The Lowland Floral Element on the Summit of Cerro Guaiquinima and Other Cerros of the Guayana Highland of Venezuela

Steyermark, Julián A.; Dunsterville, G. C. K.

doi:10.2307/2844634

Cited by 37 publications

(23 citation statements)

References 3 publications

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“…Comprehensive collecting, however, revealed that many taxa have a wider elevational range than previously thought, and that taxa from both highlands and lowlands merge at intermediate altitudes (Steyermark & Dunsterville 1980;Huber 1988). Also, the myth of total geographical isolation has been questioned, because large valleys and ridges effectively connect some tepui summits with the surrounding uplands (Huber 1988).…”

Section: Origin and Evolution Of The Unique Biota Of The Pantepui Regmentioning

confidence: 95%

“…The idea of evolution in isolation therefore progressively lost credibility and the Vertical Displacement hypothesis emerged. According to Steyermark & Dunsterville (1980), connection between the ecosystems of the tepui summits is possible. They propose two mechanisms: (1) migrations using river valleys, and (2) vertical displacement during Pleistocene glacial-interglacial cycles.…”

Section: Origin and Evolution Of The Unique Biota Of The Pantepui Regmentioning

confidence: 99%

See 1 more Smart Citation

Biogeography of the Lost World (Pantepui region, northeastern South America): Insights from bryophytes

Désamoré¹,

Vanderpoorten²,

Laenen³

et al. 2014

Phytotaxa

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The 'Pantepui' region of northern South America comprises about 50 topographic islands above a lowland/upland rainforest matrix and constitutes a model of choice for testing island theory hypotheses in a continental setting. Although the Guiana Highlands are considered as the second most important center of endemism in the Neotropics for hepatics, the 10% endemism rates at the species level in liverworts, and probably even less in mosses, pale in comparison of the 42% of endemic angiosperm species. While about 60% of angiosperm endemics are distributed on a single tepui, single-tepui endemics represent only 1/3 of endemic liverworts and only one single-tepui endemic moss species has been described to date. These observations point to a higher dispersal ability of bryophytes as compared to angiosperms and may account for the contrasting rates of endemism between the two groups. In contrast to the vertical displacement hypothesis, which proposes that endemic tepui species originated from niche diversification and local adaptation during vertical migrations in the course of glacial/interglacial cycles, the Amazonian element represents only about 10% of the liverwort flora. By contrast, 1/2-2/3 of the species belong to the montane Neotropical element. The recurrent disjunctions observed between the Andes and the Pantepui region suggest that the bulk of endemic species in the Pantepui area might have originated by dispersal from cold-adapted Andean ancestors.

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Section: Origin and Evolution Of The Unique Biota Of The Pantepui Regmentioning

confidence: 95%

Section: Origin and Evolution Of The Unique Biota Of The Pantepui Regmentioning

confidence: 99%

Biogeography of the Lost World (Pantepui region, northeastern South America): Insights from bryophytes

Désamoré¹,

Vanderpoorten²,

Laenen³

et al. 2014

Phytotaxa

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“…The flora of the tepui summits shows a high degree of specialisation and endemism which has been explained by assuming a long evolutionary process in isolation, due to topographical barriers in the form of huge vertical cliffs that separate these summits from the lowlands (Maguire, 1970;Brewer-Carías, 1980). In contrast, Steyermark and Dunsterville (1980) and Huber (1988) claim the existence of potential migrational pathways that could have promoted the merging and dispersal of high-tepuian floras in lowland regions during the glaciations, when the vegetation was displaced downward owing to cold climates. Similarly, the concept of a Pantepui refuge (Mayr and Phelps, 1967) as a biogeographical entity embracing all the tepui summits above 1500 m, was created to explain the survival of summit floras during glaciations, when climates were purportedly unfavourable for their development in adjacent areas (Steyermark, 1979).…”

Section: Introductionmentioning

confidence: 96%

“…However, palynological and, in general, palaeoecological studies, are still too scarce in the Guayana highlands to adequately substantiate evolutionary, biogeographical and palaeoclimatic hypotheses. This paper presents new palynological reconstructions of Holocene vegetation and palaeoenvironments on top of the Guaiquinima tableau, that Steyermark and Dunsterville (1980) studied, which led them to propose the hypothesis of vertical migration.…”

Section: Introductionmentioning

confidence: 99%

Palaeovegetational and palaeoenvironmental trends in the summit of the Guaiquinima massif (Venezuelan Guayana) during the Holocene

Rull

2005

J Quaternary Science

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The summits of the table mountains (tepuis) from the Neotropical Guayana region are remote environments suitable for palaeoecological studies with evolutionary, biogeographical and palaeoclimatic implications. Here, using palynological analyses of two radiocarbon-dated peat bogs from a tepui summit, the Holocene palaeovegetational trends are reconstructed, and related to possible forcing factors. Because of the pristine character of the Guaiquinima summit, the recorded palaeoenvironmental changes are probably due to natural causes, which makes them valuable archives of the natural component of climatic change at a millennial time scale. The sequence begins with pioneer communities or meadows similar to present-day ones, between about 8.4 and 4.5 ky BP. After this date, and until about 2 kyr BP the expansion of gallery forests suggests an increase in precipitation, documented also at regional (Neotropical) level. Between ca. 2 kyr BP and the last century, gallery forests are replaced by forests characteristic of the upper Guaiquinima altitudes, coinciding with a regional phase of reduced moisture. The present-day meadows, established relatively quickly during the last century, substituted the former upland forests. In the locality studied, the main controlling factor of the vegetation during the Holocene seems to have been the moisture balance. In contrast to other tepui summits, there is no clear evidence for changes linked to temperature oscillations. This could be due to the elevation of the site, far from any characteristic ecological boundary, that makes it insensitive to this parameter.

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“…Early botanical researchers assumed that 90-95% of Pantepui plant species were endemic, and thus adopted Doyle's idea of a long history of evolution in isolation (Maguire 1970;BrewerCarías 1978). Later, it was realised that not all the tepui summits were topographically isolated from the adjacent lowlands, and it was postulated that plants could have been dispersed through them, after vertical shifts during glaciations (Steyermark and Dunsterville 1980;Huber 1988). This idea was further supported by the realisation that the degree of endemism was notably lower (33%) than previously estimated (Berry et al 1995).…”

Section: Introductionmentioning

confidence: 99%

Is the ?Lost World? really lost? Palaeoecological insights into the origin of the peculiar flora of the Guayana Highlands

Rull

2004

Naturwissenschaften

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The peculiar biogeography of the so-called "Lost World", i.e. the summits of sandstone tableaux ( tepuis) in the Neotropical Guyana region of Venezuela, has generated a debate regarding the factors that are thought to account for modern vegetation patterns in the region. Some argue that plant communities on these high-elevation summits reflect a long history of evolution in isolation, while others surmise that there has been substantial biotic interchange with the surrounding lowlands during glacial times. Until now, these apparently competing hypotheses have not been tested using palaeoecological methods. I used pollen analysis of Quaternary sediments and documented past vertical migrations of vegetation in response to climate changes, which supports the second hypothesis. Physiographical analysis, however, shows that about half the tableaux summits are too high for their flora to have reached the lowlands during the last glaciation, suggesting that a portion of the tableaux vegetation has always experienced some degree of biotic isolation. Thus, a component of the summit vegetation evolved in isolation, whereas other taxa experienced interchange, as reflected in endemism patterns among the tableaux summits. Biogeographical patterns on the summits are the result of complex evolutionary processes. The two hypotheses invoked to explain the vegetation patterns are not mutually exclusive, but instead complement one another.

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The Lowland Floral Element on the Summit of Cerro Guaiquinima and Other Cerros of the Guayana Highland of Venezuela

Cited by 37 publications

References 3 publications

Biogeography of the Lost World (Pantepui region, northeastern South America): Insights from bryophytes

Biogeography of the Lost World (Pantepui region, northeastern South America): Insights from bryophytes

Palaeovegetational and palaeoenvironmental trends in the summit of the Guaiquinima massif (Venezuelan Guayana) during the Holocene

Is the ?Lost World? really lost? Palaeoecological insights into the origin of the peculiar flora of the Guayana Highlands

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