Phylogenetic position and reinstatement of Gayella (Sapotaceae), a monotypic genus endemic to Chile with an Eocene origin in continental Australia

Abstract

AbstractPouteria splendens is the only native species of Sapotaceae in Chile, a species once placed in the monotypic genus Gayella and known as G. valparadisaea, but for a long time treated as a Pouteria. In a phylogenetic analysis, this species was placed in an Australasian clade, not with its presumed relatives in South America. We used Bayesian inference under a relaxed molecular clock in BEAST, nuclear ribosomal DNA (ETS, ITS), the nuclear gene RPB2, indel information, and 201 terminals to find the closest relative of P. splendens and to estimate the age of the disjunction between Australasia and South America. The taxon has an isolated phylogenetic position, being part of the cladeʼs backbone, and is placed with weak support as sister to Van‐royena, another monotypic genus, but endemic to Australia. Our results justify reinstatement of Gayella with its single species G. valparadisaea. Gayella has a unique combination of morphological features including alternate, opposite or 3‐whorled leaves, often on the same plant, a usually 6‐lobed, rotate corolla with revolute corolla lobes giving the flower a star‐like appearance, lacerate to dentate staminodes, and yellow‐orange‐red fruit with plano‐convex cotyledons and an exserted radicle below the cotyledon commissure. The split between Gayella and Van‐royena is estimated to the late Eocene at about 40.0 Ma (50.5–25.3 Ma). The hypothesis that the presence of Gayella in South America is a result of vicariance is consistent with the timing of the geological splits of southern Gondwana, as well as with evidence from fossil pollen, but long‐distance dispersal is an alternative explanation that cannot be excluded. Gayella is restricted to an area with a Mediterranean‐type climate in coastal central Chile, where it occurs in rocky places, ravines, and gullies, usually below 100 m altitude within reach of sea mist. Gayella valparadisaea is a rare plant, listed as Endangered (EN) in Chile, but it does not occur in any protected area. Considering the isolated phylogenetic position of this old lineage, we urge the Chilean authorities to increase the efforts towards protection of this species.