The Wallace Line Alfred Wallace, one of the premier zoobiogeographers, wrote the definitive treatise “Distributions of Animals” in 1876 where he summarized the known distributions and causes of their biogeographical patterns
The Wallace Line Alfred Wallace’s main interest was in the vertebrate fauna of the Indo-Malay Archipelago from Asia to Australia where he clearly saw a sharp faunistic break
Probably his most important trip he ever made was a 6 km ferry ride from Bali to Lombok
Wallace’s trips
Sclater’s & Wallace’s faunistic regions
The Wallace Line
The Wallace Line
“In the archipelago . . . there are two distinct faunas rigidly circumscribed, which differ as much as those of South America and Africa, and more than those of Europe and North America” [ Letter to Henry Bates in London (1858)]
“In the archipelago . . . there are two distinct faunas rigidly circumscribed, which differ as much as those of South America and Africa, and more than those of Europe and North America” [ Letter to Henry Bates in London (1858)] “The boundary line often passes between islands closer than others in the same group. I believe the western part to be a separated portion of continental Asia, the eastern the fragmentary prolongation of a former Pacific continent”
Wallace’s trips
Sclater’s & Wallace’s faunistic regions
Looking east from Bali across 6 km Lombok Straits
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The Wallace Line
The Wallace Line
Wallace graphically depicts what has since been termed the “Wallace Line” in his book by showing birds and mammals that are found in the Oriental (Borneo, left) and Australian (New Guinea, right) sides tarsier
tree kangaroo lory
• Wallace Line — the imaginary line separating the Oriental and Australian biotas — extends between Bali and Lombok and between Borneo/Philippines and Sulawesi • Several other lines have been proposed in the region based on particular groups of animals or plants.
tree shrew
tapir raquet-tailed kingfisher
Oriental Fauna
• Main issue with most lines is what do with Sulawesi (Celebes)
Australian Fauna
Cover plate from Distributions of Animals
The Wallace Line Sulawesi, with its mixture of Oriental and Australian fauna, was so perplexing to Wallace, that he vacillated back and forth on where to place the island
The Wallace Line Now know that the two regions are different continental plates that have been moving independently — the Asian and Australian plates
Crested black macaque
The IndoMalay - New Guinea Archipelago area includes island groups mostly confined to either of two continental shelves: Sunda shelf — Asian Bear cuscus (marsupial)
Sahul shelf — Australian
Backbone of Sulawesi
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Eastern North America - Eastern Asia
Eastern North America - Eastern Asia This disjunct pattern, also seen in animals, was one of the original repeated patterns that led Rosen, Nelson, and Platnick to formulate cladistic biogeography
Stewartia malacodendron Theaceae - tea family
Eastern North America and Eastern Asia is the “classic” north temperate disjunction pattern They interpreted such a repeated pattern as due to vicariance (erection of barrier in once continual biota) Stewartia sinensis
Stewartia pseudocamellia
Eastern North America - Eastern Asia Floristic connection between the two areas is strong at the generic level Impression of a biological connection has been strengthened by similarities in climate and ecology or ecological biogeography
Eastern North America - Eastern Asia First disjunction recognized by botanical biogeographers and thus played an important role in Darwin’s evidence for evolution Pattern also involves fossil taxa from the Tertiary (back to about 40 mya), and thus has been termed the Arcto-Tertiary Flora
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Eastern North America - Eastern Asia Credit for the recognition of the floristic similarities often given to Asa Gray (Harvard University), but the first published reference was in a thesis by Linnaeus’ student Jona Halenius (1750) Pattern first noticed by a Jesuit priest, Father Joseph Lafitau, who found American ginseng (1716) near Montreal after reading description of the Chinese ginseng
Eastern North America - Eastern Asia Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst) 1. Pattern originally thought to include “identical species” (Gray listed 134) but now believed to be largely congeneric not conspecific. By 1992 the list included only 8 conspecific examples, and by 1999 only 1.
Caulophyllum thalictroides Blue cohosh - Berberidaceae Caulophyllum robustum
Eastern North America - Eastern Asia
Eastern North America - Eastern Asia
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
1. Pattern originally thought to include “identical species” (Gray listed 134) but now believed to be largely congeneric not conspecific. By 1992 the list included only 8 conspecific examples, and by 1999 only 1.
1. Pattern originally thought to include “identical species” (Gray listed 134) but now believed to be largely congeneric not conspecific. By 1992 the list included only 8 conspecific examples, and by 1999 only 1.
Symplocarpus renifolius Mitchella undulata
Mitchella repens Partridge-berry, Rubiaceae
Symplocarpus foetidus Skunk cabbage, Araceae
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Eastern North America - Eastern Asia
Eastern North America - Eastern Asia
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
1. Pattern originally thought to include “identical species” (Gray listed 134) but now believed to be largely congeneric not conspecific. By 1992 the list included only 8 conspecific examples, and by 1999 only 1.
2. Up to 120 genera of plants have been cited as exhibiting this pattern. If remove genera (like blue beech) with western North American or western European distributions as well, then 65 genera in 42 different families involved
Phryma leptostachya var. asiatica Phryma leptostachya var. leptostachya Lopseed, Verbenaceae
Eastern North America - Eastern Asia
Carpinus betulus Europe
Carpinus caroliniana American hornbeam, blue beech Betulaceae
Eastern North America - Eastern Asia
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
2. . . . and included in the 65 genera are trees
2. . . . and included in the 65 genera are trees
Hamamelis mollis Liriodendron chinense
1 sp. E. Asia
Hamamelis virginiana Witch hazel, Hamamelidaceae
Liriodendron tulipfera Tulip tree, Magnoliaceae
vs.
1 sp. E. North America
2 spp. E. Asia
vs.
2 spp. E. North America
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Eastern North America - Eastern Asia
Eastern North America - Eastern Asia
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
2. . . . and included in the 65 genera are vines
2. . . . and included in the 65 genera are vines
Parthenocissus quinquefolia Virgnia creeper, woodbine, Vitaceae
Parthenocissus heneryana
9 spp. E. Asia
vs.
3 spp. E. North America
Eastern North America - Eastern Asia
Campsis sp.
1 sp. E. Asia
Campsis radicans Trumpet creeper, Bignoniaceae
vs.
1 sp. E. North America
Eastern North America - Eastern Asia
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
2. . . . and included in the 65 genera are herbs
2. . . . and included in the 65 genera are herbs
Jeffersonia dubia Jeffersonia diphylla Twinleaf, Berberidaceae
1 sp. E. Asia
vs.
1 sp. E. North America
Podophyllum peltatum Mayapple, Berberidaceae
Podophyllum hexandra
1 sp. E. Asia
vs.
1 sp. E. North America
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Eastern North America - Eastern Asia
Eastern North America - Eastern Asia
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
2. . . . and included in the 65 genera are herbs
3. In few cases, the disjunction involves different but closely related genera
Nelumbo nucifera
1 sp. E. Asia
Nelumbo lutea Lotus lily, Nelumbonaceae
vs.
1 sp. E. North America
Eastern North America - Eastern Asia
Eomecon chionantha
Sanguinaria canadensis Bloodroot, Papaveraceae
Eastern North America - Eastern Asia
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
3. In few cases, the disjunction involves different but closely related genera
4. The disjunction typically involves E. North America and E. Asia . . .
Weigela florida Diervilla splendens Bush honeysuckle, Caprifoliaceae
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Eastern North America - Eastern Asia
Eastern North America - Eastern Asia
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
Four quick points (reviewed in Jun Wen’s 1999 paper in Ann Rev Ecol Syst)
4. . . . but can involve western North America . . .
4. . . . and central Asia/Europe
Clintonia, bead lily
Eastern North America - Eastern Asia Fossil evidence indicates widespread Arcto-Tertiary Flora existed with subsequent extinction in many portions of this range:
Ginkgo, now confined to east-central China, had a wide Holarctic distribution from the Paleocene into the Neogene as indicated by fossil localities ()
The European plane tree is a hybrid between the eastern North American and central Asian sycamores - Platanus x hybrida - and is more tolerant to urbanization
Eastern North America - Eastern Asia Fossil evidence indicates widespread Arcto-Tertiary Flora existed with subsequent extinction in many portions of this range:
Pseudotsuga (Douglas fir) is widespread today in western North America but has only relictual stands (+) in eastern Asia. Fossil localities () indicate its wider distribution in the past.
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Eastern North America - Eastern Asia Fossil evidence indicates widespread Arcto-Tertiary Flora existed with subsequent extinction in many portions of this range:
Eastern North America - Eastern Asia Summary: Tertiary, as well as present day distributions, indicate that a widespread Arcto-Tertiary or Holarctic Flora existed, especially during 25-3 mya, throughout the entire North Temperate region, and facilitated by Bering and North Atlantic land bridges. Why not present today? 1. Climate deterioration during end of Tertiary and into the Pleistocene
Ginkgo - Tertiary
Sequoia, now confined to coastal California and adjacent Oregon, had a Holarctic Tertiary distribution as indicated by some of its fossil sites ().
Eastern North America - Eastern Asia Summary: Tertiary, as well as present day distributions, indicate that a widespread Arcto-Tertiary or Holarctic Flora existed, especially during 25-3 mya, throughout the entire North Temperate region, and facilitated by Bering and North Atlantic land bridges. Why not present today?
3. Glaciation effects most severe in western Europe where E-W mountain chains prevented forest flora going south to refugias — extinction of forest species
2. Mountain building in w. North America, grassland formation, and extinction of forest species
Stewartia - today
Eastern North America - Eastern Asia New Twists - Molecular Systematics Phylogenetic analyses of 11 putative pairs of vicariad species - are they sister species? Aralia — NO
General interpretation is that the Arcto-Tertiary Flora (and Fauna) was a widespread biota that got fragmented by various events — vicariance
Aralia spinosa Devil’s walking stick, Araliaceae
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Eastern North America - Eastern Asia
Eastern North America - Eastern Asia
New Twists - Molecular Systematics
New Twists - Molecular Systematics
Phylogenetic analyses of 11 putative pairs of vicariad species - are they sister species?
Phylogenetic analyses of 11 putative pairs of vicariad species - are they sister species?
Hamamelis — NO
Gledistsia — NO
Hamamelis Witch hazel, Hamamelidaceae
Eastern North America - Eastern Asia
Gleditsia Honey locust, Fabaceae
Eastern North America - Eastern Asia
New Twists - Molecular Systematics
New Twists - Molecular Systematics
Phylogenetic analyses of 11 putative pairs of vicariad species - are they sister species?
Phylogenetic analyses of 11 putative pairs of vicariad species - are they sister species? Nyssa — +/-
Panax — NO
Panax quinquefolius American ginseng, Araliaceae
Nyssa sylvatica - sour gum, black gum,black tupelo
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Eastern North America - Eastern Asia
Eastern North America - Eastern Asia
New Twists - Molecular Systematics
New Twists - Molecular Systematics
Phylogenetic analyses of 11 putative pairs of vicariad species - are they sister species?
Molecular clocks - when did the species diverge and at same time?
Symplocarpus — YES
1. Liriodendron - tulip trees 13 mya
2. Magnolia - magnolias 2 mya
3. Campsis - trumpet creepers Symplocarpus foetidus, skunk cabbage
25 mya
Symplocarpus renifolius
Eastern North America - Eastern Asia New Twists - Molecular Systematics
Eastern North America - Eastern Asia New Twists - Molecular Systematics
from reading! plants
animals
% of examples showing various disjunct patterns
Recent analysis of 100 examples of disjunctions (33 with absolute time divergences) among these four areas provides some new insights on the Holarctic Flora
1. Plants show considerably higher proportion of Eastern Asia - Eastern North America disjunct pattern than do animals
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Eastern North America - Eastern Asia New Twists - Molecular Systematics
plants
Eastern North America - Eastern Asia New Twists - Molecular Systematics
animals 3. Eastern Asia is source of 20 of the disjuncts, and Eastern North America only 1. These dispersal events occurred over the last 30 my and with Beringia the likely route.
% of examples showing various disjunct patterns 1. Plants show considerably higher proportion of Eastern Asia - Eastern North America disjunct pattern than do animals 2. Plants show considerably lower proportion of Western North America Eastern North America disjunct pattern than do animals
Arrows indicate inferred directions of dispersal
Eastern North America - Eastern Asia Summary: Tertiary, as well as present day distributions, indicate that a widespread Arcto-Tertiary or Holarctic Flora existed, especially during 25-3 mya, throughout the entire North Temperate region, and facilitated by Bering and North Atlantic land bridges. Is vicariance a mechanism for the repeated pattern? • Vicariad species recognized on morphological similarity are not necessarily sister species using phylogenetics. • The large range in estimated time splits for vicariad species indicates that vicariance alone is not an adequate explanation. • Dispersal and speciation did not all occur at the same time in all groups.
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