Thirteen new weeds on Cedros Island, Baja California, Mexico

Background and Aims: Cedros Island is the southernmost outpost of the California Floristic Province, the largest island in the Californian archipelago, and home to a suite of endemic plants and animals. As such, it is an important resource within the Pacific Islands Biosphere Reserve, with many management concerns. The goal of this study was to document newly arrived plant species on Cedros Island, Baja California, Mexico.Methods: From the 8th to the 11th February 2019 we visited Cedros Island and made observations of plants around Cedros Village using the platform NaturaLista (iNaturalist).Key results: Thirteen new plant taxa were detected around Cedros village, all were non-native. These discoveries follow a very recently published checklist on the flora and suggest that new non-native plants are arriving rapidly. Conclusions: Recommended management implications include monitoring and eradication of new species, particularly at inhabited areas, and with priority given to highly invasive species such as Cenchrus setaceus and C. ciliaris.

Phylogeography of Cedros and Tiburón Island Mule Deer in North America’s Desert Southwest

Though mule deer (Odocoileus hemionus) persist in robust populations throughout most of their North American distribution, habitat loss, unregulated hunting, and other factors have reduced their historical range in México. Two of the 6 putative subspecies inhabiting México’s deserts and Baja California peninsula are of conservation concern, occupying islands in the Pacific Ocean (Odocoileus hemionus cerrosensis on Cedros Island: endangered) and Sea of Cortés (Odocoileus hemionus sheldoni on Tiburón Island: threatened). Focusing on the desert southwest (n = 448), we sampled Tiburón (n = 22) and Cedros (n = 15) Island mule deer using contemporary samples and natural history museum specimens to complete a phylogeographic evaluation of the species complex, and assess the phylogeography of these insular subspecies. Both insular subspecies formed endemic haplotype lineages, consistent with island biogeographic theory. Bayesian skyline plots were consistent with Holocene demographic expansion. Cedros Island deer were genetically most similar to adjacent mainland Baja California deer, but exhibited a suite of unique haplotypes and reduced genetic variation. Tiburón Island deer haplotypes unexpectedly nested within a mainland lineage found in distant New Mexico, rather than the adjacent mainland Sonoran lineage. Such findings suggest the importance of postglacial climate fluctuations and biotic community turnover in the phylogeographic history of mule deer in the desert southwest. Our genetic data corroborates cultural, archaeological, and phenotypic evidence supporting Cedros and Tiburón deer endemicity and subspecies status. Reduced genetic variation, divergence from mainland populations, and demographic trends on both islands indicate that conservation, monitoring, and management are critical to ensure persistence of these endemic insular subspecies.

The Columbellid species of the northeast Pacific coast from the Aleutian Islands to Cedros Island, Baja California (Neogastropoda: Columbellidae)

The neogastropod family Columbellidae is a diverse cosmopolitan group of small marine snails, with its greatest diversity in the tropics. They are represented in high latitudes, but the columbellid fauna of higher latitudes tends to be much less well documented. The present paper documents the nearshore columbellid fauna of the northeastern Pacific Ocean, from the Aleutian Islands to Cedros Island, near the dividing point between Baja California and Baja California Sur. It is based on work by J.H. McLean, and completed posthumously. Examination of the regional columbellid collections in the Natural History Museum of Los Angeles County and the Santa Barbara Museum of Natural History has resulted in 24 species in eight genera, of which four new species and one new genus are described herein. The present paper focuses on dry shell material.

Baja California, Domain 1

Ophiolites occur in Baja California along the outer coast from San Benito and Cedros Islands through the Vizcaíno Peninsula to Magdalena and Santa Margarita Islands. This is a mountainous region with altitudes up to 920 m (3018 ft) on the Vizcaíno Peninsula, >300 m (∼1000 ft.) on Magdalena Island, and about 550 m (∼1800 ft) on Santa Margarita Island. The ophiolite of Calmalli, which is geologically distinct from ophiolites on the outer coast, is in low hills (mostly <500 m, or 1640 ft) near El Arco, about midway from Guerrero Negro to the Gulf of California. Ophiolites of the outer coast are in the Cochimí terrane, whereas the ophiolite of Calmalli is in the Alisitos terrane (Sedlock et al. 1993, Sedlock 2003). Mafic rocks of the Peninsular Ranges batholith that extends from California into Baja California are included in this domain. A major feature of the Peninsular Ranges is this batholith with plutons that range in composition from granite to gabbro, with tonalite the most common composition. Also, gabbro is common in the “western zone” of the batholith (Sedlock 2003). This zone is mostly southwest of the Elsinore fault zone in the California and north of the Agua Blanca fault in Baja California. All the ophiolites are in desert areas. Mean annual temperatures are about 20°C, and mean annual precipitation is about 10 cm on Cedros Island and along the outer coast of Baja California Sur and about 15 cm in the ophiolite of Calmalli locality (Hastings and Turner 1965). The precipitation falls mostly in winter in the Cedros Island and Puerto Nuevo localities, in September in the Magdalena–Margarita locality, and in both September and in winter in the Calmalli locality. Fog and dew are common along the outer coast around Santa Margarita and Magdalena Islands. Drought persists for most of each year at all the localities (Hastings and Humphrey 1969; fig 13-3). The gabbro belt in the northern part of the Peninsular Ranges has been added to this domain. Descriptions of the geology, climate, soils, and vegetation of the gabbroic plutons are given in section 13.8, describing the Los Pinos locality.

Holocene Marine Reservoir Time Series ΔR Values from Cedros Island, Baja California

ΔR values have been calculated based on offsets in radiocarbon values exhibited in a series of stratigraphically paired charcoal and marine shell values, ranging from about 300 to 10,000 BP, excavated from archaeological sites on Cedros Island, Baja California, Mexico. Based on this data, there appears to be the equivalent of about an 800-yr range in inferred ΔR values (-400 to 400 yr) exhibited in Holocene-age marine shells from this portion of the central Baja California coast.