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species, and therefore the circumpolar distribution of Dryas
species such as D. octopetala sensu lato (Hult6n 1971) is par-
ticularly significant.
All of the above-mentioned data supports the idea that fleshy
fungi are governed by many of the same physioecological and
historical factors that control vascular plant ranges just as Cul-
berson (1972) suggested for lichens. This is difficult to recon-
cile with the ease with which fungal spores are disseminated.
Fungal spores are minute compared to the seeds of vascular
plants, and can be transported vast distances by winds or storm
systems. However, the current evidence suggests that most
macrofungi are not transported across oceans or large conti-
nental areas without first colonizing the intermediate ground.
For example, while large numbers of fungal spores, including
basidiospores and even moss protonema were recovered in air
over the Atlantic Ocean by Pady and Kapica (1955), most
spores were no longer viable. And although Pady and Kapica
concluded that some viable fungal spores could make the trans-
atlantic crossing, additional evidence indicates that this is not
the case for most macrofungi. One of the problems facing all
spores transported long distance is contacting a suitable target.
Target size and abundance of targets becomes crucial to sur-
vival. For species colonizing specific wild plants or plant
parts, the targets are very small compared to those inhabiting
soil, grasslands, or at least plant species in large scale mono-
culture. Examples of long distance dispersal are difficult to
find.. One case involves Puccinia graminis Pers. f. sp. tritici,
which may have been introduced in eastern Australia from
South Africa by wind (Watson and de Sousa 1983). Even then
some doubt exists as Wellings et al. (1987) note that at least in
the case of Puccinia striiformis Westend. f.sp. tritici, other
means of introduction, such as transport on clothing, are more
probable. Wind obviously plays an important role in the dis-
semination of fungi when the target sizes are sufficiently large
and not thousands of kilometers distant. The spread of coffee
rust, Hemileia vastatrix Berk. & Br., by wind in Central and
South America following prevailing winds is well documented
(Schieber and Zentmeyer 1984). However, no evidence has
been found to support the idea of transoceanic dispersal by
wind.
A second problem facing most basidiomycetes is the estab-
lishment of a dikaryon to complete their life cycle. Given that a
viable spore can make an oceanic or continental crossing and
does fall on a suitable substrate, the odds against there being a
compatible colony nearby must be astronomical. Even where
compatible species occur on opposite sides of a barrier, thus
vastly increasing this probability, there is little evidence of
gene flow. Vilgalys and Johnson (1987) noted considerable
genetic divergence between geographically isolated popula-
tions of single mating groups in the Collybia dryophila
(Bull.:Fr.) Kummer group in Europe and eastern North
America. Similarly, Macrae (1942) showed that luminosity in
Panellus stypticus (Bull.:Fr.) Karst. only occurs in eastern
North American strains and is absent in European strains. Fur-
thermore, she showed that luminosity was caused by a single
Mendelian factor and was the dominant form, expressed in the
F, generation. The absence of the luminous form in Europe
indicates that eastern North American spores are failing either
to make the crossing or to establish themselves. At least in
coastal British Columbia, the nonluminescent form of P. styp-
ticus is established. Fresh, sporulating collections seen by me
on Vancouver Island, and their mycelium in culture are non-
luminescent. The absence of various other species from other-
CAN. I. BOT. VOL. 67, 1989
wise suitable habitats in eastern North America when they
occur in western North America, also indicates that there is
little if any long distance transport of viable inoculum.
Phaeolepiota aurea, which is widespread in Europe and Asia,
is only known from the west in North America. Strobilurus
occidentalis has its most distinctive form along the Pacific
coast on cones of Picea sitchensis, and a less distinctive form
in the western cordillera on Picea engelmanii, also occurs east
of the continental divide in Alberta on cones of Picea glauca,
but has never been picked up further east following that host.
In eastern North America, Rhodotus palmatus apparently has
not yet extensively colonized the eastern side of the Appalachians
where suitable substrates occur. Maryland is the-only
location where it is known to have reached the Atlantic coast.
All three examples, P. aurea, S. occidentalis, and R. palmatus,
may represent species still in the slow process of mkration
and colonization. Watling (1978, 1987) also noted that
two conspicuous species, Amanita caesarea (Scop. : Fr.) Grev.
and Albatrellus ovinus (Fr.) Kotl. & Pouz., were absent in the
British Isles in spite of the presence of suitable habitats and
hosts and in spite of the presence of these fungi in adjacent
Europe.
In concurrence with Bisby et al. (1929), in general it has
been established that macrofungi have wider global ranges
than vascular plants. However, the ranges are not so broad as
to be biogeographically meaningless. On the contrary, fungi
offer yet another dimension to the study of biogeography.
Whereas many of the transoceanic disjunct patterns exhibited
by vascular plants are exhibited at the generic or family level
(Axelrod 1970; Raven and Axelrod 1974), they are exhibited
at the species level by many higher fungi just as they are for the
lichenized ascomycetes and bryophytes (Culberson 1972;
Schofield and Crum 1972). Horak (1983~) listed 75 species
common to southern South America and Australia or New
Zealand, many of which must be remnants of populations fragmented
by the breakup of Gondwanaland approximately 100
million years ago. Similarly, Imai (1961), Hongo (1978),
Hongo and Yokoyama (1978), Mao et al. (1986), and Zang
(1986) have noted several species disjunct between eastern
Asia and eastern North ~merica. It is known that saprophytic
~asidiomycet'es existed approximately 300 million years BP in
the Middle Pennsylvania (Dennis 1970), and that woody perennial
polypores associated with conifers were extant in the
Upper Mesojurassic approximately 150 million years ago
(Singer and Archangelsky . 1958). Therefore it would not be
~
surp&sing if agarics and other higher fungi populated Gondwanaland.
To have their present distributions, some of the
fungal species listed by Horak must be at least 100 million
years old. Cyptotrama asprata, Tetrapyrgos nigripes, and
Xeromphalina tenuipes, represented in Canada and with pantropical
distributions including Australia and South America,
are possibly northern examples of this ancient Gondwanaland
mycoflora. Heliocybe sulcata with its peculiar South Africa,
Mediterranean, continental North American range (cf. Axelrod
1970) may be another species originating in Gondwanaland.
Some species must be at least 25 -30 million years old if correlated
with the connection of mesic forests between southeast
Asia and eastern North America (Wolfe and Leopold 1967).
These species include Crinipellis setipes, C. campanella, Lactarius
indigo, and others listed by Imai and Hongo, e.g.,
Marasmius siccus (Schw.) Fr., Lactarius gerardii Peck, T.10pilus
chromapes (Frost) Smith & Thiers, T. ballouii (Peck)
Singer, Boletellus russellii (Frost) Gilbert, Catathelas~na ven-