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Pattern and theory of geographic var...

Tracy, Christopher Richard.

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Pattern and theory of geographic variation in physiology and body size in chuckwallas, Sauromalus obesus.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Pattern and theory of geographic variation in physiology and body size in chuckwallas, Sauromalus obesus./
作者:	Tracy, Christopher Richard.
面頁冊數:	150 p.
附註:	Source: Dissertation Abstracts International, Volume: 63-07, Section: B, page: 3121.
Contained By:	Dissertation Abstracts International63-07B.
標題:	Biology, Animal Physiology. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3060515
ISBN:	0493761780

Pattern and theory of geographic variation in physiology and body size in chuckwallas, Sauromalus obesus.
Tracy, Christopher Richard.

Pattern and theory of geographic variation in physiology and body size in chuckwallas, Sauromalus obesus. - 150 p.

Source: Dissertation Abstracts International, Volume: 63-07, Section: B, page: 3121.

Thesis (Ph.D.)--The University of Wisconsin - Madison, 2002.

Patterns of variation in body size of chuckwallas, sexual size dimorphism, and digestive physiology appear consistent with hypotheses about an environmental selection gradient. At lower elevations, where it is generally hotter; drier and subject to more frequent drought years, chuckwallas adopt a life history strategy of rapid energy uptake during times of resource abundance and allocation of energy toward storage, rather than somatic growth. Chuckwallas at low elevations tend to be small and have large fat stores, enabling them to survive dry years. Presumably, the reduced fecundity resulting from small size is offset by increased probability of surviving until the next reproductive season. Higher elevations have more moderate environments, with longer and more predictable growing seasons. Here, there may be relaxed pressure for storage to survive long fasts, allowing chuckwallas from higher elevations to allocate energy to somatic growth, and increasing fecundity for both sexes.

ISBN: 0493761780Subjects--Topical Terms:

1017835
Biology, Animal Physiology.

Pattern and theory of geographic variation in physiology and body size in chuckwallas, Sauromalus obesus.
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245 1 0 $a Pattern and theory of geographic variation in physiology and body size in chuckwallas, Sauromalus obesus.
300 $a 150 p.
500 $a Source: Dissertation Abstracts International, Volume: 63-07, Section: B, page: 3121.
500 $a Supervisor: Warren P. Porter.
502 $a Thesis (Ph.D.)--The University of Wisconsin - Madison, 2002.
520 $a Patterns of variation in body size of chuckwallas, sexual size dimorphism, and digestive physiology appear consistent with hypotheses about an environmental selection gradient. At lower elevations, where it is generally hotter; drier and subject to more frequent drought years, chuckwallas adopt a life history strategy of rapid energy uptake during times of resource abundance and allocation of energy toward storage, rather than somatic growth. Chuckwallas at low elevations tend to be small and have large fat stores, enabling them to survive dry years. Presumably, the reduced fecundity resulting from small size is offset by increased probability of surviving until the next reproductive season. Higher elevations have more moderate environments, with longer and more predictable growing seasons. Here, there may be relaxed pressure for storage to survive long fasts, allowing chuckwallas from higher elevations to allocate energy to somatic growth, and increasing fecundity for both sexes.
520 $a At lower elevations, chuckwallas show little sexual size dimorphism; At higher elevations, chuckwallas are more dimorphic. This suggests that overall size, and size dimorphism, reflect a balance in the relative strength of natural selection (survival) and sexual selection (reproduction). At lower elevations, survival pressures appear primary, leaving little room for sexual size dimorphism, but as survival pressures ease at higher elevations, sexual selective pressures have a relatively greater influence and may drive dimorphism.
520 $a The physiology of gut regulation also appears consistent with this paradigm. Chuckwallas at low elevations appear to have a gut regulation strategy of large organ size and high transport rates while food is available, and small organ size when it is not. This may maximize energy acquisition during short growing seasons, and minimize energy expenditures during fasting periods. The regulation is less at higher elevations, possibly to take advantage of extended, unpredictable food availability.
520 $a Comparing chuckwalla and desert iguana size patterns suggests the importance of isolated populations. While chuckwallas occur exclusively on rock outcrops separated by vast expanses of open desert, desert iguanas occur in relatively contiguous stretches of open desert. This may allow greater gene flow in desert iguanas, swamping subtle differences in selective pressures along the environmental gradient of elevation.
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773 0 $t Dissertation Abstracts International $g 63-07B.
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791 $a Ph.D.
792 $a 2002
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