Camila Martínez

Tracing the fossil pollen record of Hedyosmum (Chloranthaceae), an old lineage with recent Neotropical diversification

Abstract Chloranthaceae represent one of the oldest angiosperm lineages. Hedyosmum, with 45 species, is the only Neotropical genus in the family. The first appearance of Hedyosmum-like pollen was in the Early Cretaceous (∼112u2009Ma). The next unequivocal record of Hedyosmum-like pollen (Clavainaperturites microclavatus) occurred in the early Miocene. The main objective of this study was to determine the relationship between the fossil C. microclavatus and extant representatives of Hedyosmum. Pollen was examined using light, scanning and transmission electron microscopy. Based on a phylogenetic analysis of pollen traits of Chloranthaceae, we concluded that C. microclavatus is related to Hedyosmum. The abundant Neogene fossil evidence of C. microclavatus from South America showed that the ancestor of extant Hedyosmum migrated to tropical South America during the early Miocene and occupied initially lowlands. A comparison of the C. microclavatus fossil record from both Panama and Colombia/Venezuela suggests that the first Neotropical migration of Hedyosmum was from South America to Central America. The abundant Plio-Pleistocene C. microclavatus from Andean regions supports the hypothesis of a recent radiation of the genus as a consequence of the uplift of the tropical Andes. The biogeographic history of Hedyosmum provides an example of recent enrichment of the Neotropical flora.

A Late Cretaceous Piper (Piperaceae) from Colombia and diversification patterns for the genus

PREMISE OF THE STUDYnDocumented fossil floras in the neotropics are sparse, yet their records provide evidence on the spatial and temporal occurrence of taxa, allowing for testing of biogeographical and diversification scenarios on individual lineages. A new fossil Piper from the Late Cretaceous of Colombia is described here, and its importance for assessing diversification patterns in the genus is addressed.nnnMETHODSnLeaf architecture of 32 fossil leaf compressions from the Guaduas Formation was compared with that of 294 extant angiosperm species. The phylogenetic position of the fossil named Piper margaritae sp. nov. was established based on leaf traits and a molecular scaffold of Piper. The age of the fossil was independently used as a calibration point for divergence time estimations.nnnKEY RESULTSnNatural affinities of P. margaritae to the Schilleria clade of Piper indicate that the genus occurred in tropical America by the Late Cretaceous. Estimates of age divergence and lineage accumulation reveal that most of the extant diversity of the genus accrued during the last ∼30 Myr.nnnCONCLUSIONSnThe recent radiation of Piper is coeval with both the Andean uplift and the emergence of Central America, which have been proposed as important drivers of diversity. This pattern could exemplify a recurrent theme among many neotropical plant lineages.

Cretaceous asterid evolution: fruits of Eydeia jerseyensis sp. nov. (Cornales) from the upper Turonian of eastern North America

BACKGROUND AND AIMSnThe asterids (>80 000 extant species) appear in the fossil record with considerable diversity near the Turonian-Coniacian boundary (~90 Ma; Late Cretaceous) and are strongly represented in the earliest diverging lineage, Cornales. These early asterid representatives have so far been reported from western North America and eastern Asia. In this study, we characterize a new cornalean taxon based on charcoalified fruits from the upper Turonian of eastern North America, a separate landmass from western North America at the time, and identify early palaeobiogeographical patterns of Cornales during the Cretaceous.nnnMETHODSnFossils were studied and imaged using scanning electron microscopy and micro-computed tomography (micro-CT) scanning. To assess the systematic affinities of the fossils, phylogenetic analyses were conducted using maximum parsimony.nnnKEY RESULTSnThe charcoalified fruits are represented by tri-locular woody endocarps with dorsal apically opening germination valves. Three septa intersect to form a robust central axis. Endocarp ground tissue consists of two zones: an outer endocarp composed of isodiametric sclereids and an inner endocarp containing circum-locular fibres. Central vasculature is absent; however, there are several small vascular bundles scattered within the septa. Phylogenetic analysis places the new taxon within the extinct genus Eydeia.nnnDISCUSSIONnThick-walled endocarps with apically opening germination valves, no central vascular bundle and one seed per locule are indicative of the order Cornales. Comparative analysis suggests that the fossils represent a new species, Eydeia jerseyensis sp. nov. This new taxon is the first evidence of Cornales in eastern North America during the Cretaceous and provides insights into the palaeobiogeography and initial diversification of the order.

Passifloraceae seeds from the late Eocene of Colombia

PREMISE OF THE STUDYnThe plant fossil record for the neotropics is still sparse and temporally discontinuous. The location and description of new fossil material are fundamental for understanding evolutionary and biogeographic patterns of lineages. A new fossil record of Passifloraceae from the late Eocene of Colombia is described in this study.nnnMETHODSnPlant fossils were collected from a new locality from the Eocene Esmeraldas Formation. Eighteen fossil seeds were selected, described, and compared with fossil and extant angiosperm seeds based on the literature and herbarium collections. Taxonomic affinities of the fossil seeds within Passifloraceae s.l. were evaluated by comparing morphological characters of the seeds in a phylogenetic context. Stratigraphic information associated with the fossil locality was used to interpret the environment and taphonomic processes associated with fossil deposition.nnnKEY RESULTSnA new seed fossil genus and species, Passifloroidesperma sogamosense gen. and sp. nov., is described and associated with the subfamily Passifloroideae based on the presence of a foveolate seed surface, ruminate endosperm, and a seed coat with prismatic palisade cells. The depositional environment of the locality is described as a floodplain associated with river channels.nnnCONCLUSIONSnA detailed review of the Passifloraceae fossil record indicates that P. sogamosense is the oldest confirmed record of Passifloraceae. Its late Eocene age provides a minimum age that can be used as a calibration point for the crown Passifloroideae node in future dating analyses that together with its neotropical geographic location can shed light on the origin and diversification of the subfamily.