Journal of Comparative Physiology A https://doi.org/10.1007/s00359-021-01492-4

ORIGINAL PAPER

Neuroanatomical diferentiation associated with alternative reproductive tactics in male arid land , Centris pallida and dawsoni

Meghan Barrett1 · Sophi Schneider2 · Purnima Sachdeva1 · Angelina Gomez1 · Stephen Buchmann3,4 · Sean O’Donnell1,5

Received: 1 February 2021 / Revised: 19 May 2021 / Accepted: 22 May 2021 © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2021

Abstract Alternative reproductive tactics (ARTs) occur when there is categorical variation in the reproductive strategies of a sex within a population. These diferent behavioral phenotypes can expose to distinct cognitive challenges, which may be addressed through neuroanatomical diferentiation. The dramatic phenotypic plasticity underlying ARTs provides a powerful opportunity to study how intraspecifc nervous system variation can support distinct cognitive abilities. We hypothesized that conspecifc animals pursuing ARTs would exhibit dissimilar brain architecture. Dimorphic males of the species Centris pallida and Amegilla dawsoni use alternative mate location strategies that rely primarily on either olfaction (large-morph) or vision (small-morph) to fnd females. This variation in behavior led us to predict increased volumes of the brain regions supporting their primarily chemosensory or visual mate location strategies. Large-morph males relying mainly on olfaction had relatively larger antennal lobes and relatively smaller optic lobes than small-morph males relying primarily on visual cues. In both species, as relative volumes of the optic lobe increased, the relative volume of the antennal lobe decreased. In addition, A. dawsoni large males had relatively larger mushroom body lips, which process olfactory inputs. Our results suggest that the divergent behavioral strategies in ART systems can be associated with neuroanatomical diferentiation.

Keywords Alternative mating tactics · Sensory diferentiation · Solitary bees

Introduction , and include both behavioral and morphological trait variation (Shuster and Wade 2003; Paxton 2005; Oliveira Alternative reproductive tactics (ARTs) occur when there is et al. 2008; Shuster 2010). ARTs evolve when ftness gains categorical variation in the mating-related behaviors or traits can be achieved by pursuing divergent mating strategies, of same-sex individuals within a population (Oliveira et al. leading to selection on phenotypes that maximize the suc- 2008). ARTs have evolved in diverse taxa, including cess of two or more specialized morphs (Shuster 2010). fsh, crustaceans, birds, amphibians/reptiles, mammals, and Because morphs often develop via phenotypic plasticity, ARTs allow for the study of behavioral and morphological * variation within a population that are not dependent upon Meghan Barrett genotypic diferences (Kukuk 1996; reviewed in Oliveira [email protected] et al. 2008). In this way, ARTs provide a unique and pow- 1 Department of Biology, Drexel University, Philadelphia, PA, erful opportunity to explore the evolution of relationships USA between behavioral and morphological specialization. 2 Upper Dublin, PA, USA Neuroecology theory predicts that relative investment in 3 Department of Entomology, University of Arizona, Tucson, functionally discrete regions of the brain will be correlated AZ, USA to the cognitive demands of an organism’s environment/ 4 Department of Ecology and Evolutionary Biology, University behaviors, due to constraints imposed by the high meta- of Arizona, Tucson, AZ, USA bolic cost of producing and maintaining neural tissue (Aiello 5 Department of Biodiversity, Earth, and Environmental and Wheeler 1995; Sherry 2006; Liao et al. 2016; Niven Science, Drexel University, Philadelphia, PA, USA 2016; Luo et al. 2017). Energy limitation thus places neural

Vol.:(0123456789)1 3 Journal of Comparative Physiology A systems under selective pressure for optimal investment chase after females ‘upwind’ of them, as males are oriented (Niven and Laughlin 2008). Because successful mate loca- 360° around the vegetation—not just on the downwind side— tion behaviors are expected to be strongly linked to repro- and always orient facing the largest open area visually, away ductive success, diferent sensory mate location strategies from the vegetation and not necessarily into the wind (Barrett, could be associated with neuroanatomical diferentiation in personal observation). the regions of the brain that support those sensory systems. Similarly, the large ‘majors’ of A. dawsoni exhibit a fxed We hypothesized that conspecifc animals utilizing ARTs strategy, patrolling female emergence sites and likely using would have diferent brain architecture patterns, related cuticular hydrocarbon cues to locate females waiting within to the cognitive demands of their morph-specifc mating emergence tunnels, before fghting other males and/or guard- behaviors. ing potential mates (Alcock 1997; Simmons et al. 2003). The male morphs of Centris pallida Fox, found in the Smaller A. dawsoni ‘minor’ males rarely patrol emergence Sonoran Desert of the USA and Northern Mexico, and sites, instead typically hovering or patrolling near blooming Amegilla dawsoni Rayment (Dawson’s burrowing bee), host plant vegetation and use visual cues to locate females found in the deserts of Western Australia, use alternative (Houston 1991; Alcock 1997). sensory mate location strategies. In C. pallida, large-morph In summary, the large-morph males (e.g. metanders or males are morphologically distinct based on coloration and majors) of both species are behaviorally fxed on using chem- hind leg morphology (called ‘metanders’ with ‘swollen’ legs osensory cues to locate females (Alcock et al. 1977; Alcock in Snelling 1984 or ‘largest males’ in Alcock et al. 1977). 1997; Simmons et al. 2003), while the small-morph males are These males have a fxed mate location strategy, using che- more behaviorally fexible but rely more heavily on visual cues mosensory cues to patrol close to the soil surface in search to locate mates when hovering. We predicted brain structure for females buried underground. Males land near buried would difer between the male morphs in both species, with females and repetitively touch the soil with their antennae relative increases in tissue investment in brain regions that (typical odor-tracking behavior on a surface; Wenner support mating-tactic relevant cognitive abilities. 1974), before digging up the buried female (Alcock et al. We analyzed whether relative brain investment patterns 1977). Chemosensory cues are both sufcient and neces- difered between the morphs of each species in their anten- sary for locating females–males will dig up dead, buried nal lobes (AL), which receive chemosensory information females that are not moving or visible but will not dig up from the antennae, and their optic lobes (OL), which receive vibrating objects (Alcock et al. 1976). Other males will fght visual information from the eyes (Kenyon 1896). We tested with the digging male for the opportunity to mate with the for a negative correlation in investment between visual and emerging females, with the largest male typically winning olfactory brain regions, which are seen in comparative stud- and copulating with the female (Alcock 1976, 2013; Alcock ies of other insects (often described as trade-ofs: Niven et al. 1976, 1977). and Laughlin 2008, Stöckl et al. 2016; Kessey et al. 2019; In contrast to the fxed mate location strategy the large-male Özer and Carle 2020). In addition to analyzing investment morph uses, small-morph males can be behaviorally fexible. in peripheral sensory brain regions, we asked whether the They may patrol the ground like large-morph males or alter- relative volumes of the mushroom body (MB) calyces (we natively hover near vegetation, chasing after and mating with analyzed the lip and collar separately) difered between any females or mating pairs they locate visually (Alcock 1976, the morphs. The mushroom bodies are involved in learn- 1979, 1984; Alcock et al. 1977). Visual cues are likely the only ing, memory, and sensory integration, and receive olfactory or primary sensory strategy used while hovering. First, hover- input to the MB calyx lip and visual input to the MB calyx ing males chase any insect passing through their visual feld collar (Fahrbach 2006; Paulk and Gronenberg 2008). We (even those several meters away, C. pallida males, and non-C. thus predicted that the large-morph males that are fxed on pallida insects). Second, males only chase nearby hovering chemosensory cues for mate location would have relatively males when they enter their visual feld, even though they are larger MB lips and ALs, and relatively smaller MB collars often hovering less than a meter away for several hours. If and OLs, as compared with the small-morph males that rely olfaction were in use, males would detect, orient towards, and more heavily on vision but are behaviorally fexible. chase after nearby males even when not in their visual feld (e.g. drones of Apis mellifera, Brandstaetter et al. 2014). Third, male C. pallida do not discriminate between the odors of male Materials and methods or female C. pallida (when digging Alcock et al. 1976; and even in close contact, Alcock and Buchmann 1985), making it Specimen collection unlikely that they are tracking the odor of a single, fast-moving female bee in the midst of a turbulent aggregation of thousands Centris pallida males (n = 27) were collected in late April of fast-moving C. pallida males. Fourth, males frequently and early May of 2018 at Tonto National Forest in Arizona

1 3 Journal of Comparative Physiology A

Fig. 1 Characteristic coloration diference in large and small C. pallida male morphs. Large- morph (metandric; Snelling 1984) C. pallida males are a light gray coloration with ‘swollen’ hind femurs (bee on the right) while small-morph C. pallida males are a dark brown on the thorax, with thin hind femurs (bee on the left). Bees were collected in 2018, from the same population used in this study

(33.552, − 111.566). A. dawsoni males (n = 19) were col- ethanol concentrations, acetone, and then increasing con- lected on July 29, 2019 at the Carnarvon Pistol Range, West- centrations of plastic resin. Resin was composed of 5.5 g ern Australia (− 24.917, 114.725). Dense emergence and EMbed 812, 5.7 g DDSA (dodecenyl succinic anhy- nesting aggregations at both sites have persisted for several dride), 0.65 g DBP (dibutyl phthalate), and 0.31 g of DMP decades. C. pallida males were transported in a cooler on ice (2,4,6-tri(dimethylaminoethyl)phenol; all Electron Micros- to a lab where they were weighed on an analytical balance copy Sciences products). Heads were incubated at 60 °C for to the nearest 0.1 mg; males of A. dawsoni were transported 72 h inside cylindrical molds, until the resin hardened. on ice from the feld to a lab for dissection within six hours. Heads were cut along the frontal plane into 14 um thick Heads were cut from the thorax and placed immediately into sections using a rotary microtome and disposable steel his- Prefer fxative (Anatech, Ltd.) following transport (A. daw- tology blades. Sections were mounted on gelatin-coated soni) or weighing (C. pallida). microscope slides and stained with Toluidine blue stain, For C. pallida, males were classifed as the ‘large’ male then cleared in a series of distilled water, increasing ethanol morph if they were found patrolling, digging, or fghting concentrations, and Histochoice clearing medium (Sigma- and had the gray/white coloration and leg morphology dis- Aldrich) and kept in the oven at 60 °C for 4 h. Slides were tinctive to this ‘large’ behaviorally infexible morph (Fig. 1; coverslipped under DEPEX transparent mounting medium Alcock 1976; Alcock et al. 1977; Snelling 1984). They were (Electron Microscopy Sciences). classifed as ‘small’ male morphs if they were collected hov- A compound light microscope-mounted digital camera ering near vegetation, or if they were found patrolling or was used to photograph every section containing brain tissue digging but did not have the distinct morphology/coloration at 2560 × 1920 pixel resolution at 2.5× microscope objective of the large morph (Alcock et al. 1977; Snelling 1984). and a 1× camera mount. Digital photographs were taken For A. dawsoni, males were classifed as small-morph using LAS V4.9 software, with sharpness set to robust. (minor) males if they were collected near vegetation away from emergence areas. Alcock (1997) classifed emergence- Neuroanatomical measurements site patrolling males as large-morph (major) males if their head width was greater than 6.3 mm; Houston (1991) and ImageJ (Schneider et al. 2012) was used to quantify the Alcock (1997) found a distinct separation in head width area of brain regions by outlining the neuropil of the target around 6.0–6.2 mm between majors and minors. This cri- region on every other section using the freehand selections terion was used to classify large-morph males at patrolling tool, quantifying the number of pixels in the structure, and sites in our study. converting the pixel count to area using a photograph of a stage micrometer taken at the same resolution and magnif- Histological sectioning cation. We then multiplied the area by section thickness and fnally added up all the volumes across all slides to obtain Brain tissue was dissected completely out of the head total brain region volumes in cubic millimeters. We quan- capsule and dehydrated through a series of increasing tifed the following regions: mushroom bodies (calyx lip,

1 3 Journal of Comparative Physiology A calyx collar, and basal ring + peduncles together), central df = 25, p = 0.0013; A. dawsoni: n = 19, t = 2.60, df = 17, complex, central brain mass (protocerebrum, protocerebral p = 0.0188). In contrast, the large-morph males, which bridge, subesophageal ganglion), antennal lobes, optic lobes rely exclusively on a chemosensory mate location strat- (medulla and lobula only). We did not measure Kenyon body egy, had relatively larger antennal lobes (Fig. 2b; unpaired cell volumes. t test; C. pallida: t = 3.26, df = 25, p = 0.0032; unpaired t test with Welch’s correction; A. dawsoni: t = 3.38, df = 7.62, Statistical analysis p = 0.0104). Optic and antennal lobe volumes both increased as GraphPad Prism v. 8.3.0 (GraphPad Prism for Windows ROB volume increased (C. pallida, OL: y = 0.98 x + 0.13, 2018) was used for all statistical analyses and data were con- R2 = 0.71, F = 61.04, p < 0.0001, AL: y = 0.04 x − 0.003, frmed to meet the assumptions of parametric tests before R2 = 0.68, F = 54.27, p < 0.0001; A. dawsoni, OL: y = 0.54 those analyses were performed using Anderson–Darling x + 0.27, R2 = 0.40, F = 11.30, p = 0.0037, AL: y = 0.07 and Shapiro–Wilk normality tests and an F test was used to x − 0.02, R2 = 0.57, F = 22.51, p = 0.0002). However, in test for equal variance. Relative brain region volumes were both C. pallida and A. dawsoni as the relative volume of the calculated by dividing the brain region of interest by the optic increased, the relative volume of the antennal lobes total brain volume minus the brain region of interest (as in O’Donnell et al. 2018, termed Rest of Brain [ROB]). The diferences in relative brain region volumes between morphs of each species were assessed using standard unpaired t tests, except when variances were unequal in which case a Welch’s correction to the unpaired t test was used. Linear regressions were used to assess the relationship between brain region volumes, and the relationship between relative optic and antennal lobe volumes.

Results

Body size variation

Small- and large-morph C. pallida males difered in mean head width and wet body mass (unpaired t tests; head width: n = 27, t = 7.63, df = 25, p < 0.0001; body mass: t = 10.89, df = 25, p < 0.0001). Large-morph males had a minimum head width of 5.35 mm and minimum body mass of 0.25 g (ranges, head width: 5.35–6.02 mm; body mass: 0.25–0.35 g), while small-morph males had a max- imum head width of 5.27 mm and maximum body mass of 0.21 g (ranges, head width: 4.53–5.27 mm; body mass: 0.11–0.21 g). Small- and large-morph A. dawsoni males difered in mean head width (unpaired t test; n = 19, t = 13.21, df = 17, p < 0.0001). Minimum head width of large-morph males was 6.51 mm (range 6.51–7.20 mm) and the maximum head width of small-morph males was 5.86 mm (range 5.28–5.86 mm). Fig. 2 Smaller optic lobes (OL) and larger antennal lobes (AL) in C. pallida A. dawsoni. C. pallida Relative optic and antennal lobe volumes large-morph males of and a and A. dawsoni large-morph males have relatively smaller optic lobes (unpaired t tests; C. pallida: n = 27, t = 3.63, df = 25, p = 0.0013; A. The small-morph C. pallida and A. dawsoni males, which dawsoni: n = 19, t = 2.60, df = 17, p = 0.0188) and b relatively larger rely primarily on a visual mate location strategy, had rela- antennal lobes than the small-morph males of their species (unpaired t tests; C. pallida: t = 3.26, df = 25, p = 0.0032; A. dawsoni: t = 3.38, tively larger optic lobes compared with the large-morph df = 7.62, p = 0.0104). Means with error bars representative of stand- males (Fig. 2a; unpaired t tests; C. pallida: n = 27, t = 3.63, ard deviations. *p < 0.05, **p < 0.01

1 3 Journal of Comparative Physiology A decreased (Fig. 3: C. pallida, y = − 0.01 x + 0.05, R2 = 0.17, t test with Welch’s correction; MB lip: t = 1.63, df = 10.3, F = 5.22, p = 0.03; A. dawsoni, y = − 0.03 x + 0.08, R2 = 0.30, p = 0.13; MB collar: t = 0.05, df = 24.37, p = 0.96; unpaired t F = 7.24, p = 0.016). test; MB basal ring and peduncle: t = 0.10, df = 25, p = 0.92; central complex: t = 1.74, df = 25, p = 0.09). In addition, Relative volumes of other brain regions there was no relationship between the relative volumes of the optic and antennal lobes and the corresponding MB There were no signifcant diferences between the C. pallida region (C. pallida, OL-collar: R2 = 0.05, F = 1.44, p = 0.24; morphs in the relative volumes of the MB lip, collar, or basal AL-lip: R2 = 0.08, F = 2.47, p = 0.12; A. dawsoni, OL-collar: ring and peduncles, or the central complex (Fig. 4a; unpaired R2 = 0.07, F = 1.20, p = 0.29; AL-lip: R2 = 0.08, F = 1.50,

Fig. 3 Negative correlation in relative OL and AL volumes in C. pal- R2 = 0.17, F = 5.22, p = 0.031) and b A. dawsoni (y = − 0.03 x + 0.08; lida and A. dawsoni males. As relative OL volume increases, rela- n = 19, R2 = 0.30, F = 7.24, p = 0.016) males tive AL volume decreases in a C. pallida (y = − 0.01 x + 0.05; n = 27,

Fig. 4 Larger relative MB lip in A. dawsoni large-morph males; dawsoni large-morph males have relatively larger MB lips than no diferences in relative volumes of other MB regions or the cen- the small-morph males (unpaired t test; n = 19, t = 2.55, df = 17, tral complex between morphs in C. pallida or A. dawsoni. a There p = 0.0209). There are no diferences in the relative volumes of the are no signifcant diferences in the relative volumes of the MB lips, MB collars, basal ring + peduncles, or the central complex of A. collars, basal ring + peduncles, or the central complexes of C. pal- dawsoni male morphs (unpaired t test; MB collar: t = 0.40, df = 17, lida male morphs (unpaired t tests with Welch’s correction; MB lip: p = 0.70; MB basal ring and peduncle: t = 1.19, df = 17, p = 0.25; n = 27, t = 1.63, df = 10.3, p = 0.13; MB collar: t = 0.05, df = 24.37, unpaired t test with Welch’s correction; central complex: t = 1.32, p = 0.96; unpaired t test; MB basal ring and peduncle: t = 0.10, df = 9.57, p = 0.22). Means with error bars representative of standard df = 25, p = 0.92; central complex: t = 1.74, df = 25, p = 0.09). b A. deviations. *p < 0.05 1 3 Journal of Comparative Physiology A p = 0.24). There was also no relationship between the rel- manipulation of the visual environment of “Dark flies” ative volumes of the two MB regions (C. pallida, collar- (Drosophila melanogaster that had been reared in darkness lip: R2 = 0.007, F = 0.17, p = 0.69; A. dawsoni, collar-lip: since 1954, followed by 65 generations in the light) showed R2 = 0.11, F = 2.15, p = 0.16), demonstrating that the nega- a negative correlation between OL and AL volumes evolved tive correlation between sensory systems occurs only in the simultaneously in this new environment, as OL volume peripheral processing lobes. increased and AL volume decreased (Özer and Carle 2020). Amegilla dawsoni large-morph males had a relatively Closely related hawkmoth (Sphingidae) species that rely on larger MB lip region compared with the small-morph males diferent senses for foraging behavior (vision- vs. olfaction- (Fig. 4b; unpaired t test; t = 2.55, df = 17, p = 0.0209). No based) show diferentiation in both lower- and higher-order other regions of the brain difered in their relative volumes brain regions, with larger neuropil volumes to support the (unpaired t tests; MB collar: t = 0.40, df = 17, p = 0.70; MB preferred foraging method (Stöckl et al. 2016). basal ring and peduncle: t = 1.19, df = 17, p = 0.25; unpaired Dimorphic solitary male bees likely arise from difer- t test with Welch’s correction; central complex: t = 1.32, ences in nutritional quantity/quality, similar to many other df = 9.57, p = 0.22). morphologically diferentiated adult insects, as genetic dif- ferences are rarely the sole foundation for alternative repro- ductive tactics (e.g., honey bee queens and workers, other Discussion bees; Gross 1996; Kukuk 1996; Danforth and Desjardins 1999; Slater et al. 2020). Our results for C. pallida and A. Large-morph and small-morph C. pallida and A. dawsoni dawsoni are particularly interesting because they reveal males difered signifcantly in the relative volumes of their adaptively distinct brains resulting from phenotypic plastic- peripheral processing lobes, where larger relative volumes ity, not genetics. In addition, our results suggest that alterna- correlated with their morph-typical sensory mate location tive reproductive tactics without variation in reproductive strategies. As predicted, large-morph males, which rely investment (e.g. honeybee queens vs workers) are capable most heavily on olfaction to fnd mates, had relatively larger of producing divergent patterns of relative brain investment. antennal lobes; small-morph males, which rely more heavily Our results suggest that higher-order sensory brain on visual cues to fnd mates, had relatively larger optic lobes regions may be under diferential investment pressures than (Alcock et al. 1976; Alcock 1997; Simmons et al. 2003). peripheral sensory regions as, broadly, the higher-order sen- In both species, there was a negative correlation in relative sory structures were not diferent between morphs (except antennal and optic lobe investment. Optic and antennal lobe the MB lip in A. dawsoni). This suggests that brain regions volumes increased as ROB volumes increased, possibly due dealing with the same sensory information, but at difer- to the impact of allometric scaling on the brain. Morphs of ent levels of processing, may be subjected to diferential both species did not difer signifcantly in any other brain investment patterns, as seen in studies of social insect poly- region, except that in A. dawsoni the mushroom body lip morphisms (Wilczynski 1984; Gordon and Traniello 2018; (olfactory processing) was relatively larger in large-morph O’Donnell et al. 2018). Many studies of sensory systems males. Our study was not able to control for age/experience occur in relation to foraging behavior, where both input level, which has been shown to change mushroom body (lower-order) and processing/storage (higher-order) of sen- investment in numerous insects (including bees, Rehan et al. sory information may be important to animal survival (Bern- 2015). stein and Bernstein 1969; Stöckl et al. 2016). The sensory Sensory systems are adapted to the cognitive challenges mate location tactics of C. pallida and A. dawsoni may not of species’ environments and behaviors. This can gener- require as much higher-order processing or storage of infor- ate inverse tissue investment and energetic cost patterns mation as foraging behaviors. between sensory modalities, sometimes demonstrated to be Due to their large population sizes and stable aggregation trade-ofs (Barton et al. 1995; Barton 1998; Kotrschal et al. locations across decades, these bees are excellent systems 1998; Barton and Harvey 2000; Stieb et al. 2011; Montgom- for additional research on the mechanisms of intraspecifc ery and Ott 2015; Keesey et al. 2019, Sheehan et al. 2019; brain resource variation on transcriptomic, cellular, and neu- but see Gronenberg and Hölldobler 1999; O’Donnell et al. ral network levels. Our results demonstrate that intraspe- 2013). Comparative studies of species that have evolved to cifc behavioral variation is supported by diferences in live/behave in the dark (subterranean, nocturnal foragers, developmental brain region investment patterns, but how etc.) show they possess smaller visual neuropil volumes, this volumetric diference arises deserves further study. alongside other olfactory or mechanical sensory adaptations Changes in brain volume can arise through an increased (Healy and Guilford 1990; Warrant and Locket 2004; Soares number of neurons, increases in neuron size, increased den- and Niemiller 2013; Bulova et al. 2016; O’Donnell et al. dritic branching, or other changes at diferent levels of neural 2017; Tierney et al. 2017; Sheehan et al. 2019). A unique organization (reviewed in Chittka and Niven 2009; Godfrey

1 3 Journal of Comparative Physiology A and Gronenberg 2019). In addition, changes in brain volume Alcock J (2013) Role of body size in the competition for mates by Centris pallida do not necessarily translate into diferences in behavioral males of (Anthophorinae: ). South- west Nat 58:427–430 competence (Chittka and Niven 2009; van der Woude et al. Alcock J, Buchmann S (1985) The signifcance of the post-insemina- 2019). Understanding the sensory competence of dimorphic tion display by male Centris pallida (Hymenoptera: Anthophori- males in these species would provide additional intraspe- dae). Z Tierpsychol 68:231–243 cifc evidence that increased brain region volumes support Alcock J, Jones E, Buchmann S (1976) Location before emergence of the female bee, Centris pallida, by its male (Hymenoptera: increased capacity to deal with specifc sensory tasks. Future Anthrophoridae). J Zool 179:189–199 research should investigate how volumetric diferences in Alcock J, Jones E, Buchmann S (1977) Male mating strategies in the C. pallida and A. dawsoni brains manifest at other levels of bee Centris pallida Fox (Anthophoridae: Hymenoptera). Am Nat neural organization. 111:145–155 Barton RA (1998) Visual specialization and brain evolution in pri- Acknowledgements mates. Proc R Soc Lond B Biol Sci 265:1933–1937 The authors would like to thank Dan Papaj, Antio- Barton RA, Harvey PH (2000) Mosaic evolution of brain structure in nette “Toni” Roe, Kay Richter, and Kit Prendergast for feld assis- mammals. Nature 405:1055–1058 tance; Karmi Oxman, Stefan Bonestroo, Virginia Caponera, Christian Barton RA, Purvis A, Harvey PH (1995) Evolutionary radiation of Cabuslay, Rhe Congdon, Devneet Kainth, and Cheyenne McNair for visual and olfactory systems in primates, bats and insectivores. laboratory assistance; Nikolai Tatarnic and the Western Australian Philos Trans R Soc L B Biol Sci 348:381–392 Museum (Perth, Australia) for export permits from Australia to the Bernstein S, Bernstein RA (1969) Relationship between foraging ef- USA; and John Alcock, Bruce Taubert, and Leigh Simmons for nesting ciency and the size of the head and component brain and sensory site information. RA support for MRB from Drexel College of Arts and structures in the red wood ant. Brain Res 16:85–104 A. dawsoni Sciences. Buchmann acknowledges support for specimen Brandstaetter AS, Bastin F, Sandoz JC (2014) Honeybee drones are collection and preparation from National Science Foundation Grant attracted by groups of consexuals in a walking simulator. J Exp number 1929499, collection and export permits obtained through the Biol 217:1278–1285 Australian Government Department of the Environment in collabora- Bulova S, Purce K, Khodak P, Sulger E, O’Donnell S (2016) Into the tion with the Western Australia Museum (AU027; Buchmann: US174). black and back: the ecology of brain investment in Neotropical Species are not endangered nor protected. army ants (Formicidae: Dorylinae). Sci Nat 103:31 Chittka L, Niven J (2009) Are bigger brains better? Curr Biol Funding RA support to MRB from the Drexel College of Arts and Sci- 19:R995–R1008 ences. SB received support from National Science Foundation Grant Danforth B, Desjardins CA (1999) Male dimorphism in Perdita porta- number 1929499 to collect and prepare A. dawsoni specimen. lis (Hymenoptera, Andrenidae) has arisen from preexisting allo- metric patterns. Insectes Soc 46:18–28 Availability of data and materials Data archived in Dryad: https://doi.​ ​ Fahrbach SE (2006) Structure of the mushroom bodies of the insect org/​10.​5061/​dryad.​bcc2f​qzcd. brain. Ann Rev Entomol 51:209–232 Godfrey RK, Gronenberg W (2019) Brain evolution in social insects: Code availability Not applicable. advocating for the comparative approach. J Comp Physiol A 205:13–32 Gordon DG, Traniello JF (2018) Synaptic organization and division of Declarations labor in the exceptionally polymorphic ant Pheidole rhea. Neu- rosci Lett 676:46–50 Conflict of interest The authors have no conficts of interest to declare GraphPad Software (2018) GraphPad Prism v 8.3.0 for Windows. La that are relevant to the content of this article. Jolla Gronenberg W, Hölldobler B (1999) Morphologic representation of visual and antennal information in the ant brain. J Comp Neurol 412:229–240 References Gross MR (1996) Alternative reproductive strategies and tactics: diver- sity within sexes. Trends Ecol Evol 11:92–98 Aiello LC, Wheeler P (1995) The expensive-tissue hypothesis: the Healy S, Guilford T (1990) Olfactory-bulb size and nocturnality in brain and the digestive system in human and primate evolution. birds. Evolution 44:339–346 Curr Anthro 36:199–221 Houston TF (1991) Ecology and behaviour of the bee Amegilla (Asa- Alcock J (1976) The social organization of male populations of Centris ropoda) dawsoni (Rayment) with notes on a related species pallida (Hymenoptera, Anthophoridae). Psyche 83:121–131 (Hymenoptera: Anthophoridae). Rec West Aust Mus 15:591–609 Alcock J (1979) The evolution of intraspecifc diversity in male repro- Keesey IW, Grabe V, Gruber L, Koerte S, Obiero GF, Bolton G, Khal- ductive strategies in some bees and wasps. In: Blum MS, Blum laf MA, Kunert G, Lavista-Llanos S, Valenzano DR, Rybak J, NA (eds) Sexual selection and reproductive competition in insects. Barrett BA, Knaden M, Hansson BS (2019) Inverse resource allo- Academic Press, New York, pp 381–402 cation between vision and olfaction across the genus Drosophila. Alcock J (1984) Long-term maintenance of size variation in popu- Nat Commun 10:1162 lations of Centris pallida (Hymenoptera: Anthophoridae). Evol Kenyon FC (1896) The brain of the bee. A preliminary contribution to 38:220–223 the morphology of the nervous system of the Arthropoda. J Comp Alcock J (1997) Competition from large males and the alternative mat- Neurol 6:133–210 ing tactics of small males of Dawson’s burrowing bee (Amegilla Kotrschal K, van Staaden MJ, Huber R (1998) Fish brains: evolution dawsoni) (, Apinae, ). J Insect Behav and environmental relationships. Rev Fish Biol Fish 8:373–408 10:99–113 Kukuk PF (1996) Male dimorphism in Lasioglossum (Chilalictus) hemichalceum: the role of larval nutrition. J Kans Entomol Soc 69:147–157

1 3 Journal of Comparative Physiology A

Liao WB, Lou SL, Zeng Y, Kotrschal A (2016) Large brains, small Sherry DF (2006) Neuroecology. Ann Rev Psychol 57:167–197 guts: the expensive tissue hypothesis supported with anurans. Am Shuster SM (2010) Alternative mating strategies. In: Fox C, Westneat Nat 188:693–700 DF (eds) Evolutionary behavioral ecology. Cambridge University Luo Y, Zhong MJ, Huang Y, Li F, Liao WB, Kotrschal A (2017) Sea- Press, Cambridge sonality and brain size are negatively associated in frogs: evidence Shuster SM, Wade MJ (2003) Mating systems and strategies. Princeton for the expensive brain framework. Sci Rep 7:16629 University Press, Princeton Montgomery SH, Ott SR (2015) Brain composition in Godyris Simmons LW, Alcock J, Reeder A (2003) The role of cuticular hydro- zavaleta, a diurnal butterfy, refects an increased reliance on carbons in male attraction and repulsion by female Dawson’s bur- olfactory information. J Comp Neurol 523:869–891 rowing bee, Amegilla dawsoni. Anim Behav 66:677–685 Niven JE (2016) Neuronal energy consumption: biophysics efciency Slater GP, Yocum GD, Bowsher JH (2020) Diet quantity infuences and evolution. Curr Opin Neurobiol 41:129–135 caste determination in honeybees (Apis mellifera). Proc R Soc Niven JE, Laughlin SB (2008) Energy limitation as a selective pressure Lond B Biol Sci 287:20200614 on the evolution of sensory systems. J Exp Biol 211:1792–1804 Snelling RR (1984) Studies on the and distribution of Ameri- O’Donnell S, Cliford MR, DeLeon S, Papa C, Zahedi N, Bulova SJ can Centridine bees (Hymenoptera: Anthophoridae). Contrib Sci (2013) Brain size and visual environment predict species difer- 347:1–69 ences in paper wasp sensory processing brain regions (Hymenop- Soares D, Niemiller ML (2013) Sensory adaptations of fshes to subter- tera: Vesidae, Polistinae). Brain Behav Evol 82:177–184 ranean environments. Bioscience 63:274–283 O’Donnell S, Bulova SJ, Barrett M, Fiocca K (2017) Size constraints Stieb SM, Kelber C, Wehner R, Rossler W (2011) Antennal-lobe organ- and sensory adaptations afect mosaic brain evolution in paper ization in desert ants of the genus Cataglyphis. Brain Behav Evol wasps (Vespidae: Epiponini). Biol J Linn Soc 123:302–310 77:136–146 O’Donnell S, Bulova S, Barrett M, von Beeren C (2018) Brain invest- Stöckl A, Heinze S, Charalabidis A, el Jundi B, Warrant E, Kelber A ment under colony-level selection: soldier-specialization in Eciton (2016) Diferential investment in visual and olfactory brain areas army ants (Formicidae: Dorylinae). BMC Zool 3:3 refects behavioral choices in hawk moths. Sci Rep 6:26041 Oliveira RF, Taborsky M, Brockmann HJ (2008) Alternative repro- Tierney SM, Friedrich M, Humphreys WF, Jones TM, Warrant EJ, ductive tactics: an integrative approach. Cambridge University Wcislo WT (2017) Consequences of evolutionary transitions in Press, Cambridge changing photic environments. Aust Entomol 56:23–46 Özer I, Carle T (2020) Back to the light, coevolution between vision van der Woude E, Groothius J, Smid HM (2019) No gains for bigger and olfaction in the “dark-fies” (Drosophila melanogaster). PLoS brains: functional and neuroanatomical consequences of relative ONE 15:e0228939 brain size in a parasitic wasp. J Evol Biol 32:694–705 Paulk AC, Gronenberg W (2008) Higher order visual input to the Warrant EJ, Locket NA (2004) Vision in the deep sea. Biol Rev Camb mushroom bodies in the bee, Bombus impatiens. Struct Philos Soc 79:671–712 Dev 37:443–458 Wenner AM (1974) Information transfer in honeybees: a population Paxton RJ (2005) Male mating behaviour and mating systems of bees: approach. In: Kramer L, Pliver P, Alloway R (eds) Advances in an overview. Apidologie 36:145–156 the study of communication and afect. Plenum Press, New York, Rehan SM, Bulova SJ, O’Donnell S (2015) Cumulative efects of for- pp 133–169 aging behavior and social dominance on brain development in Wilczynski W (1984) Central nervous systems subserving a homopla- a facultatively social bee (Ceratina australensis). Brain Behav sous periphery. Am Zool 24:755–763 Evol 85:117–124 Schneider CA, Rasband WS, Eliceiri KW (2012) NIH Image to ImageJ: Publisher’s Note Springer Nature remains neutral with regard to 25 years of image analysis. Nat Methods 9:671–675 jurisdictional claims in published maps and institutional afliations. Sheehan ZBV, Kamhi JF, Seid MA, Narendra A (2019) Diferential investment in brain regions for a diurnal and nocturnal lifestyle in Australian Myrmecia ants. J Comp Neurol 527:1261–1277

1 3