Temporally Variable Multivariate Sexual Selection on Sexually Dimorphic Traits in a Wild Insect Population

2010 ◽  
Vol 175 (4) ◽  
pp. 401-414 ◽  
Author(s):  
David Punzalan ◽  
F. Helen Rodd ◽  
Locke Rowe
Keyword(s):  
Sexual Selection ◽  
Insect Population ◽  
Sexually Dimorphic

scholarly journals Variation in Chin and Mandibular Symphysis Size and Shape in Males and Females: A CT-Based Study

2020 ◽  
Vol 17 (12) ◽  
pp. 4249
Author(s):  
Tatiana Sella Tunis ◽  
Israel Hershkovitz ◽  
Hila May ◽  
Alexander Dan Vardimon ◽  
Rachel Sarig ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Anatomical Landmark ◽  
Anatomical Structure ◽  
Sexually Dimorphic ◽  
Selection Theory ◽  
Size And Shape ◽  
Size Index ◽  
Sexual Selection Theory ◽  
Males And Females ◽  
Anthropological Literature

The chin is a unique anatomical landmark of modern humans. Its size and shape play an important role from the esthetic perspective. However, disagreement exists in the dental and anthropological literature regarding the sex differences in chin and symphysis morphometrics. The “sexual selection” theory is presented as a possible reason for chin formation in our species; however, many other contradictory theories also exist. This study’s aims were therefore to determine how chin and symphysis size and shape vary with sex, and to discuss “sexual selection” theory as a reason for its formation. Head and neck computed tomography (CT) scans of 419 adults were utilized to measure chin and symphysis sizes and shapes. The chin and symphysis measures were compared between the sexes using an independent-samples t-test, a Mann–Whitney test, and the F-statistic. The chin width was significantly greater in males than in females (p < 0.001), whereas the chin height, area, and size index were significantly greater in females (p < 0.001). Symphysis measures did not differ significantly between the sexes. Size accounted for 2–14% of the chin variance and between 24–33% of the symphysis variance. Overall, the chin was found to be a more heterogeneous anatomical structure than the symphysis, as well as more sexually dimorphic.

Adult morphology of Paramorganiella adventurosa Tonnoir (Diptera: Mycetophilidae: Sciophilinae), including a description of the unique maxillary palpi

Zootaxa ◽  
2010 ◽  
Vol 2559 (1) ◽  
pp. 36 ◽  
Author(s):  
MATHIAS JASCHHOF ◽  
STEPHAN M. BLANK ◽  
Uwe Kallweit
Keyword(s):  
Sexual Selection ◽  
Male Genitalia ◽  
Maxillary Palpus ◽  
Sexually Dimorphic ◽  
Adult Morphology ◽  
New Material ◽  
Mechanical Tool ◽  
First Time

The adult morphology of male Paramorganiella adventurosa Tonnoir is redescribed on the basis of new material from Tasmania. Details of the male genitalia are described and figured for the first time. The female is described for the first time. Special attention is paid to the clypeus and maxillary palpus, both sexually dimorphic, of which the anatomy is extensively illustrated and discussed with respect to possible function and in the context of palpal modifications found in other Mycetophilidae. Anatomy suggests the palpi of males function as a mechanical tool rather than a probing organ, which is unique among Mycetophilidae and Diptera. Various functional hypotheses are discussed in the context of sexual selection.

Is body shape of mangrove-dwelling monitor lizards (Varanus indicus; Varanidae) sexually dimorphic?

2011 ◽  
Vol 32 (1) ◽  
pp. 27-37 ◽  
Author(s):  
Jan Hnízdo ◽  
Veronika Cikánová ◽  
Olga Šimková ◽  
Daniel Frynta ◽  
Petr Velenský ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Body Shape ◽  
Sexually Dimorphic ◽  
Evolutionary Explanation ◽  
Body Measurements ◽  
Male And Female ◽  
Fecundity Selection ◽  
Selective Forces ◽  
Monitor Lizards

AbstractIn monitor lizards, males are typically larger than conspecific females, but body shape is usually quite similar in both sexes. This not only represents a puzzle worthy of evolutionary explanation, but also makes field sex determination of monitor lizards difficult. We asked whether subtle differences in body shape follow the same pattern as in other sexually dimorphic lizard taxa and thus can be explained by the same selective forces. We tested the hypotheses that (1) females have a longer abdomen due to fecundity selection and (2) males possess bigger heads due to intrasexual selection. We also hypothesised that (3) male monitors show a wider chests and longer upper fore-limbs to win male-male wrestling matches. We monitored ontogeny in 35 mangrove-dwelling monitors (Varanus indicus). Seventeen body measurements were taken every three months up to the age of 24-34 months. Sex was determined by an ultrasonographic imaging. We employed multiple approaches to remove the effect of size and used both confirmation and exploratory statistics. The results revealed that sexual differences in body shape were small and emerged after maturity. Females have a relatively longer abdomen while males wider chest and longer upper fore-limbs. Thus, the differences in body shape between male and female varanid lizards may be attributed to both fecundity and sexual selection.

scholarly journals Artificial sexual selection alters allometry in the stalk-eyed fly Cyrtodiopsis dalmanni (Diptera: Diopsidae)

1993 ◽  
Vol 62 (3) ◽  
pp. 213-222 ◽  
Author(s):  
Gerald S. Wilkinson
Keyword(s):  
Sexual Selection ◽  
Sexual Dimorphism ◽  
Body Length ◽  
Sexually Dimorphic ◽  
Selected Lines ◽  
Variable Intensity ◽  
High Line ◽  
Cumulative Selection ◽  
Selection For ◽  
Selection Of

SummarySelection for increased and decreased ratio of eye span to body length was exerted on male stalk-eyed flies (Cyrtodiopsis dalmanni) from Malaysia using replicate selected and unselected lines. Response to selection was symmetrical. After 10 generations high line male eye span increased to 1·3 body lengths while low line male eye span declined to 1·1 body lengths. Realized heritabilities for eye span to body length ratio, estimated using regressions of deviations from unselected controls on cumulative selection differentials, were greater than zero for all four selected lines with average h2 = 0·35 + 0·06. The static linear allometric relationship between eye span and body length diverged between selected lines and rotated among selected line males in the same direction as among males in other sexually dimorphic diopsid species. Crosses between lines after 13 generations of selection indicate that the genes which influence relative eye span combine additively and do not exhibit sex linkage or maternal effects. The genetic correlation between the sexes, 0·29 + 0·05 as estimated by the regression of female on male change in eye span, did not prevent sexual dimorphism in eye span from diverging between lines. These results suggest that the exaggerated eye span of male C. dalmanni is maintained by natural selection opposing sexual selection rather than by lack of or asymmetry in additive genetic variation. Furthermore, the variation in sexual dimorphism for eye span-body length allometry observed among extant diopsid species is consistent with sexual selection of variable intensity acting on relative eye span.

scholarly journals Diversification through gustatory courtship: an X-ray micro-computed tomography study on dwarf spiders

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Shou-Wang Lin ◽  
Lara Lopardo ◽  
Gabriele Uhl
Keyword(s):  
Computed Tomography ◽  
Sexual Selection ◽  
Anterior Part ◽  
Divergent Evolution ◽  
Sexually Dimorphic ◽  
Ancestral State ◽  
Glandular Tissue ◽  
Micro Computed Tomography ◽  
Nuptial Gifts ◽  
X Ray

Abstract Background Sexual selection has been considered to promote diversification and speciation. Sexually dimorphic species have been used to explore the supposed effect, however, with mixed results. In dwarf spiders (Erigoninae), many species are sexually dimorphic—males possess marked prosomal modifications. These male traits vary from moderate elevations to bizarre shapes in various prosomal regions. Previous studies established that male dwarf spiders produce substances in these prosomal modifications that are taken up by the females. These substances can act as nuptial gifts, which increase the mating probability of males and the oviposition rate in females. Therefore, these dimorphic traits have evolved in the context of sexual selection. Here, we explore the evolutionary lability of this gustatory trait complex with the aim of assessing the role of this trait complex in species divergence by investigating (1) if erigonine modified prosomata are inherently linked to nuptial-gift-producing glands, (2) if the evolution of the glands evolution preceded that of the modified prosomal shapes, and by assessing (3) the occurrence of convergent/divergent evolution and cryptic differentiation. Results We reconstructed the position and extent of the glandular tissue along with the muscular anatomy in the anterior part of the prosoma of 76 erigonine spiders and three outgroup species using X-ray micro-computed tomography. In all but one case, modified prosomata are associated with gustatory glands. We incorporated the location of glands and muscles into an existing matrix of somatic and genitalic morphological traits of these taxa and reanalyzed their phylogenetic relationship. Our analysis supports that the possession of glandular equipment is the ancestral state and that the manifold modifications of the prosomal shape have evolved convergently multiple times. We found differences in gland position between species with both modified and unmodified prosomata, and reported on seven cases of gland loss. Conclusions Our findings suggest that the occurrence of gustatory glands in sexually monomorphic ancestors has set the stage for the evolution of diverse dimorphic external modifications in dwarf spiders. Differences among congeners suggest that the gland position is highly susceptible to evolutionary changes. The multiple incidences might reflect costs of glandular tissue maintenance and nuptial feeding. Our results indicate divergent evolutionary patterns of gustatory-courtship-related traits, and thus a likely facilitating effect of sexual selection on speciation.

scholarly journals Rapid courtship evolution in grouse (Tetraonidae): contrasting patterns of acceleration between the Eurasian and North American polygynous clades

2007 ◽  
Vol 274 (1613) ◽  
pp. 1079-1086 ◽  
Author(s):  
Allen Spaulding
Keyword(s):  
Sexual Selection ◽  
Mating Success ◽  
Male Mating ◽  
Sexually Dimorphic ◽  
Sexually Selected Traits ◽  
Species Pairs ◽  
Rapid Divergence ◽  
Nucleotide Divergence ◽  
Selected Traits ◽  
Dimorphic Species

Sexual selection is thought to be a powerful diversifying force, based on large ornamental differences between sexually dimorphic species. This assumes that unornamented phenotypes represent evolution without sexual selection. If sexual selection is more powerful than other forms of selection, then two effects would be: rapid divergence of sexually selected traits and a correlation between these divergence rates and variance in mating success in the ornamented sex. I tested for these effects in grouse (Tetraonidae). For three species pairs, within and among polygynous clades, male courtship characters had significantly greater divergence than other characters. This was most pronounced for two species in Tympanuchus . In the Eurasian polygynous clade, relative courtship divergence gradually increased with nucleotide divergence, suggesting a less dramatic acceleration. Increase in relative courtship divergence was associated with mating systems having higher variance in male mating success. These results suggest that sexual selection has accelerated courtship evolution among grouse, although the microevolutionary details appear to vary among clades.

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