RESUMO
Within the southern California Current ecosystem there are two well-documented breaks in marine community structure at Point Conception and Punta Eugenia. We explored the presence of similar breaks in a diverse zooplankton community through metabarcoding of mixed net tow tissue samples collected during an expedition from Monterey to Baja California in February of 2012. We recovered a high diversity of species as well as patterns of species presence that align with their previously documented ranges in this region. We found a clear break at Punta Eugenia in overall zooplankton community structure, while Point Conception was weakly linked to changes in community structure. We analyzed this dataset through two parallel bioinformatic pipelines to examine the robustness of these results. Our overall conclusions were consistent across both pipelines, however there were differences in species detection. This study illustrates the utility of metabarcoding analysis on mixed tissue samples for recovering known patterns of diversity, as well as allowing elucidation of broad patterns of community differentiation across many groups of organisms.
Assuntos
Código de Barras de DNA Taxonômico , Ecossistema , Zooplâncton/classificação , Zooplâncton/fisiologia , Animais , México , Oceano PacíficoRESUMO
Poeciliopsis jackschultzi sp. nov., is described based on seven specimens (17.9-26.7 mm SL) from the Río Concepción (also known as Río Magdalena), Sonora, Mexico. The new species belongs to the Leptorhaphis species group and can be distinguished from other members of this group by features of the skeleton and colouration. The new species is sympatric with P. occidentalis, a hybridogenetic all-female biotype P. monacha-occidentalis, and hybrids between P. monacha-occidentalis females and P. jackschultzi males. The distribution of P. jackschultzi is highly restricted, and the main habitat, spring-fed marshy streams and pools, is susceptible to loss and degradation in a desert environment with increasing human water demand.
RESUMO
The discovery of four new Xenoturbella species from deep waters of the eastern Pacific Ocean is reported here. The genus and two nominal species were described from the west coast of Sweden, but their taxonomic placement remains unstable. Limited evidence placed Xenoturbella with molluscs, but the tissues can be contaminated with prey. They were then considered deuterostomes. Further taxon sampling and analysis have grouped Xenoturbella with acoelomorphs (=Xenacoelomorpha) as sister to all other Bilateria (=Nephrozoa), or placed Xenacoelomorpha inside Deuterostomia with Ambulacraria (Hemichordata + Echinodermata). Here we describe four new species of Xenoturbella and reassess those hypotheses. A large species (>20 cm long) was found at cold-water hydrocarbon seeps at 2,890 m depth in Monterey Canyon and at 1,722 m in the Gulf of California (Mexico). A second large species (~10 cm long) also occurred at 1,722 m in the Gulf of California. The third large species (~15 cm long) was found at ~3,700 m depth near a newly discovered carbonate-hosted hydrothermal vent in the Gulf of California. Finally, a small species (~2.5 cm long), found near a whale carcass at 631 m depth in Monterey Submarine Canyon (California), resembles the two nominal species from Sweden. Analysis of whole mitochondrial genomes places the three larger species as a sister clade to the smaller Atlantic and Pacific species. Phylogenomic analyses of transcriptomic sequences support placement of Xenacoelomorpha as sister to Nephrozoa or Protostomia.
Assuntos
Organismos Aquáticos/classificação , Filogenia , Animais , Organismos Aquáticos/genética , Oceano Atlântico , Teorema de Bayes , California , Feminino , Genes , Genoma Mitocondrial/genética , Fontes Hidrotermais , Funções Verossimilhança , Masculino , México , Modelos Biológicos , Oceano Pacífico , Especificidade da Espécie , Suécia , Transcriptoma/genéticaRESUMO
To assess the historical biogeography of freshwater topminnows in the genus Poeciliopsis, we examined sequence variation in two mitochondrial genes, cytochrome b (1140 bp) and NADH subunit 2 (1047 bp). This widespread fish genus is distributed from Arizona to western Colombia, and nearly half of its 21 named species have distributions that border on the geologically active Trans-Mexican Volcanic Belt (TMVB), a region that defines the uplifted plateau (Mesa Central) of Mexico. We used the parametric bootstrap method to test the hypothesis that a single vicariant event associated with the TMVB was responsible for divergence of taxa found to the north and south of this boundary. Because the single-event hypothesis was rejected as highly unlikely, we hypothesize that at least two geological events were responsible for divergence of these species. The first (8-16 million years ago) separated ancestral populations that were distributed across the present TMVB region. A second event (2.8-6.4 million years ago) was associated with northward dispersal and subsequent vicariance of two independent southern lineages across the TMVB. The geological history of this tectonically and volcanically active region is discussed and systematic implications for the genus are outlined.