provide critical resources such as EFN [36] or prey availability for these species [35].…”

“…The importance of EFN in plant-ant mutualism has been demonstrated in various ecosystems, including tropical dry forests [23] and rainforests [24][25][26], temperate forests [27,28], savannas [29], shrublands [30], dry grasslands [31] and desert ecosystems [32,33]. However, the role of EFN in boreal ecosystems is still poorly understood [28,34,35] and most experimental field studies in the boreal-subarctic zone have been conducted with Populus tremuloides Michx. in Alaska [36][37][38].…”

“…in Alaska [36][37][38]. Although EFN together with aphid (homopteran) honeydew is known to have a key role in shaping the structure of canopy-dwelling ant communities in rainforest ecosystems [39], only a study by Wenninger et al [35] has assessed the role of EFN in ant community structures in boreal forest ecosystems.…”

Ground-Dwelling Arthropod Community Responses to Recent and Repeated Wildfires in Conifer Forests of Northern New Mexico, USA

“…These communities have been reported to be sensitive to alterations in vegetation and litter cover from various forest disturbances, ranging from severe wildfires to relatively minor manipulations of coarse woody debris [12][13][14][15][16][17][18][19][20][21]. Thus, fires may affect ground-dwelling arthropods through direct mortality and/or via impacts on soil and litter/duff layers, understory and overstory vegetation composition, the quantity and arrangement of woody debris, and changes in microclimate [12,[22][23][24][25]. While numerous studies have found that fires decrease arthropod density, e.g., [12,24], responses at a community level can seem idiosyncratic, and some taxa appear to be resistant to fire disturbance, while others are highly sensitive [26][27][28][29][30].…”