Expansión poblacional reciente en la historia evolutiva de la anchoveta de California Engraulis mordax

Recent population expansion in the evolutionary history of the Californian anchovy Engraulis mordax

NOE DIAZ VILORIA LAURA SANCHEZ VELASCO RICARDO PEREZ ENRIQUEZ (2012, [Artículo])

"La anchoveta de California Engraulis mordax, es una especie templada que pudo haber pasado por un proceso de disyunción poblacional, debido al proceso postglacial de calentamiento del agua alrededor de la punta de la península de Baja California, hace unos 10,000 años. Se realizó un análisis genético para probar la hipótesis nula de homogeneidad genética entre el Golfo de California, México y el sur de California, EUA y si este era el caso, estimar el tiempo de surgimiento de haplotipos en términos de coalescencia. Se analizaron en total 80 secuencias de la región control hipervariable (ADNmt) de E. mordax, capturadas en la región central del Golfo de California (n = 40) y el sur de California (n = 40). A pesar del gran número de haplotipos únicos, no se observó diferenciación genética significativa entre localidades (FST = –0.0025, p = 0.686). Una distribución unimodal en la frecuencia del número de diferencias entre haplotipos indica un modelo de expansión rápida en el tamaño poblacional, que basado en una tasa mutacional de 3.6% por millón de años para la región control, indicó un tiempo de diferenciación nucleotídica relativamente reciente de aproximadamente 61,000 años. Este periodo de tiempo corresponde al Pleistoceno tardío, después de la formación de la península de Baja California, sugiriendo expansiones poblacionales en cada una de las localidades, seguidas del último episodio de glaciación, el cual quizás contribuyó a la migración de esta especie de afinidad templada entre las dos localidades y a su homogenización genética. Sin embargo este único evento reciente de flujo genético en la historia evolutiva de la especie, no explica por sí solo los patrones de distribución encontrados en las frecuencias de diferencias nucleotídicas."

"The Californian anchovy Engraulis mordax, a temperate species, may have undergone a process of population disjunction from experiencing post-glacial water heating processes around the tip of the Baja California Peninsula, Mexico about 10,000 b.p. A genetic analysis was performed to test the null hypothesis of genetic homogeneity between the Gulf of California and Southern California, U. S. A., and if this is the case, to estimate the time of haplotype emergence in terms of coalescence. A total of 80 sequences of the mtDNA hypervariable control region of E. mordax captured in the central Gulf of California (n = 40) and Southern California (n = 40) were analyzed. In spite of the large number of private haplotypes, no significant genetic differentiation among sites (FST = –0.0025, p = 0.686) was observed. An unimodal distribution of mismatch frequency between haplotypes indicated a model of rapid expansion in population size that, based on a mutation rate of 3.6% per million years in the control region, indicates a relatively recent nucleotide differentiation

time of approximately 61,000 years. This time period corresponds to the late Pleistocene, suggesting population expansions at each locality, followed by the last episode of glaciation, which may have contributed to migration of this temperate-affinity species between two locations and the genetic homogenization. However this unique recent event of gene flow in the evolutionary history of species does not explain by itself the mismatch distribution patterns found."

ADN mitocondrial, expansión poblacional reciente, flujo genético, región control, reloj molecular. Control region, gene flow, mitochondrial DNA, molecular clock, recent population expansion. BIOLOGÍA Y QUÍMICA CIENCIAS DE LA VIDA BIOLOGÍA ANIMAL (ZOOLOGÍA) ZOOLOGÍA MARINA ZOOLOGÍA MARINA

Maintenance of Coastal Surface Blooms by Surface Temperature Stratification and Wind Drift

MARY CARMEN RUIZ DE LA TORRE (2013, [Artículo])

Algae blooms are an increasingly recurrent phenomenon of potentially socio-economic impact in coastal waters globally and in the coastal upwelling region off northern Baja California, Mexico. In coastal upwelling areas the diurnal wind pattern is directed towards the coast during the day. We regularly found positive Near Surface Temperature Stratification (NSTS), the resulting density stratification is expected to reduce the frictional coupling of the surface layer from deeper waters and allow for its more efficient wind transport. We propose that the net transport of the top layer of approximately 2.7 kilometers per day towards the coast helps maintain surface blooms of slow growing dinoflagellate such as Lingulodinium polyedrum. We measured: near surface stratification with a free-rising CTD profiler, trajectories of drifter buoys with attached thermographs, wind speed and direction, velocity profiles via an Acoustic Doppler Current Profiler, Chlorophyll and cell concentration from water samples and vertical migration using sediment traps. The ADCP and drifter data agree and show noticeable current shear within the first meters of the surface where temperature stratification and high cell densities of L. polyedrum were found during the day. Drifters with 1m depth drogue moved towards the shore, whereas drifters at 3 and 5 m depth showed trajectories parallel or away from shore. A small part of the surface population migrated down to the sea floor during night thus reducing horizontal dispersion. The persistent transport of the surface bloom population towards shore should help maintain the bloom in favorable environmental conditions with high nutrients, but also increasing the potential socioeconomic impact of the blooms. The coast wise transport is not limited to blooms but includes all dissolved and particulate constituents in surface waters. © 2013 Ruiz-de la Torre et al.

chlorophyll, algal bloom, article, cell count, cell density, coastal waters, controlled study, dinoflagellate, Lingulodinium polyedrum, meteorological phenomena, Mexico, near surface temperature stratification, nonhuman, nutrient concentration, popul CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA CIENCIAS DE LA TIERRA Y DEL ESPACIO OCEANOGRAFÍA OCEANOGRAFÍA

Assessing the Response of Nematode Communities to Climate Change-Driven Warming: A Microcosm Experiment

RUTH GINGOLD WERMUTH (2013, [Artículo])

Biodiversity has diminished over the past decades with climate change being among the main responsible factors. One consequence of climate change is the increase in sea surface temperature, which, together with long exposure periods in intertidal areas, may exceed the tolerance level of benthic organisms. Benthic communities may suffer structural changes due to the loss of species or functional groups, putting ecological services at risk. In sandy beaches, free-living marine nematodes usually are the most abundant and diverse group of intertidal meiofauna, playing an important role in the benthic food web. While apparently many functionally similar nematode species co-exist temporally and spatially, experimental results on selected bacterivore species suggest no functional overlap, but rather an idiosyncratic contribution to ecosystem functioning. However, we hypothesize that functional redundancy is more likely to observe when taking into account the entire diversity of natural assemblages. We conducted a microcosm experiment with two natural communities to assess their stress response to elevated temperature. The two communities differed in diversity (high [HD] vs. low [LD]) and environmental origin (harsh vs. moderate conditions). We assessed their stress resistance to the experimental treatment in terms of species and diversity changes, and their function in terms of abundance, biomass, and trophic diversity. According to the Insurance Hypothesis, we hypothesized that the HD community would cope better with the stressful treatment due to species functional overlap, whereas the LD community functioning would benefit from species better adapted to harsh conditions. Our results indicate no evidence of functional redundancy in the studied nematofaunal communities. The species loss was more prominent and size specific in the HD; large predators and omnivores were lost, which may have important consequences for the benthic food web. Yet, we found evidence for alternative diversity-ecosystem functioning relationships, such as the Rivets and the Idiosyncrasy Model. © 2013 Gingold et al.

aquaculture, article, bacterivore, benthos, biodiversity, biomass, climate, community dynamics, controlled study, ecosystem, environmental temperature, microcosm, nematode, nonhuman, population abundance, species diversity, species richness, taxonomy CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA CIENCIAS DE LA TIERRA Y DEL ESPACIO OCEANOGRAFÍA OCEANOGRAFÍA

Trophic ecology of Mexican Pacific harbor seal colonies using carbon and nitrogen stable isotopes

MARICELA JUAREZ RODRIGUEZ (2020, [Artículo])

There is limited information that provides a comprehensive understanding of the trophic ecology of Mexican Pacific harbor seal (Phoca vitulina richardii) colonies. While scat analysis has been used to determine the diet of some colonies, the integrative characterization of its feeding habits on broader temporal and spatial scales remains limited. We examined potential feeding grounds, trophic niche width, and overlap, and inferred the degree of dietary specialization using stable carbon and nitrogen isotope ratios (δ13C and δ15N) in this subspecies. We analyzed δ13C and δ15N on fur samples from pups collected at five sites along the western coast of the Baja California Peninsula, Mexico. Fur of natal coat of Pacific harbor seal pups begins to grow during the seventh month in utero until the last stage of gestation. Therefore pup fur is a good proxy for the mother's feeding habits in winter (∼December to March), based on the timing of gestation for the subspecies in this region. Our results indicated that the δ13C and δ15N values differed significantly among sampling sites, with the highest mean δ15N value occurring at the southernmost site, reflecting a well-characterized north to south latitudinal 15N-enrichment in the food web. The tendency identified in δ13C values, in which the northern colonies showed the most enriched values, suggests nearshore and benthic-demersal feeding habits. A low variance in δ13C and δ15N values for each colony (<1‰) and relatively small standard ellipse areas suggest a specialized foraging behavior in adult female Pacific harbor seals in Mexican waters. © 2020 Juárez-Rodríguez et al.

carbon, delta carbon 13, delta nitrogen 15, isotope, nitrogen, unclassified drug, carbon, nitrogen, Article, correlational study, feeding behavior, latitude, Mexico, nonhuman, organism colony, Pinnipedia, population abundance, species richness, troph BIOLOGÍA Y QUÍMICA CIENCIAS DE LA VIDA BIOLOGÍA ANIMAL (ZOOLOGÍA) BIOLOGÍA ANIMAL (ZOOLOGÍA)