scholarly journals Sperm numbers vary between inter- and intra-population matings of the grasshopper Chorthippus parallelus

2006 ◽  
Vol 2 (2) ◽  
pp. 239-241 ◽  
Author(s):  
Klaus Reinhardt
Keyword(s):  
Sexual Selection ◽  
Reproductive Isolation ◽  
Reproductive Output ◽  
Mating Effort ◽  
Sperm Number ◽  
Storage Organ ◽  
Genetic Incompatibility ◽  
Chorthippus Parallelus ◽  
Mating Signals ◽  
Crucial Assumption

Comparing the reproductive output of intra- and inter-population matings is the most common way to assess whether post-mating reproductive isolation is caused by genetic incompatibilities. Such genetic incompatibility can however, only assume that the quantity of the post-mating signals involved does not differ between intra- and inter-population matings. This assumption may not be true because sexual selection predicts reduced mating effort towards low-quality mates and in many circumstances, allopatric partners are low-quality mates. Post-mating efforts may, therefore, be reduced in inter- compared to intra-population matings. Here, I test this crucial assumption by studying variation in one post-mating trait, sperm number, in crosses of two parapatric grasshopper populations. In both populations, males transferred fewer sperm to allopatric than sympatric females. If such plasticity with respect to population is common in other post-mating traits, differences between inter- and intra-population crosses may be more frequently caused by differences in sperm number rather than gamete incompatibility. Additionally, I found that sperm numbers declined less rapidly in the female storage organ of allopatric than sympatric females but its rate differed markedly between populations. This is discussed with respect to female adaptations to male traits.

scholarly journals Local adaptation and sexual selection drive intra-island diversification in a songbird lineage: differential divergence in autosomes and sex chromosomes

2018 ◽  
Author(s):  
Yann XC Bourgeois ◽  
Joris AM Bertrand ◽  
Boris Delahaie ◽  
Hélène Holota ◽  
Christophe Thébaud ◽  
...  
Keyword(s):  
Sexual Selection ◽  
Natural Selection ◽  
Reproductive Isolation ◽  
Local Adaptation ◽  
Sex Chromosomes ◽  
Genomic Variation ◽  
Color Variation ◽  
Mating Signals ◽  
Genome Wide

AbstractRecently diverged taxa showing marked phenotypic and ecological diversity are optimal systems to test the relative importance of two major evolutionary mechanisms, adaptation to local ecological conditions by natural selection, or mechanisms of reproductive isolation such as assortative mating mediated by sexually selected mating signals or post-zygotic incompatibilities. Whereas local adaptation is expected to affect many loci throughout the genome, traits acting as mating signals are expected to be located on sex chromosomes and have a simple genetic basis. We used genome-wide markers to test these predictions in Reunion Island’s gray-white eye (Zosterops borbonicus), which has recently diversified into five distinct plumage forms. Two of them correspond to a polymorphic highland population that is separated by a steep ecological gradient from three distinct lowland forms that show narrow contact zones in plumage color traits, yet no association with environmental variables. An analysis of population structure using genome-wide SNP loci revealed two major clades corresponding to highland and lowland forms, respectively, with the latter separated further into three independent lineages corresponding to plumage forms. Coalescent tests of alternative demographic scenarios provided support for divergence of highland and lowland lineages with an intensification of gene flow in the last 60,000 years. Landscapes of genomic variation revealed that signatures of selection associated with elevation are found at multiple regions across the genome, whereas most loci associated with the lowland forms are located on the Z sex chromosome. A gene ontology analysis identified TYRP1, a Z-linked color gene, as a likely candidate locus underlying color variation among lowland forms. Our results are consistent with the role of natural selection in driving the divergence of locally adapted highland populations, and the role of sexual selection in differentiating lowland forms through reproductive isolation mechanisms, showing that both modes of lineage divergence can take place at very small geographic scales in birds.

scholarly journals Sex ratio effects on reproductive strategies in humans

2015 ◽  
Vol 2 (1) ◽  
pp. 140402 ◽  
Author(s):  
Ryan Schacht ◽  
Monique Borgerhoff Mulder
Keyword(s):  
Sexual Selection ◽  
Sex Ratio ◽  
Ethnic Group ◽  
Reproductive Strategies ◽  
Situational Factors ◽  
Male Mating ◽  
Mating Effort ◽  
Short Term ◽  
Adult Sex Ratio ◽  
Using Data

Characterizations of coy females and ardent males are rooted in models of sexual selection that are increasingly outdated. Evolutionary feedbacks can strongly influence the sex roles and subsequent patterns of sex differentiated investment in mating effort, with a key component being the adult sex ratio (ASR). Using data from eight Makushi communities of southern Guyana, characterized by varying ASRs contingent on migration, we show that even within a single ethnic group, male mating effort varies in predictable ways with the ASR. At male-biased sex ratios, men's and women's investment in mating effort are indistinguishable; only when men are in the minority are they more inclined towards short-term, low investment relationships than women. Our results support the behavioural ecological tenet that reproductive strategies are predictable and contingent on varying situational factors.

scholarly journals A LIFE-HISTORY PERSPECTIVE ON SEXUAL SELECTION IN A POLYGAMOUS SPECIES

2019 ◽  
Author(s):  
Gao Ke ◽  
Michiel van Wijk ◽  
Zoe Clement ◽  
Martijn Egas ◽  
Astrid Groot
Keyword(s):  
Sexual Selection ◽  
Life History ◽  
Sperm Competition ◽  
Reproductive Output ◽  
Relative Fitness ◽  
Quadratic Model ◽  
Costs And Benefits ◽  
Bateman Gradient ◽  
Multiple Matings ◽  
Males And Females

Abstract Background Ever since Darwin, evolutionary biologists have studied sexual selection driving differences in appearance and behaviour between males and females. An unchallenged paradigm in such studies is that one sex (usually the male) signals its quality as a mate to the other sex (usually the female), who is choosy in accepting a partner. Here, we argue that in polygamous species these roles may change dynamically with the mating status of males and females, depending on direct reproductive costs and benefits of multiple matings, and on sperm competition. We test this hypothesis using a polygamous moth species, as in moths not males but females are the signalers and males are the responders. Results We found that multiple matings are beneficial as well as costly for both sexes. Specifically, the number of matings did not affect the longevity of males or females, but when paired with a new virgin mate every night for five nights, only 67% of the males and 14% of the females mated successfully in all five nights. The female’s reproductive output increased with multiple matings, although when paired with a new virgin male every night, additional matings beyond 3 decreased her reproductive output, so that the Bateman gradient for females fit a quadratic model better than a linear model. The male’s reproductive success was positively affected by the number of matings and a linear regression line best fit the data. Simulations of the effect of sperm competition showed that increasing last-male paternity increases the steepness of the male Bateman gradient and thus the male’s relative fitness gain from additional mating. Irrespective of last-male paternity value, the female Bateman gradient is steeper than the male one for up to three matings. Conclusion Our results suggest that choosiness in moths may well change throughout the mating season, with males being more choosy early in the season and females being more choosy after having mated at least three times. This life-history perspective on the costs and benefits of multiple matings for both sexes sheds new light on sexual selection forces acting on sexual signals and responses.

scholarly journals The collapse of genetic incompatibilities in a hybridizing population

2021 ◽  
Author(s):  
Tianzhu Xiong ◽  
James L MALLET
Keyword(s):  
Gene Regulation ◽  
Reproductive Isolation ◽  
Genetic Drift ◽  
Recombination Rate ◽  
Time Scale ◽  
Genetic Incompatibility ◽  
Genetic Process ◽  
Underlying Mechanisms ◽  
The Stability

Genetic incompatibility has long been considered to be a hallmark of speciation due to its role in reproductive isolation. Previous analyses of the stability of epistatic incompatibility show that it is subject to collapse upon hybridization. In the present work, we derive explicitly the distribution of the lifespan of two-locus incompatibilities, and show that genetic drift, along with recombination, is critical in determining the time scale of collapse. The first class of incompatibilities, where derived alleles separated in parental populations act antagonistically in hybrids, survive longer in smaller populations when incompatible alleles are (co)dominant and tightly linked, but collapse more quickly when they are recessive. The second class of incompatibilities, where fitness is reduced by disrupting co-evolved elements in gene regulation systems, collapse on a time scale proportional to the exponential of effective recombination rate. Overall, our result suggests that the effects of genetic drift and recombination on incompatibility's lifespan depend strongly on the underlying mechanisms of incompatibilities. As the time scale of collapse is usually shorter than the time scale of establishing a new incompatibility, the observed level of genetic incompatibilities in a particular hybridizing population may be shaped more by the collapse than by their initial accumulation. Therefore, a joint theory of accumulation-erosion of incompatibilities is in need to fully understand the genetic process under speciation with hybridization.

scholarly journals The Reproductive Microbiome: An Emerging Driver of Sexual Selection, Sexual Conflict, Mating Systems, and Reproductive Isolation

2020 ◽  
Vol 35 (3) ◽  
pp. 220-234 ◽  
Author(s):  
Melissah Rowe ◽  
Liisa Veerus ◽  
Pål Trosvik ◽  
Angus Buckling ◽  
Tommaso Pizzari
Keyword(s):  
Sexual Selection ◽  
Reproductive Isolation ◽  
Sexual Conflict ◽  
Mating Systems

scholarly journals Disposable penis and its replenishment in a simultaneous hermaphrodite

2013 ◽  
Vol 9 (2) ◽  
pp. 20121150 ◽  
Author(s):  
Ayami Sekizawa ◽  
Satoko Seki ◽  
Masakazu Tokuzato ◽  
Sakiko Shiga ◽  
Yasuhiro Nakashima
Keyword(s):  
Sexual Selection ◽  
Outer Surface ◽  
Mating Behaviour ◽  
Sperm Storage ◽  
Simultaneous Hermaphrodite ◽  
Storage Organ ◽  
Simultaneous Hermaphrodites

Although it is often thought that sexual selection is weaker in simultaneous hermaphrodites than in gonochorists, some simultaneous hermaphrodites exhibit bizarre mating behaviour. In the simultaneously hermaphroditic nudibranch Chromodoris reticulata , we found a peculiar mating behaviour, wherein the nudibranch autotomized its penis after each copulation and was able to copulate again within 24 h. To have sufficient length to be replenished for three copulations, the penis is compressed and spiralled internally. No other animal is known to repeatedly copulate using such ‘disposable penes’. Entangled sperm masses were observed on the outer surface of the autotomized penis, which is equipped with many backward-pointed spines. There is a possibility that the nudibranch removes sperm already stored in a mating partner's sperm storage organ(s).

Differential survival of allosperm by location within the female storage organ of the snail Cornu aspersum

2008 ◽  
Vol 86 (11) ◽  
pp. 1244-1251 ◽  
Author(s):  
Ronald Chase ◽  
Emily Darbyson
Keyword(s):  
Sexual Selection ◽  
Sperm Competition ◽  
Female Choice ◽  
Complex Structure ◽  
Sperm Storage ◽  
Storage Organ ◽  
Differential Survival ◽  
Cornu Aspersum ◽  
The Mean ◽  
Epithelial Wall

The sperm storage organ of terrestrial gastropod molluscs is implicated in sexual selection because it has a complex structure and it functions in a context of intense sperm competition. Received sperm are stored in spermathecal tubules. In our sample using the brown garden snail ( Cornu aspersum (Müller, 1774)) (n = 58), the mean number of tubules per animal was 16, with lengths ranging from ≤40 to 2480 μm. A hereditary influence on tubule number was indicated by clutch-dependent variations. From histological sections, we counted the spermatozoa that were present in the tubules of ex-virgin snails 1, 2, 4, and 8 weeks after mating (n = 40). Sperm were distributed, on average, across 75% of the tubules in individual snails, thus contradicting one proposed mechanism for cryptic female choice. The total number of sperm declined 66% over 8 weeks, with the largest losses incurred by sperm in the lumens of the tubules and sperm gathered in clusters. By contrast, in the same period, the numbers of sperm that were in contact with the walls of the tubules remained relatively stable. These data imply that sperm survive best when attached to the epithelial wall, either because they derive nutrition from the epithelium or because they use the epithelium as an anchor.

scholarly journals Sexual selection on color and behavior within and between cichlid populations: Implications for speciation

2012 ◽  
Vol 58 (3) ◽  
pp. 475-483 ◽  
Author(s):  
Michael J. Pauers ◽  
Jeffrey S. Mckinnon
Keyword(s):  
Sexual Selection ◽  
Mate Choice ◽  
Reproductive Isolation ◽  
Assortative Mating ◽  
Mate Preferences ◽  
Separate Experiment ◽  
Color Patterns ◽  
Male Behavior ◽  
Female Population ◽  
Different Color

Abstract Sexual selection is widely viewed as playing a central role in haplochromine cichlid speciation. Hypothetically, once divergent mate preferences evolve among populations of these fishes, reproductive isolation follows and the populations begin to behave as different species. Various studies have examined patterns of assortative mating among species and sometimes populations, but few have examined variation in directional preferences, especially among populations of the same species. We investigated mate choice behavior in two populations of Labeotropheus fuelleborni, a Lake Malawi endemic. We test whether mating preferences between populations are based on the same traits and in the same direction as preferences within populations. We examine the potential contributions of two classes of trait, color patterns and behaviors, to reproductive isolation. When females chose between either two males of their own population, or two from another, female preferences were generally similar (for the female population) across the two contexts. Mate choice patterns differed between (female) populations for a measure of color, but only modestly for male behavior. In a separate experiment we simultaneously offered females a male of their own population and a male from a different population. In these trials, females consistently preferred males from their own population, which were also the males that displayed more frequently than their opponents, but not necessarily those with color traits suggested to be most attractive in the previous experiment. Thus directional preferences for chroma and related aspects of color may be important when females are presented with males of otherwise similar phenotypes, but may play little role in mediating assortative mating among populations with substantially different color patterns. A preference for male behavior could play some role in speciation if males preferentially court same-population females, as we have observed for the populations studied herein.

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