Brahea

Abstract: This publication is an account of the palms (Arecaceae) in the state of Sonora in northwestern Mexico. Six native palm species in three genera are recorded for Sonora: Brahea with four species, and Sabat and Washingtonia each with one species. Relationships and taxonomy within Brahea, especially B. elegans, remain unresolved. Brief botanical descriptions, taxonomic synopses, local names, identification keys, conservation status and recommendations, and distributional and ethnobotanical information are provided for each species. Basionyms and types are cited. Distributions are documented with citations of nearly all herbarium specimens known to us from Sonora. Many palm populations in this arid and semiarid region are threatened by development and in some cases overexploitation. There is an urgent need for formal management and conservation action for local populations, although as a whole none of these species in Sonora are rare or immediately threatened.

Abstract: The complex geological and ecological processes that have generated high levels of biodiversity and endemism in the Baja California Peninsula have been the subject of intensive study However, relatively little is known about phylogeography of the iconic endemic palm species of this region We therefore analyzed a total of 2,294 bp of chloroplast and 738 bp of nuclear sequence data in 169 samples of five native palm species from Baja California, Sonora and Guadalupe Island We found that Washingtonia and Brahea palms had low levels of genetic diversity and were highly structured, with the majority of species and major geographic regions being characterized by distinct haplotypes We also found strong support for currently recognized species in Washingtonia, but our results were less clear cut for Brahea due to haplotype sharing Furthermore, patterns of population structure were broadly consistent with historical vicariant events such as the inundation of the Isthmus of La Paz, the formation of the Sea of Cortez, and the more recent colonization and isolation of Guadalupe Island's palms Our findings contribute toward a growing appreciation of the complexity of plant responses to past geological changes and also provide valuable baseline genetic data on relict American palm species

Abstract: Comparative studies can provide powerful insights into processes that affect population divergence and thereby help to elucidate the mechanisms by which contemporary populations may respond to environmental change. Furthermore, approaches such as genotyping by sequencing (GBS) provide unprecedented power for resolving genetic differences among species and populations. We therefore used GBS to provide a genomewide perspective on the comparative population structure of two palm genera, Washingtonia and Brahea, on the Baja California peninsula, a region of high landscape and ecological complexity. First, we used phylogenetic analysis to address taxonomic uncertainties among five currently recognized species. We resolved three main clades, the first corresponding to W. robusta and W. filifera, the second to B. brandegeei and B. armata, and the third to B. edulis from Guadalupe Island. Focusing on the first two clades, we then delved deeper by investigating the underlying population structure. Striking differences were found, with GBS uncovering four distinct Washingtonia populations and identifying a suite of loci associated with temperature, consistent with ecologically mediated divergence. By contrast, individual mountain ranges could be resolved in Brahea and few loci were associated with environmental variables, implying a more prominent role of neutral divergence. Finally, evidence was found for long‐distance dispersal events in Washingtonia but not Brahea, in line with knowledge of the dispersal mechanisms of these palms including the possibility of human‐mediated dispersal. Overall, our study demonstrates the power of GBS together with a comparative approach to elucidate markedly different patterns of genomewide divergence mediated by multiple effectors.