Zoogeography of Vietnamese primates

Based on geographic complementarity of congeneric taxa, the 22 species or well-defined subspecies of primates that inhabit Vietnam may be allocated to nine zoogeographic groups (lorises, two; macaques, three; langurs, three; gibbons, one). Analysis of group distributions reveals two major patterns: (1) four of the six non-macaque groups are essentially restricted to the eastern part of the Indochinese Peninsula, east of the Mekong River; and (2) species and subspecies in seven of the nine groups reach their northern or southern limits of distribution in central Vietnam, at 14–17‡N. The first pattern suggests that the Mekong River has been an important barrier to westward dispersal of nonmacaque primates in continental Southeast Asia. The second pattern suggests that a Zoogeographic barrier formerly extended east and west across Vietnam at ca. 14–17‡N.     

Effect of river size on Amazonian primate community structure: A biogeographic analysis using updated taxonomic assessments

The mechanisms that underlie the diversification of Neotropical primates remain contested. One mechanism that has found support is the riverine barrier hypothesis (RBH), which postulates that large rivers impede gene flow between populations on opposite riverbanks and promote allopatric speciation. Ayres and Clutton-Brock (1992) demonstrated that larger Amazonian rivers acted as barriers, delineating the distribution limits of primate species. However, profound changes in taxonomy and species concepts have led to the proliferation of Neotropical primate taxa, which may have reduced support for their results. Using the most recent taxonomic assessments and distribution maps, we tested the effect of increasing river size on the similarity of opposite riverbank primate communities in the Amazon. First, we conducted a literature review of primate taxonomy and developed a comprehensive spatial database, then applied geographical information system to query mapped primate ranges against the riverine geography of the Amazon watershed to produce a similarity index for opposite riverbank communities. Finally, we ran models to test how measures of river size predicted levels of similarity. We found that, almost without exception, similarity scores were lower than scores from Ayres and Clutton-Brock (1992) for the same rivers. Our model showed a significant negative relationship between streamflow and similarity in all tests, and found river width significant for the segmented Amazon, but not for multiple Amazon watershed rivers. Our results support the RBH insofar as they provide evidence for the prediction that rivers with higher streamflow act as more substantial barriers to dispersal, and accordingly exhibit greater variation in community composition between riverbanks.     

Size variation facilitates population divergence but does not explain it all: an example study from a widespread African monkey

Subspecific variation is widespread in vertebrates. Within Africa, several mammals have extensive geographic distributions with attendant morphological, ecological, and behavioural variations, which are often used to demarcate subspecies. In the present study, we use a primate species, the vervet monkey, Cercopithecus aethiops, as a case study for intraspecific divergence in widespread mammals, assessed through hard tissue morphology. We examine intraspecific differences in size, shape, and non‐allometric shape from a taxonomic perspective, and discuss the macroevolutionary implications of findings from microevolutionary analyses of geographic variation. A geometric morphometric approach was used, employing 86 three‐dimensional landmarks of almost 300 provenanced crania. Many of the taxonomic differences in skull morphology between vervet populations appear to be related to geographic proximity, with subspecies at opposite extremes of a west‐to‐east axis showing greatest divergence, and populations from central and south Africa being somewhat intermediate. The classification rate from discriminant analyses was lower than that observed in other African primate radiations, including guenons as a whole and red colobus. Nonetheless, taxonomic differences in shape were significant and not simply related to either geography or size. Thus, although shifts in size may be an important first step in adaptation and diversification, with size responding more quickly than shape to environmental change, the six vervet taxa currently recognized (either as species or subspecies) are not simply allometrically scaled versions of one another and are probably best viewed as subspecies. Holding allometry constant when examining inter‐population differences in shape may thus help to reveal the early stages of evolutionary divergence. The vervet case study presented here hence has relevance for future studies examining intraspecific differentiation in other large mammals, particularly through the methods used to identify small but biologically meaningful divergence, with attendant implications for conservation planning. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 823–843.     

Rarity in the tropics: biogeography and macroecology of the primates

Aim To describe rarity and elucidate its biology in a tropical mammalian order, the Primates. Location Africa, Central and South America, Asia, Madagascar. Methods A review of the literature, with some additional analyses using data from the literature. A variety of definitions of rarity are used in order to describe it and to investigate its biology by correlating the degree of rarity with a variety of biological traits indicative of resource use (e.g. size of annual home range), reproductive rate (e.g. birth interval)and specialization (e.g. number of habitat types used). Results Few primate taxa occur outside the tropics, and most taxa are rare (small geographical range size or latitudinal extent, low density or both). Latitudinal extent is narrower at lower latitudes in Africa and Asia, but the potential resultant packing of taxa appears not to explain the taxonomic diversity gradient. Whilst primate species do not show the common, positive density by range size relationship, primate genera show a significant shallow slope, and primate families/subfamilies a strongly positive slope. Rare taxa are specialized, but neither use more resources nor breed more slowly than common taxa. The correlation of rarity and specialization is via geographical range: taxa with small ranges, or small ranges for their density, are specialized, but not taxa at low density. Common taxa are generalized because they consist of more differently specialized subtaxa, not because each subtaxon is generalized. Main conclusions Most primate taxa are rare, in which case most are presumably likely to go extinct. Rare primates are specialized, but do not necessarily use more resources, nor breed more slowly. Specialization as an explanation for rarity appears to work via constriction of range size, not of density. Common primates might be common (large range size) not because subtaxa or individuals are generalized, but because they are composed of more subtaxa. A consequence could be that persistence of even common taxa will depend on conservation of several populations scattered across the taxon's geographical range.     

Distribution and Diversity of Primates in Guyana: Species-Area Relationships and Riverine Barriers

Species-area relationships predict that there is a positive relationship between the number of species and the size of an area. It has been suggested that species richness will covary with area because larger areas have a greater diversity of habitats. Moreover, habitat diversity may operate in conjunction with riverine barriers to influence primate biogeography. Few studies have determined if and how these hypotheses relate to primate diversity in Guyana. To test these biogeographic hypotheses, I used data from 1,725 km of primate surveys I conducted in Guyana. I estimated geographic ranges for each of the 8 primate species via a GIS system. Geographic range size is a major determinant of the number of sightings of the 8 primate species. Primate species diversity is strongly negatively correlated with the number of rivers crossed moving in a clockwise pattern from eastern to NW Guyana. Interfluvial and habitat areas influence primate species diversity in Guyana. However, my data on primate biogeography in Guyana do not support the hypothesis that habitat diversity within the interfluvial areas effects primate diversity. Although the species-area relationship is considered the closest thing to a rule in ecology, researchers should be wary of too readily applying and accepting the model at all scales in biogeographic studies.     

Nonconvergence in the evolution of primate life history and socio-ecology

The goal of this study was to investigate the extent of convergence in four basic life history and socio-ecological traits among the primates of Africa, Asia, South America and Madagascar. The convergence hypothesis predicts that similar abiotic conditions should result in similar adaptations in independent taxa. Because primates offer a unique opportunity among mammals to examine adaptations of independent groups to tropical environments, we collected information on body mass, activity pattern, diet and group size from all genera for quantitative tests of this hypothesis. We revealed a number of qualitative and quantitative differences among the four primate groups, indicating a lack of convergence in these basic aspects of life history and socio-ecology. Our analyses demonstrated that New World primates are on average significantly smaller than primates in other regions and characterized by a lack of species larger than about 10 kg. Madagascar harbours significantly more nocturnal species than the other regions and is home to all but one of the primates with irregular bursts of activity. Asia is the only region with strictly faunivorous primates, but lacks primarily gummivorous ones. The Neotropics are characterized by the absence of primarily folivorous primates. Solitary species are not represented in the New World, whereas solitary and pair-living species make up the majority of Malagasy primates. Lemurs live in significantly smaller groups than other primates, even after controlling for differences in body size. The lack of convergence among the major primate groups is neither primarily due to phylogenetic constraints as a result of founder effects, nor can it be sufficiently explained as a passive consequence of body size differences. However, because the role of adaptive forces, such as interspecific competition, predation or phenology in shaping the observed differences is largely unexplored, we conclude that it is premature to discard the convergence hypothesis without further tests.     

Sampling Effort in Neotropical Primate Diet Studies: Collective Gains and Underlying Geographic and Taxonomic Biases

Primates are among the most observable and best studied mammalian orders, yet the distribution of sampling effort by primatologists has inevitably concentrated on a few genera and a limited number of study sites. We present the first systematic review of sampling effort and associated biases in wild primate field research, focusing on dietary studies across the Neotropics. Our literature review of all 24 neotropical primate ecospecies spans 42 years (1969–2011) and covers 290 dietary studies at 164 study sites across 17 countries. We use a standardized measure of sampling effort to assimilate data sets derived from multiple methodologies and attempt to understand the distribution of effort (total equivalent to 193,804 h) using geographic variables and primate species traits. Results indicate that there are both geographic and taxonomic biases, with sampling effort generally skewed towards large-bodied species occupying large geographic ranges, and concentrated at a select few primatology research hubs. We also note that full primate assemblages at any given study site are rarely investigated. Our assessment thus reveals severely undersampled primate taxa and geographic regions that must be considered in future research. Current biases could be ameliorated by deliberately targeting poorly studied genera anywhere in their geographic distribution, well-studied genera in poorly studied regions, and striving to study multiple sympatric taxa within a single site. Although continued inequalities in sampling effort are probably inevitable, this study shows that this need not inhibit successful compilations and meta-analyses, provided that adequate data on feeding records and sampling effort can be made available.     

Biogeography of the Tropical Eastern Pacific: distribution and phylogeny of chaenopsid fishes

The Tropical Eastern Pacific Biogeographic Region (TEP) is delimited by steep thermal gradients to the north and south, by a wide expanse of open ocean (the East Pacific Barrier) to the west, and by the Central American land mass to the east. Four provinces within the TEP have been recognized based on the distribution of rocky shore fishes and marine invertebrates: the Cortez, Mexican, Panamic, and Galápagos Provinces. For rocky shore fishes, hypothesized barriers between these provinces are areas lacking rocky outcroppings, specifically the Central American Gap between the Panamic and Mexican Provinces, the Sinaloan Gap between the Mexican and Cortez Provinces, and the Pelagic Gap between the mainland and the Islas Galápagos. The occurrence of 33 chaenopsid fish species within these provinces, as well as other oceanic islands or archipelagos in the TEP (Isla de Malpelo, Isla del Coco, and Islas Revillagigedo) were tallied based on literature records and observations of museum specimens. Chaenopsid distributions within the TEP support these hypothesized provinces and their intervening gaps. Twenty‐one species (64% of the TEP chaenopsid fauna) are restricted to a single mainland province or one of the oceanic islands or archipelagos. Of the mainland provinces, the Cortez and Panamic exhibit similar levels of endemism (50%), but the Mexican Province has only one endemic (10%). Of the remaining chaenopsids in the Mexican Province, three are widespread, occurring in all three mainland provinces, four are shared only with the Cortez Province, and two are shared only with the Panamic Province. Within the TEP, the Pelagic Gap is the most effective (crossed by only 3 of 33 species adjacent to it), followed by the Central American Gap (crossed by 5 of 21 species), and the Sinaloan Gap (crossed by 7 of 17 species). Only one species, Chaenopsis alepidota, which is found off southern California and in the Cortez Province, crosses a barrier delimiting the TEP. Species‐level phylogenetic hypotheses for the Chaenopsidae imply exclusively allopatric speciation for these fishes in the TEP. Of the barriers delimiting the TEP, the most important in the recent evolution of chaenopsids is the Isthmian Barrier which is implicated in six speciation events. Within the TEP, the Central American Gap and Sinaloan Gap are each implicated in three speciation events, while the Pelagic Gap is implicated in three speciation events of island endemics from mainland populations and one inter‐island speciation event.     

Biogeography of central African forests: Determinants,ongoing threats and conservation priorities of mammal assemblages

Aim

Central Africa shelters diverse and iconic megafauna, which is threatened by climate and land-use changes and increased hunting-induced defaunation. Though crucial for coordinating regional conservation actions, how species assemblages are spatially structured remains poorly understood. This study aims to fill this knowledge gap for mammals across central African forests.

Location

Tropical moist forests from Nigeria to the Albertine Rift.

Methods

An extensive compilation of forest-dwelling mammal species lists was made from wildlife and bushmeat-related surveys across central Africa. A beta-diversity approach enabling the clustering of surveys composed of similar species was implemented to identify and delimit zoogeographic districts, separately for three well-documented mammal orders: carnivores, primates and artiodactyls. Random forest classification models were then used to identify the environmental determinants of the district's distribution and to produce a continuous zoogeographic map (and associated uncertainties) critical to assess the conservation status of each district and their ongoing threats.

Results

While carnivores do not present a clear spatial structure within central African forests, our findings highlight the structuring role of rivers on both primate and artiodactyl assemblages' distributions. We retained eight and six spatially congruent districts for primates and artiodactyls, respectively. These districts were shaped by the Ubangi-Congo River system, and the Cross and Sanaga Rivers, with a secondary role of insularity and precipitation identified for primates. Highly threatened districts were highlighted, especially in Nigeria and in the Democratic Republic of Congo, the latter including vast areas that are understudied and poorly represented in the protected area network.

Main Conclusions

Beyond refining our understanding of the diversity and uniqueness of mammalian assemblages across central African forests, our map of zoogeographic districts has far-reaching implications for the conservation of highly threatened taxa, allowing to target species and areas of interest for further sampling, conservation and rewilding efforts.     

Biogeographic and Ecological Forces Responsible for Speciation in Ateles

We used the results of phylogenetic analyses of relationships among spider monkeys (Ateles) based on mitochondrial and nuclear DNA to investigate questions of their evolutionary origins and speciation mechanisms. We employed the concept of a local molecular clock to date nodes of interest (corresponding to hypothesized species and subspecies) in the various phylograms for comparison to hypothesized biogeographical events that might have affected speciation. We considered various mechanisms—Pleistocene refuge formation, riverine barriers, geological fluctuations, and ecological changes associated with these mechanisms—for their contribution to speciation in Ateles. Most speciation among the various species of Ateles occurred during the middle to late Pliocene, suggesting that Pleistocene refuge formation was not a key speciation mechanism. However, it is likely that the genetic structure of populations of Ateles was modified to some extent by refuge formation. Additionally, riverine barriers do not seem to interrupt gene flow significantly among Ateles. No river formed a barrier among species of Ateles, with the exception of the lower Amazon and possibly some of the black-water rivers draining the Guianan highlands. Large-scale geographic changes associated with the continued rise of the eastern and western cordilleras of the northern Andes and associated changes in habitat were the most important causes of speciation in Ateles. The various factors that modify genetic structure in Ateles are important to consider in order to protect endangered primate genera in the Neotropics.     

Distribution of diurnal primate species in Togo and Bénin

The Dahomey Gap, a strip of forest-savanna mosaic that interrupts the lowland rainforests of West Africa, is supposed to have acted as a natural barrier to the distribution of forest-dwelling mammals. However, few thorough mammal surveys have been conducted in this region. This study intended to gather distributional data and help clarify the distribution limits of diurnal primates occurring within this 'Gap'. Southern Togo and Bénin were surveyed between June and November 2003. The surveys consisted of interviews with hunters and guards from parks and reserves, and walking surveys of forests. As a result, seven diurnal primate species are listed for Togo and Bénin.     

Cross-Species Pathogen Transmission and Disease Emergence in Primates

Many of the most virulent emerging infectious diseases in humans, e.g., AIDS and Ebola, are zoonotic, having shifted from wildlife populations. Critical questions for predicting disease emergence are: (1) what determines when and where a disease will first cross from one species to another, and (2) which factors facilitate emergence after a successful host shift. In wild primates, infectious diseases most often are shared between species that are closely related and inhabit the same geographic region. Therefore, humans may be most vulnerable to diseases from the great apes, which include chimpanzees and gorillas, because these species represent our closest relatives. Geographic overlap may provide the opportunity for cross-species transmission, but successful infection and establishment will be determined by the biology of both the host and pathogen. We extrapolate the evolutionary relationship between pathogen sharing and divergence time between primate species to generate “hotspot” maps, highlighting regions where the risk of disease transfer between wild primates and from wild primates to humans is greatest. We find that central Africa and Amazonia are hotspots for cross-species transmission events between wild primates, due to a high diversity of closely related primate species. Hotspots of host shifts to humans will be most likely in the forests of central and west Africa, where humans come into frequent contact with their wild primate relatives. These areas also are likely to sustain a novel epidemic due to their rapidly growing human populations, close proximity to apes, and population centers with high density and contact rates among individuals.     

Modern classification and distribution of the family Issidae Spinola (Homoptera,Auchenorrhyncha: Fulgoroidea)

The modern classification of the family Issidae s. str. is presented according to which the family consists of 3 tribes: Issini, Hemisphaeriini, and Parahiraciini and comprises a total of 994 species and subspecies in 159 genera. The largest tribe, Issini, is distributed worldwide and comprises 129 genera with 755 species and subspecies. The tribes Hemisphaeriini and Parahiraciini are much smaller and mostly distributed in the Indo-Malayan Realm with some taxa also present in the Eastern Palaearctic and the Oceania. The tribe Hemisphaeriini consists of 15 genera with 187 species and subspecies while Parahiraciini includes 14 genera with 38 species. The Palaearctic and Indo-Malayan Realms have the richest faunas of Issidae. In contrast, Equatorial Africa has a very poor fauna of the family, whereas the Australian fauna is still almost undescribed. Chimetopon camerunensis Schmidt is recorded for the first time from Central African Republic and Gabon, and Sarima erythrocyclos Fennah, from Taveuni Island (Fiji).     

Biogeography of lemurs in the humid forests of Madagascar: the role of elevational distribution and rivers

Aim Elucidation of the influence of river systems on the distribution of lemurs. Location Humid forests of Madagascar. Methods We review the elevational distribution of Malagasy lemurs to address hypotheses of the role of rivers as physical barriers. Main conclusions Rivers are barriers for some species. However, several lemurs have altitudinal ranges that are higher than the headwaters of a given river, and in such cases these species are able to disperse across the source.     

Mitochondrial phylogeny of African wood mice, genus Hylomyscus (Rodentia, Muridae): implications for their taxonomy and biogeography

This paper investigates the usefulness of two mitochondrial genes (16S rRNA and cytochrome b) to solve taxonomical difficulties within the genus Hylomyscus and to infer its evolutionary history. Both genes proved to be suitable molecular markers for diagnosis of Hylomyscus species. Nevertheless the resolving powers of these two genes differ, and with both markers (either analyzed singly or in combination), some nodes remain unresolved. This is probably related to the fact that the species emerged during a rapid diversification event that occurred 2-6 Myr ago (4-5 Myr ago for most divergence events). Our molecular data support the recognition of an "aeta" group, while the "alleni" and "parvus" groups are not fully supported. Based on tree topology and genetic divergence, two taxa generally recognized as subspecies should be elevated at the species level (H. simus and H. cf kaimosae). H. stella populations exhibit ancient haplotype segregation that may represent currently unrecognized allopatric species. The existence of cryptic species within H. parvus is questioned. Finally, three potentially new species may occur in West Central Africa. The Congo and Oubangui Rivers, as well as the Volta and Niger Rivers and/or the Dahomey gap could have formed effective barriers to Hylomyscus species dispersal, favoring their speciation in allopatry. The pronounced shifts in African climate during the late Pliocene and Miocene, which resulted in major changes in the distribution and composition of the vegetation, could have promoted speciation within the genus (refuge theory). Future reports should focus on the geographic distribution of Hylomyscus species in order to get a better understanding of the evolutionary history of the genus.     

Regional environmental breadth predicts geographic range and longevity in fossil marine genera

Background

Geographic range is a good indicator of extinction susceptibility in fossil marine species and higher taxa. The widely-recognized positive correlation between geographic range and taxonomic duration is typically attributed to either accumulating geographic range with age or an extinction buffering effect, whereby cosmopolitan taxa persist longer because they are reintroduced by dispersal from remote source populations after local extinction. The former hypothesis predicts that all taxa within a region should have equal probabilities of extinction regardless of global distributions while the latter predicts that cosmopolitan genera will have greater survivorship within a region than endemics within the same region. Here we test the assumption that all taxa within a region have equal likelihoods of extinction.

Methodology/Principal Findings

We use North American and European occurrences of marine genera from the Paleobiology Database and the areal extent of marine sedimentary cover in North America to show that endemic and cosmopolitan fossil marine genera have significantly different range-duration relationships and that broad geographic range and longevity are both predicted by regional environmental breadth. Specifically, genera that occur outside of the focal region are significantly longer lived and have larger geographic ranges and environmental breadths within the focal region than do their endemic counterparts, even after controlling for differences in sampling intensity. Analyses of the number of paleoenvironmental zones occupied by endemic and cosmopolitan genera suggest that the number of paleoenvironmental zones occupied is a key factor of geographic range that promotes genus survivorship.

Conclusions/Significance

Wide environmental tolerances within a single region predict both broad geographic range and increased longevity in marine genera over evolutionary time. This result provides a specific driving mechanism for the spatial and temporal distributions of marine genera at regional and global scales and is consistent with the niche-breadth hypothesis operating on macroevolutionary timescales.     

Taxonomy and conservation of Vietnam's primates: a review

Vietnam has the highest number of primate taxa overall (24-27) and the highest number of globally threatened primate taxa (minimum 20) in Mainland Southeast Asia. Conservation management of these species depends in part on resolving taxonomic uncertainties, which remain numerous among the Asian primates. Recent research on genetic, morphological, and acoustic diversity in Vietnam's primates has clarified some of these uncertainties, although a number of significant classification issues still remain. Herein, we summarize and compare the major current taxonomic classifications of Vietnam's primates, discuss recent advances in the context of these taxonomies, and suggest key areas for additional research to best inform conservation efforts in a region crucial to global primate diversity. Among the most important next steps for the conservation of Vietnam's primates is a new consensus list of Asian primates that resolves current differences between major taxonomies, incorporates recent research advances, and recognizes units of diversity at scales below the species-level, whether termed populations, morphs, or subspecies. Priority should be placed on recognizing distinct populations, regardless of the species concept in use, in order to foster the evolutionary processes necessary for primate populations to cope with inevitable environmental changes. The long-term conservation of Vietnam's primates depends not only on an accepted and accurate taxonomy but also on funding for on-the-ground conservation activities, including training, and the continued dedication and leadership of Vietnamese researchers and managers.     

Climatic and geographic barriers drive distributional patterns of bird phenotypes within peninsular India

Modern phylogenetic data provide unparalleled ability to test biogeographic paradigms, often suggested by differences in species distribution patterns. However, such approaches have been applied less at regional scales, particularly in Asia. In the absence of such data, we examine if concordance of distributional patterns for phenotypes (subspecies) suggest potential biogeographic barriers for birds in peninsular India. Specifically, we examine climatic and physical factors that might limit phenotype distributions in this region. Various physical, vegetation and climatic barriers were demarcated to identify potential biogeographic units within peninsular India. We then collated occurrence of endemic or disjunctly distributed species and subspecies within these units using published range maps. We also quantified turnover between potential units, allowing us to identify significant biogeographic barriers. Three time‐step climate data (Last Glacial Maxima, mid‐Holocene and present) enabled us to examine differences between these potential biogeographic regions through time. The Palk Straits, followed by the Goa Gap (～ 16°N) and the Godavari River emerged as the major barriers in this region. The Palk Straits and Godavari are physical barriers while Goa Gap appears to be a climate‐mediated ecological divide. Mountain barriers like the Palghat Gap are not the most significant barriers as previously thought. Climatically intermediate regions appeared unstable in the past and showed inconsistent affinities to different geographic units across families. We suggest that relative climatic stability of the wet regions of the southern western Ghats could be responsible for high subspecies endemism here. Our approach provides hypotheses that can be tested with comparative multi‐species phylogeographic data in the future.     

The role of physical barriers in the location of avian suture zones in the Guiana Shield, northern Amazonia

Suture zones represent natural forums in which to examine the role of geography and ecology in the speciation process. Here, we conduct a comparative analysis designed to investigate the location of avian phylogeographic breaks and contact zones in the Guiana Shield, northern Amazonia. We use distributional and genetic data from 78 pairs of avian taxa to address whether phylogeographic breaks and contact zones are associated with contemporary landscape features. Using spatially explicit statistical models, we found that phylogeographic breaks and contact zones are not randomly distributed throughout the landscape. In general, geographic breaks cluster along physical barriers (rivers, nonforested habitats, and small mountain ranges), whereas contact zones aggregate where these barriers either break down or are easier to overcome, such as around rivers' headwaters. Our results indicate that although major Amazonian rivers are often key determinants of taxon boundaries, the "riverine barrier effect" is a synergistic consequence of the wide lower reaches of some rivers, coupled with nonriverine landscape features at the headwaters. Our data suggest that ancestral refugia are not necessary to explain current distribution patterns and that pairs of codistributed taxa do not seem to be the result of simultaneous diversification processes.     

Fossil preservation and the stratigraphic ranges of taxa

The incompleteness of the fossil record hinders the inference of evolutionary rates and patterns. Here, we derive relationships among true taxonomic durations, preservation probability, and observed taxonomic ranges. We use these relationships to estimate original distributions of taxonomic durations, preservation probability, and completeness (proportion of taxa preserved), given only the observed ranges. No data on occurrences within the ranges of taxa are required. When preservation is random and the original distribution of durations is exponential, the inference of durations, preservability, and completeness is exact. However, reasonable approximations are possible given non-exponential duration distributions and temporal and taxonomic variation in preservability. Thus, the approaches we describe have great potential in studies of taphonomy, evolutionary rates and patterns, and genealogy. Analyses of Upper Cambrian-Lower Ordovician trilobite species, Paleozoic crinoid genera, Jurassic bivalve species, and Cenozoic mammal species yield the following results: (1) The preservation probability inferred from stratigraphic ranges alone agrees with that inferred from the analysis of stratigraphic gaps when data on the latter are available. (2) Whereas median durations based on simple tabulations of observed ranges are biased by stratigraphic resolution, our estimates of median duration, extinction rate, and completeness are not biased.(3) The shorter geologic ranges of mammalian species relative to those of bivalves cannot be attributed to a difference in preservation potential. However, we cannot rule out the contribution of taxonomic practice to this difference. (4) In the groups studied, completeness (proportion of species [trilobites, bivalves, mammals] or genera [crinoids] preserved) ranges from 60% to 90%. The higher estimates of completeness at smaller geographic scales support previous suggestions that the incompleteness of the fossil record reflects loss of fossiliferous rock more than failure of species to enter the fossil record in the first place.