Australian angiosperm ﬂora looks like, for example it is
predominantly composed of bisexual shrubs with dry-dehis-
cent fruits (Fig. 1), and, not unexpectedly, this combination of
characters is signiﬁcantly and negatively associated with a
threatened status (Table 2). The binomial and the multinomial
models reveal that the occurrence of a threatened status in the
Australian ﬂora can be explained by a complex interaction
between habit, sex system and fruit type. Thus it may be
misleading to use a single character state or layer of informa-
tion to infer character association with a threatened status. If
interaction is considered, it appears from the binomial model
(Table 2) that there is a signiﬁcant and positive association of
endangered trees having a monoecious sex system. In contrast,
there is a signiﬁcant occurrence of herbs with dry-indehiscent
fruits not being endangered species. From this we hypothesize
that tree species with monoecious sex systems (rare and
common) are likely to be vulnerable to processes that increase
extinction risk, such as fragmentation. Gross (2005) postulates
that the high predominance of monoecy in Australian
rainforest trees may be related to inefﬁciencies in insect
pollination systems – and from this we suggest that inefﬁcien-
cies in pollination could be causal of extinction risk. Support
for this hypothesis comes from Sakai et al. (2002), who found
for the Hawaiian ﬂora that insect pollination is signiﬁcantly
associated with extinction risk. In contrast, we hypothesize that
herbs with dry-indehiscent fruits are resilient to the processes
of fragmentation. These will be interesting areas to test, for
example in rehabilitation studies.
The inﬂuence of phylogeny on extinction risk
We found that phylogeny and particular life-history characters
are signiﬁcantly correlated with extinction risk. For example,
extinction risk and unisexual ﬂowers are signiﬁcantly correlated
in the Asteraceae, Thymelaeaceae, and in a clade represented by
the Cyperaceae, Eriocaulaceae and Hydatellaceae. Similarly,
certain fruit types are also correlated with a threatened status in
some groups. For example, in the Apocynaceae, Euphorbiaceae,
Myrtaceae and Rutaceae, ﬂeshy fruit and extinction risk are
correlated. Whether the correlation between these characters
and extinction risk is cause or effect remains to be tested. Our
results could, however, be used in conservation planning; for
example, species from the Euphorbiaceae with ﬂeshy fruits on
low-priority threatened species lists could be ﬂagged for
population assessment, a process that otherwise might not
happen for many years if at all, thus enabling species to be caught
in a cost-effective way before they become critically endangered.
The association between speciosity and extinction risk
Studies that determine whether rarity is associated with taxon
speciosity provide the opportunity to test the hypothesis that
rates of rarity are independent of taxonomic group-size (e.g.
Edwards & Westoby, 2000; Schwartz & Simberloff, 2001).
Results from studies between speciosity, extinction risk and
taxon size (e.g. Edwards & Westoby, 2000) should, however, be
viewed with caution if artiﬁcial phylogenies (e.g. Cronquist,
1988 classiﬁcation system) were used in the study. Our results
concur with those of Schwartz & Simberloff (2001); that is,
genera and families with few species consistently contain fewer
than the expected number of threatened species. We did detect
a signiﬁcant positive relationship between extinction risk and
the size of genera for endangered species and the size of
families for extinct species, but bootstrapping supports our
hypothesis that these relationships are an artifact of the fact
that most genera and families in Australia are small. Thus, as
pointed out by Schwartz & Simberloff (2001), plant conser-
vation is facilitated by the fact that there are relatively few
species-poor lineages that contain rare species.
C O N C L U S I O N
At the continental scale, the Australian ﬂora mostly comprises
bisexual shrubs with dry-dehiscent fruits, and this combina-
tion of characters is signiﬁcantly and negatively associated with
rarity. Moreover, herbs with dry-indehiscent fruits are unlikely
to be endangered species. This combination of characters could
be taken into consideration for the selection of species with
robust life-history strategies where resilience is greatly needed,
for example in the restoration of degraded habitats. The tree
life form is signiﬁcantly absent from the contemporary list of
extinct species in Australia. This may reﬂect a degree of
resilience in the tree life form, as well as too short an
observation period. In particular, there are many trees on the
current endangered list, indicating that extinction is a real
threat for such species. However, the longevity of many tree
species provides a window of opportunity to mitigate some
threats. Our analyses showed that monoecious trees in
particular may be a life form vulnerable to extinction
processes. Our approach has been a broad one, so that
most ﬂowering species in Australia could be assessed for
key life-history strategies. This approach could also be used
as a model for other ﬂoras for which a continent-speciﬁc
proﬁle of the life-history characters would expedite conserva-
A C K N O W L E D G E M E N T S
The following people kindly answered our botanical queries:
L. Adams, K. Atkins, B. Bennett, E. Brown, J.J. Bruhl,
D. Coates, B. Conn, R. Chinnock, D. Dixon, R. Elick, J.
Everett, A.S. George, B. Gray, S.G. Hegde, B.P.M. Hyland, B. R.
Jackes, J. Jeanes, L. Jessup, R.W. Johnson, G. Keighery, A.
Lowrie, D. Mackay, N. Marchant L. Meredith, A. Orchard, P.
A. Sjo¨stro¨m and C. L. Gross
Journal of Biogeography 33, 271–290
the Latin. The directors from the following herbaria are
thanked for allowing us access to their specimens and/or data
bases: AD, BRI, NE, NSW, QRS, PERTH. Several colleagues
reviewed an earlier version of this manuscript. R. Goldingay, S.
McIntyre, D. Morrison, A. Robertson. D.A. Mackay, R.
Murison and J. Reid are thanked for comments on statistics.
D.A. Mackay, D.A. Keith and B.R. Murray are thanked for
valuable suggestions. D. Bowman and B.W. Brooks are
thanked for comments that improved the manuscript. The
study was funded by the University of New England.
R E F E R E N C E S
Akaike, H. (1974) A new look at statistical model identiﬁcation.
IEEE Transactions on Automatic Control, Au-19, 716–722.
Akcakaya, H.R., Ferson, S., Burgman, M.A., Keith, D.A., Mace,
G.M. & Todd, C.R. (2000) Making consistent IUCN classi-
ﬁcations under uncertainty. Conservation Biology, 14, 1001–
plants, 1995 rev. edn. Centre for Plant Biodiversity Research;
Australian Nature Conservation Agency, Canberra, Australia.
Burgman, M.A. (2002) Are listed threatened plant species
actually at risk? Australian Journal of Botany, 50, 1–13.
Carlquist, S. (1966) The biota of long distance dispersal. IV.
Genetic systems in the ﬂoras of oceanic islands. Evolution,
Chazdon, R.L., Careaga, S., Webb, C. & Vargas, O. (2003)
Community and phylogenetic structure of reproductive
traits of woody species in wet tropical forests. Ecological
Monographs, 73, 331–348.
Conn, J.S., Wentworth, T.R. & Blum, U. (1980) Patterns of
dioecism in the ﬂora of the Carolinas. The American Mid-
land Naturalist, 103, 310–315.
Crawley, M.S. (2003) Statistical computing. An introduction to
data analysis using S-Plus. Wiley, Chichester, UK.
Cronquist, A. (1988) The evolution and classiﬁcation of
ﬂowering plants, 2nd edn. New York Botanical Garden
Publication, Bronx, NY.
Davies, T.J., Barraclough, T.G., Chase, M.W., Soltis, P.S.,
Soltis, D.E. & Savolainen, V. (2004) Darwin’s abominable
mystery: insights from a supertree of the angiosperms.
Proceedings of the National Academy of Sciences of the United
States of America, 101, 1904–1909.
Edwards, W. & Westoby, M. (2000) Families with highest
proportions of rare species are not consistent between ﬂoras.
Journal of Biogeography, 27, 733–740.
Flores, S. & Schemske, D. (1984) Dioecy and monoecy in the
ﬂora of Puerto Rica and the virgin islands. Biotropica, 16,
Fox, J.F. (1985) Incidence of dioecy in relation to growth form,
pollination and dispersal. Oecologia, 67, 244–249.
Garcia, M.B. (2003) Demographic viability of a relict popu-
lation of the critically endangered plant Borderea chouardii.
Conservation Biology, 17, 1672–1680.
Godley, E. (1979) Flower biology in New Zealand. New Zea-
land Journal of Botany, 17, 441–466.
Golding, J.S. & Hurter, P.J.H. (2003) A Red List account
of Africa’s cycads and implications of considering life-
history and threats. Biodiversity and Conservation, 12, 507–
trees from the Australian tropics with other tropical biomes
– more monoecy but why? American Journal of Botany,
Hegde, S.G. & Ellstrand, N.C. (1999) Life history differences
between rare and common ﬂowering plant species of Cali-
fornia and the British Isles. International Journal of Plant
Sciences, 160, 1083–1091.
Hnatiuk, R.J. (ed.) (1990) Census of Australian vascular plants.
Australian Govt. Pub. Service, Canberra.
Ihaka, R. & Gentleman, R. (1996) R: A language for data
analysis and graphics. Journal of Computational and Gra-
phical Statistics, 5, 299–314.
Kay, Q.O.N. & Stevens, D.P. (1986) The frequency, distribu-
tion and reproductive biology of dioecious species in the
native ﬂora of Britain and Ireland. Botanical Journal of the
Linnean Society, 92, 39–64.
Kaye, T., Meinke, R.J., Kagan, J., Virlakas, S., Chambers, K.,
Zika, P.F. & Nelson, J. (1997) Patterns of rarity in the
Oregon ﬂora: implications for conservation and manage-
ment. Conservation and management of native plants and
fungi (ed. by T.N. Kaye, A. Liston, R.M. Love, D. Luoma,
R.J. Meinke and M.V. Wilson), pp. 1–10. Native Plant
Society of Oregon, Corvallis, OR.
Keith, D.A. & Burgman, M.A. (2004) The Lazarus effect: can the
dynamics of extinct species lists tell us anything about the
status of biodiversity? Biological Conservation, 117, 41–48.
Khedr, A.H., Cadotte, M.W., El Keblawy, A. & Lovett-Doust, J.
(2002) Phylogenetic diversity and ecological features in
the Egyptian ﬂora. Biodiversity and Conservation, 11, 1809–
Laurance, W.F., Lovejoy, T.E., Vasconcelos, H.L., Bruna, E.M.,
Laurance, S.G. & Sampaio, E. (2002) Ecosystem decay of
Amazonian forest fragments: a 22-year investigation. Con-
servation Biology, 16, 605–618.
Maddison, D.R. & Maddison, W.P. (2001) MacClade 4.03.
Sinauer Associates, Inc., Sunderland, MA.
McComb, J.A. (1966) The sex forms of species in the ﬂora of
south-west Western Australia. Australian Journal of Botany,
Morley, B.D. & Toelken, H.R. (eds) (1983) Flowering plants in
Australia. Rigby Publishers, Adelaide.
Murray, B.R. & Lepschi B.J. (2004) Are locally rare species
abundant elsewhere in their geographical range? Austral
Ecology, 29, 287–293.
Murray, B.R., Thrall, P.H., Gill, A.M. & Nicotra, A.B. (2002a)
How plant life-history and ecological traits relate to species
rarity and commonness at varying spatial scales. Austral
Ecology, 27, 291–310.
Life-history characters in the Australian ﬂora
ª 2006 The Authors. Journal compilation ª 2006 Blackwell Publishing Ltd
species rarity to life history in plants of eastern Australia.
Evolutionary Ecology Research, 4, 937–950.
Parsons, P.A. (1958) Evolution of sex in the ﬂowering plants of
South Australia. Nature, 181, 1673–1674.
Possingham, H.P., Andelman, S.J., Burgman, M.A., Medellin,
R.A., Master, L.L. & Keith, D.A. (2002) Limits to the use of
threatened species lists. Trends in Ecology and Evolution, 17,
Rabinowitz, D. (1981) Seven forms of rarity. The biological
aspects of rare plant conservation (ed. by H. Synge), pp. 205–
217. Wiley, New York.
Renner, S.S. & Ricklefs, RE. (1995) Dioecy and its correlates in
the ﬂowering plants. American Journal of Botany, 82, 596–
Rey Benayas, J.M., Scheiner, S.M., Sanchez-Colomer, M.G. &
application of a new model to Mediterranean montane
grasslands. Conservation Ecology, 3, 5. http://www.consecol.
Robinson, G.R., Yurlina, M.E. & Handel, S.N. (1994) A cen-
tury of change in the Staten Island ﬂora: ecological correlates
of species losses and invasions. Bulletin of the Torrey Bota-
nical Club, 121, 119–129.
Rogers, G. & Walker, S. (2002) Taxonomic and ecological
proﬁles of rarity in the New Zealand vascular ﬂora. New
Zealand Journal of Botany, 40, 73–93.
Roy, R.P. (1974) Sex mechanism in higher plants. The Journal
of the Indian Botanical Society, 53, 141–155.
Sakai, A.K., Wagner, W.L., Ferguson, D.M. & Herbst, D.
(1995) Biogeographical and ecological correlates of dioecy in
the Hawaiian ﬂora. Ecology, 76, 2530–2543.
Sakai, A.K., Wagner, W.L. & Mehrhoff, L.A. (2002) Patterns of
endangerment in the Hawaiian ﬂora. Systematic Biology, 51,
Schwartz, M.W. & Simberloff, D. (2001) Taxon size predicts
rates of rarity in vascular plants. Ecology Letters, 4, 464–469.
Scott, B. & Gross, C.L. (2004) Recovery directions for mono-
ecious and endangered Bertya ingramii using autecology and
(Euphorbiaceae). Biodiversity and Conservation, 13, 885–899.
Steiner, K.E. (1988) Dioecism and its correlates in the cape ﬂora
of South Africa. American Journal of Botany, 75, 1742–1754.
Stevens, P.F. (2001) Angiosperm phylogeny website. Version 5,
May 2004 (and updated more or less continuously since).
Turner, I.M., Chua, K.S., Ong, Y.S.Y., Soong, B.D. & Tan,
H.T.W. (1996) A century of plant species loss from an
isolated fragment of lowland tropical rain forest. Conserva-
tion Biology, 10, 1229–1244.
Vamosi, J.C. & Vamosi, S.M. (2005) Present day risk of ex-
tinction may exacerbate the lower species richness of dioe-
cious clades. Diversity and Distributions, 11, 25–32.
Venables, W.N. & Ripley, B.D. (2002) Modern applied statistics
with S, 4th edn. Springer, New York.
Walter, K.S. & Gillett, H.J. (eds) (1998) 1997 IUCN Red list of
threatened plants, compiled by the World Conservation
Monitoring Centre. IUCN – The World Conservation Union,
Gland, Switzerland and Cambridge, UK.
Webb, C.O. & Donoghue, M.J. (2002) Phylomatic: a database
for applied phylogenetics. http://www.phylodiversity.net/
Yampolsky, C. & Yampolsky, H. (1922) Distribution of sex
forms in the Phanerogamic ﬂora. Bibliotheca Genetica, 3, 1–63.
B I O S K E T C H E S
Anne Sjo¨stro¨m is interested in the life histories of threatened
Australian ﬂora and the detection of patterns that can be
applied to conservation management.
Caroline Gross studies the distribution of life-history
characters in relation to phylogeny. She has broad interests
in the ecology of pioneer species and plant species in decline,
particularly their reproductive ecologies. The evolutionary
ecology of plant sexual systems, particularly in tropical
ecosystems is a current research focus.
Editor: David Bowman