J Behav (2019) 32:243–251 https://doi.org/10.1007/s10905-019-09730-z

Reproduction and Offspring Sex Ratios Differ Markedly among Closely Related Hyperparasitoids Living in the Same Microhabitats

Jeffrey A. Harvey & Lucas de Haan & Oriol Verdeny-Vilalta & Bertanne Visser & Rieta Gols

Received: 2 May 2019 /Revised: 2 October 2019 /Accepted: 12 October 2019 /Published online: 25 October 2019 # The Author(s) 2019

Abstract Closely related species in nature usually ex- times higher in G. proximus than in G. agilis with hibit very similar phylogenetically conserved traits, such G. hortensis producing intermediate numbers of off- as reproduction, behavior and development. Here, we spring. All three species depleted their teneral reserves compared fecundity schedules, lifetime reproductive during their lives. Females of G. proximus and success and offspring sex ratios in three congeneric G. hortensis lived significantly longer than females of facultative hyperparasitoid wasps that exhibit several G. agilis.OffspringsexratiosinyoungG. proximus overlapping traits and which co-occur in the same mothers were female-biased and marginally male- small-scale habitats. agilis, G. proximus and biased in G. hortensis. As mothers aged, however, the G. hortensis are abundant in meadows and forest edge ratio of male:female progeny produced rapidly in- habitats in the Netherlands. is asexual (all creased until no daughters emerged later in life. Our female), whereas the other two species reproduce sexu- results reveal significant differences in reproductive ally. Here they developed on cocoons of the primary traits among the three species despite them co- parasitoid .Whenprovidedwithun- occurring in the same microhabitats, being very closely limited hosts, lifetime reproductive success was three related and morphologically similar. The increase in the production of male progeny by Gelis mothers over time suggests a depletion in sperm number or viability with J. A. Harvey (*) Department of Ecological Science, Section Ecology, VU age. This is especially interesting, given that Gelis spe- University Amsterdam, Amsterdam the Netherlands cies are among the least fecund parasitoids thus far e-mail: [email protected] studied. It is likely that in the field most Gelis mothers are probably only able to parasitize a few hosts and to J. A. Harvey : L. de Haan Department of Terrestrial Ecology, Netherlands Institute of maintain the production of female offspring. Ecology, Droevendaalsesteeg 10 6708 PB Wageningen The Netherlands Keywords Realized lifetime fecundity. Longevity. O. Verdeny-Vilalta Gelis . . Secondary parasitoids Ynsect, Rue Pierre Fontaine 1 Évry France

B. Visser Evolutionary Ecology and Genetics Group, Biodiversity Research Introduction Centre, Earth and Life Institute, UC Louvain, Croix du Sud 4 1348 Louvain-la-Neuve Belgium Phylogeny and phylogenetic constraints are central to R. Gols our understanding of ecology and evolutionary biology Laboratory of Entomology, Wageningen University, (McKitrick 1993). Phylogeny describes the evolution- Droevendaalsesteeg 1 6708 PB Wageningen The Netherlands ary history and ecophysiological relationships among 244 J Insect Behav (2019) 32:243–251 groups of organisms (Gould, 1977; Nei and Kumar reproductive capacity by a difficulty in finding many 2000). In nature, closely related species generally ex- food plants and therefore invests more metabolic re- hibit traits that very strongly reflect their phylogeny, sources in maintenance than in egg production, allowing such as morphology, reproduction and development it to extend its lifespan in searching for suitable plants on (Cheverud et al. 1985;Blombergetal.2003). Conse- which to oviposit. quently, closely related species generally exhibit a suite Parasitic wasps, or ‘parasitoids’, are model organ- of traits that overlap and which are functionally special- isms for addressing a range of questions in evolutionary ized (West-Eberhard, 1986). Phylogenetic constraints biology. Parasitoids lay their eggs inside or on the bod- are defined as components or aspects of a lineage that ies of other (‘hosts’) and their larvae grow prevent or impede any anticipated form of evolution in and develop by feeding on host tissues, whereas the that lineage (McKitrick 1993). In other words, a con- adult stage is free-living (Godfray 1994). The develop- straint affects the potential of a species to evolve radical ment of parasitoid offspring is dependent on resources changes in its biology and/or ecology from its ancestors contained in a single host: because hosts of many para- and close relatives and may hinder a species attempting sitoids are only marginally bigger than the parasitoid to exploit novel resources or colonize novel habitats. For itself, they are under intense selection to optimize the instance, in many families of the Hymenoptera exploitation of limited resources to vital metabolic func- (Aculeata) the ovipositor, which is a specialized egg- tions (Harvey 2005; Jervis et al. 2008). By contrast, laying apparatus, has evolved into a stinger that instead selection for resource allocation to different metabolic of eggs injects venom into potential prey or as a means functions in predators is generally much more of defense against attackers (Zhao et al. 2015). A stinger relaxed, because they are not restricted to a single prey is of much more utility than an ovipositor for a social item. For this reason, parasitoids exhibit a suite of traits wasp, because the workers are sterile and do not repro- that are adapted for exploiting a narrow range of host duce. In vertebrates, woodpeckers possess sharp, point- species in nature, whereas most predators will attack ed bills for chiseling wood for nest construction and many prey species in order to reach maturity. foraging, and long, barbed tongues made up of cartilage Parasitoids that are closely related and/or exhibit and bone for catching embedded in trees (Bock similar host ranges in nature often exhibit a convergence 1999;Zhouetal.2009). These adaptations are specifi- in traits such as host utilization and reproduction (Jervis cally tailored for nesting in forest habitats and would et al. 2008). This is because of both phylogenetic con- clearly be of little utility in grasslands. servatism and overlapping selection pressures on trade- Phylogeny is not the only factor constraining organ- offs such as between maintenance and egg production. isms in nature. All species are also constrained in their One of the best examples on how host ecology drives ability to allocate limited metabolic resources for vital similarities and differences in parasitoid traits is a study functions such as reproduction, foraging and survival by Price (1972), who compared parasitoids attacking (Roff 2002). Under strong selection for the acquisition, different stages of the Jack pine sawfly, Neodiprion utilization and allocation of these resources to different swaineii. He found that parasitoids attacking early host and potentially competing fitness functions, the optimal stages, such as young larvae, exhibited traits such as the phenotype of most organisms is determined by trade- production of large numbers of small eggs that could be offs in life-history traits such as between reproduction oviposited rapidly and adults that had short lifespans. and longevity (van Noordwijk and de Jong 1986). A By contrast, parasitoids attacking older hosts, such as trade-off occurs when two fitness-related traits are lim- pupae, produced small numbers of large eggs that took a ited by the same resource, such as time and/or energy, considerable time to lay and adults that had extended that can only be utilized once (Stearns 1989). For ex- lifespans. He attributed these differences to variation in ample, an organism that invests a disproportionate mortality risks experienced by hosts along their ontoge- amount of metabolic resources towards early reproduc- netic continuum with high fecundity being an adaptive tion will invariably experience a reduction in its life response in parasitoids attacking comparatively abun- expectancy and vice-versa. Trade-offs strongly reflect dant young hosts with high mortality risks, and lower environmental limitations on food, prey, mates and other fecundity for parasitoids attacking scarce older hosts factors. Thus, a specialized herbivore that feeds on a rare with a lower mortality risks (Price 1972; see also or small species of plant may be limited in its Pexton and Mayhew 2002). Differences in reproductive J Insect Behav (2019) 32:243–251 245 investment and longevity also appear to reflect host of primary parasitoids (Cotesia spp.) in the field (Lei abundance (Price 1972). and Hanski 1997; van Nouhuys and Hanski 2000; Sex determination in parasitoids is haplodiploid, Harvey et al. 2014; Heinen and Harvey 2019). Thus where unfertilized (haploid) eggs develop into males far 280 species of Gelis have been described (Catalogue and fertilized (diploid) eggs develop into females. This of Life, 2019), although there are certainly many more gives females the choice of deciding what sex to lay as the genus is not well-studied. during oviposition. In parasitoids, numerous studies We compared fecundity schedules, lifetime reproduc- have shown that mothers prefer to oviposit daughters tive success and offspring sex ratios in the three Gelis on larger hosts of perceived higher quality, and sons on species when reared on cocoons of the gregarious para- smaller hosts (Charnov et al. 1981;Charnov1982;King sitoid, Cotesia glomerata L. (Hyemoptera: Braconidae). 1987, 1989). This is because eggs are typically more Previous work with different Gelis species, including costly to produce than sperm, with large females gaining the wingless G. acororum and the fully winged much higher fitness returns than large males (Jervis et al. G. areator, reported significant interspecific differences 2008). Importantly, offspring sex ratios in parasitoids in in fecundity schedules over two day periods and lifetime the field are dependent on more than host quality, such reproductive success, especially between the winged as population-related factors. For example, when plenty and wingless gelines. Furthermore, sex ratios in both of resources are available, mating patterns in parasitoid species were highly male-biased throughout reproduc- populations generally select for equal parental invest- tive life (Visser et al. 2014, 2016). The authors specu- ment into both sexes. However, when vital resources, lated that the male bias was attributable to anticipation such as mates or hosts, are scarce or limiting, increased of limited hosts in nature by both parasitoids, with a competition can generate conditions that bias sex ratios high production of males reducing competition for these in the direction of either sex (King 1987; Visser et al., scarce hosts among the low number of remaining fe- 2016). males (Visser et al. 2014). Given that the three species In this study we examined development and repro- studied here are all wingless, we hypothesize that ductive strategies in three congeneric species of parasit- reproduction and longevity among them will be more oids. Gelis agilis Fabricius, G. proximus Forster and similar than among the gelines in the Visser et al. (2014, G. hortensis Christ (Hymenoptera: Ichmeumonidae) 2016) studies. We also discuss how these several are three species of facultative hyperparasitoids that closely-related species exhibiting overlapping traits are are virtually morphologically and behaviorally indistin- able to co-exist locally at small scale in nature. guishable, apart from differences in cuticle color. The three species exhibit a suite of overlapping traits that are phylogenetically conserved. These include (1) the pro- Methods and Materials duction of large, yolky anhydropic eggs that are only produced in small numbers daily (Jervis & Kidd 1986). Insects (2) Obligate host-feeding behavior among adult females to secure proteins for oogenesis (Jervis and Kidd, 1986; All insects were reared at a temperature of 22 +2°C Heimpel and Collier 1996). (3) Complete synovigeny under a 16:8 h L:D regime with a relative humidity of where adult females emerge with no mature eggs (Jervis 50%. Cultures of the parasitoid C. glomerata and its et al. 2001). (4) Ectoparasitic idiobisis, whereby eggs host, the large cabbage white butterfly P. brassicae, are laid by female parasitoids on the body surface of were obtained from insects reared at Wageningen Uni- paralyzed hosts (Mayhew and Blackburn, 1999). (5) versity (WUR), the Netherlands, that were originally Wingless adults, which contrasts with most parasitoid collected from agricultural fields in the vicinity of the taxa that are fully winged (Schwarz and Shaw 1999; University. All C. glomerata cocoons used in this ex- Harvey et al. 2018). Despite these overlapping traits, the periment were generated from P. brassicae caterpillars three species successfully co-occur in grassy meadow reared on Brassica oleracea var. Cyrus (Brussels and forest edges across much of Eurasia, including the sprouts) at the Netherlands Institute of Ecology (NIOO, Netherlands. Little is known about the ecology or host Wageningen, The Netherlands). range of most gelines, although previous work has In the field, C. glomerata females generally oviposit shown that the three species studied here attack cocoons between 10 and 40 eggs into first (L1) to third (L3) 246 J Insect Behav (2019) 32:243–251 instars of P. brassicae. Fully grown parasitoid larvae sex ratios over time and longevity. The experiment was emerge from the host caterpillar late during its final repeated with 10 females of each species. In order to instar, spinning cocoons adjacent to the host, which measure longevity for female wasps without host access perishes within a few days. Once weekly, several hun- (=control), the procedure was repeated with 10 females dred L2 P. brassicae larvae were presented to of each species in Petri dishes without host access. To C. glomerata in rearing cages (30 × 30 × 30 cm) for measure male longevity, the procedure was repeated in parasitism. Parasitized caterpillars were then transferred Petri dishes with 10 males each of the sexual species to steel and plexiglass cages (30 × 30 × 60 cm) contain- G. proximus and G. hortensis. ing cabbage plants. Fresh parasitoid cocoons were col- lected from these cages. Adult G. agilis, G. proximus and G. hortensis were Statistics collected from cocoons of C. glomerata that had been pinned onto the lower shoots and stems of black mustard All statistics were performed using IBM SPSS Statistics (Brassica nigra)orgarlicmustard(Alliaria petiolata)at (IBM Corp. Released 2017. IBM SPSS Statistics for several locations in the provinces of Gerlderland and Windows, Version 25.0. Armonk, NY: IBM Corp). To South Holland, the Netherlands. Species identification compare total number of offspring and longevity of was made by Dr. Martin Schwarz, one of the world’s females provided with hosts, we used general linear leading experts on the Cryptinae, who is based at the model ANOVAs with species as main factor. Offspring Biologiezentrum in Linz, Austria. A recent phylogenetic numbers were log-transformed to meet assumptions of reconstruction of the three geline species is shown in equal variance. If the effect of species was significant, Harvey et al. (2018). means were compared using Tukey multiple compari- Each species was therefore obtained from multiple son tests (Fig. 1). populations that were reared collectively. In culture, hyperparasitoids were maintained exclusively on fresh cocoons of C. glomerata. After adult emergence, each species was separately kept in closed, meshed rearing Results cages (30 × 30 × 30 cm) with honey and water and stored at 10 + 1 °C in incubators. Fecundity Schedules and Lifetime Reproductive Success in the Three Geline Wasps Fecundity Schedules, Lifetime Reproductive Success, Longevity and Sex Allocation Total offspring numbers differed among the three spe-

cies (F2,26 =15.5,p < 0.001), with G. proximus produc- Newly emerged females of G. proximus and ing most offspring (126.7 ± 14.5, mean ± 1SE), follow- G. hortensis were sexed, fed with honey and allowed ed by G. hortensis (87.5 ± 9.2) and G. agilis producing to mate with males in Petri dishes (8 cm dia.). After the fewest total offspring (41.9 ± 4.5) (Fig. 2). Total mating, which was ascertained visually, females were reproduction was also reflected in the fecundity sched- transferred to new Petri dishes (12 cm dia.) containing ules of the three species. Gelis agilis had a pre- 10 cocoons of <12 h-old C. glomerata with drops of oviposition period after eclosion of several days and honey smeared on the underside of the lid and water then typically produced a maximum of ~ 2 progeny absorbed into a small ball of cotton wool. Every 48 h every two days until this declined around day 50. By cocoons were removed and placed in marked vials with contrast, G. hortensis had the shortest pre-ovipositon the species, female number, dates, and days of exposure period of the three species and produced a maximum marked on the vials. Fresh cocoons, honey and water of ~ 3–4 progeny every two days which dropped off were presented to female wasps in new Petri dishes. rapidly after around 35 days. Lastly, the pre-ovipositon This procedure was repeated throughout the lives of period of G. proximus was intermediate in length and female wasps. Vials were checked daily for adult eclo- this species also produced ~ 3–4 progeny every two sion and newly emerged wasps were sexed and counted. days, but the decline in progeny production was much These data make it possible to determine fecundity more gradual than in G. hortensis, and also dropped off schedules of the three wasps, total fecundity, offspring sharply only after around 90 days (Fig. 3). J Insect Behav (2019) 32:243–251 247

(a) shift from the production of female to male offspring later in reproductive life than in G. hortensis.

Discussion

Females of the three Gelis species are morphologically similar, aside from differences in the color of their cuticle (Fig. 1). Despite these similarities, we found that (b) there were interspecific differences in fecundity sched- ules and lifetime reproductive success among the three species. Total progeny production was significantly lower in G. agilis than in the other two Gelis species; female G. proximus produced three times as many prog- eny as G. agilis females, with G. hortensis producing intermediate numbers of progeny. Moreover, despite the fact that the three species only produce eggs in small numbers, a peak in mean number of progeny produced (c) over two days was higher in G. proximus and G. hortensis (~ 3–4) than in G. agilis (~ 1–2). However, progeny production declined in G. hortensis somewhat more rapidly than in G. proximus. Longevity among females provided with hosts did not differ significantly among the three gelines. Our study shows that there are both interspecific similarities and differences among the three gelines in terms of trait expression. Traits like behavior, general Fig. 1 Adult females of Gelis agilis (a), Gelis proximus (b) and Gelis hortensis (c) parasitizing cocoons of Cotesia glomerata appearance (morphology, winglessness) and physiology (ectoparasitism, host-feeding and the production of small numbers of large, yolky eggs) were present in all Longevity three species and are typical among most species in the (Schwarz and Shaw 1999). However,

Although G. agilils tended to have a shorter lifespan 160 r B than the other two species, the longevity of females e

p 140 provided with hosts did not statistically differ among y

n 120 them (F =2.26, p =0.12,Fig. 4). Each of the three e 2,26 g B

o 100 species lived on average between 80 and 120 days. At r p

l 80

the upper end of the longevity distribution, some a female t

o 60

G. proximus females lived for almost 6 months. t A

n 40 a e 20 Sex ratios M 0 G. agilis G. hortensis G. proximus Overall sex ratios did not differ between the two sexu- Species ally reproducing species, G. proximus and G. hortensis Fig. 2 Mean total progeny (± SE) produced by females of Gelis (F1, 18 = 1.30, p = 0.270), but allocation of male and female progeny did differ throughout the life of each agilis, Gelis proximus, and Gelis hortensis. Data from 10 adult females for G. proximus and G. hortensis and 9 adult females for species (Likelihood Ratio Test = 19.33, p < 0.0001; G. agilis. Bars with different letters are statistically different Fig. 5). In G. proximus there was a much more dramatic (Tukey tests, p <0.05) 248 J Insect Behav (2019) 32:243–251

Fig. 3 Fecundity schedules (± a) SE) of (a) Gelis agilis (b) Gelis hortensis (c) Gelis proximus. Data 6 from 10 adult females for Gelis agilis G. proximus and G. hortensis and 5 9adultfemalesforG. agilis 4

3

2

1

0 0 20 40 60 80 100 120 140

) b) s

y 6 a

d Gelis hortensis

2 5 / e l

a 4 m e f

/ 3 # (

g 2 n i r

p 1 s f f

o 0 f

o 0 20 40 60 80 100 120 140 r e c) b m u 6 Gelis proximus N 5

4

3

2

1

0 0 20 40 60 80 100 120 140

Female age (days post emergence) differences in longevity and reproduction, although sub- extrinsic) abilities, with the better competitor producing tle when compared with many more distantly related less offspring (Harvey et al. 2013). On the other hand, parasitoids (e.g. koinobionts) were nevertheless ob- differences in reproduction may simply reflect marginal served. This suggests that selection on these traits differs differences in host range or else some aspect of niche among the three species. It is difficult to understand differentiation. Gelis spp. are generalists and can prob- what these divergent selection pressures might be, al- ably attack a range of hosts in nature (in addition to the though trade-offs may be involved. For instance, Gelis cocoons of other parasitoids). However, the lack of species may differ in their competitive (intrinsic and wings in most gelines probably limits the number of J Insect Behav (2019) 32:243–251 249

160 competitive edge for access to potentially limiting hosts 140 in the field. This argument assumes, however, that adult )

s 120

y cohorts of different Gelis species strongly overlap tem- a

d 100

( porally and that host availability decreases rapidly over y

t 80

i time. Consequently, the first daughters that emerge have v

e 60 the greatest chance of exploiting hosts before they are g

n depleted. This scenario is highly unlikely because o 40 L 20 gelines are long-lived and there are probably no discrete 0 generations in nature but a constant turnover of wasps as G. agilis G. hortensis G. proximus long as hosts are available. In another laboratory exper- iment, Visser et al. (2014) reported male-biased sex Species ratios throughout life in two other Gelis species, the Fig. 4 Mean longevity (± SE) of females of Gelis agilis, Gelis wingless G. acororum and the winged G. areator.The proximus, and Gelis hortensis when provided with hosts. Data from 10 adult females for G. proximus and G. hortensis and9adult authors attributed the male bias in these species to a females for G. agilis perceived scarcity of hosts in the field, meaning that just enough daughters are produced to diffuse competition suitable hosts they are able to find and parasitize in the among the parasitoids. field. In spite of this, in the. The second and more likely explanation is that Netherlands, the three species studied here co-occur G. proximus and G. hortensis are sperm-limited and in the same habitats with at least two other morpholog- thus deplete their sperm stores abruptly. For many years ically similar species, G. acororum and G. spurius,and it was assumed that eggs are much more limiting than perhaps more (Harvey et al. 2014). sperm in parasitoids, and this notion was often used as Offspring sex ratios in G. proximus and G. hortensis the basis of optimization models for sex allocation strat- were highly variable among individual females, at least egies in these insects (Charnov 1982;King1987, 1989; during the first several weeks of reproductive life. In Visser 1994;Mackauer,1996). However, it has more most G. hortensis females, offspring sex ratios favored recently been revealed that many female parasitoids the production of sons over this time (>70%), whereas in mate only once in their lifetimes and store low numbers G. proximus ca. 60% of progeny were daughters. How- of sperm (Henter 2004;Boivinetal.2005;Boivin ever, in both species there was an abrupt shift from the 2013). If males inseminate females with just enough production of mixed sex to all-male offspring after about sperm to produce daughters early in reproductive life, 40 days, leading to the production of all-male progeny this may imply that Gelis spp. will only ever encounter later in life. There are two possible explanations. The small numbers of hosts and that the sudden switch to all- first, and less likely, is that sperm is unlimited, but that male progeny is an artefact: in nature, no females there- females produce more daughters early to gain a fore survive long enough to encounter enough hosts to

Fig. 5 Sex allocation patterns G. hortensis G. proximus (proportion of males, mean ± SE) during life of Gelis hortensis 1,0 s

(blue line) and Gelis proximus d o i

(orange line). Sex ratios were r 0,8 e

determined for progeny produced p by 10 females of each species in y 0,6 a consecutive 6-day intervals d 6

( 0,4 s o i t 0,2 a r x

e 0,0 S- ) 0 20 40 60 80 100 120 Female age ( days post emergence) 250 J Insect Behav (2019) 32:243–251 deplete their sperm. What is remarkable in G. proximus Data Accessibility Upon acceptance of the manuscript all data and G. hortensis is that the switch from mixed broods to will be archived in the Dryad Respository. all-male progeny occurred when females had only laid Compliance with ethical standards around 50 or so eggs – much lower than in other parasitoids so far studied. However, given that suitable Conflict of interests The authors declare that they have no hosts are probably scarce it is unlikely that females ever conflicts of interest. exhaust their supply of sperm in nature. Our experimen- ‘ ’ tal females thus experienced a jackpot of hosts that far Open Access This article is distributed under the terms of the exceeds what females would normally ever encounter. Creative Commons Attribution 4.0 International License (http:// Males thus inseminate just enough sperm to ensure that creativecommons.org/licenses/by/4.0/), which permits unrestrict- females do not become sperm-depleted. ed use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, Given that at least several Gelis species are found in provide a link to the Creative Commons license, and indicate if the same microhabitats, an interesting question is how changes were made. multiple species that presumably compete for hosts at small, local scales can co-exist. One important assump- References tion in ecology is that co-existing species differ in their niches (Adler et al., 2007) and that intense competition Adler PB, HilleRisLambers J, Levine JM (2007) A niche for among similar species for the same resources, such as neutrality. Ecol Lett 10:95–104 hosts by parasitoids, will lead to competitive exclusion Bezant ET (1956) Gelis micrurus Forster (Hymenoptera: of others by a dominant species (Harvey et al. 2013; ) parasitising a lycosid spider egg sac. Pekas et al. 2016). Co-existence theory has been posited Entomol Month Mag 92:106 Blomberg SP, Garland T, Ives AR (2003) Testing for phylogenetic as a framework to better understand how species with signal in comparative data: behavioral traits are more labile. strongly overlapping traits can co-exist in ecologically Evolution 57:717–745 similar environments (Leibold and McPeek, 2006). This Bock WJ (1999) Functional and evolutionary morphology of – theory may partly explain niche differentiation among woodpeckers. Ostrich 70:23 31 Boivin G, Jacob S, Damiens D (2005) Spermatogeny as a life- species with overlapping traits. One important factor history index in parasitoid wasps. Oecologia 143:198–202 that may enable multiple Gelis species to co-exist local- Boivin G (2013) Sperm as a limiting factor in mating success in ly is that they are extreme generalists, parasitizing what- Hymenoptera parasitoids. Entomol Exp et Appl 146:149– ever suitable hosts are available. Although the biology 155 Catalogue of Life (2019) 2019 Annual Checklist. Gelis of most Gelis species is unknown, other species in this http://www.catalogueoflife.org/col/browse/tree/id/7555800 genus parasitize a wide range of hosts including spider b1216a3f5e8e4e740288c8463 egg sacs and moth pupae in addition to parasitoid co- Charnov EL, Los-den Hartogh RL, Jones WT, van den Assem J coons (Bezant 1956; Schwarz & Boriani 1994; Cobb (1981) Sex ratio evolution in a variable environment. Nature – and Cobb 2004). They may also differ in other, more 289:27 33 Charnov EL (1982) The Theory of Sex Allocation. Volume 18. subtle ways that diffuse competition. 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Princeton University Press Gould SJ (1977) Ontogeny and Phylogeny. Harvard University Press Acknowledgements The authors with to thank Arjen de Jong Harvey JA (2005) Factors affecting the evolution of development for help in collecting gelines in the field. Photos of the gelines in strategies in parasitoid wasps: the importance of functional Fig. 1 are by Tibor Bukovinszky. Roel Wagenaar is thanked for the constraints and incorporating complexity. Entomol Exp Appl rearing of Cotesia glomerata and the three Gelis species. 117:1–13 J Insect Behav (2019) 32:243–251 251

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