Sexual selection in spiders

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A male Eresus sandaliatus EresusSandaliatusHogeVeluwe.JPG
A male Eresus sandaliatus

Sexual selection in spiders shows how sexual selection explains the evolution of phenotypic traits in spiders. Male spiders have many complex courtship rituals and have to avoid being eaten by the females, with the males of most species surviving only a few matings and consequently having short life-spans.

Contents

Pre-copulatory mate choice processes have been observed in a wide range of spider species, including Stegodyphus lineatus, Argiope aurantia, Schizocosa floridana, Hygrolycosa rubrofasciata, and Schizocosa stridulans. [1] [2] [3] [4] [5]

Sexual selection occurs after copulation as well as before copulation. [6] Post-copulatory sexual selection involves sperm competition and cryptic female choice. Sperm competition occurs when the sperm of more than one male competes to fertilize the egg of the female. Cryptic female choice involves the expelling of a males sperm during or after copulations. [7]

Male to male competition

Thomisidae Thomisidae sp.jpg
Thomisidae
Misumena vatia Goldenrod Spider.jpg
Misumena vatia
Nephila clavipes Golden silk orb-weaver spider Nephila clavipes) female.jpg
Nephila clavipes

Size is a factor in the reproductive success of males with species such as Stegodyphus lineatus, Argiope aurantia and Argyroneta aquatica showing sexual dimorphism, beneficial for larger males, stronger and more aggressive, who fight off the smaller ones using their large chelicerae and forelegs. [1] [8] This leads to a decrease in the paternal success for smaller males since they are unable to gain access to females. [9] In Argiope aurantia males can lose legs in combat, with the loss more prevalent in smaller males, evidence that larger males are favored in male-to-male competition. [2] In the water spider Argyroneta aquatica, where males and females permanently live in the water [10] the males are larger, indicating sexual selective pressures for large body size. The large male water spiders are more mobile, helping them obtain more females.

Sexual selection provides benefits to smaller male spiders under certain conditions, such as Misumena vatia and Nephila clavipes , whose smaller males climb faster to reach their mates: [11] [12] Explained by the gravity hypothesis, [11] outcompeting larger males thus having more reproductive success, [12] especially when females live in high patches of flowers, [12] whereas females live in low lying areas, larger males are favored. [2]

In spiders like Tetragnathidae, Araneidae, Thomisidae and Pholicidae [11] there is an optimal body size that favors climbing speed. Smaller males will have an advantage over the largest males of the species, however the smallest male will not be the fastest climber. [12] This optimal body size for climbing is observed in different males from the same species express phenotypes, weapons such as chelicerae, teeth or even legs to fight off competition are used to fight off oncoming rivals, with larger bodied spiders contained larger chelicerae. [8] In most cases body size correlated with mating success. [1] This is observed in Lysommanes viridis , whose males display weapons that are very pronounced in comparison with females and selected to help males fight off competition. [8]

The time it takes to develop is crucial to the overall fitness of a spider. This idea is true, however does not mean that larger males will always have better fitness. In Latrodectus hasselti , larger males outcompete smaller males by getting to the females web first. However, these large male spiders have long development times, meaning that the larger male will need more time before being able to copulate. Smaller males tend to have a quick development time which gives them an advantage in mating with a female. This advantage correlates with high paternal success in the species Latrodectus hasselti . Larger males are able to outcompete smaller males, but not able to mate. Smaller males risk getting outcompeted, but are more likely to have paternal success. [13]

Sperm competition

Argiope aurantia Corn Spider.jpg
Argiope aurantia

Sperm competition occurs in many species, such as Unicorn catleyi , Nephila Pilipes and Argiope aurantia , [14] [15] [16] with males acting to limit it by guarding the female or inserting parts of the male genitalia into the females reproductive organs, [6] or using mating plugs [17] which come from the males seminal fluid. [18] This process is observed in the species Unicorn catleyi, for example. [14] In this species, males plug a females insemination duct with a portion of their palp that contains the ejaculatory duct called the embolus. The embolus that is found in the female's posterior receptaculum suggests that males are trying to limit sperm competition. [14]

In some spider species, such as the Nephila pilipes, multiple males try to mate with only one female. This can be harmful to the female, because it forces her to participate in energy costly matings. In response to this polyandry, the female produces mating plugs of her own to prevent too many males from copulating with her. [17]

The mating plugs transferred to females by the males are believed to be a possible cause of monogyny. [16] For example, in the spider species Argiope aurantia, males will sometimes plug a female with both pedipalps to prevent sperm competition. When this occurs, the male loses his ability to mate with more than one female. [16]

Mate choice

Phidippus putnami male Phidippus putnami male.jpg
Phidippus putnami male

Mate choice is typically displayed by females, but males can be choosy as well. Traits associated with winning competitive bouts are more likely to be chosen by females. As body size effects male-to-male competition, females will choose the male with the more efficient body size. A Wolf spider, Schizocosa floridana , females assess males based on their ability to cope with a changing environment, observing the way males adapt to differences in food availabilities at different times. Males who are able to adapt to the changes in food availability are well conditioned and usually show courtship displays such as tapping on their forelegs and waving. females choose the males who express these courtship displays and are larger in size based on predictions of the males foraging past. [3]

Courtship displays, such as degrees of ornamentation, colors, and movements, are commonly expressed in individuals of a species to attract the opposite sex. The male Hygrolycosa rubrofasciata spider displays certain signals, known as drumming, where a male taps his legs on a rough surface such as a leaf to signal he is ready to mate, [4] with its speed influencing female choice towards faster drummers. Once the females chooses the male, her body starts to shake, a signal that she is ready to mate too. Males who exhibit better drumming behavior typically are more viable. [4]

Schizocosa stridulans males have ornamentation traits in their forelegs [5] which affect their mating success. When courtship rates are high, ornamentation does not increase the reproductive rates of males because of the correlation between the aggressiveness of a spider and the degrees of ornamentation. Due to this correlation it is hypothesized that females choose males without ornamentation to avoid aggression from the males. Females are able to be choosy when courtship rates are high because they do not have to worry about missing out on copulations if there are plenty of male spiders to mate with. When courtship rates are low, males with high degrees of ornamentation are able to get to the female more quickly, thus giving them an advantage over non ornamented males. [5]

Sometimes facial color or leg brightness can play a role in mate choice. In several species of jumping spiders, including Habronattus pyrrithrix, and Cosmophasis umbratica, males show different brightness and color of body parts prior to copulation. [19] These colors can be used to the males advantage in attracting a mate. In the species Habronattus pyrrithrix, the males who have faces that are red and non bright green legs are more likely to attract a mate than males who do not, indicating that females prefer males with those particular traits. [19]

Although females from the species, Hygrolycosa rubrofasciata, Schizocosa floridana and Schizocosa stridulans tend to be the choosier sex, it is not uncommon to observe males from different spider species such as the Zygiella x-notata and Latrodectus hesperus, to be choosy as well. [3] [4] [5] [20] [21] In the orb weaving spider Zygiella x-notata, reproduction rates are affected by male choice under different conditions. [20] These external conditions depend on the amount of competition between males of the species. When competition rates are low, males mate opportunistically with as many females as possible. [20] When competition between males is high, larger males choose to mate with a large female as opposed to the smaller males who choose to mate with any female. The belief is that the advantages of larger size in competition, will give the larger males an opportunity to increase their paternal success by allowing them to be more selective of females. [20]

Sometimes males choose females who are large and better conditioned to avoid being eaten. Choosing a malnourished female can result in a male being cannibalized before copulation. [21] Cannibalism by females is often expressed as a way for females to get nutrition from their mates after copulation. [22] This cannibalistic behavior by females makes males more selective with whom to mate with. The males from the species Latrodectus hesperus show high mate preference for better conditioned females. By choosing well nourished females, males are able to increase their mating success while limiting their chance of being consumed. This is because well nourished females are less likely to eat their mates than mal-nourished females. [21]

Cryptic female choice

Cryptic female choice is a post-copulatory process of mate choice. [7] This process is observed in numerous spider species such as, Physocyclus globosus and Argiope bruennichi. [7] [23] For example in the Argiope bruennichi species, males produce energetic courtship displays prior to copulation. Regardless of the displays, females are observed to mate with multiple males. Once copulation is over the offspring of the female is more likely to have the courtship display phenotype than not. The females of this species must be cryptically discarding sperm from the non courtship males while keeping the other males sperm for copulation. [23] This allows females to mate with as many males as she wants prior to copulation, while being more choosy of males after copulation. Discarding the sperm of a male who does not perform courtship displays indicates that females feel that males who perform courtship displays have the greatest fitness. [23]

Related Research Articles

<span class="mw-page-title-main">Sperm competition</span> Reproductive process

Sperm competition is the competitive process between spermatozoa of two or more different males to fertilize the same egg during sexual reproduction. Competition can occur when females have multiple potential mating partners. Greater choice and variety of mates increases a female's chance to produce more viable offspring. However, multiple mates for a female means each individual male has decreased chances of producing offspring. Sperm competition is an evolutionary pressure on males, and has led to the development of adaptations to increase male's chance of reproductive success. Sperm competition results in a sexual conflict between males and females. Males have evolved several defensive tactics including: mate-guarding, mating plugs, and releasing toxic seminal substances to reduce female re-mating tendencies to cope with sperm competition. Offensive tactics of sperm competition involve direct interference by one male on the reproductive success of another male, for instance by mate guarding or by physically removing another male's sperm prior to mating with a female. For an example, see Gryllus bimaculatus.

<i>Trichonephila clavipes</i> Species of spider native to the Americas

Trichonephila clavipes, commonly known as the golden silk orb-weaver, golden silk spider, or colloquially banana spider, is an orb-weaving spider species which inhabits forests and wooded areas ranging from the southern US to Argentina. It is indigenous to both continental North and South America. Known for the golden color of their silk, the large size of their females, and their distinctive red-brown and yellow coloring, T. clavipes construct large, asymmetrical circular webs attached to trees and low shrubs in woods to catch small- and medium-size flying prey, mostly insects. They are excellent web-builders, producing and utilizing seven different types of silk, and they subdue their prey by injecting them with venom, as opposed to related species which immobilize their prey by wrapping them in silk first. They are not known to be aggressive towards humans, only biting out of self-defense if touched, and their relatively harmless venom has a low toxicity, posing little health concern to healthy human adults. Due to their prevalence in forests, T. clavipes may be encountered by hikers.

<span class="mw-page-title-main">Argiope bruennichi</span> Species of orb-weaver spider

Argiope bruennichi is a species of orb-web spiders distributed throughout Central and Northern Europe, North Africa, parts of Asia, and the Azores archipelago. Like many other members of the genus Argiope, it has striking yellow and black markings on its abdomen.

<i>Latrodectus hesperus</i> Species of spider

Latrodectus hesperus, the western black widow spider or western widow, is a venomous spider species found in western regions of North America. The female's body is 14–16 mm in length and is black, often with an hourglass-shaped red mark on the lower abdomen. This "hourglass" mark can be yellow, and on rare occasions, white. The male of the species is around half this length and generally a tan color with lighter striping on the abdomen. The population was previously described as a subspecies of Latrodectus mactans and it is closely related to the northern species Latrodectus variolus. The species, as with others of the genus, build irregular or "messy" webs: unlike the spiral webs or the tunnel-shaped webs of other spiders, the strands of a Latrodectus web have no apparent organization.

<i>Nephila pilipes</i> Species of spider

Nephila pilipes is a species of golden orb-web spider. It resides all over countries in East and Southeast Asia as well as Oceania. It is commonly found in primary and secondary forests and gardens. Females are large and grow to a body size of 30–50 mm, with males growing to 5–6 mm. It is the second largest of the orb-weaving spiders apart from the recently discovered Nephila komaci. The first, second, and fourth pairs of legs of juvenile females have dense hairy brushes, but these brushes disappear as the spider matures.

<span class="mw-page-title-main">Sexual conflict</span> Term in evolutionary biology

Sexual conflict or sexual antagonism occurs when the two sexes have conflicting optimal fitness strategies concerning reproduction, particularly over the mode and frequency of mating, potentially leading to an evolutionary arms race between males and females. In one example, males may benefit from multiple matings, while multiple matings may harm or endanger females, due to the anatomical differences of that species. Sexual conflict underlies the evolutionary distinction between male and female.

<span class="mw-page-title-main">Sexual cannibalism</span> Practice of animals eating their own mating partners

Sexual cannibalism is when an animal, usually the female, cannibalizes its mate prior to, during, or after copulation. It is a trait observed in many arachnid orders and several insect and crustacean clades. Several hypotheses to explain this seemingly paradoxical behavior have been proposed. The adaptive foraging hypothesis, aggressive spillover hypothesis and mistaken identity hypothesis are among the proposed hypotheses to explain how sexual cannibalism evolved. This behavior is believed to have evolved as a manifestation of sexual conflict, occurring when the reproductive interests of males and females differ. In many species that exhibit sexual cannibalism, the female consumes the male upon detection. Females of cannibalistic species are generally hostile and unwilling to mate; thus many males of these species have developed adaptive behaviors to counteract female aggression.

<i>Trichonephila plumipes</i> Species of spider

Trichonephila plumipes, the Pacific golden orb weaver, is a species of spider found in Australia, Indonesia and some Pacific Islands, which exhibits extreme sexual dimorphism through its sexual cannibalism behavior. It is sometimes called the tiger spider due to its markings which look similar to a tiger. This species was formerly called Nephila plumipes. As with other spiders from the genus Nephila, these spiders have a distinct golden web.

<span class="mw-page-title-main">Courtship display</span> Communication to start a relationship with someone or to get sexual contact

A courtship display is a set of display behaviors in which an animal, usually a male, attempts to attract a mate; the mate exercises choice, so sexual selection acts on the display. These behaviors often include ritualized movement ("dances"), vocalizations, mechanical sound production, or displays of beauty, strength, or agonistic ability.

Monogyny is a specialised mating system in which a male can only mate with one female throughout his lifetime, but the female may mate with more than one male. In this system, the males generally provide no paternal care. In many spider species that are monogynous, the males have two copulatory organs, which allows them to mate a maximum of twice throughout their lifetime. As is commonly seen in honeybees, ants and certain spider species, a male may put all his energy into a single copulation, knowing that this will lower his overall fitness. During copulation, monogynous males have adapted to cause self genital damage or even death to increase their chances of paternity.

A biological ornament is a characteristic of an animal that appears to serve a decorative function rather than a utilitarian function. Many are secondary sexual characteristics, and others appear on young birds during the period when they are dependent on being fed by their parents. Ornaments are used in displays to attract mates, which may lead to the evolutionary process known as sexual selection. An animal may shake, lengthen, or spread out its ornament in order to get the attention of the opposite sex, which will in turn choose the most attractive one with which to mate. Ornaments are most often observed in males, and choosing an extravagantly ornamented male benefits females as the genes that produce the ornament will be passed on to her offspring, increasing their own reproductive fitness. As Ronald Fisher noted, the male offspring will inherit the ornament while the female offspring will inherit the preference for said ornament, which can lead to a positive feedback loop known as a Fisherian runaway. These structures serve as cues to animal sexual behaviour, that is, they are sensory signals that affect mating responses. Therefore, ornamental traits are often selected by mate choice.

A nuptial gift is a nutritional gift given by one partner in some animals' sexual reproduction practices.

<span class="mw-page-title-main">Sexual selection in birds</span>

Sexual selection in birds concerns how birds have evolved a variety of mating behaviors, with the peacock tail being perhaps the most famous example of sexual selection and the Fisherian runaway. Commonly occurring sexual dimorphisms such as size and color differences are energetically costly attributes that signal competitive breeding situations. Many types of avian sexual selection have been identified; intersexual selection, also known as female choice; and intrasexual competition, where individuals of the more abundant sex compete with each other for the privilege to mate. Sexually selected traits often evolve to become more pronounced in competitive breeding situations until the trait begins to limit the individual's fitness. Conflicts between an individual fitness and signaling adaptations ensure that sexually selected ornaments such as plumage coloration and courtship behavior are "honest" traits. Signals must be costly to ensure that only good-quality individuals can present these exaggerated sexual ornaments and behaviors.

<span class="mw-page-title-main">Sexual selection in mammals</span> Mode of natural selection

Sexual selection in mammals is a process the study of which started with Charles Darwin's observations concerning sexual selection, including sexual selection in humans, and in other mammals, consisting of male–male competition and mate choice that mold the development of future phenotypes in a population for a given species.

<span class="mw-page-title-main">Sexual selection in scaled reptiles</span>

Sexual selection in scaled reptiles studies how sexual selection manifests in snakes and lizards, which constitute the order Squamata of reptiles. Each of the over three thousand snakes use different tactics in acquiring mates. Ritual combat between males for the females they want to mate with includes topping, a behavior exhibited by most viperids in which one male will twist around the vertically elevated fore body of its opponent and forcing it downward. It is common for neck biting to occur while the snakes are entwined.

<span class="mw-page-title-main">Sexual selection in insects</span>

Sexual selection in insects is about how sexual selection functions in insects. The males of some species have evolved exaggerated adornments and mechanisms for self-defense. These traits play a role in increasing male reproductive expectations by triggering male-male competition or influencing the female mate choice, and can be thought of as functioning on three different levels: individuals, colonies, and populations within an area.

<span class="mw-page-title-main">Sexual selection in amphibians</span> Choice of and competition for mates

Sexual selection in amphibians involves sexual selection processes in amphibians, including frogs, salamanders and newts. Prolonged breeders, the majority of frog species, have breeding seasons at regular intervals where male-male competition occurs with males arriving at the waters edge first in large number and producing a wide range of vocalizations, with variations in depth of calls the speed of calls and other complex behaviours to attract mates. The fittest males will have the deepest croaks and the best territories, with females making their mate choices at least partly based on the males depth of croaking. This has led to sexual dimorphism, with females being larger than males in 90% of species, males in 10% and males fighting for groups of females.

Cryptic female choice is a form of mate choice which occurs both in pre and post copulatory circumstances when females in certain species use physical or chemical mechanisms to control a male's success of fertilizing their ova or ovum; i.e. by selecting whether sperm are successful in fertilizing their eggs or not. It occurs in internally-fertilizing species and involves differential use of sperm by females when sperm are available in the reproductive tract.

<i>Schizocosa ocreata</i> Species of spider

Schizocosa ocreata is a species of wolf spider in the family Lycosidae that is found in North America. The Schizocosa ocreata is a spider that is most commonly known as the “brush-legged wolf spider” because of their distinct dark-colored fur-like coverings around their legs. The S. ocreata are commonly found in North American states, usually in the middle and eastern United States.

Schizocosa stridulans is a sibling species of S. ocreata and S. rovneri and is part of the wolf spider family. The name of the genus comes from the epigynum structure being lycosid and having a split T excavation. This spider is well-known for its specific leg ornamentation and courtship rituals and that is how it has been differentiated from its related species. The S. stridulans take systematic steps during its courtship ritual, which involves two independent signals. More specifically, female spiders will leave silk and pheromones to communicate that they are ready to mate.

References

  1. 1 2 3 Maklakov, A. a., Bilde, T. & Lubin, Y. Sexual selection for increased male body size and protandry in a spider. Animal Behaviour 68, 1041–1048 (2004).
  2. 1 2 3 Foellmer, M. W. & Fairbairn, D. J. Competing dwarf males: sexual selection in an orb-weaving spider. Journal of Evolutionary Biology 18, 629–41 (2005).
  3. 1 2 3 Rosenthal, M. F. & Hebets, E. a. Resource heterogeneity interacts with courtship rate to influence mating success in the wolf spider Schizocosa floridana. Animal Behaviour 84, 1341–1346 (2012).
  4. 1 2 3 4 Kotiaho, J., Alatalo, R. V, Mappes, J. & Parri, S. SEXUAL SELECTION IN A WOLF SPIDER : MALE DRUMMING ACTIVITY, BODY SIZE, AND VIABILITY. 50, 1977–1981 (1996).
  5. 1 2 3 4 Hebets, E. A., Stafstrom, J. A., Rodriguez, R. L. & Wilgers, D. J. Enigmatic ornamentation eases male reliance on courtship performance for mating success. Animal Behaviour 81, 963–972 (2011).
  6. 1 2 Eberhard, W. G. Postcopulatory sexual selection: Darwin’s omission and its consequences. Proceedings of the National Academy of Sciences of the United States of America 106 Suppl, 10025–32 (2009).
  7. 1 2 3 Peretti, a V & Eberhard, W. G. Cryptic female choice via sperm dumping favours male copulatory courtship in a spider. Journal of Evolutionary Biology 23, 271–81 (2010).
  8. 1 2 3 Tedore, C. & Johnsen, S. Weaponry, color, and contest success in the jumping spider Lyssomanes viridis. Behavioural processes 89, 203–11 (2012).
  9. ↑ Maklakov, A. a. & Lubin, Y. Indirect genetic benefits of polyandry in a spider with direct costs of mating. Behavioral Ecology and Sociobiology 61, 31–38 (2006).
  10. ↑ Schutz, D. & Taborsky, M. Sexual Selection in the Water Spider: Female Choice and Male-Male Competition. Ethology 117, 1101–1110 (2011).
  11. 1 2 3 Moya-Laraño, J., Vinković, D., Allard, C. M. & Foellmer, M. W. Optimal climbing speed explains the evolution of extreme sexual size dimorphism in spiders. Journal of Evolutionary Biology 22, 954–63 (2009).
  12. 1 2 3 4 Moya-laraño, A. J., Halaj, J. & Wise, D. H. Climbing to Reach Females : Romeo Should be Small. 56, 420–425 (2001).
  13. ↑ Kasumovic, M. M. & Andrade, M.C.B. A change in competitive context reverses sexual selection on male size. Journal of Evolutionary Biology 22, 324–33 (2009).
  14. 1 2 3 Izquierdo, M. A & Rubio, G. D. Male genital mutilation in the high-mountain goblin spider, Unicorn catleyi. Journal of insect science (Online) 11, 118, p1-8 (2011).
  15. ↑ Zhang, S., Kuntner, M. & Li, D. Mate binding: male adaptation to sexual conflict in the golden orb-web spider (Nephilidae: Nephila pilipes). Animal Behaviour 82, 1299–1304 (2011).
  16. 1 2 3 Foellmer, M. W. Broken genitals function as mating plugs and affect sex ratios in the orb-web spider Argiope aurantia. Evolutionary Ecology Research 10, 449–462 (2008).
  17. 1 2 Kuntner, M., Gregorič, M., Zhang, S., Kralj-Fišer, S. & Li, D. Mating plugs in polyandrous giants: which sex produces them, when, how and why? PLoS ONE 7, e40939 (2012).
  18. ↑ Aisenberg, A. & Barrantes, G. Sexual behavior, cannibalism, and mating plugs as sticky traps in the orb weaver spider Leucauge argyra (Tetragnathidae). Die Naturwissenschaften 98, 605–13 (2011).
  19. 1 2 Taylor, L. a., Clark, D. L. & McGraw, K. J. Condition dependence of male display coloration in a jumping spider (Habronattus pyrrithrix). Behavioral Ecology and Sociobiology 65, 1133–1146 (2010).
  20. 1 2 3 4 Bel-Venner, M. C., Dray, S., Allainé, D., Menu, F. & Venner, S. Unexpected male choosiness for mates in a spider. Proceedings: Biological Sciences 275, 77–82 (2008).
  21. 1 2 3 Johnson, J. C., Trubl, P., Blackmore, V. & Miles, L. Male black widows court well-fed females more than starved females: silken cues indicate sexual cannibalism risk. Animal Behaviour 82, 383–390 (2011).
  22. ↑ Wu, L., Zhang, H., He, T., Liu, Z. & Peng, Y. Factors influencing sexual cannibalism and its benefit to fecundity and offspring survival in the wolf spider Pardosa pseudoannulata (Araneae: Lycosidae). Behavioral Ecology and Sociobiology 67, 205–212 (2012).
  23. 1 2 3 Schneider, J. M. & Lesmono, K. Courtship raises male fertilization success through post-mating sexual selection in a spider. Proceedings: Biological Sciences 276, 3105–11 (2009).
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