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Fig. 7 in Sexually dimorphic ornamentation in modern spinicaudatans and the taxonomic implications for fossil clam shrimps

Fig. 7. Ornamentations on the growth bands in extant spinicaudatans species of Cyzicus Audouin, 1837, Ozestheria Schwentner, Just, and Richter, 2015, and Diestheria longinqua Chen in Zhang et al., 1976. A. Carapace of Ozestheria pilosa (Rogers, Thaimuangphol, Saengphan, and Sanoamuang, 2013), from Thailand (after Rogers et al. 2013: fig. 3A). B. Cyzicus gifuensis (Ishikawa, 1895), from Anhui, China, NIPG Cr.121, male; ornamentation in the ventral part of the carapace (B1) and near the ventral margin of carapace (B2); radial lirae along the lower margin of each growth band (B3). in ornamentations might suggest a close affinity between The carapaces of the family Limnadiidae are thin and hermaphroditic Cyzicus and Aquilonoglypta as suggested by lightly mineralized, which commonly resulted in a reticulate Astrop and Hegna (2015). depressiononthecarapacesurface, suchas Eulimnadiatexana The transition pattern from reticulation to lirae in the Packard, 1871 (Astrop 2014). However, the carapace surfaces ventral part of the carapace in the Ozestheria differs from of most species of Eulimnadia are unornamented (smooth the Cyzicus which has the large undeveloped reticulation. surface pattern). This pattern also occurs in Metalimnadia Australian species of Ozestheria had reticulation, granulated serratus Mattox, 1952, Paralimnadia badia (Wolf, 1911) and ornaments, or a combination of punctae and lirae (Timms some Triassic fossil species of Paleolimnadiidae (Table 1). 2018). The ornamentation pattern of O. pilosa was similar The fossil family Palaeolimnadiopsidae is characterized by to species of Diestheriidae, in which transversely enlarged the recurvature of growth lines to form carinate at the posreticulation overlapped on the lirae ornamentation of each terior-dorsal marginal junction of the carapace. This feature growth band of the carapace (Rogers et al. 2013). The larger has also been observed in living species of Limnadopsis. secondary reticulation was likely originated from the in- The ornamentation documented for Palaeolimnadiopsidae tra-cuticular layer rather than the reticulation from procuti- ranged from reticulation to reticulation-lirae combination. cle (Astrop 2014). The ornamentation pattern in Ozestheria However, the ornamentation possessed by Limnadopsis ocsp. (males, Fig. 1A5), including punctae-reticulation-lirae cidentalis Timms, 2009, is nodular (Astrop 2014). Imnadia combination, the transition from reticulation to lirae, and yeyetta Hertzog, 1935, was reported to exhibit punctae ornathe larger undeveloped reticulation, is in line with that of mentation (Astrop 2014). Nevertheless, this pattern was not fossil species Triglypta yabraiensis Wang, 2014 (Wang 2014: mentioned in the original descriptions of the fossil families pl. 2: 2). The close morphological resemblance of ornamen- Paleolimnadiidae, Palaeolimnadiopsidae or Perilimnadiidae. tations and carapace shape suggests that Ozestheria might The phenotypic differentiation of ornamentation pattern is be closely related to Triglypta or Tianzhuestheria. a model to investigate morpho-functional adaptation to some

Fig. 6 in Sexually dimorphic ornamentation in modern spinicaudatans and the taxonomic implications for fossil clam shrimps

Fig. 6. Carapaces and ornamentations of representatives of the extant spinicaudatan family Leptestheriidae. A. Leptestheria kawachiensis Uéno, 1927, from Hubei, China, NIGP Cr. 101, male, lateral view; left valve, oval outline (A1); growth bands in the upper part of carapace with wide radial fringes pattern (A2). B. Eoleptestheria ticinensis (Balsamo-Crivelli, 1859), from Jiangsu, China, NIGP Cr. 61, male, lateral view; right valve, oval outline (B1); growth bands in the ventral part of carapace with shallow fringes pattern, never developing reticulation or punctae between fringes (B2); details of ventral growth bands with shallow fringes pattern separated with smooth surface (B3, B4).

Fig. 4 in Sexually dimorphic ornamentation in modern spinicaudatans and the taxonomic implications for fossil clam shrimps

Fig. 4. Ornamentations on the growth bands in the extant spinicaudatan branchiopod Eulimnadia sp. and the extant laevicaudatan branchiopod Lynceus sp. A, B. Eulimnadia sp., from Jiangxi, China. A. NIGP Cr. 161, male, carapace in lateral view. B. NIGP Cr. 162, female, unornamented area near the ventral margin. C, D. Lynceus sp., from Heilongjiang, China. C. NIGP Cr. 173, male, carapace in lateral view. D. NIGP Cr. 174, female, isogonal reticulate ornamentation in the valve.

Fig. 3 in Sexually dimorphic ornamentation in modern spinicaudatans and the taxonomic implications for fossil clam shrimps

Fig. 3. Ornamentations on the growth bands of carapace of the extant spinicaudatan branchiopod Eocyzicus orientalis Daday, 1913, from Xinjiang, China. A. NIGP Cr. 1, male, ornamentation in the upper to middle parts of the carapace (A1), reticulate ornaments in the ventral part of the carapace (A2), dense pilosity on the growth lines near the edge of the carapace (A3). B. NIGP Cr. 2, female, ornamentation in the upper to middle parts of the carapace (B1), rows of nodular ornaments in the ventral part of the carapace (B2), stout setae on the growth lines near the edge of the carapace (B3).

Fig. 2 in Sexually dimorphic ornamentation in modern spinicaudatans and the taxonomic implications for fossil clam shrimps

Fig. 2. Ornamentation on the growth bands of carapaces of the extant spinicaudatan branchiopod Cyzicus sp., from Jilin, China. A. NIGP Cr. 141, male, ornamentation in the larval valve (A1), in the middle part of the carapace (A2), large reticulation and the radial lirae along the lower margin of the growth band (A3). B. NIGP Cr. 142, female, ornamentation in the larval valve (B1) and in the middle part of the carapace (B2), weakly ornamented area near the ventral margin (B3).

opencc-zeroDec 2020View details →

Physiological costs and age constraints of a sexual ornament: an experimental study in a wild bird

Sexual ornaments are often considered honest signals of quality because potential costs or constraints prevent their display by low-quality individuals. Testing for potential physiological costs of ornaments is difficult, as this requires experimentally forcing individuals to produce and display elaborate ornaments. We use this approach to test whether a sexually selected trait is physiologically costly to male superb fairy-wrens (Malurus cyaneus). Male fairy-wrens moult from brown to blue breeding plumage at different times of the year, and females strongly prefer the few males that are blue early, during winter. We used short-acting testosterone implants to stimulate males to produce 'early-blue' plumage and assessed costs during and after moult using a panel of physiological indices. Testosterone-implanted, T-males moulted in winter and produced blue plumage six weeks before control-implanted, C-males. T-males moulted while in lower body condition, had lower fat reserves, and were more likely to be parasitised by lice. However, we detected no negative effects on immune function, blood parasites, exposure to stressors, or survival. Juvenile males never naturally display early-blue plumage, but we found no evidence for increased costs paid by juvenile T-males. Instead, juvenile T-males moulted later than adult T-males, suggesting that age presents an absolute constraint on ornament exaggeration that cannot be fully overcome by testosterone treatment. Together, these small costs and large, age-related constraints may enforce signal honesty, and explain female preference for early-blue males.

opencc-zeroDec 2020View details →

Positive genetic covariance between male sexual ornamentation and fertilizing capacity

Postcopulatory sexual selection results from variation in competitive fertilization success among males, and comprises powerful evolutionary forces that operate after the onset of mating [1, 2]. Theoretical advances in the field of sexual selection addressing the build-up and co-evolutionary consequences of genetic coupling [3-5], motivate the hypothesis that indirect postcopulatory sexual selection may promote evolution of male secondary sexual traits—those traits traditionally ascribed to mate choice and male fighting [6, 7]. A crucial prediction of this hypothesis is genetic covariance between trait expression and competitive fertilization success, which has been predicted to arise, for example, when traits subject to pre- and postcopulatory sexual selection are under positive correlational selection [8]. We imposed bidirectional artificial selection on male ornament (sex comb) size in Drosophila bipectinata, and demonstrate increased competitive fertilization success as a correlated evolutionary response to increasing ornament size. Transcriptional analyses revealed that levels of specific seminal fluid proteins repeatedly shifted in response to this selection, suggesting that properties of the ejaculate rather than the enlarged sex comb itself contributed fertilizing capacity. We used ultraprecise laser surgery to reduce ornament size of high line males, and found that their fertilizing superiority persisted despite the size reduction, reinforcing the transcriptional results. The data support the existence of positive genetic covariance between a male secondary sexual trait and competitive fertilization success, and suggest the possibility that indirect postcopulatory sexual selection may under certain conditions magnify net selection on ornamental trait expression.

opencc-zeroNov 2021View details →

The stabilising impact of natural selection on the allometry of sexual ornaments: Fish that escape locomotor constraints exhibit extravagant ornamentation

1. Positive allometry has been considered a hallmark of sexual selection whereby larger males of superior condition develop disproportionately larger ornaments for their body size compared to smaller males of poorer condition. 2. Yet many structures known to be sexually selected often exhibit other allometric patterns. This has led to controversy over the utility of allometry in adequately capturing the signature of sexual selection, particularly if static (within population) and evolutionary (across species) allometries are functionally constrained by stabilising natural selection. 3. To investigate this, we evaluated the allometries of ornamental head crests and dorsal fins across multiple species of blenny fish. In particular, we compared species that occupied an aquatic environment—where swimming performance was expected to have constrained ornament size—with species that have transitioned onto land where such biomechanical constraints on ornament size have been removed. 4. Static allometries of both head crest and dorsal fin ornaments were found to be positive in males, but less so in females, across all species examined. This was consistent with the allometric theory of sexual selection that predicts positive allometry specifically in male ornamentation. Nevertheless, male allometric slopes were constrained in aquatic species whereas males of terrestrial species were free to exaggerate the size of their ornaments. Natural selection therefore appears to suppress ornament size in aquatics because of the biomechanical constraints associated with swimming. These differences in within-population static allometry between aquatic and terrestrial species in turn manifested in a greater across-species evolutionary allometric intercept, but not slope, for terrestrial species relative to aquatic and species. 5. These findings indicate that the study of ornament allometries can provide useful insights into the role of sexual selection on ornament elaboration and also help reveal the presence of opposing natural selection that might result in alternative allometric patterns. The relationship between static and evolutionary allometries remains complex, and our results caution against the interpretation of evolutionary allometry in the absence of a clear understanding of the underlying static allometries associated with it.

opencc-zeroJan 2022View details →

Effects of chronic and acute predation risk on sexual ornamentation and mating preferences

Phenotypic plasticity is wide-spread in animals, but how plastic responses to predation threat affect traits under sexual selection and influence mating preferences is not well understood. Here, we examined how chronic predation risk during development and acute predation risk during mate choice affect the expression of male secondary sexual traits and female mating preference in the three-spined stickleback, Gasterosteus aculeatus. Males reared under chronic predation risk developed less intense red breeding colouration but showed higher courtship activity than males that grew up in a predator-free environment. Acute predation risk during mate choice did not influence male behaviour or ornamentation. Predation risk experienced during development did not affect female mating preferences, while acute predator presence induced a switch in preferences for male courtship activity. Male body size and eye colouration influenced the intensity of female mating preferences, while the trait changing most in response to predation risk during development (red colouration) had no significant impact. The observed interplay between developmental plasticity in male ornamental traits and environment-dependent female mating preferences may lead to dynamic processes altering the strength and direction of sexual selection depending on both the chronic and acute risk of predation. These processes may contribute to the maintenance of within- and among-population variation in secondary sexual traits, and may, ultimately, facilitate speciation.

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Data from: Sexual color ornamentation, microhabitat choice, and thermal physiology in the common wall lizard (Podarcis muralis)

Common wall lizards (Podarcis muralis) in Italy show a striking variation in body coloration across the landscape, with highly exaggerated black and green colors in hot and dry climates and brown and white colors in cool and wet climates. Males are more intensely colored than females, and previous work has suggested that the maintenance of variation in coloration across the landscape reflects climatic effects on the strength of male–male competition, and through this sexual selection. However climatic effects on the intensity of male–male competition would need to be exceptionally strong to fully explain the geographic patterns of color variation. Thus, additional processes may contribute to the maintenance of color variation. Here we test the hypothesis that selection for green and black ornamentation in the context of male–male competition is opposed by selection against ornamentation because the genes involved in the regulation of coloration have pleiotropic effects on thermal physiology, such that ornamentation is selected against in cool climates. Field observations revealed no association between body coloration and microhabitat use or field active body temperatures. Consistent with these field data, lizards at the extreme ends of the phenotypic distribution for body coloration did not show any differences in critical minimum temperature, preferred body temperature, temperature‐dependent metabolic rate, or evaporative water loss when tested in the laboratory. Combined, these results provide no evidence that genes that underlie sexual ornamentation are selected against in cool climate because of pleiotropic effects on thermal biology.

opencc-by-4.0Jul 2024View details →

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Male-like ornamentation in female hummingbirds results from social harassment rather than sexual selection DATA_CODE

Contains all relevant data and code for analyses and figures used in "Male-like ornamentation in female hummingbirds results from social harassment rather than sexual selection" by Jay J. Falk, Michael S. Webster, and Dustin R. Rubenstein. Current Biology, 2021.

opencc-by-4.0Jun 2021View details →

opencc-zeroMay 2023View details →

Data for: Size rather than complexity of sexual ornaments prolongs male metamorphosis and explains sexual size dimorphism in sepsid flies

Male sexual ornaments often evolve rapidly and are thought to be costly, thus contributing to sexual size dimorphism. However, little is known about their developmental costs, and even less about costs associated with structural complexity. Here, we quantified the size and complexity of three morphologically elaborate sexually dimorphic male ornaments that starkly differ across sepsid fly species (Diptera: Sepsidae). Male forelegs range from being unmodified, like in most females, to being adorned with spines and large cuticular protrusions. The 4th abdominal sternites are either unmodified or are converted into complex de novo appendages. Male genital claspers range from small and simple to large and complex (e.g. bifurcated). We tracked the development of 18 sepsid species from egg to adult to determine larval feeding and pupal metamorphosis times of both sexes. We then statistically explored whether pupal and adult body size, ornament size, and/or ornament complexity are correlated with sex-specific development times. Larval growth and foraging periods of male and female larvae did not differ, but the time spent in the pupal stage was ca. 5% longer for sepsid males despite emerging 9% smaller than females on average. Surprisingly, we found no evidence that sexual trait complexity prolongs pupal development beyond some effects of trait size. Evolving more complex traits thus does not incur developmental costs.

opencc-zeroAug 2023View details →

X chromosome drive is constrained by sexual selection and influences ornament evolution

Experimental evolution provides an integrative method for revealing complex interactions among evolutionary processes. One such interaction involves sex-linked selfish genetic elements and sexual selection. X-linked segregation distorters, a type of selfish genetic element, influence sperm transmission to increase in frequency and consequently alter the population sex ratio and the opportunity for sexual selection, while sexual selection may impact the spread of X-linked distorters. Here we manipulated sexual selection by controlling female mating opportunities and the presence of a distorting X chromosome in experimental lines of the stalk-eyed fly, Teleopsis dalmanni , over 11 generations . We find that removal of sexual selection leads to an increase in the frequency of the X-linked distorter and sex ratio across generations and that post-copulatory sexual selection alone is sufficient to limit the frequency of distorters. In addition, we find that male eyestalk length, a trait under pre-copulatory sexual selection, evolves in response to changes in the strength of sexual selection with the magnitude of the response dependent on X chromosome type and the frequency of distorting X chromosomes. These results reveal how a selfish X can interact with sexual selection to influence the evolution of sexually selected traits in multiple ways.