Botany Fossil species of Boehmerieae Gaudich. (Urticaceae) in Dominican and Mexican amber: A new genus (Ekrixanthera) and two new species with anemophilous pollination by explosive pollen release, and possible lepidopteran herbivory Journal: Botany Manuscript ID cjb-2016-0006.R2 Manuscript Type: Article Date Submitted by the Author: 04-May-2016Draft Complete List of Authors: Poinar, Jr., George; Oregon State University, Department of Integrative Biology Kevan, Peter; Environmental Biology Jackes, Betsy; James Cook University palaeobotany, anemophily, Ekrixanthera hispaniolae, Ekrixanthera ehecatli, Keyword: paleoecology https://mc06.manuscriptcentral.com/botany-pubs Page 1 of 31 Botany Fossil species in Boehmerieae Gaudich. (Urticaceae) in Dominican and Mexican amber: A new genus ( Ekrixanthera ) and two new species with anemophilous pollination by explosive pollen release, and possible lepidopteran herbivory GEORGE POINAR, JR. 1 PETER G. KEVAN 2 AND BETSY R. JACKES 3 1Department of Integrative Biology, Oregon State University, Corvallis, Oregon, 97331 USA 2School of Environmental Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada 3College of Marine and Environmental DraftSciences, James Cook University, Townsville, QLD 4811, Australia Corresponding Author: Peter G. Kevan [email protected] Received; revised; accepted for publication Running title: Fossil species of Boehmerieae (Ekrixanthera gen. nov.) https://mc06.manuscriptcentral.com/botany-pubs Botany Page 2 of 31 ABSTRACT The first fossil flowers of Neotropical Urticaceae (Boehmerieae) are described from the Dominican Republic and Mexico as belonging to a new genus, Ekrixanthera . Ekrixanthera hispaniolae sp. nov. from Dominican amber has pentamerous staminate flowers on short pedicels with a pilose pistillode and heteromorphic pilose tepals, two are clavate and three linear. Ekrixanthera ehecatli sp. nov. has pentamerous staminate flowers lacking pedicels, a pistillode with greatly reduced pilosity, glabrous and heteromorphic tepals with two linear and three wedge-shaped with truncate tips. The presence or absence of a pedicel, heterotrophic condition of the tepals and presence or absence of pilosity of the pistillode and tepals separate the two species. Those characters, together with the pentamerous flowers separate both fossil species from extant genera. The floral Draftstructures indicate explosive pollen release and pollination by wind (anemophily). Pistillate flowers have not been found for this usually dioecious tribe. Lepidopteran herbivory is suggested by a damaged stipule in one specimen and a nymphalid butterfly ( Vanessa -like) caterpillar that may have used Ekrixanthera as a food plant is illustrated. The fossils establish an early lineage of Boehmerieae with characteristic explosive pollen release and perhaps associated herbivorous insects in the West Indies and North America during the mid-Tertiary. Keywords: palaeobotany, paleoecology, anemophily, Ekrixanthera hispaniolae , Ekrixanthera ehacatli https://mc06.manuscriptcentral.com/botany-pubs Page 3 of 31 Botany INTRODUCTION Amber is a wonderful medium for preserving delicate structures like flowers and has provided evidence of various plant lineages dating back to the Early-mid Cretaceous. New World ambers from the Dominican Republic and Mexico have provided rare glimpses into the flora that existed in the West Indies during the mid-Tertiary. Genera from the following families of angiosperms have been described from this New World amber: Poaceae (Poinar and Judziewicz 2005; Poinar and Columbus 2012), Arecaceae (Poinar 2002a; 2002b), Chrysobalanaceae (Poinar et al. 2008a; corrected by Chambers and Poinar 2010), Lauraceae (Chambers et al. 2011a; 2012), Meliaceae (Chambers et al. 2011b; Chambers and Poinar 2012), Burseraceae (Chambers and Poinar 2013), Myristicaceae (Poinar and Steeves 2013), Rhamnaceae (Chambers and Poinar 2014a), Ticodendraceae (Chambers and Poinar Draft2014b), Fabaceae (Poinar 1991; Poinar and Brown 2002) and possibly Moraceae (Poinar et al. 2008b). The Dominican amber forest was characterized by Poinar and Poinar (1999) based on both animal and plant fossils. The Urticaceae is a large family with over 45 genera and some 2000 species (Friis 1989; Wu et al. 2015). The family has a poor fossil record of flowers, with only one definite flower (Forskohleanthium nudum Conwentz) having been described in Baltic amber (Conwentz 1886). The present work describes two congeneric species that share characters with other Boehmerieae, such as Boehmeria, but have characters that prevent assignment to an extant genus. One species is described from Dominican and the other from Mexican amber. They represent the first fossil flowers of Neotropical Urticaceae. https://mc06.manuscriptcentral.com/botany-pubs Botany Page 4 of 31 MATERIAL AND METHODS PROVENANCES The Dominican amber fossils originated from amber mines in the northern mountain range (Cordillera Septentrional) of the Dominican Republic between Puerto Plata and Santiago. Amber from mines in this region was produced by Hymenaea protera Poinar (1991) (Fabaceae). Dating of Dominican amber is still controversial, with the youngest proposed age of 20-15 mya based on Foraminifera (Iturralde-Vincent and MacPhee 1996) and the oldest of 45-30 mya based on coccoliths (Cepek in Schlee 1990). These are considered minimum dates as they are based on microfossils in the strata containing the amber. Most of the amber was secondarily deposited in turbiditic sandstones of the Upper EoceneDraft to Lower Miocene Mamey Group (Draper et al. 1994). Dilcher et al. (1992) stated that “...the amber clasts, from all physical characteristics, were already matured amber at the time of re-deposition into marine basins. Therefore, the age of the amber is greater than Miocene and quite likely is as early as late Eocene”. The issue is further complicated by the discovery of Early Oligocene amber in Puerto Rico and Maastrichtian- Paleocene amber in Jamaica (Iturralde-Vinent 2001) showing that amber from a range of deposits occurs in the Greater Antilles. The Mexican amber fossils originated from amber mines in the northern mountain ranges or Chiapas Highlands of the Simojovel area in Chiapas, Mexico. Amber from Chiapas, which was produced by Hymenaea mexicana (Fabaceae) (Poinar and Brown 2002), occurs in lignitic beds among sequences of primarily marine calcareous sandstones and silt. The amber is associated with Balumtun Sandstone of Early Miocene and the La Quinta Formation of the Late Oligocene with radiometric ages from 22.5 to 26 million years (Berggren and Van Couvering 1974). Because the amber was secondarily deposited in these marine formations, it may be https://mc06.manuscriptcentral.com/botany-pubs Page 5 of 31 Botany somewhat older than the above dates. METHODS Observations and photographs were made with a Nikon SMZ-10 R stereoscopic microscope and Nikon Optiphot compound microscope with magnifications up to 600 X. Helicon Focus Pro X64 was used to stack photos for better clarity and depth of field. RESULTS Three separate pieces of Dominican amber contain fossil representatives ascribed to the tribe Boehmerieae but not to an extant genus. Dominican amber piece Sd-9-95ADraft contains a single staminate flower (Figs. 1-3). Dominican amber piece Sd-9-95B contains two staminate flowers, one with the tepals and stamens beginning to unroll and another with the tepals and stamens outstretched (Fig. 4). The same piece of amber also contains a developing fruit but not on the same structure (Fig. 5) and an insect-damaged stipule (Fig. 6) with evidence of putative cystoliths (Fig. 7). Two conjoined staminate flowers with short pedicels in lateral view (specimen Sd-9-95C) provide indication of the structure of the inflorescence (Fig. 8). The Mexican amber piece (Sd-9-96) contains two staminate flowers, one of which is completely opened (Figs. 9, 10) and another that has the stamens bent back, one of which was releasing pollen (Fig. 11). We found no evidence of female reproductive structures. TAXONOMIC PLACEMENT AND DESCRIPTIONS The specimens we describe (below) belong to species in the tribe Boehmerieae, a large tribe which, as presently considered, comprises about 20 genera with limits that often are not https://mc06.manuscriptcentral.com/botany-pubs Botany Page 6 of 31 satisfactory. The presence of the pistillode in the staminate flowers of both species we describe indicates that neither can be placed in the tribe Urticeae. With the characters that are preserved in the fossils we describe, we note five similar extant genera in Boehmerieae. We rule out assignment to Nothocnide, Cypholophus and Oreocnide on the basis of stipule forms. Species in the genera Pouzolzia and Boehmeria share greater similarities with the fossils we describe with pentamerous male flowers. In Pouzolzia they are usually vaulted at the apex, at least in Javanese species (Backer and Bakhuizen van den Brink 1965). Staminate flowers of extant species of Boehmeria are regular (actinomorphic) and most are reported to be tetramerous (Friis 1989), which would separate them from those of the fossils we describe. A persistent filamentous style on the developing fruit is expected for Boehmeria but not necessarily for Pouzolzia (Wilmot- Dear et al. 2009). Even so, the two generaDraft are difficult to distinguish morphologically (Wilmot- Dear et al. 2009). On the basis of morphological and molecular data, members of Boehmeria and Pouzolzia have been assigned to three or two subclades respectively,