Patterns of Biodiversity and Endemism on Indo-West Pacific Coral Reefs Author(s): Marjorie L. Reaka, Paula J. Rodgers and Alexei U. Kudla Source: Proceedings of the National Academy of Sciences of the United States of America, Vol. 105, In the Light of Evolution II: Biodiversity and Extinction (Aug. 12, 2008), pp. 11474-11481 Published by: National Academy of Sciences Stable URL: http://www.jstor.org/stable/25463366 Accessed: 04-06-2018 17:14 UTC REFERENCES Linked references are available on JSTOR for this article: http://www.jstor.org/stable/25463366?seq=1&cid=pdf-reference#references_tab_contents You may need to log in to JSTOR to access the linked references. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact
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Patterns of biodiversity and endemism on Indo-West Pacific coral reefs Marjorie L. Reaka**, Paula J. Rodgers*, and Alexei U. Kudla* *Department of Biology, University of Maryland, College Park, MD 20742; and *Georgetown University School of Medicine, Washington, DC 20007
Diversity of the primary groups of contemporary Indo-West Pacific coral reef organisms, including mantis shrimps (stomatopod crus taceans), peaks in the Indo-Australian Archipelago (IAA), reaches a lower peak in East Africa and Madagascar [Indian Ocean continen tal (IOC)], and declines in the central Indian Ocean (IO) and Central Pacific (CP). Percent endemism in stomatopods (highest in the IAA, high in the IOC, lower in regions adjacent to centers, and moderate in the CP) correlates positively with species diversity (this varies
with scale) and inversely with species body size. Because it con strains reproductive traits and dispersal, body size is a reliable indicator of speciation and extinction potential in reef stomato pods and probably most marine organisms. Assemblages are dom inated by small-sized species in the IAA and IOC. Both speciation and extinction likely are high, resulting in especially high ende mism (small ranges reflect both originating and disappearing species) in these regions. Rates of speciation exceed extinction,
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yielding centers of diversity (especially in the IAA). Dispersal slows
speciation and extinction in areas adjacent to these centers. Body size declines toward the CP, especially in atoll environments. Here the wheels of speciation and extinction again spin rapidly but in
the opposite direction (extinction > speciation), yielding low
diversity and moderate endemism. We conclude that life histories, dispersal, and speciation/extinction dynamics are primary agents that mold patterns of diversity and endemism. Historical factors, currents, productivity, and species diversity itself (through ecolog ical interactions) also influence these patterns, in some cases by altering body size. hot spots | stomatopod | life history | geographic range | body size
Beingspecialized repositories of are ancient as well as more recent taxa, coral reefs among thephyla most spectacular, productive, diverse (per unit area), and threatened ecosystems
on earth. Organisms they house provide a critical source of
protein for people in many tropical countries, and reefs them selves protect human populations from storm and wave damage. Coral reefs provide aesthetic beauty (and the bioeroded sand on beaches) for tourism?an increasingly important economic re source for developing tropical countries. However, tourism and other uses of reefs must be carefully managed to be of sustain able economic benefit. A fundamental value of coral reefs is that they provide an aesthetic, intellectual, educational, and cultural heritage for present and future generations. Threats to global coral reefs, however, are severe and well documented (1-9). Overexploitation has been identified as an especially serious problem, but other threats include coastal development and sedimentation, pollution, global warming,
disease, and ocean acidification. The Global Coral Reef Mon itoring Network reports that 20% of global coral reefs already
have been degraded beyond recovery, an additional 24% are
under imminent threat of collapse, and a further 26% are at longer-term risk (10). In the Indo-West Pacific (IWP), 88% of Southeast Asian reefs and 61% and 54% of Middle Eastern and
Indian Ocean (IO) reefs are at medium to high risk (1, 2). Human population density near reefs is particularly high in
Fig. 1. Dorsal view of typically sized reef stomatopods (large Gonodactyla ceus falcatus, small Gonodactylellus incipiens; scale bar for both is 10.0 mm),
lateral view of raptorial claw, and photograph of individual delivering a threatening display at the entrance of its burrow (Gonodactylaceus ternat ensis, courtesy of Roy Caldwell). Drawing of the raptorial claw shows the merus (m), meral spot (ms, varies in color from white through yellow, orange, red, pink, purple, and blue among species), propodus (p), and dactyl (d); p and
d normally are folded against m but are opened (arrow) either together as a hammer or with d projected as a spear. The photograph shows species-specific
coloration of the flared antennal scales (blue) and setae (red) and spread raptorial claws of the display (yellow ms surrounded by white ring).
Despite the biological, cultural, and economic value of coral reefs and the widely publicized alarm at their global decline, it remains astonishing how little we know about the patterns of diversity ("diversity" will be used equivalently to species rich ness) on coral reefs that would help us manage and conserve them. This article will (/) review and provide new information on the geography of coral reef diversity in the IWP using informa
tion from the most ecologically important and well known
groups of reef organisms, (ii) provide a brief overview of the major factors that generate these patterns, and (iii) briefly review
"hotspots" and provide new information on endemism in reef stomatopods. (iv) We will then examine information on body size, life history characteristics, geographic ranges, and specia tion/extinction dynamics of reef stomatopods and other organ
This paper results from the Arthur M. Sackler Colloquium of the National Academy of Sciences, "In the Light of Evolution II: Biodiversity and Extinction," held December 6-8, 2007, at the Arnold and Mabel Beckman Center of the National Academies of Sciences and Engineering in Irvine, CA. The complete program and audio files of most presentations are available on the NAS web site at www.nasonline.org/Sackler_biodiversity.
Author contributions: M.L.R. designed research; M.L.R., P.J.R., and A.U.K. performed research; M.L.R., P.J.R., and A.U.K. analyzed data; and M.L.R., P.J.R., and A.U.K. wrote the
paper.
The authors declare no conflict of interest.
+To whom correspondence should be addressed. E-mail:
[email protected].
Southeast Asia and the IO. Pacific reefs are in better condition
This article contains supporting information online at www.pnas.org/cgi/content/full/
(59% at low risk), with more protected area, than those in other regions.
? 2008 by The National Academy of Sciences of the USA
0802594105/DCSupplemental.
11474-11481 | PNAS | August 12,2008 | vol.105 | suppl. 1 www.pnas.org/cgi/doi/10.1073/pnas.0802594105 This content downloaded from 142.103.160.110 on Mon, 04 Jun 2018 17:14:37 UTC All use subject to http://about.jstor.org/terms
Fig. 2. Contours of species richness for reef stomatopods in the IWP. Numbers represent species present in each contour. Arrows indicate major currents. All species of Alainosquillidae, Gonodactylidae, Odtontodactylidae, Protosquillidae, and Takuidae are included; Pseudosquillidae occur on reefs but are excluded from analysis because their reproductive, larval, and life history patterns differ from those of other reef-dwelling families (27-29). Data are from our own collections, National Museum of Natural History collections, and published literature [updated to currently accepted taxonomy (30, 31)].
isms to suggest mechanisms that, in combination with environ and peaks again in the Caribbean (13-26). The first diversity contour map for reef stomatopods (Fig. 2) shows a similar mental factors, can explain the observed patterns of IWP coral pattern, with a high, sharp peak in the central IAA and an area reef diversity and endemism. of elevated diversity in the northwestern IO that increases We will focus on reef-dwelling mantis shrimps as a model taxonomic group for such analyses because these crustaceans are southward to a secondary peak around Madagascar. Similar to important members of the benthic community. All stomatopods most other taxa where contours of diversity are known, tails of diversity extend from the IAA toward the southeast and are predators with a pair of enlarged, equally sized raptorial northeast. claws that are used to smash and spear prey, competitors, and predators (Fig. 1). Protective holes in the substrate are a limiting Explanations of IWP Diversity Gradients resource because of strong fish predation; stomatopods exhibit After considering all explanations for patterns of IWP reef colorful communicatory displays and intense territorial fighting biodiversity, we identify here only those that are most applicable to maintain exclusive ownership of these holes (11, 12). to the present study. Patterns of Coral Reef Diversity Species diversity for several marine taxa (fishes, corals, lobsters,
and snails) reaches a global maximum in the "East Indies triangle" (Malaysia, Indonesia, New Guinea, and the Philip
pines) of the Indo-Australian Archipelago (IAA), declines in the IO (with heightened diversity in some parts of the western IO for many taxa), declines eastward across the Central Pacific (CP),
Faunal Carryover Hypothesis. Species from a Mesozoic/early Ce nozoic center of diversity in Europe migrated east to the IAA and probably south along the continental margin of the Indian Ocean (IOC) as the Tethys Seaway was closed by the collision of
Africa with Eurasia between the Paleocene and Miocene (17 19). High stomatopod diversity in the IAA and in the western/ southwestern IO (Fig. 2) is consistent with this hypothesis.
Global Biosphere
Phytoplankton Pigment Concentration (mg/m3)
BDDDDDBHB
0.05). Average endemism for the 21 local sites is 10.5 ? 2.6% (SE).
"Restricted regional endemics"?those known from local
sites, archipelagos, and parts of regions?are widespread but reach their highest incidences (>15%) in the Malay Peninsula/ Indonesia/Philippines, Red Sea, Mascarene Islands, Madagascar/
Comores Islands, Society Islands, and Hawaiian Islands [see supporting information (SI) Fig. SI]. However, the distribution
of restricted regional endemics does not differ from those expected when the diversities of their subregional stomatopod 100
S3 All species
u High Islands N$
2 60 E Low Islands W
z* II Hi Endemic Nonendemic
Fig. 7. Number of regional endemic vs. nonendemic species of reef stomato pods and those occurring on high vs. low islands.
increases signif among species of gonodactylid (open diamonds) an squares) reef stomatopods (r2 = 0.55, F = 92.74, P 1291.69).
faunas are considered (x2 = 25.13, df = 23, P > 0.05). Endemism across the 24 subregions averages 14.5 ? 2.1%. To examine patterns of endemism at a larger scale, the IWP
was divided into major "regions" of continental and oceanic habitat types. At this scale, percent endemism (squares) is
significantly concentrated in the IAA and drops in the adjacent oceanic regions but then rises toward the west in the IOC and, to a lesser extent, toward the east in the West Central Pacific and especially the CP (jc2 = 26.23 using raw numbers of endemics/
nonendemics, df = 5, P < 0.001; Fig. 5). Average endemism
among the six regions is 20.2 ? 6.1%. The percent regional endemism increases significantly with regional species richness (Fig. 6; r2 = 0.74, P = 0.03, F = 11.41, y = O.O&t + 1.61, square-root-transformed data). The percent regional endemism is inversely related to body size among regions, decreasing with increased median body size
(Fig. 6; r2 = 0.65, P = 0.05, F = 7.53, y = 0.1(k + 8.16,
square-root-transformed data) and increasing with percentage of species in each region that are 40 mm and
