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15. Marcet, B., Chevalier, B., Luxardi, G., Dougherty, G.W., et al. (2014). Mutations in 20. Spektor, A., Tsang, W.Y., Khoo, D., and Coraux, C., Zaragosi, L.E., Cibois, M., CCNO result in congenital mucociliary Dynlacht, B.D. (2007). Cep97 and CP110 Robbe-Sermesant, K., Jolly, T., Cardinaud, B., clearance disorder with reduced generation of suppress a cilia assembly program. Cell 130, Moreilhon, C., et al. (2011). Control of multiple motile cilia. Nat. Genet. 46, 646–651. 678–690. vertebrate multiciliogenesis by miR-449 18. Boon, M., Wallmeier, J., Ma, L., Loges, N.T., through direct repression of the Delta/Notch Jaspers, M., Olbrich, H., Dougherty, G.W., pathway. Nat. Cell Biol. 13, 693–699. Raidt, J., Werner, C., Amirav, I., et al. (2014). Swiss Institute for Experimental Cancer 16. Song, R., Walentek, P., Sponer, N., Klimke, A., MCIDAS mutations result in a mucociliary Research (ISREC), School of Life Sciences, Lee, J.S., Dixon, G., Harland, R., Wan, Y., clearance disorder with reduced generation Swiss Federal Institute of Technology (EPFL), Lishko, P., Lize, M., et al. (2014). miR-34/449 of multiple motile cilia. Nat. Commun. 5, 4418. Lausanne, Switzerland. miRNAs are required for motile ciliogenesis 19. Chen, Z., Indjeian, V.B., McManus, M., by repressing cp110. Nature 510, 115–120. Wang, L., and Dynlacht, B.D. (2002). CP110, *E-mail: pierre.gonczy@epfl.ch 17. Wallmeier, J., Al-Mutairi, D.A., Chen, C.T., a cell cycle-dependent CDK substrate, Loges, N.T., Pennekamp, P., Menchen, T., regulates centrosome duplication in human Ma, L., Shamseldin, H.E., Olbrich, H., cells. Dev. Cell 3, 339–350. http://dx.doi.org/10.1016/j.cub.2014.07.006

Animal Behaviour: Task Perhaps some individuals are just inherently better than others at certain Differentiation by Personality tasks, or they become better over time with more practice [8]. If, at the same in Groups time, other group members are, or become better at other tasks, and individuals mostly perform the tasks In social , group efficiency is often assumed to increase with task they are good at, each group member differentiation, but this requires that individuals are better than generalists may gain the benefits of improved at the task they specialize in. A new study finds that individual group efficiency. For example, in the studiosus do predominantly perform the task they excel at, in line cooperatively breeding cichlid fish with their individual personality type, when they are placed in groups. Neolamprologus pulcher, task participation varies with body size Lena Grinsted* raising the young. Hence, when groups and age, perhaps because smaller and Jonathan P. Bacon contain a mix of both types, emergent fish are better at defending the nest task differentiation increases overall while larger fish are better at removing Did you think that all spiders are group performance benefitting all sand from the nest [9]. However, ferocious predators, which attack any group members. the assumption that task participation other spider or bug they come across? Consider a leafcutter ant nest. Some actually correlates with individual Well, think again. Sure, it is true that worker ants are tiny, while others are task performance in non-polymorphic many spiders will eat their own huge. It is easy to imagine how an ant social animals has rarely been proven. offspring if they get in the way, and yes, colony can benefit from this extreme Social spiders provide a good some females will happily snack on polymorphism; tiny workers will example of highly cooperative their partners during mating. But efficiently feed and clean the fungus societies in which female group some spiders form cooperative gardens, while large soldiers with members are non-polymorphic and communities where they live peacefully gigantic mandibles are superior at yet show reproductive skew and task side by side [1]. Darwin himself defending the nest against larger differentiation within groups [10,11]. expressed surprise when he came predators [6]. Task specialization Only about 25 species bear the title across a group-living spider in 1832 accompanied by polymorphism leads ‘social’ out of almost 45,000 spider (Parawixia bistriata) [2]. One spider that to more efficient and successful species described [12]. These are facultatively forms small groups is groups. Why task differentiation would cooperative breeders that live in Anelosimus studiosus. Within an be beneficial within societies of extremely inbred societies. In the Anelosimus studiosus group some cooperative breeders that lack evolution of permanent sociality from females show an aggressive morphological castes, such as the subsociality, a pre-mating dispersal personality type and participate more social spiders, birds and mammals, is stage has been lost, leaving brothers in colony defense and prey capture, harder to imagine. For example, why do and sisters to mate generation after while others are docile and engage helpers in the cooperatively breeding generation (within-group relatedness: more in brood care [3]. Experimental noisy miner, Manorina melanocephala, r > 0.5 [13]). Subsocial species, such groups containing a mix of these two often specialize in either chick as A. studiosus, show cooperation at different personalities outperform provisioning or mobbing nest the juvenile stage, after which siblings groups of only one personality type, predators, rather than participating disperse to breed alone, maintaining using egg-case weight as a proxy for equally in all tasks [7]? Individuals an outbred mating system [1]. The new fitness [4]. An elegant new study by within these types of social groups findings by Wright et al. [5] showing Colin M. Wright and colleagues [5] has are all morphologically capable of that A. studiosus specialize on tasks found the reason why. Aggressive performing any task. So why do some they are efficient at when placed in females are simply more efficient group members engage in riskier groups may be key to understanding at foraging, web construction and activities, such as colony defense, why social spiders show individual defense, while docile females excel at more than others? behavioral variation. Current Biology Vol 24 No 16 R750

characteristic of social cooperative breeders. All females within the groups reproduce and mothers will aggressively chase away other adult group members [17]. Hence, A. studiosus is a subsocial species that sometimes occurs in groups. This makes it an ideal species for studies on the costs and benefits of group living, as group sizes are easily manipulated in the lab. Studies asking whether behavioral variation is an adaptation to sociality are now needed in fully social spider species. All populations of A. studiosus studied to date have contained a mix of aggressive and docile phenotypes [15], personality traits have been found to be heritable [18], and group forming behavior is non-plastic in solitary populations [14]. Therefore, different personalities are maintained even in populations that exist purely of solitary spiders with no behavioral plasticity to naturally form groups. Thus, it seems Figure 1. Social spiders. unlikely that mixed phenotypes is an Six Stegodyphus sarasinorum attack an ant prey, while their more timid nestmates (not shown) remain in the safety of the nest. (Photo: Virginia Settepani.) adaptation to group living or sociality in this species. Consistent personalities and In some Amazonian social spiders, area of behavioral types. Interestingly, behavioral syndromes have been such as Anelosimus eximius [11], instead of showing gradual, normally documented in a diverse range of both task differentiation is age related, as distributed individual personality social and non-social species, individuals acquire more colony tasks scores, this spider shows a bimodal including insects, spiders, fish, birds with age, while in Old World social distribution [14]. This allows and mammals [19]. Behavioral spiders, something more intriguing researchers to group individual spiders differences may occur in some species is going on. Despite being genetically into aggressive and docile phenotypes, due to stochasticity and differences in highly similar and all of similar age and and it turns out that different internal states and may be adaptive in developmental stage, Stegodyphus personality traits are correlated in a others due, for example, to sarasinorum spiders (Figure 1) show behavioral syndrome [15]. Aggressive frequency-dependent selection [20].If task differentiation in prey attack: individuals show shorter latencies to personalities exist in a non-social or certain individuals specialize in attack prey and to resume movement subsocial ancestral state, whether it be bringing in the food while others after a disturbance, and prefer to maintained stochastically or through rarely or never help out [11]. What is position themselves further from selection, and if phenotypic variation it that predicts differential participation conspecifics in forced pairings in the within groups proves beneficial in the in this spider? Individual personality lab. The docile phenotypes show the transition to sociality, selection might is the answer, with personality defined opposite trends in all of the above quickly amplify individual differences. as behavioral differences among personality tests. Hence, if having mixed personalities individuals that are consistent over A. studiosus is usually found living within a group provides adaptive time and across context [10]. solitarily in nature. A small percentage benefits in the form of improved Individuals vary in their level of of nests, however, contain multiple group performance, this mechanism boldness, and bolder spiders females with an average of about five behind task specialization might be specialize in prey attack. What do females per nest. In its usual habitat in prevalent in a whole range of other the shy group members then do? the U.S. the proportion of multi-female non-polymorphic cooperative And are the bold group members nests varies from 0 to 15% [14]. Groups breeders. This is an exciting era for actually better at catching prey? These of adult females probably stem from research on social organization in are still unanswered questions in social young failing to disperse from their cooperative animals, a field species, but perhaps the behavioral maternal nest, and relatedness within previously dominated by studies on strategy of doing what you are good at, groups is therefore at the half-sib eusocial insects. The question remains now demonstrated so clearly in the level (r w 0.25) [16]. Females may whether personality is a common subsocial A. studiosus [5], provides share prey, and it seems they do not mechanism behind task allocation the answer. discriminate their own and foreign across taxa, and whether social A. studiosus is a model organism for egg cases and offspring, but they spiders, and other cooperative studies on personality and by far lack the features of reproductive breeders, have adaptively employed the best-studied spider in the research skew and tolerance, which are this mechanism. Dispatch R751

References 9. Bruintjes, R., and Taborsky, M. (2011). (2010). Population differences in behaviour 1. Lubin, Y., and Bilde, T. (2007). The evolution of Size-dependent task specialization in a are explained by shared within-population sociality in spiders. Adv. Study Behav. 37, cooperative cichlid in response to experimental trait correlations. J. Evol. Biol. 23, 748–756. 83–145. variation of demand. Anim. Behav. 81, 387–394. 16. Duncan, S.I., Riechert, S.E., Fitzpatrick, B.M., 2. Darwin, C. (1845). The Voyage of the Beagle. 10. Grinsted, L., Pruitt, J.N., Settepani, V., and and Fordyce, J.A. (2010). Relatedness and Journal of Reasearches into the Natural History Bilde, T. (2013). Individual personalities shape genetic structure in a socially polymorphic and Geology of the Countries Visited During the task differentiation in a social spider. Proc. R. population of the spider Anelosimus studiosus. Voyage of HMS Beagle Round the World Soc. B. Biol. Sci. 280. Mol. Ecol. 19, 810–818. (London: J. Murray). 11. Settepani, V., Grinsted, L., Granfeldt, J., 17. Furey, F.E. (1998). Two cooperatively social 3. Pruitt, J.N., and Riechert, S.E. (2011). Jensen, J.L., and Bilde, T. (2013). Task populations of the theridiid spider Anelosimus Within-group behavioral variation promotes specialization in two social spiders, studiosus in a temperate region. Anim. Behav. biased task performance and the emergence Stegodyphus sarasinorum (Eresidae) and 55, 727–735. of a defensive caste in a social spider. Behav. Anelosimus eximius (). J. Evol. Biol. 18. Pruitt, J.N., and Riechert, S.E. (2009). Sex Ecol. Sociobiol. 65, 1055–1060. 26, 51–62. matters: sexually dimorphic fitness 4. Pruitt, J.N., and Riechert, S.E. (2011). 12. Avile´ s, L. (1997). Causes and consequences consequences of a behavioural syndrome. How within-group behavioural variation and of cooperation and permanent-sociality in Anim. Behav. 78, 175–181. task efficiency enhance fitness in a social spiders. In The Evolution of Social Behavior in 19. Bell, A.M., Hankison, S.J., and Laskowski, K.L. group. Proc. R. Soc. B. Biol. Sci. 278, Insects and , J.C. Choe and (2009). The repeatability of behaviour: a 1209–1215. B.J. Crespi, eds. (Cambridge, United Kingdom: meta-analysis. Anim. Behav. 77, 771–783. 5. Wright, C.M., Holbrook, C.T., and Pruitt, J.N. Cambridge University Press), pp. 476–498. 20. Dall, S.R.X., Houston, A.I., and McNamara, J.M. (2014). Animal personality aligns task 13. Johannesen, J., Hennig, A., Dommermuth, B., (2004). The behavioural ecology of personality: specialization and task proficiency in and Schneider, J.M. (2002). Mitochondrial consistent individual differences from an a spider society. Proc. Natl. Acad. Sci. USA DNA distributions indicate colony propagation adaptive perspective. Ecol. Lett. 7, 734–739. 111, 9533–9537. by single matri-lineages in the social spider 6. Wilson, E.O. (1953). The origin and evolution Stegodyphus dumicola (Eresidae). Biol. J. Linn. of polymorphism in ants. Quart. Rev. Biol. 28, Soc. 76, 591–600. Evolution, Behaviour and Environment 136–156. 14. Riechert, S.E., and Jones, T.C. (2008). Group, School of Life Sciences, University of 7. Arnold, K.E., Owens, I.P.F., and Goldizen, A.W. Phenotypic variation in the social behaviour Sussex, Falmer, Brighton BN1 9QG, UK. of the spider Anelosimus studiosus along (2005). Division of labour within cooperatively *E-mail: [email protected] breeding groups. Behaviour 142, a latitudinal gradient. Anim. Behav. 75, 1577–1590. 1893–1902. 8. Gordon, D.M. (1996). The organization of work 15. Pruitt, J.N., Riechert, S.E., Iturralde, G., in social insect colonies. Nature 380, 121–124. Vega, M., Fitzpatrick, B.M., and Aviles, L. http://dx.doi.org/10.1016/j.cub.2014.07.008

Dinosaur Evolution: Feathers Up for There is also support for hypotheses that flapping flight in modern birds most Selection likely evolved through a four-winged stageindinosaurs.Clearly,feathersare key to understanding the evolutionary A new specimen of the early bird Archaeopteryx shows remarkable plumage forces and events that led to the preservation, including pennaceous leg feathers. But whether birds went emergence of flying birds. Now, Foth through a four-winged stage, and in what exact functional context feathers and colleagues [11] report a new evolved remains a matter of debate. specimen of the iconic early bird Archaeopteryx that shows unique Zhonghe Zhou tremendously improved our preservation of feathers. understanding of the evolutionary Archaeopteryx lithographica, After nearly one and half century of transition from dinosaur to bird [1–4]. arguably the most studied species in study and debate on whether extant More recently, evidence of the color of vertebrate paleontology, has long been birds are descendants of dinosaurs, fossil feathers in the form of preserved held as the earliest and most primitive paleontologists now generally agree melanosomes has been found in various bird, ever since its first skeleton was that all birds are derived from a group dinosaurs and early birds, providing reported in 1861. Undoubtedly, of small-sized theropods (a suborder of evidence of their appearance and Archaeopteryx has played a key role bipedal saurischian or ‘lizard-hipped’ inferred behaviors [5–7].Thisfurther in the discussion of the origin of birds, dinosaurs). In the past two decades, allowed new investigations into the feathers, and avian flight. However, paleontology has also made remarkable details of feather morphology and their with the remarkable discoveries of progress in understanding of the origin functional explanations in these new feathered dinosaurs (e.g., Anchiornis and early evolution of bird feathers. taxa as well as rekindled studies on and Xiaotingia), particularly from the Since the first report of proto-feathers previously known birds, such as Jurassic lake deposits in northeastern from the theropod dinosaur the well-known Archaeopteryx China, even the iconic status of Sinosauropteryx [1], diverse types lithographica [8–10]. Many of our Archaeopteryx as the oldest known of feathers in dinosaurs, including traditional views on the origin and early bird has been challenged [4]. theropods and ornithischians, (one of evolution of bird feathers have since Furthermore, until now, information on the two basic divisions of dinosaurs, been revolutionized; we now know that the plumage of Archaeopteryx (largely the ‘bird-hipped’ dinosaurs) have feathers are not restricted to birds, but limited to the London and Berlin been reported mainly from the Early are also found in some non-avian specimens) remained incomplete Cretaceous (about 120 million years ago) dinosaurs; also, they probably did not compared to the exceptional but also Middle-Late Jurassic (about 160 originally evolve for flight, but rather in preservation of the plumage in several million years ago) deposits in some other functional context such as feathered dinosaurs and early birds from northeastern China that have insulation, display, camouflage etc. China. The complete articulated 10th