Phylogeny, biogeography, and evolutionary trends in the core Liliales and Calochortus (Calochortaceae): Insights from DNA sequenced data.

摘要

A detailed phylogenetic analysis of relationships within the core Liliales (including Dahlgren et al.'s [1985] Liliaceae, Calochortaceae, and part of Uvulariaceae) is presented, based on variation in rbcL and ndhF cpDNA sequences. The combined molecular phylogeny indicated that Calochortaceae and Liliaceae are not each other's closest relatives, and that Uvulariaceae within the core Liliales is not monophyletic. The results strongly imply that key morphological similarities between Liliaceae and Calochortaceae (conspicuous flowers, capsular fruits, bulbs, narrow leaves) developed via the process of concerted convergence, not common descent.;Studies on Calochortus as a whole used variation in noncoding cpDNA sequences to generate a phylogeny for 72 taxa, employing Tricyrds as an outgroup. Seven main clades were resolved, each exhibiting a strong degree of geographic cohesion. This pattern probably resulted from highly localized speciation in Calochortus, reflecting an interaction between poor seed dispersal capacity and distribution in a mountainous, dissected landscape. Serpentine tolerance arose a minimum of five times in Calochonrus, and was concentrated in two clades restricted to regions rich in serpentine outcrops. Parallel sets of floral syndromes evolved in the physiognomically similar regions occupied by different Calochortus clades: mariposas in dry grasslands and semi-deserts, star tulips in wet meadows, cat's-ears in montane woodlands, and fairy lanterns in closed forests. Poor dispersal capacity may have indirectly fostered these parallel adaptive radiations, by preventing species adapted to particular habitats from invading similar habitats in other regions, and forcing species in each geographically restricted clade to adapt to local conditions as they radiated into a variety of nearby habitats.;Analyses of Calochortus section Calochortus used variation in the internal transcribed spacer (M) of nuclear ribosomal DNA to reconstruct phylogenetic relationships. The US family tree confirmed findings based on cpDNA sequences, and indicated that serpentine tolerance evolved independently at least six times in the section. The cat's-ear floral syndrome (spreading petals, densely covered with trichomes on their inner surfaces) and montane woodland habitats are the basal conditions in section Calochortus, and the three other floral syndromes evolved as species in the section radiated into novel habitats.