Download Evidence and hypothesis in biogeography

Journal of Biogeography (J. Biogeogr.) (2013) 40, 813–820
GUEST
EDITORIAL
1
Department of Vertebrate Zoology, National
Museum of Natural History, Smithsonian
Institution, Washington, D.C. 20013-7012,
USA, 2School of Biological, Earth and
Environmental Sciences, University of
New South Wales, NSW 2052, Australia
*Correspondence: Lynne R. Parenti,
Department of Vertebrate Zoology, National
Museum of Natural History, Smithsonian
Institution, PO Box 37012 MRC 159,
Washington, D.C. 20013-7012, USA.
E-mail: [email protected]
Evidence and hypothesis in biogeography
Lynne R. Parenti1* and Malte C. Ebach2
ABSTRACT
Evidence can provide support for or against a particular biogeographical hypothesis. Treating a hypothesis as if it were evidence or an empirical observation confounds many biogeographical analyses. We focus on two recent publications that
address, in part, the evolution of the biota of Sulawesi, the large Indonesian
island in the centre of the Indo-Australian Archipelago. Many biogeographical
explanations are hampered by invoking simple notions of mechanism or process
– dispersal and vicariance – or constraints, such as dispersal from a centre of origin, and, in so doing, dismiss more complex geological phenomena such as
emergent volcanoes within island chains or composite areas as irrelevant. Moreover, they do not search for, therefore never discover, biogeographical patterns
that may better explain the distribution of biota through time.
Keywords
Biogeographical regions, co-evolution, dispersal, historical biogeography,
Indo-Pacific, molecular clock, Sulawesi, vicariance, volcanoes.
INTRODUCTION
Historical biogeographers are like journalists. We report on
the Who, What, Where, When and Why or How of biotic distributions. The Who (biota, such as bony fishes), What (particular clades, such as genera of freshwater eels) and Where
(description of the distribution of each clade, in words and in
maps, over time) of biotic distributions are descriptive and in
practice range from the simple to the complex, from the local
to the global. The When may be part empirical (during what
time periods did/does the clade live) and part hypothesis
[a clade is hypothesized to have split from its sister clade 45
million years ago (Ma) as inferred from a relaxed molecular
clock hypothesis, the minimum age of a fossil, conformance to
a geological event, or conformance to a biogeographical pattern]. The Why or How is solely a hypothesis (e.g. eggplants
arose in Africa and dispersed to Asia; Weese & Bohs, 2010).
Conflating these concepts – treating a hypothesis as if it were
evidence or an empirical observation – introduces bias into a
biogeographical analysis. The bias may come in many forms,
such as favouring one explanation over another simply
because no other explanation was ever considered.
ALTERNATIVE EXPLANATIONS
The philosophical divide in historical biogeography between
those who advocate that Earth and life evolve together and
ª 2013 Blackwell Publishing Ltd
those who advocate centre of origin/chance dispersal explanations was enunciated by Croizat et al. (1974). In modern
historical biogeographical studies the divide is between those
who discover patterns versus those who generate explanations (Ebach & Humphries, 2002). As an example of the latter, the freshwater eels, family Anguillidae, were inferred to
have a deep-sea origin by Inoue et al. (2010) who optimized
habitats on a molecular phylogeny of anguilliform fishes: the
freshwater anguillids were nested in the cladogram among a
series of taxa that live in the deep sea. Freshwater eels and
their close relatives live in three habitats, shallow water
(SW), oceanic midwater (OM) and freshwater (FW), related
as follows (summarized from Inoue et al., 2010; figure 2,
node A): (SW(OM(OM, FW))). Optimization of habitats on
the cladogram is presented by Inoue et al. (2010, p. 363) as
the evidence for the origin of freshwater eels in the deep-sea:
‘…reconstruction of the growth habitats on the resulting tree
unequivocally indicates an origination of the freshwater eels
from the midwater of the deep ocean’ [italics added].
Optimization of habitats on nodes to infer an ancestral
habitat is an extension of the common practice of optimizing
areas on nodes to infer an ancestral area or centre of origin
(e.g. Bremer, 1992; Pirie et al., 2012). Optimization to infer
ancestral habitat is problematic because a deep-sea ancestor
(OM) of anguillids is not ‘unequivocal’. The ancestral population could have lived in both freshwater and the deep sea,
or in neither: it could have lived in shallow water, epicontihttp://wileyonlinelibrary.com/journal/jbi
doi:10.1111/jbi.12069
813
L. R. Parenti and M. C. Ebach
nental seas. Repetition or geographical paralogy of the OM
habitat is given as the evidence that the shift in habitat was
from deep-sea (OM) to freshwater (FW), but it means only
that the deep-sea taxa are more common or widespread
(Ebach, 1999).
Other biogeographical ideas are so well-worn that they
have in practice crossed the line from supporting a hypothesis to appearing to present evidence. We address two such
proposals here with respect to the biota of the Indo-Pacific,
in particular the Indonesian islands of Sulawesi:
1. Volcanoes (and other oceanic islands) must have been
colonized via dispersal.
2. Estimates of divergence time trump biogeographical
patterns.
(a)
widespread
biota
sea
(b)
VOLCANOES (AND OTHER OCEANIC ISLANDS)
Today, many of the Philippine and Wallacean islands are generally regarded as oceanic islands because they have had no terrestrial connection to any surrounding land since their
emergence…. Consequently, their biota arose predominantly via
dispersal and not vicariance.
(c)
1
2
Lohman et al. (2011, p. 209)
Although dispersal may be ‘less parsimonious’ than vicariance…
sometimes it is still the only sensible explanation of a given pattern of distribution. For inhabitants of oceanic islands, this
would seem to be the case regardless of the age of the taxon.
Brower & Vane-Wright (2011, p. 602)
The two recent quotes above sum up what some consider
a rule of thumb: endemic taxa on oceanic islands must have
dispersed from terrestrial source areas. We reject this ‘rule’
because it assumes that the islands, and much of the sea surrounding them, were abiotic until life made the overseas
journey from the nearest continent.
Formation of a volcano or volcanic chain may be interpreted as a vicariance event. We illustrate a hypothetical
example in Fig. 1. A biota may range throughout a broad
area in the sea (Fig. 1a). Formation of a volcanic chain may
bisect the biota (Fig. 1b) and lead to its subsequent divergence into two sister biotas (Fig. 1c). The marine biota
evolves along with the volcanoes and, as the emerging volcanic islands become high enough to have established freshwater streams, taxa that once lived exclusively in the sea may
become part of the terrestrial island biota. This is a gradual,
co-evolutionary process. Once any land appears above sea
level, it will have a biota in its tidal pools and other saline
water bodies. The volcano supports a biota even before
freshwater streams are established. As an example, the
Hawaiian archipelago has five endemic freshwater fishes,
Eleotris sandwicensis, Awaous stamineus, Lentipes concolor,
Stenogobius hawaiiensis and Sicyopterus stimpsoni, all gobiiforms. The taxa (genera and their relatives) are widespread
throughout the tropics and inferred to be older than the
Hawaiian Islands (cf. Heads, 2011). The endemic species
may be the same age as or older than the archipelago; there
814
Figure 1 Simplified representation of the formation of a
volcanic chain bisecting a biota. (a) The range of a widespread
biota throughout the sea. (b) Formation of a volcanic chain
(arrows) in the biotic range. (c) Subsequent divergence of the
biota into two sister biotas, 1 and 2, and growth of the volcanic
chain.
is little genetic structure of species populations among the
islands, which may be interpreted as an indication that the
species are endemic to the archipelago, but not to individual
Hawaiian islands (Zink et al., 1996). The species have
diverged from close relatives: Awaous stamineus from Hawaii
and Awaous guamensis from Guam, once considered conspecific (Watson, 1992), have been shown to be genetically and
morphologically distinct (Lindstrom et al., 2012). To say that
the gobiiform fishes must have colonized the Hawaiian
Islands after they were formed because the islands are volcanic is to reject, a priori, the study and discovery of co-evolution of the islands and the fishes (see also Nelson, 2006;
Heads, 2012a).
We hypothesize that Hawaii’s endemic freshwater fish
lineages ranged throughout the region where the Hawaiian
Islands formed and, that the lineages of part of Hawaii’s
terrestrial biota ranged throughout that region, not necessarily as marine organisms, but on once emergent lands
(Cain, 1944, p. 222; Heads, 2012a). Whether distributed via
dispersal or vicariance, an insular terrestrial organism had
to be able to survive across a vast sea. Terrestrial Hawaiian
relicts include the endemic plant Hillebrandia sandwicensis,
inferred to have had broadly distributed boreotropic or
Journal of Biogeography 40, 813–820
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Evidence and hypothesis in biogeography
Malesian–Pacific close relatives (Clement et al., 2004; see
also Cowie & Holland, 2008).
TESTING BIOGEOGRAPHICAL PATTERNS
Sulawesi, in the heart of the Indo-Australian Archipelago, is
a group of islands that has a special place in biogeography
because of its high degree of endemism and complex geological history (Wallace, 1863, 1876; Hall, 2002). Sulawesi lies at
the junction of the Asian, Australian and Pacific plates (Hall,
2002; Villeneuve et al., 2002; Spakman & Hall, 2010). Biogeographically it has been recognized as an area of overlap or
interdigitation or a ‘… hinge between two worlds of life…’
(Croizat, 1958, p. 1196), Asian and Australian (Wallace,
1876). Wallacea, named formally by Dickerson et al. (1928,
p. 101), is a broad region in the centre of the Indo-Australian Archipelago that includes Sulawesi. Wallacea is an undiagnosable area in a comparative, systematic biogeographical
analysis (Parenti & Ebach, 2010): some areas within Wallacea
are more closely related to areas outside of Wallacea than
they are to each other.
Part of the two worlds that collided and overlap today
were identified by Parenti & Ebach (2010) as Indo-Malayan
and Pandora – biogeographical subregions that were disjunct
in the Oligocene, 30 Ma (Fig. 2). Recognizing and naming
Pandora as a separate subregion highlights the close relationship among portions of the modern biotas of Madagascar,
Australia and Sulawesi, and their surrounding seas, as demonstrated, for example, by species groups of the teleost genera Trimmatom and Hippocampus, and the gastropod genus
Strombus (see Parenti & Ebach, 2009, pp. 227–234), as well
as by atherinomorph rainbowfishes in the family Melanotaeniidae (Sparks & Smith, 2004) and terapontid perches of the
genus Mesopristes (Vari, 1992).
Once proposed, Pandora is open to test. The disjunct
distribution of Madagascan/Melanesian sister groups of
boas of the genera Candoia (Melanesian) and Sanzinia
(Madagascar) was concluded to be (Austin, 2000, p. 348)
‘…not the result of a recent dispersal event’. More
recently, Chakrabarty et al. (2012) hypothesized that
the south-western Madagascan endemic gobiiform genus
Typhleotris is the sister group of the north-western Australian endemic genus Milyeringa. These are blind, obligate
cave fishes that live in similar subterranean karst habitats.
Chakrabarty et al. (2012, p. 1) describe this as an ‘…
extraordinary case of Gondwanan vicariance’. We consider
the boa and blind gobiiform distributions as more support
for Pandora.
The modern overlap of the western (eastern Indo-Malayan) and eastern (eastern Pandora) segments of the IndoAustralian biota in eastern Borneo, southern Philippines and
south-western Sulawesi – the ‘hinge’ of Croizat – is seen in
the atheriniform fish family Phallostethidae. Its two subfamilies, Phallostethinae and Denatherininae (Parenti & Louie,
1998), together range broadly from Thailand to Fiji (Fig. 3).
There are no known fossil phallostethids. As sister taxa, phallostethines and dentatherines are logically of the same age.
We hypothesize that the ancestral population was widespread, perhaps throughout the Meso-Tethys Sea (Hall,
2011), then was disrupted by reconstruction and rearrangement of land and changes in sea level that may have facilitated expansion of one taxon into the range of the other.
Asking whether they came from the west or the east is moot
as it does not address the biogeographical question of how
they diverged and now overlap in the centre of their distribution ranges (see also Ladiges et al., 2012). As it has since
the time of Wallace, understanding the evolution of such
biogeographical distributions centres on Sulawesi.
Indo-Malayan
Pandora
*
Figure 2 Biogeographical subregions Pandora and Indo-Malayan depicted on an early Oligocene (30 Ma) reconstruction of global
tectonic plate arrangement (map from University of Texas Institute for Geophysics). The asterisk (*) approximates the location of the
South Pandora Ridge in North Fiji (Parenti & Ebach, 2010, figure 15.6). Copyright 2010 by the Regents of the University of California.
Journal of Biogeography 40, 813–820
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815
L. R. Parenti and M. C. Ebach
110 E
130 E
150 E
170 E
Pacific Ocean
20 N
Dentatherininae
0
0
Phallostethinae
10 S
Indian Ocean
90 E
110 E
130 E
Figure 3 Distribution limits of the freshwater and coastal Phallostethinae and its sister taxon, the marine shorefish Denatherininae
(following Parenti & Louie, 1998). The western (eastern Indo-Malayan) and eastern (eastern Pandora) clades overlap in the centre of the
Indo-Australian Archipelago.
Where and How did the unique biota of Sulawesi evolve?
Stelbrink et al. (2012) concentrate on the hypothetical How
and apply a popular approach. Time of divergence between a
Sulawesi taxon and its extra-Sulawesi sister group is estimated using a relaxed molecular clock. That time is compared with temporal estimates of presumed relevant
vicariance events imposed by a geological model. If the taxon
divergence time is the same as or older than the inferred
vicariance event, vicariance is supported. If the taxon divergence time is younger than the inferred vicariance event, dispersal is supported. Despite the logical appeal of this method
(e.g. de Queiroz, 2005; Sanmartın et al., 2008; Crisp et al.,
2009), its application has been seriously flawed (Nelson &
Ladiges, 2009; Brower & Vane-Wright, 2011; Heads, 2012b).
Molecular sequence differences constitute empirical evidence.
An estimate of divergence time requires calibration of a
molecular clock and is a hypothesis, not empirical evidence.
Further, minimum ages of taxa as estimated from oldest fossils have been treated illogically as maximum ages in selection of prior probability curves in Bayesian estimates of
divergence times in biogeographical analyses rendering their
results spurious (see especially Heads, 2012b).
After analysing 27 datasets representing 20 taxa, Stelbrink
et al. (2012, p. 2267) conclude: ‘Dispersal seems the primary
mechanism of bringing taxa to the island and a standardized
molecular clock approach has [led] to the falsification of
vicariance hypotheses for some Sulawesi taxa of Asian origin.’ Historical biogeography is limited in what it can say
about explicit processes such as vicariance and dispersal. The
analyses and conclusions of Lohman et al. (2011) and Stelbrink et al. (2012) are problematic for several reasons. First,
they assume that vicariance is old and dispersal is new. Yet
cyclical changes in sea level are hypothesized to have facilitated the spread of the freshwater biota throughout Sundaland sensu Metcalfe (2011) and the subsequent fragmentation
of the land and its biota (Molengraaff & Weber, 1921). We
hypothesize dispersion of a biota (sensu Platnick, 1976), followed by vicariance. This is likely to be followed by more
816
dispersion and more vicariance. Here, we mean range expansion or normal ecological dispersal sensu Heads (2012a), not
dispersal from a centre of origin. Second, Lohman et al.
(2011) and Stelbrink et al. (2012) focus on the timing of a
particular geological event and invoke dispersal or vicariance
as an explanation where lineage divergence time is younger
or older, respectively, than the event. But that method can
reject only particular vicariance events, not identify what
other vicariance event may be invoked as an explanation.
Lastly, and most importantly, Stelbrink et al. (2012,
p. 2265) also remark:
Not only is there no obvious respective pattern in the distribution of lineages that have colonized Sulawesi independently, there
is in our opinion also little hard evidence for any Sulawesi clade
being confined to part of the island only, which might suggest a
link of its origin on Sulawesi and tectonic processes.
To address the second assertion first, restricted endemism
in Sulawesi is well documented (Michaux, 2010; Thomas
et al., 2011; Heads, 2012a). The vastly different, disjunct floras of the Latimodjong Mountains and Mount Lompobatang
(Bonthain) in south-western Sulawesi were described by Croizat (1964, p. 228) as ‘…ancient blocks of life [that] face
each other in age-long immobilism’ [italics in the original].
Ricefishes, a taxon in the Stelbrink et al. (2012) analysis,
include the genus Adrianichthys comprising four species, all
endemic to Lake Poso, central Sulawesi (Parenti, 2008).
To return to the first assertion, Stelbrink et al. (2012)
claim that there is no pattern in the distribution of lineages.
But they did not look for a biogeographical pattern. Instead,
they assume, a priori, independent dispersal or vicariant origins of Sulawesi taxa in line with the philosophy of Crisp
et al. (2011), who argue that process, not pattern, is primary
in biogeography. We note that by ‘pattern’ Crisp et al.
(2011) mean, for example, a single phylogenetic hypothesis
of a single taxon used as the basis for biogeographical inference. In contrast, by ‘pattern’ we mean the comparison of
more than one statement of area relationship across a range
of taxa (Parenti & Ebach, 2009).
Journal of Biogeography 40, 813–820
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Evidence and hypothesis in biogeography
Table 1 Informative areagrams or relationships among the four areas – Sulawesi, Asia, Southeast Asia (Philippines, Moluccas, Lesser
Sunda Islands East of Bali) and Australia (including New Guinea), as specified by the cladograms in Stelbrink et al. (2012) for each of
their 27 molecular datasets.
Dataset no.
Taxon
Dataset type
Informative area relationship
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
Mite harvestmen
Water beetles
Freshwater snails
Freshwater crabs
Shrews
Shrews
Macaques
Phalangerids
Water beetles
Sailfin silversides
Cockroaches
Squirrels
Squirrels
Megapodes
Fanged frogs
Fanged frogs
Tarsiers
Grasshoppers
Ricefishes
Bovids
Toads
Water beetles
Ricefishes
Macaques
Water snakes
Freshwater bivalves
Pigs
concatenated
Cyt b
16S
16S
Cyt b
Cyt b
NADH
16S
COI
ND5
COII
16S
12S
ND2
16S
12S
Cyt b
COI
16S
Cyt b
12S
16S
12S
12S
Cyt b
COI
control region
none
Sulawesi (Asia, Australia)
Asia (Sulawesi, Australia)
none
Sulawesi (Asia, Southeast Asia)
Asia (Sulawesi, Southeast Asia)
none
none
Australia (Sulawesi, Asia)
none
Sulawesi (Asia, Australia)
none
none
none
none
none
none
none
none
Sulawesi (Asia, Southeast Asia)
none
Asia (Sulawesi, Australia)
Sulawesi (Asia, Southeast Asia)
none
(Australia, Southeast Asia) (Sulawesi, Asia)
Australia (Sulawesi, Asia)
Australia (Sulawesi, Asia)
Is there a biogeographical pattern expressed by the distribution of the 20 Sulawesi taxa examined by Stelbrink et al.
(2012)? We extracted informative three-area statements of
area relationship (Nelson & Ladiges, 1996; Parenti & Ebach,
2009) from the 27 cladograms of Stelbrink et al. (2012). A
hypothetical informative three-area relationship is X(Y,Z).
An uninformative area relationship is X(X,Z), in which X is
paralogous or repeated. The data may be analysed by hand
or by implementing a computer algorithm, as described in
Parenti & Ebach (2009). The 20 taxa live in four general
areas recognized by Stelbrink et al. (2012): Sulawesi, Asia,
Southeast Asia (Philippines, Moluccas, and Lesser Sunda
Islands East of Bali) and Australia (including New Guinea).
Relationships in this example are simple enough that we
can extract informative statements of area relationship manually (Table 1). Of the 27 areagrams, 15 have no informative
area relationships. Among the remaining 12, there are eight
informative area relationships (A–H; Table 2), distributed as
in Table 3. Three of the three-area statements, A, C and D,
summarize the relationships among Asia, Sulawesi and
Australia. Of these, C (Australia (Sulawesi, Asia)), is shared
by four clades – water beetles, water snakes, freshwater bivalves and pigs – and may be considered a general pattern.
Alternative patterns, A (Sulawesi (Asia, Australia)) and D
(Asia (Sulawesi, Australia)), are each supported by two
clades. Another informative area relationship, G (Sulawesi
Journal of Biogeography 40, 813–820
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(Australia, Southeast Asia)), is unique to clade 25, water
snakes, hence not a general pattern. Three other informative
area relationships, B, E and F, are less useful in this analysis
because they do not include any areas east of Sulawesi. Informative area relationship H is of no value in this analysis
because it does not include Sulawesi.
Why the conflict or seeming lack of resolution? Modern
Sulawesi is a biogeographical and geological composite area
that harbours several different biotic areas (e.g. Thomas et al.,
2011, figure 4; Heads, 2012a, figures 5–16). We have identified a general pattern, C (Australia (Sulawesi, Asia)). Yet any
or all of the three broadly informative area relationships – A,
C and D – may be supported by other taxa and indicate alternative general patterns. This is the type of conflict or incongruence we would expect when trying to infer the biotic
relationships of a geological composite such as Sulawesi, especially from datasets that treat Sulawesi as one area. Further,
the conflict reflects the overlap of Asian and Australian biotas
in the centre of the Indo-Australian Archipelago, as discussed
above and illustrated for phallostethid fishes (Fig. 3).
To discover a robust general biogeographical pattern, we
need to recognize the separate biotic areas of Sulawesi and
other composites based on taxic distributions that span the
Indo-Australian Archipelago. Yet, Stelbrink et al. (2012) provide no distribution maps or detailed descriptions of taxon
distributions. Do shrews live throughout Sulawesi or are they
817
L. R. Parenti and M. C. Ebach
Table 2 The eight informative three-area statements (A–H)
specified by the 12 areagrams of Table 1.
A: Sulawesi (Asia, Australia)
B: Sulawesi (Asia, Southeast Asia)
C: Australia (Sulawesi, Asia)
D: Asia (Sulawesi, Australia)
E: Asia (Sulawesi, Southeast Asia)
F: Southeast Asia (Sulawesi, Asia)
G: Sulawesi (Australia, Southeast Asia)
H: Asia (Australia, Southeast Asia)
CONCLUSIONS
Table 3 Distribution of the eight (A–H) informative three-area
statements (Table 2) among the 12 areagrams, numbered as in
Table 1.
Informative area
Statement
Dataset no.
Taxon
A
A
B
B
B
C
C
C
C
D
D
E
F
G
H
2
11
5
20
23
9
25
26
27
3
22
6
25
25
25
Water beetles
Cockroaches
Shrews
Bovids
Ricefishes
Water beetles
Water snakes
Freshwater bivalves
Pigs
Freshwater snails
Water beetles
Shrews
Water snakes
Water snakes
Water snakes
restricted to particular regions? Mapping is critical to biogeographical inference. The overlap of the sister clades of phallostethid fishes simply illustrate one part of the complexity of
the Sulawesi biota, for example (Fig. 3).
Detailed description of areas of endemism in Sulawesi is still
inchoate. About one half of the approximately 60 endemic species of Sulawesi freshwater fishes have been described since 1989
(Parenti, 2011). Phallostethids as a taxon were unknown from
Sulawesi until collected in 1995 and described in 1998 (Parenti
& Louie, 1998). No ricefishes were known to science from
south-eastern Sulawesi until their collection in 2007 and
description three years later (Parenti & Hadiaty, 2010). Interestingly, the ricefish species described in 2010 is endemic to
Muna Island, a terrane hypothesized to have been submerged
until it started to emerge some 15 Ma (Spakman & Hall, 2010).
For the purposes of biogeography, we view the emergence of
once submerged landmasses as analogous to the formation of a
volcano (see above).
Is Sulawesi a single biotic area with a unique history or a
composite biotic area (the problem posed by Wallace in
1876)? Lohman et al. (2011) and Stelbrink et al. (2012) do
not ask this important biogeographical question. Instead,
they generate a series of hypotheses or explanations without
considering biogeographical patterns in the form of biotic
818
area relationships. Despite their claims, Lohman et al. (2011,
p. 214) have not illustrated ‘…patterns of dispersal and
diversification illuminated by molecular phylogenetic and
phylogeographic evidence’ [italics added].
Evidence and hypothesis are not always distinguished in
historical biogeographical studies. Inferences that result from
application of methods, such as optimization of areas on a
cladogram to infer an ancestral area, or assumptions about
mechanism, such as ‘volcanoes must always be colonized by
dispersal’, add an unnecessary bias or constraint. We may
speculate about the process or mechanism that may have
caused a particular distribution, but always as a hypothesis,
not as evidence. Rejecting particular vicariance events to
explain a distribution does not demonstrate dispersal as it
ignores other vicariance events that may be invoked as an
explanation.
We offer an alternative line of investigation that extracts
and summarizes information from distributions and phylogenetic relationships: biotic area relationships, namely pattern.
Rather than trying to explain individual distributional histories, we are able to reconstruct the history of biotic areas,
their relationships to each other and may consider the abiotic factors (such as climate, tectonics or orogeny) that have
shaped them. When we change our focus from individual
taxon histories to shared biotic area histories, we move historical biogeography beyond the dispersal versus vicariance
debate to a period of discovery.
ACKNOWLEDGEMENTS
Plate tectonic reconstruction maps were obtained through
the courtesy of Lisa Gahagan and Lawrence Lawver, University of Texas Institute for Geophysics, The Plates Project
(http://www.ig.utexas.edu/research/projects/plates/).
Three
referees provided thoughtful comments that improved the
text. Figure 2 was published originally as Figure 15.6 in Parenti & Ebach (2010); it is reproduced here with permission
of the University of California Press.
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BIOSKETCHES
Lynne R. Parenti is a Curator of Fishes and Research Scientist at the National Museum of Natural History, Smithsonian Institution, Washington, D.C. She studies the
systematics, biogeography and reproductive biology of bony
fishes, collections-based comparative biology, and the theory
and methods of biogeography.
Malte C. Ebach is an ARC Future Fellow and Senior Lecturer in the School of Biological, Earth and Environmental
Science (BEES) at the University of New South Wales
(UNSW). Malte’s research focuses on Australasian biogeography, the historical development of phyto- and zoogeography,
and classification.
Editor: Liliana Katinas
Journal of Biogeography 40, 813–820
ª 2013 Blackwell Publishing Ltd