First tardigrade records from San Pedro Mártir, Baja California, Mexico

A total of 66 specimens representing four tardigrade taxa were found in 14 moss and lichen samples collected from the bark of Jeffrey’s Pine, Pinus jeffreyi Balf., in the Sierra de San Pedro Mártir (Baja California, north-western Mexico). Two taxa were identified to the species level (Echiniscus becki Schuster & Grigarick, 1966 and E. blumi Richters, 1903), and two to the genus level (Milnesium sp. and Ramazzottius sp.). These are the first tardigrade records from the state of Baja California, and they increase the known tardigrade diversity of Mexico to 84 species.

Phylogenomics in the Hard Pines (Pinus subsection Ponderosae; Pinaceae) Confirms Paraphyly in Pinus ponderosa, and Places Pinus jeffreyi with the California Big Cone Pines

We sampled 130 individuals (2 to 25 per taxon) of Pinus subsections Ponderosae and Sabinianae. Nucleotide sequences were obtained by targeting 703 low copy nuclear genes. From the unenriched portion of the short reads, we assembled nearly complete plastome nucleotide sequences. We used 600 nuclear genes and the plastome sequences to create phylogenies and species trees that we compared to evaluate cytonuclear concordance and reticulation. We found that Pinus jeffreyi belongs with Pinus subsect. Sabinianae based on morphological synapomorphiesas well as strong molecular phylogenetic support. Pinus ponderosa sensu lato is paraphyletic, and we suggest treatment as three species: P. ponderosa sensu stricto (with P. ponderosa var. ponderosa, P. ponderosa var. benthamiana, and P. ponderosa var. washoensis), P. scopulorum, and P. brachyptera. The persistence of lineages with the footprints of ancient nuclear introgression (labeled bpw in clade N4) and chloroplast capture (labeledbpw in clade P1) should caution species identification in Pinus subsection Ponderosae based on limited molecular data. The hybrid frequency was low based on cytonuclear discordance, and the persistence of an ancient P1 plastid clade is a better explanation than hybridization betweenP. ponderosa and P. jeffreyi for unexpected plastid associations in the western Sierra Nevada, USA. We identified a new potential zone of ancient admixture between P. ponderosa and P. scopulorum in Idaho, USA. Some populations of P. arizonica, P. brachyptera, P. engelmannii, and P. scopulorum in the USA are more closely related to taxa with distributions limited to Mexico than they are to each other. To integrate phylogeny and taxonomy, future work should sample widely in Mexico and the USA, score morphological characters (including seedling characters from the known seed parent), on the same individual as used for molecular data, and use methods that are based on individuals rather than population frequencies.

Bending of Pinus jeffreyi in response to wind

<p><em>Aim of study:</em> To evaluate the degree of trunk sway in relation to wind velocity, with varying temporal integration and to compare this relation among seasons.</p><p><em>Area of study:</em> Sierra de Juárez, Baja California, México</p><p><em>Materials and Methods:</em> Displacements of a 19 m tall Jeffrey pine tree were recorded at 6 m from a three dimensional digital compass during one year, at c. 4 Hz. Adjacent wind speed at 6 m was recorded at 1 Hz.</p><p><em>Main results:</em> Sway was essentially unaffected by wind in the same second but increasing dependence of cumulative displacement on average sustained wind speed was found for intervals of 1 to 60 minutes (r² up to 0.89). The relation is generally log-linear but apparently differs in parameters between seasons.</p><p><em>Research highlights:</em> Wind-sway relations are clear from integration of several-to-many minutes. However, to estimate cumulative stress, sub-second data on sway are essential. Sub-second, precision measurements of sway can be registered from small, inexpensive sensors.</p><p><strong>Keywords:</strong><strong> </strong>biomechanics; <em>Pinus jeffreyi</em>; seasonality; stress accumulation; time series; tree bending.</p>