An official website of the United States government
The Chromodorididae family tree has been refined in recent years via molecular phylogenetic analyses which have clarified many relationships between taxa. The genus Goniobranchus is one clade within Chromodorididae that was previously included within the genus Chromodoris. However, based on recent molecular phylogenetic results, Chromodoris was determined to be non-monophyletic and Goniobranchus was resurrected. In this study, we performed molecular and morphological analyses to resolve the internal relationships among Goniobranchus species, specifically the red-reticulate species complex of three previously described species, Goniobranchus tinctorius, G. reticulatus, and G. alderi, which display a red network of lines over a white mantle and are widely distributed across the Indo-Pacific Ocean. We sequenced two mitochondrial genes (COI and 16S) and one nuclear gene (H3) for 339 Goniobranchus specimens, and in our phylogenetic analyses the red-reticulate species group emerged as a monophyly. This current work has indicated there are at least eleven distinct species within this species complex, including the only three previously described species and another described species, G. splendidus, was added to this clade. The molecular data and the morphological differences among species will be discussed, and we present a possible way forward to clarify the taxonomy of the red-reticulate species complex.
more »
« less
Integrative taxonomic and geographic variation analyses in Cyrtodactylus aequalis (Squamata: Gekkonidae) from southern Myanmar (Burma): one species, two different stories
The historical accuracy of building taxonomies is improved when they are based on phylogenetic inference (i.e., the resultant classifications are less apt to misrepresent evolutionary history). In fact, taxonomies inferred from statistically significant diagnostic morphological characters in the absence of phylogenetic considerations, can contain non-monophyletic lineages. This is especially true at the species level where small amounts of gene flow may not preclude the evolution of localized adaptions in different geographic areas while underpinning the paraphyletic nature of each population with respect to the other. We illustrate this point by examining genetic and morphological variation among three putatively allopatric populations of the granite-dwelling Bent-toed Gecko Cyrtodactylus aequalis from hilly regions in southeastern Myanmar. In the absence of molecular phylogenetic inference, a compelling argument for three morphologically diagnosable species could be marshaled. However, when basing the morphological analyses of geographic variation on a molecular phylogeny, there is a more compelling argument that only one species should be recognized. We are cognizant of the fact however, that when dealing with rare species or specimens for which no molecular data are possible, judicious morphological analyses are the only option—and the desired option given the current worldwide biodiversity crisis.
more »
« less
- Award ID(s):
- 1656004
- PAR ID:
- 10159580
- Date Published:
- Journal Name:
- Israel Journal of Ecology and Evolution
- ISSN:
- 2224-4662
- Page Range / eLocation ID:
- 1 to 29
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
The type of the xeniid soft coral Sansibia flava (May, 1898) is re-described for the first time and its morphological diagnosis is presented. A subsequent integrated analysis of molecular and morphological characters of related Xeniidae, including species indigenous to the Indo-Pacific Ocean and invasive in the Atlantic (Brazil), led to the description of a new Sansibia species, as well as two new genera comprising an additional three new species. All of these taxa are encrusting, with polyps arising directly from a spreading basal membrane. Molecular phylogenetic analyses show that these genera are not sister taxa, thus further emphasizing the remarkable phylogenetic diversity of xeniids with such a growth form. The sclerites of all species are uniformly ellipsoid platelets, abundant throughout the colony. The species exhibit restricted, non-overlapping geographic ranges, with distinct genotypes (molecular operational taxonomic units) found in different marine realms. The results emphasize the importance of re-examination of original old type material while applying molecular phylogenetic analyses in order to delineate species boundaries and to recognize biodiversity patterns.more » « less
-
The oldest existing type material for any of the xeniid soft corals, Sympodium caeruleum Ehrenberg, 1834, is re-described. An integrated analysis of molecular and morphological characters of Indo-Pacific Xeniidae support the description of seven new species of that genus. The extent of interspecific morphological variation within the genus is extensive; colonies arise from an encrusting membrane of variable thickness that can be either mat-like or may have ribbon-like extensions or irregularly shaped low mounds. The polyps can either arise separately from the membrane or may be arranged into clusters of polyps that bud off at different levels to form small branched groups. The sclerites of all species are uniformly ellipsoid platelets, abundant throughout the colony. The genetic results suggest that Sympodium species demonstrate restricted geographic ranges and regional endemism, with distinct genotypes (molecular operational taxonomic units) each mostly found at a single Indo-Pacific location. The results emphasize the importance of integrating classical taxonomy with a re-examination of original old type material and molecular phylogenetic analyses, in order to delineate species boundaries and to recognize biodiversity patterns.more » « less
-
Abstract The fossilized birth–death (FBD) process provides an ideal model for inferring phylogenies from both extant and fossil taxa. Using this approach, fossils are directly integrated into the tree, leading to a statistically coherent prior on divergence times. Since fossils are typically not associated with molecular sequences, additional information is required to place fossils in the tree. We use simulations to evaluate two different approaches to handling fossil placement in FBD analyses: using topological constraints, where the user specifies monophyletic clades based on established taxonomy, or using total‐evidence analyses, which use a morphological data matrix in addition to the molecular alignment. We also explore how rate variation in fossil recovery or diversification rates impacts these approaches. We find that the extant topology is well recovered under all methods of fossil placement. Divergence times are similarly well recovered across all methods, with the exception of constraints which contain errors. We see similar patterns in datasets which include rate variation, however, relative errors in extant divergence times increase when more variation is included in the dataset, for all approaches using topological constraints, and particularly for constraints with errors. Finally, we show that trees recovered under the FBD model are more accurate than those estimated using non‐time calibrated inference. Overall, we show that both fossil placement approaches are reliable even when including uncertainty. Our results underscore the importance of core taxonomic research, including morphological data collection and species descriptions, irrespective of the approach to handling phylogenetic uncertainty using the FBD process.more » « less
-
The subspecies rank has been widely applied by taxonomists to capture infraspecific variation within the Linnaean classification system. Many subspecies described throughout the 20th century were recognised largely based on perceived variation in single morphological characters yet have since been found not to correspond to separately evolving population lineages, thus requiring synonymy or elevation to full species under lineage-based views of species. These modern lineage-based taxonomic resolutions have resulted from a combination of new molecular genetic techniques, improved geographical sampling of specimens, and more sophisticated analyses of morphological variation (e.g., statistical assessments rather than solely univariate descriptive ones). Here, we revisit the current taxonomic arrangement of species-level and subspecific taxa in the Lerista microtis (Gray) group, which is distributed along a narrow ~2000 km strip on the southern coast of Australia. From specimens of the L. microtis group, an additional species (Lerista arenicola) and two additional subspecies (L. m. intermedia and L. m. schwaneri) were described. We collected data on mensural, meristic, and colour pattern characters to explore morpho-spatial relationships among these taxa. Although our morphological analyses revealed some distinctiveness among specimens from locations assigned to each taxon, this variation is continuous along Australia’s southern coastline, assuming the form of a geographic cline rather than discrete forms. For many characters, however, spatial patterns were inconsistent with the original descriptions, particularly of the subspecies. Moreover, analysis of genome wide restriction-associated DNA loci revealed multiple instances of paraphyly among taxa, with phylogenetic clustering of specimens assigned to distinct species and subspecies. These emerging patterns provide no support for L. arenicola as a species evolving separately from L. microtis. Additionally, our findings challenge the presumed distinctiveness and coherence of the three subspecies of L. microtis. We thus synonymise L. arenicola and the L. microtis subspecies with L. microtis and provide a redescription of a single yet morphologically variable species—an arrangement that best reflects evolutionary history and the continuous nature of morphological variation across space.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1163/22244662-20191082
