Life history plasticity magnifies the ecological effects of a social wasp invasion

Abstract

An unresolved question in ecology concerns why the ecological effects of invasions vary in magnitude. Many introduced species fail to interact strongly with the recipient biota, whereas others profoundly disrupt the ecosystems they invade through predation, competition, and other mechanisms. In the context of ecological impacts, research on biological invasions seldom considers phenotypic or microevolutionary changes that occur following introduction. Here, we show how plasticity in key life history traits (colony size and longevity), together with omnivory, magnifies the predatory impacts of an invasive social wasp (Vespula pensylvanica) on a largely endemic arthropod fauna in Hawaii. Using a combination of molecular, experimental, and behavioral approaches, we demonstrate (i) that yellowjackets consume an astonishing diversity of arthropod resources and depress prey populations in invaded Hawaiian ecosystems and (ii) that their impact as predators in this region increases when they shift from small annual colonies to large perennial colonies. Such trait plasticity may influence invasion success and the degree of disruption that invaded ecosystems experience. Moreover, postintroduction phenotypic changes may help invaders to compensate for reductions in adaptive potential resulting from founder events and small population sizes. The dynamic nature of biological invasions necessitates a more quantitative understanding of how postintroduction changes in invader traits affect invasion processes.biological invasions ͉ predation S pecies introductions disrupt ecosystems and can threaten biodiversity (1-3). Predicting the magnitude of these effects, however, has proved difficult (4), in part because invaders and members of the recipient biota may undergo microevolutionary changes or display phenotypic plasticity following introduction events (5-7). For invaders, postintroduction modifications in behavior, morphology, or life history traits may influence invasion success and alter the capacity of these species to disrupt the ecosystems they invade. In this way, trait plasticity may permit individuals to compensate for reduced genetic diversity (8) and the subsequent loss of adaptive potential that is assumed to result from translocation to new environments (9).Trait plasticity may be especially important for invasive social insects, because small behavioral changes at the individual level can scale up to produce dramatic and unexpected changes at the colony level (e.g., the formation of supercolonies) (10). In this sense, the phenotypic envelope of the social superorganism can encompass a larger set of potential morphotypes compared with that of a typical solitary organism. Here, we quantify the ecological effects of trait plasticity in an omnivorous social insect invader (the western yellowjacket, Vespula pensylvanica) that is shaping Hawaiian arthropod assemblages through top-down effects on multiple trophic levels. In part because Hawaii lacks native eusocial insects (11), yellowjacket invasions pose a potentially ...

Jack-of-all-trades: phenotypic plasticity facilitates the invasion of an alien slug species

“…This framework has been developed for a more mechanistic understanding of plant invasions but has, to our knowledge, never been applied to invasive animals. Generally, most evidence for phenotypic plasticity as an important trait of invasive organisms is derived from plants [15][16][17][18][19] with some studies also investigating vertebrates [20], aquatic organisms [7,[21][22][23][24][25][26][27], entognatha [28,29] or insects [8,30,31]. Evidence from terrestrial molluscs, however, is largely lacking.…”

Predation or scavenging? Thoracic muscle pH and rates of water loss reveal cause of death in arthropods

“…Although information about the availability of fresh carcasses in the field might improve estimates of how much carrion predators consume (Foltan et al, 2005;Juen and Traugott, 2005), measuring predator number, carcass removal rates and carrion availability in the field poses logistic difficulties (Foltan et al, 2005), and may be infeasible for small taxa such as arthropods. The approach developed in this study could indicate the relative frequency of scavenging versus predation by central-place invertebrate foragers (Kasper et al, 2004;Tillberg et al, 2007;Wilson et al, 2009) because diet items can be obtained from returning individuals prior to consumption. Further investigation into how muscle physiology of prey and carrion change in the gut of consumers is needed to assess the applicability of this method to non-central-place foragers.…”

“…Because the pH of invertebrate thoracic muscle decreases predictably post mortem and is sensitive to stress, we can evaluate the peri-mortem stress level experienced by diet items and distinguish prey from carrion. Our study uses social insects as a model system, because ants and social wasps represent ecologically dominant scavenging predators in many terrestrial ecosystems (Jeanne, 1979;Hölldobler and Wilson, 1990;Snyder and Evans, 2006;Wilson et al, 2009). Nonetheless, it often remains unclear whether these consumers are serving as predators or scavengers (Tillberg et al, 2007).…”

Traits related to biological invasion: A note on the applicability of risk assessment tools across taxa

“…Certain traits lead to a competitive advantage for invasive insects; in general, large, unicolonial forms confer invasiveness in social insects by increasing the rates of colony growth and spread (Moller 1996, Tsusui andSuarez 2003). Loss of genetic diversity (Tsusui and Suarez 2003, Suarez et al 2008, Ugelvig and Cremer 2012 and shifts in colony structure (Wilson et al 2009) are also related to sustained rapid growth and dispersal of invasive social insects. This is thought to be the case because large supercolonies can be formed from many genetically similar individuals, making the colony more successful.…”

“…Recognition cues Invasive insects are more chemically similar than natives (Errard et al 2005, Cremer et al 2008, Brandt et al 2009, Fournier et al 2009, Perdereau et al 2011; Invasive insects are more genetically similar than native insects (Tsusui and Suarez 2003, Suarez et al 2008, Ugelvig and Cremer 2012 A, E, O Colony longevity Shift from small, annual colony to large, perennial colony can increase invasion success (Wilson et al 2009) E, O Queen characteristics Queen longevity Queen longevity is greater in invasive insects than in natives (Gamboa et al 2002) O Queen number Invasive insects have more queens per nest than natives (Ross et al 1996, Tsusui and Suarez 2003, Abril et al 2013;…”