Spatial Nest‐Settlement Decisions in Digger Wasps: Conspecifics Matter more than Heterospecifics and Previous Experience

Abstract

Research into the driving forces behind spatial arrangement of wasp nests has considered abiotic environmental factors, but seldom investigated attraction or repulsion towards conspecifics or heterospecifics. Solitary female digger wasps (Hymenoptera) often nest in dense aggregations, making these insects good models to study this topic. Here, we analysed the nesting patterns in an area shared by three species of the genus Bembix, in a novel study to discover whether female wasps are attracted to or repulsed by conspecific nests, heterospecific nests or their own previously established nests when choosing nest‐digging locations. Early in the season, each species showed a clumping pattern of nests, but later in the season, a random distribution of nests was more common, suggesting an early conspecific attraction. Such behaviour was confirmed by the fact that females started building their nests more frequently where other females of their species were simultaneously digging. The distances between subsequent nests dug by individual females were shorter than those obtained by random simulations. However, this pattern seemed to depend on the tendency to dig close to conspecifics rather than remain in the vicinity of previous nests, suggesting that females' experience matters to future decisions only on a large scale. Nesting patches within nest aggregations largely overlapped between species, but the nests of each species were generally not closer to heterospecific nests than expected by chance, suggesting that females are neither repulsed by, nor attracted to, congenerics within nest aggregations. A role of the spatial distribution of natural enemies on the observed nesting patterns seemed unlikely. Bembix digger wasp nest aggregations seem thus to be primarily the result of female–female attraction during nest‐settlement decisions, in accordance with the ‘copying’ mechanisms suggested for nesting vertebrates.

Vespa velutinanest distribution at a local scale: An 8‐year survey of the invasive honeybee predator

“…First, in 2007, the distribution of nests was regular, which was most likely caused by a statistical artefact of the small sample size (4 nests) and not because of biology. Second, in 2009, the nests were distributed as aggregates; and aggregated patterns are caused, for example, by philopatry (Polidori et al, 2006), group protection against parasites and/or predators (Antonini et al, 2003;Rosenheim, 1990), or intraspecific attraction and/or increased mating probability (Oldroyd et al, 1995;Wattanachaiyingcharoen et al, 2003;Paar et al, 2004;Polidori et al, 2008;Tanner & Keller, 2012;Asίs et al, 2014). For V. velutina, the pressure from parasitism and/or predation as a driver of nest aggregation was unlikely, because this invasive species has few natural enemies, many of which remain anecdotal (see Monceau et al, 2014;Darrouzet et al, 2015;Villemant et al, 2015).…”

“…Instead, conspecific attraction and/or philopatry might be involved (Edwards, 1980). Conspecific attraction occurs in different hymenopteran species such as honeybees (Oldroyd et al, 1995), ants (Tanner & Keller, 2012) and solitary wasps (Asίs et al, 2014). Therefore, the V. velutina foundresses might use the occurrence of conspecifics as a cue to indicate, for example, nesting site quality.…”

“…We believe this study is valuable for several different reasons. First, the analysis of the distribution of nests is commonly used in central place foragers such as V. velutina to examine population dynamics; several studies with ants (Kenne & Dejean, 1999;Schooley & Wiens, 2003;Tanner & Keller, 2012), wasps (Polidori et al, 2008;Asίs et al, 2014) and bees (McNally & Schneider, 1996;Potts & Willmer, 1998;Rinderer et al, 2002;Baum et al, 2005) were released that provided important information about population regulation and dynamics. In this study, for the first time, we provided information on the nesting patterns of V. velutina and on the evolution of the nesting pattern in the years since the beginning of the invasion.…”

Complex-to-Predict Generational Shift between Nested and Clustered Organization of Individual Prey Networks in Digger Wasps

“…Nevertheless, in the studied aggregation nest density was not higher in 2009 [46], and neither was mass variance of the females lower in that year, in such a way that the organization of the females in 2009 seems not to be influenced by such traits.…”

Differential distribution of resources for females on a dioecious plant affects the small–scale distribution of male of an oligolectic bee

“…1). The small observed nest aggregation departed from the more common trend of a clumped arrangement of nests observed in fossorial bees and wasps (Potts and Willmer, 1998;Polidori, 2017;Polidori et al, 2008;Asís et al, 2014). However, at least a couple of Andrena species (A. wilkella (Kirby, 1802) and A. nigroaenea (Kirby, 1802)) were also observed nesting in a random pattern in loose aggregations (Tengö et al, 1990;Schiestl and Ayasse, 2000).…”