Toxic males: Density‐dependent male mating harassment can explain geographic parthenogenesis

Two very basic ideas in sexual selection are heavily influenced by numbers of potential mates: the evolution of anisogamy, leading to sex role differentiation, and the frequency dependence of reproductive success that tends to equalize primary sex ratios. However, being explicit about the numbers of potential mates is not typical to most evolutionary theory of sexual selection. Here, we argue that this may prevent us from finding the appropriate ecological equilibria that determine the evolutionary endpoints of selection. We review both theoretical and empirical advances on how population density may influence aspects of mating systems such as intrasexual competition, female choice or resistance, and parental care. Density can have strong effects on selective pressures, whether or not there is phenotypic plasticity in individual strategies with respect to density. Mating skew may either increase or decrease with density, which may be aided or counteracted by changes in female behaviour. Switchpoints between alternative mating strategies can be density dependent, and mate encounter rates may influence mate choice (including mutual mate choice), multiple mating, female resistance to male mating attempts, mate searching, mate guarding, parental care, and the probability of divorce. Considering density-dependent selection may be essential for understanding how populations can persist at all despite sexual conflict, but simple models seem to fail to predict the diversity of observed responses in nature. This highlights the importance of considering the interaction between mating systems and population dynamics, and we strongly encourage further work in this area.

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Density-dependent mating behaviors reduce male mating harassment in locusts

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2104673118 ◽

2021 ◽

Vol 118 (42) ◽

pp. e2104673118

Author(s):

Koutaro Ould Maeno ◽

Cyril Piou ◽

Sidi Ould Ely ◽

Sid’Ahmed Ould Mohamed ◽

Mohamed El Hacen Jaavar ◽

...

Keyword(s):

Gravid Female ◽

Male Mating ◽

Group Separation ◽

Density Dependent ◽

Gregarious Behavior ◽

Open Ground ◽

Pair Mating ◽

Behavioral Group ◽

Mating Behaviors ◽

Gravid Females

Male mating harassment may occur when females and males do not have the same mating objectives. Communal animals need to manage the costs of male mating harassment. Here, we demonstrate how desert locusts in dense populations reduce such conflicts through behaviors. In transient populations (of solitarious morphology but gregarious behavior), we found that nongravid females occupied separate sites far from males and were not mating, whereas males aggregated on open ground (leks), waiting for gravid females to enter the lekking sites. Once a male mounted a gravid female, no other males attacked the pair; mating pairs were thereby protected during the vulnerable time of oviposition. In comparison, solitarious locusts displayed a balanced sex ratio in low-density populations, and females mated irrespective of their ovarian state. Our results indicate that the mating behaviors of desert locusts are density dependent and that sex-biased behavioral group separation may minimize the costs of male mating harassment and competition.

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Density-dependent costs and benefits of male mating success in a wild insect

10.1101/733832 ◽

2019 ◽

Author(s):

Petri T. Niemelä ◽

Stefano Tiso ◽

Niels J. Dingemanse

Keyword(s):

Mating Success ◽

Allee Effect ◽

Local Density ◽

Field Cricket ◽

Male Mating ◽

Male Mating Success ◽

Costs And Benefits ◽

Density Dependent ◽

Effect Theory ◽

Local Densities

AbstractSocial environments are important determinant of fitness, particularly when same-sex local densities shape both mating success and survival costs.We studied how mating success varied across a range of naturally occurring local male densities in wild field cricket males, Gryllus campestris, monitored by using fully automated RFID-surveillance system. We predicted that mating success as a function of local density follow a concave pattern predicted by the Allee-effect theory. As increasing density should reduce per capita predation and parasitism risk, we predicted that males generally having high mating success in low (versus high) local density live less long. Finally, we predicted that males on average occurred in local densities where their mating success is highest.Male mating success followed a density-dependent pattern predicted by the Allee-effect theory. Males also differed in the local density where their mating success was highest. This variation explained longevity and total fitness: males with high mating success in low local density lived longer and had higher total mating success. Finally, we found no evidence of males occupying local densities in which their mating success is highest.Our study suggest that density-dependent plasticity in mating success is under selection: males having high mating success in low density, but low mating success in high density, lived longer and had higher overall mating success. We thus provide novel insights, with unseen detail, about individual differences in density-dependent mating success and, costs and benefits related to variation in mating success in the wild. Finally, our study also highlights that specific statistical approaches are needed to firmly study the costs and benefits associated with the traits that are repeatedly expressed across range of environments.

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Density‐Dependent Male Mating Harassment, Female Resistance, and Male Mimicry

The American Naturalist ◽

10.1086/598491 ◽

2009 ◽

Vol 173 (6) ◽

pp. 709-721 ◽

Cited By ~ 109

Author(s):

Thomas P. Gosden ◽

Erik I. Svensson

Keyword(s):

Male Mating ◽

Female Resistance ◽

Density Dependent

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The Effects of the sphragis on male and female genitalia in Acraea (Nymphalidae) butterflies

UF Journal of Undergraduate Research ◽

10.32473/ufjur.v22i0.121244 ◽

2020 ◽

Vol 22 ◽

Author(s):

Shannon L Summers ◽

Akito Y Kawahara ◽

Ana P. S. Carvalho

Keyword(s):

Interspecific Variation ◽

Sperm Storage ◽

Male Mating ◽

Museum Collections ◽

Storage Organ ◽

Mating Plug ◽

Males And Females ◽

Comparison And Analysis ◽

Imagej Software ◽

Sexually Antagonistic Coevolution

Male mating plugs have been used in many species to prevent female re-mating and sperm competition. One of the most extreme examples of a mating plug is the sphragis, which is a large, complex and externalized plug found only in butterflies. This structure is found in many species in the genus Acraea (Nymphalidae) and provides an opportunity for investigation of the effects of the sphragis on the morphology of the genitalia, which is poorly understood. This study aims to understand morphological interspecific variation in the genitalia of Acraea butterflies. Using specimens from museum collections, abdomen dissections were conducted on 19 species of Acraea: 9 sphragis bearing and 10 non-sphragis bearing species. Genitalia imaging was performed for easier comparison and analysis and measurements of genitalia structures was done using ImageJ software. Some distinguishing morphological features in the females were found. The most obvious difference is the larger and more externalized copulatory opening in sphragis bearing species, with varying degrees of external projections. Females of the sphragis bearing species also tend to have a shorter ductus (the structure that connects the copulatory opening with the sperm storage organ) than those without the sphragis. These differences may be due to a sexually antagonistic coevolution between the males and females, where the females evolve larger and more difficult to plug copulatory openings and the males attempt to prevent re-mating with the sphragis.

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Urbanization impacts on production and recruitment of Fundulus heteroclitus in salt marsh creeks

Marine Ecology Progress Series ◽

10.3354/meps13378 ◽

2020 ◽

Vol 645 ◽

pp. 187-204

Author(s):

PJ Rudershausen ◽

JA Buckel

Keyword(s):

Salt Marsh ◽

Salt Marshes ◽

Fundulus Heteroclitus ◽

Multiple Factor Analysis ◽

Southeastern Usa ◽

Density Dependent ◽

Dependent Relationship ◽

Juvenile Abundance ◽

The Relationship ◽

Throw Trap

It is unclear how urbanization affects secondary biological production in estuaries in the southeastern USA. We estimated production of larval/juvenile Fundulus heteroclitus in salt marsh areas of North Carolina tidal creeks and tested for factors influencing production. F. heteroclitus were collected with a throw trap in salt marshes of 5 creeks subjected to a range of urbanization intensities. Multiple factor analysis (MFA) was used to reduce dimensionality of habitat and urbanization effects in the creeks and their watersheds. Production was then related to the first 2 dimensions of the MFA, month, and year. Lastly, we determined the relationship between creek-wide larval/juvenile production and abundance from spring and abundance of adults from autumn of the same year. Production in marsh (g m-2 d-1) varied between years and was negatively related to the MFA dimension that indexed salt marsh; higher rates of production were related to creeks with higher percentages of marsh. An asymptotic relationship was found between abundance of adults and creek-wide production of larvae/juveniles and an even stronger density-dependent relationship was found between abundance of adults and creek-wide larval/juvenile abundance. Results demonstrate (1) the ability of F. heteroclitus to maintain production within salt marsh in creeks with a lesser percentage of marsh as long as this habitat is not removed altogether and (2) a density-dependent link between age-0 production/abundance and subsequent adult recruitment. Given the relationship between production and marsh area, natural resource agencies should consider impacts of development on production when permitting construction in the southeastern USA.

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