590 Tiere (Zoologie)
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In this second part of the study, using a ‘clean’ dataset without very low precision landmarks and outliers, I describe how to compare mandibular size and shape using Procrustes methods in adult North American marmots. After demonstrating that sex differences are negligible, females and males are pooled together with specimens of unknown sex and species are compared using a battery of tests, that estimate both statistical significance and effect size. The importance of allometric variation and its potential effect on shape differences is also explored. Finally, to provide potential clues on founder effects, I compare the magnitude of variance in mandibular size and shape between the Vancouver Island marmot (VAN) and the hoary marmot, its sister species on the mainland. In almost all main analyses, I explore the sensitivity of results to heterogeneous sample size and small samples using subsamples and randomized selection experiments. For both size and shape, I find a degree of overlap among species variation but, with very few exceptions, mean interspecific differences are well supported in all analyses. Shape, in particular, is an accurate predictor of taxonomic affiliation. Allometry in adults, however, explains a modest amount of within-species shape change. Yet, there is a degree of divergence in allometric trajectories that seems consistent with subgeneric separation. VAN is the most distinctive species for mandibular shape and mandibular morphology suggests a long history of reduced variation in this insular population. Geometric morphometrics (GMM) is a powerful tool to aid taxonomic research. Regardless of the effectiveness of this family of methods and the apparent robustness of results obtained with GMM, however, large samples and careful measurements remain essential for accuracy. Even with excellent data, morphometrics is important, but its findings must be corroborated with an integrative approach that combines multiple lines of evidence to taxonomic assessment. The analytical protocol I suggest is described in detail, with a summary checklist, in the Appendix, not to miss important steps. All the analyses can be replicated using the entire dataset, which is freely available online. Beginners may follow all the steps, whereas more experienced researchers can focus on one specific aspect and read only the relevant chapter. There are limitations, but the protocol is flexible and easy to improve or implement using a programming language such as R.
To better understand the dung beetle (Coleoptera: Scarabaeidae: Scarabaeinae) biodiversity of Costa Rica and Panama, new synonyms, records, distributions, and updates are presented. This paper analyzes the distribution and taxonomy of Phanaeus olsoufieffi Balthasar, 1939 in Panama and establishes the following new subjective synonym: Phanaeus panamensis Moctezuma and Halffter, 2021 = Phanaeus olsoufieffi Balthasar, 1939. Color morphs of Phanaeus pyrois Bates, 1887 in Costa Rica are analyzed. The Costa Rican distribution of Onthophagus bidentatus Drapiez, 1819 and O. marginicollis Harold, 1880 is studied. Onthophagus bidentatus is recorded for Costa Rica for the first time. A population analysis of barcode mtDNA, color morphs, and morphological and genitalia characters for different body sizes of Onthophagus cyanellus is undertaken. An mtDNA barcode tree is presented to assess the molecular identity of O. cyanellus resulting in the reaffirmed subjective synonymy, Onthophagus mesoamericanus Zunino and Halffter, 1988 = O. cyanellus Bates, 1887.
ZooBank registration. urn:lsid:zoobank.org:pub:E701D60F-A455-4048-8279-DA450930ACB3