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At least 379 records · Page 21Linked to original sources
PubMed2003

Historical contingency in the evolution of primate color vision.

Primates are unique among eutherian mammals for possessing three types of retinal cone. Curiously, catarrhines, platyrrhines, and strepsirhines share this anatomy to different extents, and no hypothesis has hitherto accounted for this variability. Here we propose that the historical biogeography of figs and arborescent palms accounts for the global variation in primate color vision. Specifically, we suggest that primates invaded Paleogene forests characterized by figs and palms, the fruits of which played a keystone function. Primates not only relied on such resources, but also provided high-quality seed dispersal. In turn, figs and palms lost or simply did not evolve conspicuous coloration, as this conferred little advantage for attracting mammals. We suggest that the abundance and coloration of figs and palms offered a selective advantage to foraging groups with mixed capabilities for chromatic distinction. Climatic cooling at the end of the Eocene and into the Neogene resulted in widespread regional extinction or decimation of palms and (probably) figs. In regions where figs and palms became scarce, we suggest primates evolved routine trichromatic vision in order to exploit proteinaceous young leaves as a replacement resource. A survey of the hue and biogeography of extant figs and palms provides some empirical support. Where these resources are infrequent, primates are routinely trichromatic and consume young leaves during seasonal periods of fruit dearth. These results imply a link between the differential evolution of primate color vision and climatic changes during the Eocene-Oligocene transition.

Animals↗
PubMed2003

Geography and niche occupancy as determinants of yeast biodiversity: the yeast-insect-morning glory ecosystem of Kīpuka Puaulu, Hawai'i.

Biodiversity theory proposes two types of hypotheses to account for the species composition of a given community. The first encompasses geographic and historical factors. For example, local species richness is thought to be affected by area, proximity to large landmasses, dispersal mechanisms, and climatic history, collectively known as biogeography. The second type, termed niche occupancy rules, deals with the intrinsic properties of the species as they affect their interaction with the habitat and with other members of the community. The yeast-insect-morning glory ecosystem is a good model to explore biodiversity theory in ascomycetous yeasts. Here we focus on beetles that breed or feed in morning glories and a group of ascomycetous yeasts that are associated exclusively with them. Specifically, we analyse the community found in the vicinity of Kīpuka Puaulu, a small patch of disturbed but mature forest situated amidst lava flows on the island of Hawai'i. Major members of the yeast community include Metschnikowia hawaiiensis, Metschnikowia lochheadii, and the related asexual species Candida ipomoeae and Candida kipukae. These species are nearly indistinguishable from one another in terms of nutritional requirements and abilities, although their phylogenetic range is enormous. Their distribution, both global and local, is far from random. As Kīpuka Puaulu is an island within an island, the principles of island biogeography may be invoked to explain some aspects of its yeast species composition. M. lochheadii, C. ipomoeae, and the rare species Candida hawaiiana are recent introductions from the American continent and therefore exotic, whereas M. hawaiiensis and C. kipukae might be regarded as endemic, as they are yet to be isolated elsewhere. Vectoring by certain nitidulid beetles explains the long-range dispersal of these species. However, niche occupancy rules may account in part for the local spatial distribution of the yeasts within the island of Hawai'i and within the kīpuka itself. We have identified the maximum growth temperature as a potentially critical property of the fundamental niche of these yeasts.

Animals↗
PubMed2000

Diversity and endemism of the benthic seamount fauna in the southwest Pacific.

Seamounts comprise a unique deep-sea environment, characterized by substantially enhanced currents and a fauna that is dominated by suspension feeders, such as corals. The potential importance of these steep-sided undersea mountains, which are generally of volcanic origin, to ocean biogeography and diversity was recognized over 40 years ago, but this environment has remained very poorly explored. A review of seamount biota and biogeography reported a total of 597 invertebrate species recorded from seamounts worldwide since the Challenger expedition of 1872. Most reports, based on a single taxonomic group, were extremely limited: 5 seamounts of the estimated more than 30,000 seamounts in the world's oceans accounted for 72% of the species recorded. Only 15% of the species occurring on seamounts were considered potential seamount endemics. Here we report the discovery of more than 850 macro- and megafaunal species from seamounts in the Tasman Sea and southeast Coral Sea, of which 29-34% are new to science and potential seamount endemics. Low species overlap between seamounts in different portions of the region indicates that the seamounts in clusters or along ridge systems function as 'island groups' or 'chains' leading to highly localized species distributions and apparent speciation between groups or ridge systems that is exceptional for the deep sea. These results have substantial implications for the conservation of this fauna, which is threatened by fishing activity.

Animals↗
PubMed2003

Phylogeography of the harlequin beetle-riding pseudoscorpion and the rise of the Isthmus of Panamá.

Molecular and geological evidence indicates that the emergence of the Isthmus of Panamá influenced the historical biogeography of the Neotropics in a complex, staggered manner dating back at least 9 Myr bp. To assess the influence of Isthmus formation on the biogeography of the harlequin beetle-riding pseudoscorpion, Cordylochernes scorpioides, we analysed mitochondrial COI sequence data from 71 individuals from 13 locations in Panamá and northern South America. Parsimony and likelihood-based phylogenies identified deep divergence between South American and Panamanian clades. In contrast to low haplotype diversity in South America, the Panamanian Cordylochernes clade is comprised of three highly divergent lineages: one clade consisting predominantly of individuals from central Panamá (PAN A), and two sister clades (PAN B1 and PAN B2) of western Panamanian pseudoscorpions. Breeding experiments demonstrated a strictly maternal mode of inheritance, indicating that our analyses were not confounded by nuclear-mitochondrial pseudogenes. Haplotype diversity is striking in western Atlantic Panamá, where all three Panamanian clades can occur in a single host tree. This sympatry points to the existence of a cryptic species hybrid zone in western Panamá, a conclusion supported by interclade crosses and coalescence-based migration rates. Molecular clock estimates yield a divergence time of approximately 3 Myr between the central and western Panamanian clades. Taken together, these results are consistent with a recent model in which a transitory proto-Isthmus enabled an early wave of colonization out of South America at the close of the Miocene, followed by sea level rise, inundation of the terrestrial corridor and then a second wave of colonization that occurred when the Isthmus was completed approximately 3 Myr bp.

Animal Migration↗
PubMed1996

Molecular phylogeny analysis of fiddler crabs: test of the hypothesis of increasing behavioral complexity in evolution.

The current phylogenetic hypothesis for the evolution and biogeography of fiddler crabs relies on the assumption that complex behavioral traits are assumed to also be evolutionary derived. Indo-west Pacific fiddler crabs have simpler reproductive social behavior and are more marine and were thought to be ancestral to the more behaviorally complex and more terrestrial American species. It was also hypothesized that the evolution of more complex social and reproductive behavior was associated with the colonization of the higher intertidal zones. Our phylogenetic analysis, based upon a set of independent molecular characters, however, demonstrates how widely entrenched ideas about evolution and biogeography led to a reasonable, but apparently incorrect, conclusion about the evolutionary trends within this pantropical group of crustaceans. Species bearing the set of "derived traits" are phylogenetically ancestral, suggesting an alternative evolutionary scenario: the evolution of reproductive behavioral complexity in fiddler crabs may have arisen multiple times during their evolution. The evolution of behavioral complexity may have arisen by coopting of a series of other adaptations for high intertidal living and antipredator escape. A calibration of rates of molecular evolution from populations on either side of the Isthmus of Panama suggest a sequence divergence rate for 16S rRNA of 0.9% per million years. The divergence between the ancestral clade and derived forms is estimated to be approximately 22 million years ago, whereas the divergence between the American and Indo-west Pacific is estimated to be approximately 17 million years ago.

Journal Article↗
PubMed2006

Molecular phylogenetics of the exoneurine allodapine bees reveal an ancient and puzzling dispersal from Africa to Australia.

Previous phylogenetic studies of the bee tribe Allodapini suggested a puzzling biogeographic problem: one of the key basal divergences involved separation of the southern African and southern Australian clades at a very early stage in allodapine evolution, but no taxa occur in the Palaearctic or Asian regions that might suggest a Laurasian dispersal route. However, these studies lacked sufficient sequence data and appropriate maximum likelihood partition models to provide reliable phylogenetic estimates and enable alternative biogeographic hypotheses to be distinguished. Using Bayesian and penalized likelihood approaches and an expanded sequence and taxon set we examine phylogenetic relationships between the Australian, African, and Malagasy groups and estimate divergence times for key nodes. We show that divergence of the three basal Australian clades (known as the exoneurines) occurred at least 25 Mya following a single colonization event, and that this group diverged from the African + Madagascan clade at least 30 Mya, but actual divergence dates are likely to be much older than these very conservative limits. The bifurcation order of the exoneurine clades was not resolved and analyses could not rule out the existence of a hard polytomy, suggesting rapid radiation after colonization of Australia. Their divergence involved major transitions in life history traits and these placed constraints on the kinds of social organization that subsequently evolved in each lineage. Early divergence between the African, Malagasy, and Australian clades presents a major puzzle for historical biogeography: node ages are too recent for Gondwanan vicariance hypotheses, but too early for Laurasian dispersal scenarios. We suggest a scenario involving island hopping across the Indian Ocean via a series of now largely submerged elements of the Kergulen Plateau and Broken Ridge provinces, both of which are known to have had subaerial formations during the Cenozoic. [Bayesian; biogeography; dispersal; Gondwana; Kerguelen Plateau; penalized likelihood.].

Africa↗
PubMed2003

Multiple overseas dispersal in amphibians.

Amphibians are thought to be unable to disperse over ocean barriers because they do not tolerate the osmotic stress of salt water. Their distribution patterns have therefore generally been explained by vicariance biogeography. Here, we present compelling evidence for overseas dispersal of frogs in the Indian Ocean region based on the discovery of two endemic species on Mayotte. This island belongs to the Comoro archipelago, which is entirely volcanic and surrounded by sea depths of more than 3500 m. This constitutes the first observation of endemic amphibians on oceanic islands that did not have any past physical contact to other land masses. The two species of frogs had previously been thought to be nonendemic and introduced from Madagascar, but clearly represent new species based on their morphological and genetic differentiation. They belong to the genera Mantidactylus and Boophis in the family Mantellidae that is otherwise restricted to Madagascar, and are distinguished by morphology and mitochondrial and nuclear DNA sequences from mantellid species occurring in Madagascar. This discovery permits us to update and test molecular clocks for frogs distributed in this region. The new calibrations are in agreement with previous rate estimates and indicate two further Cenozoic transmarine dispersal events that had previously been interpreted as vicariance: hyperoliid frogs from Africa to Madagascar (Heterixalus) and from Madagascar to the Seychelles islands (Tachycnemis). Our results provide the strongest evidence so far that overseas dispersal of amphibians exists and is no rare exception, although vicariance certainly retains much of its importance in explaining amphibian biogeography.

Animals↗
PubMed2005

Not so ancient: the extant crown group of Nothofagus represents a post-Gondwanan radiation.

This study uses a molecular-dating approach to test hypotheses about the biogeography of Nothofagus. The molecular modelling suggests that the present-day subgenera and species date from a radiation that most likely commenced between 55 and 40 Myr ago. This rules out the possibility of a reconciled all-vicariance hypothesis for the biogeography of extant Nothofagus. However, the molecular dates for divergences between Australasian and South American taxa are consistent with the rifting of Australia and South America from Antarctica. The molecular dates further suggest a dispersal of subgenera Lophozonia and Fuscospora between Australia and New Zealand after the onset of the Antarctic Circumpolar Current and west wind drift. It appears likely that the New Caledonian lineage of subgenus Brassospora diverged from the New Guinean lineage elsewhere, prior to colonizing New Caledonia. The molecular approach strongly supports fossil-based estimates that Nothofagus diverged from the rest of Fagales more than 84 Myr ago. However, the mid-Cenozoic estimate for the diversification of the four extant subgenera conflicts with the palynological interpretation because pollen fossils, attributed to all four extant subgenera, were widespread across the Weddellian province of Gondwana about 71 Myr ago. The discrepancy between the pollen and molecular dates exists even when confidence intervals from several sources of error are taken into account. In contrast, the molecular age estimates are consistent with macrofossil dates. The incongruence between pollen fossils and molecular dates could be resolved if the early pollen types represent extinct lineages, with similar types later evolving independently in the extant lineages.

Bayes Theorem↗
PubMed2002

Examining genetic structure in a bogus yucca moth: a sequential approach to phylogeography.

Understanding the phylogeography of a species requires not only elucidating patterns of genetic structure among populations, but also identifying the possible evolutionary events creating that structure. The use of a single phylogeographic test or analysis, however, usually provides a picture of genetic structure without revealing the possible underlying evolutionary causes. We used current analytical techniques in a sequential approach to examine genetic structure and its underlying causes in the bogus yucca moth Prodoxus decipiens (Lepidoptera: Prodoxidae). Both historical biogeography and recent human transplantations of the moth's host plants provided a priori expectations of the pattern of genetic structure and its underlying causes. We evaluated these expectations by using a progression of phylogenetic, demographic, and population genetic analyses of mtDNA sequence data from 476 individuals distributed across 25 populations that encompassed the range of P. decipiens. The combination of these analyses revealed that much of the genetic structure has evolved more recently than suggested by historical biogeography, has been influenced by changes in demography, and can be best explained by long distance dispersal and isolation by distance. We suggest that performing a suite of analyses that focus on different temporal scales may be an effective approach to investigating the patterns and causes of genetic structure within species.

Animals↗
PubMed2006

Biogeographic patterns and phylogeography of dwarf chameleons (Bradypodion) in an African biodiversity hotspot.

The southern African landscape appears to have experienced frequent shifts in vegetation associated with climatic change through the mid-Miocene and Plio-Pleistocene. One group whose historical biogeography may have been affected by these fluctuations are the dwarf chameleons (Bradypodion), due to their associations with distinct vegetation types. Thus, this group provides an opportunity to investigate historical biogeography in light of climatic fluctuations. A total of 138 dwarf chameleons from the Cape Floristic Region of South Africa were sequenced for two mitochondrial genes (ND2 and 16S), and resulting phylogenetic analyses showed two well-supported clades that are distributed allopatrically. Within clades, diversity among some lineages was low, and haplotype networks showed patterns of reticulate evolution and incomplete lineage sorting, suggesting relatively recent origins for some of these lineages. A dispersal-vicariance analysis and a relaxed Bayesian clock suggest that vicariance between the two main clades occurred in the mid-Miocene, and that both dispersal and vicariance have played a role in shaping present-day distributions. These analyses also suggest that the most recent series of lineage diversification events probably occurred within the last 3-6 million years. This suggests that the origins of many present-day lineages were founded in the Plio-Pleistocene, a time period that corresponds to the reduction of forests in the region and the establishment of the fynbos biome.

Animals↗
PubMed2005

Island size and bacterial diversity in an archipelago of engineering machines.

There is an increasing realization that progress in bacterial ecology can be further advanced by applying theories and models developed in ecology. Consequently, there is a significant need to assess the applicability of such tools, developed specifically for macroorganisms, for investigating the underlying issues that determine bacterial diversity and community assemblage. In this study, we employed the island biogeography species-area model, originally conceived to assess colonization of islands by macroorganisms, to assess bacterial communities colonizing metal-cutting fluids from machines of increasing sump tank size, taking these to be analogous to islands of variable size. This system was selected because it is well studied and compared with other natural bacterial communities has a relatively low (manageable) diversity. Our findings show that island biogeography theory holds for the bacterial communities studied, in that smaller sump tanks contained lower and putatively less stable diversity, and larger sumps had greater diversity and were temporally stable. It was found that the calculated power law indices (i.e. z-values) were similar for all sample sets, and strikingly, typical of those observed in classical ecology. This was not expected as bacteria have significant distinguishing features such as huge population sizes, rapid asexual reproduction and small body size that facilitate dispersal, and are particularly resistant to extinction.

Bacteria↗
PubMed2006

The questionable effectiveness of science spending by international conservation organizations in the tropics.

The general context of conservation in the tropics--in the Amazon basin and elsewhere--is stagnant or declining funding and rapidly growing threat levels. For conservation programs this makes strategic deployment of limited conservation resources all the more important. International conservation organizations active in the tropics increasingly define themselves as science driven and expend considerable resources on science-based activities such as ecoregional analysis, field research, and monitoring of ecological variables. l argue that an overemphasis on science has generated a series of unintended but serious problems for conservation in the tropics. Spending on monitoring and ecoregional analysis has effectively starved protection and threat analysis of resources. A decoupling of biology from serious cost-benefit analysis has led to the privileging of small-scale and local analyses, rather than the systemic analyses essential for the strategic allocation of scarce conservation resources. Successful conservation in the tropics depends on the crossing of biogeography with sophisticated threat analysis to identify priority geographies for protection. This should be combined with much more systematic engagement with the principal drivers of tropical deforestation, especially agribusiness. Caution and a sense of proportion are required when balancing the financial demands of science and those of protection. I suggest that conservation organizations should cooperate far more in assembling and analyzing information on conservation spending and on threat levels and biogeography at the continental, national, and regional levels. Site selection should follow rather than precede this kind of strategic analysis, and sites should be considered elements of a network rather than stand-alone projects. More attention should be paid to market-driven conservation through techniques such as certification and responsible supply-chain management.

Brazil↗
PubMed2005

A likelihood framework for inferring the evolution of geographic range on phylogenetic trees.

At a time when historical biogeography appears to be again expanding its scope after a period of focusing primarily on discerning area relationships using cladograms, new inference methods are needed to bring more kinds of data to bear on questions about the geographic history of lineages. Here we describe a likelihood framework for inferring the evolution of geographic range on phylogenies that models lineage dispersal and local extinction in a set of discrete areas as stochastic events in continuous time. Unlike existing methods for estimating ancestral areas, such as dispersal-vicariance analysis, this approach incorporates information on the timing of both lineage divergences and the availability of connections between areas (dispersal routes). Monte Carlo methods are used to estimate branch-specific transition probabilities for geographic ranges, enabling the likelihood of the data (observed species distributions) to be evaluated for a given phylogeny and parameterized paleogeographic model. We demonstrate how the method can be used to address two biogeographic questions: What were the ancestral geographic ranges on a phylogenetic tree? How were those ancestral ranges affected by speciation and inherited by the daughter lineages at cladogenesis events? For illustration we use hypothetical examples and an analysis of a Northern Hemisphere plant clade (Cercis), comparing and contrasting inferences to those obtained from dispersal-vicariance analysis. Although the particular model we implement is somewhat simplistic, the framework itself is flexible and could readily be modified to incorporate additional sources of information and also be extended to address other aspects of historical biogeography.

Biological Evolution↗
PubMed2026

An updated checklist of testate amoebae in China.

We present an updated checklist of testate amoebae (TA) in China covering TA records in the literature of the past ∼100 years. In total 363 TA species/subspecies in 53 genera have been included in the current Chinese checklist. The updated Chinese checklist includes five recently discovered TA species (Netzelia mulanensis, Pentagonia zhangduensis, Pontigulasia pentangulostoma, Cornutheca jiuhuensis, and Planhoogenraadia wuchanica) and 24 TA species/subspecies that have been added as new records for China. TA taxonomy and classification in the updated Chinese checklist are based on current knowledge derived from morphological, physiological, and molecular (ribosomal and mitochondrial DNA sequence data, genomics) studies. Corresponding changes in the updated Chinese checklist are outlined and the taxonomy and diversity of (Chinese) TA as well as their biogeography, ecology, and conservation are discussed. As all kinds of TA studies are eventually based on a reliable taxonomy and nomenclature, we are confident that our updated Chinese checklist will be of great value for TA researchers not only in China, but also worldwide.

China↗
PubMed2025

Caenorhabditis diversity on Pohnpei, Micronesia, provides evidence that the Elegans Supergroup has its roots in the Americas and diversified in the Pacific en route to Asia.

The microscopic nematode Caenorhabditis elegans stands unrivaled as a model for developmental biology, neurobiology, and genetics, but fundamental aspects of its ecology, biogeography, and natural history remain unknown. Leveraging recent findings that place its center of diversity in the cool, high-elevation forests of Hawaii, we performed an intensive survey of the Caenorhabditis fauna of Pohnpei, a high island in Micronesia that is home to the largest patch of high-elevation forest between Hawaii and East Asia. We found nine species of Caenorhabditis, five of them new, but not C. elegans. Most species were limited to the hot lowlands but three spanned the elevational range and one was found only in the cloudforest. Using the distribution of Caenorhabditis nematodes among habitat patches - individual rotting fruits or flowers - we parameterized simple models that capture key aspects of the population biology of these animals. We generated transcriptomes for the new species and inferred a phylogeny for 70 species of Caenorhabditis, based on 2955 genes. This phylogeny allowed us to perform the first quantitative biogeographic analysis for the group. Our analysis suggests that the deep ancestors of the Elegans Supergroup of species lived in the Americas, and that the Supergroup's subsequent diversification occurred in Remote Oceania. The ancestors of the Supergroup gave rise to a diverse Oceanian fauna and ultimately to multiple lineages that moved into Asia, Africa, Australasia, and back into the Americas. Though biogeographic inferences are limited by the lack of information from key regions of the southwest Pacific, the data are consistent with a model of trans-Pacific migration, with the islands of Oceania serving as sources rather than sinks for biodiversity.

Caenorhabditis↗
PubMed1999

Lemur traits and Madagascar ecology: coping with an island environment.

The last decade's lemur research includes successes in discovering new living and extinct species and learning about the distribution, biogeography, physiology, behavior, and ecology of previously little-studied species. In addition, in both the dry forest and rain forest, long-term studies of lemur demography, life history, and reproduction, have been completed in conjunction with data on tree productivity, phenology, and climate. Lemurs contrast with anthropoids in several behavioral features, including female dominance, targeted female-female aggression, lack of sexual dimorphism regardless of mating system, sperm competition coupled with male-male aggression, high infant mortality, cathemerality, and strict seasonal breeding. Hypotheses to explain these traits include the "energy conservation hypothesis" (ECH) suggesting that harsh and unpredictable climate factors on the island of Madagascar have affected the evolution of female dominance, and the "evolutionary disequilibrium hypotheses" (EVDH) suggesting that the recent megafauna extinctions have influenced lemurs to become diurnal. These hypotheses are compared and contrasted in light of recent empirical data on climate, subfossils, and lemur behavior. New data on life histories of the rain forest lemurs at Ranomafana National Park give further support to the ECH. Birth seasons are synchronized within each species, but there is a 6-month distribution of births among species. Gestation and lactation lengths vary among sympatric lemurs, but all lemur species in the rain forest wean in synchrony at the season most likely to have abundant resources. Across-species weaning synchrony seen in Ranomafana corroborates data from the dry forest that late lactation and weaning is the life history event that is the primary focus of the annual schedule. Lemur adaptations may assure maximum offspring survival in this environment with an unpredictable food supply and heavy predation. In conclusion, a more comprehensive energy frugality hypothesis (EFH) is proposed, which postulates that the majority of lemur traits are either adaptations to conserve energy (e.g., low basal metabolic rate (BMR), torpor, sperm competition, small group size, seasonal breeding) or to maximize use of scarce resources (e.g., cathemerality, territoriality, female dominance, fibrous diet, weaning synchrony). Among primates, the isolated adaptive radiation of lemurs on Madagascar may have been uniquely characterized by selection toward efficiency to cope with the harsh and unpredictable island environment.

Adaptation, Physiological↗
PubMed2006

Edge effects and their influence on lemur density and distribution in Southeast Madagascar.

Edge effects are caused by the penetration of abiotic and biotic conditions from the matrix into forest interiors. Although edge effects influence the biogeography of many tropical organisms, they have not been studied directly in primates. Edge effects are particularly relevant to lemurs due to the loss of 80-90% of forests in Madagascar. In this study, data are presented on how biotic edge effects influenced the distribution and density of lemurs in the Vohibola III Classified Forest in southeastern Madagascar. In total, 415 lemur surveys were conducted during June-October 2003 and May-September 2004 along six 1,250-m transects that ran perpendicular to the forest edge. Data were also collected on lemur food trees along the six transects (density, height, diameter at breast height, area, volume, and distance to forest edge). Four nocturnal species (Avahi laniger, Cheirogaleus major, Lepilemur microdon, and Microcebus rufus) and four diurnal species (Eulemur rubriventer, Eulemur fulvus rufus, Hapalemur grisesus griseus, and Propithecus diadema edwardsi) were sighted during surveys. Regression analyses of lemur densities as a function of distance to forest edge provided edge tolerances for A. laniger (edge-tolerant), M. rufus (edge-tolerant), E. rubriventer (edge-tolerant or omnipresent), and H. g. griseus (omnipresent). The density and distribution of M. rufus and their foods trees were correlated. Edge-related variations in food quality and predation pressures may also be influencing lemurs in Vohibola III. Tolerance for edge effects may explain, in part, how lemurs have survived extreme habitat loss and forest fragmentation in southeastern Madagascar.

Animals↗
PubMed2005

Dental morphology and variation in theropod dinosaurs: implications for the taxonomic identification of isolated teeth.

Isolated theropod teeth are common Mesozoic fossils and would be an important data source for paleoecology biogeography if they could be reliably identified as having come from particular taxa. However, obtaining identifications is confounded by a paucity of easily identifiable characters. Here we discuss a quantitative methodology designed to provide defensible identifications of isolated teeth using Tyrannosaurus as a comparison taxon. We created a standard data set based as much as possible on teeth of known taxonomic affinity against which to compare isolated crowns. Tooth morphology was described using measured variables describing crown length, base length and width, and derived variables related to basal shape, squatness, mesial curve shape, apex location with respect to base, and denticle size. Crown curves were described by fitting the power function Y = a + bX(0.5) to coordinate data collected from lateral-view images of mesial curve profiles. The b value from these analyses provides a measure of curvature. Discriminant analyses compared isolated teeth of various taxonomic affinities against the standard. The analyses classified known Tyrannosaurus teeth with Tyrannosaurus and separated most teeth known not to be Tyrannosaurus from Tyrannosaurus. They had trouble correctly classifying teeth that were very similar to Tyrannosaurus and for which there were few data in the standard. However, the results indicate that expanding the standard should facilitate the identification of numerous types of isolated theropod teeth.

Analysis of Variance↗