Birds of paradise, biogeography and ecology in New Guinea: a review
Birds of paradise, biogeography and ecology in New Guinea: a review
Birds of paradise, biogeography and ecology in New Guinea: a review
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916 M. Heads<br />
where the taxa do not range to the top <strong>of</strong> the latter, could be<br />
partly expla<strong>in</strong>ed by differential uplift ± the mounta<strong>in</strong>s are<br />
lower <strong>in</strong> Milne Bay, for example, because there has been less<br />
uplift there <strong>and</strong> for the same reason the altitud<strong>in</strong>al vegetation<br />
b<strong>and</strong>s have rema<strong>in</strong>ed telescoped together. The more or<br />
less constant wet-season mists also lie much lower on these<br />
isolated mounta<strong>in</strong>s than <strong>in</strong> the central Highl<strong>and</strong>s, where they<br />
usually only descend to about 2700 m (pers. obser., around<br />
Goroka). This may expla<strong>in</strong> the survival <strong>of</strong> moss forest<br />
communities at low altitudes on the isolated mounta<strong>in</strong>s, but<br />
perhaps not their orig<strong>in</strong>.<br />
It is <strong>of</strong>ten thought that mounta<strong>in</strong>s are uplifted <strong>and</strong> then<br />
<strong>in</strong>vaded by a new ¯ora <strong>and</strong> fauna from elsewhere. However,<br />
before the l<strong>and</strong> was uplifted it was not an ecological vacuum.<br />
There would have been a diverse array <strong>of</strong> plants <strong>and</strong> animals<br />
present, some <strong>of</strong> which would have been able to survive uplift<br />
by pre-adaptation (or adaptation), while many other populations<br />
would die out. This would allow pre-adapted taxa to<br />
atta<strong>in</strong> a very wide altitud<strong>in</strong>al range, <strong>and</strong> many such taxa are<br />
known <strong>in</strong> <strong>New</strong> Gu<strong>in</strong>ea. Like the family Paradisaeidae, the<br />
most diverse bird genera <strong>in</strong> <strong>New</strong> Gu<strong>in</strong>ea, Ptil<strong>in</strong>opus Swa<strong>in</strong>son<br />
(fourteen species) <strong>and</strong> Pachycephala (®fteen species),<br />
range from mangrove forest to 3400 <strong>and</strong> 3650 m, respectively,<br />
<strong>and</strong> at species rank trees like Schuurmansia henn<strong>in</strong>gsii<br />
range widely from sea-level to 3000 m (Kanis, 1978).<br />
Whether the `montane' elements occur at low altitude<br />
through downwarp<strong>in</strong>g <strong>of</strong> terranes bear<strong>in</strong>g these populations,<br />
or because there has been relatively little uplift there<br />
compared with the ma<strong>in</strong> central mounta<strong>in</strong>s, it seems<br />
unrealistic to discuss the altitud<strong>in</strong>al range <strong>of</strong> communities<br />
<strong>and</strong> taxa without reference to the geological changes <strong>of</strong><br />
altitude by orogenic <strong>and</strong> epeirogenic uplift, sedimentation,<br />
downwarp<strong>in</strong>g <strong>and</strong> erosion.<br />
Ophiolite endemism<br />
It is suggested here that the distributions <strong>of</strong> the birds <strong>of</strong><br />
<strong>paradise</strong> ma<strong>in</strong>ly re¯ect geological change, <strong>and</strong> are generally<br />
much older than was thought. Unlike chance dispersal <strong>and</strong><br />
chance ext<strong>in</strong>ction this tectonic hypothesis seems to account<br />
for some <strong>of</strong> the st<strong>and</strong>ard aspects <strong>of</strong> the distribution patterns<br />
<strong>and</strong> leads to <strong>in</strong>terest<strong>in</strong>g, testable correlations.<br />
An example <strong>of</strong> biogeographical <strong>and</strong> tectonic correlation is<br />
that <strong>of</strong> endemism on ultrama®c terranes. Rocks with less than<br />
45% silica are rare <strong>and</strong> are termed ultrabasic or ultrama®c<br />
(that is, high <strong>in</strong> magnesium <strong>and</strong> iron). They usually occur as<br />
part <strong>of</strong> ophiolitic igneous suites, or ophiolites, which comprise<br />
pillow basalts, massive gabbros, <strong>and</strong> serpent<strong>in</strong>ized<br />
ultrama®cs. The presence <strong>of</strong> ultrama®cs on the earth's<br />
surface is <strong>of</strong> great tectonic signi®cance as they are sections<br />
<strong>of</strong> oceanic crust <strong>and</strong> upper mantle that have been uplifted <strong>and</strong><br />
obducted onto l<strong>and</strong> (rather than subducted below it). This<br />
has occurred at plate marg<strong>in</strong>s dur<strong>in</strong>g isl<strong>and</strong>-arc collision, <strong>and</strong><br />
accreted arc terranes <strong>and</strong> orogenic belts frequently <strong>in</strong>clude<br />
ophiolites. In the Western Papuan Isl<strong>and</strong>s, Waigeo, Batanta<br />
<strong>and</strong> nearby Ko®au (but not Salawati) comprise an ophiolite<br />
complex, the Waigeo terrane (Pigram & Davies, 1987).<br />
Waigeo <strong>and</strong> Batanta are also dist<strong>in</strong>guished by the presence <strong>of</strong><br />
local endemics such as Cic<strong>in</strong>nurus respublica (Bonaparte)<br />
<strong>and</strong> Paradisaea rubra (Fig. 27). Similarly, Melidora Lesson<br />
(Alced<strong>in</strong>idae) is widespread <strong>in</strong> <strong>New</strong> Gu<strong>in</strong>ea west to Waigeo<br />
<strong>and</strong> Batanta, but is not on Salawati. The straits between<br />
Salawati <strong>and</strong> Batanta Isl<strong>and</strong>s are less than two miles wide,<br />
but `have prevented the cross<strong>in</strong>g' <strong>of</strong> seventeen species <strong>of</strong><br />
Salawati birds to Batanta <strong>and</strong> ®ve from Batanta to Salawati<br />
(Mayr, 1940). It seems more likely that this strik<strong>in</strong>g faunistic<br />
difference is due to different tectonic <strong>and</strong> evolutionary<br />
histories, rather than to a 2-mile wide sea-barrier.<br />
The <strong>New</strong> Gu<strong>in</strong>ea orogen is characterized by abundant<br />
outcrops <strong>of</strong> ultrama®c rocks. The largest <strong>of</strong> these, the<br />
Papuan Ultrama®c Belt (Bowutu terrane) covers an area<br />
400 ´ 40 km <strong>and</strong> is one <strong>of</strong> the world's most spectacular<br />
ophiolites. It forms a series <strong>of</strong> subsidiary mounta<strong>in</strong> ranges<br />
north <strong>of</strong> the ma<strong>in</strong> ranges <strong>of</strong> the Papuan Pen<strong>in</strong>sula <strong>and</strong> its<br />
emplacement must have been a major tectonic event.<br />
Botanists have long recognized that these northern <strong>New</strong><br />
Gu<strong>in</strong>ea ultrama®cs were strong foci <strong>of</strong> endemism (e.g.<br />
Kairothamnus Airy Shaw ± Airy Shaw, 1980; Calophyllum<br />
streimannii Stevens ± Stevens, 1974a), but it was felt that<br />
much <strong>of</strong> this endemism was the result <strong>of</strong> edaphic rather than<br />
historical factors. Polhemus (1996) po<strong>in</strong>ted out that although<br />
many animals (e.g. Parotia lawesii helenae) show similar<br />
patterns, zoologists have been slow to realize that this<br />
correlation greatly weakens the edaphic hypothesis. Instead,<br />
Polhemus (1996) regarded the ophiolites as biogeographically<br />
signi®cant because they are arc terrane markers. The<br />
most mature phase <strong>of</strong> arc collision is seen <strong>in</strong> old arc fragments<br />
now deeply embedded <strong>in</strong> modern ma<strong>in</strong>l<strong>and</strong>s, such as <strong>New</strong><br />
Gu<strong>in</strong>ea <strong>and</strong> the Philipp<strong>in</strong>es. The remnants <strong>of</strong> these Mesozoic<br />
arc systems have been crushed between even older arcs or<br />
cont<strong>in</strong>ents but have left a biological signature <strong>in</strong> the disjunct<br />
distributions <strong>of</strong> liv<strong>in</strong>g taxa.<br />
Survival <strong>of</strong> taxa <strong>in</strong> situ<br />
At ®rst it seemed unlikely that bird taxa would ma<strong>in</strong>ta<strong>in</strong><br />
their distributions over geological time as precisely as<br />
<strong>in</strong>dicated here. However, results from another ®eld ±<br />
ecological studies <strong>of</strong> current populations ± also show that<br />
<strong>New</strong> Gu<strong>in</strong>ea ra<strong>in</strong>forests <strong>and</strong> their bird fauna have a great<br />
capacity to survive more or less <strong>in</strong> situ, despite high levels <strong>of</strong><br />
disturbance by volcanic activity, movement on faults,<br />
l<strong>and</strong>slides, rivers chang<strong>in</strong>g course, storms, human activity,<br />
<strong>and</strong> as seen dramatically <strong>in</strong> 1997, drought <strong>and</strong> ®re. Life is<br />
`stickier' <strong>and</strong> less easily `eroded' away than biologists <strong>of</strong>ten<br />
assume. Comparatively few <strong>New</strong> Gu<strong>in</strong>ea ra<strong>in</strong>forest trees<br />
regenerate <strong>in</strong> full shade <strong>and</strong> the long-held idea <strong>of</strong> tropical<br />
ra<strong>in</strong>forest as fragile <strong>and</strong> undisturbed has more recently been<br />
rejected by ecologists (Johns, 1986). So it is not surpris<strong>in</strong>g<br />
that while all birds <strong>of</strong> <strong>paradise</strong> are generally found <strong>in</strong> closed<br />
ra<strong>in</strong>forest, the vast majority are also occasionally seen <strong>in</strong> at<br />
least one <strong>of</strong> the follow<strong>in</strong>g: forest edge, secondary or broken<br />
forest, selectively logged forest, disturbed forest near villages,<br />
ab<strong>and</strong>oned gardens, <strong>and</strong> even open agricultural l<strong>and</strong> with<br />
scattered shrubs. Parotia se®lata is most abundant <strong>in</strong> wellestablished<br />
secondary forest, Lophor<strong>in</strong>a superba (Pennant) is<br />
Ó Blackwell Science Ltd 2001, Journal <strong>of</strong> Biogeography, 28, 893±925