The phytogeography of unglaciated Eastern United States and its interpretation

Braun, E. Lucy

doi:10.1007/bf02872433

Cited by 77 publications

(8 citation statements)

References 103 publications

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“…The prevailing evidence from the fossil record (e.g., Graham, 1999Graham, , 2010Ramírez-Arriaga et al, 2014a, 2014b suggests that this disjunction pattern formed after the mid-Miocene, with northern temperate elements (with Paleogene fossil records in ENA) appearing in MAM palynofloras particularly after the mid-Pliocene. This is consistent with the scenarios suggested by Sharp (1953) and Braun (1955) and challenges the idea, held by several others (e.g., Steyermark, 1950;Dressler, 1954), that this disjunction was formed during the early Tertiary. Graham (2010), who has studied this disjunction extensively from a paleobotanical and palynological perspective, generally favors a gradual introduction (from north to south) of the temperate elements after the mid-Miocene and downplays the importance of Pleistocene glaciation in shaping this disjunction given the earlier appearance of genera such as Alnus, Fagus, Liquidambar, and Ulmus in the MAM highlands (Braun [1955] 2015) for similar conceptual models.…”

Section: The Fossil Recordsupporting

confidence: 91%

“…The MAM cloud forests and ENA broadleaf forests are separated by a large arid expanse of grassland and desert ranging across the central and southwestern United States and northern Mexico. Since the landmark paper by Miranda and Sharp (1950), there has been considerable interest in this biogeographic pattern, and many have speculated about the evolutionary and geologic history underlying its formation (e.g., Carlson, 1954;Dressler, 1954;Braun 1950Braun , 1955Martin and Harrell, 1957;Graham, 1973Graham, , 1999Lorenzo et al, 1983;Greller, 1990), but there have been surprisingly few recent empirical studies to explore the evolutionary history of ENA-MAM disjuncts.…”

Section: Introductionmentioning

confidence: 99%

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Evolutionary origins of the eastern North American–Mesoamerican floristic disjunction: Current status and future prospects

Stull

2023

American J of Botany

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Biogeographic disjunction patterns, where multiple taxa are shared between isolated geographic areas, represent excellent systems for investigating the historical assembly of modern biotas and fundamental biological processes such as speciation, diversification, niche evolution, and evolutionary responses to climate change. Studies on plant genera disjunct across the northern hemisphere, particularly between eastern North America (ENA) and eastern Asia (EAS), have yielded tremendous insight on the geologic history and assembly of rich temperate floras. However, one of the most prevalent disjunction patterns involving ENA forests has been largely overlooked: that of taxa disjunct between ENA and cloud forests of Mesoamerica (MAM), with examples including Acer saccharum, Liquidambar styraciflua, Cercis canadensis, Fagus grandifolia, and Epifagus virginiana. Despite the remarkable nature of this disjunction pattern, which has been recognized for over 75 years, there have been few recent efforts to empirically examine its evolutionary and ecological origins. Here I synthesize previous systematic, paleobotanical, phylogenetic, and phylogeographic studies to establish what is known about this disjunction pattern to provide a roadmap for future research. I argue that this disjunction pattern, and the evolution and fossil record of the Mexican flora more broadly, represents a key missing piece in the broader puzzle of northern hemisphere biogeography. I also suggest that the ENA–MAM disjunction represents an excellent system for examining fundamental questions about how traits and life history strategies mediate plant evolutionary responses to climate change and for predicting how broadleaf temperate forests will respond to the ongoing climatic pressures of the Anthropocene.

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Section: The Fossil Recordsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Evolutionary origins of the eastern North American–Mesoamerican floristic disjunction: Current status and future prospects

Stull

2023

American J of Botany

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“…Conifer hotspots could then be thought of like Pleistocene glacial refugia [89][90][91], although they maintain and accumulate regional diversity over longer time periods. Indeed, the southern China conifer hotspot occurs within a region that has long been considered a global refugium for a variety of plant lineages, including notable 'living fossil' conifers like Pseudolarix and Metasequoia [92,93].…”

Section: Discussionmentioning

confidence: 99%

“…Given the association between topographic heterogeneity and species richness among organisms more generally [23,[89][90][91][95][96][97][98][99], the accumulation process that we propose for the formation of conifer hotspots is likely to be widespread among organisms. The degree to which in situ diversification or preservation processes influence biodiversity should depend on the rate at which groups adapt [18]; for example, conifers and other long-lived woody plant groups have low rates of evolution but can show large range shifts over time, and thus may be more likely to form such accumulation hotspots.…”

Section: Discussionmentioning

confidence: 99%

Accumulation over evolutionary time as a major cause of biodiversity hotspots in conifers

et al. 2019

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Biodiversity hotspots are important for understanding how areas of high species richness form, but disentangling the processes that produce them is difficult. We combine geographical ranges, phylogenetic relationships and trait data for 606 conifer species in order to explore the mechanisms underlying richness hotspot formation. We identify eight richness hotspots that overlap known centres of plant endemism and diversity, and find that conifer richness hotspots occur in mountainous areas within broader regions of long-term climate stability. Conifer hotspots are not unique in their species composition, traits or phylogenetic structure; however, a large percentage of their species are not restricted to hotspots and they rarely show either a preponderance of new radiating lineages or old relictual lineages. We suggest that conifer hotspots have primarily formed as a result of lineages accumulating over evolutionary time scales in stable mountainous areas rather than through high origination, preferential retention of relictual lineages or radiation of species with unique traits, although such processes may contribute to nuanced differences among hotspots. Conifers suggest that a simple accumulation of regional diversity can generate high species richness without additional processes and that geography rather than biology may play a primary role in hotspot formation.

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“…Qom, Arak, Kermanshah, Ilam, Shiraz and Hamedan populations came from Kurdo-Zagrosian sub-province, Kerman population from Farso-Kermanian sub-province and Khorasan from Khorasanian sub-province of Irano-Turanian region. Turkey population was from Euxinian district of Euro-Siberian region and USA from Atlantic province (Braun 1955;Zohary 1973).…”

Section: Discussionmentioning

confidence: 99%

Seed morphology and fatty acids composition among Flax populations

et al. 2020

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Flax (Linum usitassimum L.) of family Linaceae is one of the most important crops, which has been widely used from ancient times. The aim of the study was to examine seed morphological characteristics and fatty acids differences among 13 populations of flax (11 from Iran, one from Turkey and one from USA). We studied six morphological variables of seeds in 50 replications. The methyl esters of seeds fatty acids were analyzed using GC. We detected that the flax seeds shape and color were stable among the populations, whereas ANOVA proved significant variations for all the quantitative seed morphological features. Moreover, we found the main fatty acids of the seed oil remained consistent over the ecological and geographical ranges of the populations, except for Khorasan and Turkey populations differed from the rest by their second main fatty acid. We registered that the amounts of main fatty acids differed among the populations and ANOVA test proved significant differences for most of the identified fatty acids. In addition, significant relationships were registered between some fatty acids. The populations were clustered in UPGMA tree and PCO plot into three distinct groups. CA joined plot and PCA biplot demonstrated that each group had specific type and amount of fatty acid. Therefore, we defined three chemotypes: petroselinic acid, linoleic and linolenic acids, and oleic acid. Although, studied ecological factors influenced some fatty acids amounts, populations from different phytogeographical regions clustered closely as chemotypes. This revealed that populations of each chemotype have been originated from the same diversity center, and some secondary diversity centers exist for flax in the world.

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The phytogeography of unglaciated Eastern United States and its interpretation

Cited by 77 publications

References 103 publications

Evolutionary origins of the eastern North American–Mesoamerican floristic disjunction: Current status and future prospects

Evolutionary origins of the eastern North American–Mesoamerican floristic disjunction: Current status and future prospects

Accumulation over evolutionary time as a major cause of biodiversity hotspots in conifers

Seed morphology and fatty acids composition among Flax populations

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