Neotenic Salamanders, Ambystoma tigrinum, in the Elk Mountains of Colorado

Levi, Herbert W.; Levi, Lorna R.

doi:10.2307/1440311

Cited by 14 publications

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“…However, these examples are cases where animals remove structures facultatively in relatively specific situations. Here, we document a case in which all males of the species remove a reproductive organ in an obligatory manner, thus representing a case of dramatic evolutionary change in behavior.Although sexual size dimorphism is common in spiders (15-17), it is extreme in the cobweb spider, Tidarren (Araneae, Theridiidae) (18)(19)(20). In this genus, sexual size dimorphism results from a decrease in male size (19,21,22) and an increase in female size (20).…”

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Overcoming an evolutionary conflict: Removal of a reproductive organ greatly increases locomotor performance

Ramos

Irschick

Christenson

2004

Proc. Natl. Acad. Sci. U.S.A.

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One potential consequence of sexual size dimorphism is conflict among characters. For example, a structure evolved for reproduction can impair performance during other activities (e.g., locomotion). Here we provide quantitative evidence for an animal overcoming an evolutionary conflict generated by differential scaling and sexual size dimorphism by obligatorily removing an undamaged reproductive organ, and thus dramatically enhancing its locomotor performance. The spider genus Tidarren (Araneae, Theridiidae) is interesting because, within several species presenting extreme sexual size dimorphism (males representing Ϸ1% of the total mass of the female), males voluntarily remove one of their two disproportionately large pedipalps (modified copulatory organs; a single one represents Ϸ10% of the body mass in an adult) before achieving sexual maturity. Whether the left or right pedipalp is removed appears to be random. Previous researchers have hypothesized that pedipalp removal might enhance locomotor performance, a prediction that has remained untested. We found that, for male Tidarren sisyphoides, maximum speed increased (44%) significantly and endurance increased (63%) significantly after pedipalp removal. Furthermore, spiders with one pedipalp moved Ϸ300% greater distances before exhaustion and had a higher survival after exertion than those with two pedipalps. Removal of the pedipalp may have evolved in male Tidarren because of enhanced abilities to search for females (higher endurance and survival after exertion) and to out-compete rival males on the female's web (higher maximum speed). Our data also highlight how the evolution of conflicts can result in the evolution of a novel behavior.A central tenet of optimality theory is that natural selection will optimize structure and performance resulting in an overall highly fit organism (1, 2). Many studies, however, have shown that the evolution of high performance in one task can lead to decreased performance during another task (e.g., refs. 3-5). In extreme cases of such apparent conflicts, a structure evolved for one activity can substantially impair performance during another activity. For example, Darwin (6) described how sexual selection for sex differences might lead to such functional conflicts, particularly in males. He depicted how the relatively elaborate feathers in some male birds result in enhanced reproductive success via female mate choice, yet also reduces or constrains flight capacities, thus potentially making the animal more susceptible to predators (7). A relatively unexplored area is how organisms cope with these constraints imposed by factors such as sexual selection, natural selection, or allometry. One view of constraints is that they limit or hinder morphological or behavioral change, but another possibility is that constraints can result in a novel phenotype or behavior (8, 9). For example, as plethodontid salamanders undergo evolutionary miniaturization (become smaller), they shift from a terrestrial to an arboreal lifestyle (10). This ...

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confidence: 99%

“…Although sexual size dimorphism is common in spiders (15-17), it is extreme in the cobweb spider, Tidarren (Araneae, Theridiidae) (18)(19)(20). In this genus, sexual size dimorphism results from a decrease in male size (19,21,22) and an increase in female size (20).…”

mentioning

confidence: 99%

Overcoming an evolutionary conflict: Removal of a reproductive organ greatly increases locomotor performance

Ramos

Irschick

Christenson

2004

Proc. Natl. Acad. Sci. U.S.A.

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“…L'aridité du domaine terrestre environnant un milieu aqua tique, bien oxygéné et sans prédateurs, est, selon divers auteurs, favorable à la néoténie partielle et à la paedogenèse. C'est du moins ce que Carpenter (1953), Levi et Levi (1955), Schuierer (1958), Brandon et Bremer (1967), Larson (1968) et Sprules (1974 envisa gent pour expliquer les paedogénèses de divers Ambystoma et de Dicamptodon ensatus en Amérique du Nord. L'influence de ce facteur sur les Urodèles ne peut être négli gée, étant donné leur faible protection contre la dessiccation.…”

Section: Conclusion Et Disr:llssionunclassified

Les populations néoténiques de Triturus helveticus Raz. des Causses et du Bas-Languedoc. II. Écologie

Gabrion¹,

Sentein²,

Gabrion³

1978

revec

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The physical, chemical, and biotic characteristics of the ponds where neotenic populations of Palmate newts are found in Southern France are described. The frequency of neoteny is high in permanent ponds, at an altitude ranging from 400 to 700 m, on arid limestone plateaux with a yearly rainfall of 1500-2000 mm. In such areas there are large seasonal variations of water temperature, ranging from + 1 to + 28°C, water remaining cold (below + 15°C) for 8 to 10 months during the year. The saline content of water is low, as shown by conductivity figures (less than 200 μmhos/cm/cm²). No iodine deficiency was ever found in the ponds of the study area. A correlation has been found between the frequency of neoteny and the water concentration in Ca, Mg and particularly K (which may account for 35-40 % of the cations). The aridity of the area surrounding the pools can also contri¬ bute to the selection of neotenic individuals, paedogenesis being of obvious adaptive value in such an environment.

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Alkylpyridines and Arylpyridines

Micetich¹

1974

Chemistry of Heterocyclic Compounds: A Series of Monographs

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Neotenic Salamanders, Ambystoma tigrinum, in the Elk Mountains of Colorado

Cited by 14 publications

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Overcoming an evolutionary conflict: Removal of a reproductive organ greatly increases locomotor performance

Overcoming an evolutionary conflict: Removal of a reproductive organ greatly increases locomotor performance

Les populations néoténiques de Triturus helveticus Raz. des Causses et du Bas-Languedoc. II. Écologie

Alkylpyridines and Arylpyridines

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