Some Clues to Great Basin Postpluvial Climates Provided by Oak Distributions

Cottam, Walter P.; Tucker, John M.; Drobnick, Rudy

doi:10.2307/1929752

Cited by 35 publications

(20 citation statements)

References 12 publications

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“…A., fi (1, 2,%35), % a 3J (2, 79 9), QLU2Ia.. (5,11) andQ. stJata (3, 4, Table 1, and characters (given above the short vertical bars) as in Table 2. 1 6 3B i i I virginiana in Travis Co., Texas, is especially interesting, as Q. virginiana, an evergreen species, is very different morphologically from the deciduous oak species and the two groups never form extensive hybrid swarms (30).…”

Section: Discussionmentioning

confidence: 99%

“…Oak species are interfertile in many combinations, and natural hybrids may be formed between pairs of species that are very different from one another both morphologically and physiologically (11)(12)(13). Although some pairs of interfertile species show strong ecological separation (14,15), many interfertile species pairs show extensive ecological overlap; these may form mixed stands over extensive areas of sympatry and remain distinct despite occasional hybridization.…”

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confidence: 99%

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Interspecific gene flow in sympatric oaks.

Whittemore

Schaal

1991

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

350

269

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Variation of chloroplast DNA and nuclear ribosomal DNA (DNA encoding ribosomal RNA) was studied for five species of white oak native to the eastern United States. Although these species differ in many morphological characters and have different (though overlapping) geographical ranges and ecological tolerances, they are interfertile and often grow in mixed stands, and hybrids are occasionally found in nature. AU individuals studied were morphologically typical members of their respective species-i.e., showed no evidence of recent hybrid ancestry. Restriction site markers in the chloroplast DNA reveal several clear cases of localized gene exchange between species, showing that there is appreciable gene flow between sympatric species in this group. One length variant of the nuclear ribosomal DNA, however, is species specific. The sharp morphological and ecological differences between the species, together with the one ribosomal DNA variant, suggest that nuclear genes may be exchanged less freely between species than are chloroplast genotypes.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Interspecific gene flow in sympatric oaks.

Whittemore

Schaal

1991

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

350

269

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“…While there is species overlap and frequent hybridization at the southern portions of the distribution of Q gambelii, the occurrence of long-lived hybrids between Q gambelii and Q turbinella 300 km north of the northernmost Q turbinella is unusual and has been the focus of paleoecological interest (Drobnik, 1958). Cottam et al (1959) proposed that cold winter temperatures were the primary factor restricting the distribution of Q turbinella to the southerly latitudes and that these hybrids were remnants of a warmer postpluvial climate. While not focusing specifically on the remnant oak hybrids, Neilson and Wullstein (1983) concluded that a combination of spring freezes and summer moisture stress restricted the northerly distributions of both Q gambelii and Q turbinella.…”

Section: Introductionmentioning

confidence: 99%

Ecophysiological factors contributing to the distributions of several Quercus species in the intermountain west

Ehleringer

Phillips

1996

Ann. For. Sci.

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Summary — Aspects of the water relations of three oak species (Quercus gambelii, Q turbinella and Q macrocarpa) and their hybrids (Q gambelii x turbinella, Q gambelii x macrocarpa) were observed under common garden conditions in northern Utah, USA. In the absence of summer moisture inputs, Q macrocarpa and Q turbinella were unable to maintain active gas exchange through the day; following an early morning peak, leaf conductances to water vapor remained very low through the remainder of the day. In contrast, Q gambelii and the hybrids were able to maintain high leaf conductances throughout this period. Consistent with these observations, Q gambelii is thought to have a root system penetrating to the deeper, winter-recharged layers, a feature apparently absent in both Q macrocarpa or Q turbinella. Based on current hybrid distributions, both Q turbinella and Q macrocarpa once extended into drier more northerly regions than they occupy at present. When these parents retreated, they left behind hybrids with Q gambelii, which do not depend on monsoonal moisture input. Leaf size, leaf longevity, carbon isotope ratio, and minimum winter temperatures appear not to be correlated with the absence of Q macrocarpa and Q turbinella from summer-dry habitats. Instead it appears that reliance on summer monsoon events is one of the critical factors influencing loss of these oaks from summer-dry sites in the intermountain west.

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“…2), an evergreen sclerophyllous white oak. The distribution of relic hybrids between these two species, which persist north of the present range of Q. turbinella, has been attributed to a more northerly distribution of that species during a warmer Holocene climate, the Hypsithermal (Cottam, Tucker & Drobnick, 1959;Deevey & Flint, 1957). Although Q. gambelii and Q. turbinella have long been thought to be key indicators of Holocene climatic and biogeographic changes (Christensen, 1949;Cottam et al, 1959;Grover, Richardson & Southard, 1970), the factors controlling their distributions remain obscure, and comprise the focus of this study.…”

Section: Introductionmentioning

confidence: 99%

“…Species restricted to sexual reproduction must complete the sexual cycle in order just to maintain a geographic distribution, as well as to extend their range. Both oak species, however, possess the ability to form extensive clones, which may persist for thousands of years through persistent suckering (Muller, 1951;Brown, 1958;Cottam et al, 1959). Thus, asexual reproduction might be sufficient to maintain a static geographic distribution ......... Little, 1971;Mitchell, 1976).…”

Section: Introductionmentioning

confidence: 99%