An official website of the United States government
Abstract Taxonomic classification is important for understanding the natural world, yet current methods for species assessment often focus on craniodental morphology rather than the entire skeleton. Moreover, it is currently unknown how much variation could, or should, exist intragenerically. Here, we tested whether taxonomy can be accurately predicted based on patterns of morphological variation in macaques (H1) and whether postcranial bones reflect subgeneric macaque taxonomy similarly, or better, than the cranium (H2). Data included 3D scans of cranial and postcranial bones for eight macaque species (Macaca arctoides,Macaca fascicularis,Macaca fuscata,Macaca mulatta,Macaca nemestrina,Macaca nigra,Macaca radiata, andMacaca sylvanus). Fixed anatomical and semilandmarks were applied to scans of eight skeletal elements (crania = 45; mandible = 31; scapula = 66; humerus = 38; radius = 33; os coxa = 28; femur = 40; tibia = 40). For each skeletal element, regression analyses were performed to minimize the effects of sexual dimorphism. Between‐groups principal components analysis was used to visualize the major patterns of among‐species morphological variation, while the strength of correct taxon classification was measured with discriminant function analysis. Results suggested accepting the alternate hypothesis that different macaque species can be distinguished morphologically. Both cranial and many postcranial elements appeared to possess a taxonomic signal, and the limb bones—especially the upper limb—are reported to be more useful for taxonomic assessment than previously realized. Theoretically, certain behaviors and/or ecogeographical factors, as well as phylogeny, influenced skeletal morphology in macaques, likely contributing to taxonomic distinctions among different species.
more »
« less
This content will become publicly available on January 3, 2026
A hypothesis-based approach to species identification in the fossil record: a papionin case study
Modern papionin monkeys are a diverse group that encompasses a broad range of morphologies, behaviors, and ecologies. A fossil genus known from African Plio-Pleistocene deposits, Parapapio, is widely regarded as a candidate ancestor to later African papionins. However, despite general agreement that this genus sits at or near the base of the African papionin clade, the taxonomy within Parapapio remains highly contentious. This project evaluates the species-level taxonomy of Parapapio with an explicit hypothesis-based approach to interpreting morphological variation in this sample of fossils. We tested two hypotheses: (H1) the craniodental variation within Parapapio does not cluster into three groups that reflect the three known species, and (H2) all the Parapapio fossils can be accommodated within the craniodental shape and size variation observed for a single extant species of papionin. To test the first hypothesis, we assessed a subset of relatively complete and well-preserved Parapapio crania (n=16), intentionally without reference to previous taxonomic identifications. Specimens were sorted by similarity in cranial features and results were then compared with published taxonomic classifications. Our results demonstrate that morphological traits do not cluster consistently according to the current species categories within Parapapio, failing to reject our first hypothesis. To test our second hypothesis, we examined variation in cranial and dental metrics within Parapapio (n=64) relative to three extant papionin samples (n=310). Our results fail to reject the hypothesis that all Parapapio specimens could belong to a single species and suggest that the three-species paradigm does not reflect the anatomical variation of this genus. We recommend subsuming all Parapapio specimens within Parapapio broomi, the species name with taxonomic priority. The results of this hypothesis-testing approach to taxonomy carry substantial implications for the taxonomy of Parapapio, as well as for biochronological and paleoecological studies more generally, including the taxonomy and paleobiology of hominids recovered from these same deposits.
more »
« less
- Award ID(s):
- 2235771
- PAR ID:
- 10585677
- Publisher / Repository:
- Frontiers in Ecology and Evolution
- Date Published:
- Journal Name:
- Frontiers in Ecology and Evolution
- Volume:
- 12
- ISSN:
- 2296-701X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Taxonomic classification is fundamental for understanding the natural world, yet current methods for unknown species assessment are based on qualitative methods and focused on craniodental morphology. It is currently unknown how much variation could, or should, exist within a particular genus. Here, we tested whether taxonomy can be accurately predicted from patterns of morphological variation in a geographically widespread taxa, the macaques (H1) and whether postcranial bones reflect subgeneric taxonomy similarly, or better, than the cranium (H2). Data included 3D scans from nine species (M. arctoides, M. fascicularis, M. fuscata, M. mulatta, M. nemestrina, M. nigra, M. radiata, M. sylvanus, and outgroup Trachypithecus cristatus), for a sample of 297 individuals. Macaque species were chosen for their phylogenetic diversity and their geographic representation. 293 fixed and semilandmarks were applied to eight skeletal elements for each individual (crania=45; mandible=31; scapula=66; humerus=38; radius=33; os coxa=28; femur=40; tibia=40). A regression analysis was performed to minimize the effects of sexual dimorphism, making the primary input variables regression residuals. Patterns of variation were analyzed between- and within-species via Canonical Variates Analysis and 2D Multidimensional Scaling. Classificatory ability was tested using Discriminant Function Analysis. Results suggest that different species of macaque monkeys are taxonomically distinct and that the crania and postcrania possess a taxonomic signal. Some bones, like the limb bones, were more useful taxonomically than previously realized. Results suggest that taxonomic assessment should be updated to reflect newer methodologies and we argue that these results should inform future studies.more » « less
-
Camacho, Gabriela P (Ed.)Abstract The ant genus Nylanderia Emery has a cosmopolitan distribution and includes 150 extant described species and subspecies, with potentially hundreds more undescribed. Global taxonomic revision has long been stalled by strong intra- and interspecific morphological variation, limited numbers of diagnostic characters, and dependence on infrequently collected male specimens for species description and identification. Taxonomy is further complicated by Nylanderia being one of the most frequently intercepted ant genera at ports of entry worldwide, and at least 15 globetrotting species have widespread and expanding ranges, making species-level diagnoses difficult. Three species complexes (‘bourbonica complex’, ‘fulva complex’, and ‘guatemalensis complex’) include globetrotting species. To elucidate the phylogenetic positions of these three complexes and delimit species boundaries within each, we used target enrichment of ultraconserved elements (UCEs) from 165 specimens representing 98 Nylanderia morphospecies worldwide. We also phased the UCEs, effectively doubling sample size and increasing population-level sampling. After recovering strong support for the monophyly of each complex, we extracted COI barcodes and SNPs from the UCE data and tested within-complex morphospecies hypotheses using three molecular delimitation methods (SODA, bPTP, and STACEY). This comparison revealed that most methods tended to over-split taxa, but results from STACEY were most consistent with our morphospecies hypotheses. Using these results, we recommend species boundaries that are conservative and most congruent across all methods. This work emphasizes the importance of integrative taxonomy for invasive species management, as globetrotting occurs independently across at least nine different lineages across Nylanderia.more » « less
-
Abstract The genus Ponera includes over 60 extant species worldwide. These tiny, endogeic predator ants are predominantly distributed in the Indomalaya and Australasia regions, with a few additional Holarctic species. Herein, we explore and describe the diversity of the Malagasy Ponera fauna through an integrative taxonomic approach. We obtained our morphological species hypotheses from multivariate analyses of ten continuous morphometric characters. Species boundaries and reliability of morphological clusters were tested via confirmatory Linear Discriminant Analysis (LDA), cross-validation (LOOCV), and analyses of a mitochondrial COI gene fragment. According to the combined application of the analyses, altogether, three species are inferred in the Malagasy region, Ponera petila Wilson (1957), P. swezeyi Wheeler (1933), and P. adumbrans Csősz & Fisher sp. n. Ponera petila and P. swezeyi belong to the Indo-Australian Ponera tenuis group; the third species, P. adumbrans sp. n., is morphologically similar to the Papua New Guinean P. clavicornis Emery (1900). Furthermore, Linear Discriminant Analysis classified the type specimens of P. bableti Perrault (1993), along with a P. petila cluster with posterior p = 1. Therefore, we propose the new junior synonymy of P. bableti with P. petila . Madagascar’s extant biodiversity is predominantly explained by colonization events from the African continent across the Mozambique channel via rafting. However, since no native Ponera species are known from the Afrotropical continent, and the closest congeners have an almost exclusively Indo-Australian distribution, the likelihood of an Indo-Australian origin of the Malagasy Ponera fauna is implied.more » « less
-
Abstract The phylogenetic relationships within crown Crocodylia remain contentious due to conflicts between molecular and morphological hypotheses. However, morphology‐based datasets are mostly constructed on external characters, overlooking internal structures. Here, we use 3D geometric morphometrics to study the shape of the intertympanic sinus system in crown crocodylians during ontogeny, in order to assess its significance in a taxonomic context. Intertympanic sinus shape was found to be highly correlated with size and modulated by cranial shape during development. Still, adult sinus morphology distinguishes specimens at the family, genus and species level. We observe a clear distinction between Alligatoridae and Longirostres, a separation of differentCrocodylusspecies and the subfossil Malagasy genusVoay, and a distinction between theTomistomaandGavialislineages. Our approach is independent of molecular methods but concurs with the molecular topologies. Therefore, sinus characters could add significantly to morphological datasets, offering an alternative viewpoint to resolve problems in crocodylian relationships.more » « less
