Diversification and biogeography of Juniperus (Cupressaceae): variable diversification rates and multiple intercontinental dispersals

Abstract

Summary• A central aim of biogeography is to understand when and how modern patterns of species diversity and distribution developed. Many plant groups have disjunct distributions within the Northern Hemisphere, but among these very few have been studied that prefer warm semi-arid habitats.• Here we examine the biogeography and diversification history of Juniperus, which occurs in semi-arid habitats through much of the Northern Hemisphere. A phylogeny was generated based on > 10 000 bp of cpDNA for 51 Juniperus species plus many outgroups. Phylogenies based on fewer species were also constructed based on nuclear internal transcribed spacer (nrITS) and combined nrITS ⁄ cpDNA data sets to check for congruence. Divergence time-scales and ancestral distributions were further inferred.• Both long dispersal and migration across land bridges probably contributed to the modern range of Juniperus, while long-term climatic changes and the uplift of the Qinghai-Tibetan plateau probably drove its diversification. Diversification apparently slowed down during climate-stable period of the Oligocene, and then speeded up from the Miocene onwards.• Juniperus probably originated in Eurasia, and was a part of the south Eurasian Tethyan vegetation of the Eocene to Oligocene. It reached America once at this time, once in the Miocene and once more recently.

Distribution of living Cupressaceae reflects the breakup of Pangea

“…Previous studies of gymnosperm radiations mostly have inferred Oligocene-age crown groups (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26), and a recent meta-analysis found a median crown age for gymnosperm genera of 32 Ma, younger than that found for angiosperm genera (25). Our dating of those genera with more than one species in the Cupressaceae similarly suggests relatively recent diversifications (Fig.…”

“…Relatively few Cupressaceae lineages have adapted to the strongly seasonal and semiarid habitats that became more widespread with the global cooling during the Oligocene/Miocene (30). Those that did, such as Juniperus, experienced a diversification burst during the Miocene (19).…”

“…19 and 64). For DNA extraction, PCR, and sequencing procedures, see Mao et al (19). The sequences produced were aligned using ClustalX version 1.83 (65), followed by manual adjustments in Mega4 (66).…”

Hemisphere-scale differences in conifer evolutionary dynamics

“…This phylogeny is based on a molecular dataset including two nuclear genes (18S and a phytochrome gene, PHYP) and two chloroplast genes (matK and rbcL). A maximum-likelihood (ML) tree topology, which agrees well with previously published phylogenetic studies of conifers (e.g., [12][13][14][15][16], was used as a constraint topology for inferring the dated phylogeny. Divergence times were estimated using a Bayesian implementation of an uncorrelated lognormal relaxed clock model with fossil calibration points used as minimum age constraints (Materials and Methods).…”

Anatomía comparada de la madera de Cupressaceae y su correspondencia con los estudios de filogenia

“…pisifera-Ch. formosensis (Li et al 2003;Wang et al 2003;Little et al 2004;Xiang y Li 2005;Mao et al 2010) más relacionado con Fokienia que el resto (Li et al 2003;Wang et al 2003;Xiang y Li 2005). También se han definido fuertes asociaciones entre Ch.…”