Molecular evidence for the origin and evolutionary history of the rare American desert monotypic family Setchellanthaceae

Climate change and conservation in a warm North American desert: effect in shrubby plants

Background

Deserts are biologically rich habitats with a vast array of animals and plants adapted to xeric conditions, and most deserts are among the planet’s last remaining areas of total wilderness. Among North American deserts, the Chihuahuan Desert has the highest levels of diversity and endemism. To understand the effect of future climate change on plants distributed in this arid land and propose effective conservation planning, we focused on five endemic shrubby species that characterize the Chihuahuan Desert and used an integrative approach.

Methods

Ecological niche-based modeling, spatial genetics and ecological resistance analyses were carried out to identify the effect of global warming on the studied five shrubby species. Key areas that need to be preserved were identified taking into account the existing protected areas within the Chihuahuan Desert.

Results

The extent of future distribution will vary among these species, and on average expansion will occur in the western part of the Chihuahuan Desert. For most species low environmental resistance to gene flow was predicted, while higher future resistance was predicted for one species that would lead to increased population isolation. The highest haplotype diversity was identified in three hotspots. Based on future suitability of habitat and in the haplotype diversity we suggest preserving two hotspots of genetic diversity in the Sierra Madre Oriental, located in areas without protection. The third hotspot was detected in the well preserved Tehuacán-Cuicatlán Man and Biosphere Reserve.

Conclusion

Global climate change will have an effect in arid adapted plants, favoring expansion in the western of the Chihuahuan Desert however negatively affecting others with high ecological resistance disrupting gene flow. Two hotspots of genetic diversity in the Sierra Madre Oriental should be protected.

Pre-Holocene Origin for the Coronopus navasii Disjunction: Conservation Implications from Its Long Isolation

Integration of unexpected discoveries about charismatic species can disrupt their well-established recovery plans, particularly when this requires coordinate actions among the different governments responsible. The Critically Endangered Coronopus navasii (Brassicaceae) was considered a restricted endemism to a few Mediterranean temporary ponds in a high mountain range of Southeast Spain, until a new group of populations were discovered 500 km North in 2006. Ten years after this finding, its management has not been accommodated due to limited information of the new populations and administrative inertia. In this study, DNA sequences and species distribution models are used to analyse the origin of the C. navasii disjunction as a preliminary step to reassess its recovery plan. Molecular results placed the disjunction during Miocene-Pleistocene (6.30-0.49 Mya, plastid DNA; 1.45-0.03 Mya, ribosomal DNA), which discards a putative human-mediated origin. In fact, the haplotype network and the low gene flow estimated between disjunct areas suggest long-term isolation. Dispersal is the most likely explanation for the disjunction as interpreted from the highly fragmented distribution projected to the past. Particularly, a northward dispersal from Southeast is proposed since C. navasii haplotype network is connected to the sister-group through the southern haplotype. Although the reassessment of C. navasii conservation status is more optimistic under the new extent of occurrence, its long-term survival may be compromised due to the: (1) natural fragmentation and rarity of the species habitat, (2) genetic isolation between the two disjunct areas, and (3) northward shift of suitable areas under future climate change scenarios. Several ex-situ and in-situ conservation measures are proposed for integrating Central East Spanish populations into the on-going recovery plan, which still only contemplates Southeast populations and therefore does not preserve the genetic structure and diversity of the species.

Biogeography and diversification of Brassicales: A 103million year tale

Brassicales is a diverse order perhaps most famous because it houses Brassicaceae and, its premier member, Arabidopsis thaliana. This widely distributed and species-rich lineage has been overlooked as a promising system to investigate patterns of disjunct distributions and diversification rates. We analyzed plastid and mitochondrial sequence data from five gene regions (>8000bp) across 151 taxa to: (1) produce a chronogram for major lineages in Brassicales, including Brassicaceae and Arabidopsis, based on greater taxon sampling across the order and previously overlooked fossil evidence, (2) examine biogeographical ancestral range estimations and disjunct distributions in BioGeoBEARS, and (3) determine where shifts in species diversification occur using BAMM. The evolution and radiation of the Brassicales began 103Mya and was linked to a series of inter-continental vicariant, long-distance dispersal, and land bridge migration events. North America appears to be a significant area for early stem lineages in the order. Shifts to Australia then African are evident at nodes near the core Brassicales, which diverged 68.5Mya (HPD=75.6-62.0). This estimated age combined with fossil evidence, indicates that some New World clades embedded amongst Old World relatives (e.g., New World capparoids) are the result of different long distance dispersal events, whereas others may be best explained by land bridge migration (e.g., Forchhammeria). Based on these analyses, the Brassicaceae crown group diverged in Europe/Northern Africa in the Eocene, circa 43.4Mya (HPD=46.6-40.3) and Arabidopsis separated from close congeners circa 10.4Mya. These ages fall between divergent dates that were previously published, suggesting we are slowly converging on a robust age estimate for the family. Three significant shifts in species diversification are observed in the order: (1) 58Mya at the crown of Capparaceae, Cleomaceae and Brassicaceae, (2) 38Mya at the crown of Resedaceae+Stixis clade, and (3) 21Mya at the crown of the tribes Brassiceae and Sisymbrieae within Brassicaceae.

Phylogenetic relationships among the North American cleomoids (Cleomaceae): a test of Iltis's reduction series

PREMISE OF STUDY

A monophyletic group composed of five genera of the Cleomaceae represents an intriguing lineage with outstanding taxonomic and evolutionary questions. Generic boundaries are poorly defined, and historical hypotheses regarding the evolution of fruit type and phylogenetic relationships provide testable questions. This is the first detailed phylogenetic investigation of all 22 species in this group. We use this phylogenetic framework to assess generic monophyly and test Iltis's evolutionary "reduction series" hypothesis regarding phylogeny and fruit type/seed number. •

METHODS

Maximum likelihood and Bayesian analyses of four plastid intergenic spacer region sequences (rpl32-trnL, trnQ-rps16, ycf1-rps15, and psbA-trnH) and one nuclear (ITS) region were used to reconstruct phylogenetic relationships among the NA cleomoid species. Stochastic mapping and ancestral-state reconstruction were used to study the evolution of fruit type. •

KEY RESULTS

Both analyses recovered nearly identical phylogenies. Three of the currently recognized genera (Wislizenia, Carsonia, and Oxystylis) are monophyletic while two (Cleomella and Peritoma) are para- or polyphyletic. There was a single origin of the two-seeded schizocarp in the ancestor of the Oxystylis-Wislizenia clade and a secondary derivation of elongated capsule-type fruits in Peritoma from a truncated capsule state in Cleomella. •

CONCLUSIONS

Our well-resolved phylogeny supports most of the current species circumscriptions but not current generic circumscriptions. Additionally, our results are inconsistent with Iltis's hypothesis of species with elongated many-seed fruits giving rise to species with truncated few-seeded fruits. Instead, we find support for the reversion to elongated multiseeded fruits from a truncate few-seeded ancestor in Peritoma.