Inland dunes fauna and flora from Paleolake Irritila in the Comarca Lagunera, Coahuila, northern Mexico

Abstract

For over a decade the Chihuahuan Desert has been considered as a hotspot of biodiversity. The diverse aquatic ecosystems, especially, are (and were) rich in mollusk species. The dunes of the Comarca Lagunera, Coahuila, Mexico, are of major importance due to the well-preserved remains of animals and plants in a paleolake that covered a vast area in the region. This paper is the first report of the paleolimnological investigations of the Paleolake Irritila ecosystems in northern Mexico. We determined more than 28 species of gastropods, bivalves, ostracods, algae and one aquatic plant. The dunes contain one of the richest and most diverse fauna of the late Quaternary of northern Mexico. The fossils indicate a permanent but shallow lake with moderate salinity and alkalinity (pH) higher than 8.5, most likely around 10. Most of the mollusks are distributed outside Mexico and restricted to northern latitudes (northern United States and Canada). Several of them are endemic to the southern United States (Florida, Nevada, and Texas). For the first time in North America, using the local fauna and flora preserved in dune sediments, we try to reconstruct the paleoenvironmental conditions in northern Mexico during the late Quaternary.Keywords: Paleolake, inland dunes, Pleistocene mollusk fauna, northern Mexico. Resumen Desde hace más de una década el Desierto Chihuahuense está considerado como un hotspot de biodiversidad. Especialmente los diversos ecosistemas acuáticos contienen (y contenían) un alto número de especies de moluscos. Las dunas de la

Two new subfossil species of springsnails (Hydrobiidae: Pyrgulopsis) from North Mexico and their relation with extant species from Cuatrociénegas

“…from Late Quaternary Paleo-Lake Irritilian Coahuila do not belong to this genus but to the sister genus Cincinnatia Pilsbry, 1891. The only Late Holocene record of Pyrgulopsis, P. manantiali (Hershler), was recently described by Czaja et al (2014b). In sediments of two recently dried-up springs near the town of Viesca, Coahuila, specimens of two species of the genus Pyrgulopsis Call and Pilsbry, 1886 were collected.…”

Shifts in Climatic Niche Occupation in Astrophytum Coahuilense (H. Möller) Kayser and Its Potential Distribution in Mexico

“…This can be explained by the historic biogeography of A. coahuilense. It has already been documented that species is hydrochoric [5], and its principal method of dispersion was through extinct paleolithic lakes and rivers of the Pleistocene [52,53]. Likewise, it is possible to indicate that the occupation of new climatic niches by A. coahuilense occurs over thousands or millions of years.…”

HYDROCHORY IN Astrophytum coahuilense: EXPERIMENT TO IDENTIFY SEMINAL STRUCTURES THAT PROVIDE ITS BUOYANCY

“…Sánchez-Salas et al (2014) also found that 70% of A. capricorne seeds showed buoyancy for more than 30 days and that most of the seedlings that developed on the water during the evaluation, also floated. The probable adaptation for dispersion by water currents in A. coahuilense seeds could be considered to explain the geographical range of this plant, which in turn borders the margins of the great Irritila paleolake (Czaja et al, 2014). Taking into account that this area was covered by extensive paleolakes and paleorivers in the past (Van Devender, 1977;Van Devender y Burgess, 1985;Metcalfe, 2006, Marín y Torres-Ruata, 1990) that could have served as a mechanism of dispersion and probably as an agent for deposition of seeds on the limestone hills with rosette vegetation, characteristics where its main nurse Agave lecheguilla inhabits (Muro-Pérez et al, 2009).…”

“…Astrophytum coahuilense (considered a different species to A. myriostigma según Vazquez-Lobo et al 2015) is an endemic cactus species native to Mexico and it is currently in vulnerable (VU) category according to the IUCN (2011), mainly due to systematic extraction and habitat destruction in areas where it grows naturally. Various studies propose that the seed of this species is hydrochorous and that it is dispersed by means of water currents (Bregman 1988;Barthlott and Hunt 2000;Sánchez-Salas et al 2012, 2013, which has probably provided a wide range of dispersion to the species along the northern Mexican Chihuahuan desert, considering that in the past (Pleistocene-Holocene) there were abundant paleo-lakes and paleorivers in the north of Mexico (Van Devender y Burgess, 1977, 1985y Marín y Torres-Ruata, 1990;Metcalfe 2006;Czaja et al, 2014). However, there has not been any analysis carried out to show that the structure of the seed together with its density, as adaptations of its empty chambers and spongy tissue, confer buoyancy and to answer the question: why floats the seed of A. coahuilense?…”