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7/14/2009 5:02:37 PM
Creation date
5/20/2009 10:35:04 AM
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UCREFRP
UCREFRP Catalog Number
9613
Author
Desert Fishes Council.
Title
Proceedings of the Desert Fishes Council Volume XXVII 1995 Annual Symposium.
USFW Year
1995.
USFW - Doc Type
Ingram, Texas.
Copyright Material
NO
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PxocEmrr-res op THiE DESERT Fist Es Courrcn., 1995 SnmposRim Voi uha XXVII - PvsusHED 1996 <br />Geographic Variation in Life History Traits <br />of Gambusia Species <br />by Clark Hubbs <br />Department of Zoology <br />The University of Texas at Austin <br />Austin, Texas, USA 78712 <br />ABSTRACT <br />Populations of Gambusia af"inis differ substantially in predation on newborns, birth weight, and <br />interbrood interval. Populations of G. geiseri also differ significantly, but to a lesser degree, in the same three <br />factors. Populations of G. nobilis differ in predation and birth weight. These factors are not concordant <br />among species and localities; thus these variations are genetic, not environmental. Overall, G. afflnis is less <br />predaceous, has less heavy young, and has shorter interbrood intervals than G. nobilis, and G. geis' is <br />intermediate. However, the factors can be reversed by choosing extreme populations. Data are available <br />on interbrood intervals for six species; they range from long to short by G. nobihs, G. heterochir, G. gaigei, G. <br />geiseri, G. spedwa, and G. afinis. In the same sequence, birth weights vary from heavy to light and predation <br />rates vary from major to less. However, intraspecific variation is not correlated among these factors. <br />Predation susceptibility varies similarly with the heavier newborn being less likely to be eaten than the <br />lighter newborns. However, predation on the relatively heavy but less active Poecilia young is the greatest <br />of all. <br />RESUMEN <br />Las poblaciones de Gamhwia afinis difieren substancialmente en la depredaci6n de reciennacidos, peso <br />al momento de nacer a intervalo de las gestaciones. Las poblaciones de G. geiseri tambien difieren <br />significativamente, pero a un grado meno, en los mismos tres factores. Las poblaciones de G. nobilis difieren <br />en depredaci6n y peso al momento de nacimiento. Estos factores no son concordantes entre especies y <br />localidades; por to tanto estos variaciones son basadas en genetica, no en medio ambiente. En general G. <br />affinis es menos depredador, tiene crias con menos peso y tiene intervalos de gestaci6n mas cortos que G. <br />nobilis, mientras tanto G. geiseri se encuentra entre ambos. Sin embargo, los factores pueden ser reversidos <br />al escoger poblaciones extremas. Data de los intervalos de gestaci6n de seis especies es disponible; estos se <br />extienden de largos a cortos de las especies G. nobilis, G. heterochir, G. gaigei, G. geiseri, G. speciosa y G. afnis. <br />En las misma sequencias, el peso al momento de nacimiento varta de pesado a liviano y las proporciones <br />de depredaci6n varian de mayor a menor. Sin embargo, variaci6n intraespecifica no esta correlacionada <br />entre estos factores. Susceptibilidad en la depredaci6n varia similarmente con )as crias que son mas pesadas <br />al haber menos posibilidad de ser comidos que los son mas ligeros. Sin embargo, depredaci6n en las <br />relativamente pesadas pero menos activas crias de Poecilia es la mas grande de todas.
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