The Gulf of California, Mexico is home to many cetacean species, including a presumed resident population of fin whales, Balaenoptera physalus . Past studies reported very low levels of genetic diversity among Gulf of California fin whales and a significant level of genetic differentiation from con-specifics in the eastern North Pacific. The aim of the present study was to assess the degree and timing of the isolation of Gulf of California fin whales in a population genetic analysis of 18 nuclear microsatellite genotypes from 402 samples and 565 mitochondrial control region DNA sequences (including mitochondrial sequences retrieved from NCBI). The analyses revealed that the Gulf of California fin whale population was founded ~2.3 thousand years ago and has since remained at a low effective population size (~360) and isolated from the eastern North Pacific ( N e m between 0.89–1.4). The low effective population size and high degree of isolation implied that Gulf of California fin whales are vulnerable to the negative effects of genetic drift, human-caused mortality and habitat change.

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Studies of cetacean evolution using genetics and other biomolecules have come a long way—from the use of allozymes and short sequences of mitochondrial or nuclear DNA to the assembly of full nuclear genomes and characterization of proteins and lipids. Cetacean research has also advanced from using only contemporary samples to analyzing samples dating back thousands of years, and to retrieving data from indirect environmental sources, including water or sediments. Combined, these studies have profoundly deepened our understanding of the origin of cetaceans; their adaptation and speciation processes; and of the past population change, migration, and admixture events that gave rise to the diversity of cetaceans found today.

The specimens deposited in a scientific collection are the physical evidence of living, as well as extinct, life forms. The physical state and the accuracy of the data and of the specimens stored in a collection may be assessed by the health level of the collection, which is represented by the collection profile and a health index. This paper presents a practical method for assessing a mammal collection health level. This method was designed and standardized following previous works and includes 8 levels. The method was applied to the Colección Nacional de Mamíferos (CNMA), housed at the Instituto de Biología, Universidad Nacional Autónoma de México, in 2011 and in 2015. The cataloged specimens were selected by a stratified random sampling in 2011 and a simple random sampling in 2015. Specimens that had not been cataloged were also assessed and selected by a stratified sampling in both years. A total of 336 specimens were evaluated in 2011 and 331 in 2015. The health index in the CNMA was 0.70 in 2015.Keywords: Biodiversity; Certification; Biological collections; Curatorial standards; Health index; Handling; Maintenance ResumenLos ejemplares albergados en las colecciones científicas constituyen evidencias físicas de formas de vida presentes así como extintas. El estado físico y la precisión de los datos de los ejemplares depositados en las colecciones científicas se pueden evaluar con un método conocido como nivel de salud, que está representado por el perfil de la colección y el índice de salud. Este artículo presenta un método práctico para evaluar el nivel de salud de una colección de mamíferos. El método fue diseñado siguiendo trabajos previos e incluye 8 niveles. El método se aplicó a la Colección Nacional de Mamíferos (CNMA) del Instituto de Biología, UNAM, en 2011 y en 2015. Los ejemplares catalogados fueron seleccionados por muestreo aleatorio estratificado en el 2011 y por un muestreo aleatorio simple en el 2015. Los ejemplares que no habían sido catalogados también se evaluaron y se seleccionaron mediante un muestreo sistemático. Se evaluaron 336 ejemplares en 2011 y 331 en 2015. El índice de salud en la CNMA fue de 0.70 en 2015.Palabras clave: Biodiversidad; Certificación; Colecciones biológicas; Estándares curatoriales; Índice de salud; Manejo; Mantenimiento V.E. Rivera-León et al. / Revista Mexicana de Biodiversidad 89 (2018): 402-411 403 https://doi

HighlightsMitochondrial monophyly is commonly employed to define evolutionary significant units.Monophyly may be caused by insufficient sampling or a recent common ancestor.Mitogenomic studies are generally based on few samples and prone to sampling issues.Expanded mitogenome sampling negates previous monophyly in fin whales.AbstractThe advent of massive parallel sequencing technologies has resulted in an increase of studies based upon complete mitochondrial genome DNA sequences that revisit the taxonomic status within and among species. Spatially distinct monophyly in mitogenomic genealogies, i.e., the sharing of a recent common ancestor among con-specific samples collected in the same region has been viewed as evidence for subspecies. Several recent studies in cetaceans have employed this criterion to suggest subsequent intraspecific taxonomic revisions. We reason that employing intra-specific, spatially distinct monophyly at non-recombining, clonally inherited genomes is an unsatisfactory criterion for defining subspecies based upon theoretical (genetic drift) and practical (sampling effort) arguments. This point is illustrated by a re-analysis of a global mitogenomic assessment of fin whales, Balaenoptera physalus spp., published by Archer et al. (2013) which proposed to further subdivide the Northern Hemisphere fin whale subspecies, B. p. physalus. The proposed revision was based upon the detection of spatially distinct monophyly among North Atlantic and North Pacific fin whales in a genealogy based upon complete mitochondrial genome DNA sequences. The extended analysis conducted in this study (1,676 mitochondrial control region, 162 complete mitochondrial genome DNA sequences and 20 microsatellite loci genotyped in 358 samples) revealed that the apparent monophyly among North Atlantic fin whales reported by Archer et al. (2013) to be due to low sample sizes. In conclusion, defining sub-species from monophyly (i.e., the absence of para-or polyphyly) can lead to erroneous conclusions due to relatively “trivial” aspects, such as sampling. Basic population genetic processes (i.e., genetic drift and migration) also affect the time to most recent common ancestor and hence the probability that individuals in a sample are monophyletic.