scholarly journals On two cases of male dimorphism in dwarf spiders (Araneae: Linyphiidae)

2018 ◽  
Vol 55 (1) ◽  
pp. 52-56 ◽  
Author(s):  
Robert Bosmans ◽  
Pierre Oger
Keyword(s):  
Male Dimorphism

scholarly journals Male dimorphism of a neotropical arachnid: harem size, sneaker opportunities, and gonadal investment

2012 ◽  
Vol 23 (4) ◽  
pp. 827-835 ◽  
Author(s):  
Roberto Munguía-Steyer ◽  
Bruno A. Buzatto ◽  
Glauco Machado
Keyword(s):  
Male Dimorphism ◽  
Harem Size

Notes on Phalangiidae (Arachnida: Opiliones) of southern Africa with description of new species and comments on within-species variation

Zootaxa ◽  
2017 ◽  
Vol 4272 (2) ◽  
pp. 236
Author(s):  
CHRISTOPHER K. TAYLOR
Keyword(s):  
South Africa ◽  
New Species ◽  
Body Size ◽  
Southern Africa ◽  
Limpopo Province ◽  
Species Variation ◽  
Male Dimorphism ◽  
California Academy ◽  
Academy Of Sciences ◽  
A New Species

Notes are provided on a collection of Afrotropical harvestmen (Opiliones: Palpatores: Phalangiidae) from the California Academy of Sciences. A new species of Rhampsinitus, R. conjunctidens n. sp., is described from Limpopo province of South Africa. Rhampsinitus flavobrunneus Staręga 2009 and R. silvaticus Lawrence 1931 are recognised as junior synonyms of R. nubicolus Lawrence 1963 and R. vittatus Lawrence 1931, respectively. Both R. conjunctidens and R. nubicolus are recognised as exhibiting strong male dimorphism with major males exhibiting larger body size and greatly enlarged chelicerae relative to minor males; minor males cannot be readily identified to species without examination of genitalia. A discussion is also provided on generic boundaries within Afrotropical Phalangiidae, and a generic key to males of the region is presented.

scholarly journals Life-History Differences Favor Evolution of Male Dimorphism in Competitive Games

2014 ◽  
Vol 183 (2) ◽  
pp. 188-198 ◽  
Author(s):  
Isabel M. Smallegange ◽  
Jacob Johansson
Keyword(s):  
Life History ◽  
Male Dimorphism ◽  
Competitive Games

Conditional male dimorphism and alternative reproductive tactics in a Neotropical arachnid (Opiliones)

2010 ◽  
Vol 25 (2) ◽  
pp. 331-349 ◽  
Author(s):  
Bruno A. Buzatto ◽  
Gustavo S. Requena ◽  
Rafael S. Lourenço ◽  
Roberto Munguía-Steyer ◽  
Glauco Machado
Keyword(s):  
Alternative Reproductive Tactics ◽  
Male Dimorphism ◽  
Reproductive Tactics

scholarly journals Sexual Dimorphism in White Campion: Deletion on the Y Chromosome Results in a Floral Asexual Phenotype

Genetics ◽  
1999 ◽  
Vol 151 (3) ◽  
pp. 1187-1196 ◽  
Author(s):  
Isabelle Farbos ◽  
Jacky Veuskens ◽  
Boris Vyskot ◽  
Margarida Oliveira ◽  
Stefan Hinnisdaels ◽  
...  
Keyword(s):  
Sexual Dimorphism ◽  
Y Chromosome ◽  
Gamma Ray ◽  
Functional Organization ◽  
Male Dimorphism ◽  
Developmental Defects ◽  
White Campion ◽  
Wild Type Female ◽  
Default State ◽  
Gamma Ray Irradiation

AbstractWhite campion is a dioecious plant with heteromorphic X and Y sex chromosomes. In male plants, a filamentous structure replaces the pistil, while in female plants the stamens degenerate early in flower development. Asexual (asx) mutants, cumulating the two developmental defects that characterize the sexual dimorphism in this species, were produced by gamma ray irradiation of pollen and screening in the M1 generation. The mutants harbor a novel type of mutation affecting an early function in sporogenous/parietal cell differentiation within the anther. The function is called stamen-promoting function (SPF). The mutants are shown to result from interstitial deletions on the Y chromosome. We present evidence that such deletions tentatively cover the central domain on the (p)-arm of the Y chromosome (Y2 region). By comparing stamen development in wild-type female and asx mutant flowers we show that they share the same block in anther development, which results in the production of vestigial anthers. The data suggest that the SPF, a key function(s) controlling the sporogenous/parietal specialization in premeiotic anthers, is genuinely missing in females (XX constitution). We argue that this is the earliest function in the male program that is Y-linked and is likely responsible for “male dimorphism” (sexual dimorphism in the third floral whorl) in white campion. More generally, the reported results improve our knowledge of the structural and functional organization of the Y chromosome and favor the view that sex determination in this species results primarily from a trigger signal on the Y chromosome (Y1 region) that suppresses female development. The default state is therefore the ancestral hermaphroditic state.

scholarly journals Sexual Selection on Population-level Mating Opportunities Drives Morph Ratios in a Fig Wasp with Extreme Male Dimorphism

2020 ◽  
Author(s):  
James M. Cook
Keyword(s):  
Population Level ◽  
Quantitative Prediction ◽  
Fig Wasp ◽  
Wing Polymorphism ◽  
Fig Wasps ◽  
Conditional Strategy ◽  
Male Dimorphism ◽  
Wasp Species ◽  
Mating Opportunities ◽  
Morph Ratios

Abstract Background Alternative mating tactics are widespread in animals and associated with extreme morphological polymorphism in some insects. Some fig wasps have both highly modified wingless males and dispersing winged males. Wingless males mate inside figs before females disperse, while winged males mate elsewhere after dispersal. Hamilton proposed a model for this system with morphs determined by alternative alleles. This has an equilibrium where the proportion of winged males equals the proportion of females dispersing unmated; i.e. the proportion of matings they obtain. Previously, we have shown qualitative support for this prediction across nine fig wasp species. Here I test the quantitative prediction in a population of the fig wasp Pseudidarnes minerva. In addition, while Hamilton envisaged simple Mendelian strategies, some fig wasp species with two wingless male morphs (but no winged males) show a conditional strategy with morph determination influenced by the number of wasps developing in a patch - I also test for this pattern in P. minerva. Results I sampled 114 figs that contained a mean of 2.1 P. minerva wasps from 44 trees across four sites in Sydney, Australia. At the whole population level, the proportion of winged males (0.84 or 0.79 corrected for sampling bias) did not differ significantly from the proportion of unmated females (0.84), providing strong quantitative support for the prediction of Hamilton’s model. In addition, there was no evidence for other factors, such as local mate competition or fighting between wingless males, that could violate simplifying assumptions of the model. Meanwhile, the proportion of winged males was not correlated with the number of wasps per fig, providing no evidence for a conditional strategy. Conclusions Morph ratios in P. minerva are consistent with Hamilton’s simple Mendelian strategy model, where morph ratios are set by average mating opportunities at the population level. This contrasts with some fig wasps from another subfamily that show conditional morph determination, allowing finer scale adaptation to fig-level mating opportunities. However, these conditional cases do not involve wing polymorphism. Male polymorphism is common and variable in fig wasps and has evolved independently in multiple lineages with apparently different underlying mechanisms.

A new type of male dimorphism with ergatoid and short-winged males in Cardiocondyla cf. kagutsuchi

2005 ◽  
Vol 52 (3) ◽  
pp. 274-281 ◽  
Author(s):  
K. Yamauchi ◽  
Y. Asano ◽  
B. Lautenschläger ◽  
A. Trindl ◽  
J. Heinze
Keyword(s):  
Male Dimorphism ◽  
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