Copyright (c) 2013 University of Iowa All rights reserved. http://ir.uiowa.edu/geog_pubs Recent documents in Department of Geography Publications en-us Tue, 18 Jun 2013 11:13:57 PDT 3600 http://ir.uiowa.edu/geog_pubs/449 http://ir.uiowa.edu/geog_pubs/449 Tue, 13 Sep 2011 19:48:38 PDT C. C. Wallace et al. http://ir.uiowa.edu/geog_pubs/448 http://ir.uiowa.edu/geog_pubs/448 Tue, 13 Sep 2011 19:48:33 PDT H. M. Ruiz et al. http://ir.uiowa.edu/geog_pubs/447 http://ir.uiowa.edu/geog_pubs/447 Tue, 13 Sep 2011 19:48:30 PDT H. Ruiz et al. http://ir.uiowa.edu/geog_pubs/446 http://ir.uiowa.edu/geog_pubs/446 Tue, 13 Sep 2011 19:48:26 PDT H. Ruiz et al. http://ir.uiowa.edu/geog_pubs/445 http://ir.uiowa.edu/geog_pubs/445 Tue, 13 Sep 2011 19:48:21 PDT The Pleistocene extinction of the widespread organ-pipe Montastraea coral had measurable morphological and ecological effects on surviving lineages of the Montastraea "annularis" species complex. Extinction of the organ-pipe Montastraea occurred after more than 500,000 years of dominance in the shallow-water reef habitat of Barbados. Extinction resulted in a morphological shift of the columnar Montastraea lineage from thick to thin columns in modern reef environments. Pleistocene colonies of the columnar morphotype sympatric with organ-pipe Montastraea showed greater column widths than those in allopatry. We subjected our data to a number of criteria for interpreting the morphological shift as character release following lifting of competitive pressure after extinction. The morphological differences do not appear to be due either to chance or to physical properties of the marine environment. Differential local extinction and recolonization of four members of the species complex did not occur on Barbados, so that the species coexisted and appear to have coevolved between more than 600,000 and 82,000 years ago. The morphological shift is related to coral growth form and growth rate, and thus reflects the acquisition of a primary resource in corals-light. Character release occurred at the same oceanic Caribbean island (Barbados) where environments have fluctuated with similar variance throughout the period of coexistence. Not only has competition among living members of the Montastraea "annularis" species complex been convincingly demonstrated, but trends in relative abundance among fossil members of the species complex strongly suggest that a competitive hierarchy was operating during their Pleistocene coexistence on Barbados. We also observed an ecological analogue to character release on another Caribbean island, Curaçao. The distribution and abundance of living columnar M. annularis s.s. and massive M. faveolata from the leeward reef crest in Curaçao is greater now than in the Pleistocene, when organ-pipe Montastraea dominated this shallow-water reef habitat. Extinction of the faster growing, shallow-water organ-pipe Montastraea resulted in higher abundance of the columnar Montastraea lineage in shallow-water habitats, where it shifted its morphology to one adapted to high light levels. The species extinction released surviving lineages from a competitive network that had resulted in lower rank abundance in the Pleistocene community and enhanced abundance of both columnar M. annularis s.s. and M. faveolata in modern communities. Full validation of our interpretation of character release must await experiments that demonstrate whether phenotypic differences between populations have a genetic basis. However, we believe the results of this study point to the important, yet heretofore neglected, role that biological interactions have played in the evolution of closely related reef coral species.

]]> John M. Pandolfi et al. http://ir.uiowa.edu/geog_pubs/444 http://ir.uiowa.edu/geog_pubs/444 Tue, 13 Sep 2011 19:48:17 PDT Estimates of species diversity on coral reefs are extremely high, yet hidden biological diversity makes even these, underestimates. The morphological complexity in the Caribbean reef coral Montastraea 'annularis' was originally interpreted as a single species because colony growth form was highly correlated with depth distribution from the coral reefs surrounding Carrie Bow Cay in Belize. This 'species' has since been re-interpreted from other Caribbean reefs as representing at least 3 separate species based on morphometric, genetic, reproductive, and ecological differences. We revisited the shallow water coral reefs in the Carrie Bow Cay region to test whether the 3 species could be recognized, and if so, what their ecological distribution might be. We have found that the 3 recently described species of the Montastraea 'annularis' species complex can be readily identified using both colony forms observed in the field and morphometric analyses of the corallite wall, and that their abundance distributions vary significantly along depth gradients. Morphometric comparison with both colonies from Panama and results from transplantation experiments in Jamaica show consistent patterns in the morphological characters that differentiate species and growth forms and are useful in understanding the geographic, environmental, and genetic components of variability within the species complex. All 3 species have a broad depth distribution, but each species dominates in a preferred depth zone, suggesting a high degree of niche differentiation. Our results confirm the existence of hidden biological diversity in Caribbean reef corals and call for caution in future estimates of biological diversity on coral reefs.

]]> John M. Pandolfi et al. http://ir.uiowa.edu/geog_pubs/443 http://ir.uiowa.edu/geog_pubs/443 Tue, 13 Sep 2011 19:48:14 PDT R. H. Nehm et al. http://ir.uiowa.edu/geog_pubs/442 http://ir.uiowa.edu/geog_pubs/442 Tue, 13 Sep 2011 19:48:10 PDT B. D. Mishler et al. http://ir.uiowa.edu/geog_pubs/441 http://ir.uiowa.edu/geog_pubs/441 Tue, 13 Sep 2011 19:48:07 PDT A recently completed integrated stratigraphic study of the mixed sediments on the Caribbean side of the Isthmus of Panama (Limon, Costa Rica) has delineated two phases of reef proliferation that were controlled by changes in eustatic sea level. The older one, latest Early Pliocene, originated on siliciclastics of a prograded, shallow-marine shelf unit (Rio Banano Fm.), and corresponds with closure of the Central American isthmus. Although heavily stressed by siliciclastic input, the depositional conditions were supportive enough to stimulate origination of several modern reef-building corals. Most notably, the first occurrence of Acropora palmata is now placed significantly earlier at about approximately 3.6-4.0 Ma. The younger episode of reef development occurred around the Plio/Pleistocene boundary and is separated from the older reef unit by coarse-grained sands and gravel (Pueblo Nuevo Sands, Moin Fm.) associated with a marine regression. This younger reef sequence, also heavily sediment stressed, shows that most modern reef species were established by this time (1.9-1.6 Ma) and that accelerated extinction occurred between the two reef episodes. This sequence of reef development is coincident with several third-order sea level events, as recently documented from the Bahamas record. Relatively high sea levels in the Early Pliocene, a mid-Pliocene fall related to onset of northern hemisphere glaciation, and a highstand at the Plio/Pleistocene boundary are correlated respectively to the first reef phase, shallow marine sands, and the second reef event. Subsequent to the second reef phase, the Limon region was uplifted at least 50 m.

]]> D. F. McNeill et al. http://ir.uiowa.edu/geog_pubs/440 http://ir.uiowa.edu/geog_pubs/440 Tue, 13 Sep 2011 19:48:01 PDT Miocene and Pliocene reef tracts of the Caribbean were less common and smaller than older Oligocene and younger Pleistocene to Recent reefs. In the present study, samples from the Arroyo Bellaco exposures in the Cibao Valley, northern Dominican Republic were analyzed for Sr-87/Sr-86 to refine the age for a rare, well-developed Mio-Pliocene reef sequence. A mean age of 6.2 million years old (Ma) was determined for the reef. This age places the reef in the latter part of the late Miocene Messinian stage. The reef originated in a low-nutrient window at the end of a global cooling event and sea level lowstand, coincident with a period of decreased upwelling intensity from 6.2 to 5.8 Ma. Reef demise is attributed to a latest Miocene transgression and an associated pulse of marine siliciclastic deposition.

]]> K. L. Maier et al. http://ir.uiowa.edu/geog_pubs/439 http://ir.uiowa.edu/geog_pubs/439 Tue, 13 Sep 2011 19:47:58 PDT Marina A. Mackenzie et al. http://ir.uiowa.edu/geog_pubs/438 http://ir.uiowa.edu/geog_pubs/438 Tue, 13 Sep 2011 19:47:53 PDT An assemblage of planktonic foraminifera is described from 125 samples taken from the Cercado, Gurabo, and Mao Formations in the Cibao Valley, northern Dominican Republic. The primary objectives of this study are to establish a biochronologic model for the late Neogene of the Dominican Republic and to examine sea surface conditions within the Cibao Basin during this interval. The Cercado Formation is loosely confined to Zones N17 and N18 (similar to 7.0-5.9 Ma). The Gurabo Formation spans Zones N18 and N19 (similar to 5.9-4.5 Ma). The Mao Formation is placed in Zone N19 (similar to 4.5-3.6 Ma). Changes in the relative abundances of indicator species are used to reconstruct sea surface conditions within the basin. Increasing relative abundances of Globigerinoides sacculifer and Globigerinoides ruber, in conjunction with a decreasing relative abundance of Globigerina bulloides, suggests the onset of increasing sea surface temperature and salinity in conjunction with diminishing primary productivity at similar to 6.0 Ma. Abrupt increases in the relative abundances of G. sacculifer and G. ruber at similar to 4.8 Ma suggest a major increase in sea surface temperature and salinity in the early Pliocene. The most likely mechanism for these changes is isolation of the Caribbean Ocean through progressive restriction of Pacific-Caribbean transfer via the Central American Seaway. Periods of high productivity associated with upwelling events are recorded in the upper Cercado Formation (similar to 6.1 Ma) and in the middle Mao Formation (similar to 4.2 Ma) by spikes in G. bulloides and Neogloboquadrina spp. respectively. The timing of major increases in sea surface salinity and temperature as well as decreasing productivity (similar to 4.8 Ma) and periods of upwelling (similar to 6.1 and 4.2 Ma) in the Cibao Basin generally corroborate previously suggested Caribbean oceanographic changes related to the uplift of Panama. Changes in sea surface conditions depicted by paleobiogeographic distributions in the Cibao Basin suggest that shoaling along the Isthmus of Panama had implications in a shallow Caribbean basin as early as 6.0 Ma. Major paleobiologic changes between similar to 4.8 and 4.2 Ma likely represent the period of final closure of the CAS and a nearly complete disconnection between Pacific and Caribbean water masses. This study illustrates the use of planktonic foraminifera in establishing some paleoceanographic conditions (salinity, temperature, productivity and upwelling) within a shallow water basin, outlining the connection between regional and localized oceanographic changes. (C) 2008 Elsevier B.V. All rights reserved.

]]> B. D. Lutz et al. http://ir.uiowa.edu/geog_pubs/437 http://ir.uiowa.edu/geog_pubs/437 Tue, 13 Sep 2011 19:47:49 PDT Porites sverdrupi has long been considered to be an ecotype of the more abundant and widespread species P. panamensis, but multivariate comparisons of corallite characteristics indicate that P. sverdrupi is morphologically distinct and thus represents a valid species. In these analyses, linear measurements and counts were made on 72 colonies of the two species (53 of P. panamensis and 19 of P. sverdrupi), and analyzed multivariately using canonical discriminant analysis. Generally, corallite characteristics of P. sverdrupi are larger in size than P. panamensis. Important characters in the discriminant function (e.g., number of bifurcate septa, wall thickness, and dorsal septum length) have not been recognized in previous studies of Porites in either the Indo-Pacific or Atlantic regions as being significant in distinguishing among poritid species. In addition to corallite characteristics, P. sverdrupi is unique in its ecological habit, colony form, and geographic distribution.

]]> R. A. Lopez-Perez et al. http://ir.uiowa.edu/geog_pubs/436 http://ir.uiowa.edu/geog_pubs/436 Tue, 13 Sep 2011 19:47:45 PDT Bernard Lathuiliere et al. http://ir.uiowa.edu/geog_pubs/435 http://ir.uiowa.edu/geog_pubs/435 Tue, 13 Sep 2011 19:47:40 PDT Scleractinian reef-coral species display high phenotypic plasticity in skeletal morphology. Understanding environmental and physiologic controls on this variation is essential to explaining the distribution and abundance of coral species as well as understanding their susceptibility to pollution and global climate change. Here we assess phenotypic plasticity in the corallite morphology of genetically determined colonies of Montastraea annularis s.s. (Ellis and Solander, 1786) by analyzing the three-dimensional morphology of calical surfaces and the two-dimensional corallite morphology represented in transverse thin sections. Samples were collected along gradients of seawater depth and coastal influence on the island of Curacao, Netherlands Antilles, and additionally compared to M. annularis and two closely related species, M. franksi (Gregory, 1895), and M. faveolata (Ellis and Solander, 1786), collected from Panama. Significant phenotypic plasticity was found between seawater depths and localities of Curacao, as well as between the two geographic regions. Morphologic characters associated with calical surfaces were significantly more plastic than characters preserved in transverse thin sections. While characters preserved in thin section were more successful at classifying the three closely related species, characters associated with calical surfaces provide a basis for interpreting the adaptive significance of the observed differences between these three species.

]]> James S. Klaus et al. http://ir.uiowa.edu/geog_pubs/434 http://ir.uiowa.edu/geog_pubs/434 Tue, 13 Sep 2011 19:47:37 PDT The extent to which origination and selective extinction influenced the structure and dynamics of Caribbean coral reef communities is evaluated by comparing the diversity and distributional patterns of coral species in two Dominican Republic reef sequences prior to and following late Cenozoic Caribbean faunal turnover. The two sequences consist of the late Miocene Arroyo Bellaco reef of the Cibao Valley, northern Dominican Republic, and the late Pleistocene 125-ka reef terrace of the southern Dominican Republic. Samples were collected along 20-meter transects (10 Miocene, 10 Pleistocene); species identifications were made using standard sets of characters and morphometrics. In particular, species of Montastraea annularis-like corals were distinguished within each sequence using a 2-dimensional landmark technique involving average linkage cluster analysis, discriminant analyses, and non-parametric tests. Four Miocene and four Pleistocene species were recognized. Subsequent community analysis was two-fold: (1) whole coral community, and 2) distribution of the Montastraea "annularis" complex. For the whole coral community, occurrence matrices of transect samples, assembled separately for Miocene (35 species) and Pleistocene (20 species) reef sequences, were analyzed using average linkage cluster analysis, multidimensional scaling, similarity percentages, one-way analysis of similarity, and non-parametric tests for independent samples (Mann-Whitney U, Kruskal-Wallis H). Three assemblages were recognized within each sequence, which correspond with back-reef, reef-crest, and reef-front facies defined independently on the basis of sedimentological criteria. Comparisons between the two sequences suggest that widespread species (ecological generalists) are more common within the Pleistocene sequence than within the Miocene sequence. Fifteen of thirty-five (43%) Miocene species occur in single reef facies compared to five of twenty (25%) Pleistocene species. Of the five species found within both reef sequences, four occur in all three of the identified Miocene reef facies; one was found in two of these three facies. For the distribution of the Montastraea "annularis" complex, samples of M. annularis-like corals were examined to determine if distributional patterns of species within the complex were similar before and after faunal turnover. The four M. annularis-like corals identified within each reef sequence had markedly different distributional patterns. During the late Miocene, cohabitation within reef facies was low. Following faunal turnover, cohabitation within facies increased. This result further suggests that niche partitioning may have been reduced on post-turnover reefs. The results support the hypothesis of selective extinction of ecologically restricted species during Plio-Pleistocene turnover. Despite the prolonged and continuous nature of faunal turnover, reef community change involved more than species replacement-the underlying structure of reef communities and their biological interactions were fundamentally altered.

]]> James S. Klaus et al. http://ir.uiowa.edu/geog_pubs/433 http://ir.uiowa.edu/geog_pubs/433 Tue, 13 Sep 2011 19:47:33 PDT We analyze a new compilation of Neogene to Recent (22-0 Ma) Caribbean coral occurrences to determine how ecological and life history traits at the population level affect long-term evolutionary patterns. The compilation consists of occurrences of 175 species and 49 genera in one continuous (> 5 m.y.) sequence and 22 scattered sites across the Caribbean region. Previous study of evolutionary rates using these data has shown that both extinction and origination were accelerated between 4 and 1 Ma, resulting in large-scale faunal turnover. Categories for three morphological and two reproductive variables (colony size, colony shape, and corallite size; and sex, and mode of embryonic development; respectively) are assigned to each species in the compilation. Comparisons of the ecological variables with evolutionary rates using randomization procedures and modified analysis of variance show that only colony size was strongly related to rates of extinction and origination during either normal background times or times of accelerated extinction. Extinction rates were lower in species with large colonies, because species with small massive colonies tend to live in small, short-lived populations with highly fluctuating recruitment rates. During turnover, extinction rates increased disproportionately in species with small colonies. Orig-ination rates are found to be less related to ecological variables, although species with small massive colonies originated at higher rates prior to turnover. Accelerated turnover may have therefore involved an increase in local population extinction rates that caused increased rates of both species extinction and origination across the entire fauna. Since extinction rates accelerated disproportionately with respect to colony size, the overall result was a relative increase in species with large colonies. After severe disturbance, one might expect that populations of species with large colonies and high rates of fragmentation would be more likely to escape extinction, because of larger population sizes, longer generation times, and more constant rates of population increase. The modern Caribbean reef-coral fauna is therefore structured by large, long-lived colonies that are robust to regional environmental change. Many of the very taxa that allowed reef communities to escape collapse in the past are declining today in response to anthropogenic disturbances, suggesting that Caribbean reef communities may be less resilient in the future in response to ongoing environmental perturbations.

]]> Kenneth G. Johnson et al. http://ir.uiowa.edu/geog_pubs/432 http://ir.uiowa.edu/geog_pubs/432 Tue, 13 Sep 2011 19:47:28 PDT Kenneth G. Johnson et al. http://ir.uiowa.edu/geog_pubs/431 http://ir.uiowa.edu/geog_pubs/431 Tue, 13 Sep 2011 19:47:24 PDT Jeremy B. Jackson et al. http://ir.uiowa.edu/geog_pubs/430 http://ir.uiowa.edu/geog_pubs/430 Tue, 13 Sep 2011 19:47:21 PDT Recent work suggests the Montastraea annularis species complex consists of at least three species, which can be distinguished qualitatively in the field using features related to colony growth (e.g. overall growth form. bumpiness, growth along the colony edge). However, when whole colonies are not available and surfaces are eroded, identification becomes problematic when relying on such characteristics. Characters based on internal skeletal structures are less prone to loss due to taphonomic processes. Previous work has shown that internal corallite architectural features measured in transverse thin sections can be used to distinguish species. To determine whether internal colony-level features measured on X-radiographs can be used. eight characters related to corallite budding and accretionary growth were measured on specimens representing three modern members of the M. annularis species complex (M. annularis, M. flaveolata and M. franksi), as well as two fossil forms (columnar and organ-pipe). All eight characters showed significant differences among species. Discriminant function analysis using seven of these characters resulted in distinct species groupings In canonical scores plots and a 100% classification success for specimens from Panama. These results suggest that measurements made on X-radiographs provide a useful tool for quantitatively distinguishing members of the M. annularis complex as well as between other massive reef corals.

]]> M. Holcomb et al.